WorldWideScience

Sample records for atomic force microscopy

  1. Noncontact atomic force microscopy v.3

    CERN Document Server

    Morita, Seizo; Meyer, Ernst

    2015-01-01

    This book presents the latest developments in noncontact atomic force microscopy. It deals with the following outstanding functions and applications that have been obtained with atomic resolution after the publication of volume 2: (1) Pauli repulsive force imaging of molecular structure, (2) Applications of force spectroscopy and force mapping with atomic resolution, (3) Applications of tuning forks, (4) Applications of atomic/molecular manipulation, (5) Applications of magnetic exchange force microscopy, (6) Applications of atomic and molecular imaging in liquids, (7) Applications of combine

  2. Coffee Cup Atomic Force Microscopy

    Science.gov (United States)

    Ashkenaz, David E.; Hall, W. Paige; Haynes, Christy L.; Hicks, Erin M.; McFarland, Adam D.; Sherry, Leif J.; Stuart, Douglas A.; Wheeler, Korin E.; Yonzon, Chanda R.; Zhao, Jing; Godwin, Hilary A.; Van Duyne, Richard P.

    2010-01-01

    In this activity, students use a model created from a coffee cup or cardstock cutout to explore the working principle of an atomic force microscope (AFM). Students manipulate a model of an AFM, using it to examine various objects to retrieve topographic data and then graph and interpret results. The students observe that movement of the AFM…

  3. Atomic Force Microscopy in Liquids

    Science.gov (United States)

    Weisenhorn, Albrecht Ludwig

    The atomic force microscope (AFM) was invented by Binnig, Quate, and Gerber in 1986 as an offspring of the very successful scanning tunneling microscope (STM), which Binnig and Rohrer invented in 1982 and for which they shared the Nobel prize. While the STM can only image conducting surfaces, the AFM has overcome this limitation. An AFM creates a three-dimensional image of the sample surface by raster scanning this surface under a sharp tip that is attached to a cantilever. The tip moves the cantilever up and down while going over "hills" and through "valleys" of the surface. The vertical motion of the cantilever deflects a laser beam that is reflected off the back of the cantilever toward a two-segment photodiode. The difference of the intensity of the two segments is used as the deflection signal. A feedback loop is used to keep the deflection signal constant by moving the sample surface up and down accordingly. This vertical motion gives a direct measurement of the surface height. The forces involved in the imaging process have been studied in air and water. Due to adsorbed layers on tip and sample surface when scanning in air (capillary condensation) the imaging forces are >10 ^{-7} N. If the tip and sample surface are immersed in water the forces can be reduced to {~}10^{ -9} N. An AFM with a large scanner can image up to tens of micrometers like an optical microscope. Zooming in allows one to get resolution of a few nanometers, which makes the AFM a natural continuation of the optical microscope towards higher magnification. Integrated circuit chips, photographic film, bacteria, red and white blood cells, purple membrane, polymerized Langmuir-Blodgett (LB) films, and stoma have been imaged at low and high magnification. The AFM has shown its power by imaging "hard" and "soft" surfaces with atomic and (sub)molecular resolution respectively. The "hard" crystalline surfaces of mica, graphite, RuCl_3, Ge(111), Bi(111), and zeolites (clinoptilolite (010

  4. Calcite biomineralization in coccoliths: Evidence from atomic force microscopy (AFM)

    DEFF Research Database (Denmark)

    Henriksen, Karen; Stipp, S.L.S.

    2002-01-01

    geochemistry, crystal orientation, coccolith function, biomineralization, biological calcite, atomic force microscopy......geochemistry, crystal orientation, coccolith function, biomineralization, biological calcite, atomic force microscopy...

  5. Atomic force microscopy in cell biology

    Institute of Scientific and Technical Information of China (English)

    LU Zhexue; ZHANG Zhiling; PANG Daiwen

    2005-01-01

    The history, characteristic, operation modes and coupling techniques of atomic force microscopy (AFM) are introduced. Then the application in cell biology is reviewed in four aspects: cell immobilization methods, cell imaging, force spectrum study and cell manipulation. And the prospect of AFM application in cell biology is discussed.

  6. Imaging DNA Structure by Atomic Force Microscopy.

    Science.gov (United States)

    Pyne, Alice L B; Hoogenboom, Bart W

    2016-01-01

    Atomic force microscopy (AFM) is a microscopy technique that uses a sharp probe to trace a sample surface at nanometre resolution. For biological applications, one of its key advantages is its ability to visualize substructure of single molecules and molecular complexes in an aqueous environment. Here, we describe the application of AFM to determine superstructure and secondary structure of surface-bound DNA. The method is also readily applicable to probe DNA-DNA interactions and DNA-protein complexes.

  7. Spectroscopy and atomic force microscopy of biomass.

    Science.gov (United States)

    Tetard, L; Passian, A; Farahi, R H; Kalluri, U C; Davison, B H; Thundat, T

    2010-05-01

    Scanning probe microscopy has emerged as a powerful approach to a broader understanding of the molecular architecture of cell walls, which may shed light on the challenge of efficient cellulosic ethanol production. We have obtained preliminary images of both Populus and switchgrass samples using atomic force microscopy (AFM). The results show distinctive features that are shared by switchgrass and Populus. These features may be attributable to the lignocellulosic cell wall composition, as the collected images exhibit the characteristic macromolecular globule structures attributable to the lignocellulosic systems. Using both AFM and a single case of mode synthesizing atomic force microscopy (MSAFM) to characterize Populus, we obtained images that clearly show the cell wall structure. The results are of importance in providing a better understanding of the characteristic features of both mature cells as well as developing plant cells. In addition, we present spectroscopic investigation of the same samples.

  8. Can Atomic Force Microscopy Achieve Atomic Resolution in Contact Mode?

    Science.gov (United States)

    Jarvis, M. R.; Pérez, Rubén; Payne, M. C.

    2001-02-01

    Atomic force microscopy operating in the contact mode is studied using total-energy pseudopotential calculations. It is shown that, in the case of a diamond tip and a diamond surface, it is possible for a tip terminated by a single atom to sustain forces in excess of 30 nN. It is also shown that imaging at atomic resolution may be limited by blunting of the tip during lateral scanning.

  9. Recognizing nitrogen dopant atoms in graphene using atomic force microscopy

    DEFF Research Database (Denmark)

    van der Heijden, Nadine J.; Smith, Daniel; Calogero, Gaetano

    2016-01-01

    Doping graphene by heteroatoms such as nitrogen presents an attractive route to control the position of the Fermi level in the material. We prepared N-doped graphene on Cu(111) and Ir(111) surfaces via chemical vapor deposition of two different molecules. Using scanning tunneling microscopy images...... as a benchmark, we show that the position of the dopant atoms can be determined using atomic force microscopy. Specifically, the frequency shift-distance curves Delta f(z) acquired above a N atom are significantly different from the curves measured over a C atom. Similar behavior was found for N-doped graphene...

  10. Atomic force microscopy of biological samples

    Energy Technology Data Exchange (ETDEWEB)

    Doktycz, Mitchel John [ORNL

    2010-01-01

    The ability to evaluate structural-functional relationships in real time has allowed scanning probe microscopy (SPM) to assume a prominent role in post genomic biological research. In this mini-review, we highlight the development of imaging and ancillary techniques that have allowed SPM to permeate many key areas of contemporary research. We begin by examining the invention of the scanning tunneling microscope (STM) by Binnig and Rohrer in 1982 and discuss how it served to team biologists with physicists to integrate high-resolution microscopy into biological science. We point to the problems of imaging nonconductive biological samples with the STM and relate how this led to the evolution of the atomic force microscope (AFM) developed by Binnig, Quate, and Gerber, in 1986. Commercialization in the late 1980s established SPM as a powerful research tool in the biological research community. Contact mode AFM imaging was soon complemented by the development of non-contact imaging modes. These non-contact modes eventually became the primary focus for further new applications including the development of fast scanning methods. The extreme sensitivity of the AFM cantilever was recognized and has been developed into applications for measuring forces required for indenting biological surfaces and breaking bonds between biomolecules. Further functional augmentation to the cantilever tip allowed development of new and emerging techniques including scanning ion-conductance microscopy (SICM), scanning electrochemical microscope (SECM), Kelvin force microscopy (KFM) and scanning near field ultrasonic holography (SNFUH).

  11. High-resolution noncontact atomic force microscopy.

    Science.gov (United States)

    Pérez, Rubén; García, Ricardo; Schwarz, Udo

    2009-07-01

    Progress in nanoscience and nanotechnology requires tools that enable the imaging and manipulation of matter at the atomic and molecular scale. During the last two decades or so, scanning probe-based techniques have proven to be particularly versatile in this regard. Among the various probe-based approaches, atomic force microscopy (AFM) stands out in many ways, including the total number of citations and the breadth of possible applications, ranging from materials characterization to nanofabrication and biological studies. However, while nanometer scale operation in different environments became routine, atomic resolution imaging remained elusive for a long time. The reason for this initial deficiency was that contact with the sample blunts atomically sharp tips, which are mandatory for successful atomic resolution imaging. This problem was overcome in the mid-1990s with the introduction of noncontact atomic force microscopy (NC-AFM), which represents a version of AFM where the cantilever is oscillated close to the sample surface without actually 'touching' it. This allows the preservation of the atomic sharpness of the tip while interaction-induced changes in the cantilever's resonance frequency are used to quantify the tip-sample distance. Since then, progress has been steady and includes the development of commercial instruments as well as the addition of many new capabilities beyond imaging, such as the identification and manipulation of individual atoms. A series of annual international conferences, starting in Osaka in 1998, have contributed significantly to this outstanding performance. The program of the most recent conference from this series, held in Madrid on 15-19 September 2008, reflects the maturity of this field, with an increasing number of groups developing strong activities that involve novel approaches and applications covering areas well beyond the original vacuum-based imaging. In this special issue of Nanotechnology we present a selection of

  12. Periodicity in bimodal atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Chia-Yun; Santos, Sergio, E-mail: santos-en@yahoo.com; Chiesa, Matteo [Laboratory for Energy and NanoScience (LENS), Institute Center for Future Energy (iFES), Masdar Institute of Science and Technology, Abu Dhabi (United Arab Emirates); Barcons, Victor [Departament de Disseny i Programació de Sistemes Electrònics, UPC - Universitat Politècnica de Catalunya, Av. Bases, 61, 08242 Manresa (Barcelona) (Spain)

    2015-07-28

    Periodicity is fundamental for quantification and the application of conservation principles of many important systems. Here, we discuss periodicity in the context of bimodal atomic force microscopy (AFM). The relationship between the excited frequencies is shown to affect and control both experimental observables and the main expressions quantified via these observables, i.e., virial and energy transfer expressions, which form the basis of the bimodal AFM theory. The presence of a fundamental frequency further simplifies the theory and leads to close form solutions. Predictions are verified via numerical integration of the equation of motion and experimentally on a mica surface.

  13. Atomic force microscopy of model lipid membranes.

    Science.gov (United States)

    Morandat, Sandrine; Azouzi, Slim; Beauvais, Estelle; Mastouri, Amira; El Kirat, Karim

    2013-02-01

    Supported lipid bilayers (SLBs) are biomimetic model systems that are now widely used to address the biophysical and biochemical properties of biological membranes. Two main methods are usually employed to form SLBs: the transfer of two successive monolayers by Langmuir-Blodgett or Langmuir-Schaefer techniques, and the fusion of preformed lipid vesicles. The transfer of lipid films on flat solid substrates offers the possibility to apply a wide range of surface analytical techniques that are very sensitive. Among them, atomic force microscopy (AFM) has opened new opportunities for determining the nanoscale organization of SLBs under physiological conditions. In this review, we first focus on the different protocols generally employed to prepare SLBs. Then, we describe AFM studies on the nanoscale lateral organization and mechanical properties of SLBs. Lastly, we survey recent developments in the AFM monitoring of bilayer alteration, remodeling, or digestion, by incubation with exogenous agents such as drugs, proteins, peptides, and nanoparticles.

  14. High-frequency multimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Adrian P. Nievergelt

    2014-12-01

    Full Text Available Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples.

  15. Atomic Force Microscopy for Soil Analysis

    Science.gov (United States)

    gazze, andrea; doerr, stefan; dudley, ed; hallin, ingrid; matthews, peter; quinn, gerry; van keulen, geertje; francis, lewis

    2016-04-01

    Atomic Force Microscopy (AFM) is a high-resolution surface-sensitive technique, which provides 3-dimensional topographical information and material properties of both stiff and soft samples in their natural environments. Traditionally AFM has been applied to samples with low roughness: hence its use for soil analysis has been very limited so far. Here we report the optimization settings required for a standardization of high-resolution and artefact-free analysis of natural soil with AFM: soil immobilization, AFM probe selection, artefact recognition and minimization. Beyond topography, AFM can be used in a spectroscopic mode to evaluate nanomechanical properties, such as soil viscosity, stiffness, and deformation. In this regards, Bruker PeakForce-Quantitative NanoMechanical (QNM) AFM provides a fast and convenient way to extract physical properties from AFM force curves in real-time to obtain soil nanomechanical properties. Here we show for the first time the ability of AFM to describe the topography of natural soil at nanometre resolution, with observation of micro-components, such as clays, and of nano-structures, possibly of biotic origin, the visualization of which would prove difficult with other instrumentations. Finally, nanomechanical profiling has been applied to different wettability states in soil and the respective physical patterns are discussed.

  16. High-speed atomic force microscopy: imaging and force spectroscopy.

    Science.gov (United States)

    Eghiaian, Frédéric; Rico, Felix; Colom, Adai; Casuso, Ignacio; Scheuring, Simon

    2014-10-01

    Atomic force microscopy (AFM) is the type of scanning probe microscopy that is probably best adapted for imaging biological samples in physiological conditions with submolecular lateral and vertical resolution. In addition, AFM is a method of choice to study the mechanical unfolding of proteins or for cellular force spectroscopy. In spite of 28 years of successful use in biological sciences, AFM is far from enjoying the same popularity as electron and fluorescence microscopy. The advent of high-speed atomic force microscopy (HS-AFM), about 10 years ago, has provided unprecedented insights into the dynamics of membrane proteins and molecular machines from the single-molecule to the cellular level. HS-AFM imaging at nanometer-resolution and sub-second frame rate may open novel research fields depicting dynamic events at the single bio-molecule level. As such, HS-AFM is complementary to other structural and cellular biology techniques, and hopefully will gain acceptance from researchers from various fields. In this review we describe some of the most recent reports of dynamic bio-molecular imaging by HS-AFM, as well as the advent of high-speed force spectroscopy (HS-FS) for single protein unfolding.

  17. Investigating bioconjugation by atomic force microscopy

    Science.gov (United States)

    2013-01-01

    Nanotechnological applications increasingly exploit the selectivity and processivity of biological molecules. Integration of biomolecules such as proteins or DNA into nano-systems typically requires their conjugation to surfaces, for example of carbon-nanotubes or fluorescent quantum dots. The bioconjugated nanostructures exploit the unique strengths of both their biological and nanoparticle components and are used in diverse, future oriented research areas ranging from nanoelectronics to biosensing and nanomedicine. Atomic force microscopy imaging provides valuable, direct insight for the evaluation of different conjugation approaches at the level of the individual molecules. Recent technical advances have enabled high speed imaging by AFM supporting time resolutions sufficient to follow conformational changes of intricately assembled nanostructures in solution. In addition, integration of AFM with different spectroscopic and imaging approaches provides an enhanced level of information on the investigated sample. Furthermore, the AFM itself can serve as an active tool for the assembly of nanostructures based on bioconjugation. AFM is hence a major workhorse in nanotechnology; it is a powerful tool for the structural investigation of bioconjugation and bioconjugation-induced effects as well as the simultaneous active assembly and analysis of bioconjugation-based nanostructures. PMID:23855448

  18. Atomically resolved graphitic surfaces in air by atomic force microscopy.

    Science.gov (United States)

    Wastl, Daniel S; Weymouth, Alfred J; Giessibl, Franz J

    2014-05-27

    Imaging at the atomic scale using atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomic resolution of graphite and hydrogen-intercalated graphene on SiC in air. The main challenges arise from the overall surface cleanliness and the water layers which form on almost all surfaces. To further investigate the influence of the water layers, we compare data taken with a hydrophilic bulk-silicon tip to a hydrophobic bulk-sapphire tip. While atomic resolution can be achieved with both tip materials at moderate interaction forces, there are strong differences in force versus distance spectra which relate to the water layers on the tips and samples. Imaging at very low tip-sample interaction forces results in the observation of large terraces of a naturally occurring stripe structure on the hydrogen-intercalated graphene. This structure has been previously reported on graphitic surfaces that are not covered with disordered adsorbates in ambient conditions (i.e., on graphite and bilayer graphene on SiC, but not on monolayer graphene on SiC). Both these observations indicate that hydrogen-intercalated graphene is close to an ideal graphene sample in ambient environments.

  19. Interfacial forces between silica surfaces measured by atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    DUAN Jinming

    2009-01-01

    Colloidal particle stability and some other interfacial phenomena are governed by interfacial force interactions. The two well known forces are van der Waals force and electrostatic force, as documented by the classical Derjaguin, Landau, Verwey and Overbeek (DLVO) theory. Moreover, advances in modern instrumentation and colloid science suggested that some short-ranged forces or structure forces are important for relevant colloidal systems. The interfacial and/or molecular forces can be measured as a resultant force as function of separation distance by atomic force microscopy (AFM) colloid probe. This article presents a discussion on AFM colloid probe measurement of silica particle and silica wafer surfaces in solutions with some technical notifications in measurement and data convolution mechanisms. The measured forces are then analyzed and discussed based on the 'constant charge' and 'constant potential' models of DLVO theory. The difference between the prediction of DLVO theory and the measured results indicates that there is a strong short-range structure force between the two hydrophilic surfaces, even at extremely low ionic concentration, such as Milli-Q water purity solution.

  20. Interfacial forces between silica surfaces measured by atomic force microscopy.

    Science.gov (United States)

    Duan, Jinming

    2009-01-01

    Colloidal particle stability and some other interfacial phenomena are governed by interfacial force interactions. The two well known forces are van der Waals force and electrostatic force, as documented by the classical Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. Moreover, advances in modern instrumentation and colloid science suggested that some short-ranged forces or structure forces are important for relevant colloidal systems. The interfacial and/or molecular forces can be measured as a resultant force as function of separation distance by atomic force microscopy (AFM) colloid probe. This article presents a discussion on AFM colloid probe measurement of silica particle and silica wafer surfaces in solutions with some technical notifications in measurement and data convolution mechanisms. The measured forces are then analyzed and discussed based on the 'constant charge' and 'constant potential' models of DLVO theory. The difference between the prediction of DLVO theory and the measured results indicates that there is a strong short-range structure force between the two hydrophilic surfaces, even at extremely low ionic concentration, such as Milli-Q water purity solution.

  1. Force dependent metalloprotein conductance by conducting atomic force microscopy

    Science.gov (United States)

    Zhao, Jianwei; Davis, Jason J.

    2003-09-01

    Our ability to analyse charge transport through a biological macromolecule, pertinent to our understanding not only of biological redox processes but also, for example, to our interpretation of tunnelling imaging, remains a significant practical and theoretical issue. Though much information can be gained by carrying out such examinations at a molecular level, there exist few methods where such controlled analyses are, in fact, feasible. Here we report on the electron transport characteristics of a blue copper metalloprotein as characterized at a refined level by conductive-probe atomic force microscopy. The modulation of this conductance with compressional force has also been examined. Though highly resistive, observations are consistent with the ability of the protein matrix to mediate appreciable tunnelling current. This work, then, paves the way for designed implementation of biomacromolecules into electronic devices.

  2. Microfluidics, Chromatography, and Atomic-Force Microscopy

    Science.gov (United States)

    Anderson, Mark

    2008-01-01

    A Raman-and-atomic-force microscope (RAFM) has been shown to be capable of performing several liquid-transfer and sensory functions essential for the operation of a microfluidic laboratory on a chip that would be used to perform rapid, sensitive chromatographic and spectro-chemical analyses of unprecedentedly small quantities of liquids. The most novel aspect of this development lies in the exploitation of capillary and shear effects at the atomic-force-microscope (AFM) tip to produce shear-driven flow of liquids along open microchannels of a microfluidic device. The RAFM can also be used to perform such functions as imaging liquids in microchannels; removing liquid samples from channels for very sensitive, tip-localized spectrochemical analyses; measuring a quantity of liquid adhering to the tip; and dip-pen deposition from a chromatographic device. A commercial Raman-spectroscopy system and a commercial AFM were integrated to make the RAFM so as to be able to perform simultaneous topographical AFM imaging and surface-enhanced Raman spectroscopy (SERS) at the AFM tip. The Raman-spectroscopy system includes a Raman microprobe attached to an optical microscope, the translation stage of which is modified to accommodate the AFM head. The Raman laser excitation beam, which is aimed at the AFM tip, has a wavelength of 785 nm and a diameter of about 5 m, and its power is adjustable up to 10 mW. The AFM is coated with gold to enable tip-localized SERS.

  3. Immunogold labels: cell-surface markers in atomic force microscopy

    NARCIS (Netherlands)

    Putman, Constant A.J.; Grooth, de Bart G.; Hansma, Paul K.; Hulst, van Niek F.; Greve, Jan

    1993-01-01

    The feasibility of using immunogold labels as cell-surface markers in atomic force microscopy is shown in this paper. The atomic force microscope (AFM) was used to image the surface of immunogold-labeled human lymphocytes. The lymphocytes were isolated from whole blood and labeled by an indirect imm

  4. Atomic Force Microscopy: Theory and Experiment

    Science.gov (United States)

    Gould, Scot A. C.

    When the scanning tunnelling microscope (STM) was invented in 1980, it was hoped that all scientists would benefit from a device that could image surfaces with atomic resolution. Unfortunately while conductors and semiconductors could be imaged with the STM, the vast number of non-conductors, for examples, most ceramics, proteins and cells were virtually unobservable. With the invention of a new device, the atomic force microscope (AFM) suddenly scientists could image the topography of all samples, including non-conductors. The basic construction and operation of the AFM consists of placing a small probe at the end of a spring and measuring the deflection of the spring. Along with the STM, the AFM has revolutionized the study of surfaces in air, water and vacuum. This dissertation reports some of the work I have been involved in. Specifically: (1) building an AFM that used an STM to measure the deflection of the cantilever, (2) building an improved AFM that used an optical level to measure the deflection of the cantilever, microfabricated tips and a water cell, (3) adding a force modulation imaging mode for imaging the surface elasticity, (4) the creation of a theoretical model to help explain atomic imaging, and (5) the creation of image processing techniques that filter out noise inherent in the system and enhance the topographical features of the surface. Using these techniques, we have imaged and analyzed (1) the amino acid crystal DL-leucine and noted that the surface represents an extension of the bulk crystal, (2) imaged polyalanine demonstrating the ability of the microscope to image polymers with molecular resolution, (3) observed the process of blood clotting at the molecular level, (4) imaged important samples including germanium and graphite with atomic resolution and large scale objects including red and white blood cells with nanometer resolution, (5) imaged photographic film as an example of industrial quality control, (6) demonstrated through

  5. Single molecule atomic force microscopy and force spectroscopy of chitosan.

    Science.gov (United States)

    Kocun, Marta; Grandbois, Michel; Cuccia, Louis A

    2011-02-01

    Atomic force microscopy (AFM) and AFM-based force spectroscopy was used to study the desorption of individual chitosan polymer chains from substrates with varying chemical composition. AFM images of chitosan adsorbed onto a flat mica substrate show elongated single strands or aggregated bundles. The aggregated state of the polymer is consistent with the high level of flexibility and mobility expected for a highly positively charged polymer strand. Conversely, the visualization of elongated strands indicated the presence of stabilizing interactions with the substrate. Surfaces with varying chemical composition (glass, self-assembled monolayer of mercaptoundecanoic acid/decanethiol and polytetrafluoroethylene (PTFE)) were probed with chitosan modified AFM tips and the corresponding desorption energies, calculated from plateau-like features, were attributed to the desorption of individual polymer strands. Desorption energies of 2.0±0.3×10(-20)J, 1.8±0.3×10(-20)J and 3.5±0.3×10(-20)J were obtained for glass, SAM of mercaptoundecanoic/dodecanethiol and PTFE, respectively. These single molecule level results can be used as a basis for investigating chitosan and chitosan-based materials for biomaterial applications.

  6. Intermittent contact atomic force microscopy in electrochemical environment

    Energy Technology Data Exchange (ETDEWEB)

    Haering, P.; Koetz, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegenthaler, H. [Bern Univ., Bern (Switzerland)

    1997-06-01

    In situ measurements with Atomic Force Microscopy may cause surface modifications due to the tip-surface interactions. As an alternative and less destructive method, Intermittent Contact Atomic Force Microscopy (ICAFM) has been tested in an electrolytic environment. In the ICAFM mode the tip is not constantly in contact with the surface under investigation but is tapping onto the surface with a certain frequency. A commercial Park Scientific Instruments Microscopy has been modified to enable in situ experiment with ICAFM. It was possible to image iridium oxide films with ICAFM in the electrolytic environment without any noticeable surface modifications. (author) 3 figs., 4 refs.

  7. Quantitative Atomic Force Microscopy with Carbon Monoxide Terminated Tips

    NARCIS (Netherlands)

    Sun, Zhixiang; Boneschanscher, Mark P.; Swart, Ingmar; Vanmaekelbergh, Daniel; Liljeroth, Peter

    2011-01-01

    Noncontact atomic force microscopy (AFM) has recently progressed tremendously in achieving atomic resolution imaging through the use of small oscillation amplitudes and well-defined modification of the tip apex. In particular, it has been shown that picking up simple inorganic molecules (such as CO)

  8. Measurement methods in atomic force microscopy.

    Science.gov (United States)

    Torre, Bruno; Canale, Claudio; Ricci, Davide; Braga, Pier Carlo

    2011-01-01

    This chapter is introductory to the measurements: it explains different measurement techniques both for imaging and for force spectroscopy, on which most of the AFM experiments rely. It gives a general overview of the different techniques and of the output expected from the instrument; therefore it is, at a basic level, a good tool to properly start a new experiment. Concepts introduced in this chapter give the base for understanding the applications shown in the following chapters. Subheading 1 introduces the distinction between spectroscopy and imaging experiments and, within the last ones, between DC and AC mode. Subheading 2 is focused on DC mode (contact), explaining the topography and the lateral force channel. Subheading 3 introduces AC mode, both in noncontact and intermittent contact case. Phase imaging and force modulation are also discussed. Subheading 4 explains how the AFM can be used to measure local mechanical and adhesive properties of specimens by means of force spectroscopy technique. An overview on the state of the art and future trends in this field is also given.

  9. The unfolding of native laminin investigated by atomic force microscopy

    Science.gov (United States)

    Nemes, Cs.; Ramsden, J. J.; Rozlosnik, N.

    2002-10-01

    Atomic force microscopy has been used to directly measure the forces required to unfold individual domains of the extracellular matrix protein laminin. The approach-retraction cycles display a characteristic saw-tooth motif. Tooth heights and separations were used to establish a statistical relation between domain unfolding force and domain extension. The extensible domains of laminin require an unfolding force intermediate between previously established values for α-helical and β-sheet domains in other proteins. The relationship between unfolding force and extension for a given domain is not smooth; discrete steps are observed, interpreted as originating from the modularity of the protein structure.

  10. Atomic-force microscopy investigations of semiconductor nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Teichert, C. [Institute of Physics, University of Leoben (Austria); Brauer, G. [Institut f. Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf (Germany); Djurisic, A. [Department of Physics, University of Hong Kong (China); Sivakov, V.; Scholz, R. [Max Planck Institute of Microstructure Physics, Halle (Germany); Andrae, G. [Institute of Physical High Technology (IPHT), Jena (Germany); Christiansen, S.H. [Physics Department, Martin-Luther-University Halle-Wittenberg (Germany)

    2007-07-01

    One-dimensional nanostructures, such as nanorods or nanotubes, exhibit technological potential for many device applications like electronic, photonic or sensing devices. However, achieving control on the growth of such nanostructures leading to proper dimensional confinement (nanorods diameter, length, density and orientation) is still a challenging task. So far, scanning electron microscopy and transmission electron microscopy are the methods of choice to characterize arrays of free standing semiconductor nanowires. Atomic force microscopy - at a first glance - might not be suited for such a task. Analyzing arrays of vertical ZnO nanorods grown on Si and ITO substrates and individual Si nanowhiskers grown by electron beam evaporation on Si(111), we demonstrate the capabilities of atomic-force microscopy to yield integral information for example on the height variation of the nanorod arrays as well as detailed information on the facet structure of the nanowhiskers.

  11. Atomic Force Microscopy of dynamic protein DNA interactions

    NARCIS (Netherlands)

    Noort, van Simon Johannes Theodorus

    1999-01-01

    In this thesis a dedicated Atomic Force Microscopy (AFM) setup is used for imaging biochemical reactions with molecular resolution. The basis for the high resolution of AFM is the combination of a small probe, close proximity to the sample and a short-range interaction between the probe and the samp

  12. Imaging and manipulation of single viruses by atomic force microscopy

    NARCIS (Netherlands)

    Baclayon, M.; Wuite, G. J. L.; Roos, W. H.

    2010-01-01

    The recent developments in virus research and the application of functional viral particles in nanotechnology and medicine rely on sophisticated imaging and manipulation techniques at nanometre resolution in liquid, air and vacuum. Atomic force microscopy (AFM) is a tool that combines these requirem

  13. Intermolecular Contrast in Atomic Force Microscopy Images without Intermolecular Bonds

    NARCIS (Netherlands)

    Hämäläinen, Sampsa K.; van der Heijden, N.J. (Nadine); van der Lit, Joost; den Hartog, Stephan; Liljeroth, Peter; Swart, Ingmar

    2014-01-01

    Intermolecular features in atomic force microscopy images of organic molecules have been ascribed to intermolecular bonds. A recent theoretical study [P. Hapala et al., Phys. Rev. B 90, 085421 (2014)] showed that these features can also be explained by the flexibility of molecule-terminated tips. We

  14. Microbially influenced corrosion visualized by atomic force microscopy

    Science.gov (United States)

    Telegdi, J.; Keresztes, Z.; Pálinkás, G.; Kálmán, E.; Sand, W.

    Corrosion, biofilm formation and the adsorption of different, corrosion-enhancing microbes (such as Desulfovibrio desulfuricans, Thiobacillus ferrooxidans, Thiobacillus intermedius, Leptospirillum ferrooxidans, and mixed cultures) to different surfaces (iron, copper, pyrite) have been studied in aqueous environment by atomic force microscopy (AFM). It is one of the most effective on-line techniques for imaging surfaces (bacterial, metallic, etc.) with high resolution.

  15. Application of dynamic impedance spectroscopy to atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Kazimierz Darowicki, Artur Zieliński and Krzysztof J Kurzydłowski

    2008-01-01

    Full Text Available Atomic force microscopy (AFM is a universal imaging technique, while impedance spectroscopy is a fundamental method of determining the electrical properties of materials. It is useful to combine those techniques to obtain the spatial distribution of an impedance vector. This paper proposes a new combining approach utilizing multifrequency scanning and simultaneous AFM scanning of an investigated surface.

  16. Atomic force fluorescence microscopy : combining the best of two worlds

    NARCIS (Netherlands)

    Kassies, Roelf

    2005-01-01

    The complementary strengths and weaknesses of AFM and optical microscopy leads to the desire to integrate both techniques into a single microscope. This thesis describes the development of a com-bined AFM / confocal °uorescence microscope. This atomic force °uorescence microscope (AFFM) combines hig

  17. Hydrogen-related contrast in atomic force microscopy

    Science.gov (United States)

    Schmidt, René; Schwarz, Alexander; Wiesendanger, Roland

    2009-07-01

    We study the effect of hydrogen adsorption on gadolinium islands epitaxially grown on W(110) utilizing atomic force microscopy operated in the non-contact regime. In constant force images, gadolinium islands exhibit two height levels, corresponding to hydrogen covered and clean gadolinium areas, respectively. The experimentally measured height differences are strongly bias dependent, showing that the contrast pattern is dominated by electrostatic tip-sample forces. We interpret our experimental findings in terms of a local reduction of the work function and the presence of localized charges on hydrogen covered areas. Both effects lead to a variation of the contact potential difference between tip and surface areas, which are clean or hydrogen covered gadolinium. After clarifying the electrostatic contrast formation, we can unambiguously identify regions of clean gadolinium on the islands. These results are important for further magnetic exchange force microscopy based studies, because hydrogen also alters the magnetic properties locally.

  18. Atomic force microscopy in biomedical research - Methods and protocols

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2011-11-01

    Full Text Available Pier Carlo Braga and Davide Ricci are old friends not only for those researchers familiar with Atomic force microscopy (AFM but also for those beginners (like the undersigned that already enthusiastically welcomed their 2004 edition (for the same Humana press printing types of Atomic force microscopy: Biomedical methods and applications, eventhough I never had used the AFM. That book was much intended to overview the possible AFM applications for a wide range of readers so that they can be in some way stimulated toward the AFM use. In fact, the great majority of scientists is afraid both of the technology behind AFM (that is naturally thought highly demanding in term of concepts not so familiar to biologists and physicians and of the financial costs: both these two factors are conceived unapproachable by the medium range granted scientist usually not educated in terms of biophysics and electronic background....

  19. Probing stem cell differentiation using atomic force microscopy

    Science.gov (United States)

    Liang, Xiaobin; Shi, Xuetao; Ostrovidov, Serge; Wu, Hongkai; Nakajima, Ken

    2016-03-01

    A real-time method using atomic force microscopy (AFM) was developed to probe stem cell differentiation by measuring the mechanical properties of cells and the extracellular matrix (ECM). The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. It is clear that AFM is a facile and useful tool for monitoring the differentiation of stem cells in a non-invasive manner.

  20. Bacterial biofilms investigated by atomic force microscopy and electrochemistry

    DEFF Research Database (Denmark)

    Hu, Yifan

    thesis, Atomic Force Microscopy (AFM) and electrochemistry have been applied to investigate three pathogenic medically important bacterial biofilms, i.e. Pseudomonas aeruginosa (cystic fibrosis pneumonia), Staphylococcus epidermidis (contamination of surgical catheters and indwelling equipment...... attachment on the surface. High-resolution AFM imaging showed no detectable differences among the four strains. Adhesion maps using hydrophobically modified tips compared with bare hydrophilic silicon nitride tips also showed small differences only. This indicates that hydrophobic effects are not the primary...

  1. Nanomechanical Characterization of Bacillus anthracis Spores by Atomic Force Microscopy

    OpenAIRE

    2016-01-01

    The study of structures and properties of bacterial spores is important to understanding spore formation and biological responses to environmental stresses. While significant progress has been made over the years in elucidating the multilayer architecture of spores, the mechanical properties of the spore interior are not known. Here, we present a thermal atomic force microscopy (AFM) study of the nanomechanical properties of internal structures of Bacillus anthracis spores. We developed a nan...

  2. Scanning Tunneling Microscopy, Atomic Force Microscopy, and Related Techniques

    Science.gov (United States)

    1992-02-26

    reducing the sixfold symmetry at the atomic Se surface to that of three-fold symmetry at the molecular WSe2 layer. Van Bakel et al. have imaged the...Technol. B 1991, 9, 1048-5 1. (D238) Akari, S.; Moller, R.; Dransfeld, K. App!. Phys. Let. 1991, 59, 243-5. (D239) Van Bakel , G.P.E.M.; De Hosson

  3. Submolecular Resolution Imaging of molecules by Atomic Force Microscopy:The influence of the Electrostatic Force

    NARCIS (Netherlands)

    van der Lit, J.; Cicco, F.; Hapala, P.; Jelinek, P.; Swart, Ingmar

    2016-01-01

    The forces governing the contrast in submolecular resolution imaging of molecules with atomic force microscopy (AFM) have recently become a topic of intense debate. Here, we show that the electrostatic force is essential to understand the contrast in atomically resolved AFM images of polar molecules

  4. Modeling noncontact atomic force microscopy resolution on corrugated surfaces

    Directory of Open Access Journals (Sweden)

    Kristen M. Burson

    2012-03-01

    Full Text Available Key developments in NC-AFM have generally involved atomically flat crystalline surfaces. However, many surfaces of technological interest are not atomically flat. We discuss the experimental difficulties in obtaining high-resolution images of rough surfaces, with amorphous SiO2 as a specific case. We develop a quasi-1-D minimal model for noncontact atomic force microscopy, based on van der Waals interactions between a spherical tip and the surface, explicitly accounting for the corrugated substrate (modeled as a sinusoid. The model results show an attenuation of the topographic contours by ~30% for tip distances within 5 Å of the surface. Results also indicate a deviation from the Hamaker force law for a sphere interacting with a flat surface.

  5. Nanoprocessing of layered crystalline materials by atomic force microscopy.

    Science.gov (United States)

    Miyake, Shojiro; Wang, Mei

    2015-01-01

    By taking advantage of the mechanical anisotropy of crystalline materials, processing at a single-layer level can be realized for layered crystalline materials with periodically weak bonds. Mica (muscovite), graphite, molybdenum disulfide (MoS2), and boron nitride have layered structures, and there is little interaction between the cleavage planes existing in the basal planes of these materials. Moreover, it is easy to image the atoms on the basal plane, where the processed shape can be observed on the atomic level. This study reviews research evaluating the nanometer-scale wear and friction as well as the nanometer-scale mechanical processing of muscovite using atomic force microscopy (AFM). It also summarizes recent AFM results obtained by our research group regarding the atomic-scale mechanical processing of layered materials including mica, graphite, MoS2, and highly oriented pyrolytic graphite.

  6. Interaction between polystyrene spheres by atomic force microscopy

    CERN Document Server

    Looi, L

    2002-01-01

    The interaction between a single polystyrene particle and a polystyrene substrate has been previously reported by a number of investigators. However, the effects of relative humidity, applied load and contact time on the adhesion of polystyrene surfaces have not been investigated and these effects are poorly understood. It is the primary aim of the current work to characterise the effect of the aforementioned parameters on the adhesion of polystyrene surfaces using atomic force microscopy. The polystyrene used in this study contained 1% of di-vinyl benzene as a cross-linking agent. From the work conducted using the custom-built instrument, the dependency of adhesion forces on the relative humidity is greatest at relative humidities above 60% where capillary forces cause a sharp increase in adhesion with increasing relative humidity. Hysteresis was observed in the solid-solid contact gradient of the accompanying force curves, suggesting non-elastic behaviour at the contact area of the surfaces

  7. Simultaneous Nanomechanical and Electrochemical Mapping: Combining Peak Force Tapping Atomic Force Microscopy with Scanning Electrochemical Microscopy.

    Science.gov (United States)

    Knittel, Peter; Mizaikoff, Boris; Kranz, Christine

    2016-06-21

    Soft electronic devices play a crucial role in, e.g., neural implants as stimulating electrodes, transducers for biosensors, or selective drug-delivery. Because of their elasticity, they can easily adapt to their environment and prevent immunoreactions leading to an overall improved long-term performance. In addition, flexible electronic devices such as stretchable displays will be increasingly used in everyday life, e.g., for so-called electronic wearables. Atomic force microscopy (AFM) is a versatile tool to characterize these micro- and nanostructured devices in terms of their topography. Using advanced imaging techniques such as peak force tapping (PFT), nanomechanical properties including adhesion, deformation, and Young's modulus can be simultaneously mapped along with surface features. However, conventional AFM provides limited laterally resolved information on electrical or electrochemical properties such as the activity of an electrode array. In this study, we present the first combination of AFM with scanning electrochemical microscopy (SECM) in PFT mode, thereby offering spatially correlated electrochemical and nanomechanical information paired with high-resolution topographical data under force control (QNM-AFM-SECM). The versatility of this combined scanning probe approach is demonstrated by mapping topographical, electrochemical, and nanomechanical properties of gold microelectrodes and of gold electrodes patterned onto polydimethylsiloxane.

  8. Observation of DNA Molecules Using Fluorescence Microscopy and Atomic Force Microscopy

    Science.gov (United States)

    Ito, Takashi

    2008-01-01

    This article describes experiments for an undergraduate instrumental analysis laboratory that aim to observe individual double-stranded DNA (dsDNA) molecules using fluorescence microscopy and atomic force microscopy (AFM). dsDNA molecules are observed under several different conditions to discuss their chemical and physical properties. In…

  9. Improved atomic force microscopy cantilever performance by partial reflective coating

    Directory of Open Access Journals (Sweden)

    Zeno Schumacher

    2015-07-01

    Full Text Available Optical beam deflection systems are widely used in cantilever based atomic force microscopy (AFM. Most commercial cantilevers have a reflective metal coating on the detector side to increase the reflectivity in order to achieve a high signal on the photodiode. Although the reflective coating is usually much thinner than the cantilever, it can still significantly contribute to the damping of the cantilever, leading to a lower mechanical quality factor (Q-factor. In dynamic mode operation in high vacuum, a cantilever with a high Q-factor is desired in order to achieve a lower minimal detectable force. The reflective coating can also increase the low-frequency force noise. In contact mode and force spectroscopy, a cantilever with minimal low-frequency force noise is desirable. We present a study on cantilevers with a partial reflective coating on the detector side. For this study, soft (≈0.01 N/m and stiff (≈28 N/m rectangular cantilevers were used with a custom partial coating at the tip end of the cantilever. The Q-factor, the detection and the force noise of fully coated, partially coated and uncoated cantilevers are compared and force distance curves are shown. Our results show an improvement in low-frequency force noise and increased Q-factor for the partially coated cantilevers compared to fully coated ones while maintaining the same reflectivity, therefore making it possible to combine the best of both worlds.

  10. Recognizing nitrogen dopant atoms in graphene using atomic force microscopy

    NARCIS (Netherlands)

    van der Heijden, N.J.; Smith, D.; Calogero, Gaetano; Koster, R.S.; Vanmaekelbergh, D.A.M.; van Huis, M.A.; Swart, I.

    2016-01-01

    Doping graphene by heteroatoms such as nitrogen presents an attractive route to control the position of the Fermi level in the material. We prepared N-doped graphene on Cu(111) and Ir(111) surfaces via chemical vapor deposition of two different molecules. Using scanning tunneling microscopy images a

  11. Characterization of new drug delivery nanosystems using atomic force microscopy

    Science.gov (United States)

    Spyratou, Ellas; Mourelatou, Elena A.; Demetzos, C.; Makropoulou, Mersini; Serafetinides, A. A.

    2015-01-01

    Liposomes are the most attractive lipid vesicles for targeted drug delivery in nanomedicine, behaving also as cell models in biophotonics research. The characterization of the micro-mechanical properties of drug carriers is an important issue and many analytical techniques are employed, as, for example, optical tweezers and atomic force microscopy. In this work, polyol hyperbranched polymers (HBPs) have been employed along with liposomes for the preparation of new chimeric advanced drug delivery nanosystems (Chi-aDDnSs). Aliphatic polyester HBPs with three different pseudogenerations G2, G3 and G4 with 16, 32, and 64 peripheral hydroxyl groups, respectively, have been incorporated in liposomal formulation. The atomic force microscopy (AFM) technique was used for the comparative study of the morphology and the mechanical properties of Chi-aDDnSs and conventional DDnS. The effects of both the HBPs architecture and the polyesters pseudogeneration number in the stability and the stiffness of chi-aDDnSs were examined. From the force-distance curves of AFM spectroscopy, the Young's modulus was calculated.

  12. OBSERVATION OF DNA PARTIAL DENATURATION BY ATOMIC FORCE MICROSCOPY

    Institute of Scientific and Technical Information of China (English)

    Xin-hua Dai; Zhi-gang Wang; Bo Xiao; Yong-jun Zhang; Chen Wang; Chun-li Bai; Xiao-li Zhang; Jian Xu

    2004-01-01

    Atomic force microscopy was used to investigate the DNA-cetyltrimethylammonium bromide (CTAB) complexes adsorbed on highly ordered pyrolytic graphite (HOPG). These complexes, at low concentrations, can automatically spread out on the surface of HOPG. The DNA-CTAB complexes display a typically extended structure rather than a globular structure. Partially denaturated DNA produced by binding CTAB to DNA is directly observed by AFM with high resolution.The three-dimensional resolution of partially denaturated DNA obtained by AFM is not available by any other technique at present.

  13. Cryogel micromechanics unraveled by atomic force microscopy-based nanoindentation.

    Science.gov (United States)

    Welzel, Petra B; Friedrichs, Jens; Grimmer, Milauscha; Vogler, Steffen; Freudenberg, Uwe; Werner, Carsten

    2014-11-01

    Cell-instructive physical characteristics of macroporous scaffolds, developed for tissue engineering applications, often remain difficult to assess. Here, an atomic force microscopy-based nanoindentation approach is adapted to quantify the local mechanical properties of biohybrid glycosaminoglycan-poly(ethylene glycol) cryogels. Resulting from cryoconcentration effects upon gel formation, cryogel struts are observed to feature a higher stiffness compared to the corresponding bulk hydrogel materials. Local Young's moduli, porosity, and integral moduli of the cryogel scaffolds are compared in dependence on gel formation parameters. The results provide valuable insights into the cryogelation process and a base for adjusting physical characteristics of the obtained cryogel scaffolds, which can critically influence the cellular response.

  14. CO tip functionalization in subatomic resolution atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Minjung [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Chelikowsky, James R. [Center for Computational Materials, Institute for Computational Engineering and Sciences, and Departments of Physics and Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-10-19

    Noncontact atomic force microscopy (nc-AFM) employing a CO-functionalized tip displays dramatically enhanced resolution wherein covalent bonds of polycyclic aromatic hydrocarbon can be imaged. Employing real-space pseudopotential first-principles calculations, we examine the role of CO in functionalizing the nc-AFM tip. Our calculations allow us to simulate full AFM images and ascertain the enhancement mechanism of the CO molecule. We consider two approaches: one with an explicit inclusion of the CO molecule and one without. By comparing our simulations to existing experimental images, we ascribe the enhanced resolution of the CO functionalized tip to the special orbital characteristics of the CO molecule.

  15. Understanding the Plasmonics of Nanostructured Atomic Force Microscopy Tips

    CERN Document Server

    Sanders, Alan; Zhang, Liwu; Turek, Vladimir; Sigle, Daniel O; Lombardi, Anna; Weller, Lee; Baumberg, Jeremy J

    2016-01-01

    Structured metallic tips are increasingly important for optical spectroscopies such as tip-enhanced Raman spectroscopy (TERS), with plasmonic resonances frequently cited as a mechanism for electric field enhancement. We probe the local optical response of sharp and spherical-tipped atomic force microscopy (AFM) tips using a scanning hyperspectral imaging technique to identify plasmonic behaviour. Localised surface plasmon resonances which radiatively couple with far-field light are found only for spherical AFM tips, with little response for sharp AFM tips, in agreement with numerical simulations of the near-field response. The precise tip geometry is thus crucial for plasmon-enhanced spectroscopies, and the typical sharp cones are not preferred.

  16. Near-grain-boundary characterization by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pramanick, A.K., E-mail: pramanick@nmlindia.org [MST Division, National Metallurgical Laboratory, Jamshedpur 831007 (India); Sinha, A. [MST Division, National Metallurgical Laboratory, Jamshedpur 831007 (India); Sastry, G.V.S. [Centre of Advanced Study, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Ghosh, R.N. [MST Division, National Metallurgical Laboratory, Jamshedpur 831007 (India)

    2009-05-15

    Characterization of near-grain boundary is carried out by atomic force microscopy (AFM). It has been observed to be the most suitable technique owing to its capability to investigate the surface at high resolution. Commercial purity-grade nickel processed under different conditions, viz., (i) cold-rolled and annealed and (ii) thermally etched condition without cold rolling, is considered in the present study. AFM crystallographic data match well with the standard data. Hence, it establishes two grain-boundary relations viz., plane matching and coincidence site lattice (CSL {Sigma}=9) relation for the two different sample conditions.

  17. Atomic force microscopy of lead iodide crystal surfaces

    Science.gov (United States)

    George, M. A.; Azoulay, M.; Jayatirtha, H. N.; Biao, Y.; Burger, A.; Collins, W. E.; Silberman, E.

    1994-03-01

    Atomic force microscopy (AFM) was used to characterize the surface of lead iodide crystals. The high vapor pressure of lead iodide prohibits the use of traditional high resolution surface study techniques that require high vacuum conditions. AFM was used to image numerous insulating surface in various ambients, with very little sample preparation techniques needed. Freshly cleaved and modified surfaces, including, chemical and vacuum etched, and air aged surfaces, were examined. Both intrinsic and induced defects were imaged with high resolution. The results were compared to a similar AFM study of mercuric iodide surfaces and it was found that, at ambient conditions, lead iodide is significantly more stable than mercuric iodide.

  18. ATOMIC FORCE MICROSCOPY STUDIES OF POLYCAPROLACTONE RINGED SPHERULITES

    Institute of Scientific and Technical Information of China (English)

    Jian-bin Zhang; De-zhu Ma; Hua Zhong; Xiao-lie Luo

    2000-01-01

    The surface morphology of free-surface PCL ringed spherulites was investigated by using atomic force microscopy. The spherulites were obtained by crystallization of PCL/PVC blends of different compositions. It was found that the ringed spherulite exhibited regularly fluctuating rings on its surface. Compared with the bright-dark ring pattern of the spherulite under a polarizing microscope, it was proved that the optical characteristics of the ringed spherulite under polarizing microscope coincided with its surface characteristics. The bright rings in polarizing micrographs of the spherulite coincided with the convex rings on its surface, while the dark rings coincided with the concave rings.

  19. Surface forces studied with colloidal probe atomic force microscopy

    NARCIS (Netherlands)

    Giesbers, M.

    2001-01-01

    Forces between surfaces are a determining factor for the performance of natural as well as synthetic colloidal systems, and play a crucial role in industrial production processes. Measuring these forces is a scientific and experimental challenge and over the years several techniques have been develo

  20. Multifarious applications of atomic force microscopy in forensic science investigations.

    Science.gov (United States)

    Pandey, Gaurav; Tharmavaram, Maithri; Rawtani, Deepak; Kumar, Sumit; Agrawal, Y

    2017-02-11

    Forensic science is a wide field comprising of several subspecialties and uses methods derived from natural sciences for finding criminals and other evidence valid in a legal court. A relatively new area; Nano-forensics brings a new era of investigation in forensic science in which instantaneous results can be produced that determine various agents such as explosive gasses, biological agents and residues in different crime scenes and terrorist activity investigations. This can be achieved by applying Nanotechnology and its associated characterization techniques in forensic sciences. Several characterization techniques exist in Nanotechnology and nano-analysis is one such technique that is used in forensic science which includes Electron microscopes (EM) like Transmission (TEM) and Scanning (SEM), Raman microscopy (Micro -Raman) and Scanning Probe Microscopes (SPMs) like Atomic Force Microscope (AFM). Atomic force microscopy enables surface characterization of different materials by examining their morphology and mechanical properties. Materials that are immeasurable such as hair, body fluids, textile fibers, documents, polymers, pressure sensitive adhesives (PSAs), etc. are often encountered during forensic investigations. This review article will mainly focus on the use of AFM in the examination of different evidence such as blood stains, forged documents, human hair samples, ammunitions, explosives, and other such applications in the field of Forensic Science.

  1. Taking Nanomedicine Teaching into Practice with Atomic Force Microscopy and Force Spectroscopy

    Science.gov (United States)

    Carvalho, Filomena A.; Freitas, Teresa; Santos, Nuno C.

    2015-01-01

    Atomic force microscopy (AFM) is a useful and powerful tool to study molecular interactions applied to nanomedicine. The aim of the present study was to implement a hands-on atomic AFM course for graduated biosciences and medical students. The course comprises two distinct practical sessions, where students get in touch with the use of an atomic…

  2. Electric charges and forces in atomic force microscopy and nano-xerography

    Energy Technology Data Exchange (ETDEWEB)

    Stemmer, A; Ziegler, D; Seemann, L; Naujoks, N [Nanotechnology Group, ETH Zurich, Tannenstrasse 3, 8092 Zurich (Switzerland); Rychen, J [Nanonis GmbH, Technoparkstrasse 1, 8005 Zurich (Switzerland)], E-mail: astemmer@ethz.ch

    2008-12-01

    Electrostatic forces generated by contact potential differences, localized charges, or externally applied voltages play a crucial role in atomic force microscopy. Electrostatic forces mediate the non-contact measurement of local potentials by the Kelvin probe technique, enabling compositional mapping of surfaces. However, if not compensated properly, electrostatic forces lead to height errors in topography images acquired in tapping mode. We present a single scan Kelvin probe force microscopy technique that compensates local electrostatic forces and allows simultaneous height and potential measurements in tapping mode. Electrostatic forces also direct the localized assembly of structures in nano-xerography. Here we describe how positive charges, written into a thin film of poly(methyl)methacrylate with the conductive tip of an atomic force microscope, guide the deposition of carboxyl-functionalized multiwalled carbon nanotubes suspended in isopropyl-alcohol.

  3. Determination of hydration film thickness using atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    PENG Changsheng; SONG Shaoxian; GU Qingbao

    2005-01-01

    Dispersion of a solid particle in water may lead to the formation of hydration film on the particle surface, which can strongly increase the repulsive force between the particles and thus strongly affect the stability of dispersions. The hydration film thickness, which varies with the variation of property of suspension particles, is one of the most important parameters of hydration film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on force-distance curve of atomic force microscopy, for determining the hydration film thickness of particles is developed. The method utilizes the difference of cantilever deflection before, between and after penetrating the hydration films between tip and sample, which reflect the difference of slope on the force-distance curve. 3 samples, mica, glass and stainless steel, were used for hydration thickness determination, and the results show that the hydration film thickness between silicon tip and mica, glass and stainless steel are 30.0(2.0, 29.0(1.0 and 32.5(2.5 nm, respectively.

  4. High resolution atomic force microscopy of double-stranded RNA

    Science.gov (United States)

    Ares, Pablo; Fuentes-Perez, Maria Eugenia; Herrero-Galán, Elías; Valpuesta, José M.; Gil, Adriana; Gomez-Herrero, Julio; Moreno-Herrero, Fernando

    2016-06-01

    Double-stranded (ds) RNA mediates the suppression of specific gene expression, it is the genetic material of a number of viruses, and a key activator of the innate immune response against viral infections. The ever increasing list of roles played by dsRNA in the cell and its potential biotechnological applications over the last decade has raised an interest for the characterization of its mechanical properties and structure, and that includes approaches using Atomic Force Microscopy (AFM) and other single-molecule techniques. Recent reports have resolved the structure of dsDNA with AFM at unprecedented resolution. However, an equivalent study with dsRNA is still lacking. Here, we have visualized the double helix of dsRNA under near-physiological conditions and at sufficient resolution to resolve the A-form sub-helical pitch periodicity. We have employed different high-sensitive force-detection methods and obtained images with similar spatial resolution. Therefore, we show here that the limiting factors for high-resolution AFM imaging of soft materials in liquid medium are, rather than the imaging mode, the force between the tip and the sample and the sharpness of the tip apex.Double-stranded (ds) RNA mediates the suppression of specific gene expression, it is the genetic material of a number of viruses, and a key activator of the innate immune response against viral infections. The ever increasing list of roles played by dsRNA in the cell and its potential biotechnological applications over the last decade has raised an interest for the characterization of its mechanical properties and structure, and that includes approaches using Atomic Force Microscopy (AFM) and other single-molecule techniques. Recent reports have resolved the structure of dsDNA with AFM at unprecedented resolution. However, an equivalent study with dsRNA is still lacking. Here, we have visualized the double helix of dsRNA under near-physiological conditions and at sufficient resolution to

  5. Nanomechanics of Cells and Biomaterials Studied by Atomic Force Microscopy.

    Science.gov (United States)

    Kilpatrick, Jason I; Revenko, Irène; Rodriguez, Brian J

    2015-11-18

    The behavior and mechanical properties of cells are strongly dependent on the biochemical and biomechanical properties of their microenvironment. Thus, understanding the mechanical properties of cells, extracellular matrices, and biomaterials is key to understanding cell function and to develop new materials with tailored mechanical properties for tissue engineering and regenerative medicine applications. Atomic force microscopy (AFM) has emerged as an indispensable technique for measuring the mechanical properties of biomaterials and cells with high spatial resolution and force sensitivity within physiologically relevant environments and timescales in the kPa to GPa elastic modulus range. The growing interest in this field of bionanomechanics has been accompanied by an expanding array of models to describe the complexity of indentation of hierarchical biological samples. Furthermore, the integration of AFM with optical microscopy techniques has further opened the door to a wide range of mechanotransduction studies. In recent years, new multidimensional and multiharmonic AFM approaches for mapping mechanical properties have been developed, which allow the rapid determination of, for example, cell elasticity. This Progress Report provides an introduction and practical guide to making AFM-based nanomechanical measurements of cells and surfaces for tissue engineering applications.

  6. Submolecular Resolution Imaging of Molecules by Atomic Force Microscopy: The Influence of the Electrostatic Force

    Science.gov (United States)

    van der Lit, Joost; Di Cicco, Francesca; Hapala, Prokop; Jelinek, Pavel; Swart, Ingmar

    2016-03-01

    The forces governing the contrast in submolecular resolution imaging of molecules with atomic force microscopy (AFM) have recently become a topic of intense debate. Here, we show that the electrostatic force is essential to understand the contrast in atomically resolved AFM images of polar molecules. Specifically, we image strongly polarized molecules with negatively and positively charged tips. A contrast inversion is observed above the polar groups. By taking into account the electrostatic forces between tip and molecule, the observed contrast differences can be reproduced using a molecular mechanics model. In addition, we analyze the height dependence of the various force components contributing to the high-resolution AFM contrast.

  7. Atomic force microscopy and spectroscopy of native membrane proteins.

    Science.gov (United States)

    Müller, Daniel J; Engel, Andreas

    2007-01-01

    Membrane proteins comprise 30% of the proteome of higher organisms. They mediate energy conversion, signal transduction, solute transport and secretion. Their native environment is a bilayer in a physiological buffer solution, hence their structure and function are preferably assessed in this environment. The surface structure of single membrane proteins can be determined in buffer solutions by atomic force microscopy (AFM) at a lateral resolution of less than 1 nm and a vertical resolution of 0.1-0.2 nm. Moreover, single proteins can be directly addressed, stuck to the AFM stylus and subsequently unfolded, revealing the molecular interactions of the protein studied. The examples discussed here illustrate the power of AFM in the structural analysis of membrane proteins in a native environment.

  8. Some issues on atomic force microscopy based surface characterization

    Institute of Scientific and Technical Information of China (English)

    CHEN Yu-hang; HUANG Wen-hao

    2007-01-01

    Influences of tip radius and sampling interval on applying atomic force microscopy(AFM)in quantitative surface evaluations are investigated by numerical simulations and experiments. Several evaluation parameters of surfaces ranging from amplitude to functional parameters are studied. Numerical and experimental results are in good agreements. The accuracy of estimating tip radius on random rough surface with Gaussian distribution of heights using a blind reconstruction method is also discussed theoretically. It is found that the accuracy is greatly depending on the ratio of actual tip radius to rootmean-square (rms) radius of curvature. To obtain an accurate estimation of tip radius under Gaussian rough surface, the ratio has to be larger than 3/2.

  9. Inverstigation of chromatin folding patterns by atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    ZHANGYi; OUYANGZhenqian; 等

    1999-01-01

    The chromatin folding patterns in air and liquid were studied by atomic force microscopy(AFM),A gentle water-air interface method was adopted to spread chromatin from interphase nucleus of chicken erythrocyte.The chromatin was absorbed on APS-mica surface and studied with AFM,Beads-on a-string were observed and many higher-order structrues such as superbeads with dimensions 40-60nm in diameter and 4-7nm in height were found to string together to make chromation fibers.When sample spreading and absorbing time were shortened.higher-order chromatin fibers with 60-120nm in width were observed in air as well as under water environment.These chromatin structures may reflect chromatin folding patterns in the living cells.

  10. Photocatalytic degradation of bacteriophages evidenced by atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Emrecan Soylemez

    Full Text Available Methods to supply fresh water are becoming increasingly critical as the world population continues to grow. Small-diameter hazardous microbes such as viruses (20-100 nm diameter can be filtered by size exclusion, but in this approach the filters are fouled. Thus, in our research, we are investigating an approach in which filters will be reusable. When exposed to ultraviolet (UV illumination, titanate materials photocatalytically evolve (•OH and O2(•- radicals, which attack biological materials. In the proposed approach, titanate nanosheets are deposited on a substrate. Viruses adsorb on these nanosheets and degrade when exposed to UV light. Using atomic force microscopy (AFM, we image adsorbed viruses and demonstrate that they are removed by UV illumination in the presence of the nanosheets, but not in their absence.

  11. Atomic force microscopy for the examination of single cell rheology.

    Science.gov (United States)

    Okajima, Takaharu

    2012-11-01

    Rheological properties of living cells play important roles in regulating their various biological functions. Therefore, measuring cell rheology is crucial for not only elucidating the relationship between the cell mechanics and functions, but also mechanical diagnosis of single cells. Atomic force microscopy (AFM) is becoming a useful technique for single cell diagnosis because it allows us to measure the rheological properties of adherent cells at any region on the surface without any modifications. In this review, we summarize AFM techniques for examining single cell rheology in frequency and time domains. Recent applications of AFM for investigating the statistical analysis of single cell rheology in comparison to other micro-rheological techniques are reviewed, and we discuss what specificity and universality of cell rheology are extracted using AFM.

  12. Nanoscale imaging of Bacillus thuringiensis flagella using atomic force microscopy

    Science.gov (United States)

    Gillis, Annika; Dupres, Vincent; Delestrait, Guillaume; Mahillon, Jacques; Dufrêne, Yves F.

    2012-02-01

    Because bacterial flagella play essential roles in various processes (motility, adhesion, host interactions, secretion), studying their expression in relation to function is an important challenge. Here, we use atomic force microscopy (AFM) to gain insight into the nanoscale surface properties of two wild-type and four mutant strains of Bacillus thuringiensis exhibiting various levels of flagellation. We show that, unlike AFM in liquid, AFM in air is a simple and reliable approach to observe the morphological details of the bacteria, and to quantify the density and dimensions of their flagella. We found that the amount of flagella expressed by the six strains, as observed at the nanoscale, correlates with their microscopic swarming motility. These observations provide novel information on flagella expression in Gram-positive bacteria and demonstrate the power of AFM in genetic studies for the fast assessment of the phenotypic characteristics of bacterial strains altered in cell surface appendages.Because bacterial flagella play essential roles in various processes (motility, adhesion, host interactions, secretion), studying their expression in relation to function is an important challenge. Here, we use atomic force microscopy (AFM) to gain insight into the nanoscale surface properties of two wild-type and four mutant strains of Bacillus thuringiensis exhibiting various levels of flagellation. We show that, unlike AFM in liquid, AFM in air is a simple and reliable approach to observe the morphological details of the bacteria, and to quantify the density and dimensions of their flagella. We found that the amount of flagella expressed by the six strains, as observed at the nanoscale, correlates with their microscopic swarming motility. These observations provide novel information on flagella expression in Gram-positive bacteria and demonstrate the power of AFM in genetic studies for the fast assessment of the phenotypic characteristics of bacterial strains altered in

  13. Subharmonic Oscillations and Chaos in Dynamic Atomic Force Microscopy

    Science.gov (United States)

    Cantrell, John H.; Cantrell, Sean A.

    2015-01-01

    The increasing use of dynamic atomic force microscopy (d-AFM) for nanoscale materials characterization calls for a deeper understanding of the cantilever dynamics influencing scan stability, predictability, and image quality. Model development is critical to such understanding. Renormalization of the equations governing d- AFM provides a simple interpretation of cantilever dynamics as a single spring and mass system with frequency dependent cantilever stiffness and damping parameters. The renormalized model is sufficiently robust to predict the experimentally observed splitting of the free-space cantilever resonance into multiple resonances upon cantilever-sample contact. Central to the model is the representation of the cantilever sample interaction force as a polynomial expansion with coefficients F(sub ij) (i,j = 0, 1, 2) that account for the effective interaction stiffness parameter, the cantilever-to-sample energy transfer, and the amplitude of cantilever oscillation. Application of the Melnikov method to the model equation is shown to predict a homoclinic bifurcation of the Smale horseshoe type leading to a cascade of period doublings with increasing drive displacement amplitude culminating in chaos and loss of image quality. The threshold value of the drive displacement amplitude necessary to initiate subharmonic generation depends on the acoustic drive frequency, the effective damping coefficient, and the nonlinearity of the cantilever-sample interaction force. For parameter values leading to displacement amplitudes below threshold for homoclinic bifurcation other bifurcation scenarios can occur, some of which lead to chaos.

  14. Atomic Force Microscopy of Asymmetric Membranes from Turtle Erythrocytes

    Science.gov (United States)

    Tian, Yongmei; Cai, Mingjun; Xu, Haijiao; Ding, Bohua; Hao, Xian; Jiang, Junguang; Sun, Yingchun; Wang, Hongda

    2014-01-01

    The cell membrane provides critical cellular functions that rely on its elaborate structure and organization. The structure of turtle membranes is an important part of an ongoing study of erythrocyte membranes. Using a combination of atomic force microscopy and single-molecule force spectroscopy, we characterized the turtle erythrocyte membrane structure with molecular resolution in a quasi-native state. High-resolution images both leaflets of turtle erythrocyte membranes revealed a smooth outer membrane leaflet and a protein covered inner membrane leaflet. This asymmetry was verified by single-molecule force spectroscopy, which detects numerous exposed amino groups of membrane proteins in the inner membrane leaflet but much fewer in the outer leaflet. The asymmetric membrane structure of turtle erythrocytes is consistent with the semi-mosaic model of human, chicken and fish erythrocyte membrane structure, making the semi-mosaic model more widely applicable. From the perspective of biological evolution, this result may support the universality of the semi-mosaic model. PMID:25134535

  15. Introduction to Atomic Force Microscopy (AFM) in Biology.

    Science.gov (United States)

    Kreplak, Laurent

    2016-08-01

    The atomic force microscope (AFM) has the unique capability of imaging biological samples with molecular resolution in buffer solution over a wide range of time scales from milliseconds to hours. In addition to providing topographical images of surfaces with nanometer- to angstrom-scale resolution, forces between single molecules and mechanical properties of biological samples can be investigated from the nano-scale to the micro-scale. Importantly, the measurements are made in buffer solutions, allowing biological samples to "stay alive" within a physiological-like environment while temporal changes in structure are measured-e.g., before and after addition of chemical reagents. These qualities distinguish AFM from conventional imaging techniques of comparable resolution, e.g., electron microscopy (EM). This unit provides an introduction to AFM on biological systems and describes specific examples of AFM on proteins, cells, and tissues. The physical principles of the technique and methodological aspects of its practical use and applications are also described. © 2016 by John Wiley & Sons, Inc.

  16. Minimizing tip-sample forces in jumping mode atomic force microscopy in liquid

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Esteban, A. [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Horcas, I. [Nanotec Electronica S.L., Centro Empresarial Euronova 3, Ronda de Poniente 12, 28760 Tres Cantos, Madrid (Spain); Hernando-Perez, M. [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ares, P. [Nanotec Electronica S.L., Centro Empresarial Euronova 3, Ronda de Poniente 12, 28760 Tres Cantos, Madrid (Spain); Perez-Berna, A.J.; San Martin, C.; Carrascosa, J.L. [Centro Nacional de Biotecnologia (CNB-CSIC), Darwin 3, 28049 Madrid (Spain); Pablo, P.J. de [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Gomez-Herrero, J., E-mail: julio.gomez@uam.es [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2012-03-15

    Control and minimization of tip-sample interaction forces are imperative tasks to maximize the performance of atomic force microscopy. In particular, when imaging soft biological matter in liquids, the cantilever dragging force prevents identification of the tip-sample mechanical contact, resulting in deleterious interaction with the specimen. In this work we present an improved jumping mode procedure that allows detecting the tip-sample contact with high accuracy, thus minimizing the scanning forces ({approx}100 pN) during the approach cycles. To illustrate this method we report images of human adenovirus and T7 bacteriophage particles which are prone to uncontrolled modifications when using conventional jumping mode. -- Highlights: Black-Right-Pointing-Pointer Improvement in atomic force microscopy in buffer solution. Black-Right-Pointing-Pointer Peak force detection. Black-Right-Pointing-Pointer Subtracting the cantilever dragging force. Black-Right-Pointing-Pointer Forces in the 100 pN range. Black-Right-Pointing-Pointer Imaging of delicate viruses with atomic force microscopy.

  17. [Application of atomic force microscopy (AFM) in ophthalmology].

    Science.gov (United States)

    Milka, Michał; Mróz, Iwona; Jastrzebska, Maria; Wrzalik, Roman; Dobrowolski, Dariusz; Roszkowska, Anna M; Moćko, Lucyna; Wylegała, Edward

    2012-01-01

    Atomic force microscopy (AFM) allows to examine surface of different biological objects in the nearly physiological conditions at the nanoscale. The purpose of this work is to present the history of introduction and the potential applications of the AFM in ophthalmology research and clinical practice. In 1986 Binnig built the AFM as a next generation of the scanning tunnelling microscope (STM). The functional principle of AFM is based on the measurement of the forces between atoms on the sample surface and the probe. As a result, the three-dimensional image of the surface with the resolution on the order of nanometres can be obtained. Yamamoto used as the first the AFM on a wide scale in ophthalmology. The first investigations used the AFM method to study structure of collagen fibres of the cornea and of the sclera. Our research involves the analysis of artificial intraocular lenses (IOLs). According to earlier investigations, e.g. Lombardo et al., the AFM was used to study only native IOLs. Contrary to the earlier investigations, we focused our measurements on lenses explanted from human eyes. The surface of such lenses is exposed to the influence of the intraocular aqueous environment, and to the related impacts of biochemical processes. We hereby present the preliminary results of our work in the form of AFM images depicting IOL surface at the nanoscale. The images allowed us to observe early stages of the dye deposit formation as well as local calcinosis. We believe that AFM is a very promising tool for studying the structure of IOL surface and that further observations will make it possible to explain the pathomechanism of artificial intraocular lens opacity formation.

  18. Atomic Steps with tuning-fork-based noncontact atomic force microscopy

    NARCIS (Netherlands)

    Rensen, W.H.J.; Hulst, van N.F.; Ruiter, A.G.T.; West, P.E.

    1999-01-01

    Tuning forks as tip-sample distance detectors are a promising and versatile alternative to conventional cantilevers with optical beam deflection in noncontact atomic force microscopy (AFM). Both theory and experiments are presented to make a comparison between conventional and tuning-fork-based AFM.

  19. Atomic force microscopy to study intermolecular forces and bonds associated with bacteria.

    Science.gov (United States)

    Lower, Steven K

    2011-01-01

    Atomic force microscopy (AFM) operates on a very different principle than other forms of microscopy, such as optical microscopy or electron microscopy. The key component of an AFM is a cantilever that bends in response to forces that it experiences as it touches another surface. Forces as small as a few picoNewtons can be detected and probed with AFM. AFM has become very useful in biological sciences because it can be used on living cells that are immersed in water. AFM is particularly useful when the cantilever is modified with chemical groups (e.g. amine or carboxylic groups), small beads (e.g. glass or latex), or even a bacterium. This chapter describes how AFM can be used to measure forces and bonds between a bacterium and another surface. This paper also provides an example of the use of AFM on Staphylococcus aureus, a Gram-positive bacterium that is often associated with biofilms in humans.

  20. Force-Mediated Kinetics of Single P-Selectin/Ligand Complexes Observed by Atomic Force Microscopy

    Science.gov (United States)

    Fritz, Jurgen; Katopodis, Andreas G.; Kolbinger, Frank; Anselmetti, Dario

    1998-10-01

    Leukocytes roll along the endothelium of postcapillary venules in response to inflammatory signals. Rolling under the hydrodynamic drag forces of blood flow is mediated by the interaction between selectins and their ligands across the leukocyte and endothelial cell surfaces. Here we present force-spectroscopy experiments on single complexes of P-selectin and P-selectin glycoprotein ligand-1 by atomic force microscopy to determine the intrinsic molecular properties of this dynamic adhesion process. By modeling intermolecular and intramolecular forces as well as the adhesion probability in atomic force microscopy experiments we gain information on rupture forces, elasticity, and kinetics of the P-selectin/P-selectin glycoprotein ligand-1 interaction. The complexes are able to withstand forces up to 165 pN and show a chain-like elasticity with a molecular spring constant of 5.3 pN nm-1 and a persistence length of 0.35 nm. The dissociation constant (off-rate) varies over three orders of magnitude from 0.02 s-1 under zero force up to 15 s-1 under external applied forces. Rupture force and lifetime of the complexes are not constant, but directly depend on the applied force per unit time, which is a product of the intrinsic molecular elasticity and the external pulling velocity. The high strength of binding combined with force-dependent rate constants and high molecular elasticity are tailored to support physiological leukocyte rolling.

  1. Atomic force microscopy study of biaxially oriented polypropylene films

    Science.gov (United States)

    Nie, H.-Y.; Walzak, M. J.; McIntyre, N. S.

    2004-08-01

    Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.

  2. Poroelasticity of cell nuclei revealed through atomic force microscopy characterization

    Science.gov (United States)

    Wei, Fanan; Lan, Fei; Liu, Bin; Liu, Lianqing; Li, Guangyong

    2016-11-01

    With great potential in precision medical application, cell biomechanics is rising as a hot topic in biology. Cell nucleus, as the largest component within cell, not only contributes greatly to the cell's mechanical behavior, but also serves as the most vital component within cell. However, cell nucleus' mechanics is still far from unambiguous up to now. In this paper, we attempted to characterize and evaluate the mechanical property of isolated cell nuclei using Atomic Force Microscopy with a tipless probe. As indicated from typical indentation, changing loading rate and stress relaxation experiment results, cell nuclei showed significant dynamically mechanical property, i.e., time-dependent mechanics. Furthermore, through theoretical analysis, finite element simulation and stress relaxation experiment, the nature of nucleus' mechanics was better described by poroelasticity, rather than viscoelasticity. Therefore, the essence of nucleus' mechanics was clarified to be poroelastic through a sophisticated analysis. Finally, we estimated the poroelastic parameters for nuclei of two types of cells through a combination of experimental data and finite element simulation.

  3. Advances in the atomic force microscopy for critical dimension metrology

    Science.gov (United States)

    Hussain, Danish; Ahmad, Khurshid; Song, Jianmin; Xie, Hui

    2017-01-01

    Downscaling, miniaturization and 3D staking of the micro/nano devices are burgeoning phenomena in the semiconductor industry which have posed sophisticated challenges in the critical dimension (CD) metrology. Over the past few years, atomic force microscopy (AFM) has emerged as an important CD metrology technique in meeting these challenges because of its high accuracy, 3D imaging capability, high spatial resolution and non-destructive nature. In this article, advances in the AFM based critical dimension (CD) metrology are systematically reviewed and discussed. CD metrology AFM techniques, strengths, limitations and scanning algorithms are described. Developments towards accurate measurements such as creep and hysteresis compensation of the piezoelectric scanners, their calibration and tip characterization are discussed. In addition, image reconstruction and measures for achieving high accuracy CD measurements with hybrid metrology technique are also discussed. CD metrology challenges offered by the next generation lithography (NGL) techniques such as those associated with the 3D nanodevices of 10 nm node and beyond have been highlighted.

  4. Wide Stiffness Range Cavity Optomechanical Sensors for Atomic Force Microscopy

    CERN Document Server

    Liu, Yuxiang; Aksyuk, Vladimir; Srinivasan, Kartik

    2012-01-01

    We report on progress in developing compact sensors for atomic force microscopy (AFM), in which the mechanical transducer is integrated with near-field optical readout on a single chip. The motion of a nanoscale, doubly-clamped cantilever was transduced by an adjacent high quality factor silicon microdisk cavity. In particular, we show that displacement sensitivity on the order of 1 fm/(Hz)^(1/2) can be achieved while the cantilever stiffness is varied over four orders of magnitude (\\approx 0.01 N/m to \\approx 290 N/m). The ability to transduce both very soft and very stiff cantilevers extends the domain of applicability of this technique, potentially ranging from interrogation of microbiological samples (soft cantilevers) to imaging with high resolution (stiff cantilevers). Along with mechanical frequencies (> 250 kHz) that are much higher than those used in conventional AFM probes of similar stiffness, these results suggest that our cavity optomechanical sensors may have application in a wide variety of hig...

  5. An atomic force microscopy investigation of cyanophage structure.

    Science.gov (United States)

    Kuznetsov, Yurii G; Chang, Sheng-Chieh; Credaroli, Arielle; Martiny, Jennifer; McPherson, Alexander

    2012-12-01

    Marine viruses have only relatively recently come to the attention of molecular biologists, and the extraordinary diversity of potential host organisms suggests a new wealth of genetic and structural forms. A promising technology for characterizing and describing the viruses structurally is atomic force microscopy (AFM). We provide examples here of some of the different architectures and novel structural features that emerge from even a very limited investigation, one focused on cyanophages, viruses that infect cyanobacteria (blue-green algae). These were isolated by phage selection of viruses collected from California coastal waters. We present AFM images of tailed, spherical, filamentous, rod shaped viruses, and others of eccentric form. Among the tailed phages numerous myoviruses were observed, some having long tail fibers, some other none, and some having no visible baseplate. Syphoviruses and a podovirus were also seen. We also describe a unique structural features found on some tailed marine phages that appear to have no terrestrial homolog. These are long, 450 nm, complex helical tail fibers terminating in a unique pattern of 3+1 globular units made up of about 20 small proteins.

  6. Actuation of atomic force microscopy microcantilevers using contact acoustic nonlinearities

    Energy Technology Data Exchange (ETDEWEB)

    Torello, D.; Degertekin, F. Levent, E-mail: levent.degertekin@me.gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2013-11-15

    A new method of actuating atomic force microscopy (AFM) cantilevers is proposed in which a high frequency (>5 MHz) wave modulated by a lower frequency (∼300 kHz) wave passes through a contact acoustic nonlinearity at the contact interface between the actuator and the cantilever chip. The nonlinearity converts the high frequency, modulated signal to a low frequency drive signal suitable for actuation of tapping-mode AFM probes. The higher harmonic content of this signal is filtered out mechanically by the cantilever transfer function, providing for clean output. A custom probe holder was designed and constructed using rapid prototyping technologies and off-the-shelf components and was interfaced with an Asylum Research MFP-3D AFM, which was then used to evaluate the performance characteristics with respect to standard hardware and linear actuation techniques. Using a carrier frequency of 14.19 MHz, it was observed that the cantilever output was cleaner with this actuation technique and added no significant noise to the system. This setup, without any optimization, was determined to have an actuation bandwidth on the order of 10 MHz, suitable for high speed imaging applications. Using this method, an image was taken that demonstrates the viability of the technique and is compared favorably to images taken with a standard AFM setup.

  7. Application of atomic force microscopy in blood research

    Institute of Scientific and Technical Information of China (English)

    Xiao-Long Ji; Ya-Min Ma; Tong Yin; Ming-Shi Shen; Xin Xu; Wei Guan

    2005-01-01

    AIM: To find suitable solutions having lesser granules and keeping erythrocytes in normal shapes under atomic force microscopy (AFM).METHODS: Eight kinds of solutions, 1% formaldehyde,PBS buffer (pH7.2), citrate buffer (pH6,0), 0.9% NaCl,5% dextrose, TAE, 1640 medium and 5% EDTA-K2, were selected from commonly used laboratory solutions, and venous blood from a healthy human volunteer was drawn and anticoagulated with EDTA-K2. Before scanned by AFM (NanoScopeⅢa SPM, Digital Instruments, Santa Barbara,CA), a kind of intermixture was deposited on freshly cleaved mica and then dried in the constant temperature cabinet (37 ℃).RESULTS: One percent formaldehyde, citrate buffer, 5%dextrose, TAE, were found to keep human erythrocytes in normal shape with few particles. Processed by these solutions, fine structures of human erythrocyte membrane were obtained.CONCLUSION: One percent formaldehyde, citrate buffer,5% dextrose and TAE may be applied to disposeerythrocytes in AFM. The results may offer meaningful data for clinical diagnosis of blood by AFM.

  8. Medical applications of atomic force microscopy and Raman spectroscopy.

    Science.gov (United States)

    Choi, Samjin; Jung, Gyeong Bok; Kim, Kyung Sook; Lee, Gi-Ja; Park, Hun-Kuk

    2014-01-01

    This paper reviews the recent research and application of atomic force microscopy (AFM) and Raman spectroscopy techniques, which are considered the multi-functional and powerful toolkits for probing the nanostructural, biomechanical and physicochemical properties of biomedical samples in medical science. We introduce briefly the basic principles of AFM and Raman spectroscopy, followed by diagnostic assessments of some selected diseases in biomedical applications using them, including mitochondria isolated from normal and ischemic hearts, hair fibers, individual cells, and human cortical bone. Finally, AFM and Raman spectroscopy applications to investigate the effects of pharmacotherapy, surgery, and medical device therapy in various medicines from cells to soft and hard tissues are discussed, including pharmacotherapy--paclitaxel on Ishikawa and HeLa cells, telmisartan on angiotensin II, mitomycin C on strabismus surgery and eye whitening surgery, and fluoride on primary teeth--and medical device therapy--collagen cross-linking treatment for the management of progressive keratoconus, radiofrequency treatment for skin rejuvenation, physical extracorporeal shockwave therapy for healing of Achilles tendinitis, orthodontic treatment, and toothbrushing time to minimize the loss of teeth after exposure to acidic drinks.

  9. Potential contributions of noncontact atomic force microscopy for the future Casimir force measurements

    CERN Document Server

    Kim, W J

    2010-01-01

    Surface electric noise, i.e., the non-uniform distribution of charges and potentials on a surface, poses a great experimental challenge in modern precision force measurements. Such a challenge is encountered in a number of different experimental circumstances. The scientists employing atomic force microscopy (AFM) have long focused their efforts to understand the surface-related noise issues via variants of AFM techniques, such as Kelvin probe force microscopy or electric force microscopy. Recently, the physicists investigating quantum vacuum fluctuation phenomena between two closely-spaced objects have also begun to collect experimental evidence indicating a presence of surface effects neglected in their previous analyses. It now appears that the two seemingly disparate science communities are encountering effects rooted in the same surface phenomena. In this report, we suggest specific experimental tasks to be performed in the near future that are crucial not only for fostering needed collaborations between...

  10. Correlative atomic force microscopy and localization-based super-resolution microscopy: revealing labelling and image reconstruction artefacts.

    Science.gov (United States)

    Monserrate, Aitor; Casado, Santiago; Flors, Cristina

    2014-03-17

    Hybrid microscopy: A correlative microscopy tool that combines in situ super-resolution fluorescence microscopy based on single-molecule localization and atomic force microscopy is presented. Direct comparison with high- resolution topography allows the authors to improve fluorescence labeling and image analysis in super-resolution imaging.

  11. Dimensional characterization of extracellular vesicles using atomic force microscopy

    Science.gov (United States)

    Sebaihi, N.; De Boeck, B.; Yuana, Y.; Nieuwland, R.; Pétry, J.

    2017-03-01

    Extracellular vesicles (EV) are small biological entities released from cells into body fluids. EV are recognized as mediators in intercellular communication and influence important physiological processes. It has been shown that the concentration and composition of EV in body fluids may differ from healthy subjects to patients suffering from particular disease. So, EV have gained a strong scientific and clinical interest as potential biomarkers for diagnosis and prognosis of disease. Due to their small size, accurate detection and characterization of EV remain challenging. The aim of the presented work is to propose a characterization method of erythrocyte-derived EV using atomic force microscopy (AFM). The vesicles are immobilized on anti-CD235a-modified mica and analyzed by AFM under buffer liquid and dry conditions. EV detected under both conditions show very similar sizes namely ~30 nm high and ~90 nm wide. The size of these vesicles remains stable over drying time as long as 7 d at room temperature. Since the detected vesicles are not spherical, EV are characterized by their height and diameter, and not only by the height as is usually done for spherical nanoparticles. In order to obtain an accurate measurement of EV diameters, the geometry of the AFM tip was evaluated to account for the lateral broadening artifact inherent to AFM measurements. To do so, spherical polystyrene (PS) nanobeads and EV were concomitantly deposited on the same mica substrate and simultaneously measured by AFM under dry conditions. By applying this procedure, direct calibration of the AFM tip could be performed together with EV characterization under identical experimental conditions minimizing external sources of uncertainty on the shape and size of the tip, thus allowing standardization of EV measurement.

  12. Low temperature corneal laser welding investigated by atomic force microscopy

    Science.gov (United States)

    Matteini, Paolo; Sbrana, Francesca; Tiribilli, Bruno; Pini, Roberto

    2009-02-01

    The structural modifications in the stromal matrix induced by low-temperature corneal laser welding were investigated by atomic force microscopy (AFM). This procedure consists of staining the wound with Indocyanine Green (ICG), followed by irradiation with a near-infrared laser operated at low-power densities. This induces a local heating in the 55-65 °C range. In welded tissue, extracellular components undergo heat-induced structural modifications, resulting in a joining effect between the cut edges. However, the exact mechanism generating the welding, to date, is not completely understood. Full-thickness cuts, 3.5 mm in length, were made in fresh porcine cornea samples, and these were then subjected to laser welding operated at 16.7 W/cm2 power density. AFM imaging was performed on resin-embedded semi-thin slices once they had been cleared by chemical etching, in order to expose the stromal bulk of the tissue within the section. We then carried out a morphological analysis of characteristic fibrillar features in the laser-treated and control samples. AFM images of control stromal regions highlighted well-organized collagen fibrils (36.2 +/- 8.7 nm in size) running parallel to each other as in a typical lamellar domain. The fibrils exhibited a beaded pattern with a 22-39 nm axial periodicity. Laser-treated corneal regions were characterized by a significant disorganization of the intralamellar architecture. At the weld site, groups of interwoven fibrils joined the cut edges, showing structural properties that were fully comparable with those of control regions. This suggested that fibrillar collagen is not denatured by low-temperature laser welding, confirming previous transmission electron microscopy (TEM) observations, and thus it is probably not involved in the closure mechanism of corneal cuts. The loss of fibrillar organization may be related to some structural modifications in some interfibrillar substance as proteoglycans or collagen VI. Furthermore, AFM

  13. Vacuum chamber for sample attachment in atomic force microscopy

    NARCIS (Netherlands)

    Putman, Constant A.J.; Werf, van der Kees O.; Oort, van Geeske; Grooth, de Bart G.; Hulst, van Niek F.; Greve, Jan

    1992-01-01

    A small ring-shaped vacuum chamber has been constructed and connected to the piezotube used for scanning samples in the atomic force microscope (AFM). Samples made up of any material, up to 50 mm in diameter, can be firmly attached o­nto the piezotube without causing damage to the sample. A 50-l bee

  14. Characterization and Detection of Biological Weapons with Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Malkin, A J; Plomp, M; Leighton, T J; McPherson, A

    2006-09-25

    Critical gaps exist in our capabilities to rapidly characterize threat agents which could be used in attacks on facilities and military forces. DNA-based PCR and immunoassay-based techniques provide unique identification of species, strains and protein signatures of pathogens. However, differentiation between naturally occurring and weaponized bioagents and the identification of formulation signatures are beyond current technologies. One of the most effective and often the only definitive means to identify a threat agent is by its direct visualization. Atomic force microscopy (AFM) is a rapid imaging technique that covers the size range of most biothreat agents (several nanometers to tens of microns), is capable of resolving pathogen morphology and structure, and could be developed into a portable device for biological weapons (BW) field characterization. AFM can detect pathogens in aerosol, liquid, surface and soil samples while concomitantly acquiring their weaponization and threat agent digital signatures. BW morphological and structural signatures, including modifications to pathogen microstructural architecture and topology that occur during formulation and weaponization, provide the means for their differentiation from crude or purified unformulated agent, processing signatures, as well as assessment of their potential for dispersion, inhalation and environmental persistence. AFM visualization of pathogen morphology and architecture often provides valuable digital signatures and allows direct detection and identification of threat agents. We have demonstrated that pathogens, spanning the size range from several nanometers for small agricultural satellite viruses to almost half micron for pox viruses, and to several microns for bacteria and bacterial spores, can be visualized by AFM under physiological conditions to a resolution of {approx}20-30 {angstrom}. We have also demonstrated that viruses from closely related families could be differentiated by AFM on

  15. Effects of nonlinear forces on dynamic mode atomic force microscopy and spectroscopy.

    Science.gov (United States)

    Das, Soma; Sreeram, P A; Raychaudhuri, A K

    2007-06-01

    In this paper, we describe the effects of nonlinear tip-sample forces on dynamic mode atomic force microscopy and spectroscopy. The jumps and hysteresis observed in the vibration amplitude (A) versus tip-sample distance (h) curves have been traced to bistability in the resonance curve. A numerical analysis of the basic dynamic equation was used to explain the hysteresis in the experimental curve. It has been found that the location of the hysteresis in the A-h curve depends on the frequency of the forced oscillation relative to the natural frequency of the cantilever.

  16. Atomic force microscopy of atomic-scale ledges and etch pits formed during dissolution of quartz

    Science.gov (United States)

    Gratz, A. J.; Manne, S.; Hansma, P. K.

    1991-01-01

    The processes involved in the dissolution and growth of crystals are closely related. Atomic force microscopy (AFM) of faceted pits (called negative crystals) formed during quartz dissolution reveals subtle details of these underlying physical mechanisms for silicates. In imaging these surfaces, the AFM detected ledges less than 1 nm high that were spaced 10 to 90 nm apart. A dislocation pit, invisible to optical and scanning electron microscopy measurements and serving as a ledge source, was also imaged. These observations confirm the applicability of ledge-motion models to dissolution and growth of silicates; coupled with measurements of dissolution rate on facets, these methods provide a powerful tool for probing mineral surface kinetics.

  17. Surface-charge differentiation of streptavidin and avidin by atomic force microscopy-force spectroscopy.

    Science.gov (United States)

    Almonte, Lisa; Lopez-Elvira, Elena; Baró, Arturo M

    2014-09-15

    Chemical information can be obtained by using atomic force microscopy (AFM) and force spectroscopy (FS) with atomic or molecular resolution, even in liquid media. The aim of this paper is to demonstrate that single molecules of avidin and streptavidin anchored to a biotinylated bilayer can be differentiated by using AFM, even though AFM topographical images of the two proteins are remarkably alike. At physiological pH, the basic glycoprotein avidin is positively charged, whereas streptavidin is a neutral protein. This charge difference can be determined with AFM, which can probe electrostatic double-layer forces by using FS. The force curves, owing to the electrostatic interaction, show major differences when measured on top of each protein as well as on the lipid substrate. FS data show that the two proteins are negatively charged. Nevertheless, avidin and streptavidin can be clearly distinguished, thus demonstrating the sensitivity of AFM to detect small changes in the charge state of macromolecules.

  18. Surface microstructure of bitumen characterized by atomic force microscopy.

    Science.gov (United States)

    Yu, Xiaokong; Burnham, Nancy A; Tao, Mingjiang

    2015-04-01

    Bitumen, also called asphalt binder, plays important roles in many industrial applications. It is used as the primary binding agent in asphalt concrete, as a key component in damping systems such as rubber, and as an indispensable additive in paint and ink. Consisting of a large number of hydrocarbons of different sizes and polarities, together with heteroatoms and traces of metals, bitumen displays rich surface microstructures that affect its rheological properties. This paper reviews the current understanding of bitumen's surface microstructures characterized by Atomic Force Microscopy (AFM). Microstructures of bitumen develop to different forms depending on crude oil source, thermal history, and sample preparation method. While some bitumens display surface microstructures with fine domains, flake-like domains, and dendrite structuring, 'bee-structures' with wavy patterns several micrometers in diameter and tens of nanometers in height are commonly seen in other binders. Controversy exists regarding the chemical origin of the 'bee-structures', which has been related to the asphaltene fraction, the metal content, or the crystallizing waxes in bitumen. The rich chemistry of bitumen can result in complicated intermolecular associations such as coprecipitation of wax and metalloporphyrins in asphaltenes. Therefore, it is the molecular interactions among the different chemical components in bitumen, rather than a single chemical fraction, that are responsible for the evolution of bitumen's diverse microstructures, including the 'bee-structures'. Mechanisms such as curvature elasticity and surface wrinkling that explain the rippled structures observed in polymer crystals might be responsible for the formation of 'bee-structures' in bitumen. Despite the progress made on morphological characterization of bitumen using AFM, the fundamental question whether the microstructures observed on bitumen surfaces represent its bulk structure remains to be addressed. In addition

  19. Local Rheology of Human Neutrophils Investigated Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Yong J. Lee, Dipika Patel, Soyeun Park

    2011-01-01

    Full Text Available During the immune response, neutrophils display localized mechanical events by interacting with their environment through the micro-vascular transit, trans-endothelial, and trans-epithelial migration. Nano-mechanical studies of human neutrophils on localized nano-domains could provide the essential information for understanding their immune responsive functions. Using the Atomic Force Microscopy (AFM - based micro-rheology, we have investigated rheological properties of the adherent human neutrophils on local nano-domains. We have applied the modified Hertz model to obtain the viscoelastic moduli from the relatively thick body regions of the neutrophils. In addition, by using more advanced models to account for the substrate effects, we have successfully characterized the rheological properties of the thin leading and tail regions as well. We found a regional difference in the mechanical compliances of the adherent neutrophils. The central regions of neutrophils were significantly stiffer (1,548 ± 871 Pa than the regions closer to the leading edge (686 ± 801 Pa, while the leading edge and the tail (494 ± 537 Pa regions were mechanically indistinguishable. The frequency-dependent elastic and viscous moduli also display a similar regional difference. Over the studied frequency range (100 to 300 Hz, the complex viscoelastic moduli display the partial rubber plateau behavior where the elastic moduli are greater than the viscous moduli for a given frequency. The non-disparaging viscous modulus indicates that the neutrophils display a viscoelastic dynamic behavior rather than a perfect elastic behavior like polymer gels. In addition, we found no regional difference in the structural damping coefficient between the leading edge and the cell body. Thus, we conclude that despite the lower loss and storage moduli, the leading edges of the human neutrophils display partially elastic properties similar to the cell body. These results suggest that the

  20. The Applications of Atomic Force Microscopy to Vision Science

    OpenAIRE

    2010-01-01

    The atomic force microscope (AFM) is widely used in materials science and has found many applications in biological sciences but has been limited in use in vision science. The AFM can be used to image the topography of soft biological materials in their native environments. It can also be used to probe the mechanical properties of cells and extracellular matrices, including their intrinsic elastic modulus and receptor-ligand interactions. In this review, the operation of the AFM is described ...

  1. Transmission electron microscopy and atomic force microscopy characterization of nickel deposition on bacterial cells

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Recently bacterial cells have become attractive biological templates for the fabrication of metal nano- structures or nanomaterials due to their inherent small size, various standard geometrical shapes and abundant source. In this paper, nickel-coated bacterial cells (gram-negative bacteria of Escherichia coli) were fabricated via electroless chemical plating. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) characterization results reveal evident morphological difference between bacterial cells before and after deposition with nickel. The bare cells with smooth surface presented transverse outspreading effect at mica surface. Great changes took place in surface roughness for those bacterial cells after metallization. A large number of nickel nanoparticles were observed to be equably distributed at bacterial surface after activation and subsequent metallization. Furthermore, ultra thin section analytic results validated the presence and uniformity of thin nickel coating at bacterial surface after metallization.

  2. Simultaneous Scanning Ion Conductance Microscopy and Atomic Force Microscopy with Microchanneled Cantilevers

    Science.gov (United States)

    Ossola, Dario; Dorwling-Carter, Livie; Dermutz, Harald; Behr, Pascal; Vörös, János; Zambelli, Tomaso

    2015-12-01

    We combined scanning ion conductance microscopy (SICM) and atomic force microscopy (AFM) into a single tool using AFM cantilevers with an embedded microchannel flowing into the nanosized aperture at the apex of the hollow pyramid. An electrode was positioned in the AFM fluidic circuit connected to a second electrode in the bath. We could thus simultaneously measure the ionic current and the cantilever bending (in optical beam deflection mode). First, we quantitatively compared the SICM and AFM contact points on the approach curves. Second, we estimated where the probe in SICM mode touches the sample during scanning on a calibration grid and applied the finding to image a network of neurites on a Petri dish. Finally, we assessed the feasibility of a double controller using both the ionic current and the deflection as input signals of the piezofeedback. The experimental data were rationalized in the framework of finite elements simulations.

  3. Carbon Nanotube Atomic Force Microscopy for Proteomics and Biological Forensics

    Energy Technology Data Exchange (ETDEWEB)

    Noy, A; De Yoreo, J J; Malkin, A J

    2002-01-01

    The Human Genome Project was focused on mapping the complete genome. Yet, understanding the structure and function of the proteins expressed by the genome is the real end game. But there are approximately 100,000 proteins in the human body and the atomic structure has been determined for less than 1% of them. Given the current rate at which structures are being solved, it will take more than one hundred years to complete this task. The rate-limiting step in protein structure determination is the growth of high-quality single crystals for X-ray diffraction. Synthesis of the protein stock solution as well as X-ray diffraction and analysis can now often be done in a matter of weeks, but developing a recipe for crystallization can take years and, especially in the case of membrane proteins, is often completely unsuccessful. Consequently, techniques that can either help to elucidate the factors controlling macromolecular crystallization, increase the amount of structural information obtained from crystallized macromolecules or eliminate the need for crystallization altogether are of enormous importance. In addition, potential applications for those techniques extend well beyond the challenges of proteomics. The global spread of modern technology has brought with it an increasing threat from biological agents such as viruses. As a result, developing techniques for identifying and understanding the operation of such agents is becoming a major area of forensic research for DOE. Previous to this project, we have shown that we can use in situ atomic force microscopy (AFM) to image the surfaces of growing macromolecular crystals with molecular resolution (1-5) In addition to providing unprecedented information about macromolecular nucleation, growth and defect structure, these results allowed us to obtain low-resolution phase information for a number of macromolecules, providing structural information that was not obtainable from X-ray diffraction(3). For some virus systems

  4. Multiple membrane tethers probed by atomic force microscopy.

    Science.gov (United States)

    Sun, Mingzhai; Graham, John S; Hegedüs, Balazs; Marga, Françoise; Zhang, Ying; Forgacs, Gabor; Grandbois, Michel

    2005-12-01

    Using the atomic force microscope to locally probe the cell membrane, we observed the formation of multiple tethers (thin nanotubes, each requiring a similar pulling force) as reproducible features within force profiles recorded on individual cells. Forces obtained with Chinese hamster ovary cells, a malignant human brain tumor cell line, and human endothelial cells (EA hy926) were found to be 28 +/- 10 pN, 29 +/- 9 pN, and 29 +/- 10 pN, respectively, independent of the nature of attachment to the cantilever. The rather large variation of the tether pulling forces measured at several locations on individual cells points to the existence of heterogeneity in the membrane properties of a morphologically homogeneous cell. Measurement of the summary lengths of the simultaneously extracted tethers provides a measure of the size of the available membrane reservoir through which co-existing tethers are associated. As expected, partial disruption of the actin cytoskeleton and removal of the hyaluronan backbone of the glycocalyx were observed to result in a marked decrease (30-50%) in the magnitude and a significant sharpening of the force distribution indicating reduced heterogeneity of membrane properties. Taken together, our results demonstrate the ability of the plasma membrane to locally produce multiple interdependent tethers-a process that could play an important role in the mechanical association of cells with their environment.

  5. Imaging stability in force-feedback high-speed atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung I., E-mail: ByungKim@boisestate.edu [Department of Physics, Boise State University, 1910 University Drive Boise, ID 83725-1570, United States of America (United States); Boehm, Ryan D. [Department of Physics, Boise State University, 1910 University Drive Boise, ID 83725-1570, United States of America (United States)

    2013-02-15

    We studied the stability of force-feedback high-speed atomic force microscopy (HSAFM) by imaging soft, hard, and biological sample surfaces at various applied forces. The HSAFM images showed sudden topographic variations of streaky fringes with a negative applied force when collected on a soft hydrocarbon film grown on a grating sample, whereas they showed stable topographic features with positive applied forces. The instability of HSAFM images with the negative applied force was explained by the transition between contact and noncontact regimes in the force–distance curve. When the grating surface was cleaned, and thus hydrophilic by removing the hydrocarbon film, enhanced imaging stability was observed at both positive and negative applied forces. The higher adhesive interaction between the tip and the surface explains the improved imaging stability. The effects of imaging rate on the imaging stability were tested on an even softer adhesive Escherichia coli biofilm deposited onto the grating structure. The biofilm and planktonic cell structures in HSAFM images were reproducible within the force deviation less than ∼0.5 nN at the imaging rate up to 0.2 s per frame, suggesting that the force-feedback HSAFM was stable for various imaging speeds in imaging softer adhesive biological samples. - Highlights: ► We investigated the imaging stability of force-feedback HSAFM. ► Stable–unstable imaging transitions rely on applied force and sample hydrophilicity. ► The stable–unstable transitions are found to be independent of imaging rate.

  6. Design of cantilever probes for Atomic Force Microscopy (AFM)

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2000-01-01

    A cantilever beam used in an Atomic Force Microscope is optimized with respect to two different objectives. The first goal is to maximize the first eigenfrequency while keeping the stiffness of the probe constant. The second goal is to maximize the tip angle of the first eigenmode while again...... keeping the stiffness constant. The resulting design of the beam from the latter optimization gives almost the same result as when maximizing the first eigenfrequency. Adding a restriction on the second eigenfrequency result in a significant change of the optimal design. The beam is modelled with 12 DOF...

  7. Contrast artifacts in tapping tip atomic force microscopy

    DEFF Research Database (Denmark)

    Kyhle, Anders; Sørensen, Alexis Hammer; Zandbergen, Julie Bjerring;

    1998-01-01

    When recording images with an atomic force microscope using the resonant vibrating cantilever mode, surprising strange results are often achieved. Typical artifacts are strange contours, unexpected height shifts, and sudden changes of the apparent resolution in the acquired images. Such artifacts...... interaction. The oscillating cantilever will be in a specific swing mode according to which type of interaction is dominating, and it is the switching between these modes that is responsible for a range of artifacts observed during image acquisition. This includes the artifact often referred to as "contrast...

  8. Dual-frequency resonance-tracking atomic force microscopy

    Science.gov (United States)

    Rodriguez, Brian J.; Callahan, Clint; Kalinin, Sergei V.; Proksch, Roger

    2007-11-01

    A dual-excitation method for resonant-frequency tracking in scanning probe microscopy based on amplitude detection is developed. This method allows the cantilever to be operated at or near resonance for techniques where standard phase locked loops are not possible. This includes techniques with non-acoustic driving where the phase of the driving force is frequency and/or position dependent. An example of the latter is piezoresponse force microscopy (PFM), where the resonant frequency of the cantilever is strongly dependent on the contact stiffness of the tip-surface junction and the local mechanical properties, but the spatial variability of the drive phase rules out the use of a phase locked loop. Combined with high-voltage switching and imaging, dual-frequency, resonance-tracking PFM allows reliable studies of electromechanical and elastic properties and polarization dynamics in a broad range of inorganic and biological systems, and is illustrated using lead zirconate-titanate, rat tail collagen, and native and switched ferroelectric domains in lithium niobate.

  9. Dual-frequency resonance-tracking atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Brian J [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Callahan, Clint [Asylum Research, Santa Barbara, CA 93117 (United States); Kalinin, Sergei V [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Proksch, Roger [Asylum Research, Santa Barbara, CA 93117 (United States)

    2007-11-28

    A dual-excitation method for resonant-frequency tracking in scanning probe microscopy based on amplitude detection is developed. This method allows the cantilever to be operated at or near resonance for techniques where standard phase locked loops are not possible. This includes techniques with non-acoustic driving where the phase of the driving force is frequency and/or position dependent. An example of the latter is piezoresponse force microscopy (PFM), where the resonant frequency of the cantilever is strongly dependent on the contact stiffness of the tip-surface junction and the local mechanical properties, but the spatial variability of the drive phase rules out the use of a phase locked loop. Combined with high-voltage switching and imaging, dual-frequency, resonance-tracking PFM allows reliable studies of electromechanical and elastic properties and polarization dynamics in a broad range of inorganic and biological systems, and is illustrated using lead zirconate-titanate, rat tail collagen, and native and switched ferroelectric domains in lithium niobate.

  10. Multifunctional hydrogel nano-probes for atomic force microscopy

    Science.gov (United States)

    Lee, Jae Seol; Song, Jungki; Kim, Seong Oh; Kim, Seokbeom; Lee, Wooju; Jackman, Joshua A.; Kim, Dongchoul; Cho, Nam-Joon; Lee, Jungchul

    2016-05-01

    Since the invention of the atomic force microscope (AFM) three decades ago, there have been numerous advances in its measurement capabilities. Curiously, throughout these developments, the fundamental nature of the force-sensing probe--the key actuating element--has remained largely unchanged. It is produced by long-established microfabrication etching strategies and typically composed of silicon-based materials. Here, we report a new class of photopolymerizable hydrogel nano-probes that are produced by bottom-up fabrication with compressible replica moulding. The hydrogel probes demonstrate excellent capabilities for AFM imaging and force measurement applications while enabling programmable, multifunctional capabilities based on compositionally adjustable mechanical properties and facile encapsulation of various nanomaterials. Taken together, the simple, fast and affordable manufacturing route and multifunctional capabilities of hydrogel AFM nano-probes highlight the potential of soft matter mechanical transducers in nanotechnology applications. The fabrication scheme can also be readily utilized to prepare hydrogel cantilevers, including in parallel arrays, for nanomechanical sensor devices.

  11. Measuring the charge state of an adatom with noncontact atomic force microscopy

    NARCIS (Netherlands)

    Gross, L.; Mohn, F.; Liljeroth, P.; Repp, J.; Meyer, G.; Giessibl, F.J.

    2009-01-01

    Charge states of atoms can be investigated with scanning tunneling microscopy, but this method requires a conducting substrate. We investigated the charge-switching of individual adsorbed gold and silver atoms (adatoms) on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force micros

  12. Taking nanomedicine teaching into practice with atomic force microscopy and force spectroscopy.

    Science.gov (United States)

    Carvalho, Filomena A; Freitas, Teresa; Santos, Nuno C

    2015-12-01

    Atomic force microscopy (AFM) is a useful and powerful tool to study molecular interactions applied to nanomedicine. The aim of the present study was to implement a hands-on atomic AFM course for graduated biosciences and medical students. The course comprises two distinct practical sessions, where students get in touch with the use of an atomic force microscope by performing AFM scanning images of human blood cells and force spectroscopy measurements of the fibrinogen-platelet interaction. Since the beginning of this course, in 2008, the overall rating by the students was 4.7 (out of 5), meaning a good to excellent evaluation. Students were very enthusiastic and produced high-quality AFM images and force spectroscopy data. The implementation of the hands-on AFM course was a success, giving to the students the opportunity of contact with a technique that has a wide variety of applications on the nanomedicine field. In the near future, nanomedicine will have remarkable implications in medicine regarding the definition, diagnosis, and treatment of different diseases. AFM enables students to observe single molecule interactions, enabling the understanding of molecular mechanisms of different physiological and pathological processes at the nanoscale level. Therefore, the introduction of nanomedicine courses in bioscience and medical school curricula is essential.

  13. Synchronizing atomic force microscopy force mode and fluorescence microscopy in real time for immune cell stimulation and activation studies

    Energy Technology Data Exchange (ETDEWEB)

    Cazaux, Séverine; Sadoun, Anaïs; Biarnes-Pelicot, Martine; Martinez, Manuel; Obeid, Sameh [Aix Marseille Université, LAI UM 61, Marseille F-13288 (France); Inserm, UMR-S 1067, Marseille F-13288 (France); CNRS, UMR 7333, Marseille F-13288 (France); Bongrand, Pierre [Aix Marseille Université, LAI UM 61, Marseille F-13288 (France); Inserm, UMR-S 1067, Marseille F-13288 (France); CNRS, UMR 7333, Marseille F-13288 (France); APHM, Hôpital de la Conception, Laboratoire d’Immunologie, Marseille F-13385 (France); Limozin, Laurent [Aix Marseille Université, LAI UM 61, Marseille F-13288 (France); Inserm, UMR-S 1067, Marseille F-13288 (France); CNRS, UMR 7333, Marseille F-13288 (France); Puech, Pierre-Henri, E-mail: pierre-henri.puech@inserm.fr [Aix Marseille Université, LAI UM 61, Marseille F-13288 (France); Inserm, UMR-S 1067, Marseille F-13288 (France); CNRS, UMR 7333, Marseille F-13288 (France)

    2016-01-15

    A method is presented for combining atomic force microscopy (AFM) force mode and fluorescence microscopy in order to (a) mechanically stimulate immune cells while recording the subsequent activation under the form of calcium pulses, and (b) observe the mechanical response of a cell upon photoactivation of a small G protein, namely Rac. Using commercial set-ups and a robust signal coupling the fluorescence excitation light and the cantilever bending, the applied force and activation signals were very easily synchronized. This approach allows to control the entire mechanical history of a single cell up to its activation and response down to a few hundreds of milliseconds, and can be extended with very minimal adaptations to other cellular systems where mechanotransduction is studied, using either purely mechanical stimuli or via a surface bound specific ligand. - Highlights: • A signal coupling AFM and fluorescence microscopy was characterized for soft cantilevers. • It can be used as an intrinsic timer to synchronize images and forces. • Mechanical stimulation of single immune cells while recording calcium fluxes was detailed. • Light-induced mechanical modifications of lymphocytes using a PA-Rac protein were demonstrated. • The precautions and limitations of use of this effect were presented.

  14. Brown algal morphogenesis: Atomic Force Microscopy as a tool to study the role of mechanical forces

    Directory of Open Access Journals (Sweden)

    Benoit eTesson

    2014-09-01

    Full Text Available Over the last few years, a growing interest has been directed toward the use of macroalgae as a source of energy, food and molecules for the cosmetic and pharmaceutical industries. Besides this, macroalgal development remains poorly understood compared to other multicellular organisms. Brown algae (Phaeophyceae form a monophyletic lineage of usually large multicellular algae which evolved independently from land plants. In their environment, they are subjected to strong mechanical forces (current, waves and tide, in response to which they modify rapidly and reversibly their morphology. Because of their specific cellular features (cell wall composition, cytoskeleton organization, deciphering how they cope with these forces might help discover new control mechanisms of cell wall softening and cellulose synthesis. Despite the current scarcity in knowledge on brown algal cell wall dynamics and protein composition, we will illustrate, in the light of methods adapted to Ectocarpus siliculosus, to what extent atomic force microscopy can contribute to advance this field of investigation.

  15. Wettability and surface forces measured by atomic force microscopy: the role of roughness

    Science.gov (United States)

    Gavoille, J.; Takadoum, J.; Martin, N.; Durand, D.

    2009-10-01

    Thin films of titanium, copper and silver with various roughnesses were prepared by physical vapour deposition technique: dc magnetron sputtering. By varying the deposition time from few minutes to one hour it was possible to obtain metallic films with surface roughness average ranging from 1 to 20 nm. The wettability of these films was studied by measuring the contact angle using the sessile drop method and surface forces were investigated using the atomic force microscopy (AFM) by measuring the pull-off force between the AFM tip and the surfaces. Experimental results have been mainly discussed in terms of metal surface reactivity, Young modulus of the materials and real surface of contact between the AFM tip and the film surfaces.

  16. Intermolecular forces between acetylcholine and acetylcholinesterases studied with atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    张英鸽; 白春礼; 王琛; 赵德禄; 苏明; 林璋; 田芳

    1999-01-01

    With the aid of atomic force microscopy, the intermolecular forces between acetyleholinesterases (AChE) and its natural substrate acetylcholine (ACh) have been studied. Through force spectrum measurement based on imaging of AChE molecules it was found that the attraction force between individual molecule pairs of ACh and AChE was (10±1) pN just before the quaternary ammonium head of ACh got into contact with the negative end of AChE and the decaying distance of attraction was (4±1) nm from the surface of ACHE. The adhesion force between individual ACh and AChE molecule pairs was (25±2) pN, which had a decaying feature of fast-slow-fast (FSF). The attraction forces between AChE and choline (Ch), the quaternary ammonium moiety and hydrolysate of ACh molecule, were similar to those between AChE and ACh. The adhesion forces between AChE and Ch were (20±2) pN, a little weaker than that between ACh and ACHE. These results indicated that AChE had a steering role for the diffusion of ACh toward it and had r

  17. Resonance frequency-retuned quartz tuning fork as a force sensor for noncontact atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ooe, Hiroaki; Sakuishi, Tatsuya; Arai, Toyoko, E-mail: arai@staff.kanazawa-u.ac.jp [Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192 (Japan); Nogami, Makoto; Tomitori, Masahiko [Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-1292 (Japan)

    2014-07-28

    Based on a two-prong type quartz tuning fork, a force sensor with a high Q factor, which we call a retuned fork sensor, was developed for non-contact atomic force microscopy (nc-AFM) with atomic resolution. By cutting a small notch and attaching an AFM tip to one prong, its resonance frequency can be retuned to that of the other intact prong. In balancing the two prongs in this manner, a high Q factor (>50 000 in ultrahigh vacuum) is obtained for the sensor. An atomic resolution image of the Si(111)-7 × 7 surface was demonstrated using an nc-AFM with the sensor. The dependence of the Q factor on resonance frequency of the sensor and the long-range force between tip and sample were measured and analyzed in view of the various dissipation channels. Dissipation in the signal detection circuit turned out to be mainly limited by the total Q factor of the nc-AFM system.

  18. Graphene on SiC(0001 inspected by dynamic atomic force microscopy at room temperature

    Directory of Open Access Journals (Sweden)

    Mykola Telychko

    2015-04-01

    Full Text Available We investigated single-layer graphene on SiC(0001 by atomic force and tunneling current microscopy, to separate the topographic and electronic contributions from the overall landscape. The analysis revealed that the roughness evaluated from the atomic force maps is very low, in accord with theoretical simulations. We also observed that characteristic electron scattering effects on graphene edges and defects are not accompanied by any out-of-plane relaxations of carbon atoms.

  19. Engineering and Characterization of Collagen Networks Using Wet Atomic Force Microscopy and Environmental Scanning Electron Microscopy

    Science.gov (United States)

    Osborn, Jenna; Coffey, Tonya; Conrad, Brad; Burris, Jennifer; Hester, Brooke

    2014-03-01

    Collagen is an abundant protein and its monomers covalently crosslink to form fibrils which form fibers which contribute to forming macrostructures like tendon or bone. While the contribution is well understood at the macroscopic level, it is not well known at the fibril level. We wish to study the mechanical properties of collagen for networks of collagen fibers that vary in size and density. We present here a method to synthesize collagen networks from monomers and that allows us to vary the density of the networks. By using biotynilated collagen and a surface that is functionalized with avidin, we generate two-dimensional collagen networks across the surface of a silicon wafer. During network synthesis, the incubation time is varied from 30 minutes to 3 hours or temperature is varied from 25°C to 45°C. The two-dimensional collagen network created in the process is characterized using environmental atomic force microscopy (AFM) and scanning electron microscopy (SEM). The network density is measured by the number of strands in one frame using SPIP software. We expect that at body temperature (37°C) and with longer incubation times, the network density should increase.

  20. Atomic force microscopy and force spectroscopy on the assessment of protein folding and functionality.

    Science.gov (United States)

    Carvalho, Filomena A; Martins, Ivo C; Santos, Nuno C

    2013-03-01

    Atomic force microscopy (AFM) applied to biological systems can, besides generating high-quality and well-resolved images, be employed to study protein folding via AFM-based force spectroscopy. This approach allowed remarkable advances in the measurement of inter- and intramolecular interaction forces with piconewton resolution. The detection of specific interaction forces between molecules based on the AFM sensitivity and the manipulation of individual molecules greatly advanced the understanding of intra-protein and protein-ligand interactions. Apart from the academic interest in the resolution of basic scientific questions, this technique has also key importance on the clarification of several biological questions of immediate biomedical relevance. Force spectroscopy is an especially appropriate technique for "mechanical proteins" that can provide crucial information on single protein molecules and/or domains. Importantly, it also has the potential of combining in a single experiment spatial and kinetic measurements. Here, the main principles of this methodology are described, after which the ability to measure interactions at the single-molecule level is discussed, in the context of relevant protein-folding examples. We intend to demonstrate the potential of AFM-based force spectroscopy in the study of protein folding, especially since this technique is able to circumvent some of the difficulties typically encountered in classical thermal/chemical denaturation studies.

  1. Nano Scale Mechanical Analysis of Biomaterials Using Atomic Force Microscopy

    Science.gov (United States)

    Dutta, Diganta

    The atomic force microscope (AFM) is a probe-based microscope that uses nanoscale and structural imaging where high resolution is desired. AFM has also been used in mechanical, electrical, and thermal engineering applications. This unique technique provides vital local material properties like the modulus of elasticity, hardness, surface potential, Hamaker constant, and the surface charge density from force versus displacement curve. Therefore, AFM was used to measure both the diameter and mechanical properties of the collagen nanostraws in human costal cartilage. Human costal cartilage forms a bridge between the sternum and bony ribs. The chest wall of some humans is deformed due to defective costal cartilage. However, costal cartilage is less studied compared to load bearing cartilage. Results show that there is a difference between chemical fixation and non-chemical fixation treatments. Our findings imply that the patients' chest wall is mechanically weak and protein deposition is abnormal. This may impact the nanostraws' ability to facilitate fluid flow between the ribs and the sternum. At present, AFM is the only tool for imaging cells' ultra-structure at the nanometer scale because cells are not homogeneous. The first layer of the cell is called the cell membrane, and the layer under it is made of the cytoskeleton. Cancerous cells are different from normal cells in term of cell growth, mechanical properties, and ultra-structure. Here, force is measured with very high sensitivity and this is accomplished with highly sensitive probes such as a nano-probe. We performed experiments to determine ultra-structural differences that emerge when such cancerous cells are subject to treatments such as with drugs and electric pulses. Jurkat cells are cancerous cells. These cells were pulsed at different conditions. Pulsed and non-pulsed Jurkat cell ultra-structures were investigated at the nano meter scale using AFM. Jurkat cell mechanical properties were measured under

  2. Autopilot for frequency-modulation atomic force microscopy

    Science.gov (United States)

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri

    2015-10-01

    One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

  3. Autopilot for frequency-modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri, E-mail: phsivan@tx.technion.ac.il [Department of Physics and the Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

    2015-10-15

    One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

  4. Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy

    Science.gov (United States)

    Balke, Nina; Jesse, Stephen; Carmichael, Ben; Baris Okatan, M.; Kravchenko, Ivan I.; Kalinin, Sergei V.; Tselev, Alexander

    2017-02-01

    Atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm-1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.

  5. Localization and force analysis at the single virus particle level using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chih-Hao [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Horng, Jim-Tong [Department of Biochemistry, Chang Gung University, 259 Wen-Hwa First Road, Kweishan, Taoyuan 333, Taiwan (China); Chang, Jeng-Shian [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Hsieh, Chung-Fan [Graduate Institute of Biomedical Sciences, Chang Gung University, Kweishan, Taoyuan 333, Taiwan (China); Tseng, You-Chen [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Lin, Shiming, E-mail: til@ntu.edu.tw [Institute of Applied Mechanics, Nation Taiwan University, Roosevelt Road, Taipei 10617, Taiwan (China); Center for Optoelectronic Biomedicine, College of Medicine, Nation Taiwan University, 1-1 Jen-Ai Road, Taipei 10051, Taiwan (China)

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer Localization of single virus particle. Black-Right-Pointing-Pointer Force measurements. Black-Right-Pointing-Pointer Force mapping. -- Abstract: Atomic force microscopy (AFM) is a vital instrument in nanobiotechnology. In this study, we developed a method that enables AFM to simultaneously measure specific unbinding force and map the viral glycoprotein at the single virus particle level. The average diameter of virus particles from AFM images and the specificity between the viral surface antigen and antibody probe were integrated to design a three-stage method that sets the measuring area to a single virus particle before obtaining the force measurements, where the influenza virus was used as the object of measurements. Based on the purposed method and performed analysis, several findings can be derived from the results. The mean unbinding force of a single virus particle can be quantified, and no significant difference exists in this value among virus particles. Furthermore, the repeatability of the proposed method is demonstrated. The force mapping images reveal that the distributions of surface viral antigens recognized by antibody probe were dispersed on the whole surface of individual virus particles under the proposed method and experimental criteria; meanwhile, the binding probabilities are similar among particles. This approach can be easily applied to most AFM systems without specific components or configurations. These results help understand the force-based analysis at the single virus particle level, and therefore, can reinforce the capability of AFM to investigate a specific type of viral surface protein and its distributions.

  6. Atomic scale imaging of hydroxyapatite and brushite in air by force microscopy

    Science.gov (United States)

    Siperko, Lorraine M.; Landis, William J.

    1992-11-01

    A method for obtaining atomic scale images of powder samples by force microscopy has been used to determine surface structures of hydroxyapatite and brushite. From isolated hydroxyapatite crystal clusters, two crystal planes have been identified. The and spacings obtained agree well with published crystallographic values. Groups of brushite platelets yielded atomic spacings which are presumed to be those of the crystal plane.

  7. Force-gradient-induced mechanical dissipation of quartz tuning fork force sensors used in atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Castellanos-Gomez, A. [Departamento de Fisica de la Materia Condensada (C-III), Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Agrait, N. [Departamento de Fisica de la Materia Condensada (C-III), Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Instituto Universitario de Ciencia de Materiales ' Nicolas Cabrera' , Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Instituto Madrileno de Estudios Avanzados en Nanociencia, IMDEA-Nanociencia, 28049 Madrid (Spain); Rubio-Bollinger, G., E-mail: gabino.rubio@uam.es [Departamento de Fisica de la Materia Condensada (C-III), Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Instituto Universitario de Ciencia de Materiales ' Nicolas Cabrera' , Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain)

    2011-02-15

    We have studied the dynamics of quartz tuning fork resonators used in atomic force microscopy taking into account the mechanical energy dissipation through the attachment of the tuning fork base. We find that the tuning fork resonator quality factor changes even in the case of a purely elastic sensor-sample interaction. This is due to the effective mechanical imbalance of the tuning fork prongs induced by the sensor-sample force gradient, which in turn has an impact on dissipation through the attachment of the resonator base. This effect may yield a measured dissipation signal that can be different from the one exclusively related to the dissipation between the sensor and the sample. We also find that there is a second-order term in addition to the linear relationship between the sensor-sample force gradient and the resonance frequency shift of the tuning fork that is significant even for force gradients usually present in atomic force microscopy, which are in the range of tens of N/m. -- Research Highlights: {yields} Dynamics of miniature tuning fork force sensors: a mechanical model. {yields} Non-linear relationship between resonance frequency shift and applied force gradient. {yields} An apparent mechanical dissipation channel opens even for purely conservative tip-sample interactions. {yields} qPlus tuning forks configuration has lower Q factor but straightforward dynamics.

  8. Direct force measurement of single DNA-peptide interactions using atomic force microscopy.

    Science.gov (United States)

    Chung, Ji W; Shin, Dongjin; Kwak, June M; Seog, Joonil

    2013-06-01

    The selective interactions between DNA and miniature (39 residues) engineered peptide were directly measured at the single-molecule level by using atomic force microscopy. This peptide (p007) contains an α-helical recognition site similar to leucine zipper GCN4 and specifically recognizes the ATGAC sequence in the DNA with nanomolar affinity. The average rupture force was 42.1 pN, which is similar to the unbinding forces of the digoxigenin-antidigoxigenin complex, one of the strongest interactions in biological systems. The single linear fit of the rupture forces versus the logarithm of pulling rates showed a single energy barrier with a transition state located at 0.74 nm from the bound state. The smaller koff compared with that of other similar systems was presumably due to the increased stability of the helical structure by putative folding residues in p007. This strong sequence-specific DNA-peptide interaction has a potential to be utilized to prepare well-defined mechanically stable DNA-protein hybrid nanostructures.

  9. Structural Evidence for α-Synuclein Fibrils Using in Situ Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    Feng ZHANG; Li-Na JI; Lin TANG; Jun HU; Hong-Yu HU; Hong-Jie XU; Jian-Hua HE

    2005-01-01

    Human α-synuclein is a presynaptic terminal protein and can form insoluble fibrils that are believed to play an important role in the pathogenesis of several neurodegenerafive diseases such as Parkinson's disease, dementia with Lewy bodies and Lewy body variant of Alzheimer's disease. In this paper, in situ atomic force microscopy has been used to study the structural properties of α-synuclein fibrils in solution using two different atomic force microscopy imaging modes: tapping mode and contact mode. In the in situ contact mode atomic force microscopy experiments α-synuclein fibrils quickly broke into fragments, and a similar phenomenon was found using tapping mode atomic force microscopy in which α-synuclein fibrils were incubated with guanidine hydrochloride (0.6 M). The α-synuclein fibrils kept their original filamentous topography for over 1 h in the in situ tapping mode atomic force microscopy experiments. The present results provide indirect evidence on how β-sheets assemble into α-synuclein fibrils on a nanometer scale.

  10. Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces

    Directory of Open Access Journals (Sweden)

    Adam Sweetman

    2014-04-01

    Full Text Available In principle, non-contact atomic force microscopy (NC-AFM now readily allows for the measurement of forces with sub-nanonewton precision on the atomic scale. In practice, however, the extraction of the often desired ‘short-range’ force from the experimental observable (frequency shift is often far from trivial. In most cases there is a significant contribution to the total tip–sample force due to non-site-specific van der Waals and electrostatic forces. Typically, the contribution from these forces must be removed before the results of the experiment can be successfully interpreted, often by comparison to density functional theory calculations. In this paper we compare the ‘on-minus-off’ method for extracting site-specific forces to a commonly used extrapolation method modelling the long-range forces using a simple power law. By examining the behaviour of the fitting method in the case of two radically different interaction potentials we show that significant uncertainties in the final extracted forces may result from use of the extrapolation method.

  11. Nanocharacterization of bio-silica using atomic force and ultrasonic force microscopy

    Science.gov (United States)

    Gill, Vinaypreet S.; Hallinan, Kevin P.; Brar, N. S.

    2005-04-01

    Nanotechnology has become central to our research efforts to fabricate relatively smaller size devices, which are more versatile than their older and larger predecessors. Silica is a very important material in this regard. Recently, a new biomimetically inspired path to silica production has been demonstrated. This processing technique was inspired from biological organisms, such as marine diatoms, which produce silica at ambient conditions and almost neutral ph with beautiful control over location and structure. Recently, several researchers have demonstrated that positional control of silica formed could be achieved by application of an electric field to locate charged enzymes responsible for the bio catalytic condensation of silica from solution. Secondly, chemical and physical controls of silica structural morphology were achievable. Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) techniques are employed for the first time to provide both substantially improved resolution of the morphology and relative measurement of the modulus of elasticity of the structures. In particular, these measurements reveal the positive impact of a shear flow field present during the silica formation on both the "ordering" of the structure and the mechanical properties.

  12. Spatial spectrograms of vibrating atomic force microscopy cantilevers coupled to sample surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, Ryan; Raman, Arvind, E-mail: raman@purdue.edu [Birck Nanotechnology Center, 1205 W. State Street, Purdue University, West Lafayette, Indiana 47907 (United States); Proksch, Roger, E-mail: Roger.Proksch@oxinst.com [Asylum Research, 6310 Hollister Ave., Santa Barbara, California 93117 (United States)

    2013-12-23

    Many advanced dynamic Atomic Force Microscopy (AFM) techniques such as contact resonance, force modulation, piezoresponse force microscopy, electrochemical strain microscopy, and AFM infrared spectroscopy exploit the dynamic response of a cantilever in contact with a sample to extract local material properties. Achieving quantitative results in these techniques usually requires the assumption of a certain shape of cantilever vibration. We present a technique that allows in-situ measurements of the vibrational shape of AFM cantilevers coupled to surfaces. This technique opens up unique approaches to nanoscale material property mapping, which are not possible with single point measurements alone.

  13. Contact force identification using the subharmonic resonance of a contact-mode atomic force microscopy.

    Science.gov (United States)

    Abdel-Rahman, Eihab M; Nayfeh, Ali H

    2005-02-01

    We propose a step-by-step experimental procedure for characterization of the nonlinear contact stiffness on surfaces using contact-mode atomic force microscopy. Our approach directly estimates the first-, second-, and third-order coefficients of the contact stiffness. It neither uses nor requires the underlying assumptions of the Hertzian contact theory. We use a primary resonance excitation of the probe to estimate the linear coefficient of the contact stiffness. We use the method of multiple scales to obtain closed-form expressions approximating the response of the probe to a subharmonic resonance excitation of order one-half. We utilize these expressions and higher-order spectral measurements to independently estimate the quadratic and cubic coefficients of the contact stiffness.

  14. Quantitative assessment of contact and non-contact lateral force calibration methods for atomic force microscopy.

    Science.gov (United States)

    Tran Khac, Bien Cuong; Chung, Koo-Hyun

    2016-02-01

    Atomic Force Microscopy (AFM) has been widely used for measuring friction force at the nano-scale. However, one of the key challenges faced by AFM researchers is to calibrate an AFM system to interpret a lateral force signal as a quantifiable force. In this study, five rectangular cantilevers were used to quantitatively compare three different lateral force calibration methods to demonstrate the legitimacy and to establish confidence in the quantitative integrity of the proposed methods. The Flat-Wedge method is based on a variation of the lateral output on a surface with flat and changing slopes, the Multi-Load Pivot method is based on taking pivot measurements at several locations along the cantilever length, and the Lateral AFM Thermal-Sader method is based on determining the optical lever sensitivity from the thermal noise spectrum of the first torsional mode with a known torsional spring constant from the Sader method. The results of the calibration using the Flat-Wedge and Multi-Load Pivot methods were found to be consistent within experimental uncertainties, and the experimental uncertainties of the two methods were found to be less than 15%. However, the lateral force sensitivity determined by the Lateral AFM Thermal-Sader method was found to be 8-29% smaller than those obtained from the other two methods. This discrepancy decreased to 3-19% when the torsional mode correction factor for an ideal cantilever was used, which suggests that the torsional mode correction should be taken into account to establish confidence in Lateral AFM Thermal-Sader method.

  15. An Undergraduate Nanotechnology Engineering Laboratory Course on Atomic Force Microscopy

    Science.gov (United States)

    Russo, D.; Fagan, R. D.; Hesjedal, T.

    2011-01-01

    The University of Waterloo, Waterloo, ON, Canada, is home to North America's first undergraduate program in nanotechnology. As part of the Nanotechnology Engineering degree program, a scanning probe microscopy (SPM)-based laboratory has been developed for students in their fourth year. The one-term laboratory course "Nanoprobing and…

  16. Height drift correction in non-raster atomic force microscopy

    NARCIS (Netherlands)

    Meyer, Travis R.; Ziegler, Dominik; Brune, Christoph; Chen, Alex; Farnham, Rodrigo; Huynh, Nen; Chang, Jen-Mei; Bertozzi, Andrea L.; Ashby, Paul D.

    2014-01-01

    We propose a novel method to detect and correct drift in non-raster scanning probe microscopy. In conventional raster scanning drift is usually corrected by subtracting a fitted polynomial from each scan line, but sample tilt or large topographic features can result in severe artifacts. Our method u

  17. An Undergraduate Nanotechnology Engineering Laboratory Course on Atomic Force Microscopy

    Science.gov (United States)

    Russo, D.; Fagan, R. D.; Hesjedal, T.

    2011-01-01

    The University of Waterloo, Waterloo, ON, Canada, is home to North America's first undergraduate program in nanotechnology. As part of the Nanotechnology Engineering degree program, a scanning probe microscopy (SPM)-based laboratory has been developed for students in their fourth year. The one-term laboratory course "Nanoprobing and Lithography"…

  18. Atomic force microscopy as a tool for the investigation of living cells.

    Science.gov (United States)

    Morkvėnaitė-Vilkončienė, Inga; Ramanavičienė, Almira; Ramanavičius, Arūnas

    2013-01-01

    Atomic force microscopy is a valuable and useful tool for the imaging and investigation of living cells in their natural environment at high resolution. Procedures applied to living cell preparation before measurements should be adapted individually for different kinds of cells and for the desired measurement technique. Different ways of cell immobilization, such as chemical fixation on the surface, entrapment in the pores of a membrane, or growing them directly on glass cover slips or on plastic substrates, result in the distortion or appearance of artifacts in atomic force microscopy images. Cell fixation allows the multiple use of samples and storage for a prolonged period; it also increases the resolution of imaging. Different atomic force microscopy modes are used for the imaging and analysis of living cells. The contact mode is the best for cell imaging because of high resolution, but it is usually based on the following: (i) image formation at low interaction force, (ii) low scanning speed, and (iii) usage of "soft," low resolution cantilevers. The tapping mode allows a cell to behave like a very solid material, and destructive shear forces are minimized, but imaging in liquid is difficult. The force spectroscopy mode is used for measuring the mechanical properties of cells; however, obtained results strongly depend on the cell fixation method. In this paper, the application of 3 atomic force microscopy modes including (i) contact, (ii) tapping, and (iii) force spectroscopy for the investigation of cells is described. The possibilities of cell preparation for the measurements, imaging, and determination of mechanical properties of cells are provided. The applicability of atomic force microscopy to diagnostics and other biomedical purposes is discussed.

  19. Noncontact atomic force microscopy in liquid environment with quartz tuning fork and carbon nanotube probe

    DEFF Research Database (Denmark)

    Kageshima, M.; Jensenius, Henriette; Dienwiebel, M.

    2002-01-01

    A force sensor for noncontact atomic force microscopy in liquid environment was developed by combining a multiwalled carbon nanotube (MWNT) probe with a quartz tuning fork. Solvation shells of octamethylcyclotetrasiloxane surface were detected both in the frequency shift and dissipation. Due...... to the high aspect ratio of the CNT probe, the long-range background force was barely detectable in the solvation region. (C) 2002 Elsevier Science B.V. All rights reserved....

  20. Atomic Force Microscopy Studies on The Surface Morphologies of Chemical Bath Deposited Cus Thin Films

    Directory of Open Access Journals (Sweden)

    Ho Soonmin

    2016-06-01

    Full Text Available In this work, copper sulphide thin films were deposited onto microscope glass slide by chemical bath deposition technique. The tartaric acid was served as complexing agent to chelate with Cu2+ to obtain complex solution. The influence of pH value on the surface morphologies of the films has been particularly investigated using the atomic force microscopy technique. The atomic force microscopy results indicate that the CuS films deposited at pH 1 were uniform, compact and pinhole free. However, the incomplete surface coverage observed for the films prepared at high pH (pH 2 and 2.5 values.

  1. Adhesive properties of Staphylococcus epidermidis probed by atomic force microscopy

    DEFF Research Database (Denmark)

    Hu, Yifan; Ulstrup, Jens; Zhang, Jingdong;

    2011-01-01

    Mapping of the surface properties of Staphylococcus epidermidis and of biofilm forming bacteria in general is a key to understand their functions, particularly their adhesive properties. To gain a comprehensive view of the structural and chemical properties of S. epidermidis, four different strains...... are not the driving forces for adhesion of the four strains. Rather, the observation of sawtooth force–distance patterns on the surface of biofilm positive strains documents the presence of modular proteins such as Aap that may mediate cell adhesion. Treatment of two biofilm positive strains with two chemical...

  2. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    Science.gov (United States)

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-12-01

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  3. Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

    Science.gov (United States)

    Kroeger, Marie E.; Sorenson, Blaire A.; Thomas, J. Santoro; Stojković, Emina A.; Tsonchev, Stefan; Nicholson, Kenneth T.

    2014-01-01

    Atomic force microscopy (AFM) uses a pyramidal tip attached to a cantilever to probe the force response of a surface. The deflections of the tip can be measured to ~10 pN by a laser and sectored detector, which can be converted to image topography. Amplitude modulation or “tapping mode” AFM involves the probe making intermittent contact with the surface while oscillating at its resonant frequency to produce an image. Used in conjunction with a fluid cell, tapping-mode AFM enables the imaging of biological macromolecules such as proteins in physiologically relevant conditions. Tapping-mode AFM requires manual tuning of the probe and frequent adjustments of a multitude of scanning parameters which can be challenging for inexperienced users. To obtain high-quality images, these adjustments are the most time consuming. PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) produces an image by measuring a force response curve for every point of contact with the sample. With ScanAsyst software, PF-QNM can be automated. This software adjusts the set-point, drive frequency, scan rate, gains, and other important scanning parameters automatically for a given sample. Not only does this process protect both fragile probes and samples, it significantly reduces the time required to obtain high resolution images. PF-QNM is compatible for AFM imaging in fluid; therefore, it has extensive application for imaging biologically relevant materials. The method presented in this paper describes the application of PF-QNM to obtain images of a bacterial red-light photoreceptor, RpBphP3 (P3), from photosynthetic R. palustris in its light-adapted state. Using this method, individual protein dimers of P3 and aggregates of dimers have been observed on a mica surface in the presence of an imaging buffer. With appropriate adjustments to surface and/or solution concentration, this method may be generally applied to other biologically relevant macromolecules and soft materials. PMID

  4. Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

    Science.gov (United States)

    Balke, Nina; Jesse, Stephen; Yu, Pu; Carmichael, Ben; Kalinin, Sergei V.; Tselev, Alexander

    2016-10-01

    Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ˜1-3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip-sample contact stiffness. The approach has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. This analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.

  5. Theoretical Models for Surface Forces and Adhesion and Their Measurement Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Osvaldo N. Oliveira

    2012-10-01

    Full Text Available The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS, it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of afs, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution.

  6. Theoretical models for surface forces and adhesion and their measurement using atomic force microscopy.

    Science.gov (United States)

    Leite, Fabio L; Bueno, Carolina C; Da Róz, Alessandra L; Ziemath, Ervino C; Oliveira, Osvaldo N

    2012-10-08

    The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of afs, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution.

  7. Note: Artificial neural networks for the automated analysis of force map data in atomic force microscopy

    Science.gov (United States)

    Braunsmann, Christoph; Schäffer, Tilman E.

    2014-05-01

    Force curves recorded with the atomic force microscope on structured samples often show an irregular force versus indentation behavior. An analysis of such curves using standard contact models (e.g., the Sneddon model) would generate inaccurate Young's moduli. A critical inspection of the force curve shape is therefore necessary for estimating the reliability of the generated Young's modulus. We used a trained artificial neural network to automatically recognize curves of "good" and of "bad" quality. This is especially useful for improving the analysis of force maps that consist of a large number of force curves.

  8. Measuring cell adhesion forces of primary gastrulating cells from zebrafish using atomic force microscopy.

    Science.gov (United States)

    Puech, Pierre-Henri; Taubenberger, Anna; Ulrich, Florian; Krieg, Michael; Muller, Daniel J; Heisenberg, Carl-Philipp

    2005-09-15

    During vertebrate gastrulation, progenitor cells of different germ layers acquire specific adhesive properties that contribute to germ layer formation and separation. Wnt signals have been suggested to function in this process by modulating the different levels of adhesion between the germ layers, however, direct evidence for this is still lacking. Here we show that Wnt11, a key signal regulating gastrulation movements, is needed for the adhesion of zebrafish mesendodermal progenitor cells to fibronectin, an abundant extracellular matrix component during gastrulation. To measure this effect, we developed an assay to quantify the adhesion of single zebrafish primary mesendodermal progenitors using atomic-force microscopy (AFM). We observed significant differences in detachment force and work between cultured mesendodermal progenitors from wild-type embryos and from slb/wnt11 mutant embryos, which carry a loss-of-function mutation in the wnt11 gene, when tested on fibronectin-coated substrates. These differences were probably due to reduced adhesion to the fibronectin substrate as neither the overall cell morphology nor the cell elasticity grossly differed between wild-type and mutant cells. Furthermore, in the presence of inhibitors of fibronectin-integrin binding, such as RGD peptides, the adhesion force and work were strongly decreased, indicating that integrins are involved in the binding of mesendodermal progenitors in our assay. These findings demonstrate that AFM can be used to quantitatively determine the substrate-adhesion of cultured primary gastrulating cells and provide insight into the role of Wnt11 signalling in modulating cell adhesion at the single cell scale.

  9. Mapping cellular magnesium using X-ray microfluorescence and atomic force microscopy

    OpenAIRE

    2010-01-01

    Magnesium is the most abundant intracellular divalent cation. We present an innovative experimental approach to localizing intracellular magnesium that combines elemental and morphological information from individual cells with high-resolution spatial information. Integration of information from scanning fluorescence X-ray microscopy with information from atomic force microscopy was used to generate a magnesium concentration map and to determine the X-ray linear absorption coefficient map wit...

  10. Microcontroller-driven fluid-injection system for atomic force microscopy.

    Science.gov (United States)

    Kasas, S; Alonso, L; Jacquet, P; Adamcik, J; Haeberli, C; Dietler, G

    2010-01-01

    We present a programmable microcontroller-driven injection system for the exchange of imaging medium during atomic force microscopy. Using this low-noise system, high-resolution imaging can be performed during this process of injection without disturbance. This latter circumstance was exemplified by the online imaging of conformational changes in DNA molecules during the injection of anticancer drug into the fluid chamber.

  11. Quantification of tip-broadening in non-contact atomic force microscopy with carbon nanotube tips

    DEFF Research Database (Denmark)

    Meinander, Kristoffer; Jensen, Thomas N.; Simonsen, Soren B.

    2012-01-01

    Carbon nanotube terminated atomic force microscopy (AFM) probes have been used for the imaging of 5 nm wide surface supported Pt nanoclusters by non-contact (dynamic mode) AFM in an ultra-high vacuum. The results are compared to AFM measurements done with conventional Si-tips, as well...

  12. Use of atomic force microscopy to quantify slip irreversibility in a nickel-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Risbet, M.; Feaugas, X.; Guillemer-Neel, C.; Clavel, M

    2003-09-15

    Atomic force microscopy was used to study the evolution of surface deformation during cyclic loading in a nickel-base superalloy. Cyclic slip irreversibility has been investigated using quantitative evaluation of extrusion heights and inter-band spacing. This approach is applied to formulate a microscopic crack initiation law, compared to a classical Manson-Coffin relationship.

  13. Calculation of Intracellular Pressure of Red Blood Cells at Jaundice According to Atomic Force Microscopy Data

    Directory of Open Access Journals (Sweden)

    Yu.S. Nagornov

    2016-03-01

    Full Text Available The present work is devoted to the analysis of three-dimensional data of atomic force microscopy for research of the morphology of red blood cells. In this paper we built a biomechanical model of the erythrocyte, which allowed calculating the intracellular pressure of erythrocyte based on data of atomic force microscopy. As a result, we obtained the dependence intracellular pressure on the morphology of red blood cell. We have proposed a method of estimating of intracellular pressure of erythrocytes based on numerical modeling and data of atomic force microscopy of erythrocytes scan, which involves a comparison of the experimental data with the results of numerical calculation. The method is applied to the data of atomic force microscopy of erythrocytes of experimental animals - dwarf domestic pigs with different degrees of obstructive jaundice and normal. It is shown that with increasing severity of the disease and the concentration of bilirubin in the blood there is an infringement erythrocyte membranes, by an average increasing their volume and intracellular pressure.

  14. Imaging organophosphate and pyrophosphate sequestration on brucite by in situ atomic force microscopy

    NARCIS (Netherlands)

    Wang, Lijun; Putnis, Christine V; King, Helen E; Hövelmann, Jörn; Ruiz-Agudo, Encarnación; Putnis, Andrew

    2016-01-01

    In order to evaluate the organic phosphorus (OP) and pyrophosphate (PyroP) cycle and their fate in the environment, it is critical to understand the effects of mineral interfaces on the reactivity of adsorption and precipitation of OP and PyroP. Here, in situ atomic force microscopy (AFM) is used to

  15. Dynamics of a Disturbed Sessile Drop Measured by Atomic Force Microscopy (AFM)

    NARCIS (Netherlands)

    McGuiggan, Patricia M.; Grave, Daniel A.; Wallace, Jay S.; Cheng, Shengfeng; Prosperetti, Andrea; Robbins, Mark O.

    2011-01-01

    A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r 20–30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liq

  16. Conductivity mapping of nanoparticles by torsional resonance tunneling atomic force microscopy

    NARCIS (Netherlands)

    Prastani, C; Vetushka, A.; Fejfar, A.; Nanu, M.; Nanu, D.; Rath, J.K.; Schropp, R.E.I.

    2012-01-01

    In this paper, torsional resonance tunneling mode atomic force microscopy is used to study the conductivity of nanoparticles. SnS nanoparticles capped with trioctylphosphine oxide (TOPO) and with In2S3 shell are analyzed. This contactless technique allows carrying out measurements on nanoparticles w

  17. Characterization of novel sufraces by FTIR spectroscopy and atomic force microscopy for food pathogen detection

    Science.gov (United States)

    Single molecular detection of pathogens and toxins of interest to food safety is within grasp using technology such as Atomic Force Microscopy. Using antibodies or specific aptamers connected to the AFM tip make it possible to detect a pathogen molecule on a surface. However, it also becomes necess...

  18. A Study of the Probe Effect on the Apparent Image of Biological Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.

  19. Three-dimensional nanometrology of microstructures by replica molding and large-range atomic force microscopy

    DEFF Research Database (Denmark)

    Stöhr, Frederik; Michael-Lindhard, Jonas; Simons, Hugh

    2015-01-01

    We have used replica molding and large-range atomic force microscopy to characterize the threedimensional shape of high aspect ratio microstructures. Casting inverted replicas of microstructures using polydimethylsiloxane (PDMS) circumvents the inability of AFM probes to measure deep and narrow c...

  20. Sulfonated polyetherketone (SPEK-C) films investigated by positron annihilation lifetime spectroscopy and atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    Htwe Htwe Yin; YIN Ze-Jie; TANG Shi-Biao; HUANG Huan; ZHU Da-Ming

    2005-01-01

    The characterization of sulfonated polyetherketone (SPEK-C) films was investigated by using positron annihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM). It was found that free volume radius and intensity depend on the variation of sulfonation degree and solvent evaporation time of the films. Pore size and distribution determined from PALS and AFM measurements showed reasonable agreement.

  1. Height anomalies in tappingmode atomic force microscopy in air caused by adhesion

    NARCIS (Netherlands)

    Noort, van S. John T.; Werf, van der Kees O.; Grooth, de Bart G.; Hulst, van Niek F.; Greve, Jan

    1997-01-01

    Height anomalies in tapping mode atomic force microscopy (AFM) in air are shown to be caused by adhesion. Depending o­n the damping of the oscillation the height of a sticking surface is reduced compared to less sticking surfaces. It is shown that the height artefacts result from a modulation of osc

  2. Electrical characterization of grain boundaries of CZTS thin films using conductive atomic force microscopy techniques

    Energy Technology Data Exchange (ETDEWEB)

    Muhunthan, N.; Singh, Om Pal [Compound Semiconductor Solar Cell, Physics of Energy Harvesting Division, New Delhi 110012 (India); Toutam, Vijaykumar, E-mail: toutamvk@nplindia.org [Quantum Phenomena and Applications Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Singh, V.N., E-mail: singhvn@nplindia.org [Compound Semiconductor Solar Cell, Physics of Energy Harvesting Division, New Delhi 110012 (India)

    2015-10-15

    Graphical abstract: Experimental setup for conducting AFM (C-AFM). - Highlights: • Cu{sub 2}ZnSnS{sub 4} (CZTS) thin film was grown by reactive co-sputtering. • The electronic properties were probed using conducting atomic force microscope, scanning Kelvin probe microscopy and scanning capacitance microscopy. • C-AFM current flow mainly through grain boundaries rather than grain interiors. • SKPM indicated higher potential along the GBs compared to grain interiors. • The SCM explains that charge separation takes place at the interface of grain and grain boundary. - Abstract: Electrical characterization of grain boundaries (GB) of Cu-deficient CZTS (Copper Zinc Tin Sulfide) thin films was done using atomic force microscopic (AFM) techniques like Conductive atomic force microscopy (CAFM), Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM). Absorbance spectroscopy was done for optical band gap calculations and Raman, XRD and EDS for structural and compositional characterization. Hall measurements were done for estimation of carrier mobility. CAFM and KPFM measurements showed that the currents flow mainly through grain boundaries (GB) rather than grain interiors. SCM results showed that charge separation mainly occurs at the interface of grain and grain boundaries and not all along the grain boundaries.

  3. Atomic force microscopy as a tool to evaluate the risk of cardiovascular diseases in patients

    Science.gov (United States)

    Guedes, Ana Filipa; Carvalho, Filomena A.; Malho, Inês; Lousada, Nuno; Sargento, Luís; Santos, Nuno C.

    2016-08-01

    The availability of biomarkers to evaluate the risk of cardiovascular diseases is limited. High fibrinogen levels have been identified as a relevant cardiovascular risk factor, but the biological mechanisms remain unclear. Increased aggregation of erythrocytes (red blood cells) has been linked to high plasma fibrinogen concentration. Here, we show, using atomic force microscopy, that the interaction between fibrinogen and erythrocytes is modified in chronic heart failure patients. Ischaemic patients showed increased fibrinogen-erythrocyte binding forces compared with non-ischaemic patients. Cell stiffness in both patient groups was also altered. A 12-month follow-up shows that patients with higher fibrinogen-erythrocyte binding forces initially were subsequently hospitalized more frequently. Our results show that atomic force microscopy can be a promising tool to identify patients with increased risk for cardiovascular diseases.

  4. Atomic force microscopy of swelling and hardening of intact erythrocytes fixed on substrate

    Science.gov (United States)

    Khalisov, M. M.; Timoshchuk, K. I.; Ankudinov, A. V.; Timoshenko, T. E.

    2017-02-01

    Peak force measurements with the aid of atomic force microscopy are used to quantitatively map nanomechanical properties of intact erythrocytes of rats under conditions that are close to physiological conditions. Erythrocytes that are immobilized on the substrate preliminary processed using poly-L-lysine predominantly exhibit plane shape. However, cells may also exhibit stepwise transformation to semispherical objects with an increase in volume and hardening. Possible reasons for such transformations are discussed.

  5. Computational model for noncontact atomic force microscopy: energy dissipation of cantilever.

    Science.gov (United States)

    Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M

    2016-09-21

    We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model.

  6. Binding Strength Between Cell Adhesion Proteoglycans Measured by Atomic Force Microscopy

    Science.gov (United States)

    Dammer, Ulrich; Popescu, Octavian; Wagner, Peter; Anselmetti, Dario; Guntherodt, Hans-Joachim; Misevic, Gradimir N.

    1995-02-01

    Measurement of binding forces intrinsic to adhesion molecules is necessary to assess their contribution to the maintenance of the anatomical integrity of multicellular organisms. Atomic force microscopy was used to measure the binding strength between cell adhesion proteoglycans from a marine sponge. Under physiological conditions, the adhesive force between two cell adhesion molecules was found to be up to 400 piconewtons. Thus a single pair of molecules could hold the weight of 1600 cells. High intermolecular binding forces are likely to form the basis for the integrity of the multicellular sponge organism.

  7. Implementing atomic force microscopy (AFM) for studying kinetics of gold nanoparticle's growth

    DEFF Research Database (Denmark)

    Georgiev, P.; Bojinova, A.; Kostova, B.

    2013-01-01

    In a novel experimental approach Atomic Force Microscopy (AFM) was applied as a tool for studying the kinetics of gold nanoparticle growth. The gold nanoparticles were obtained by classical Turkevich citrate synthesis at two different temperatures. From the analysis of AFM images during the synth......In a novel experimental approach Atomic Force Microscopy (AFM) was applied as a tool for studying the kinetics of gold nanoparticle growth. The gold nanoparticles were obtained by classical Turkevich citrate synthesis at two different temperatures. From the analysis of AFM images during...... approach. We also compared AFM experimental data with Dynamic Light Scattering (DLS) and with Transmission Electron Microscopy (TEM) data. The experimental data from all the applied methods were fitted with two step Finke-Watzky kinetics model and the corresponding kinetics constants were obtained...

  8. Mapping nanomechanical properties of live cells using multi-harmonic atomic force microscopy

    Science.gov (United States)

    Raman, A.; Trigueros, S.; Cartagena, A.; Stevenson, A. P. Z.; Susilo, M.; Nauman, E.; Contera, S. Antoranz

    2011-12-01

    The nanomechanical properties of living cells, such as their surface elastic response and adhesion, have important roles in cellular processes such as morphogenesis, mechano-transduction, focal adhesion, motility, metastasis and drug delivery. Techniques based on quasi-static atomic force microscopy techniques can map these properties, but they lack the spatial and temporal resolution that is needed to observe many of the relevant details. Here, we present a dynamic atomic force microscopy method to map quantitatively the nanomechanical properties of live cells with a throughput (measured in pixels/minute) that is ~10-1,000 times higher than that achieved with quasi-static atomic force microscopy techniques. The local properties of a cell are derived from the 0th, 1st and 2nd harmonic components of the Fourier spectrum of the AFM cantilevers interacting with the cell surface. Local stiffness, stiffness gradient and the viscoelastic dissipation of live Escherichia coli bacteria, rat fibroblasts and human red blood cells were all mapped in buffer solutions. Our method is compatible with commercial atomic force microscopes and could be used to analyse mechanical changes in tumours, cells and biofilm formation with sub-10 nm detail.

  9. Multiparametric atomic force microscopy imaging of single bacteriophages extruding from living bacteria

    Science.gov (United States)

    Alsteens, David; Trabelsi, Heykel; Soumillion, Patrice; Dufrêne, Yves F.

    2013-12-01

    Force-distance (FD) curve-based atomic force microscopy is a valuable tool to simultaneously image the structure and map the biophysical properties of biological samples at the nanoscale. Traditionally, FD-based atomic force microscopy has been severely limited by its poor temporal and lateral resolutions. Here we report the use of advanced FD-based technology combined with biochemically sensitive tips to image filamentous bacteriophages extruding from living bacteria at unprecedented speed and resolution. Directly correlated multiparametric images of the structure, adhesion and elasticity of infected bacteria demonstrate that the sites of assembly and extrusion localize at the bacterial septum in the form of soft nanodomains surrounded by stiff cell wall material. The quantitative nano-bio-imaging method presented here offers a wealth of opportunities for mapping the physical properties and molecular interactions of complex biosystems, from viruses to tissues.

  10. Comparision of atomic force microscopy interaction forces between bacteria and silicon nitride substrata for three commonly used immobilization methods

    NARCIS (Netherlands)

    Vadillo-Rodríguez, Virginia; Busscher, Henk J; Norde, Willem; de Vries, Joop; Dijkstra, René JB; Stokroos, Ietse; van der Mei, Henderina

    2004-01-01

    Atomic force microscopy (AFM) has emerged as a powerful technique for mapping the surface morphology of biological specimens, including bacterial cells. Besides creating topographic images, AFM enables us to probe both physicochemical and mechanical properties of bacterial cell surfaces on a nanomet

  11. Comparison of Atomic Force Microscopy interaction forces between bacteria and silicon nitride substrata for three commonly used immobilization methods

    NARCIS (Netherlands)

    Vadillo-Rodriguez, V.; Busscher, H.J.; Norde, W.; Vries, de J.; Dijkstra, R.J.B.; Stokroos, I.; Mei, van der H.C.

    2004-01-01

    Atomic force microscopy (AFM) has emerged as a powerful technique for mapping the surface morphology of biological specimens, including bacterial cells. Besides creating topographic images, AFM enables us to probe both physicochemical and mechanical properties of bacterial cell surfaces on a nanomet

  12. Topological Structures and Membrane Nanostructures of Erythrocytes after Splenectomy in Hereditary Spherocytosis Patients via Atomic Force Microscopy

    OpenAIRE

    Li, Ying; Lu, Liyuan; Li, Juan

    2016-01-01

    Hereditary spherocytosis is an inherited red blood cell membrane disorder resulting from mutations of genes encoding erythrocyte membrane and cytoskeletal proteins. Few equipments can observe the structural characteristics of hereditary spherocytosis directly expect for atomic force microscopy In our study, we proved atomic force microscopy is a powerful and sensitive instrument to describe the characteristics of hereditary spherocytosis. Erythrocytes from hereditary spherocytosis patients we...

  13. Characterization of gold nanoparticle films: Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Pia C. Lansåker

    2014-10-01

    Full Text Available Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness dg—from the substrate to the tops of the nanoparticles—was obtained by scanning electron microscopy (SEM combined with image analysis as well as by atomic force microscopy (AFM. The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for dg were obtained by SEM with image analysis and by AFM.

  14. Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy

    Science.gov (United States)

    Cantrell, John H.; Cantrell, Sean A.

    2010-01-01

    The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.

  15. Higher order structure of short immunostimulatory oligonucleotides studied by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Dionne C.G., E-mail: dionne.c.g.klein@ntnu.no [Department of Physics, Norwegian University of Science and Technology, N-7491, Trondheim (Norway); Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489, Trondheim (Norway); Latz, Eicke [Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489, Trondheim (Norway); Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605 (United States); Institute of Innate Immunity, University Hospitals, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn (Germany); Espevik, Terje [Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, N-7489, Trondheim (Norway); Stokke, Bjorn T. [Department of Physics, Norwegian University of Science and Technology, N-7491, Trondheim (Norway)

    2010-05-15

    Immunostimulatory CpG-DNA activates the innate immune system by binding to Toll-like receptor 9. Structurally different CpG-containing oligonucleotides trigger a different type of immune response while activating the same receptor. We therefore investigated the higher order structure of two different classes of immunostimulatory CpG-DNA. Class A, which contains a partly self-complementary sequence and poly-G ends, forms duplexes and nanoparticles in salt solution, while class B, which does not contain these features and is purely linear, does not form a duplex or nanoparticles. Results obtained here by high-resolution atomic force microscopy of classes A and B CpG-DNA, reflect these differences in secondary structure. Detailed structural analysis of the atomic force microscopy topographs is presented for two different sample preparation methods.

  16. Chiral Asymmetric Structures in Aspartic Acid and Valine Crystals Assessed by Atomic Force Microscopy.

    Science.gov (United States)

    Teschke, Omar; Soares, David Mendez

    2016-03-29

    Structures of crystallized deposits formed by the molecular self-assembly of aspartic acid and valine on silicon substrates were imaged by atomic force microscopy. Images of d- and l-aspartic acid crystal surfaces showing extended molecularly flat sheets or regions separated by single molecule thick steps are presented. Distinct orientation surfaces were imaged, which, combined with the single molecule step size, defines the geometry of the crystal. However, single molecule step growth also reveals the crystal chirality, i.e., growth orientations. The imaged ordered lattice of aspartic acid (asp) and valine (val) mostly revealed periodicities corresponding to bulk terminations, but a previously unreported molecular hexagonal lattice configuration was observed for both l-asp and l-val but not for d-asp or d-val. Atomic force microscopy can then be used to identify the different chiral forms of aspartic acid and valine crystals.

  17. Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Jorge R., E-mail: jorge.rr@cea.cu [Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz 3, Canto Blanco, 28049 Madrid, España (Spain)

    2014-07-28

    The acquisition of high resolution images in atomic force microscopy (AFM) is correlated to the cantilever's tip shape, size, and imaging conditions. In this work, relative tip wear is quantified based on the evolution of a direct experimental observable in amplitude modulation atomic force microscopy, i.e., the critical amplitude. We further show that the scanning parameters required to guarantee a maximum compressive stress that is lower than the yield/fracture stress of the tip can be estimated via experimental observables. In both counts, the optimized parameters to acquire AFM images while preserving the tip are discussed. The results are validated experimentally by employing IgG antibodies as a model system.

  18. Nano-scale observations of tattoo pigments in skin by atomic force microscopy.

    Science.gov (United States)

    Grant, Colin A; Twigg, Peter C; Tobin, Desmond J

    2015-01-01

    In this study, we have shown how particles in carbon black tattoo ink accumulate in the human skin dermis using fine-resolution atomic force microscopy, with which a single ink particle in the collagenous network can be imaged. This information further demonstrates that tattoo inks are nano-particles. Further, we have deposited a commercially available tattoo ink on a glass slide and calculated a range of volumes for single ink particles.

  19. Single-molecule reconstruction of oligonucleotide secondary structure by atomic force microscopy.

    Science.gov (United States)

    Pyne, Alice; Thompson, Ruth; Leung, Carl; Roy, Debdulal; Hoogenboom, Bart W

    2014-08-27

    Based on soft-touch atomic force microscopy, a method is described to reconstruct the secondary structure of single extended biomolecules, without the need for crystallization. The method is tested by accurately reproducing the dimensions of the B-DNA crystal structure. Importantly, intramolecular variations in groove depth of the DNA double helix are resolved, which would be inaccessible for methods that rely on ensemble-averaging.

  20. Error sources in atomic force microscopy for dimensional measurements: Taxonomy and modeling

    DEFF Research Database (Denmark)

    Marinello, F.; Voltan, A.; Savio, E.

    2010-01-01

    This paper aimed at identifying the error sources that occur in dimensional measurements performed using atomic force microscopy. In particular, a set of characterization techniques for errors quantification is presented. The discussion on error sources is organized in four main categories......: scanning system, tip-surface interaction, environment, and data processing. The discussed errors include scaling effects, squareness errors, hysteresis, creep, tip convolution, and thermal drift. A mathematical model of the measurement system is eventually described, as a reference basis for errors...

  1. Magni: A Python Package for Compressive Sampling and Reconstruction of Atomic Force Microscopy Images

    DEFF Research Database (Denmark)

    Oxvig, Christian Schou; Pedersen, Patrick Steffen; Arildsen, Thomas

    2014-01-01

    provides researchers in compressed sensing with a selection of algorithms for reconstructing undersampled general images, and offers a consistent and rigorous way to efficiently evaluate the researchers own developed reconstruction algorithms in terms of phase transitions. The package also serves......Magni is an open source Python package that embraces compressed sensing and Atomic Force Microscopy (AFM) imaging techniques. It provides AFM-specific functionality for undersampling and reconstructing images from AFM equipment and thereby accelerating the acquisition of AFM images. Magni also...

  2. Tailored probes for atomic force microscopy fabricated by two-photon polymerization

    Science.gov (United States)

    Göring, Gerald; Dietrich, Philipp-Immanuel; Blaicher, Matthias; Sharma, Swati; Korvink, Jan G.; Schimmel, Thomas; Koos, Christian; Hölscher, Hendrik

    2016-08-01

    3D direct laser writing based on two-photon polymerization is considered as a tool to fabricate tailored probes for atomic force microscopy. Tips with radii of 25 nm and arbitrary shape are attached to conventionally shaped micro-machined cantilevers. Long-term scanning measurements reveal low wear rates and demonstrate the reliability of such tips. Furthermore, we show that the resonance spectrum of the probe can be tuned for multi-frequency applications by adding rebar structures to the cantilever.

  3. Atomic force microscopy study of the antibacterial effects of chitosans on Escherichia coli and Staphylococcus aureus

    OpenAIRE

    2008-01-01

    Chitosan has been reported to be a non-toxic, biodegradable antibacterial agent. The aim of this work was to elucidate the relationship between the molecular weight of chitosan and its antimicrobial activity upon two model microorganisms, one Gram-positive (Staphylococcus aureus) and one Gramnegative (Escherichia coli). Atomic force microscopy (AFM) imaging was used to obtain high-resolution images of the effect of chitosans on the bacterial morphology. The AFM measurements were correlated...

  4. Investigation of organic films by atomic force microscopy: Structural, nanotribological and electrical properties

    Science.gov (United States)

    Qi, Yabing

    2011-11-01

    Atomic force microscopy (AFM) has found its applications in a wide range of research fields. In this review, we show by examples that atomic force microscopy is a powerful technique to investigate structural, mechanical and electrical properties of organic films. We start with an introduction of AFM instrumentation highlighting AFM developments that are of direct relevance to organic films. Next, we review AFM studies on organic films according to their preparation methods: self-assembly, the Langmuir-Blodgett technique, solution preparation, and thermal evaporation. In the discussion on self-assembled monolayers, we focus on aspects such as structural evolution, load-induced molecular tilting, annealing, and incorporation of conjugated groups. For solution prepared organic films, we stress annealing-induced structural evolution as well as the effects of phase separation/segregation. We also briefly summarize the progress of AFM investigation on Langmuir-Blodgett films and thermally evaporated organic films. We conclude the review by providing some thoughts for future exploration. In particular, atomic force microscopy combined with ultra-flat coplanar nano-electrodes provides a promising platform to isolate single or a small number of molecular features (e.g. vacancies, defects, grain boundaries) in organic films as well as to identify the role of these features at the nanometer scale.

  5. Sub-cellular structure studied by combined atomic force-fluorescence microscopy

    Science.gov (United States)

    Trache, Andreea

    2009-03-01

    A novel experimental technique that integrates atomic force microscopy (AFM) with fluorescence imaging was used to study the role of extracellular matrix proteins in cellular organization. To understand the mechanism by which living cells sense mechanical forces, and how they respond and adapt to their environment, we developed a new technology able to investigate cellular behavior at sub-cellular level that integrates an AFM with total internal reflection fluorescence (TIRF) microscopy and fast-spinning disk (FSD) confocal microscopy. Live smooth muscle cells exhibited differences in focal adhesions and actin pattern depending on the extracellular matrix used for substrate coating. Data obtained by using the AFM-optical imaging integrated technique offer novel quantitative information that allows understanding the fundamental processes of cellular reorganization in response to extracellular matrix modulation. The integrated microscope presented here is broadly applicable across a wide range of molecular dynamic studies in any adherent live cells.

  6. Observation of banded spherulites and lamellar structures by atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    姜勇; 罗艳红; 范泽夫; 王霞瑜; 徐军; 郭宝华; 李林

    2003-01-01

    Lamellar structures of banded spherulites of poly(ε-caprolactone)/poly(vinyl chloride) (PCL/PVC) blends are observed using tapping mode atomic force microscopy (AFM). The surface of the PCL/PVC banded spherulites presents to be concentric periodic ups and downs. The period of the bands corresponds to the extinction rings under the polarized optical microscopy observation. The lamellae with edge-on orientation in the ridges and the flat-on lamellae in the valleys of the banded spherulites are observed clearly. The twisting between the edge-on and flat-on lamellae is also observed.

  7. Sharing my fifteen years experiences in the research field of Atomic Force Microscopy (AFM

    Directory of Open Access Journals (Sweden)

    Guha T

    2014-03-01

    Full Text Available Atomic Force Microscope (AFM was developed by Binnig and his coworkers in the year 1986. He was awarded Nobel Prize in physics for this work in 1986 in sharing with Rohrer and Ruska. Rationale to develop AFM: Scanning Tunneling Microscope (STM, the precursor to AFM is efficient in imaging electrically conducting specimen at atomic resolution. The impetus for development of AFM came to Binnig’s mind because of relatively poor efficiency of STM to image electrically non-conducting biological samples. He wondered why the surfaces be always imaged with a current but not with a force. He thought if small forces of interactions between a probe tip atoms and specimen surface atoms could be detected and amplified then imaging of biological specimen would be possible at a very high resolution. AFM working Principle: AFM is a Scanning Probe Microscopy (SPM by which imaging is realized by interaction of a probe with sample surface without any beam (light, electron and lens system. The probe is attached to a soft and sensitive cantilever and either specimen is scanned by probe or specimen scans itself under a stationary probe. Probe’s spring constant must be small and the deflection must be measurable along with high resonance frequency. The most commonly associated force with AFM is called Vander Waals force. Three modes of working are contact mode, non contact mode and tapping mode. In contact zone, the probe tip attached with cantilever is held less than a few A˚ from the sample surface and the inter-atomic force between the atoms of probe tip and sample surface is repulsive. In non-contact zone, the probe tip is held at a distance of 100s of A˚ from the sample surface and the inter-atomic force here is long range Vander Waals interaction and is attractive in nature. AFM is also called Scanning Force Microscope because the force of interaction between probe tip atoms and surface atoms is amplified to generate a signal voltage which modulates video

  8. Fabrication of metal oxide nanostructures based on Atomic Force Microscopy lithography

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Atomic Force Microscopy (AFM) mechanical lithography is a simple but significant method for nanofabrication. In this work, we used this method to construct nanos- tructures on Pt/Cu bilayer metal electrodes under ambient conditions in air. The influence of various scratch parameters, such as the applied force, scan velocity and circle times, on the lithography patterns was investigated. The Pt-Cu-CuxO-Cu-Pt nanostructure was constructed by choosing suitable scratch parameters and oxidation at room temperature. The properties of the scratched regions were also investigated by friction force microscopy and conductive AFM (C-AFM). The I-V curves show symmetric and linear properties, and Ohmic contacts were formed. These results indicate that AFM mechanical lithography is a powerful tool for fabricating novel metal-semiconductor nanoelectronic devices.

  9. Atomic Force Microscopy Based Nanorobotics Modelling, Simulation, Setup Building and Experiments

    CERN Document Server

    Xie, Hui; Régnier, Stéphane; Sitti, Metin

    2012-01-01

    The atomic force microscope (AFM) has been successfully used to perform nanorobotic manipulation operations on nanoscale entities such as particles, nanotubes, nanowires, nanocrystals, and DNA since 1990s. There have been many progress on modeling, imaging, teleoperated or automated control, human-machine interfacing, instrumentation, and applications of AFM based nanorobotic manipulation systems in literature. This book aims to include all of such state-of-the-art progress in an organized, structured, and detailed manner as a reference book and also potentially a textbook in nanorobotics and any other nanoscale dynamics, systems and controls related research and education. Clearly written and well-organized, this text introduces designs and prototypes of the nanorobotic systems in detail with innovative principles of three-dimensional manipulation force microscopy and parallel imaging/manipulation force microscopy.

  10. Fabrication of metal oxide nanostructures based on Atomic Force Microscopy lithography

    Institute of Scientific and Technical Information of China (English)

    ZHU XiaoYang; CHENG Gang; WANG ShuJie; DAI ShuXi; WAN ShaoMing; ZHANG XingTang; DU ZuLiang

    2008-01-01

    Atomic Force Microscopy (AFM) mechanical lithography is a simple but significant method for nanofabrication. In this work, we used this method to construct nanos-tructures on Pt/Cu bilayer metal electrodes under ambient conditions in air. The influence of various scratch parameters, such as the applied force, scan velocity and circle times, on the lithography patterns was investigated. The Pt-Cu-CuxO-Cu-Pt nanostructure was constructed by choosing suitable scratch parameters and oxidation at room temperature. The properties of the scratched regions were also investigated by friction force microscopy and conductive AFM (C-AFM). The/-Vcurves show symmetric and linear properties, and Ohmic contacts were formed. These results indicate that AFM mechanical lithography is a powerful tool for fabricating novel metal-semiconductor nanoelectronic devices.

  11. Detecting CD20-Rituximab specific interactions on lymphoma cells using atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Elucidating the underlying mechanisms of cell physiology is currently an important research topic in life sciences. Atomic force microscopy methods can be used to investigate these molecular mechanisms. In this study, single-molecule force spectroscopy was used to explore the specific recognition between the CD20 antigen and anti-CD20 antibody Rituximab on B lymphoma cells under near-physiological conditions. The CD20-Rituximab specific binding force was measured through tip functionalization. Distribution of CD20 on the B lymphoma cells was visualized three-dimensionally. In addition, the relationship between the intramolecular force and the molecular extension of the CD20-Rituximab complex was analyzed under an external force. These results facilitate further investigation of the mechanism of Rituximab’s anti-cancer effect.

  12. Quantification of Staphylococcus aureus adhesion forces on various dental restorative materials using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Merghni, Abderrahmen, E-mail: abderrahmen_merghni@yahoo.fr [Laboratoire des Maladies Transmissibles et Substances biologiquement actives (LR99ES27) Faculté de Pharmacie de Monastir, Université de Monastir (Tunisia); Kammoun, Dorra [Laboratoire de Biomatériaux et Biotechnologie, Faculté de Médecine Dentaire, Monastir (Tunisia); Hentati, Hajer [Laboratoire de Recherche en Santé Orale et Réhabilitation Bucco-Faciale (LR12ES11), Faculté de Médecine Dentaire de Monastir, Université de Monastir (Tunisia); Janel, Sébastien [BioImaging Center Lille-FR3642, Lille (France); Popoff, Michka [Cellular Microbiology and Physics of Infection-CNRS UMR8204, INSERM U1019, Institut Pasteur de Lille, Lille University (France); Lafont, Frank [BioImaging Center Lille-FR3642, Lille (France); Cellular Microbiology and Physics of Infection-CNRS UMR8204, INSERM U1019, Institut Pasteur de Lille, Lille University (France); Aouni, Mahjoub [Laboratoire des Maladies Transmissibles et Substances biologiquement actives (LR99ES27) Faculté de Pharmacie de Monastir, Université de Monastir (Tunisia); Mastouri, Maha [Laboratoire des Maladies Transmissibles et Substances biologiquement actives (LR99ES27) Faculté de Pharmacie de Monastir, Université de Monastir (Tunisia); Laboratoire de Microbiologie, CHU Fattouma Bourguiba de Monastir (Tunisia)

    2016-08-30

    Highlights: • 4 dental restorative materials were characterized for roughness, angle contact water and surface free energy. • AFM adhesion forces of S. aureus to tested materials were achieved in presence and absence of salivary conditioning film. • S. aureus initial adhesion is dependent on the surface free energy and roughness. - Abstract: In the oral cavity dental restorative biomaterials can act as a reservoir for infection with opportunistic Staphylococcus aureus pathogen, which can lead to the occurrence of secondary caries and treatment failures. Our aim was to evaluate the adhesion forces by S. aureus on four dental restorative biomaterials and to correlate this finding to differences in specific surface characteristics. Additionally, the influence of salivary conditioning films in exerted adhesion forces was investigated. The substrate hydrophobicity was measured by goniometer and the surface free energy was calculated using the equilibrium advancing contact angle values of water, formamide, and diiodomethane on the tested surfaces. The surface roughness was determined using atomic force microscope (AFM). Additionally, cell force spectroscopy was achieved to quantify the forces that drive cell-substrate interactions. S. aureus bacterium exerted a considerable adhesion forces on various dental restorative materials, which decreased in the presence of saliva conditioning film. The influence of the surface roughness and free energy in initial adhesion appears to be more important than the effect of hydrophobicity, either in presence or absence of saliva coating. Hence, control of surface properties of dental restorative biomaterials is of crucial importance in preventing the attachment and subsequent the biofilm formation.

  13. Application of atomic force microscopy to the study of natural and model soil particles.

    Science.gov (United States)

    Cheng, S; Bryant, R; Doerr, S H; Rhodri Williams, P; Wright, C J

    2008-09-01

    The structure and surface chemistry of soil particles has extensive impact on many bulk scale properties and processes of soil systems and consequently the environments that they support. There are a number of physiochemical mechanisms that operate at the nanoscale which affect the soil's capability to maintain native vegetation and crops; this includes soil hydrophobicity and the soil's capacity to hold water and nutrients. The present study used atomic force microscopy in a novel approach to provide unique insight into the nanoscale properties of natural soil particles that control the physiochemical interaction of material within the soil column. There have been few atomic force microscopy studies of soil, perhaps a reflection of the heterogeneous nature of the system. The present study adopted an imaging and force measurement research strategy that accounted for the heterogeneity and used model systems to aid interpretation. The surface roughness of natural soil particles increased with depth in the soil column a consequence of the attachment of organic material within the crevices of the soil particles. The roughness root mean square calculated from ten 25 microm(2) images for five different soil particles from a Netherlands soil was 53.0 nm, 68.0 nm, 92.2 nm and 106.4 nm for the respective soil depths of 0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm. A novel analysis method of atomic force microscopy phase images based on phase angle distribution across a surface was used to interpret the nanoscale distribution of organic material attached to natural and model soil particles. Phase angle distributions obtained from phase images of model surfaces were found to be bimodal, indicating multiple layers of material, which changed with the concentration of adsorbed humic acid. Phase angle distributions obtained from phase images of natural soil particles indicated a trend of decreasing surface coverage with increasing depth in the soil column. This was consistent with

  14. Can Point Defects in Surfaces in Solution be Atomically Resolved by Atomic Force Microscopy?

    Science.gov (United States)

    Reischl, Bernhard; Raiteri, Paolo; Gale, Julian D.; Rohl, Andrew L.

    2016-11-01

    While the atomic force microscope (AFM) is able to image mineral surfaces in solution with atomic resolution, so far, it has been a matter of debate whether imaging point defects is also possible under these conditions. The difficulties stem from the limited knowledge of what types of defects may be stable in the presence of an AFM tip, as well as from the complicated imaging mechanism involving interactions between hydration layers over the surface and around the tip apex. Here, we present atomistic molecular dynamics and free energy calculations of the AFM imaging of vacancies and ionic substitutions in the calcite (10 1 ¯ 4 ) surface in water, using a new silica AFM tip model. Our results indicate that both calcium and carbonate vacancies, as well as a magnesium substitution, could be resolved in an AFM experiment, albeit with different imaging mechanisms.

  15. Free-standing biomimetic polymer membrane imaged with atomic force microscopy

    DEFF Research Database (Denmark)

    Rein, Christian; Pszon-Bartosz, Kamila Justyna; Jensen, Karin Bagger Stibius

    2011-01-01

    Fluid polymeric biomimetic membranes are probed with atomic force microscopy (AFM) using probes with both normal tetrahedrally shaped tips and nanoneedle-shaped Ag2Ga rods. When using nanoneedle probes, the collected force volume data show three distinct membrane regions which match the expected...... membrane structure when spanning an aperture in a hydrophobic scaffold. The method used provides a general method for mapping attractive fluid surfaces. In particular, the nanoneedle probing allows for characterization of free-standing biomimetic membranes with thickness on the nanometer scale suspended...

  16. Molecular Dynamics Simulation of Atomic Force Microscopy at the Water-Muscovite Interface: Hydration Layer Structure and Force Analysis.

    Science.gov (United States)

    Kobayashi, Kazuya; Liang, Yunfeng; Amano, Ken-ichi; Murata, Sumihiko; Matsuoka, Toshifumi; Takahashi, Satoru; Nishi, Naoya; Sakka, Tetsuo

    2016-04-19

    With the development of atomic force microscopy (AFM), it is now possible to detect the buried liquid-solid interfacial structure in three dimensions at the atomic scale. One of the model surfaces used for AFM is the muscovite surface because it is atomically flat after cleavage along the basal plane. Although it is considered that force profiles obtained by AFM reflect the interfacial structures (e.g., muscovite surface and water structure), the force profiles are not straightforward because of the lack of a quantitative relationship between the force and the interfacial structure. In the present study, molecular dynamics simulations were performed to investigate the relationship between the muscovite-water interfacial structure and the measured AFM force using a capped carbon nanotube (CNT) AFM tip. We provide divided force profiles, where the force contributions from each water layer at the interface are shown. They reveal that the first hydration layer is dominant in the total force from water even after destruction of the layer. Moreover, the lateral structure of the first hydration layer transcribes the muscovite surface structure. It resembles the experimentally resolved surface structure of muscovite in previous AFM studies. The local density profile of water between the tip and the surface provides further insight into the relationship between the water structure and the detected force structure. The detected force structure reflects the basic features of the atomic structure for the local hydration layers. However, details including the peak-peak distance in the force profile (force-distance curve) differ from those in the density profile (density-distance curve) because of disturbance by the tip.

  17. Quantification of Staphylococcus aureus adhesion forces on various dental restorative materials using atomic force microscopy

    Science.gov (United States)

    Merghni, Abderrahmen; Kammoun, Dorra; Hentati, Hajer; Janel, Sébastien; Popoff, Michka; Lafont, Frank; Aouni, Mahjoub; Mastouri, Maha

    2016-08-01

    In the oral cavity dental restorative biomaterials can act as a reservoir for infection with opportunistic Staphylococcus aureus pathogen, which can lead to the occurrence of secondary caries and treatment failures. Our aim was to evaluate the adhesion forces by S. aureus on four dental restorative biomaterials and to correlate this finding to differences in specific surface characteristics. Additionally, the influence of salivary conditioning films in exerted adhesion forces was investigated. The substrate hydrophobicity was measured by goniometer and the surface free energy was calculated using the equilibrium advancing contact angle values of water, formamide, and diiodomethane on the tested surfaces. The surface roughness was determined using atomic force microscope (AFM). Additionally, cell force spectroscopy was achieved to quantify the forces that drive cell-substrate interactions. S. aureus bacterium exerted a considerable adhesion forces on various dental restorative materials, which decreased in the presence of saliva conditioning film. The influence of the surface roughness and free energy in initial adhesion appears to be more important than the effect of hydrophobicity, either in presence or absence of saliva coating. Hence, control of surface properties of dental restorative biomaterials is of crucial importance in preventing the attachment and subsequent the biofilm formation.

  18. Mapping power-law rheology of living cells using multi-frequency force modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryosuke; Okajima, Takaharu, E-mail: okajima@ist.hokudai.ac.jp [Graduate School of Information Science and Technology, Hokkaido University, Kita-ku N14 W9, Sapporo 060-0814 (Japan)

    2015-10-26

    We present multi-frequency force modulation atomic force microscopy (AFM) for mapping the complex shear modulus G* of living cells as a function of frequency over the range of 50–500 Hz in the same measurement time as the single-frequency force modulation measurement. The AFM technique enables us to reconstruct image maps of rheological parameters, which exhibit a frequency-dependent power-law behavior with respect to G{sup *}. These quantitative rheological measurements reveal a large spatial variation in G* in this frequency range for single cells. Moreover, we find that the reconstructed images of the power-law rheological parameters are much different from those obtained in force-curve or single-frequency force modulation measurements. This indicates that the former provide information about intracellular mechanical structures of the cells that are usually not resolved with the conventional force measurement methods.

  19. Fuzzy logic algorithm to extract specific interaction forces from atomic force microscopy data

    Science.gov (United States)

    Kasas, Sandor; Riederer, Beat M.; Catsicas, Stefan; Cappella, Brunero; Dietler, Giovanni

    2000-05-01

    The atomic force microscope is not only a very convenient tool for studying the topography of different samples, but it can also be used to measure specific binding forces between molecules. For this purpose, one type of molecule is attached to the tip and the other one to the substrate. Approaching the tip to the substrate allows the molecules to bind together. Retracting the tip breaks the newly formed bond. The rupture of a specific bond appears in the force-distance curves as a spike from which the binding force can be deduced. In this article we present an algorithm to automatically process force-distance curves in order to obtain bond strength histograms. The algorithm is based on a fuzzy logic approach that permits an evaluation of "quality" for every event and makes the detection procedure much faster compared to a manual selection. In this article, the software has been applied to measure the binding strength between tubuline and microtubuline associated proteins.

  20. Nanotribological effects of hair care products and environment on human hair using atomic force microscopy

    Science.gov (United States)

    Latorre, Carmen; Bhushan, Bharat

    2005-07-01

    Tribological properties are useful in the study of human hair and other biological materials. Major sources of investigation for conditioner treated hair includes localization of conditioner, mechanisms related to changes in surface roughness, friction, and adhesion on the nanoscale due to conditioner agents, and how the products change the microstructure of the cuticle. The paper presents nanotribological studies investigating surface roughness, friction, and adhesion using atomic force/friction force microscopy (AFM/FFM). Test samples include virgin and chemically damaged hair, both with and without commercial conditioner treatment, as well as chemically damaged hair with experimental conditioner treatments. Friction force mapping provides insight into the localized change in friction caused by the application of hair care materials. Adhesive force maps to study adhesion on the cuticle surface provide information about localization and distribution of conditioner as well. A discussion is presented on these properties of hair as a function of relative humidity, temperature, durability, and conditioning treatments.

  1. NANOMECHANICAL MAPPING OF CARBON BLACK REINFORCED NATURAL RUBBER BY ATOMIC FORCE MICROSCOPY

    Institute of Scientific and Technical Information of China (English)

    Toshio Nishi; Hideyuki Nukaga; So Fujinami; Ken Nakajima

    2007-01-01

    Atomic force microscopy (AFM) has the advantage of obtaining mechanical properties as well as topographic information at the same time. By analyzing force-distance curves measured over two-dimensional area using Hertzian contact mechanics, Young's modulus mapping was obtained with nanometer-scale resolution. Furthermore, the sample deformation by the force exerted was also estimated from the force-distance curve analyses. We could thus reconstruct a real topographic image by incorporating apparent topographic image with deformation image. We applied this method to carbon black reinforced natural rubber to obtain Young's modulus distribution image together with reconstructed real topographic image.Then we were able to recognize three regions; rubber matrix, carbon black (or bound rubber) and intermediate regions.Though the existence of these regions had been investigated by pulsed nuclear magnetic resonance, this paper would be the first to report on the quantitative evaluation of the interfacial region in real space.

  2. Development of carbon electrodes for electrochemistry, solid-state electronics and multimodal atomic force microscopy imaging

    Science.gov (United States)

    Morton, Kirstin Claire

    Carbon is one of the most remarkable elements due to its wide abundance on Earth and its many allotropes, which include diamond and graphite. Many carbon allotropes are conductive and in recent decades scientists have discovered and synthesized many new forms of carbon, including graphene and carbon nanotubes. The work in this thesis specifically focuses on the fabrication and characterization of pyrolyzed parylene C (PPC), a conductive pyrocarbon, as an electrode material for diodes, as a conductive coating for atomic force microscopy (AFM) probes and as an ultramicroelectrode (UME) for the electrochemical interrogation of cellular systems in vitro. Herein, planar and three-dimensional (3D) PPC electrodes were microscopically, spectroscopically and electrochemically characterized. First, planar PPC films and PPC-coated nanopipettes were utilized to detect a model redox species, Ru(NH3) 6Cl3. Then, free-standing PPC thin films were chemically doped, with hydrazine and concentrated nitric acid, to yield p- and n-type carbon films. Doped PPC thin films were positioned in conjunction with doped silicon to create Schottky and p-n junction diodes for use in an alternating current half-wave rectifier circuit. Pyrolyzed parylene C has found particular merit as a 3D electrode coating of AFM probes. Current sensing-atomic force microscopy imaging in air of nanoscale metallic features was undertaken to demonstrate the electronic imaging applicability of PPC AFM probes. Upon further insulation with parylene C and modification with a focused ion beam, a PPC UME was microfabricated near the AFM probe apex and utilized for electrochemical imaging. Subsequently, scanning electrochemical microscopy-atomic force microscopy imaging was undertaken to electrochemically quantify and image the spatial location of dopamine exocytotic release, elicited mechanically via the AFM probe itself, from differentiated pheochromocytoma 12 cells in vitro.

  3. Correlative atomic force and confocal fluorescence microscopy: single molecule imaging and force induced spectral shifts (Conference Presentation)

    Science.gov (United States)

    Basché, Thomas; Hinze, Gerald; Stöttinger, Sven

    2016-09-01

    A grand challenge in nanoscience is to correlate structure or morphology of individual nano-sized objects with their photo-physical properties. An early example have been measurements of the emission spectra and polarization of single semiconductor quantum dots as well as their crystallographic structure by a combination of confocal fluorescence microscopy and transmission electron microscopy.[1] Recently, the simultaneous use of confocal fluorescence and atomic force microscopy (AFM) has allowed for correlating the morphology/conformation of individual nanoparticle oligomers or molecules with their photo-physics.[2, 3] In particular, we have employed the tip of an AFM cantilever to apply compressive stress to single molecules adsorbed on a surface and follow the effect of the impact on the electronic states of the molecule by fluorescence spectroscopy.[3] Quantum mechanical calculations corroborate that the spectral changes induced by the localized force can be associated to transitions among the different possible conformers of the adsorbed molecule.

  4. Mechanical properties of In/Si(111)-(8×2) investigated by atomic force microscopy

    Science.gov (United States)

    Iwata, Kota; Yamazaki, Shiro; Shiotari, Akitoshi; Sugimoto, Yoshiaki

    2017-01-01

    We use noncontact atomic force microscopy (AFM) as well as scanning tunneling microscopy (STM) to investigate the mechanical properties of quasi-one-dimensional indium chains on an In/Si(111) surface. The system shows phase transition from the 4×1 to 8×2 periodicity at temperatures near 120 K. AFM could not detect ×2 modulation along the chains near point defects at room temperature, but STM could. In contrast, the 8×2 phase at 80 K could be observed by AFM in phase with the STM image. High-resolution AFM images show that the 8×2 phase is not perturbed by mechanical interaction with the AFM tip because of misalignment between the reaction coordinates of the phase transition and the direction of the vertical force of the tip.

  5. Contact resonance atomic force microscopy imaging in air and water using photothermal excitation

    Energy Technology Data Exchange (ETDEWEB)

    Kocun, Marta; Labuda, Aleksander; Gannepalli, Anil; Proksch, Roger, E-mail: Roger.Proksch@oxinst.com [Asylum Research, an Oxford Instruments Company, Santa Barbara, California 93117 (United States)

    2015-08-15

    Contact Resonance Force Microscopy (CR-FM) is a leading atomic force microscopy technique for measuring viscoelastic nano-mechanical properties. Conventional piezo-excited CR-FM measurements have been limited to imaging in air, since the “forest of peaks” frequency response associated with acoustic excitation methods effectively masks the true cantilever resonance. Using photothermal excitation results in clean contact, resonance spectra that closely match the ideal frequency response of the cantilever, allowing unambiguous and simple resonance frequency and quality factor measurements in air and liquids alike. This extends the capabilities of CR-FM to biologically relevant and other soft samples in liquid environments. We demonstrate CR-FM in air and water on both stiff silicon/titanium samples and softer polystyrene-polyethylene-polypropylene polymer samples with the quantitative moduli having very good agreement between expected and measured values.

  6. Probing deviations from traditional colloid filtration theory by atomic forces microscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Reno, Marissa Devan

    2005-12-01

    Colloid transport through saturated media is an integral component of predicting the fate and transport of groundwater contaminants. Developing sound predictive capabilities and establishing effective methodologies for remediation relies heavily on our ability to understand the pertinent physical and chemical mechanisms. Traditionally, colloid transport through saturated media has been described by classical colloid filtration theory (CFT), which predicts an exponential decrease in colloid concentration with travel distance. Furthermore, colloid stability as determined by Derjaguin-Landau-Veney-Overbeek (DLVO) theory predicts permanent attachment of unstable particles in a primary energy minimum. However, recent studies show significant deviations from these traditional theories. Deposition in the secondary energy minimum has been suggested as a mechanism by which observed deviations can occur. This work investigates the existence of the secondary energy minimum as predicted by DLVO theory using direct force measurements obtained by Atomic Forces Microscopy. Interaction energy as a function of separation distance between a colloid and a quartz surface in electrolyte solutions of varying ionic strength are obtained. Preliminary force measurements show promise and necessary modifications to the current experimental methodology have been identified. Stringent surface cleaning procedures and the use of high-purity water for all injectant solutions is necessary for the most accurate and precise measurements. Comparisons between direct physical measurements by Atomic Forces Microscopy with theoretical calculations and existing experimental findings will allow the evaluation of the existence or absence of a secondary energy minimum.

  7. Looking at cell mechanics with atomic force microscopy: experiment and theory.

    Science.gov (United States)

    Benitez, Rafael; Toca-Herrera, José L

    2014-11-01

    This review reports on the use of the atomic force microscopy in the investigation of the mechanical properties of cells. It is shown that the technique is able to deliver information about the cell surface properties (e.g., topography), the Young modulus, the viscosity, and the cell the relaxation times. Another aspect that this short review points out is the utilization of the atomic force microscope to investigate basic questions related to materials physics, biology, and medicine. The review is written in a chronological way to offer an overview of phenomenological facts and quantitative results to the reader. The final section discusses in detail the advantages and disadvantages of the Hertz and JKR models. A new implementation of the JKR model derived by Dufresne is presented.

  8. Topography and Mechanical Property Mapping of International Simple Glass Surfaces with Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Eric M [ORNL

    2014-01-01

    Quantitative Nanomechanical Peak Force (PF-QNM) TappingModeTM atomic force microscopy measurements are presented for the first time on polished glass surfaces. The PF-QNM technique allows for topography and mechanical property information to be measured simultaneously at each pixel. Results for the international simple glass which represents a simplified version of SON68 glass suggests an average Young s modulus of 78.8 15.1 GPa is within the experimental error of the modulus measured for SON68 glass (83.6 2 GPa) with conventional approaches. Application of the PF-QNM technique will be extended to in situ glass corrosion experiments with the goal of gaining atomic-scale insights into altered layer development by exploiting the mechanical property differences that exist between silica gel (e.g., altered layer) and pristine glass surface.

  9. Nanoscale Thermal Response in ZnO Varistors by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Kun-Yu; ZENG Hua-Rong; LI Guo-Rong; SONG Hong-Zhang; CHENG Li-Hong; HUI Sen-Xing; YIN Qing-Rui

    2009-01-01

    We report the application of customer-built scanning thermal microscopy (SThM) based on a commercial atomic force microscope to investigate local thermal inhomogeneity of ZnO varistors.The so-called 3ω method, generally used for measuring macroscale thermal conductivity, is set up and integrated with an atomic force microscope to probe the nanoseale therma J property.Remarkably, thermal contrasts of ZnO varistors are firstly imaged by the SThM, indicating the uniform distribution of spinel phases at triple points.The frequency-dependent thermal signal of ZnO varistors is also studied to present quantitative evaluation of local thermal conductivity of the sample.

  10. Acoustic Imaging Frequency Dynamics of Ferroelectric Domains by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Kun-Yu; Shunji Takekawa; Kenji Kitamura; ZENG Hua-Rong; SONG Hong-Zhang; HUI Sen-Xing; LI Guo-Rong; YIN Qing-Rui; Kiyoshi Shimamura; Chinna Venkadasamy Kannan; Encarnacion Antonia Garcia Villora

    2008-01-01

    We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy. It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.h kHz by AFM-based acoustic microscopy. The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7 kHz to lO kHz, and reached maximum at 8.1 kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.

  11. Direct observation of defect structure in protein crystals by atomic force and transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Devaud, G. (Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)); Furcinitti, P.S. (Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309 (United States)); Fleming, J.C.; Lyon, M.K.; Douglas, K. (Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States))

    1992-09-01

    We have examined the structure of S-layers isolated from {ital Sulfolobus} {ital acidocaldarius} using atomic force microscopy (AFM) and transmission electron microscopy (TEM). From the AFM images, we were able to directly observe individual dimers of the crystal, defects in the crystal structure, and twin boundaries. We have identified two types of boundaries, one defined by a mirror plane and the other by a glide plane. This work shows that twin boundaries are highly structured regions that are directly related to the organization of units within each crystal domain. Projection maps from TEM images have shown that there are significant differences in the final average maps, depending on which side of the sample is adsorbed to the carbon support film. Comparison of AFM images to TEM projection maps has allowed us to relate high magnification views obtained by AFM to the relatively high resolution information obtained by electron microscopy and image processing.

  12. Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001.

    Science.gov (United States)

    Steele, A; Goddard, D; Beech, I B; Tapper, R C; Stapleton, D; Smith, J R

    1998-01-01

    A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure.

  13. Nonenzymatic ligation of an RNA oligonucleotide analyzed by atomic force microscopy.

    Science.gov (United States)

    Pino, Samanta; Biasiucci, Mariano; Scardamaglia, Mattia; Gigli, Giuseppe; Betti, Maria Grazia; Mariani, Carlo; Di Mauro, Ernesto

    2011-05-19

    The products of ligation reaction of a 24 nucleotides long PolyA RNA adsorbed on mica were observed by atomic force microscopy. The occurrence of oligonucleotides at different degrees of polymerization has been quantitatively studied before and after ligation reaction. The microscopy images at the nanoscale show that nonenzymatic ligation of pristine RNA monomers results in the formation of supramolecular aggregates, with prevalence of dimers and tetramers. Analytical conditions were defined allowing the identification, the quantitative evaluation, and their distribution after ligation reaction, also providing an estimate of the degree of hydration of the objects. Such investigation is of particular biological relevance and provides the simplest yet model system for direct investigation of RNA reactions by advanced microscopy.

  14. Surface morphology study on CdZnTe crystals by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, M.; George, M.A.; Burger, A.; Collins, W.E.; Silberman, E. [Fisk Univ., Nashville, TN (United States)

    1993-03-01

    The study of the crystal surface morphology of CdZnTe is important for the understanding of the fundamentals of crystal growth in order to improve the crystal quality which is essential in applications such as substrates for epitaxy or performance of devices, i.e., room temperature nuclear spectrometers. We present a first atomic force microscopy study on CdZnTe. Cleaved (110) surfaces were imaged in the ambient and an atomic layer step structure was revealed. The effects of thermal annealing on the atomic steps together with Te precipitation along these steps are discussed in terms of deformation due to stress relief and the diffusion of tellurium precipitates. 12 refs., 3 figs.

  15. Correction: Number density distribution of solvent molecules on a substrate: a transform theory for atomic force microscopy.

    Science.gov (United States)

    Amano, Ken-Ichi; Liang, Yunfeng; Miyazawa, Keisuke; Kobayashi, Kazuya; Hashimoto, Kota; Fukami, Kazuhiro; Nishi, Naoya; Sakka, Tetsuo; Onishi, Hiroshi; Fukuma, Takeshi

    2016-08-07

    Correction for 'Number density distribution of solvent molecules on a substrate: a transform theory for atomic force microscopy' by Ken-ichi Amano et al., Phys. Chem. Chem. Phys., 2016, 18, 15534-15544.

  16. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy

    Science.gov (United States)

    Siretanu, Igor; van den Ende, Dirk; Mugele, Frieder

    2016-04-01

    Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all materials investigated, namely gibbsite, kaolinite, illite, and Na-montmorillonite of both natural and synthetic origin. Next to regions of perfect crystallinity, we routinely observe extended regions of various types of defects on the surfaces, including vacancies of one or few atoms, vacancy islands, atomic steps, apparently disordered regions, as well as strongly adsorbed seemingly organic and inorganic species. While their exact nature is frequently difficult to identify, our observations clearly highlight the ubiquity of such defects and their relevance for the overall physical and chemical properties of clay nanoparticle-water interfaces.Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all

  17. Atomic force microscopy studies of human rhinovirus topology and molecular forces.

    Science.gov (United States)

    Kienberger, Ferry; Zhu, Rong; Rankl, Christian; Gruber, Hermann J; Blaas, Dieter; Hinterdorfer, Peter

    2010-01-01

    Dynamic force microscopy (DFM) allows for imaging of the structure and assessment of the function of biological specimens in their physiological environment. In DFM, the cantilever is oscillated at a given frequency and touches the sample only at the end of its downward movement. Accordingly, the problem of lateral forces displacing or even destroying biomolecules is virtually inexistent as the contact time and friction forces are greatly reduced. Here, we describe the use of DFM in studies of human rhinovirus serotype 2 (HRV2). The capsid of HRV2 was reproducibly imaged without any displacement of the virus. Release of the genomic RNA from the virions was initiated by exposure to low-pH buffer and snapshots of the extrusion process were obtained. DFM of the single-stranded RNA genome of an HRV showed loops protruding from a condensed RNA core, 20-50 nm in height. The mechanical rigidity of the RNA was determined by single molecule pulling experiments. From fitting RNA stretching curves to the worm-like-chain (WLC) model a persistence length of 1.0+/-0.17 nm was obtained.

  18. Diamagnetic Levitation Cantilever System for the Calibration of Normal Force Atomic Force Microscopy Measurements

    Science.gov (United States)

    Torres, Jahn; Yi, Jin-Woo; Murphy, Colin; Kim, Kyung-Suk

    2011-03-01

    In this presentation we report a novel technique for normal force calibration for Atomic Force Microcopy (AFM) adhesion measurements known as the diamagnetic normal force calibration (D-NFC) system. The levitation produced by the repulsion between a diamagnetic graphite sheet and a set of rare-earth magnets is used in order to produce an oscillation due to an unstable mechanical moment produced by a silicon cantilever supported on the graphite. The measurement of the natural frequency of this oscillation allows for the calculation of the stiffness of the system to three-digit accuracy. The D-NFC response was proven to have a high sensitivity for the structure of water molecules collected on its surface. This in turns allows for the study of the effects of coatings on the structure of surface water. This work was supported by the Coatings/Biofouling Program and the Maritime Sensing Program of the Office of Naval Research as well as the ILIR Program of the Naval Undersea Warfare Center DIVNPT.

  19. Probing the interactions between lignin and inorganic oxides using atomic force microscopy

    Science.gov (United States)

    Wang, Jingyu; Qian, Yong; Deng, Yonghong; Liu, Di; Li, Hao; Qiu, Xueqing

    2016-12-01

    Understanding the interactions between lignin and inorganic oxides has both fundamental and practical importance in industrial and energy fields. In this work, the specific interactions between alkali lignin (AL) and three inorganic oxide substrates in aqueous environment are quantitatively measured using atomic force microscopy (AFM). The results show that the average adhesion force between AL and metal oxide such as Al2O3 or MgO is nearly two times bigger than that between AL and nonmetal oxide such as SiO2 due to the electrostatic difference and cation-π interaction. When 83% hydroxyl groups of AL is blocked by acetylation, the adhesion forces between AL and Al2O3, MgO and SiO2 decrease 43, 35 and 75% respectively, which indicate hydrogen bonds play an important role between AL and inorganic oxides, especially in AL-silica system.

  20. Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

    Directory of Open Access Journals (Sweden)

    Miriam Jaafar

    2012-04-01

    Full Text Available We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode.

  1. Atomic force microscopy characterization of the surface wettability of natural fibres

    Science.gov (United States)

    Pietak, Alexis; Korte, Sandra; Tan, Emelyn; Downard, Alison; Staiger, Mark P.

    2007-01-01

    Natural fibres represent a readily available source of ecologically friendly and inexpensive reinforcement in composites with degradable thermoplastics, however chemical treatments of fibres are required to prepare feasible composites. It is desirable to characterize the surface wettability of fibres after chemical treatment as the polarity of cellulose-based fibres influences compatibility with a polymer matrix. Assessment of the surface wettability of natural fibres using conventional methods presents a challenge as the surfaces are morphologically and chemically heterogeneous, rough, and can be strongly wicking. In this work it is shown that under atmospheric conditions the adhesion force between an atomic force microscopy (AFM) tip and the fibre surface can estimate the water contact angle and surface wettability of the fibre. AFM adhesion force measurements are suitable for the more difficult surfaces of natural fibres and in addition allow for correlations between microstructural features and surface wettability characteristics.

  2. Integrated atomic force microscopy techniques for analysis of biomaterials: Study of membrane proteins

    Science.gov (United States)

    Connelly, Laura S.

    Atomic Force Microscopy (AFM) is the prominent techniques for structural studies of biological materials in physiological relevant fluidic environments. AFM has been used to resolve the three-dimensional (3D) surface structure of cells, membranes, and proteins structures. Ion channels, formed by membrane proteins, are the key structures that control the activity of all living systems. This dissertation focuses on the structural evaluation of membrane proteins through atomic force microscopy. In Part I, AFM is utilized to study one of the most prominent medical issues facing our society, Alzheimer's Disease (AD). AD is a misfolded protein disease characterized by the accumulation of beta-amyloid (Abeta) peptide as senile plaques, progressive neurodegeneration, and memory loss. Recent evidence suggests that AD pathology is linked to the destabilization of cellular ionic homeostasis mediated by toxic channel structures composed of Abeta peptides. Selectively engineered sequences of Abeta were examined by AFM to elucidate the substructures and thus activity Abeta channels. Key residues were evaluated with the intent better understand the exact nature by which these pores conduct electrical and molecular signals, which could aid in identifying potential therapeutic targets for the prevention/treatment of AD. Additionally, AFM was used to analyze brain derived Abeta and newly developed pharmacological agents to study membranes and Abeta. Part II, presents a novel technology that incorporates electrophysiology into the AFM interface, enabling simultaneous imaging and complementary conductance measurements. The activity of ion channels is studied by various techniques, including patch clamp, free standing lipid bilayers, droplet interface bilayers, and supported lipid bilayers. However, direct correlation with channel structures has remained a challenge. The integrated atomic force microscopy system presented offers a solution to this challenge. The functionality of the

  3. Molecular positional order in Langmuir-Blodgett films by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bourdieu, L.; Ronsin, O.; Chatenay, D. (Inst. Curie, Paris (France))

    1993-02-05

    Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules. 22 refs., 4 figs.

  4. Molecular Positional Order in Langmuir-Blodgett Films by Atomic Force Microscopy

    Science.gov (United States)

    Bourdieu, L.; Ronsin, O.; Chatenay, D.

    1993-02-01

    Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules.

  5. Atomic force microscopy: Loading position dependence of cantilever spring constants and detector sensitivity

    Science.gov (United States)

    Vakarelski, Ivan U.; Edwards, Scott A.; Dagastine, Raymond R.; Chan, Derek Y. C.; Stevens, Geoffrey W.; Grieser, Franz

    2007-11-01

    A simple and accurate experimental method is described for determining the effective cantilever spring constant and the detector sensitivity of atomic force microscopy cantilevers on which a colloidal particle is attached. By attaching large (approximately 85μm diameter) latex particles at various positions along the V-shaped cantilevers, we demonstrate how the normal and lateral spring constants as well as the sensitivity vary with loading position. Comparison with an explicit point-load theoretical model has also been used to verify the accuracy of the method.

  6. Wide-area scanner for high-speed atomic force microscopy

    OpenAIRE

    Watanabe, Hiroki; Uchihashi, Takayuki; Kobashi, Toshihide; Shibata, Mikihiro; Nishiyama, Jun; Yasuda, Ryohei; Ando, Toshio

    2013-01-01

    High-speed atomic force microscopy (HS-AFM) has recently been established. The dynamic processes and structural dynamics of protein molecules in action have been successfully visualized using HS-AFM. However, its maximum scan ranges in the X- and Y-directions have been limited to ∼1 μm and ∼4 μm, respectively, making it infeasible to observe the dynamics of much larger samples, including live cells. Here, we develop a wide-area scanner with a maximum XY scan range of ∼46 × 46 μm2 by magnifyin...

  7. Hybridisation of short DNA molecules investigated with in situ atomic force microscopy

    DEFF Research Database (Denmark)

    Holmberg, Maria; Kuhle, A.; Garnaes, J.;

    2003-01-01

    By introducing the complementary DNA (cDNA) strand to a molecular layer of short single stranded DNA (ssDNA), immobilised on a gold surface, we have investigated hybridisation between the two DNA strands through the technique of in situ atomic force microscopy (AFM). Before introduction of c...... the two DNA strands has been studied. Introduction of the cDNA strand resulted in an increase in smoothness and thickness of the molecular layer. Both the increase in order and thickness of the molecular layer can be expected if hybridisation occurs, since double stranded DNA molecules have a more rigid...

  8. Magni: A Python Package for Compressive Sampling and Reconstruction of Atomic Force Microscopy Images

    Directory of Open Access Journals (Sweden)

    Christian Schou Oxvig

    2014-10-01

    Full Text Available Magni is an open source Python package that embraces compressed sensing and Atomic Force Microscopy (AFM imaging techniques. It provides AFM-specific functionality for undersampling and reconstructing images from AFM equipment and thereby accelerating the acquisition of AFM images. Magni also provides researchers in compressed sensing with a selection of algorithms for reconstructing undersampled general images, and offers a consistent and rigorous way to efficiently evaluate the researchers own developed reconstruction algorithms in terms of phase transitions. The package also serves as a convenient platform for researchers in compressed sensing aiming at obtaining a high degree of reproducibility of their research.

  9. A review of the application of atomic force microscopy (AFM) in food science and technology.

    Science.gov (United States)

    Liu, Shaoyang; Wang, Yifen

    2011-01-01

    Atomic force microscopy (AFM) is a powerful nanoscale analysis technique used in food area. This versatile technique can be used to acquire high-resolution sample images and investigate local interactions in air or liquid surroundings. In this chapter, we explain the principles of AFM and review representative applications of AFM in gelatin, casein micelle, carrageenan, gellan gum, starch, and interface. We elucidate new knowledge revealed with AFM as well as ways to use AFM to obtain morphology and rheology information in different food fields.

  10. Immobilization and condensation of DNA with 3-aminopropyltriethoxysilane studied by atomic force microscopy.

    Science.gov (United States)

    Liu, Z; Li, Z; Zhou, H; Wei, G; Song, Y; Wang, L

    2005-06-01

    We used different methods to modify a mica surface with 3-aminopropyltriethoxysilane (APTES), and then used it as substrate to immobilize DNA for atomic force microscopy (AFM) observation. The evaporation method and solution modifying method were investigated and evaluated. The solution modifying method was found to be relatively simple and effective. Using an APTES solution-modified mica surface, DNA immobilization appeared more reproducible and it could be imaged in liquid. The mixed solution of APTES and DNA was dropped directly onto the mica surface for AFM imaging. We found that DNA can condense in APTES water solutions. Toroids, rods and intermediate structures of condensation were captured by AFM.

  11. Loss tangent imaging: Theory and simulations of repulsive-mode tapping atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Proksch, Roger [Asylum Research, Santa Barbara, California 93117 (United States); Yablon, Dalia G. [ExxonMobil Research and Engineering, Annandale, New Jersey (United States)

    2012-02-13

    An expression for loss tangent measurement of a surface in amplitude modulation atomic force microscopy is derived using only the cantilever phase and the normalized cantilever amplitude. This provides a direct measurement of substrate compositional information that only requires tuning of the cantilever resonance to provide quantitative information. Furthermore, the loss tangent expression incorporates both the lost and stored energy into one term that represents a fundamental interpretation of the phase signal in amplitude modulation imaging. Numerical solutions of a cantilever tip interacting with a simple Voigt modeled surface agree with the derived loss tangent to within a few percent.

  12. Atomic Force Microscopy Imaging of Filamentous Aggregates from an N-Terminal Peptide Fragment of Barnase

    Science.gov (United States)

    Shibata-Seki, Teiko; Masai, Junji; Yoshida, Kenji; Sato, Kazuki; Yanagawa, Hiroshi

    1993-06-01

    This paper reports the atomic force microscopy (AFM) imaging of filamentous aggregates derived from an N-terminal peptide fragment of barnase, a ribonuclease from Bacillus amyloliquefaciens. The sample was deposited on a freshly cleaved mica surface and observed in ambient conditions. The overall shapes of the filamentous structures imaged with two different kinds of AFMs were similar to those obtained with a transmission electron microscope (TEM), except that the filaments in AFM images were broader than those in TEM images. This broadening phenomenon characteristic of AFM images was explained in terms of the convolution-type distortion of the specimen diameter by the scanning-tip apex.

  13. DNA flexibility on short length scales probed by atomic force microscopy.

    Science.gov (United States)

    Mazur, Alexey K; Maaloum, Mounir

    2014-02-14

    Unusually high bending flexibility has been recently reported for DNA on short length scales. We use atomic force microscopy (AFM) in solution to obtain a direct estimate of DNA bending statistics for scales down to one helical turn. It appears that DNA behaves as a Gaussian chain and is well described by the wormlike chain model at length scales beyond 3 helical turns (10.5 nm). Below this threshold, the AFM data exhibit growing noise because of experimental limitations. This noise may hide small deviations from the Gaussian behavior, but they can hardly be significant.

  14. Atomic force microscopy based nanoindentation study of onion abaxial epidermis walls in aqueous environment

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Xiaoning; Tittmann, Bernhard [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Kim, Seong H. [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-01-14

    An atomic force microscopy based nanoindentation method was employed to study how the structure of cellulose microfibril packing and matrix polymers affect elastic modulus of fully hydrated primary plant cell walls. The isolated, single-layered abaxial epidermis cell wall of an onion bulb was used as a test system since the cellulose microfibril packing in this cell wall is known to vary systematically from inside to outside scales and the most abundant matrix polymer, pectin, can easily be altered through simple chemical treatments such as ethylenediaminetetraacetic acid and calcium ions. Experimental results showed that the pectin network variation has significant impacts on the cell wall modulus, and not the cellulose microfibril packing.

  15. Elastic-properties measurement at high temperatures through contact resonance atomic force microscopy

    DEFF Research Database (Denmark)

    Marinello, Francesco; Pezzuolo, Andrea; Carmignato, Simone;

    2015-01-01

    Miniaturization of products and need for further improvement of machines performance introduce new serious challenges in materials characterization. In particular non-destructive mechanical testing in the sub-micrometer scale is needed to better understand and improve micro-manufacturing operations...... fast direct and non-destructive measurement of Young's modulus and related surface parameters.In this work an instrument set up for Contact Resonance Atomic Force Microscopy is proposed, where the sample with is coupled to a heating stage and a piezoelectric transducer directly vibrate the cantilever...

  16. State Feedback Control for Adjusting the Dynamic Behavior of a Piezoactuated Bimorph Atomic Force Microscopy Probe

    CERN Document Server

    Orun, Bilal; Basdogan, Cagatay; Guvenc, Levent

    2012-01-01

    We adjust the transient dynamics of a piezo-actuated bimorph Atomic Force Microscopy (AFM) probe using a state feedback controller. This approach enables us to adjust the quality factor and the resonance frequency of the probe simultaneously. First, we first investigate the effect of feedback gains on dynamic response of the probe and then show that the time constant of the probe can be reduced by reducing its quality factor and/or increasing its resonance frequency to reduce the scan error in tapping mode AFM.

  17. Number density distribution of solvent molecules on a substrate: a transform theory for atomic force microscopy.

    Science.gov (United States)

    Amano, Ken-Ichi; Liang, Yunfeng; Miyazawa, Keisuke; Kobayashi, Kazuya; Hashimoto, Kota; Fukami, Kazuhiro; Nishi, Naoya; Sakka, Tetsuo; Onishi, Hiroshi; Fukuma, Takeshi

    2016-06-21

    Atomic force microscopy (AFM) in liquids can measure a force curve between a probe and a buried substrate. The shape of the measured force curve is related to hydration structure on the substrate. However, until now, there has been no practical theory that can transform the force curve into the hydration structure, because treatment of the liquid confined between the probe and the substrate is a difficult problem. Here, we propose a robust and practical transform theory, which can generate the number density distribution of solvent molecules on a substrate from the force curve. As an example, we analyzed a force curve measured by using our high-resolution AFM with a newly fabricated ultrashort cantilever. It is demonstrated that the hydration structure on muscovite mica (001) surface can be reproduced from the force curve by using the transform theory. The transform theory will enhance AFM's ability and support structural analyses of solid/liquid interfaces. By using the transform theory, the effective diameter of a real probe apex is also obtained. This result will be important for designing a model probe of molecular scale simulations.

  18. Thermochemical nanolithography fabrication and atomic force microscopy characterization of functional nanostructures

    Science.gov (United States)

    Wang, Debin

    This thesis presents the development of a novel atomic force microscope (AFM) based nanofabrication technique termed as thermochemical nanolithography (TCNL). TCNL uses a resistively heated AFM cantilever to thermally activate chemical reactions on a surface with nanometer resolution. This technique can be used for fabrication of functional nanostructures that are appealing for various applications in nanofluidics, nanoelectronics, nanophotonics, and biosensing devices. This thesis research is focused on three main objectives. The first objective is to study the fundamentals of TCNL writing aspects. We have conducted a systematic study of the heat transfer mechanism using finite element analysis modeling, Raman spectroscopy, and local glass transition measurement. In addition, based on thermal kinetics analysis, we have identified several key factors to achieve high resolution fabrication of nanostructures during the TCNL writing process. The second objective is to demonstrate the use of TCNL on a variety of systems and thermochemical reactions. We show that TCNL can be employed to (1) modify the wettability of a polymer surface at the nanoscale, (2) fabricate nanoscale templates on polymer films for assembling nano-objects, such as proteins and DNA, (3) fabricate conjugated polymer semiconducting nanowires, and (4) reduce graphene oxide with nanometer resolution. The last objective is to characterize the TCNL nanostructures using AFM based methods, such as friction force microscopy, phase imaging, electric force microscopy, and conductive AFM. We show that they are useful for in situ characterization of nanostructures, which is particularly challenging for conventional macroscopic analytical tools, such as Raman spectroscopy, IR spectroscopy, and fluorescence microscopy.

  19. Gold-decorated highly ordered self-organized grating-like nanostructures on Ge surface: Kelvin probe force microscopy and conductive atomic force microscopy studies

    Science.gov (United States)

    Alam Mollick, Safiul; Kumar, Mohit; Singh, Ranveer; Satpati, Biswarup; Ghose, Debabrata; Som, Tapobrata

    2016-10-01

    Nanoarchitecture by atomic manipulation is considered to be one of the emerging trends in advanced functional materials. It has a gamut of applications to offer in nanoelectronics, chemical sensing, and nanobiological science. In particular, highly ordered one-dimensional semiconductor nanostructures fabricated by self-organization methods are in high demand for their high aspect ratios and large number of applications. An efficient way of fabricating semiconductor nanostructures is by molecular beam epitaxy, where atoms are added to a crystalline surface at an elevated temperature during growth, yielding the desired structures in a self-assembled manner. In this article, we offer a room temperature process, in which atoms are sputtered away by ion impacts. Using gold ion implantation, the present study reports on the formation of highly ordered self-organized long grating-like nanostructures, with grooves between them, on a germanium surface. The ridges of the patterns are shown to have flower-like protruding nanostructures, which are mostly decorated by gold atoms. By employing local probe microscopic techniques like Kelvin probe force microscopy and conductive atomic force microscopy, we observe a spatial variation in the work function and different nanoscale electrical conductivity on the ridges of the patterns and the grooves between them, which can be attributed to gold atom decorated ridges. Thus, the architecture presented offers the advantage of using the patterned germanium substrates as periodic arrays of conducting ridges and poorly conducting grooves between them.

  20. High-resolution dynamic atomic force microscopy in liquids with different feedback architectures

    Directory of Open Access Journals (Sweden)

    John Melcher

    2013-02-01

    Full Text Available The recent achievement of atomic resolution with dynamic atomic force microscopy (dAFM [Fukuma et al., Appl. Phys. Lett. 2005, 87, 034101], where quality factors of the oscillating probe are inherently low, challenges some accepted beliefs concerning sensitivity and resolution in dAFM imaging modes. Through analysis and experiment we study the performance metrics for high-resolution imaging with dAFM in liquid media with amplitude modulation (AM, frequency modulation (FM and drive-amplitude modulation (DAM imaging modes. We find that while the quality factors of dAFM probes may deviate by several orders of magnitude between vacuum and liquid media, their sensitivity to tip–sample forces can be remarkable similar. Furthermore, the reduction in noncontact forces and quality factors in liquids diminishes the role of feedback control in achieving high-resolution images. The theoretical findings are supported by atomic-resolution images of mica in water acquired with AM, FM and DAM under similar operating conditions.

  1. Measurements on hydrophobic and hydrophilic surfaces using a porous gamma alumina nanoparticle aggregate mounted on Atomic Force Microscopy cantilevers

    NARCIS (Netherlands)

    Das, Theerthankar; Becker, Thomas; Nair, Balagopal N.

    2010-01-01

    Atomic Force Microscopy (AFM) measurements are extensively used for a detailed understanding of molecular and surface forces. In this study, we present a technique for measuring such forces, using an AFM cantilever attached with a porous gamma alumina nanoparticle aggregate. The modified cantilever

  2. Understanding 2D atomic resolution imaging of the calcite surface in water by frequency modulation atomic force microscopy

    Science.gov (United States)

    Tracey, John; Miyazawa, Keisuke; Spijker, Peter; Miyata, Kazuki; Reischl, Bernhard; Federici Canova, Filippo; Rohl, Andrew L.; Fukuma, Takeshi; Foster, Adam S.

    2016-10-01

    Frequency modulation atomic force microscopy (FM-AFM) experiments were performed on the calcite (10\\bar{1}4) surface in pure water, and a detailed analysis was made of the 2D images at a variety of frequency setpoints. We observed eight different contrast patterns that reproducibly appeared in different experiments and with different measurement parameters. We then performed systematic free energy calculations of the same system using atomistic molecular dynamics to obtain an effective force field for the tip-surface interaction. By using this force field in a virtual AFM simulation we found that each experimental contrast could be reproduced in our simulations by changing the setpoint, regardless of the experimental parameters. This approach offers a generic method for understanding the wide variety of contrast patterns seen on the calcite surface in water, and is generally applicable to AFM imaging in liquids.

  3. Fundamental aspects of electric double layer force-distance measurements at liquid-solid interfaces using atomic force microscopy

    Science.gov (United States)

    Black, Jennifer M.; Zhu, Mengyang; Zhang, Pengfei; Unocic, Raymond R.; Guo, Daqiang; Okatan, M. Baris; Dai, Sheng; Cummings, Peter T.; Kalinin, Sergei V.; Feng, Guang; Balke, Nina

    2016-01-01

    Atomic force microscopy (AFM) force-distance measurements are used to investigate the layered ion structure of Ionic Liquids (ILs) at the mica surface. The effects of various tip properties on the measured force profiles are examined and reveal that the measured ion position is independent of tip properties, while the tip radius affects the forces required to break through the ion layers as well as the adhesion force. Force data is collected for different ILs and directly compared with interfacial ion density profiles predicted by molecular dynamics. Through this comparison it is concluded that AFM force measurements are sensitive to the position of the ion with the larger volume and mass, suggesting that ion selectivity in force-distance measurements are related to excluded volume effects and not to electrostatic or chemical interactions between ions and AFM tip. The comparison also revealed that at distances greater than 1 nm the system maintains overall electroneutrality between the AFM tip and sample, while at smaller distances other forces (e.g., van der waals interactions) dominate and electroneutrality is no longer maintained. PMID:27587276

  4. Interaction of cationic hydrophobic surfactants at negatively charged surfaces investigated by atomic force microscopy.

    Science.gov (United States)

    McNamee, Cathy E; Butt, Hans-Jürgen; Higashitani, Ko; Vakarelski, Ivan U; Kappl, Michael

    2009-10-06

    Atomic force microscopy was used to study the adsorption of the surfactant octadecyl trimethyl ammonium chloride (C18TAC) at a low concentration (0.03 mM) to negatively charged surfaces in water. Atomic force microscopy tips were functionalized with dimethyloctadecyl(3-tripropyl)ammonium chloride (C18TAC-si) or N-trimethoxysilylpropyl-N,N,N-trimethylammomium chloride (hydrophilpos-si) to facilitate imaging of the adsorbed surfactant without artifacts. Tapping mode images and force measurements revealed C18TAC patches, identified as partial surfactant bilayers or hemimicelles. The forces controlling the adsorption process of the C18TAC to a negatively charged surface were investigated by measuring the forces between a C18TAC-si or a hydrophilpos-si tip and a silica surface in the presence of varying concentrations of either NaCl or NaNO3. Screening of forces with an increasing NaCl concentration was observed for the C18TAC-si and hydrophilpos-si tips, proving an electrostatic contribution. Screening was also observed for the hydrophilpos-si tip in NaNO3, whereas a long-range attraction was observed for the C18TAC-si tip for all NaNO3 concentrations. These results indicate that screening of the forces for the C18TAC-si tip depended on the type and/or size of the anion, possibly due to a different probability of the anions to enter the silane layers. The interaction of C18TAC patches with C18TAC-si tips in the presence of NaCl and the interaction of the patches with hydrophilpos-si tips in either NaCl or NaNO3 were repulsive and independent of the number of force curves measured, indicating a stable, positively charged C18TAC patch. However, the forces measured between the patches and a C18TAC-si tip in NaNO3 depended on the number of force curves measured, indicating a change in patch structure induced by the first interaction.

  5. Experimental validation of atomic force microscopy-based cell elasticity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Andrew R; Charras, G T, E-mail: g.charras@ucl.ac.uk [London Centre for Nanotechnology, University College London, London WC1H 0AH (United Kingdom)

    2011-08-26

    Atomic force microscopy (AFM) is widely used for measuring the elasticity of living cells yielding values ranging from 100 Pa to 100 kPa, much larger than those obtained using bead-tracking microrheology or micropipette aspiration (100-500 Pa). AFM elasticity measurements appear dependent on tip geometry with pyramidal tips yielding elasticities 2-3 fold larger than spherical tips, an effect generally attributed to the larger contact area of spherical tips. In AFM elasticity measurements, experimental force-indentation curves are analyzed using contact mechanics models that infer the tip-cell contact area from the tip geometry and indentation depth. The validity of these assumptions has never been verified. Here we utilize combined AFM-confocal microscopy of epithelial cells expressing a GFP-tagged membrane marker to directly characterize the indentation geometry and measure the indentation depth. Comparison with data derived from AFM force-indentation curves showed that the experimentally measured contact area for spherical tips agrees well with predicted values, whereas for pyramidal tips, the contact area can be grossly underestimated at forces larger than {approx} 0.2 nN leading to a greater than two-fold overestimation of elasticity. These data suggest that a re-examination of absolute cellular elasticities reported in the literature may be necessary and we suggest guidelines for avoiding elasticity measurement artefacts introduced by extraneous cantilever-cell contact.

  6. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy.

    Science.gov (United States)

    Siretanu, Igor; van den Ende, Dirk; Mugele, Frieder

    2016-04-21

    Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all materials investigated, namely gibbsite, kaolinite, illite, and Na-montmorillonite of both natural and synthetic origin. Next to regions of perfect crystallinity, we routinely observe extended regions of various types of defects on the surfaces, including vacancies of one or few atoms, vacancy islands, atomic steps, apparently disordered regions, as well as strongly adsorbed seemingly organic and inorganic species. While their exact nature is frequently difficult to identify, our observations clearly highlight the ubiquity of such defects and their relevance for the overall physical and chemical properties of clay nanoparticle-water interfaces.

  7. Atomic Force Microscopy Study of the Interactions of Indolicidin with Model Membranes and DNA.

    Science.gov (United States)

    Fojan, Peter; Gurevich, Leonid

    2017-01-01

    The cell membrane is the first barrier and quite often the primary target that antimicrobial peptides (AMPs) have to destroy or penetrate to fulfill their mission. Upon penetrating through the membrane, the peptides can further attack intracellular targets, in particular DNA. Studying the interaction of an antimicrobial peptide with a cell membrane and DNA holds keys to understanding its killing mechanisms. Commonly, these interactions are studied by using optical or scanning electron microscopy and appropriately labeled peptides. However, labeling can significantly affect the hydrophobicity, conformation, and size of the peptide, hence altering the interaction significantly. Here, we describe the use of atomic force microscopy (AFM) for a label-free study of the interactions of peptides with model membranes under physiological conditions and DNA as a possible intracellular target.

  8. Quantification of tip-broadening in non-contact atomic force microscopy with carbon nanotube tips

    DEFF Research Database (Denmark)

    Meinander, Kristoffer; Jensen, Thomas N.; Simonsen, Soren B.;

    2012-01-01

    Carbon nanotube terminated atomic force microscopy (AFM) probes have been used for the imaging of 5 nm wide surface supported Pt nanoclusters by non-contact (dynamic mode) AFM in an ultra-high vacuum. The results are compared to AFM measurements done with conventional Si-tips, as well...... as with transmission electron microscopy images, which give accurate measures for cluster widths. Despite their ideal aspect ratio, tip-broadening is concluded to be a severe problem even when imaging with carbon nanotube tips, which overestimates the cluster width by several times the nominal width of the nanotube...... tip. This broadening is attributed to a bending of the carbon nanotubes, and not to pure geometrical factors, which coincidentally results in a significant improvement for relative height measurements of tightly spaced high aspect ratio structures, as compared to what can be achieved...

  9. An assessment of the formation of electrodeposited scales using scanning electron and atomic force microscopy

    Science.gov (United States)

    Morizot, A. P.; Neville, A.; Taylor, J. D.

    2002-04-01

    The deposition of insoluble salts onto surfaces in process systems represents an important operational problem. Mineral scale formation (e.g. CaCO 3 and BaSO 4) can result from fluid streams becoming supersaturated when incompatible waters combine (e.g. in oil recovery) or can be formed when cathodic protection is applied and electrodeposition occurs. In this study, electrodeposition is studied on metal rotating disk electrodes (RDE) in artificial seawater under static conditions and under rotation at 400 rpm. Also, a Ca-free brine and a Mg-free brine of the same dissolved solids level were used in static tests. The focus of the study is the assessment of the electrochemical response of the system under potentiostatic control and correlation of the current versus time measurements to the characteristics of the scale determined via scanning electron microscopy and atomic force microscopy analysis.

  10. Local analysis of semiconductor nanoobjects by scanning tunneling atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Natalia A. Lashkova

    2015-03-01

    Full Text Available The features of the current–voltage (I–V measurements in local regions of semiconductor nanostructures by conductive atomic force microscopy (AFM are discussed. The standard procedure of I–V measurements in conductive AFM leads not infrequently to the thermomechanical stresses in the sample and, as a consequence, nonreproducibility and unreliability of measurements. The technique of obtaining reproducible current–voltage characteristics is proposed. According to the technique, a series of measurements of the selected scanning area in the mode of conducting AFM should be taken, each at the certain value of the potential. According to a series of scans I–V curve at a particular point (for any point of the scan was plotted. The program is realized in the LabVIEW software. The proposed method extends the capabilities of scanning probe microscopy in the diagnosis of nanostructured semiconductor materials.

  11. Morphology of Platinum Nanowire Array Electrodeposited Within Anodic Aluminium Oxide Template Characterized by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    孔令斌; 陆梅; 李梦轲; 郭新勇; 力虎林

    2003-01-01

    Uniform platinum nanowires were synthesized by electrodepositing the platinum under a very low altering current frequency (20Hz) and increasing voltage (5-15 V) in the pores of anodic aluminium oxide (AAO) template.Atomic force microscopy observation indicates that the template membranes we obtained have hexagonally closepacked nanochannels. The platinum nanowires have highly ordered arrays after partially dissolving the aluminium oxide membrane. With the increasing dissolving time, the platinum nanowire array collapsed. A concave topography of the aluminium substrate was observed after the aluminium oxide membrane was dissolved completely and the platinum nanowires were released from the template. Platinum nanowires were also characterized by transmission electron microscopy and the phase structure of the Al/AAO/Pt composite was proven by x-ray diffraction.

  12. Assemblies of pore-forming toxins visualized by atomic force microscopy.

    Science.gov (United States)

    Yilmaz, Neval; Kobayashi, Toshihide

    2016-03-01

    A number of pore-forming toxins (PFTs) can assemble on lipid membranes through their specific interactions with lipids. The oligomeric assemblies of some PFTs have been successfully revealed either by electron microscopy (EM) and/or atomic force microscopy (AFM). Unlike EM, AFM imaging can be performed under physiological conditions, enabling the real-time visualization of PFT assembly and the transition from the prepore state, in which the toxin does not span the membrane, to the pore state. In addition to characterizing PFT oligomers, AFM has also been used to examine toxin-induced alterations in membrane organization. In this review, we summarize the contributions of AFM to the understanding of both PFT assembly and PFT-induced membrane reorganization. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.

  13. The nanostructure and microstructure of steels: Electrochemical Tafel behaviour and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Valeria A. [Departamento de Farmacia-Bioquimica, Faculdades Federais Integradas de Diamantina, FAFEID, Rua da Gloria, 187 Centro 39100-000 Diamantina, Minas Gerais (Brazil); Paquim, Ana M. Chiorcea [Departamento de Quimica, Universidade de Coimbra, 3004-535 Coimbra (Portugal); Cavaleiro, Albano [Departamento de Engenharia Mecanica, Universidade de Coimbra, 3030 Coimbra (Portugal); Brett, Christopher M.A. [Departamento de Quimica, Universidade de Coimbra, 3004-535 Coimbra (Portugal)]. E-mail: brett@ci.uc.pt

    2005-12-15

    The influence of chemical composition and heat treatment on a low-carbon steel, chromium steel and high speed steel has been examined by polarisation curves and electrochemical parameters deduced from the Tafel plots. The electrochemical corrosion resistance, which is small between the as-received steels become greater after heat treatment, following the order: carbon steel < chromium steel {approx} high speed steel. To explain these differences, the nano- and microstructure of the steels has been characterized by the ex situ techniques of atomic force microscopy and optical microscopy, before and after surface etching with Nital (a solution of 5% HNO{sub 3} in ethanol). This causes preferential attack of the ferrite phases showing the carbide phases more clearly. From these nanostructural studies it was possible to better understand why the passive films formed on chromium steel and high speed steel have superior protective properties to those formed on carbon steel.

  14. Application of atomic force microscopy on rapid determination of microorganisms for food safety.

    Science.gov (United States)

    Yang, H; Wang, Y

    2008-10-01

    Rapid detection and quantification of microorganisms is important for food quality, safety, and security. In this field, nanotechnology appears to be promising in its ability to characterize an individual microorganism and detect heterogeneous distribution of microbes in food samples. In this study, atomic force microscopy (AFM), a nanotechnology tool, was used to investigate Escherichia coli (E. coli) qualitatively and quantitatively. E. coli strains B and K12 were used as surrogates to represent pathogenic strains, such as E. coli O157: H7. The results from AFM were compared with those from scanning/transmission electron microscopy (SEM/TEM). The qualitative determination was obtained using morphology and characteristic parameters from AFM images, and the quantitative determination was obtained by calculating the microorganisms in AFM images. The results show that AFM provides a new approach for rapid determination of microorganisms for food safety.

  15. Mechanical properties of graphene cantilever from atomic force microscopy and density functional theory.

    Science.gov (United States)

    Rasuli, R; Iraji Zad, A; Ahadian, M M

    2010-05-07

    We have studied the mechanical properties of a few-layer graphene cantilever (FLGC) using atomic force microscopy (AFM). The mechanical properties of the suspended FLGC over an open hole have been derived from the AFM data. Force displacement curves using the Derjaguin-Müller-Toporov (DMT) and the massless cantilever beam models yield a Young modulus of E(c) approximately 37, E(a) approximately 0.7 TPa and a Hamakar constant of approximately 3 x 10( - 18) J. The threshold force to shear the FLGC was determined from a breaking force and modeling. In addition, we studied a graphene nanoribbon (GNR), which is a system similar to the FLGC; using density functional theory (DFT). The in-plane Young's modulus for the GNRs were calculated from the DFT outcomes approximately 0.82 TPa and the results were compared with the experiment. We found that the Young's modulus and the threshold shearing force are dependent on the direction of applied force and the values are different for zigzag edge and armchair edge GNRs.

  16. Dynamic light scattering and atomic force microscopy techniques for size determination of polyurethane nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Giehl Zanetti-Ramos, Betina [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas (Brazil)], E-mail: betinagzramos@pq.cnpq.br; Beddin Fritzen-Garcia, Mauricia [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas (Brazil); Schweitzer de Oliveira, Cristian; Avelino Pasa, Andre [Laboratorio de Filmes Finos e Superficie, Departamento de Fisica (Brazil); Soldi, Valdir [Grupo de Estudos em Materiais Polimericos, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Borsali, Redouane [Centre de Recherche sur les Macromolecules Vegetales CERMAV/CNRS, 38041 - Grenoble (France); Creczynski-Pasa, Tania Beatriz [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas (Brazil)

    2009-03-01

    Nanoparticles have applications in various industrial fields principally in drug delivery. Nowadays, there are several processes for manufacturing colloidal polymeric systems and methods of preparation as well as of characterization. In this work, Dynamic Light Scattering and Atomic Force Microscopy techniques were used to characterize polyurethane nanoparticles. The nanoparticles were prepared by miniemulsion technique. The lipophilic monomers, isophorone diisocyanate (IPDI) and natural triol, were emulsified in water containing surfactant. In some formulations the poly(ethylene glycol) was used as co-monomer to obtain the hydrophilic and pegylated nanoparticles. Polyurethane nanoparticles observed by atomic force microscopy (AFM) were spherical with diameter around 209 nm for nanoparticles prepared without PEG. From AFM imaging two populations of nanoparticles were observed in the formulation prepared with PEG (218 and 127 nm) while dynamic light scattering (DLS) measurements showed a monodisperse size distribution around 250 nm of diameters for both formulations. The polydispersity index of the formulations and the experimental procedures could influence the particle size determination with these techniques.

  17. Atomic force microscopy fishing and mass spectrometry identification of gp120 on immobilized aptamers

    Directory of Open Access Journals (Sweden)

    Ivanov YD

    2014-10-01

    Full Text Available Yuri D Ivanov,1 Natalia S Bukharina,1 Tatyana O Pleshakova,1 Pavel A Frantsuzov,1 Elena Yu Andreeva,1 Anna L Kaysheva,1,2 Victor G Zgoda,1 Alexander A Izotov,1 Tatyana I Pavlova,1 Vadim S Ziborov,1 Sergey P Radko,1 Sergei A Moshkovskii,1 Alexander I Archakov1 1Department of Personalized Medicine, Orekhovich Institute of Biomedical Chemistry of the Russian Academy of Medical Sciences, Moscow, Russia; 2PostgenTech Ltd., Moscow, Russia Abstract: Atomic force microscopy (AFM was applied to carry out direct and label-free detection of gp120 human immunodeficiency virus type 1 envelope glycoprotein as a target protein. This approach was based on the AFM fishing of gp120 from the analyte solution using anti-gp120 aptamers immobilized on the AFM chip to count gp120/aptamer complexes that were formed on the chip surface. The comparison of image contrasts of fished gp120 against the background of immobilized aptamers and anti-gp120 antibodies on the AFM images was conducted. It was shown that an image contrast of the protein/aptamer complexes was two-fold higher than the contrast of the protein/antibody complexes. Mass spectrometry identification provided an additional confirmation of the target protein presence on the AFM chips after biospecific fishing to avoid any artifacts. Keywords: gp120 HIV-1 envelope glycoprotein, aptamer, atomic force microscopy, mass spectrometry

  18. Quantitative characterization of biomolecular assemblies and interactions using atomic force microscopy.

    Science.gov (United States)

    Yang, Yong; Wang, Hong; Erie, Dorothy A

    2003-02-01

    Atomic force microscopy (AFM) has been applied in many biological investigations in the past 15 years. This review focuses on the application of AFM for quantitatively characterizing the structural and thermodynamic properties of protein-protein and protein-nucleic acid complexes. AFM can be used to determine the stoichiometries and association constants of multiprotein assemblies and to quantify changes in conformations of proteins and protein-nucleic acid complexes. In addition, AFM in solution permits the observation of the dynamic properties of biomolecular complexes and the measurement of intermolecular forces between biomolecules. Recent advances in cryogenic AFM, AFM on two-dimensional crystals, carbon nanotube probes, solution imaging, high-speed AFM, and manipulation capabilities enhance these applications by improving AFM resolution and the dynamic and operative capabilities of the AFM. These developments make AFM a powerful tool for investigating the biomolecular assemblies and interactions that govern gene regulation.

  19. Quantitative measurement of indentation hardness and modulus of compliant materials by atomic force microscopy

    Science.gov (United States)

    Passeri, D.; Bettucci, A.; Biagioni, A.; Rossi, M.; Alippi, A.; Lucci, M.; Davoli, I.; Berezina, S.

    2008-06-01

    An atomic force microscopy (AFM) based technique is proposed for the characterization of both indentation modulus and hardness of compliant materials. A standard AFM tip is used as an indenter to record force versus indentation curves analogous to those obtained in standard indentation tests. In order to overcome the lack of information about the apex geometry, the proposed technique requires calibration using a set of reference samples whose mechanical properties have been previously characterized by means of an independent technique, such as standard indentation. Due to the selected reference samples, the technique has been demonstrated to allow reliable measurements of indentation modulus and hardness in the range of 0.3-4.0GPa and 15-250MPa, respectively.

  20. Analytical method for parameterizing the random profile components of nanosurfaces imaged by atomic force microscopy

    CERN Document Server

    Mirsaidov, Utkur; Polyakov, Yuriy S; Misurkin, Pavel I; Musaev, Ibrahim; Polyakov, Sergey V

    2010-01-01

    The functional properties of many technological surfaces in biotechnology, electronics, and mechanical engineering depend to a large degree on the individual features of their nanoscale surface texture, which in turn are a function of the surface manufacturing process. Among these features, the surface irregularities and self-similarity structures at different spatial scales, especially in the range of 1 to 100 nm, are of high importance because they greatly affect the surface interaction forces acting at a nanoscale distance. An analytical method for parameterizing the surface irregularities and their correlations in nanosurfaces imaged by atomic force microscopy (AFM) is proposed. In this method, flicker noise spectroscopy - a statistical physics approach - is used to develop six nanometrological parameters characterizing the high-frequency contributions of jump- and spike-like irregularities into the surface texture. These contributions reflect the stochastic processes of anomalous diffusion and inertial e...

  1. Electron transport through supported biomembranes at the nanoscale by conductive atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Casuso, I [Department Electronica, Universitat de Barcelona and Laboratori de Nanobioenginyeria-IBEC, Parc CientIfic de Barcelona, Barcelona (Spain); Fumagalli, L [Department Electronica, Universitat de Barcelona and Laboratori de Nanobioenginyeria-IBEC, Parc CientIfic de Barcelona, Barcelona (Spain); Samitier, J [Department Electronica, Universitat de Barcelona and Laboratori de Nanobioenginyeria-IBEC, Parc CientIfic de Barcelona, Barcelona (Spain); Padros, E [Unitat de BiofIsica, Departamento de BioquImica i de Biologia Molecular, Facultat de Medicina i Centre d' Estudis en BiofIsica, Universitat Autonoma de Barcelona, Barcelona (Spain); Reggiani, L [CNR-INFM National Nanotechnology Laboratory, Dipartimento di Ingegneria dell' Innovazione, Universita di Lecce, Lecce (Italy); Akimov, V [CNR-INFM National Nanotechnology Laboratory, Dipartimento di Ingegneria dell' Innovazione, Universita di Lecce, Lecce (Italy); Gomila, G [Department Electronica, Universitat de Barcelona and Laboratori de Nanobioenginyeria-IBEC, Parc CientIfic de Barcelona, Barcelona (Spain)

    2007-11-21

    We present a reliable methodology to perform electron transport measurements at the nanoscale on supported biomembranes by conductive atomic force microscopy (C-AFM). It allows measurement of both (a) non-destructive conductive maps and (b) force controlled current-voltage characteristics in wide voltage bias range in a reproducible way. Tests experiments were performed on purple membrane monolayers, a two-dimensional (2D) crystal lattice of the transmembrane protein bacteriorhodopsin. Non-destructive conductive images show uniform conductivity of the membrane with isolated nanometric conduction defects. Current-voltage characteristics under different compression conditions show non-resonant tunneling electron transport properties, with two different conduction regimes as a function of the applied bias, in excellent agreement with theoretical predictions. This methodology opens the possibility for a detailed study of electron transport properties of supported biological membranes, and of soft materials in general.

  2. Dynamics of a disturbed sessile drop measured by atomic force microscopy (AFM).

    Science.gov (United States)

    McGuiggan, Patricia M; Grave, Daniel A; Wallace, Jay S; Cheng, Shengfeng; Prosperetti, Andrea; Robbins, Mark O

    2011-10-04

    A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

  3. Nanopatterning of adsorbed 3-aminepropyltriethyoxysilane film by an atomic force microscopy tip

    Science.gov (United States)

    Wang, L.; Sun, Y.; Li, Z.

    2010-11-01

    In this work, we demonstrated a simple route to pattern nanostructures on the 3-aminopropyltriethoxysilane (APTES) film adsorbed on mica using nanolithography technology. Various nanopatterns (linear, foursquare and triangular) could be achieved by controlling and designing the scanning direction of AFM tip. Also, it was found that the adsorbed APTES film could be induced to rearrange into a bilayer structure. The parameters for the formation of nanostructures were investigated by contact mode atomic force microscopy (AFM). The results indicated that the height of the nanopatterns built on the adsorbed film increased with the decrease of the depth of a tip pushed in. The driving force for the formation of nanopatterns is the combination of the capillarity and inducement action of a tip to APTES molecules. The results presented in this work will improve our understanding to the formation process of short-chain alkoxysilane molecular bilayer and multilayer on mica in a position-selective way.

  4. Metrology of electromagnetic static actuation of MEMS microbridge using atomic force microscopy.

    Science.gov (United States)

    Moczała, M; Majstrzyk, W; Sierakowski, A; Dobrowolski, R; Grabiec, P; Gotszalk, T

    2016-05-01

    The objective of this paper is to describe application of atomic force microscopy (AFM) for characterization and calibration of static deflection of electromagnetically and/or thermally actuated micro-electromechanical (MEMS) bridge. The investigated MEMS structure is formed by a silicon nitride bridge and a thin film metal path enabling electromagnetic and/or thermal deflection actuation. We present how static microbridge deflection can be measured using contact mode AFM technology with resolution of 0.05nm in the range of up to tens of nm. We also analyze, for very small structure deflections and under defined and controlled load force varied in the range up to ca. 32nN, properties of thermal and electromagnetical microbridge deflection actuation schemes.

  5. Modification and characterization of thin silicon gate oxides using conducting atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kremmer, S.; Peissl, S.; Teichert, C.; Kuchar, F.; Hofer, H

    2003-09-15

    Conducting atomic force microscopy (C-AFM) is used for the anodic oxidation on thermally grown gate oxide samples. The electric field distribution during the oxidation process is studied by computer simulations as function of tip radius, thermal oxide thickness and water film coverage. The results are compared with the experimental oxidation experiments. It is shown that the tip radius and its nano-roughness play an important role for the shape of the protrusions obtained by oxidation. For smooth tips, which do not exhibit high nano-roughness, formation of ring structures can be observed. For tips with higher nano-roughness, the ring structure formation is suppressed. From a comparison of the electric field distributions within the oxide with the experimental data, we concluded that the electric field near the oxide/tip interface is the driving force during the anodic oxidation process.

  6. Techniques for imaging human metaphase chromosomes in liquid conditions by atomic force microscopy

    Science.gov (United States)

    Ushiki, Tatsuo; Shigeno, Masatsugu; Hoshi, Osamu

    2008-09-01

    The purpose of this study was to obtain three-dimensional images of wet chromosomes by atomic force microscopy (AFM) in liquid conditions. Human metaphase chromosomes—obtained either by chromosome spreads or by an isolation technique—were observed in a dynamic mode by AFM in a buffer solution. Under suitable operating conditions with a soft triangular cantilever (with the spring constant of 0.08-0.4 N m-1), clear images of fixed chromosomes in the chromosome spread were obtained by AFM. For imaging isolated chromosomes with the height of more than 400 nm, a cantilever with a high aspect ratio probing tip was required. The combination of a Q-control system and the sampling intelligent scan (SIS) system in dynamic force mode AFM was useful for obtaining high-quality images of the isolated chromosomes, in which globular or cord-like structures about 50 nm thick were clearly observed on the surface of each chromatid.

  7. Nanocharacterization and nanofabrication of a Nafion thin film in liquids by atomic force microscopy.

    Science.gov (United States)

    Umemura, Kazuo; Wang, Tong; Hara, Masahiko; Kuroda, Reiko; Uchida, On; Nagai, Masayuki

    2006-03-28

    We demonstrated the nanocharacterization and nanofabrication of a Nafion thin film using atomic force microscopy (AFM). AFM images showed that the Nafion molecules form nanoclusters in water, in 5% methanol, and in acetic acid. Young's modulus E of a Nafion film was estimated by sequential force curve measurements in water and in 5% methanol on one sample surface. Ewater/E5% methanol was 1.75 +/- 0.40, so the film was much softer in 5% methanol than in water. Even when solvent was replaced from 5% methanol to water, Young's modulus was not recovered soon. We showed the first example of the mechanical properties of a Nafion film on the nanoscale. Furthermore, we succeeded in fabricating 3D nanostructures on a Nafion surface by AFM nanolithography in liquids. Our results showed the new potential of the AFM nanolithography of a polymer film by softening the molecules in liquids.

  8. Passive microrheology of soft materials with atomic force microscopy: A wavelet-based spectral analysis

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Torres, C.; Streppa, L. [CNRS, UMR5672, Laboratoire de Physique, Ecole Normale Supérieure de Lyon, 46 Allée d' Italie, Université de Lyon, 69007 Lyon (France); Arneodo, A.; Argoul, F. [CNRS, UMR5672, Laboratoire de Physique, Ecole Normale Supérieure de Lyon, 46 Allée d' Italie, Université de Lyon, 69007 Lyon (France); CNRS, UMR5798, Laboratoire Ondes et Matière d' Aquitaine, Université de Bordeaux, 351 Cours de la Libération, 33405 Talence (France); Argoul, P. [Université Paris-Est, Ecole des Ponts ParisTech, SDOA, MAST, IFSTTAR, 14-20 Bd Newton, Cité Descartes, 77420 Champs sur Marne (France)

    2016-01-18

    Compared to active microrheology where a known force or modulation is periodically imposed to a soft material, passive microrheology relies on the spectral analysis of the spontaneous motion of tracers inherent or external to the material. Passive microrheology studies of soft or living materials with atomic force microscopy (AFM) cantilever tips are rather rare because, in the spectral densities, the rheological response of the materials is hardly distinguishable from other sources of random or periodic perturbations. To circumvent this difficulty, we propose here a wavelet-based decomposition of AFM cantilever tip fluctuations and we show that when applying this multi-scale method to soft polymer layers and to living myoblasts, the structural damping exponents of these soft materials can be retrieved.

  9. Nanostructure and force spectroscopy analysis of human peripheral blood CD4+ T cells using atomic force microscopy.

    Science.gov (United States)

    Hu, Mingqian; Wang, Jiongkun; Cai, Jiye; Wu, Yangzhe; Wang, Xiaoping

    2008-09-12

    To date, nanoscale imaging of the morphological changes and adhesion force of CD4(+) T cells during in vitro activation remains largely unreported. In this study, we used atomic force microscopy (AFM) to study the morphological changes and specific binding forces in resting and activated human peripheral blood CD4(+) T cells. The AFM images revealed that the volume of activated CD4(+) T cells increased and the ultrastructure of these cells also became complex. Using a functionalized AFM tip, the strength of the specific binding force of the CD4 antigen-antibody interaction was found to be approximately three times that of the unspecific force. The adhesion forces were not randomly distributed over the surface of a single activated CD4(+) T cell, indicated that the CD4 molecules concentrated into nanodomains. The magnitude of the adhesion force of the CD4 antigen-antibody interaction did not change markedly with the activation time. Multiple bonds involved in the CD4 antigen-antibody interaction were measured at different activation times. These results suggest that the adhesion force involved in the CD4 antigen-antibody interaction is highly selective and of high affinity.

  10. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.

    Science.gov (United States)

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo

    2014-09-16

    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.

  11. The influence of physical and physiological cues on atomic force microscopy-based cell stiffness assessment.

    Directory of Open Access Journals (Sweden)

    Yu-Wei Chiou

    Full Text Available Atomic force microscopy provides a novel technique for differentiating the mechanical properties of various cell types. Cell elasticity is abundantly used to represent the structural strength of cells in different conditions. In this study, we are interested in whether physical or physiological cues affect cell elasticity in Atomic force microscopy (AFM-based assessments. The physical cues include the geometry of the AFM tips, the indenting force and the operating temperature of the AFM. All of these cues show a significant influence on the cell elasticity assessment. Sharp AFM tips create a two-fold increase in the value of the effective Young's modulus (E(eff relative to that of the blunt tips. Higher indenting force at the same loading rate generates higher estimated cell elasticity. Increasing the operation temperature of the AFM leads to decreases in the cell stiffness because the structure of actin filaments becomes disorganized. The physiological cues include the presence of fetal bovine serum or extracellular matrix-coated surfaces, the culture passage number, and the culture density. Both fetal bovine serum and the extracellular matrix are critical for cells to maintain the integrity of actin filaments and consequently exhibit higher elasticity. Unlike primary cells, mouse kidney progenitor cells can be passaged and maintain their morphology and elasticity for a very long period without a senescence phenotype. Finally, cell elasticity increases with increasing culture density only in MDCK epithelial cells. In summary, for researchers who use AFM to assess cell elasticity, our results provide basic and significant information about the suitable selection of physical and physiological cues.

  12. Enhanced quality factors and force sensitivity by attaching magnetic beads to cantilevers for atomic force microscopy in liquid

    CERN Document Server

    Hoof, Sebastian; Hoogenboom, Bart W

    2012-01-01

    Dynamic-mode atomic force microscopy (AFM) in liquid remains complicated due to the strong viscous damping of the cantilever resonance. Here we show that a high-quality resonance (Q>20) can be achieved in aqueous solution by attaching a microgram-bead at the end of the nanogram-cantilever. The resulting increase in cantilever mass causes the resonance frequency to drop significantly. However, the force sensitivity --- as expressed via the minimum detectable force gradient --- is hardly affected, because of the enhanced quality factor. Via the enhancement of the quality factor, the attached bead also reduces the relative importance of noise in the deflection detector. It can thus yield an improved signal-to-noise ratio when this detector noise is significant. We describe and analyze these effects for a set-up which includes magnetic actuation of the cantilevers and which can be easily implemented in any AFM system that is compatible with an inverted optical microscope.

  13. Reverse engineering of an affinity-switchable molecular interaction characterized by atomic force microscopy single-molecule force spectroscopy.

    Science.gov (United States)

    Anselmetti, Dario; Bartels, Frank Wilco; Becker, Anke; Decker, Björn; Eckel, Rainer; McIntosh, Matthew; Mattay, Jochen; Plattner, Patrik; Ros, Robert; Schäfer, Christian; Sewald, Norbert

    2008-02-19

    Tunable and switchable interaction between molecules is a key for regulation and control of cellular processes. The translation of the underlying physicochemical principles to synthetic and switchable functional entities and molecules that can mimic the corresponding molecular functions is called reverse molecular engineering. We quantitatively investigated autoinducer-regulated DNA-protein interaction in bacterial gene regulation processes with single atomic force microscopy (AFM) molecule force spectroscopy in vitro, and developed an artificial bistable molecular host-guest system that can be controlled and regulated by external signals (UV light exposure and thermal energy). The intermolecular binding functionality (affinity) and its reproducible and reversible switching has been proven by AFM force spectroscopy at the single-molecule level. This affinity-tunable optomechanical switch will allow novel applications with respect to molecular manipulation, nanoscale rewritable molecular memories, and/or artificial ion channels, which will serve for the controlled transport and release of ions and neutral compounds in the future.

  14. Characterization of the surface charge distribution on kaolinite particles using high resolution atomic force microscopy

    Science.gov (United States)

    Kumar, Naveen; Zhao, Cunlu; Klaassen, Aram; van den Ende, Dirk; Mugele, Frieder; Siretanu, Igor

    2016-02-01

    Most solid surfaces, in particular clay minerals and rock surfaces, acquire a surface charge upon exposure to an aqueous environment due to adsorption and/or desorption of ionic species. Macroscopic techniques such as titration and electrokinetic measurements are commonly used to determine the surface charge and ζ -potential of these surfaces. However, because of the macroscopic averaging character these techniques cannot do justice to the role of local heterogeneities on the surfaces. In this work, we use dynamic atomic force microscopy (AFM) to determine the distribution of surface charge on the two (gibbsite-like and silica-like) basal planes of kaolinite nanoparticles immersed in aqueous electrolyte with a lateral resolution of approximately 30 nm. The surface charge density is extracted from force-distance curves using DLVO theory in combination with surface complexation modeling. While the gibbsite-like and the silica-like facet display on average positive and negative surface charge values as expected, our measurements reveal lateral variations of more than a factor of two on seemingly atomically smooth terraces, even if high resolution AFM images clearly reveal the atomic lattice on the surface. These results suggest that simple surface complexation models of clays that attribute a unique surface chemistry and hence homogeneous surface charge densities to basal planes may miss important aspects of real clay surfaces.

  15. Atomic force microscopy imaging and single molecule recognition force spectroscopy of coat proteins on the surface of Bacillus subtilis spore.

    Science.gov (United States)

    Tang, Jilin; Krajcikova, Daniela; Zhu, Rong; Ebner, Andreas; Cutting, Simon; Gruber, Hermann J; Barak, Imrich; Hinterdorfer, Peter

    2007-01-01

    Coat assembly in Bacillus subtilis serves as a tractable model for the study of the self-assembly process of biological structures and has a significant potential for use in nano-biotechnological applications. In the present study, the morphology of B. subtilis spores was investigated by magnetically driven dynamic force microscopy (MAC mode atomic force microscopy) under physiological conditions. B. subtilis spores appeared as prolate structures, with a length of 0.6-3 microm and a width of about 0.5-2 microm. The spore surface was mainly covered with bump-like structures with diameters ranging from 8 to 70 nm. Besides topographical explorations, single molecule recognition force spectroscopy (SMRFS) was used to characterize the spore coat protein CotA. This protein was specifically recognized by a polyclonal antibody directed against CotA (anti-CotA), the antibody being covalently tethered to the AFM tip via a polyethylene glycol linker. The unbinding force between CotA and anti-CotA was determined as 55 +/- 2 pN. From the high-binding probability of more than 20% in force-distance cycles it is concluded that CotA locates in the outer surface of B. subtilis spores.

  16. Dimensional comparison between amplitude-modulation atomic force microscopy and scanning ion conductance microscopy of biological samples

    Science.gov (United States)

    Kim, Joonhui; Choi, MyungHoon; Jung, Goo-Eun; Rahim Ferhan, Abdul; Cho, Nam-Joon; Cho, Sang-Joon

    2016-08-01

    The range of scanning probe microscopy (SPM) applications for atomic force microscopy (AFM) is expanding in the biological sciences field, reflecting an increasing demand for tools that can improve our fundamental understanding of the physics behind biological systems. However, the complexity associated with applying SPM techniques in biomedical research hampers the full exploitation of its capabilities. Recently, the development of scanning ion conductance microscopy (SICM) has overcome these limitations and enabled contact-free, high resolution imaging of live biological specimens. In this work, we demonstrate the limitation of AFM for imaging biological samples in liquid due to artifacts arising from AFM tip-sample interaction, and how SICM imaging is able to overcome those limitations with contact-free scanning. We also demonstrate that SICM measurements, when compared to AFM, show better fit to the actual dimensions of the biological samples. Our results highlight the superiority of SICM imaging, enabling it to be widely adopted as a general and versatile research tool for biological studies in the nanoscale.

  17. Atomic-Scale Variations of the Mechanical Response of 2D Materials Detected by Noncontact Atomic Force Microscopy.

    Science.gov (United States)

    de la Torre, B; Ellner, M; Pou, P; Nicoara, N; Pérez, Rubén; Gómez-Rodríguez, J M

    2016-06-17

    We show that noncontact atomic force microscopy (AFM) is sensitive to the local stiffness in the atomic-scale limit on weakly coupled 2D materials, as graphene on metals. Our large amplitude AFM topography and dissipation images under ultrahigh vacuum and low temperature resolve the atomic and moiré patterns in graphene on Pt(111), despite its extremely low geometric corrugation. The imaging mechanisms are identified with a multiscale model based on density-functional theory calculations, where the energy cost of global and local deformations of graphene competes with short-range chemical and long-range van der Waals interactions. Atomic contrast is related with short-range tip-sample interactions, while the dissipation can be understood in terms of global deformations in the weakly coupled graphene layer. Remarkably, the observed moiré modulation is linked with the subtle variations of the local interplanar graphene-substrate interaction, opening a new route to explore the local mechanical properties of 2D materials at the atomic scale.

  18. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles.

    Science.gov (United States)

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B; Chen, Wenli

    2015-11-20

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10(-18) J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions.

  19. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

    Science.gov (United States)

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

    2015-11-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10-18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions.

  20. ATOMIC-FORCE MICROSCOPY AND REAL ATOMIC-RESOLUTION - SIMPLE COMPUTER-SIMULATIONS

    NARCIS (Netherlands)

    KOUTSOS, [No Value; MANIAS, E; TENBRINKE, G; HADZIIOANNOU, G

    1994-01-01

    Using a simple computer simulation for AFM imaging in the contact mode, pictures with true and false atomic resolution are demonstrated. The surface probed consists of two f.c.c. (111) planes and an atomic vacancy is introduced in the upper layer. Changing the size of the effective tip and its regis

  1. Atomic force microscopy as analytical tool to study physico-mechanical properties of intestinal cells

    Directory of Open Access Journals (Sweden)

    Christa Schimpel

    2015-07-01

    Full Text Available The small intestine is a complex system that carries out various functions. The main function of enterocytes is absorption of nutrients, whereas membranous cells (M cells are responsible for delivering antigens/foreign substances to the mucosal lymphoid tissues. However, to get a fundamental understanding of how cellular structures contribute to physiological processes, precise knowledge about surface morphologies, cytoskeleton organizations and biomechanical properties is necessary. Atomic force microscopy (AFM was used here as a powerful tool to study surface topographies of Caco-2 cells and M cells. Furthermore, cell elasticity (i.e., the mechanical response of a cell on a tip indentation, was elucidated by force curve measurements. Besides elasticity, adhesion was evaluated by recording the attraction and repulsion forces between the tip and the cell surface. Organization of F-actin networks were investigated via phalloidin labeling and visualization was performed with confocal laser scanning fluorescence microscopy (CLSM and scanning electron microscopy (SEM. The results of these various experimental techniques revealed significant differences in the cytoskeleton/microvilli arrangements and F-actin organization. Caco-2 cells displayed densely packed F-actin bundles covering the entire cell surface, indicating the formation of a well-differentiated brush border. In contrast, in M cells actins were arranged as short and/or truncated thin villi, only available at the cell edge. The elasticity of M cells was 1.7-fold higher compared to Caco-2 cells and increased significantly from the cell periphery to the nuclear region. Since elasticity can be directly linked to cell adhesion, M cells showed higher adhesion forces than Caco-2 cells. The combination of distinct experimental techniques shows that morphological differences between Caco-2 cells and M cells correlate with mechanical cell properties and provide useful information to understand

  2. Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

    Science.gov (United States)

    Cantrell, John H., Jr.; Cantrell, Sean A.

    2008-01-01

    A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

  3. Investigation into local cell mechanics by atomic force microscopy mapping and optical tweezer vertical indentation

    Science.gov (United States)

    Coceano, G.; Yousafzai, M. S.; Ma, W.; Ndoye, F.; Venturelli, L.; Hussain, I.; Bonin, S.; Niemela, J.; Scoles, G.; Cojoc, D.; Ferrari, E.

    2016-02-01

    Investigating the mechanical properties of cells could reveal a potential source of label-free markers of cancer progression, based on measurable viscoelastic parameters. The Young’s modulus has proved to be the most thoroughly studied so far, however, even for the same cell type, the elastic modulus reported in different studies spans a wide range of values, mainly due to the application of different experimental conditions. This complicates the reliable use of elasticity for the mechanical phenotyping of cells. Here we combine two complementary techniques, atomic force microscopy (AFM) and optical tweezer microscopy (OTM), providing a comprehensive mechanical comparison of three human breast cell lines: normal myoepithelial (HBL-100), luminal breast cancer (MCF-7) and basal breast cancer (MDA-MB-231) cells. The elastic modulus was measured locally by AFM and OTM on single cells, using similar indentation approaches but different measurement parameters. Peak force tapping AFM was employed at nanonewton forces and high loading rates to draw a viscoelastic map of each cell and the results indicated that the region on top of the nucleus provided the most meaningful results. OTM was employed at those locations at piconewton forces and low loading rates, to measure the elastic modulus in a real elastic regime and rule out the contribution of viscous forces typical of AFM. When measured by either AFM or OTM, the cell lines’ elasticity trend was similar for the aggressive MDA-MB-231 cells, which were found to be significantly softer than the other two cell types in both measurements. However, when comparing HBL-100 and MCF-7 cells, we found significant differences only when using OTM.

  4. Modeling of adhesion in tablet compression - I. atomic force microscopy and molecular simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J. J.; Li, T.; Bateman, S. D.; Erck, R.; Morris, K. R.; Energy Technology; Purdue Univ.; Novartis Pharmaceutical Corp.

    2003-04-01

    Adhesion problems during tablet manufacturing have been observed to be dependent on many formulation and process factors including the run time on the tablet press. Consequently, problems due to sticking may only become apparent towards the end of the development process when a prolonged run on the tablet press is attempted for the first time. It would be beneficial to predict in a relative sense if a formulation or new chemical entity has the potential for adhesion problems early in the development process. It was hypothesized that favorable intermolecular interaction between the drug molecules and the punch face is the first step or criterion in the adhesion process. Therefore, the rank order of adhesion during tablet compression should follow the rank order of these energies of interaction. The adhesion phenomenon was investigated using molecular simulations and contact mode atomic force microscopy (AFM). Three model compounds were chosen from a family of profen compounds. Silicon nitride AFM tips were modified by coating a 20-nm iron layer on the surfaces by sputter coating. Profen flat surfaces were made by melting and recrystallization. The modified AFM probe and each profen surface were immersed in the corresponding profen saturated water during force measurements using AFM. The work of adhesion between iron and ibuprofen, ketoprofen, and flurbiprofen in vacuum were determined to be -184.1, -2469.3, -17.3 mJ {center_dot} m-2, respectively. The rank order of the work of adhesion between iron and profen compounds decreased in the order: ketoprofen > ibuprofen > flurbiprofen. The rank order of interaction between the drug molecules and the iron superlattice as predicted by molecular simulation using Cerius2 is in agreement with the AFM measurements. It has been demonstrated that Atomic Force Microscopy is a powerful tool in studying the adhesion phenomena between organic drug compounds and metal surface. The study has provided insight into the adhesion problems

  5. Local elasticity and adhesion of nanostructures on Drosophila melanogaster wing membrane studied using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, Ryan, E-mail: rbwagner@purdue.edu [School of Mechanical Engineering, Purdue University, West Lafayette (United States); Brick Nanotechnology Center, Purdue University, West Lafayette (United States); Pittendrigh, Barry R. [Department of Entomology, University of Illinois, Champaign (United States); Raman, Arvind, E-mail: raman@purdue.edu [School of Mechanical Engineering, Purdue University, West Lafayette (United States); Brick Nanotechnology Center, Purdue University, West Lafayette (United States)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer We studied the wing membrane of Drosophila melanogaster with atomic force microscopy. Black-Right-Pointing-Pointer We report the structure, elasticity, and adhesion on the wing membrane in air and nitrogen environments. Black-Right-Pointing-Pointer Results provide insight into the nature of the wing membrane enabling the development of biomimetic surface and micro air vehicles. - Abstract: Insect wings have a naturally occurring, complex, functional, hierarchical microstructure and nanostructure, which enable a remarkably water-resistant and self-cleaning surface. Insect wings are used as a basis for engineering biomimetic materials; however, the material properties of these nanostructures such as local elastic modulus and adhesion are poorly understood. We studied the wings of the Canton-S strain of Drosophila melanogaster (hereafter referred to as Drosophila) with atomic force microscopy (AFM) to quantify the local material properties of Drosophila wing surface nanostructures. The wings are found to have a hierarchical structure of 10-20 {mu}m long, 0.5-1 {mu}m diameter hair, and at a much smaller scale, 100 nm diameter and 30-60 nm high bumps. The local properties of these nanoscale bumps were studied under ambient and dry conditions with force-volume AFM. The wing membrane was found to have a elastic modulus on the order of 1000 MPa and the work of adhesion between the probe and wing membrane surface was found to be on the order of 100 mJ/m{sup 2}, these properties are the same order of magnitude as common thermoplastic polymers such as polyethylene. The difference in work of adhesion between the nanoscale bump and membrane does not change significantly between ambient (relative humidity of 30%) or dry conditions. This suggests that the nanoscale bumps and the surrounding membrane are chemically similar and only work to increase hydrophobicity though surface roughening or the geometric lotus effect.

  6. Conditions to minimize soft single biomolecule deformation when imaging with atomic force microscopy.

    Science.gov (United States)

    Godon, Christian; Teulon, Jean-Marie; Odorico, Michael; Basset, Christian; Meillan, Matthieu; Vellutini, Luc; Chen, Shu-Wen W; Pellequer, Jean-Luc

    2016-12-23

    A recurrent interrogation when imaging soft biomolecules using atomic force microscopy (AFM) is the putative deformation of molecules leading to a bias in recording true topographical surfaces. Deformation of biomolecules comes from three sources: sample instability, adsorption to the imaging substrate, and crushing under tip pressure. To disentangle these causes, we measured the maximum height of a well-known biomolecule, the tobacco mosaic virus (TMV), under eight different experimental conditions positing that the maximum height value is a specific indicator of sample deformations. Six basic AFM experimental factors were tested: imaging in air (AIR) versus in liquid (LIQ), imaging with flat minerals (MICA) versus flat organic surfaces (self-assembled monolayers, SAM), and imaging forces with oscillating tapping mode (TAP) versus PeakForce tapping (PFT). The results show that the most critical parameter in accurately measuring the height of TMV in air is the substrate. In a liquid environment, regardless of the substrate, the most critical parameter is the imaging mode. Most importantly, the expected TMV height values were obtained with both imaging with the PeakForce tapping mode either in liquid or in air at the condition of using self-assembled monolayers as substrate. This study unambiguously explains previous poor results of imaging biomolecules on mica in air and suggests alternative methodologies for depositing soft biomolecules on well organized self-assembled monolayers.

  7. Atomic force microscopy as a nanoscience tool in rational food design.

    Science.gov (United States)

    Morris, Victor J; Woodward, Nicola C; Gunning, Allan P

    2011-09-01

    Atomic force microscopy (AFM) is a nanoscience tool that has been used to provide new information on the molecular structure of food materials. As an imaging tool it has led to solutions to previously intractable problems in food science. This type of information can provide a basis for tailoring food structures to optimise functional behaviour. Such an approach will be illustrated by indicating how a basic understanding of the role of interfacial stability in complex foods systems can be extended to understand how such interfacial structures behave on digestion, and how this in turn suggests routes for the rational design of processed food structures to modify lipolysis and control fat intake. As a force transducer AFM can be used to probe interactions between food structures such as emulsion droplets at the colloidal level. This use of force spectroscopy will be illustrated through showing how it allows the effect of the structural modification of interfacial structures on colloidal interactions to be probed in model emulsion systems. Direct studies on interactions between colliding soft, deformable droplets reveal new types of interactions unique to deformable particles that can be exploited to manipulate the behaviour of processed or natural emulsion structures involved in digestion processes. Force spectroscopy can be adapted to probe specific intermolecular interactions, and this application of the technique will be illustrated through its use to test molecular hypotheses for the bioactivity of modified pectin molecules.

  8. Enhanced efficiency in the excitation of higher modes for atomic force microscopy and mechanical sensors operated in liquids

    Energy Technology Data Exchange (ETDEWEB)

    Penedo, M., E-mail: mapenedo@imm.cnm.csic.es; Hormeño, S.; Fernández-Martínez, I.; Luna, M.; Briones, F. [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid (Spain); Raman, A. [Birck Nanotechnology Center and School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47904 (United States)

    2014-10-27

    Recent developments in dynamic Atomic Force Microscopy where several eigenmodes are simultaneously excited in liquid media are proving to be an excellent tool in biological studies. Despite its relevance, the search for a reliable, efficient, and strong cantilever excitation method is still in progress. Herein, we present a theoretical modeling and experimental results of different actuation methods compatible with the operation of Atomic Force Microscopy in liquid environments: ideal acoustic, homogeneously distributed force, distributed applied torque (MAC Mode™), photothermal and magnetostrictive excitation. From the analysis of the results, it can be concluded that magnetostriction is the strongest and most efficient technique for higher eigenmode excitation when using soft cantilevers in liquid media.

  9. Determination of electrostatic force and its characteristics based on phase difference by amplitude modulation atomic force microscopy

    Science.gov (United States)

    Wang, Kesheng; Cheng, Jia; Yao, Shiji; Lu, Yijia; Ji, Linhong; Xu, Dengfeng

    2016-12-01

    Electrostatic force measurement at the micro/nano scale is of great significance in science and engineering. In this paper, a reasonable way of applying voltage is put forward by taking an electrostatic chuck in a real integrated circuit manufacturing process as a sample, applying voltage in the probe and the sample electrode, respectively, and comparing the measurement effect of the probe oscillation phase difference by amplitude modulation atomic force microscopy. Based on the phase difference obtained from the experiment, the quantitative dependence of the absolute magnitude of the electrostatic force on the tip-sample distance and applied voltage is established by means of theoretical analysis and numerical simulation. The results show that the varying characteristics of the electrostatic force with the distance and voltage at the micro/nano scale are similar to those at the macroscopic scale. Electrostatic force gradually decays with increasing distance. Electrostatic force is basically proportional to the square of applied voltage. Meanwhile, the applicable conditions of the above laws are discussed. In addition, a comparison of the results in this paper with the results of the energy dissipation method shows the two are consistent in general. The error decreases with increasing distance, and the effect of voltage on the error is small.

  10. Analysis of Adhesive Characteristics of Asphalt Based on Atomic Force Microscopy and Molecular Dynamics Simulation.

    Science.gov (United States)

    Xu, Meng; Yi, Junyan; Feng, Decheng; Huang, Yudong; Wang, Dongsheng

    2016-05-18

    Asphalt binder is a very important building material in infrastructure construction; it is commonly mixed with mineral aggregate and used to produce asphalt concrete. Owing to the large differences in physical and chemical properties between asphalt and aggregate, adhesive bonds play an important role in determining the performance of asphalt concrete. Although many types of adhesive bonding mechanisms have been proposed to explain the interaction forces between asphalt binder and mineral aggregate, few have been confirmed and characterized. In comparison with chemical interactions, physical adsorption has been considered to play a more important role in adhesive bonding between asphalt and mineral aggregate. In this study, the silicon tip of an atomic force microscope was used to represent silicate minerals in aggregate, and a nanoscale analysis of the characteristics of adhesive bonding between asphalt binder and the silicon tip was conducted via an atomic force microscopy (AFM) test and molecular dynamics (MD) simulations. The results of the measurements and simulations could help in better understanding of the bonding and debonding procedures in asphalt-aggregate mixtures during hot mixing and under traffic loading. MD simulations on a single molecule of a component of asphalt and monocrystalline silicon demonstrate that molecules with a higher atomic density and planar structure, such as three types of asphaltene molecules, can provide greater adhesive strength. However, regarding the real components of asphalt binder, both the MD simulations and AFM test indicate that the colloidal structural behavior of asphalt also has a large influence on the adhesion behavior between asphalt and silicon. A schematic model of the interaction between asphalt and silicon is presented, which can explain the effect of aging on the adhesion behavior of asphalt.

  11. Nonlinear dynamic analysis of atomic force microscopy under deterministic and random excitation

    Energy Technology Data Exchange (ETDEWEB)

    Pishkenari, Hossein Nejat [Center of Excellence in Design, Robotics and Automation (CEDRA), School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Behzad, Mehdi [Center of Excellence in Design, Robotics and Automation (CEDRA), School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)], E-mail: m_behzad@sharif.edu; Meghdari, Ali [Center of Excellence in Design, Robotics and Automation (CEDRA), School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2008-08-15

    The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. This paper is devoted to the analysis of nonlinear behavior of amplitude modulation (AM) and frequency modulation (FM) modes of atomic force microscopy. For this, the microcantilever (which forms the basis for the operation of AFM) is modeled as a single mode approximation and the interaction between the sample and cantilever is derived from a van der Waals potential. Using perturbation methods such as averaging, and Fourier transform nonlinear equations of motion are analytically solved and the advantageous results are extracted from this nonlinear analysis. The results of the proposed techniques for AM-AFM, clearly depict the existence of two stable and one unstable (saddle) solutions for some of exciting parameters under deterministic vibration. The basin of attraction of two stable solutions is different and dependent on the exciting frequency. From this analysis the range of the frequency which will result in a unique periodic response can be obtained and used in practical experiments. Furthermore the analytical responses determined by perturbation techniques can be used to detect the parameter region where the chaotic motion is avoided. On the other hand for FM-AFM, the relation between frequency shift and the system parameters can be extracted and used for investigation of the system nonlinear behavior. The nonlinear behavior of the oscillating tip can easily explain the observed shift of frequency as a function of tip sample distance. Also in this paper we have investigated the AM-AFM system response under a random excitation. Using two different methods we have obtained the statistical properties of the tip motion. The results show that we can use the mean square value of tip motion to image the sample when the excitation signal is random.

  12. The chemical structure of a molecule resolved by atomic force microscopy

    NARCIS (Netherlands)

    Gross, L.; Mohn, F.; Moll, N.; Liljeroth, P.|info:eu-repo/dai/nl/314007423; Meyer, G.

    2009-01-01

    Resolving individual atoms has always been the ultimate goal of surface microscopy. The scanning tunneling microscope images atomic-scale features on surfaces, but resolving single atoms within an adsorbed molecule remains a great challenge because the tunneling current is primarily sensitive to the

  13. Topographic and electronic contrast of the graphene moir´e on Ir(111) probed by scanning tunneling microscopy and noncontact atomic force microscopy

    NARCIS (Netherlands)

    Sun, Z.; Hämäläinen, K.; Sainio, K.; Lahtinen, J.; Vanmaekelbergh, D.A.M.; Liljeroth, P.

    2011-01-01

    Epitaxial graphene grown on transition-metal surfaces typically exhibits a moir´e pattern due to the lattice mismatch between graphene and the underlying metal surface. We use both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to probe the electronic and topographic contrast

  14. Electrochemical atomic force microscopy reveals potential stimulated height changes of redox responsive Cu-azurin on gold

    NARCIS (Netherlands)

    Wu, Hairong; Feng, Xueling; Kieviet, B.D.; Zhang, K.; Zandvliet, H.J.W.; Canters, G.W.; Schon, P.M.; Vancso, G.J.

    2015-01-01

    The redox active metalloprotein Cu-azurin was directly chemisorbed on bare gold electrodes through disulfide forming groups (Cys3Cys26). Topological and electrochemical properties of the immobilized molecules were investigated by electrochemical atomic force microscopy (EC-AFM) in Peak Force Tapping

  15. Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy

    Science.gov (United States)

    Jarvis, Samuel Paul

    2015-01-01

    A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions. PMID:26307976

  16. Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy.

    Science.gov (United States)

    Jarvis, Samuel Paul

    2015-08-21

    A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions.

  17. Elasticity Maps of Living Neurons Measured by Combined Fluorescence and Atomic Force Microscopy

    CERN Document Server

    Spedden, Elise; Naumova, Elena N; Kaplan, David L; Staii, Cristian

    2013-01-01

    Detailed knowledge of mechanical parameters such as cell elasticity, stiffness of the growth substrate, or traction stresses generated during axonal extensions is essential for understanding the mechanisms that control neuronal growth. Here we combine Atomic Force Microscopy based force spectroscopy with Fluorescence Microscopy to produce systematic, high-resolution elasticity maps for three different types of live neuronal cells: cortical (embryonic rat), embryonic chick dorsal root ganglion, and P-19 (mouse embryonic carcinoma stem cells) neurons. We measure how the stiffness of neurons changes both during neurite outgrowth and upon disruption of microtubules of the cell. We find reversible local stiffening of the cell during growth, and show that the increase in local elastic modulus is primarily due to the formation of microtubules. We also report that cortical and P-19 neurons have similar elasticity maps, with elastic moduli in the range 0.1-2 kPa, with typical average values of 0.4 kPa (P-19) and 0.2 k...

  18. Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Samuel Paul Jarvis

    2015-08-01

    Full Text Available A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions.

  19. Polymer Droplet Dynamic Wetting Measurement at the Nanometer Scale on Smooth Surfaces Using Atomic Force Microscopy

    Science.gov (United States)

    Soleymaniha, Mohammadreza; Felts, Jonathan Robert; Anml Team

    2016-11-01

    Fluid spreading is a complex phenomenon driven strongly by intermolecular forces that requires nanometer scale microscopy to observe and understand. We present a technique for measuring molten polymer spreading dynamics with nanometer scale spatial resolution at elevated temperatures on sapphire, silicon oxide and mica using tapping-mode atomic force microscopy (AFM). The experimental setup is used to measure the spreading dynamics of polystyrene droplets with 2 μ m diameters at 115-175 C. Custom image processing algorithms realize the droplet height, radius, volume and contact angle of the droplet over time. The contact angle evolution followed a power law with time with experimental exponent values of -0.26, -0.08, and -0.2 for sapphire, silicon oxide, and mica, respectively at 115 C. The non-zero steady state contact angles result in a slower evolution of contact angle with time compared to Tanner's Law, as expected. We observe local crystallinity on the molten droplet surface, where crystalline structures appear to nucleate at the contact line and migrate toward the top of the droplet. Increasing the temperature from 115 C to 175 C reduced surface crystallinity from 35% to 12%, consistent with increasingly energetically favorable amorphous phase as the temperature approaches the melting temperature. This platform provides a way to measure spreading dynamics of extremely small volumes of heterogeneously complex fluids not possible through other means. Dr.Jonathan Felts is the principal investigator of the ANML research group in Mechanical Engineering Department of Texas A&M University.

  20. Transformation twinning of Ni-Mn-Ga characterized with temperature-controlled atomic force microscopy.

    Science.gov (United States)

    Reinhold, Matthew; Watson, Chad; Knowlton, William B; Müllner, Peter

    2010-06-01

    The magnetomechanical properties of ferromagnetic shape memory alloy Ni-Mn-Ga single crystals depend strongly on the twin microstructure, which can be modified through thermomagnetomechanical training. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to characterize the evolution of twin microstructures during thermomechanical training of a Ni-Mn-Ga single crystal. Experiments were performed in the martensite phase at 25 degrees C and in the austenite phase at 55 degrees C. Two distinct twinning surface reliefs were observed at room temperature. At elevated temperature (55 degrees C), the surface relief of one twinning mode disappeared while the other relief remained unchanged. When cooled back to 25 degrees C, the twin surface relief recovered. The relief persisting at elevated temperature specifies the positions of twin boundaries that were present when the sample was polished prior to surface characterization. AFM and MFM following thermomechanical treatment provide a nondestructive method to identify the crystallographic orientation of each twin and of each twin boundary plane. Temperature dependent AFM and MFM experiments reveal the twinning history thereby establishing the technique as a unique predictive tool for revealing the path of the martensitic and reverse transformations of magnetic shape memory alloys.

  1. Effect of cold plasma on glial cell morphology studied by atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Nina Recek

    Full Text Available The atomic force microscope (AFM is broadly used to study the morphology of cells. The morphological characteristics and differences of the cell membrane between normal human astrocytes and glial tumor cells are not well explored. Following treatment with cold atmospheric plasma, evaluation of the selective effect of plasma on cell viability of tumor cells is poorly understood and requires further evaluation. Using AFM we imaged morphology of glial cells before and after cold atmospheric plasma treatment. To look more closely at the effect of plasma on cell membrane, high resolution imaging was used. We report the differences between normal human astrocytes and human glioblastoma cells by considering the membrane surface details. Our data, obtained for the first time on these cells using atomic force microscopy, argue for an architectural feature on the cell membrane, i.e. brush layers, different in normal human astrocytes as compared to glioblastoma cells. The brush layer disappears from the cell membrane surface of normal E6/E7 cells and is maintained in the glioblastoma U87 cells after plasma treatment.

  2. Mechanical and Electrical Properties of CdTe Tetrapods Studied byAtomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Liang; Park, Jeong Young; Cui, Yi; Alivisatos, Paul; Shcrier, Joshua; Lee, Byounghak; Wang, Lin-Wang; Salmeron, Miquel

    2007-08-30

    The mechanical and electrical properties of CdTe tetrapod-shaped nanocrystals have been studied with atomic force microscopy. Tapping mode images of tetrapods deposited on silicon wafers revealed that they contact the surface with the ends of three arms. The length of these arms was found to be 130 {+-} 10 nm. A large fraction of the tetrapods had a shortened vertical arm as a result of fracture during sample preparation. Fracture also occurs when the applied load is a few nanonewtons. Compression experiments with the AFM tip indicate that tetrapods with the shortened vertical arm deform elastically when the applied force was less than 50 nN. Above 90 nN additional fracture events occurred that further shorted the vertical arm. Loads above 130 nN produced irreversible damage to the other arms as well. Current-voltage characteristics of tetrapods deposited on gold indicated semiconducting behavior with a current gap of {approx}2 eV at low loads (<50 nN) and a narrowing to about 1 eV at loads between 60 and 110 nN. Atomic calculation of the deformation suggests that the ends of the tetrapod arms are stuck during compression so that the deformations are due to bending modes. The reduction of the current gap is due to electrostatic effects, rather than strain deformation effects inside the tetrapod.

  3. Label-free quantification of Tacrolimus in biological samples by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Menotta, Michele, E-mail: michele.menotta@uniurb.it [Department of Biomolecular Sciences, University of Urbino “Carlo Bo” via Saffi 2, Urbino (Italy); Biagiotti, Sara [Department of Biomolecular Sciences, University of Urbino “Carlo Bo” via Saffi 2, Urbino (Italy); Streppa, Laura [Physics Laboratory, CNRS-ENS, UMR 5672, Lyon (France); Cell and Molecular Biology Laboratory, CNRS-ENS Lyon, UMR 5239, IFR128, Lyon (France); Rossi, Luigia; Magnani, Mauro [Department of Biomolecular Sciences, University of Urbino “Carlo Bo” via Saffi 2, Urbino (Italy)

    2015-07-16

    Highlights: • Tacrolimus is a potent immunosuppressant drug that has to be continually monitored. • We present an atomic force microscope approach for quantification of Tacrolimus in blood samples. • Detection and quantification have been successfully achieved. - Abstract: In the present paper we describe an atomic force microscopy (AFM)-based method for the quantitative analysis of FK506 (Tacrolimus) in whole blood (WB) samples. Current reference methods used to quantify this immunosuppressive drug are based on mass spectrometry. In addition, an immunoenzymatic assay (ELISA) has been developed and is widely used in clinic, even though it shows a small but consistent overestimation of the actual drug concentration when compared with the mass spectrometry method. The AFM biosensor presented herein utilises the endogen drug receptor, FKBP12, to quantify Tacrolimus levels. The biosensor was first assayed to detect the free drug in solution, and subsequently used for the detection of Tacrolimus in blood samples. The sensor was suitable to generate a dose–response curve in the full range of clinical drug monitoring. A comparison with the clinically tested ELISA assay is also reported.

  4. Nanoscale Subsurface Imaging of Nanocomposites via Resonant Difference-Frequency Atomic Force Ultrasonic Microscopy

    Science.gov (United States)

    Cantrell, Sean A.; Cantrell, John H.; Lillehei, Peter T.

    2007-01-01

    A scanning probe microscope methodology, called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), has been developed. The method employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope engages the sample top surface. The cantilever is driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave at the sample surface generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create amplitude and phase-generated images of nanoscale near-surface and subsurface features. RDF-AFUM phase images of LaRC-CP2 polyimide polymer containing embedded nanostructures are presented. A RDF-AFUM micrograph of a 12.7 micrometer thick film of LaRC-CP2 containing a monolayer of gold nanoparticles embedded 7 micrometers below the specimen surface reveals the occurrence of contiguous amorphous and crystalline phases within the bulk of the polymer and a preferential growth of the crystalline phase in the vicinity of the gold nanoparticles. A RDF-AFUM micrograph of LaRC-CP2 film containing randomly dispersed carbon nanotubes reveals the growth of an interphase region at certain nanotube-polymer interfaces.

  5. The structure and function of cell membranes examined by atomic force microscopy and single-molecule force spectroscopy.

    Science.gov (United States)

    Shan, Yuping; Wang, Hongda

    2015-06-07

    The cell membrane is one of the most complicated biological complexes, and long-term fierce debates regarding the cell membrane persist because of technical hurdles. With the rapid development of nanotechnology and single-molecule techniques, our understanding of cell membranes has substantially increased. Atomic force microscopy (AFM) has provided several unprecedented advances (e.g., high resolution, three-dimensional and in situ measurements) in the study of cell membranes and has been used to systematically dissect the membrane structure in situ from both sides of membranes; as a result, novel models of cell membranes have recently been proposed. This review summarizes the new progress regarding membrane structure using in situ AFM and single-molecule force spectroscopy (SMFS), which may shed light on the study of the structure and functions of cell membranes.

  6. Comparative analysis of clastogen-induced chromosome aberrations observed with light microscopy and by means of atomic force microscopy.

    Science.gov (United States)

    Koleva, Vanya Petrova; Dragoeva, Asya Pencheva; Andreeva, Andreana Ivanova; Burova, Marina Todorova; Georgiev, Sevdalin; Enchev, Dobromir Dimitrov

    2013-04-30

    Different types of chromosome aberration were observed in mouse bone-marrow cells after treatment with 4-bromo-N,N-diethyl-5,5-dimethyl-2,5-dihydro-1,2-oxaphosphol-2-amine 2-oxide (Br-oxaphosphole, Br-oxph) in a previous study. The aim of the present study is to perform a comparative analysis of these chromosomal damages observed with light microscopy (LM) and by means of atomic force microscopy (AFM). The kinds of aberrations scored by LM were substantially corrected by images at the ultrastructural level. The AFM analysis excluded 29.0% of gaps and 33.3% of fusion-type aberrations. On the other hand, AFM revealed the presence of aberrations that were not visible under the LM. This indicates that only AFM images would provide precise information about the real nature of chromosomal damages. The results of our study revealed that the 'real gaps' represented about 50% of all the gaps visible under LM. Excluded 'false gaps' were detected via AFM as breaks or decondensed chromosome regions. These results would support the statement that gaps must be included when testing genotoxicity. The ultrastructural analysis also confirmed the validity of using LM in the mouse bone-marrow chromosome aberration test, as a tool for detecting genotoxicity of chemicals in routine studies. When there is a need for precise evaluation of chromosome damage, only AFM images can provide information on specific genotoxic effects.

  7. Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

    Directory of Open Access Journals (Sweden)

    Thomas König

    2011-01-01

    Full Text Available Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001 and line defects in aluminum oxide on NiAl(110, respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM and the electronic structure by scanning tunneling spectroscopy (STS. On magnesium oxide, different color centers, i.e., F0, F+, F2+ and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F2+-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms.

  8. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Jiandong; Zhang, Li [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Wang, Michael Yu, E-mail: michael.wang@nus.edu.sg [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Department of Mechanical Engineering, National University of Singapore, Singapore 117575 (Singapore)

    2015-12-15

    In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

  9. First-Principles Atomic Force Microscopy Image Simulations with Density Embedding Theory.

    Science.gov (United States)

    Sakai, Yuki; Lee, Alex J; Chelikowsky, James R

    2016-05-11

    We present an efficient first-principles method for simulating noncontact atomic force microscopy (nc-AFM) images using a "frozen density" embedding theory. Frozen density embedding theory enables one to efficiently compute the tip-sample interaction by considering a sample as a frozen external field. This method reduces the extensive computational load of first-principles AFM simulations by avoiding consideration of the entire tip-sample system and focusing on the tip alone. We demonstrate that our simulation with frozen density embedding theory accurately reproduces full density functional theory simulations of freestanding hydrocarbon molecules while the computational time is significantly reduced. Our method also captures the electronic effect of a Cu(111) substrate on the AFM image of pentacene and reproduces the experimental AFM image of Cu2N on a Cu(100) surface. This approach is applicable for theoretical imaging applications on large molecules, two-dimensional materials, and materials surfaces.

  10. Observations and morphological analysis of supermolecular structure of natural bitumens by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yevgeny A. Golubev; Olga V. Kovaleva; Nikolay P. Yushkin [Institute of Geology of RAS, Syktyvkar (Russian Federation)

    2008-01-15

    The supermolecular structures of natural bitumens of the thermal consequent row asphaltites lower kerites (albertites), higher kerites (impsonites), anthraxolites from the Timan-Pechora petroleum province and Karelian shungite rocks, Russia, were studied in details. The experimental technique used was atomic force microscopy (AFM), following fracture preparation. The element distribution of the sample surfaces was analyzed by an X-ray microanalyser 'Link ISIS', combined with a scanning electron microscope (SEM). In this work, we characterized the supermolecular evolution of natural solid bitumens in the carbonization sequence by quantitative parameters. We showed that supermolecular structure can be important in defining to which classification group solid bitumens belong. 29 refs., 7 figs., 2 tabs.

  11. Mode-synthesizing atomic force microscopy for volume characterization of mixed metal nanoparticles.

    Science.gov (United States)

    Vitry, P; Bourillot, E; Tétard, L; Plassard, C; Lacroute, Y; Lesniewska, E

    2016-09-01

    Atomic force microscopy (AFM) and other techniques derived from AFM have revolutionized the understanding of materials and biology at the nanoscale, but mostly provide surface properties. The observation of subsurface nanoscale features and properties remains a great challenge in nanometrology. The operating principle of the mode-synthesizing AFM (MSAFM) is based on the interaction of two ultrasonic waves, one launched by the AFM probe fp , a second launched by the sample fs , and their resulting nonlinear frequency mixing. Recent developments highlighted the need for quantitative correlation between the role of the frequency actuation of the probe fp and the sample fs . Here we present the great potential of MSAFM for advanced volume characterization of metallic nanoparticles presenting a multilayered structure composed of a nickel core surrounded by a gold envelope.

  12. A Thin Liquid Film and Its Effects in an Atomic Force Microscopy Measurement

    Institute of Scientific and Technical Information of China (English)

    LIN Jing; ZHENG Zhi-Jun; YU Ji-Lin; BAI Yi-Long

    2009-01-01

    Recently,it has been observed that a liquid film spreading on a sample surface will significantly distort atomic force microscopy (AFM) measurements.In order to elaborate on the effect,we establish an equation governing the deformation of liquid film under its interaction with the AFM tip and substrate.A key issue is the critical liquid bump height yoc,at which the liquid film jumps to contact the AFM tip.It is found that there are three distinct regimes in the variation of yoc with film thickness H,depending on Hamaker constants of tip,sample and liquid.Noticeably,there is a characteristic thickness H* physically defining what a thin fihn is;namely,once the film thickness H is the same order as H*,the effect of film thickness should be taken into account.The value of H* is dependent on Hamaker constants and liquid surface tension as well as tip radius.

  13. Sidewall roughness measurement inside photonic crystal holes by atomic force microscopy

    Science.gov (United States)

    Strasser, P.; Robin, F.; Carlström, C. F.; Wüest, R.; Kappeler, R.; Jäckel, H.

    2007-10-01

    We present a measurement technique to quantify sidewall roughness inside planar photonic crystal (PhC) holes. Atomic force microscopy is used to scan hole cross-section profiles. By fitting a circle onto each scan line and subtracting this circle from the measurement data, a quantitative value for the deviation from the ideal cylindrical hole shape is extracted. We investigate the sidewall roughness of InP-based PhC holes depending on the nitrogen content of the semiconductor etching plasma. The existence of a trade-off between hole undercut and surface roughness by optimizing the flux of nitrogen during the plasma etching of the PhC holes is confirmed. We further quantify with this technique the influence of the direct-writing of octagons instead of circles by electron-beam lithography on the measured roughness.

  14. Subharmonic excitation in amplitude modulation atomic force microscopy in the presence of adsorbed water layers

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Sergio [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Barcons, Victor [Departament de Disseny i Programacio de Sistemes Electronics, UPC - Universitat Politecnica de Catalunya Av. Bases, 61, 08242 Manresa (Spain); Verdaguer, Albert [Centre d' Investigacio en Nanociencia i Nanotecnologia (CIN2) (CSIC-ICN), Esfera UAB, Campus de la UAB, Edifici CM-7, 08193-Bellaterra, Catalunya (Spain); Chiesa, Matteo [Laboratory of Energy and Nanosciences, Masdar Institute of Science and Technology, P.O. BOX 54224, Abu Dhabi (United Arab Emirates); Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307 (United States)

    2011-12-01

    In ambient conditions, nanometric water layers form on hydrophilic surfaces covering them and significantly changing their properties and characteristics. Here we report the excitation of subharmonics in amplitude modulation atomic force microscopy induced by intermittent water contacts. Our simulations show that there are several regimes of operation depending on whether there is perturbation of water layers. Single period orbitals, where subharmonics are never induced, follow only when the tip is either in permanent contact with the water layers or in pure noncontact where the water layers are never perturbed. When the water layers are perturbed subharmonic excitation increases with decreasing oscillation amplitude. We derive an analytical expression which establishes whether water perturbations compromise harmonic motion and show that the predictions are in agreement with numerical simulations. Empirical validation of our interpretation is provided by the observation of a range of values for apparent height of water layers when subharmonic excitation is predicted.

  15. Investigations of Silk Fibers Using X-Ray Scattering and Atomic Force Microscopy

    Science.gov (United States)

    Miller, Lance D.; Putthanarat, Sirina; Eby, Ronald K.; Adams, W. W.; Liu, G. F.

    1998-03-01

    Silk fibers from the cocoon of Bombyx mori and the dragline of Nephila clavipes have been investigated by small angle x-ray scattering (SAXS) and atomic force microscopy (AFM). The large scale morphology of these silks have minimum scattering dimensions, and correlation length on the order of 150-300 nm. Several types of AFM measurements on peeled and abraided silk samples have revealed dimensions in agreement with SAXS results. Further agreemeent has been found through the incorporation of discrete Fourier transform theory on AFM topographic information as compared to SAXS patterns. This incorporation allows the materials scientist a way of visualizing the relationship between a material and its resulting scattering function. All of these studies yield a more complete view of the silk morphology and give a new method of model building from scattering experiments.

  16. Nanomechanical DNA origami 'single-molecule beacons' directly imaged by atomic force microscopy

    Science.gov (United States)

    Kuzuya, Akinori; Sakai, Yusuke; Yamazaki, Takahiro; Xu, Yan; Komiyama, Makoto

    2011-01-01

    DNA origami involves the folding of long single-stranded DNA into designed structures with the aid of short staple strands; such structures may enable the development of useful nanomechanical DNA devices. Here we develop versatile sensing systems for a variety of chemical and biological targets at molecular resolution. We have designed functional nanomechanical DNA origami devices that can be used as 'single-molecule beacons', and function as pinching devices. Using 'DNA origami pliers' and 'DNA origami forceps', which consist of two levers ~170 nm long connected at a fulcrum, various single-molecule inorganic and organic targets ranging from metal ions to proteins can be visually detected using atomic force microscopy by a shape transition of the origami devices. Any detection mechanism suitable for the target of interest, pinching, zipping or unzipping, can be chosen and used orthogonally with differently shaped origami devices in the same mixture using a single platform. PMID:21863016

  17. Electrothermally driven high-frequency piezoresistive SiC cantilevers for dynamic atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Boubekri, R.; Cambril, E.; Couraud, L.; Bernardi, L.; Madouri, A. [LPN, CNRS-UPR20, route de Nozay, 91460 Marcoussis (France); Portail, M. [Centre de Recherche sur l' Hetero-Epitaxie et ses Applications CNRS, Rue Bernard Gregory, 06560 Valhonne (France); Chassagne, T.; Moisson, C.; Zielinski, M. [NOVASiC, Savoie Technolac, Arche bât 4, BP 267, 73375 Le Bourget du Lac Cedex (France); Jiao, S.; Michaud, J.-F.; Alquier, D. [Université François Rabelais, Tours, GREMAN, CNRS-UMR7347, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours Cedex 2 (France); Bouloc, J.; Nony, L.; Bocquet, F.; Loppacher, C. [IM2NP-CNRS/Aix-Marseille University, 38 rue Frédéric Joliot-Curie, 13451 Marseille (France); Martrou, D.; Gauthier, S., E-mail: gauthier@cemes.fr [CEMES, CNRS UPR 8011 et Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse (France)

    2014-08-07

    Cantilevers with resonance frequency ranging from 1 MHz to 100 MHz have been developed for dynamic atomic force microscopy. These sensors are fabricated from 3C-SiC epilayers grown on Si(100) substrates by low pressure chemical vapor deposition. They use an on-chip method both for driving and sensing the displacement of the cantilever. A first gold metallic loop deposited on top of the cantilever is used to drive its oscillation by electrothermal actuation. The sensing of this oscillation is performed by monitoring the resistance of a second Au loop. This metallic piezoresistive detection method has distinct advantages relative to more common semiconductor-based schemes. The optimization, design, fabrication, and characteristics of these cantilevers are discussed.

  18. Surface nanobubbles studied by atomic force microscopy techniques: Facts, fiction, and open questions

    Science.gov (United States)

    Schönherr, Holger; Hain, Nicole; Walczyk, Wiktoria; Wesner, Daniel; Druzhinin, Sergey I.

    2016-08-01

    In this review surface nanobubbles, which are presumably gas-filled enclosures found at the solid-liquid interface, are introduced and discussed together with key experimental findings that suggest that these nanoscale features indeed exist and are filled with gas. The most prominent technique used thus far has been atomic force microscopy (AFM). However, due to its potentially invasive nature, AFM data must be interpreted with great care. Owing to their curved interface, the Laplace internal pressure of surface nanobubbles exceeds substantially the outside ambient pressure, and the experimentally observed long term stability is in conflict with estimates of gas transport rates and predicted surface nanobubble lifetimes. Despite recent explanations of both the stability and the unusual nanoscopic contact angles, the development of new co-localization approaches and the adequate analysis of AFM data of surface nanobubbles are important as a means to confirm the gaseous nature and correctly estimate the interfacial curvature.

  19. Scanning thermal microscopy based on a modified atomic force microscope combined with pyroelectric detection

    Science.gov (United States)

    Antoniow, J.-S.; Chirtoc, M.; Trannoy, N.; Raphael, O.; Pelzl, J.

    2005-06-01

    We propose a novel approach in scanning thermal microscopy of layered samples. The thermal probe (ThP) (Wollaston wire) acts as a local a.c. heat source at the front of a sample layer deposited on a pyroelectric (PE) sensor. The PE signal is proportional to the heat wave transmitted through the sample. The ThP and PE signals can be used to generate complementary thermal conductivity maps and with some restrictions, thermal diffusivity maps of the sample. Additionally, the topography map is obtained in the usual way from the atomic force microscope. We give the theoretical background for the interpretation of PE signal obtained at low and at high frequency, and we demonstrate that it carries information on the thermal diffusivity of a test sample (12 μm thick PET polymer sheet). Finally, we discuss the contributions of heat transfer channels between ThP and sample, and the role of contact thermal resistance.

  20. Saponaria officinalis karyology and karyotype by means of image analyzer and atomic force microscopy.

    Science.gov (United States)

    Di Bucchianico, S; Venora, G; Lucretti, S; Limongi, T; Palladino, L; Poma, A

    2008-10-01

    The aim of this work was to offer a contribution to the characterization of taxonomic entity of Saponaria officinalis (2n = 28; an herbaceous perennial species; saporin, a type 1 Ribosome Inactivating Protein, is present in leaves and seeds) by a cytogenetic and karyomorphological approach. We investigated the karyotype's morphometry correlated with Stebbin's symmetric index; the same information has been used for computing the indices resemblance between chromosomes (REC), symmetric indices (SYI), and total form (TF%) which allow the comparison between species and evaluation of karyological evolution. Fluorescence intensities of the stained nuclei were measured by a flow cytometer and, for the first time, values for nuclear DNA content were estimated by comparing nuclei fluorescence intensities of the test population with those of appropriate internal DNA standards. Our study is also aimed to introduce chromosomal volumes, which were determined by atomic force microscopy (AFM), as novel karyomorphological parameter which could allow for chromosome discrimination especially when tiny ones are present.

  1. Automated cantilever exchange and optical alignment for High-throughput, parallel atomic force microscopy

    CERN Document Server

    Bijnagte, Tom; Kramer, Lukas; Dekker, Bert; Herfst, Rodolf; Sadeghian, Hamed

    2016-01-01

    In atomic force microscopy (AFM), the exchange and alignment of the AFM cantilever with respect to the optical beam and position-sensitive detector (PSD) are often performed manually. This process is tedious and time-consuming and sometimes damages the cantilever or tip. To increase the throughput of AFM in industrial applications, the ability to automatically exchange and align the cantilever in a very short time with sufficient accuracy is required. In this paper, we present the development of an automated cantilever exchange and optical alignment instrument. We present an experimental proof of principle by exchanging various types of AFM cantilevers in 6 seconds with an accuracy better than 2 um. The exchange and alignment unit is miniaturized to allow for integration in a parallel AFM. The reliability of the demonstrator has also been evaluated. Ten thousand continuous exchange and alignment cycles were performed without failure. The automated exchange and alignment of the AFM cantilever overcome a large ...

  2. Atomic force microscopy imaging of polyurethane nanoparticles onto different solid substrates

    Energy Technology Data Exchange (ETDEWEB)

    Beddin Fritzen-Garcia, Mauricia [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); POLIMAT, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil)], E-mail: maurifritzen@hotmail.com; Giehl Zanetti-Ramos, Betina [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Schweitzer de Oliveira, Cristian [Laboratorio de Filmes Finos e Superficies, Departamento de Fisica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Soldi, Valdir [POLIMAT, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Avelino Pasa, Andre [Laboratorio de Filmes Finos e Superficies, Departamento de Fisica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Creczynski-Pasa, Tania Beatriz [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil)

    2009-03-01

    Atomic force microscopy (AFM) is a technique suited for characterizing nanoparticles on solid surfaces because it offers the capability of 3D visualization and quantitative information about the topography of the samples. In the present work, contact-mode AFM has been applied to imaging polyurethane nanoparticles formulated from a natural triol and isophorone diisocyanate (IPDI) in the presence of poly(ethylene glycol) (PEG). The colloidal polymeric system was deposited on mica, hydrophilic and hydrophobic silicon solid substrates to evaluate the size and shape of the nanoparticles. Our data showed that the nanoparticles were better distributed on mica and hydrophilic silicon. From the analysis of line-scan profiles we obtained different values for the ratio between the diameter and the height of the nanoparticles, indicating that the shape of the particles depends on the interaction between the nanoparticles and the substrate.

  3. Investigation of Adsorption of Xanthan Gum on Enamel by Tapping Mode Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    LI Hao-ying

    2004-01-01

    By using tapping mode atomic force microscopy(TMAFM), a polymer layer was found on the enamel surface after the exposure to xanthan gum solutions. The layer thickness is closely related to the exposure time and the concentration of xanthan gum solution. The thickness data were evaluated by a Kruskal-Wallis test and Box-Whisker Plot at a 95% confidence level(p<0. 05), and a statistically significant difference among the thickness data groups was demonstrated. After the exposure to 1000, 400, 100 mg/L xanthan gum solutions, the mean of layer thickness at the adsorption equilibrium is in the ranges of 103.5-122.06,82.4-88. 94 and 45.27-55. 55 nm, respectively. This phenomenon suggests that the viscosity modifying agents in the beverage might be adsorbed on the enamel surface during consumption, which may form a barrier that can protect the enamel from being attacked by acid and therefore reduce dental erosion.

  4. Magnetically-modulated atomic force microscopy for analysis of soft matter systems.

    Science.gov (United States)

    Kageshima, Masami

    2012-11-01

    Experimental method of studying viscoelasticity, a common idea to understand properties of microscopic biological soft matter systems, especially single biopolymer chains, using atomic force microscopy (AFM) with magnetically- driven cantilever is surveyed. The experimental setup of applying well-characterized excitation to the cantilever and the analysis method to derive the viscoelasticity of the system under study are briefly introduced. Examples of measuring viscoelasticity of single peptide molecule and single titin molecule are shown. Considering the close relation of viscoelasticity and the time-scale for nonequilibrium dynamics in soft matter, extension of the method to a frequency-resolved analysis is attempted. A result of measuring viscoelasticity spectrum of a single dextran chain is shown. Challenges in further progress of the method are also described.

  5. Monitoring the elasticity changes of HeLa cells during mitosis by atomic force microscopy

    Science.gov (United States)

    Jiang, Ningcheng; Wang, Yuhua; Zeng, Jinshu; Ding, Xuemei; Xie, Shusen; Yang, Hongqin

    2016-10-01

    Cell mitosis plays a crucial role in cell life activity, which is one of the important phases in cell division cycle. During the mitosis, the cytoskeleton micro-structure of the cell changed and the biomechanical properties of the cell may vary depending upon different mitosis stages. In this study, the elasticity property of HeLa cells during mitosis was monitored by atomic force microscopy. Also, the actin filaments in different mitosis stages of the cells were observed by confocal imaging. Our results show that the cell in anaphase is stiffer than that in metaphase and telophase. Furthermore, lots of actin filaments gathered in cells' center area in anaphase, which contributes to the rigidity of the cell in this phase. Our findings demonstrate that the nano-biomechanics of living cells could provide a new index for characterizing cell physiological states.

  6. Application of atomic force microscopy as a nanotechnology tool in food science.

    Science.gov (United States)

    Yang, Hongshun; Wang, Yifen; Lai, Shaojuan; An, Hongjie; Li, Yunfei; Chen, Fusheng

    2007-05-01

    Atomic force microscopy (AFM) provides a method for detecting nanoscale structural information. First, this review explains the fundamentals of AFM, including principle, manipulation, and analysis. Applications of AFM are then reported in food science and technology research, including qualitative macromolecule and polymer imaging, complicated or quantitative structure analysis, molecular interaction, molecular manipulation, surface topography, and nanofood characterization. The results suggested that AFM could bring insightful knowledge on food properties, and the AFM analysis could be used to illustrate some mechanisms of property changes during processing and storage. However, the current difficulty in applying AFM to food research is lacking appropriate methodology for different food systems. Better understanding of AFM technology and developing corresponding methodology for complicated food systems would lead to a more in-depth understanding of food properties at macromolecular levels and enlarge their applications. The AFM results could greatly improve the food processing and storage technologies.

  7. Statistical investigations of an ENIG Nickel film morphology by Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Germanicus Rosine Coq

    2016-01-01

    Full Text Available The morphology of a Nickel layer grown by an Electroless Nickel Immersion Gold (ENIG technique used for microelectronics interconnections is determined by Atomic Force Microscopy (AFM investigations. The root mean square (rms roughness, determined over a scanned area is a function of the AFM scanned area size. In this work, we propose to consider the dynamic scale theory and the power spectrum density (PSD analysis in order to perform a comprehensive determination of the surface properties of the ENIG nickel layer. Results highlight the existence of a first regime with a roughness exponent of 0.95 and a fractal dimension (DF of the nickel film about 2.05. This case study is presented in order to propose further investigations. In fact, same experimental procedure should be performed in a magnetic shielded zone where a very low noise level is available such as the Low-Noise Underground Laboratory (LSBB of Rustrel (France.

  8. Examination of native and carbamide peroxide-bleached human tooth enamel by atomic force microscopy.

    Science.gov (United States)

    Mahringer, Christoph; Fureder, Monika; Kastner, Markus; Ebner, Andreas; Hinterdorfer, Peter; Vitkov, Ljubomir; Hannig, Matthias; Kienberger, Ferry; Schilcher, Kurt

    2009-10-01

    Atomic force microscopy (AFM) was used to study the effects of bleaching on the morphology of the enamel surface with nanoscale resolution. Samples of human tooth enamel with native (pumiced) or fine-polished surfaces were examined before and after bleaching with 30% carbamide peroxide. The obtained profilometric AFM data revealed significant morphological surface alterations. After 1 h of bleaching, the surface roughness increased significantly from 19 +/- 4nm to 33 +/- 5 nm. Six-hour bleaching did not produce any significant further increase in enamel surface roughness. The interrod junction depth raised more than twice after 1 h of bleaching. After 6 h of bleaching, a further and significant increase in interrod junction depth was recorded. This alteration might be a consequence of oxidation and a subsequent partial lysis of the tooth enamel matrix proteins.

  9. Reactivity of Ozone with Solid Potassium Iodide Investigated by Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mulleregan, Alice; Brown, Matthew A.; Ashby, Paul D.; Ogletree, D. Frank; Salmeron, Miquel; Hemminger, John C.

    2008-04-14

    The reaction of ozone with the (100) plane of solid potassium iodide (KI) was investigated using atomic force microscopy (AFM). The reaction forming potassium iodate (KIO{sub 3}) initiates at step edges prior to reacting on the flat terraces. Small domains of KIO{sub 3}, initially 3.8 {angstrom} in height are formed on the top of step edges. Following reaction at the step edge, domains of KIO{sub 3} are formed across the terraces. With prolonged exposure to ozone, KIO{sub 3} domains nucleate further growth until the surface is evenly covered with KIO{sub 3} particles that are 4-6 nm in height, at which point the surface is passivated and the reaction terminates.

  10. Surface kinetic roughening caused by dental erosion: An atomic force microscopy study

    Science.gov (United States)

    Quartarone, Eliana; Mustarelli, Piercarlo; Poggio, Claudio; Lombardini, Marco

    2008-05-01

    Surface kinetic roughening takes place both in case of growth and erosion processes. Teeth surfaces are eroded by contact with acid drinks, such as those used to supplement mineral salts during sporting activities. Calcium-phosphate based (CPP-ACP) pastes are known to reduce the erosion process, and to favour the enamel remineralization. In this study we used atomic force microscopy (AFM) to investigate the surface roughening during dental erosion, and the mechanisms at the basis of the protection role exerted by a commercial CPP-ACP paste. We found a statistically significant difference (proughness of surfaces exposed and not exposed to the acid solutions. The treatment with the CPP-ACP paste determined a statistically significant reduction of the roughness values. By interpreting the AFM results in terms of fractal scaling concepts and continuum stochastic equations, we showed that the protection mechanism of the paste depends on the chemical properties of the acid solution.

  11. Atomic force microscopy study of anion intercalation into highly oriented pyrolytic graphite

    Energy Technology Data Exchange (ETDEWEB)

    Alliata, D.; Haering, P.; Haas, O.; Koetz, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegenthaler, H. [University of Berne (Switzerland)

    1999-08-01

    In the context of ion transfer batteries, we studied highly oriented pyrolytic graphite (HOPG) in perchloric acid, as a model to elucidate the mechanism of electrochemical intercalation in graphite. Aim of the work is the local and time dependent investigation of dimensional changes of the host material during electrochemical intercalation processes on the nanometer scale. We used atomic force microscopy (AFM), combined with cyclic voltammetry, as in-situ tool of analysis during intercalation and expulsion of perchloric anions into the HOPG electrodes. According to the AFM measurements, the HOPG interlayer spacing increases by 32% when perchloric anions intercalate, in agreement with the formation of stage IV of graphite intercalation compounds. (author) 3 figs., 3 refs.

  12. Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Oyoshi, K., E-mail: oyoshi.keiji@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

    2010-11-15

    Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

  13. Advanced tip design for liquid phase vibration mode atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Muramatsu, Hiroshi; Yamamoto, Yuji [School of Bionics, Tokyo University of Technology, 1404-1 Katakura, Hachioji, Tokyo 192-0982 (Japan); Shigeno, Masatsugu; Shirakawabe, Yoshiharu; Inoue, Akira [Technology Center, Seiko Instruments Inc., 563 Takatsukashinden, Matsudo, Chiba 271-2222 (Japan); Kim, Woo-Sik [Department of Chemical Engineering, Kyunghee University, Kyungki-Do 449-701 (Korea, Republic of); Kim, Seung Jin; Chang, Sang-Mok [Department of Chemical Engineering, Hadan 840, Saha-Gu, Busan 604-714 (Korea, Republic of); Kim, Jong Min [Department of Chemical Engineering, Hadan 840, Saha-Gu, Busan 604-714 (Korea, Republic of)], E-mail: jmkim3@dau.ac.kr

    2008-03-24

    We have fabricated polymer tips for atomic force microscopy in order to elucidate the effects of tip length and shape on cantilever vibration damping in liquids. The vibration damping is investigated by measuring the vibration amplitude of cantilevers as a function of tip-sample distance. The cantilever with a short tip provides a higher damping effect over long tip-sample distances. When the vibration amplitude was rescaled to show the effect of the cantilever width on oscillation damping, the vibration amplitude of cantilevers with various tip lengths was similarly obtained in a long distance range over 50 {mu}m. This similarity is explained by an acoustic damping model in which an acoustic wave is generated by the cantilever. Finally, the results indicate a cantilever with a sufficiently long tip compared to the cantilever width can dramatically reduce the long-range damping effect in a liquid environment.

  14. Atomic Force Microscopy Investigation of Morphological and Nanomechanical Properties of Pseudomonas aeruginosa Cells

    DEFF Research Database (Denmark)

    Mortensen, Ninell Pollas

    2008-01-01

    Atomic Force Microscopy (AFM) is unique in the aspect of studying living biological sample under physiological conditions. AFM was invented in 1986 by Binnig and Gerber and began in the early 1990’s to be implemented in life science. AFM can give a detailed three dimensional image of an intact cell...... caused by the dehydration. When visualizing bacteria in liquid the image resolution is reduced, but the bacteria are kept in the natural environment and therefore not subject to the same degree of artifact formation as observed for dehydrated bacteria. However, when imaging rode-shape Gram...... spectrum diagnostic tool originally visualized. Low antibody-antigen affinity and inefficient exposure of the antibody recognition sites could be an explanation for the lack of success. Work presented in this thesis proves what powerful tool AFM is in bacteriology. AFM of bacteria in liquid can be used...

  15. Topographic characterization of unworn contact lenses assessed by atomic force microscopy and wavelet transform.

    Science.gov (United States)

    Ţălu, Ştefan; StȨpień, Krzysztof; Caglayan, Mustafa Oguzhan

    2015-11-01

    This paper analyses the three-dimensional (3-D) surface morphology of optic surface of unworn contact lenses (CLs) using atomic force microscopy (AFM) and wavelet transform. Refractive powers of all lens samples were 2.50 diopters. Topographic images were acquired in contact mode in air-conditioned medium (35% RH, 23°C). Topographic measurements were taken over a 5 µm × 5 µm area with 512 pixel resolution. Resonance frequency of the tip was 65 kHz. The 3-D surface morphology of CL unworn samples revealed (3-D) micro-textured surfaces that can be analyzed using (AFM) and wavelet transform. AFM and wavelet transform are accurate and sensitive tools that may assist CL manufacturers in developing CLs with optimal surface characteristics.

  16. Observation of nuclear track in organic material by atomic force microscopy in real time during etching

    CERN Document Server

    Palmino, F; Labrune, J C

    1999-01-01

    The developments of Atomic Force Microscopy (AFM) allow to investigated solid surfaces with a nanometer scale. These techniques are useful methods allowing direct observation of surface morphologies. Particularly in the nuclear track fields, they offer a new tool to give many new informations on track formation. In this paper we present the preliminary results of a new use of this technique to characterize continuously the formation of the revealed track in a cellulose nitrate detector (LR115) after an alpha particle irradiation. For that, a specific cell has been used to observe, by nano-observations, the evolution of track shapes simultaneously with chemical treatment. Thus, the track shape evolution has been studied; visualizing the evolution of the tracks in real time, in situ during the chemical etching process.

  17. RSC remodeling of oligo-nucleosomes: an atomic force microscopy study

    CERN Document Server

    Montel, Fabien; Menoni, Hervé; Angelov, Dimitar; Dimitrov, Stéfan; Faivre-Moskalenko, Cendrine

    2010-01-01

    RSC is an essential chromatin remodeling factor that is required for the control of several processes including transcription, repair and replication. The ability of RSC to relocate centrally positioned mononucleosomes at the end of nucleosomal DNA is firmly established, but the data on RSC action on oligo-nucleosomal templates remains still scarce. By using Atomic Force Microscopy (AFM) imaging, we have quantitatively studied the RSC- induced mobilization of positioned di- and trinucleosomes as well as the directionality of mobilization on mononucleosomal template labeled at one end with streptavidin. AFM imaging showed only a limited set of distinct configurational states for the remodeling products. No stepwise or preferred directionality of the nucleosome motion was observed. Analysis of the corresponding reaction pathways allows deciphering the mechanistic features of RSC-induced nucleosome relocation. The final outcome of RSC remodeling of oligosome templates is the packing of the nucleosomes at the edg...

  18. Short-term effect of cryotherapy on human scleral tissue by atomic force microscopy.

    Science.gov (United States)

    Lee, Seung Jun; Choi, Samjin; Kim, Moo Sang; Cheong, Youjin; Kwak, Hyung-Woo; Park, Hun-Kuk; Jin, Kyung-Hyun

    2013-01-01

    This study investigated the inflammatory effect of cryotherapy application on collagen matrix network in human infant sclera. Donor scleral tissues taken from three infant patients divided into five groups: control group, sham-treated group, and three cryotreated groups. In the cryotherapy groups, the sclera was treated for 5 s, 10 s, and 20 s with -80°C freezing by a cryosurgical system. The cryotreated reactions were examined using double histological analysis with hematoxylin-eosin and Masson's trichrome, and atomic force microscopy analysis to quantify the diameter and D-banding of collagen fibrils. The infant scleral tissues treated with cryotherapy showed a significantly increased collagen density associated with inflammatory response (p cryotherapy affects the morphology of scleral collagen.

  19. Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

    Science.gov (United States)

    Bathomarco, Ti R. V.; Solorzano, G.; Elias, C. N.; Prioli, R.

    2004-06-01

    The surface of commercial unalloyed titanium, used in dental implants, was analyzed by atomic force microscopy. The morphology, roughness, and surface area of the samples, submitted to mechanically-induced erosion, chemical etching and a combination of both, were compared. The results show that surface treatments strongly influence the dental implant physical and chemical properties. An analysis of the length dependence of the implant surface roughness shows that, for scan sizes larger than 50 μm, the average surface roughness is independent of the scanning length and that the surface treatments lead to average surface roughness in the range of 0.37 up to 0.48 μm. It is shown that the implant surface energy is sensitive to the titanium surface area. As the area increases there is a decrease in the surface contact angle.

  20. Observation of Dislocation Behavior in Graphite by Using Ultrasonic Atomic Force Microscopy

    Science.gov (United States)

    Tsuji, Toshihiro; Irihama, Hiroshi; Yamanaka, Kazushi

    We verify that ultrasonic atomic force microscopy (UAFM) can detect and evaluate subsurface objects with a resolution of around 10nm. We first show that the resonance frequency of UAFM cantilever shows a measurable change due to subsurface low-elasticity layer by a finite element analysis. We then proved the ability of subsurface imaging in a highly oriented pyrolytic graphite (HOPG) specimen. We found a new type of dislocation motion. As a load was applied to the tip, apparent edge-type dislocations (Frank partial dislocations) moved to the direction of climb over distances of 47nm and returned to the original position as the load was removed. To explain this motion, we propose a possible model where the extra half-plane of the dislocation is elastically compressed to shorten its length due to the normal load applied by the tip.

  1. Determination of the actuator sensitivity of electromechanical polypropylene films by atomic force microscopy

    Science.gov (United States)

    Peltonen, Jouko; Paajanen, Mika; Lekkala, Jukka

    2000-10-01

    The actuator functionality of electromechanical polypropylene films was studied using atomic force microscopy. The film carries a permanent electric charge and includes microbubbles as a result of two-dimensional stretching of the film. The thickness change of various film structures covered with electrodes was measured as a function of external voltage. The dependence was found to be nonlinear, the thickness change in the range 0.001%-0.1% of the total film thickness and affected by the internal charge density of the film. Applying a capacitor model including an air gap within the polymer layer enabled the determination of the Young's modulus, the interfacial charge density and the actuator sensitivity of the studied structures.

  2. Boundary slip study on hydrophilic, hydrophobic, and superhydrophobic surfaces with dynamic atomic force microscopy.

    Science.gov (United States)

    Bhushan, Bharat; Wang, Yuliang; Maali, Abdelhamid

    2009-07-21

    Slip length has been measured using the dynamic atomic force microscopy (AFM) method. Unlike the contact AFM method, the sample surface approaches an oscillating sphere with a very low velocity in the dynamic AFM method. During this process, the amplitude and phase shift data are recorded to calculate the hydrodynamic damping coefficient, which is then used to obtain slip length. In this study, a glass sphere with a large radius was glued to the end of an AFM cantilever to measure the slip length on rough surfaces. Experimental results for hydrophilic, hydrophobic, and superhydrophobic surfaces show that the hydrodynamic damping coefficient decreases from the hydrophilic surface to the hydrophobic surface and from the hydrophobic one to the superhydrophobic one. The slip lengths obtained on the hydrophobic and superhydrophobic surfaces are 43 and 236 nm, respectively, which indicates increasing boundary slip from the hydrophobic surface to the superhydrophobic one.

  3. A serial-kinematic nanopositioner for high-speed atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wadikhaye, Sachin P., E-mail: sachin.wadikhaye@uon.edu.au; Yong, Yuen Kuan; Reza Moheimani, S. O. [School of Electrical Engineering and Computer Science, The University of Newcastle, Callaghan, NSW (Australia)

    2014-10-15

    A flexure-guided serial-kinematic XYZ nanopositioner for high-speed Atomic Force Microscopy is presented in this paper. Two aspects influencing the performance of serial-kinematic nanopositioners are studied in this work. First, mass reduction by using tapered flexures is proposed to increased the natural frequency of the nanopositioner. 25% increase in the natural frequency is achieved due to reduced mass with tapered flexures. Second, a study of possible sensor positioning in a serial-kinematic nanopositioner is presented. An arrangement of sensors for exact estimation of cross-coupling is incorporated in the proposed design. A feedforward control strategy based on phaser approach is presented to mitigate the dynamics and nonlinearity in the system. Limitations in design approach and control strategy are discussed in the Conclusion.

  4. Charge transfer on porous silicon membranes studied by current-sensing atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    Bing Xia; Qiang Miao; Jie Chao; Shou Jun Xiao; Hai Tao Wang; Zhong Dang Xiao

    2008-01-01

    A visible rectification effect on the current-voltage curves of metal/porous silicon/p-silicon has been observed by currentsensing atomic force microscopy.The current-voltage curves of porous silicon membranes with different porosities,prepared through variation of etching current density for a constant time,indicate that a higher porosity results in a higher resistance and thus a lower rectification,until the current reaches a threshold at a porosity>55%.We propose that the conductance mode in the porous silicon membrane with porosities>55% is mainly a hopping mechanism between nano-crystallites and an inverse static electric field between the porous silicon and p-Si interface blocks the electron injection from porous silicon to p-Si,but with porosities <55%,electron flows through a direct continuous channel between nano-crystallites.

  5. [Atomic force microscopy fishing of gp120 on immobilized aptamer and its mass spectrometry identification].

    Science.gov (United States)

    Bukharina, N S; Ivanov, Yu D; Pleshakova, T O; Frantsuzov, P A; Andreeva, E Yu; Kaysheva, A L; Izotov, A A; Pavlova, T I; Ziborov, V S; Radko, S P; Archakov, A I

    2015-01-01

    A method of atomic force microscopy-based fishing (AFM fishing) has been developed for protein detection in the analyte solution using a chip with an immobilized aptamer. This method is based on the biospecific fishing of a target protein from a bulk solution onto the small AFM chip area with the immobilized aptamer to this protein used as the molecular probe. Such aptamer-based approach allows to increase an AFM image contrast compared to the antibody-based approach. Mass spectrometry analysis used after the biospecific fishing to identify the target protein on the AFM chip has proved complex formation. Use of the AFM chip with the immobilized aptamer avoids interference of the antibody and target protein peaks in a mass spectrum.

  6. DEVELOPMENT OF A COMPUTER LABORATORY WORK ON ATOMIC FORCE MICROSCOPY OF BIOOBJECTS

    Directory of Open Access Journals (Sweden)

    T. A. Kuchmenko

    2015-01-01

    Full Text Available Innovations in Education are based on the use of new effective educational and information technologies, introduction of progressive forms of organization of educational process, active learning methods. The significant role in the educational system is the development and implementation of virtual labs. For the development of the contemporary science section as bioinformatics, it is necessary to extend the possibility of using computers for processing the information received with the use of modern devices. These research methods include atomic force microscopy. For Students of the specialty 06.05.01 "Bioengineering and Bioinformatics" in the SD "Basics of Nanobiotechnology" it has been developed a virtual laboratory work on "Processing of nanostructured images of biomolecules." The basis for the development of laboratory work was the handbook modified for affordable performance. Laboratory workshop allows you to briefly find out the theory of atomic force microscopy, the organization and the principle of operation of the device. It allows Students to quickly learn the using the program at the AFM image processing Nova 1.0.26.1443. In the laboratory work for the tasks solution the biological objects are selected from the images catalog, and to study and describe of these objects the software is used. Students work with images of biomolecules in the program: change them (increasing, selection of separate areas, evaluate the geometrical parameters, work with 3D-image, writing a description and compare objects with each other. The results are summarized in a table and conclusion. The effectiveness and usefulness of the created laboratory work are proved by the results of Student’s survey and tested in the final and interim certification. This kind of work is suitable for distance learning, to provide a laboratory practicum in SD "Nanotechnology", "Modern methods of analysis" for other specialties as an educational and methodological materials.

  7. Control of the higher eigenmodes of a microcantilever: Applications in atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Karvinen, K.S., E-mail: kai.karvinen@uon.edu.au; Moheimani, S.O.R.

    2014-02-01

    While conventional techniques in dynamic mode atomic force microscopy typically involve the excitation of the first flexural mode of a microcantilever, situations arise where the excitation of higher modes may result in image artefacts. Strong nonlinear coupling between the cantilever modes in liquid environments may result in image artefacts, limiting the accuracy of the image. Similar observations have been made in high-speed contact mode AFM. To address this issue, we propose the application of the modulated–demodulated control technique to attenuate problematic modes to eliminate the image artefacts. The modulated–demodulated control technique is a high-bandwidth technique, which is well suited to the control of next generation of high-speed cantilevers. In addition to potential improvements in image quality, a high-bandwidth controller may also find application in multifrequency AFM experiments. To demonstrate the high-bandwidth nature of the control technique, we construct an amplitude modulation AFM experiment in air utilizing low amplitude setpoints, which ensures that harmonic generation and nonlinear coupling of the modes result in image artefacts. We then utilize feedback control to highlight the improvement in image quality. Such a control technique appears extremely promising in high-speed atomic force microscopy and is likely to have direct application in AFM in liquids. - Highlights: • The excitation of higher eigenmodes can potentially affect the estimated surface topography resulting in image artefacts. • We demonstrated the application of modulated–demodulated control and elimination of image artefacts resulting from the coupling of two modes. • Modulated–demodulated control is well suited to the control of high-frequency resonant dynamics and may find application in liquid/multifrequency AFM experiments.

  8. Antimicrobial properties of analgesic kyotorphin peptides unraveled through atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Marta M.B.; Franquelim, Henri G.; Torcato, Ines M. [Instituto de Medicina Molecular, Faculdade de Medicina de Lisboa, Av. Professor Egas Moniz, 1649-028 Lisboa (Portugal); Ramu, Vasanthakumar G.; Heras, Montserrat; Bardaji, Eduard R. [Laboratori d' Innovacio en Processos i Productes de Sintesi Organica (LIPPSO), Departament de Quimica, Universitat de Girona, Campus Montilivi, 17071 Girona (Spain); Castanho, Miguel A.R.B., E-mail: macastanho@fm.ul.pt [Instituto de Medicina Molecular, Faculdade de Medicina de Lisboa, Av. Professor Egas Moniz, 1649-028 Lisboa (Portugal)

    2012-04-13

    Highlights: Black-Right-Pointing-Pointer New kyotorphin derivatives have antimicrobial properties against S. aureus. Black-Right-Pointing-Pointer Atomic force microscopy show membrane disturbing effects of KTP-NH{sub 2} and IbKTP-NH{sub 2}. Black-Right-Pointing-Pointer None of the KTP derivatives are hemolytic. Black-Right-Pointing-Pointer The minimal peptidic sequence with antimicrobial activity is Tyr-Arg, if amidated. -- Abstract: Antimicrobial peptides (AMPs) are promising candidates as alternatives to conventional antibiotics for the treatment of resistant pathogens. In the last decades, new AMPs have been found from the cleavage of intact proteins with no antibacterial activity themselves. Bovine hemoglobin hydrolysis, for instance, results in AMPs and the minimal antimicrobial peptide sequence was defined as Tyr-Arg plus a positively charged amino acid residue. The Tyr-Arg dipeptide alone, known as kyotorphin (KTP), is an endogenous analgesic neuropeptide but has no antimicrobial activity itself. In previous studies new KTP derivatives combining C-terminal amidation and Ibuprofen (Ib) - KTP-NH{sub 2}, IbKTP, IbKTP-NH{sub 2} - were designed in order to improve KTP brain targeting. Those modifications succeeded in enhancing peptide-cell membrane affinity towards fluid anionic lipids and higher analgesic activity after systemic injection resulted therefrom. Here, we investigated if this affinity for anionic lipid membranes also translates into antimicrobial activity because bacteria have anionic membranes. Atomic force microscopy revealed that KTP derivatives perturbed Staphylococcus aureus membrane structure by inducing membrane blebbing, disruption and lysis. In addition, these peptides bind to red blood cells but are non-hemolytic. From the KTP derivatives tested, amidated KTP proves to be the most active antibacterial agent. The combination of analgesia and antibacterial activities with absence of toxicity is highly appealing from the clinical point of view

  9. Atomic force microscopy with nanoelectrode tips for high resolution electrochemical, nanoadhesion and nanoelectrical imaging

    Science.gov (United States)

    Nellist, Michael R.; Chen, Yikai; Mark, Andreas; Gödrich, Sebastian; Stelling, Christian; Jiang, Jingjing; Poddar, Rakesh; Li, Chunzeng; Kumar, Ravi; Papastavrou, Georg; Retsch, Markus; Brunschwig, Bruce S.; Huang, Zhuangqun; Xiang, Chengxiang; Boettcher, Shannon W.

    2017-03-01

    Multimodal nano-imaging in electrochemical environments is important across many areas of science and technology. Here, scanning electrochemical microscopy (SECM) using an atomic force microscope (AFM) platform with a nanoelectrode probe is reported. In combination with PeakForce tapping AFM mode, the simultaneous characterization of surface topography, quantitative nanomechanics, nanoelectronic properties, and electrochemical activity is demonstrated. The nanoelectrode probe is coated with dielectric materials and has an exposed conical Pt tip apex of ∼200 nm in height and of ∼25 nm in end-tip radius. These characteristic dimensions permit sub-100 nm spatial resolution for electrochemical imaging. With this nanoelectrode probe we have extended AFM-based nanoelectrical measurements to liquid environments. Experimental data and numerical simulations are used to understand the response of the nanoelectrode probe. With PeakForce SECM, we successfully characterized a surface defect on a highly-oriented pyrolytic graphite electrode showing correlated topographical, electrochemical and nanomechanical information at the highest AFM-SECM resolution. The SECM nanoelectrode also enabled the measurement of heterogeneous electrical conductivity of electrode surfaces in liquid. These studies extend the basic understanding of heterogeneity on graphite/graphene surfaces for electrochemical applications.

  10. Atomic force microscopy (AFM) study of thick lamellar stacks of phospholipid bilayers

    CERN Document Server

    Schafer, Arne; Rheinstadter, Maikel C

    2007-01-01

    We report an Atomic Force Microscopy (AFM) study on thick multi lamellar stacks of approx. 10 mum thickness (about 1500 stacked membranes) of DMPC (1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine) deposited on silicon wafers. These thick stacks could be stabilized for measurements under excess water or solution. From force curves we determine the compressional modulus B and the rupture force F_r of the bilayers in the gel (ripple), the fluid phase and in the range of critical swelling close to the main transition. AFM allows to measure the compressional modulus of stacked membrane systems and values for B compare well to values reported in the literature. We observe pronounced ripples on the top layer in the Pbeta' (ripple) phase and find an increasing ripple period Lambda_r when approaching the temperature of the main phase transition into the fluid Lalpha phase at about 24 C. Metastable ripples with 2Lambda_r are observed. Lambda_r also increases with increasing osmotic pressure, i.e., for different concent...

  11. Passive microrheology of normal and cancer cells after ML7 treatment by atomic force microscopy

    Science.gov (United States)

    Lyapunova, Elena; Nikituk, Alexander; Bayandin, Yuriy; Naimark, Oleg; Rianna, Carmela; Radmacher, Manfred

    2016-08-01

    Mechanical properties of living cancer and normal thyroidal cells were investigated by atomic force microscopy (AFM). Cell mechanics was compared before and after treatment with ML7, which is known to reduce myosin activity and induce softening of cell structures. We recorded force curves with extended dwell time of 6 seconds in contact at maximum forces from 500 pN to 1 nN. Data were analyzed within different frameworks: Hertz fit was applied in order to evaluate differences in Young's moduli among cell types and conditions, while the fluctuations of the cantilever in contact with cells were analyzed with both conventional algorithms (probability density function and power spectral density) and multifractal detrended fluctuation analysis (MF-DFA). We found that cancer cells were softer than normal cells and ML7 had a substantial softening effect on normal cells, but only a marginal one on cancer cells. Moreover, we observed that all recorded signals for normal and cancer cells were monofractal with small differences between their scaling parameters. Finally, the applicability of wavelet-based methods of data analysis for the discrimination of different cell types is discussed.

  12. Energy Landscape of Alginate-Epimerase Interactions Assessed by Optical Tweezers and Atomic Force Microscopy.

    Directory of Open Access Journals (Sweden)

    Armend Gazmeno Håti

    Full Text Available Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase-polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ, lifetimes in the absence of external perturbation (τ0 and free energies (ΔG# were determined for the different epimerase-alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate

  13. Temperature and force dependence of electron transport via the copper protein azurin: conductive probe atomic force microscopy measurements

    CERN Document Server

    Li, Wenjie; Amdursky, Nadav; Cohen, Sidney R; Pecht, Israel; Sheves, Mordechai; Cahen, David

    2012-01-01

    We report conducting probe atomic force microscopy (CP-AFM) measurements of electron transport (ETp), as a function of temperature and force, through monolayers of holo-azurin (holo-Az) and Cu-depleted Az (apo-Az) that retain only their tightly bound water, immobilized on gold surfaces. The changes in CP-AFM current-voltage (I-V) curves for holo-Az and apo-Az, measured between 250 - 370K, are strikingly different. While ETp across holo-Az at low force (6 nN) is temperature-independent over the whole examined range, ETp across apo-Az is thermally activated, with calculated activation energy of 600\\pm100 meV. These results confirm our results of macroscopic contact area ETp measurements via holo- and apo-Az, as a function of temperature, where the crucial role of the Cu redox centre has been observed. While increasing the applied tip force from 6 to 12 nN did not significantly change the temperature dependence of ETp via apo-Az, ETp via holo-Az changed qualitatively, namely from temperature-independent at 6 nN ...

  14. Lipid domain formation and ligand-receptor distribution in lipid bilayer membranes investigated by atomic force microscopy

    DEFF Research Database (Denmark)

    Kaasgaard, Thomas; Mouritsen, O.G.; Jørgensen, K.

    2002-01-01

    A novel experimental technique, based on atomic force microscopy (AFM), is proposed to visualize the lateral organization of membrane systems in the nanometer range. The technique involves the use of a ligand-receptor pair, biotin-avidin, which introduces a height variation on a solid-supported l......A novel experimental technique, based on atomic force microscopy (AFM), is proposed to visualize the lateral organization of membrane systems in the nanometer range. The technique involves the use of a ligand-receptor pair, biotin-avidin, which introduces a height variation on a solid...

  15. Molecular Processes Studied at a Single-Molecule Level Using DNA Origami Nanostructures and Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Ilko Bald

    2014-09-01

    Full Text Available DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates.

  16. Evaluating the morphology of erythrocyte population: An approach based on atomic force microscopy and flow cytometry.

    Science.gov (United States)

    Ghosh, Sayari; Chakraborty, Ishita; Chakraborty, Monojit; Mukhopadhyay, Ashis; Mishra, Raghwendra; Sarkar, Debasish

    2016-04-01

    Erythrocyte morphology is gaining importance as a powerful pathological index in identifying the severity of any blood related disease. However, the existing technique of quantitative microscopy is highly time consuming and prone to personalized bias. On the other hand, relatively unexplored, complementary technique based on flow cytometry has not been standardized till date, particularly due to the lack of a proper morphological scoring scale. In this article, we have presented a new approach to formulate a non-empirical scoring scale based on membrane roughness (R(rms)) data obtained from atomic force microscopy. Subsequently, the respective morphological quantifier of the whole erythrocyte population, commonly known as morphological index, was expressed as a function of highest correlated statistical parameters of scattered signal profiles generated by flow cytometry. Feed forward artificial neural network model with multilayer perceptron architecture was used to develop the intended functional form. High correlation coefficient (R(2) = 0.95), even for model-formulation exclusive samples, clearly indicates the universal validity of the proposed model. Moreover, a direct pathological application of the proposed model has been illustrated in relation to patients, diagnosed to be suffering from a wide variety of cancer.

  17. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes

    Directory of Open Access Journals (Sweden)

    Gemma Rius

    2015-01-01

    Full Text Available Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  18. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes.

    Science.gov (United States)

    Rius, Gemma; Lorenzoni, Matteo; Matsui, Soichiro; Tanemura, Masaki; Perez-Murano, Francesc

    2015-01-01

    Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  19. An integrated instrumental setup for the combination of atomic force microscopy with optical spectroscopy.

    Science.gov (United States)

    Owen, R J; Heyes, C D; Knebel, D; Röcker, C; Nienhaus, G U

    2006-07-01

    In recent years, the study of single biomolecules using fluorescence microscopy and atomic force microscopy (AFM) techniques has resulted in a plethora of new information regarding the physics underlying these complex biological systems. It is especially advantageous to be able to measure the optical, topographical, and mechanical properties of single molecules simultaneously. Here an AFM is used that is especially designed for integration with an inverted optical microscope and that has a near-infrared light source (850 nm) to eliminate interference between the optical experiment and the AFM operation. The Tip Assisted Optics (TAO) system consists of an additional 100 x 100-microm(2) X-Y scanner for the sample, which can be independently and simultaneously used with the AFM scanner. This allows the offset to be removed between the confocal optical image obtained with the sample scanner and the simultaneously acquired AFM topography image. The tip can be positioned exactly into the optical focus while the user can still navigate within the AFM image for imaging or manipulation of the sample. Thus the tip-enhancement effect can be maximized and it becomes possible to perform single molecule manipulation experiments within the focus of a confocal optical image. Here this is applied to simultaneous measurement of single quantum dot fluorescence and topography with high spatial resolution.

  20. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Andrew; Butte, Manish J., E-mail: manish.butte@stanford.edu [Department of Pediatrics, Division of Immunology, Allergy and Rheumatology, Stanford University, Stanford, California 94305 (United States)

    2014-08-04

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  1. Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Derek G. Gray

    2015-11-01

    Full Text Available Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from aqueous suspensions of cellulose nanocrystals (CNC was investigated by polarized light microscopy, optical profilometry and atomic force microscopy (AFM. An attempt is made to interpret qualitatively the observed textures in terms of the orientation of the cellulose nanocrystals in the suspensions and films, and the changes in orientation caused by the evaporative process. Mass transfer within the evaporating droplet resulted in the formation of raised rings whose magnitude depended on the degree of pinning of the receding contact line. AFM of dry films at short length scales showed a radial orientation of the CNC at the free surface of the film, along with a radial height variation with a period of approximately P/2, ascribed to the anisotropic shrinkage of the chiral nematic structure.

  2. Advances in research on structural characterisation of agricultural products using atomic force microscopy.

    Science.gov (United States)

    Liu, Dongli; Cheng, Fang

    2011-03-30

    Atomic force microscopy (AFM) has many unique features compared with other conventional microscopies, such as high magnification with high resolution, minimal sample preparation, acquiring 2D and 3D images at the same time, observing ongoing processes directly, the possibility of manipulating macromolecules, etc. As a nanotechnology tool, AFM has been used to investigate the nanostructure of materials in many fields. This mini-review focuses mainly on its latest application to characterise the macromolecular nanostructure and surface topography of agricultural products. First the fundamentals of AFM are briefly explained. Then the macromolecular nanostructure information on agricultural products from AFM images is introduced by exploring the structure-function relationship in three aspects: agricultural product processing, agricultural product ripening and storage, and genetic and environmental factors. The surface topography characterisation of agricultural products using AFM is also discussed. The results reveal that AFM could be a powerful nanotechnology tool to acquire a deeper understanding of the mechanisms of structure and quality variations of agricultural products, which could be instructive in improving processing and storage technologies, and AFM is also helpful to reveal the essential nature of a product at nanoscale.

  3. Advanced fabrication process for combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes.

    Science.gov (United States)

    Eifert, Alexander; Mizaikoff, Boris; Kranz, Christine

    2015-01-01

    An advanced software-controlled focused ion beam (FIB) patterning process for the fabrication of combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes is reported. FIB milling is a standard process in scanning probe microscopy (SPM) for specialized SPM probe fabrication. For AFM-SECM, milling of bifunctional probes usually requires several milling steps. Milling such complex multi-layer/multi-material structures using a single milling routine leads to significantly reduced fabrication times and costs. Based on an advanced patterning routine, a semi-automated FIB milling routine for fabricating combined AFM-SECM probes with high reproducibility is presented with future potential for processing at a wafer level. The fabricated bifunctional probes were electrochemically characterized using cyclic voltammetry, and their performance for AFM-SECM imaging experiments was tested. Different insulation materials (Parylene-C and SixNy) have been evaluated with respect to facilitating the overall milling process, the influence on the electrochemical behavior and the long-term stability of the obtained probes. Furthermore, the influence of material composition and layer sequence to the overall shape and properties of the combined probes were evaluated.

  4. Combining nanoscale optical phenomena with atomic force microscopy for cellular studies

    Science.gov (United States)

    Amini, Sina; Sun, Zhe; Meininger, Gerald A.; Meissner, Kenith E.

    2012-03-01

    Evanescent Waves (EWs) and Förster Resonance Energy Transfer (FRET) concepts combined with Atomic Force Microscopy (AFM) have been used for imaging and sensing. For the proposed EW microscopy system, Quantum Dot (QD) embedded Polystyrene microspheres are mounted on AFM cantilevers. When excited by laser, QDs luminescence couples to the Whispering Gallery Modes (WGMs) in the periphery of the microsphere. The resultant EWs extend on the order of 100 nm from the surface of the microsphere. These EWs decay exponentially and are explored as a tool to excite fluorescent labeled trans-membrane and near-membrane proteins. For the FRET system, QD coated silica microspheres are conjugated with fibronectin and mounted on AFM cantilevers. Moving the sphere down to the surface of the RFP-αv integrin tagged cells, fibronectins on the microsphere surface bind to integrins on the cell surface and FRET is observed between the QDs (donor) and RFP (acceptor). The detected fluorescence for the imaging system and the FRET efficiency for the sensing system are both functions of cell surface protein density. These innovative nanoscale imaging and sensing systems can be used to obtain unique dynamic data from living cells to improve understanding of cell adhesion and mechanobiology in cells.

  5. Different patterns of collagen-proteoglycan interaction: a scanning electron microscopyand atomic force microscopy study

    Directory of Open Access Journals (Sweden)

    A Ruggeri

    2009-12-01

    Full Text Available The extracellular matrix of unfixed, unstained rat corneal stroma, visualized with high-resolution scanning electron microscopy and atomic force microscopy after minimal preliminary treatment, appears composed of straight, parallel, uniform collagen fibrils regularly spaced by a three-dimensional, irregular network of thin, delicate proteoglycan filaments. Rat tail tendon, observed under identical conditions, appears instead made of heterogeneous, closely packed fibrils interwoven with orthogonal proteoglycan filaments. Pre-treatment with cupromeronic blue just thickens the filaments without affecting their spatial layout. Digestion with chondroitinase ABC rids the tendon matrix of all its interconnecting filaments while the corneal stroma architecture remains virtually unaffected, its fibrils always being separated by an evident interfibrillar spacing which is never observed in tendon. Our observations indicate that matrix proteoglycans are responsible for both the highly regular interfibrillar spacing which is distinctive of corneal stroma, and the strong interfibrillar binding observed in tendon. These opposite interaction patterns appear to be distinctive of different proteo- glycan species. The molecular details of proteoglycan interactions are still incompletely understood and are the subject of ongoing research.

  6. High-speed atomic force microscopy shows that annexin V stabilizes membranes on the second timescale

    Science.gov (United States)

    Miyagi, Atsushi; Chipot, Christophe; Rangl, Martina; Scheuring, Simon

    2016-09-01

    Annexins are abundant cytoplasmic proteins that can bind to negatively charged phospholipids in a Ca2+-dependent manner, and are known to play a role in the storage of Ca2+ and membrane healing. Little is known, however, about the dynamic processes of protein-Ca2+-membrane assembly and disassembly. Here we show that high-speed atomic force microscopy (HS-AFM) can be used to repeatedly induce and disrupt annexin assemblies and study their structure, dynamics and interactions. Our HS-AFM set-up is adapted for such biological applications through the integration of a pumping system for buffer exchange and a pulsed laser system for uncaging caged compounds. We find that biochemically identical annexins (annexin V) display different effective Ca2+ and membrane affinities depending on the assembly location, providing a wide Ca2+ buffering regime while maintaining membrane stabilization. We also show that annexin is membrane-recruited and forms stable supramolecular assemblies within ˜5 s in conditions that are comparable to a membrane lesion in a cell. Molecular dynamics simulations provide atomic detail of the role played by Ca2+ in the reversible binding of annexin to the membrane surface.

  7. Single molecule atomic force microscopy of aerolysin pore complexes reveals unexpected star-shaped topography.

    Science.gov (United States)

    He, Jianfeng; Wang, Jiabin; Hu, Jun; Sun, Jielin; Czajkowsky, Daniel Mark; Shao, Zhifeng

    2016-04-01

    Aerolysin is the paradigmatic member of a large family of toxins that convert from a water-soluble monomer/dimer into a membrane-spanning oligomeric pore. While there is x-ray crystallographic data of its water-soluble conformation, the most recent structural model of the membrane-inserted pore is based primarily on data of water-soluble tetradecamers of mutant protein, together with computational modeling ultimately performed in vacuum. Here we examine this pore model with atomic force microscopy (AFM) of membrane-associated wild-type complexes and all-atom molecular dynamics (MD) simulations in water. In striking contrast to a disc-shaped cap region predicted by the present model, the AFM images reveal a star-shaped complex, with a central ring surrounded by seven radial projections. Further, the MD simulations suggest that the locations of the receptor-binding (D1) domains in the present model are not correct. However, a modified model in which the D1 domains, rather than localized at fixed positions, adopt a wide range of configurations through fluctuations of an intervening linker is compatible with existing data. Thus our work not only demonstrates the importance of directly resolving such complexes in their native environment but also points to a dynamic receptor binding region, which may be critical for toxin assembly on the cell surface.

  8. OPTIMIZATION AND CHARACTERIZATION OF ELECTRON BEAM RESIST USING ATOMIC FORCE MICROSCOPY

    Directory of Open Access Journals (Sweden)

    - Sutikno

    2012-01-01

    Full Text Available Resis negatif ma-N 2403 dan 495 K PMMA memiliki resolusi yang baik untuk aplikasi litografi berkas elektron (EBL. Ketebalanresist optimal memainkan peran penting dalam paparan berkas elektron. Oleh karena itu, dalam penelitian ini, ketebalan darikedua resist yang dioptimalkan menggunakan spincoater dalam jangkauan laju spin 1000-6000 rpm. Semakin laju spin meningkat,ketebalan resist menurun juga. Morfologi permukaan resist dikarakterisasi dengan mikroskop gaya atom. Butir butir resist nampakpanjang. Dalam analisis AFM, permukaan profil resist negatif ma-N 2403 dan 495 K PMMA nampak seperti kerucut. Negative resist ma-N 2403 and 495 K PMMA have good resolution for electron beam lithography (EBL application. The optimumresist thickness plays significant role in e-beam exposure. Therefore, in this research, thicknesses of both resists were optimizedusing spincoater within spin speeds of 1000-6000 rpm. As spin speed increased, resist thickness decreased as well. Morphology ofresist surfaces were characterized using atomic force microscopy (AFM. Grains of resist show long grains. In AFM analyses,surface profiles of negative resist ma-N 2403 and 495 K PMMA show cone peaks.Keywords: e-beam resist; spincoater; e-beam lithography

  9. An ultra-low noise optical head for liquid environment atomic force microscopy

    Science.gov (United States)

    Schlesinger, I.; Kuchuk, K.; Sivan, U.

    2015-08-01

    The design considerations and eventual performance of a new, ultra-low noise optical head for dynamic atomic force microscopy (AFM) are presented. The head, designed specifically for the study of hydration layers and ion organization next to solid surfaces and biomolecules, displays an integrated tip-sample distance noise below 3 pm. The sensitivity of the optical beam deflection sensor, operating at frequencies up to 8.6 MHz (3 dB roll-off), is typically below 10 fm / √{ Hz } , enabling utilization of high frequency cantilevers of low thermal noise for fundamental and higher mode imaging. Exceptional signal stability and low optical noise are achieved by replacing the commonly used laser diode with a helium-neon laser. An integral photothermal excitation of the cantilever produces pure harmonic oscillations, minimizing the generation of higher cantilever modes and deleterious sound waves characterizing the commonly used excitation by a piezoelectric crystal. The optical head is designed to fit on top of the widespread Multimode® (Bruker) piezo-tube and accommodate its commercial liquid cell. The performance of the new AFM head is demonstrated by atomic resolution imaging of a muscovite mica surface in aqueous solution.

  10. Comparison of bacterial adhesion to dental materials of polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) using atomic force microscopy and scanning electron microscopy.

    Science.gov (United States)

    Fang, Jie; Wang, Chuanyong; Li, Yifei; Zhao, Zhihe; Mei, Li

    2016-11-01

    The aim of this study was to compare the bacterial adhesion to denture materials of polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) using atomic force microscopy and scanning electron microscopy. The adhesion forces of living Streptococcus sanguinis and Streptococcus mutans to PET and PMMA were directly measured using atomic force microscopy (AFM) in liquid. Streptococcal biofilms formed on the two material surfaces were investigated and compared using scanning electron microscopy (SEM) and colony-forming units (CFU) counting. Surface roughness and hydrophobicity of PET and PMMA were also measured. The results showed that PET surfaces were significantly smoother and more hydrophilic than PMMA surfaces both with and without a salivary film (p SCANNING 38:665-670, 2016. © 2016 Wiley Periodicals, Inc.

  11. Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles.

    Science.gov (United States)

    Song, Bo; Zhou, Yi; Schönherr, Holger

    2016-11-01

    The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.

  12. Local elasticity and adhesion of nanostructures on Drosophila melanogaster wing membrane studied using atomic force microscopy

    Science.gov (United States)

    Wagner, Ryan; Pittendrigh, Barry R.; Raman, Arvind

    2012-10-01

    Insect wings have a naturally occurring, complex, functional, hierarchical microstructure and nanostructure, which enable a remarkably water-resistant and self-cleaning surface. Insect wings are used as a basis for engineering biomimetic materials; however, the material properties of these nanostructures such as local elastic modulus and adhesion are poorly understood. We studied the wings of the Canton-S strain of Drosophila melanogaster (hereafter referred to as Drosophila) with atomic force microscopy (AFM) to quantify the local material properties of Drosophila wing surface nanostructures. The wings are found to have a hierarchical structure of 10-20 μm long, 0.5-1 μm diameter hair, and at a much smaller scale, 100 nm diameter and 30-60 nm high bumps. The local properties of these nanoscale bumps were studied under ambient and dry conditions with force-volume AFM. The wing membrane was found to have a elastic modulus on the order of 1000 MPa and the work of adhesion between the probe and wing membrane surface was found to be on the order of 100 mJ/m2, these properties are the same order of magnitude as common thermoplastic polymers such as polyethylene. The difference in work of adhesion between the nanoscale bump and membrane does not change significantly between ambient (relative humidity of 30%) or dry conditions. This suggests that the nanoscale bumps and the surrounding membrane are chemically similar and only work to increase hydrophobicity though surface roughening or the geometric lotus effect.

  13. Indentation modulus and hardness of viscoelastic thin films by atomic force microscopy: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Passeri, D., E-mail: daniele.passeri@uniroma1.it [Dipartimento di Energetica, Universita di Roma ' La Sapienza' , Via A. Scarpa 16, 00161 Roma (Italy); Bettucci, A.; Biagioni, A.; Rossi, M.; Alippi, A. [Dipartimento di Energetica, Universita di Roma ' La Sapienza' , Via A. Scarpa 16, 00161 Roma (Italy); Tamburri, E. [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Roma (Italy); Lucci, M.; Davoli, I. [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Roma (Italy); Berezina, S. [Department of Physics, University of Zilina, 01026, Univerzitna 1 Zilina (Slovakia)

    2009-11-15

    We propose a nanoindentation technique based on atomic force microscopy (AFM) that allows one to deduce both indentation modulus and hardness of viscoelastic materials from the force versus penetration depth dependence, obtained by recording the AFM cantilever deflection as a function of the sample vertical displacement when the tip is pressed against (loading phase) and then removed from (unloading phase) the surface of the sample. Reliable quantitative measurements of both indentation modulus and hardness of the investigated sample are obtained by calibrating the technique through a set of different polymeric samples, used as reference materials, whose mechanical properties have been previously determined by standard indentation tests. By analyzing the dependence of the cantilever deflection versus time, the proposed technique allows one to evaluate and correct the effect of viscoelastic properties of the investigated materials, by adapting a post-experiment data processing procedure well-established for standard depth sensing indentation tests. The technique is described in the case of the measurement of indentation modulus and hardness of a thin film of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate), deposited by chronoamperometry on an indium tin oxide (ITO) substrate.

  14. Atomic Force Microscopy of DNA-wrapped Single-walled Carbon Nanotubes in Aqueous Solution.

    Science.gov (United States)

    Hayashida, Takuya; Umemura, Kazuo

    2016-07-01

    We evaluated hybrids of DNA and single-walled carbon nanotubes (SWNTs) in aqueous solution and in air using atomic force microscopy (AFM). Although intensive AFM observations of these hybrids were previously carried out for samples in air, this is the first report on AFM observations of these hybrids in solution. As expected, diameters of DNA-SWNT hybrids dramatically increased in tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid (TE) buffer solution. The data suggest that DNA molecules maintain their structures even on the SWNT surfaces. Furthermore, we simultaneously observed single DNA-SWNT hybrids using three different AFM modes in air and in the TE buffer solution. Height value of the hybrids was largest in the solution, and lowest for the mode that repulsive force is expected in air. For the bare SWNT molecules, height differences among the three AFM modes were much lower than those of the DNA-SWNT hybrids. DNA molecules adsorbed on SWNT surfaces flexibly changed their morphology as well as DNA molecules on flat surfaces such as mica. This is hopeful results for biological applications of DNA-SWNT hybrids. In addition, our results revealed the importance of the single-molecule approach to evaluate DNA structures on SWNT surfaces.

  15. Quantitative Conductive Atomic Force Microscopy on Single-Walled Carbon Nanotube-Based Polymer Composites.

    Science.gov (United States)

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leendert G J; de With, Gijsbertus

    2016-08-03

    Conductive atomic force microscopy (C-AFM) is a valuable technique for correlating the electrical properties of a material with its topographic features and for identifying and characterizing conductive pathways in polymer composites. However, aspects such as compatibility between tip material and sample, contact force and area between the tip and the sample, tip degradation and environmental conditions render quantifying the results quite challenging. This study aims at finding the suitable conditions for C-AFM to generate reliable, reproducible, and quantitative current maps that can be used to calculate the resistance in each point of a single-walled carbon nanotube (SWCNT) network, nonimpregnated as well as impregnated with a polymer. The results obtained emphasize the technique's limitation at the macroscale as the resistance of these highly conductive samples cannot be distinguished from the tip-sample contact resistance. Quantitative C-AFM measurements on thin composite sections of 150-350 nm enable the separation of sample and tip-sample contact resistance, but also indicate that these sections are not representative for the overall SWCNT network. Nevertheless, the technique was successfully used to characterize the local electrical properties of the composite material, such as sample homogeneity and resistance range of individual SWCNT clusters, at the nano- and microscale.

  16. Sequential unfolding of beta helical protein by single-molecule atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    David Alsteens

    Full Text Available The parallel βhelix is a common fold among extracellular proteins, however its mechanical properties remain unexplored. In Gram-negative bacteria, extracellular proteins of diverse functions of the large 'TpsA' family all fold into long βhelices. Here, single-molecule atomic force microscopy and steered molecular dynamics simulations were combined to investigate the mechanical properties of a prototypic TpsA protein, FHA, the major adhesin of Bordetella pertussis. Strong extension forces were required to fully unfold this highly repetitive protein, and unfolding occurred along a stepwise, hierarchical process. Our analyses showed that the extremities of the βhelix unfold early, while central regions of the helix are more resistant to mechanical unfolding. In particular, a mechanically resistant subdomain conserved among TpsA proteins and critical for secretion was identified. This nucleus harbors structural elements packed against the βhelix that might contribute to stabilizing the N-terminal region of FHA. Hierarchical unfolding of the βhelix in response to a mechanical stress may maintain β-helical portions that can serve as templates for regaining the native structure after stress. The mechanical properties uncovered here might apply to many proteins with β-helical or related folds, both in prokaryotes and in eukaryotes, and play key roles in their structural integrity and functions.

  17. Nanoindentation and atomic force microscopy measurements on reactively sputtered TiN coatings

    Indian Academy of Sciences (India)

    Harish C Barshilia; K S Rajam

    2004-02-01

    Titanium nitride (TiN) coatings were deposited by d.c. reactive magnetron sputtering process. The films were deposited on silicon (111) substrates at various process conditions, e.g. substrate bias voltage (B) and nitrogen partial pressure. Mechanical properties of the coatings were investigated by a nanoindentation technique. Force vs displacement curves generated during loading and unloading of a Berkovich diamond indenter were used to determine the hardness () and Young’s modulus () of the films. Detailed investigations on the role of substrate bias and nitrogen partial pressure on the mechanical properties of the coatings are presented in this paper. Considerable improvement in the hardness was observed when negative bias voltage was increased from 100–250 V. Films deposited at |B| = 250 V exhibited hardness as high as 3300 kg/mm2. This increase in hardness has been attributed to ion bombardment during the deposition. The ion bombardment considerably affects the microstructure of the coatings. Atomic force microscopy (AFM) of the coatings revealed fine-grained morphology for the films prepared at higher substrate bias voltage. The hardness of the coatings was found to increase with a decrease in nitrogen partial pressure.

  18. Influence of Halide Solutions on Collagen Networks: Measurements of Physical Properties by Atomic Force Microscopy

    Science.gov (United States)

    Kempe, André; Lackner, Maximilian

    2016-01-01

    The influence of aqueous halide solutions on collagen coatings was tested. The effects on resistance against indentation/penetration on adhesion forces were measured by atomic force microscopy (AFM) and the change of Young's modulus of the coating was derived. Comparative measurements over time were conducted with halide solutions of various concentrations. Physical properties of the mesh-like coating generally showed large variability. Starting with a compact set of physical properties, data disperse after minutes. A trend of increase in elasticity and permeability was found for all halide solutions. These changes were largest in NaI, displaying a logical trend with ion size. However a correlation with concentration was not measured. Adhesion properties were found to be independent of mechanical properties. The paper also presents practical experience for AFM measurements of soft tissue under liquids, particularly related to data evaluation. The weakening in physical strength found after exposure to halide solutions may be interpreted as widening of the network structure or change in the chemical properties in part of the collagen fibres (swelling). In order to design customized surface coatings at optimized conditions also for medical applications, halide solutions might be used as agents with little impact on the safety of patients.

  19. IMPROVED FABRICATION METHOD FOR CARBON NANOTUBE PROBE OF ATOMIC FORCE MICROSCOPY(AFM)

    Institute of Scientific and Technical Information of China (English)

    XU Zongwei; DONG Shen; GUO Liqiu; ZHAO Qingliang

    2006-01-01

    An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function.Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication's difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.

  20. Atomic force microscopy reveals two phases in single stranded DNA self-assembled monolayers

    Science.gov (United States)

    Kosaka, Priscila M.; González, Sheila; Domínguez, Carmen M.; Cebollada, Alfonso; San Paulo, Alvaro; Calleja, Montserrat; Tamayo, Javier

    2013-07-01

    We have investigated the structure of single-stranded (ss) DNA self-assembled monolayers (SAMs) on gold by combining peak force tapping, Kelvin probe and phase contrast atomic force microscopy (AFM) techniques. The adhesion, surface potential and phase shift signals show heterogeneities in the DNA film structure at two levels: microscale and nanoscale; which cannot be clearly discerned in the topography. Firstly, there is multilayer aggregation covering less than 5% of the surface. The DNA multilayers seem to be ordered phases and their existence suggests that DNA end-to-end interaction can play a role in the self-assembly process. Secondly, we find the formation of two phases in the DNA monolayer, which differ both in surface energy and surface potential. We relate the two domains to differences in the packing density and in the ssDNA conformation. The discovered heterogeneities in ssDNA SAMs provide a new scenario in our vision of these relevant films that have direct consequences on their biological, chemical and physical properties.

  1. High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force.

    Science.gov (United States)

    Ren, Juan; Zou, Qingze

    2014-07-01

    In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.

  2. Direct detection by atomic force microscopy of single bond forces associated with the rupture of discrete charge-transfer complexes.

    Science.gov (United States)

    Skulason, Hjalti; Frisbie, C Daniel

    2002-12-18

    Atomic force microscopy (AFM) was used to measure the chemical binding force of discrete electron donor-acceptor complexes formed at the interface between proximal self-assembled monolayers (SAMs). Derivatives of the well-known electron donor N,N,N',N'-tetramethylphenylenediamine (TMPD) and the electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) were immobilized on Au-coated AFM tips and substrates by formation of SAMs of N,N,N'-trimethyl-N'-(10-thiodecyl)-1,4-phenylenediamine (I) and bis(10-(2-((2,5-cyclohexadiene-1,4-diylidene)dimalonitrile))decyl) disulfide (II), respectively. Pull-off forces between modified tips and substrates were measured under CHCl(3) solvent. The mean pull-off forces associated with TMPD/TCNQ microcontacts were more than an order of magnitude larger than the pull-off forces for TMPD/TMPD and TCNQ/TCNQ microcontacts, consistent with the presence of specific charge-transfer interactions between proximal TMPD donors and TCNQ acceptors. Furthermore, histograms of pull-off forces for TMPD/TCNQ contacts displayed 70 +/- 15 pN periodicity, assigned to the rupture of individual TMPD-TCNQ donor-acceptor (charge-transfer) complexes. Both the mean pull-off force and the 70 pN force quantum compare favorably with a contact mechanics model that incorporates the effects of discrete chemical bonds, solvent surface tensions, and random contact area variations in consecutive pull-offs. From the 70 pN force quantum, we estimate the single bond energy to be approximately 4-5 kJ/mol, in reasonable agreement with thermodynamic data. These experiments establish that binding forces due to discrete chemical bonds can be detected directly in AFM pull-off measurements employing SAM modified probes and substrates. Because SAMs can be prepared with a wide range of exposed functional groups, pull-off measurements between SAM-coated tips and substrates may provide a general strategy for directly measuring binding forces associated with a variety of simple

  3. Semi-in situ atomic force microscopy imaging of intracellular neurofilaments under physiological conditions through the 'sandwich' method.

    Science.gov (United States)

    Sato, Fumiya; Asakawa, Hitoshi; Fukuma, Takeshi; Terada, Sumio

    2016-08-01

    Neurofilaments are intermediate filament proteins specific for neurons and characterized by formation of biochemically stable, obligate heteropolymers in vivo While purified or reassembled neurofilaments have been subjected to morphological analyses by electron microscopy and atomic force microscopy, there has been a need for direct imaging of cytoplasmic genuine intermediate filaments with minimal risk of artefactualization. In this study, we applied the modified 'cells on glass sandwich' method to exteriorize intracellular neurofilaments, reducing the risk of causing artefacts through sample preparation. SW13vim(-) cells were double transduced with neurofilament medium polypeptide (NF-M) and alpha-internexin (α-inx). Cultured cells were covered with a cationized coverslip after prestabilization with tannic acid to form a sandwich and then split into two. After confirming that neurofilaments could be deposited on ventral plasma membranes exposed via unroofing, we performed atomic force microscopy imaging semi-in situ in aqueous solution. The observed thin filaments, considered to retain native structures of the neurofilaments, exhibited an approximate periodicity of 50-60 nm along their length. Their structural property appeared to reflect the morphology formed by their constituents, i.e. NF-M and α-inx. The success of semi-in situ atomic force microscopy of exposed bona fide assembled neurofilaments through separating the sandwich suggests that it can be an effective and alternative method for investigating cytoplasmic intermediate filaments under physiological conditions by atomic force microscopy.

  4. Polymorphism of Two-Dimensional Cyanine Dye J-Aggregates and Its Genesis: Fluorescence Microscopy and Atomic Force Microscopy Study.

    Science.gov (United States)

    Prokhorov, Valery V; Perelygina, Olga M; Pozin, Sergey I; Mal'tsev, Eugene I; Vannikov, Anatoly V

    2015-12-01

    Polymorphic J-aggregates of monomethine cyanine dye 3,3'-di(γ-sulfopropyl)-5,5'-dichlorotiamonomethinecyanine (TC) have been studied by fluorescence optical microscopy (FOM) and by atomic force microscopy (AFM). The in situ FOM observations in a solution drop distinguish two J-aggregate morphology classes: flexible strips and rigid rods. The AFM imaging of dried samples reveals a strong J-aggregate structural rearrangement under adsorption on a mica surface with the strips self-folding and the rods squashing into rectangular bilayers and much deeper destruction. In the present work, the following structural conclusions have been drawn on the basis of careful consideration of strip crystal habits and various structural features of squashed/destructed rods: (1) the tubular morphology of TC rods is directly proved by FOM measurements in the solution bulk; (2) the staircase model of molecular arrangement in strips is proposed explaining the characteristic ∼44° skew angle in strip vertices; (3) a model of tube formation by a close-packed helical winding of flexible monolayer strips is proposed and justified which explains the observed J-aggregate polymorphism and strip-to-rod polymorphic transformations in a wide spatiotemporal scale; (4) at a nanoscale, an unexpectedly complex quasi-one-dimensional organization in J-aggregate two-dimensional monolayers is observed by high-resolution AFM imaging of constituent nanostrips separated by a characteristic distance in the range of 6-10 nm. The obtained results indicate that the underlying monolayer structure is the same for all J-aggregate polymorphs.

  5. Cell wall extension results in the coordinate separation of parallel microfibrils: evidence from scanning electron microscopy and atomic force microscopy.

    Science.gov (United States)

    Marga, Francoise; Grandbois, Michel; Cosgrove, Daniel J; Baskin, Tobias I

    2005-07-01

    Enlargement of the cell wall requires separation of cellulose microfibrils, mediated by proteins such as expansin; according to the multi-net growth hypothesis, enlargement passively reorients microfibrils. However, at the molecular scale, little is known about the specific movement of microfibrils. To find out, we examined directly changes in microfibril orientation when walls were extended slowly in vitro under constant load (creep). Frozen-thawed cucumber hypocotyl segments were strained by 20-30% by incubation in pH 4.5 buffer or by incubation of heat-inactivated segments in alpha-expansin or a fungal endoglucanase (Cel12A). Subsequently, the innermost layer of the cell wall was imaged, with neither extraction nor homogenization, by field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). AFM images revealed that sample preparation for FESEM did not appreciably alter cell wall ultrastructure. In both FESEM and AFM, images from extended and non-extended samples appeared indistinguishable. To quantify orientational order, we used a novel algorithm to characterize the fast Fourier transform of the image as a function of spatial frequency. For both FESEM and AFM images, the transforms of non-extended samples were indistinguishable from those of samples extended by alpha-expansin or Cel12A, as were AFM images of samples extended by acidic buffer. We conclude that cell walls in vitro can extend slowly by a creep mechanism without passive reorientation of innermost microfibrils, implying that wall loosening agents act selectively on the cross-linking polymers between parallel microfibrils, rather than more generally on the wall matrix.

  6. Quantitative force and dissipation measurements in liquids using piezo-excited atomic force microscopy: a unifying theory.

    Science.gov (United States)

    Kiracofe, Daniel; Raman, Arvind

    2011-12-02

    The use of a piezoelectric element (acoustic excitation) to vibrate the base of microcantilevers is a popular method for dynamic atomic force microscopy. In air or vacuum, the base motion is so small (relative to tip motion) that it can be neglected. However, in liquid environments the base motion can be large and cannot be neglected. Yet it cannot be directly observed in most AFMs. Therefore, in liquids, quantitative force and energy dissipation spectroscopy with acoustic AFM relies on theoretical formulae and models to estimate the magnitude of the base motion. However, such formulae can be inaccurate due to several effects. For example, a significant component of the piezo excitation does not mechanically excite the cantilever but rather transmits acoustic waves through the surrounding liquid, which in turn indirectly excites the cantilever. Moreover, resonances of the piezo, chip and holder can obscure the true cantilever dynamics even in well-designed liquid cells. Although some groups have tried to overcome these limitations (either by theory modification or better design of piezos and liquid cells), it is generally accepted that acoustic excitation is unsuitable for quantitative force and dissipation spectroscopy in liquids. In this paper the authors present a careful study of the base motion and excitation forces and propose a method by which quantitative analysis is in fact possible, thus opening this popular method for quantitative force and dissipation spectroscopy using dynamic AFM in liquids. This method is validated by experiments in water on mica using a scanning laser Doppler vibrometer, which can measure the actual base motion. Finally, the method is demonstrated by using small-amplitude dynamic AFM to extract the force gradients and dissipation on solvation shells of octamethylcyclotetrasiloxane (OMCTS) molecules on mica.

  7. Dynamic behaviour of dagger-shaped cantilevers for atomic force microscopy

    Science.gov (United States)

    Shen, Kangzhi; Hurley, Donna C.; Turner, Joseph A.

    2004-11-01

    Experimental techniques based on the atomic force microscope (AFM) have been developed for characterizing mechanical properties at the nanoscale and applied to a variety of materials and structures. Atomic force acoustic microscopy (AFAM) is one such technique that uses spectral information of the AFM cantilever as it vibrates in contact with a sample. In this paper, the dynamic behaviour of AFM cantilevers that have a dagger shape is investigated using a power-series method. Dagger-shaped cantilevers have plan-view geometry consisting of a rectangular section at the clamped end and a triangular section at the tip. Their geometry precludes modelling using closed-form expressions. The convergence of the series is demonstrated and the convergence radius is shown to be related to the given geometry. The accuracy and efficiency of the method are investigated by comparison with finite element results for several different cases. AFAM experiments are modelled by including a linear spring at the tip that represents the contact stiffness. The technique developed is shown to be very effective for inversion of experimental frequency information into contact stiffness results for AFAM. In addition, the sensitivities of the frequencies to the contact stiffness are discussed in terms of the various geometric parameters of the problem including the slope, the ratio of the rectangular to triangular lengths and the tip location. Calculations of contact stiffness from experimental data using this model are shown to be very good in comparison with other models. It is anticipated that this approach may be useful for other cantilever geometries as well, such that AFAM accuracy may be improved.

  8. Force spectroscopy of hyaluronan by atomic force microscopy: from hydrogen-bonded networks toward single-chain behavior.

    Science.gov (United States)

    Giannotti, Marina I; Rinaudo, Marguerite; Vancso, G Julius

    2007-09-01

    The conformational behavior of hyaluronan (HA) polysaccharide chains in aqueous NaCl solution was characterized directly at the single-molecule level. This communication reports on one of the first single-chain atomic force microscopy (AFM) experiments performed at variable temperatures, investigating the influence of the temperature on the stability of the HA single-chain conformation. Through AFM single-molecule force spectroscopy, the temperature destabilization of a local structure was proven. This structure involved a hydrogen-bonded network along the polymeric chain, with hydrogen bonds between the polar groups of HA and possibly water, and a change from a nonrandom coil to a random coil behavior was observed when increasing the temperature from 29 +/- 1 to 46 +/- 1 degrees C. As a result of the applied force, this superstructure was found to break progressively at room temperature. The use of a hydrogen-bonding breaker solvent demonstrated the hydrogen-bonded water-bridged nature of the network structure of HA single chains in aqueous NaCl solution.

  9. Imaging and quantitative data acquisition of biological cell walls with Atomic Force Microscopy and Scanning Acoustic Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tittmann, B. R. [Penn State; Xi, X. [Penn State

    2014-09-01

    This chapter demonstrates the feasibility of Atomic Force Microscopy (AFM) and High Frequency Scanning Acoustic Microscopy (HF-SAM) as tools to characterize biological tissues. Both the AFM and the SAM have shown to provide imaging (with different resolution) and quantitative elasticity measuring abilities. Plant cell walls with minimal disturbance and under conditions of their native state have been examined with these two kinds of microscopy. After descriptions of both the SAM and AFM, their special features and the typical sample preparation is discussed. The sample preparation is focused here on epidermal peels of onion scales and celery epidermis cells which were sectioned for the AFM to visualize the inner surface (closest to the plasma membrane) of the outer epidermal wall. The nm-wide cellulose microfibrils orientation and multilayer structure were clearly observed. The microfibril orientation and alignment tend to be more organized in older scales compared with younger scales. The onion epidermis cell wall was also used as a test analog to study cell wall elasticity by the AFM nanoindentation and the SAM V(z) feature. The novelty in this work was to demonstrate the capability of these two techniques to analyze isolated, single layered plant cell walls in their natural state. AFM nanoindentation was also used to probe the effects of Ethylenediaminetetraacetic acid (EDTA), and calcium ion treatment to modify pectin networks in cell walls. The results suggest a significant modulus increase in the calcium ion treatment and a slight decrease in EDTA treatment. To complement the AFM measurements, the HF-SAM was used to obtain the V(z) signatures of the onion epidermis. These measurements were focused on documenting the effect of pectinase enzyme treatment. The results indicate a significant change in the V(z) signature curves with time into the enzyme treatment. Thus AFM and HF-SAM open the door to a systematic nondestructive structure and mechanical property

  10. Methods and apparatus of spatially resolved electroluminescence of operating organic light-emitting diodes using conductive atomic force microscopy

    Science.gov (United States)

    Hersam, Mark C. (Inventor); Pingree, Liam S. C. (Inventor)

    2008-01-01

    A conductive atomic force microscopy (cAFM) technique which can concurrently monitor topography, charge transport, and electroluminescence with nanometer spatial resolution. This cAFM approach is particularly well suited for probing the electroluminescent response characteristics of operating organic light-emitting diodes (OLEDs) over short length scales.

  11. Survival of adhering staphylococci during exposure to a quaternary ammonium compound evaluated by using atomic force microscopy imaging

    NARCIS (Netherlands)

    Crismaru, Mihaela; Asri, Lia ATW; Loontjens, Jacobus; Krom, Bastiaan P; de Vries, Jacob; van der Mei, Henderina; Busscher, Hendrik

    2011-01-01

    Effects of a quaternary ammonium compound (QAC) on the survival of adhering staphylococci on a surface were investigated using atomic force microscopy (AFM). Four strains with different minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) for the QAC were exposed to

  12. Characterization of Bacterial Polysaccharide Capsules and Detection in the Presence of Deliquescent Water by Atomic Force Microscopy

    OpenAIRE

    Su, Hai-Nan; Chen, Zhi-Hua; Liu, Sheng-Bo; Qiao, Li-Ping; Chen, Xiu-Lan; He, Hai-Lun; Zhao, Xian; Zhou, Bai-Cheng; Zhang, Yu-Zhong

    2012-01-01

    We detected polysaccharide capsules from Zunongwangia profunda SM-A87 with atomic force microscopy (AFM). The molecular organization of the capsules at the single-polysaccharide-chain level was reported. Furthermore, we found that with ScanAsyst mode the polysaccharide capsules could be detected even in the presence of deliquescent water covering the capsule.

  13. Structure-dependent behaviours of skin layers studied by atomic force microscopy.

    Science.gov (United States)

    Chang, A C; Liu, B H; Shao, P L; Liao, J D

    2017-03-23

    The multilayer skin provides the physical resistance and strength against the environmental attacks, and consequently plays a significant role in maintaining the mammalian health. Currently, optical microscopy (OM) is the most common method for the research related to skin tissues while with the drawbacks including the possibility of changing the native morphology of the sample with the addition of the chemical or immunological staining and the restricted resolution of images for the direct observation of the tissue structures. To investigate if the function of each tissue is structure-dependent and the how the injured skin returns to the intact condition, we applied atomic force microscopy (AFM) on the sectioned mice-skin to reveal the tissue structures with a nanoscale resolution. From the outermost stratum to the inner layer of the skin tissue, the respectively laminated, fibrous, and brick-like structures were observed and corresponded to various functions. Due to the mechanical differences between the tissue constituents and their boundaries, the sizes and arrangements of the components were characterised and quantified by the mechanical mapping of AFM, which enabled the analytical comparisons between tissue layers. For the wound model, the skin tissues were examined with the initial formation of blood vessels and type-I collagen, which agreed with the stage of healing process estimated by OM but showed more detail information about the evolution of proteins among the skin. In conclusion, the characterisation of the components that consist of skin tissue by AFM enables the connection of the tissue function to the corresponded ultrastructure.

  14. A novel type of colony formation in marine planktonic diatoms revealed by atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Sunčica Bosak

    Full Text Available Diatoms have evolved a variety of colonial life forms in which cells are connected by organic threads, mucilage pads or silicate structures. In this study, we provide the first description of a novel strategy of colony formation among marine planktonic diatoms. Bacteriastrum jadranum forms loose but regular chains with distinct heterovalvate terminal cells. The colonial cells and their siliceous projections, the setae, are not in direct contact; instead, they are enclosed within the optically transparent organic matrix. This cell jacket structure was detected by staining procedure with Alcian Blue, which showed that the polysaccharides are predominant matrix constituents and revealed that the jacket reaches the span of the setae. The scanning electron microscopy (SEM observations showed distinguishable fibrillar network firmly associated with cells. Using atomic force microscopy (AFM, we were able to visualise and characterise the cell jacket structure at molecular resolution. At nanoscale resolution, the cell jacket appears as a cross-linked fibrillar network organised into a recognisable structure. The circular patches of self-repeating pattern (hexagonal pores with openings of 8-100 nm are connected through thicker surrounding fibrils and reinforced by branching fibrils. The pore-forming fibrils within the patches are only 0.6-1.6 nm high, the surrounding fibrils connecting patches are 2.0-2.8 nm high, and the branching fibrils are considerably wider but not higher than 4.0 nm. The discovered polysaccharide fibrillar network is highly organised and delicately structured with a monomolecular fibril height of 0.6 nm. We conclude that the Bacteriastrum polysaccharide jacket represents an essential part of the cell, as the conjunction of the polymer network with the frustule appears to be extremely tight and such specific and unique patterns have never been found in self-assembled polysaccharide gel networks, which are usually encountered in the

  15. DNA Free Energy Landscapes and RNA Nano-Self-Assembly Using Atomic Force Microscopy

    Science.gov (United States)

    Frey, Eric William

    There is an important conceptual lesson which has long been appreciated by those who work in biophysics and related interdisciplinary fields. While the extraordinary behavior of biological matter is governed by its detailed atomic structure and random fluctuations, and is therefore difficult to predict, it can nevertheless be understood within simplified frameworks. Such frameworks model the system as consisting of only one or a few components, and model the behavior of the system as the occupation of a single state out of a small number of states available. The emerging widespread application of nanotechnology, such as atomic force microscopy (AFM), has expanded this understanding in eye-opening new levels of detail by enabling nano-scale control, measurement, and visualization of biological molecules. This thesis describes two independent projects, both of which illuminate this understanding using AFM, but which do so from very different perspectives. The organization of this thesis is as follows. Chapter 1 begins with an experimental background and introduction to AFM, and then describes our setup in both single-molecule manipulation and imaging modes. In Chapter 2, we describe the first project, the motivation for which is to extend methods for the experimental determination of the free energy landscape of a molecule. This chapter relies on the analysis of single-molecule manipulation data. Chapter 3 describes the second project, the motivation for which is to create RNA-based nano-structures suitable for future applications in living mammalian cells. This chapter relies mainly on imaging. Chapters 2 and 3 can thus be read and understood separately.

  16. Nonlinear dynamics of tapping mode atomic force microscopy in the bistable phase

    Science.gov (United States)

    Bahrami, Arash; Nayfeh, Ali H.

    2013-03-01

    Nonlinear dynamics of amplitude modulation atomic force microscopy (AFM) is studied employing a reduced-order model based on a differential quadrature method (DQM). The AFM microcantilever is assumed to be operating in the dynamic contact or tapping mode while the microcantilever tip being initially located in the bistable region. We have found that the DQM is capable of precise prediction of the static bifurcation diagram and natural frequencies of the microcantilever. We have used the DQM to discretize the partial-differential equation governing the microcantilever motion and a finite difference method (FDM) to calculate limit-cycle responses of the AFM tip. It is shown that a combination of the DQM and FDM applied, respectively, to discretize the spatial and temporal derivatives provides an efficient, accurate procedure to address the complicated dynamic behavior exhibited by the AFM probe. The procedure was, therefore, utilized to study the response of the microcantilever to a base harmonic excitation through several numerical examples. We found that the dynamics of the AFM probe in the bistable region is totally different from those in the monostable region.

  17. Atomic force microscopy for the investigation of molecular and cellular behavior.

    Science.gov (United States)

    Ozkan, Alper D; Topal, Ahmet E; Dana, Aykutlu; Guler, Mustafa O; Tekinay, Ayse B

    2016-10-01

    The present review details the methods used for the measurement of cells and their exudates using atomic force microscopy (AFM) and outlines the general conclusions drawn by the mechanical characterization of biological materials through this method. AFM is a material characterization technique that can be operated in liquid conditions, allowing its use for the investigation of the mechanical properties of biological materials in their native environments. AFM has been used for the mechanical investigation of proteins, nucleic acids, biofilms, secretions, membrane bilayers, tissues and bacterial or eukaryotic cells; however, comparison between studies is difficult due to variances between tip sizes and morphologies, sample fixation and immobilization strategies, conditions of measurement and the mechanical parameters used for the quantification of biomaterial response. Although standard protocols for the AFM investigation of biological materials are limited and minor differences in measurement conditions may create large discrepancies, the method is nonetheless highly effective for comparatively evaluating the mechanical integrity of biomaterials and can be used for the real-time acquisition of elasticity data following the introduction of a chemical or mechanical stimulus. While it is currently of limited diagnostic value, the technique is also useful for basic research in cancer biology and the characterization of disease progression and wound healing processes.

  18. Surface Morphology of Ice and Ice with AFGP studied with Atomic Force Microscopy

    Science.gov (United States)

    Zepeda, Salvador; Orme, Christine A.; Yeh, Yin

    2001-03-01

    Water is earth's only naturally occurring inorganic liquid and as such it is not surprising that the special properties of water and ice are responsible for life. As essential as it is for survival of living organisms, it can also cause death by freezing in cold weather organisms causing cells to burst upon expansion and recrystallization. Many organisms have developed a tolerance to both freezing and recrystallization. In particular, certain polar and near polar fish have done so in the form of antifreeze glycoproteins (AFGPs). These proteins suppress the freezing temperature of water and inhibit recrystallization. The focus of our efforts is to understand the mechanism by which these proteins function. The working hypothesis has been a Gibbs-Thomson model in which the protein binds to an ice plane and physically impedes its growth. Atomic force microscopy offers molecular level resolution and this type of phenomenon has been readily investigated for other systems with this technique. We will discuss the results from AFM measurements on single ice crystals carried out in an octane overlayer for both the pure phase and in the presence of AFGPs. Our results implicate a high surface mobility of water molecules in both cases.

  19. Viewing dynamic interactions of proteins and a model lipid membrane with atomic force microscopy.

    Science.gov (United States)

    Quinn, Anthony S; Rand, Jacob H; Wu, Xiao-Xuan; Taatjes, Douglas J

    2013-01-01

    The information covered in this chapter will present a model homogenous membrane preparation technique and dynamic imaging procedure that can be successfully applied to more than one type of lipid study and atomic force microscope (AFM) instrument setup. The basic procedural steps have been used with an Asylum Research MFP-3D BIO and the Bruker (formerly, Veeco) BioScope. The AFM imaging protocol has been supplemented by procedures (not to be presented in this chapter) of ellipsometry, standardized western blotting, and dot-blots to verify appropriate purity and activity of all experimental molecular components; excellent purity and activity level of the lipids, proteins, and drug(s) greatly influence the success of imaging experiments in the scanning probe microscopy field. The major goal of the chapter is to provide detailed procedures for sample preparation and operation of the Asylum Research MFP-3D BIO AFM. In addition, one should be cognizant that our comprehensive description in the use of the MFP-3D BIO's functions for successful image acquisitions and analyses is greatly enhanced by Asylum Research's (AR's) accompanying extensive manual(s), technical notes, and AR's users forum. Ultimately, the stepwise protocol and information will allow novice personnel to begin acquiring quality images for processing and analysis with minimal supervision.

  20. In situ observations of shape evolution during copper dissolution using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cruickshank, B.J.; Gewirth, A.A.; Rynders, R.M.; Alkire, R.C. (Illinois Univ., Urbana, IL (United States). Materials Research Lab.)

    1992-10-01

    In this paper, atomic force microscopy is used to monitor, in situ, the shape evolution of polycrystalline copper during anodic dissolution in 0. 5 M H[sub 2]SO[sub 4]. During dissolution of the copper surface under a small anodic potential (30 mV), an overlayer of material that resulted from mechanical polishing was removed, exposing the underlying grain boundaries. A chemically etched sample was exposed to the same experimental conditions, and no overlayer was observed. Dissolution of the copper bulk metal was monitored under a higher applied potential (100 mV, 0. 5M H[sub 2]SO[sub 4]). The overlayer was immediately removed, and the dissolution produced a nonuniform, crystallographically etched surface. The inhibiting effect of benzotriazole (BTA) on copper dissolution in 0. 5M H[sub 2]SO[sub 4]/20 mM BTA was observed. Copper dissolution did not proceed at 100 mV or 200 mV applied potential; but at 300 mV, rapid localized dissolution resulted in the formation of pit-like features.

  1. Oligomerization states of Bowman-Birk inhibitor by atomic force microscopy and computational approaches.

    Science.gov (United States)

    Silva, Luciano P; Azevedo, Ricardo B; Morais, Paulo C; Ventura, Manuel M; Freitas, Sonia M

    2005-11-15

    Several methods have been applied to study protein-protein interaction from structural and thermodynamic point of view. The present study reveals that atomic force microscopy (AFM), molecular modeling, and docking approaches represent alternative methods offering new strategy to investigate structural aspects in oligomerization process of proteinase inhibitors. The topography of the black-eyed pea trypsin/chymotrypsin inhibitor (BTCI) was recorded by AFM and compared with computational rigid-bodies docking approaches. Multimeric states of BTCI identified from AFM analysis showed globular-ellipsoidal shapes. Monomers, dimers, trimers, and hexamers were the most prominent molecular arrays observed in AFM images as evaluated by molecular volume calculations and corroborated by in silico docking and theoretical approaches. We therefore propose that BTCI adopts stable and well-packed self-assembled states in monomer-dimer-trimer-hexamer equilibrium. Although there are no correlation between specificity and packing efficiency among proteinases and proteinase inhibitors, the AFM and docked BTCI analyses suggest that these assemblies may exist in situ to play their potential function in oligomerization process.

  2. Electrochemical direct writing and erasing of silver nanostructures on phosphate glass using atomic force microscopy

    Science.gov (United States)

    Barna, Shama F.; Jacobs, Kyle E.; Mensing, Glennys A.; Ferreira, Placid M.

    2017-02-01

    This paper reports a liquid-free, mask-less electrochemical direct-write lithographic technique using an atomic force microscopy (AFM) probe for writing silver nanostructures in minutes on an optically transparent substrate. Under ambient conditions, silver is locally and controllably extracted to the surface of superionic (AgI)0.25 (AgPO3)0.75 glass by bringing a conductive AFM probe tip in contact with it, biasing the probe with a negative voltage, and regulating the resulting current. The growth mechanism of the resulting nanostructure is explored by extracting silver with a stationary AFM tip on the surface of the silver. A moving tip was then used to produce continuous lines, solid films and discrete dots of silver by implementing continuous and pulsed current writing approaches. The line dimensions depend on writing speed and current flowing in the electrochemical circuit, while the size and spacing of the dots depend on the parameters (magnitude, duration and frequency) of the current pulses and the writing speed of the AFM tip. Line-widths in the ∼100 nm range are demonstrated. Our investigation also shows that a threshold potential must be overcome to be able to draw and reduce silver ions on the glass surface. When polarity between the electrodes is reversed, the patterned silver ionizes back into the glass, thus offering the capability to erase and rewrite Ag patterns on the glass surface.

  3. Electrical characterization of InAs/GaAs (110) nanostructures by conductive atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Beinik, Igor; Teichert, Christian [Institute of Physics, Montanuniversitaet Leoben (Austria); Diez-Merino, Laura; Tejedor, Paloma [Instituto de Ciencia de Materiales de Madrid (Spain). CSIC

    2009-07-01

    Self-assembled InAs quantum dots and wires have been studied over many years and still they are of great interest for application in nanoelectronics, high-speed spintronic devices, etc. Samples for our investigation were grown by molecular beam epitaxy on misoriented (110) GaAs substrates. Conductive Atomic Force Microscopy (C-AFM) technique was used to study the surface topography and conductivity simultaneously. Comparison of the corresponding cross-section profiles indicated that InAs nucleation takes place on the[1-10]-oriented step bunches, forming 3 nm-high and up to 70 nm-wide wires of variable length. On the other hand,[1-12]-type steps very rarely appeared to be decorated by InAs, also in agreement with previous TEM studies. The presented results prove that C-AFM technique might be successfully applied as a tool for investigation of electrical properties in III-V quantum dots and wires on the nanometer scale.

  4. High-speed Lissajous-scan atomic force microscopy: scan pattern planning and control design issues.

    Science.gov (United States)

    Bazaei, A; Yong, Yuen K; Moheimani, S O Reza

    2012-06-01

    Tracking of triangular or sawtooth waveforms is a major difficulty for achieving high-speed operation in many scanning applications such as scanning probe microscopy. Such non-smooth waveforms contain high order harmonics of the scan frequency that can excite mechanical resonant modes of the positioning system, limiting the scan range and bandwidth. Hence, fast raster scanning often leads to image distortion. This paper proposes analysis and design methodologies for a nonlinear and smooth closed curve, known as Lissajous pattern, which allows much faster operations compared to the ordinary scan patterns. A simple closed-form measure is formulated for the image resolution of the Lissajous pattern. This enables us to systematically determine the scan parameters. Using internal model controllers (IMC), this non-raster scan method is implemented on a commercial atomic force microscope driven by a low resonance frequency positioning stage. To reduce the tracking errors due to actuator nonlinearities, higher order harmonic oscillators are included in the IMC controllers. This results in significant improvement compared to the traditional IMC method. It is shown that the proposed IMC controller achieves much better tracking performances compared to integral controllers when the noise rejection performances is a concern.

  5. Detection of erythrocytes in patients with Waldenstrom macroglobulinemia using atomic force microscopy.

    Science.gov (United States)

    Liu, Junru; Li, Juan

    2014-05-01

    The pathological changes of erythrocytes are detected at the nanometer scale, which is important for revealing the onset of diseases and diagnosis. The aim of this study is to examine the ultrastructural changes of erythrocytes in Waldenström macroglobulinemia (WM) at a nanometer scale. Blood samples were collected from two healthy volunteers, two WM patients, and three multiple myeloma (MM) patients when they were first diagnosed. The changes of morphology in the erythrocytes were studied at the nanometer level by high-resolution atomic force microscopy imaging (AFM). Compared with the healthy controls and the MM patients, there were dramatic deformations in the overall shape and surface membrane of the erythrocytes in WM patients. Healthy, pathological WM, and MM erythrocytes could be distinguished by several morphological parameters, including the width, length, length-to-width ratio, valley, peak, peak-to-valley, and Ra. AFM is able to detect the morphological differences in the red blood cells from WM patients, healthy controls, and MM patients. Therefore, the erythrocyte morphology is an important parameter for the diagnosis of WM, which can be used to distinguish WM from MM. The changes of ultrastructure in red blood cells may provide a clue to reveal the mechanism of WM.

  6. Scanned Probe Oxidation onp-GaAs(100 Surface with an Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Juang Jenh-Yih

    2008-01-01

    Full Text Available AbstractLocally anodic oxidation has been performed to fabricate the nanoscale oxide structures onp-GaAs(100 surface, by using an atomic force microscopy (AFM with the conventional and carbon nanotube (CNT-attached probes. The results can be utilized to fabricate the oxide nanodots under ambient conditions in noncontact mode. To investigate the conversion of GaAs to oxides, micro-Auger analysis was employed to analyze the chemical compositions. The growth kinetics and the associated mechanism of the oxide nanodots were studied under DC voltages. With the CNT-attached probe the initial growth rate of oxide nanodots is in the order of ~300 nm/s, which is ~15 times larger than that obtained by using the conventional one. The oxide nanodots cease to grow practically as the electric field strength is reduced to the threshold value of ~2 × 107 V cm−1. In addition, results indicate that the height of oxide nanodots is significantly enhanced with an AC voltage for both types of probes. The influence of the AC voltages on controlling the dynamics of the AFM-induced nanooxidation is discussed.

  7. Wide-area scanner for high-speed atomic force microscopy.

    Science.gov (United States)

    Watanabe, Hiroki; Uchihashi, Takayuki; Kobashi, Toshihide; Shibata, Mikihiro; Nishiyama, Jun; Yasuda, Ryohei; Ando, Toshio

    2013-05-01

    High-speed atomic force microscopy (HS-AFM) has recently been established. The dynamic processes and structural dynamics of protein molecules in action have been successfully visualized using HS-AFM. However, its maximum scan ranges in the X- and Y-directions have been limited to ~1 μm and ~4 μm, respectively, making it infeasible to observe the dynamics of much larger samples, including live cells. Here, we develop a wide-area scanner with a maximum XY scan range of ~46 × 46 μm(2) by magnifying the displacements of stack piezoelectric actuators using a leverage mechanism. Mechanical vibrations produced by fast displacement of the X-scanner are suppressed by a combination of feed-forward inverse compensation and the use of triangular scan signals with rounded vertices. As a result, the scan speed in the X-direction reaches 6.3 mm/s even for a scan size as large as ~40 μm. The nonlinearity of the X- and Y-piezoelectric actuators' displacements that arises from their hysteresis is eliminated by polynomial-approximation-based open-loop control. The interference between the X- and Y-scanners is also eliminated by the same technique. The usefulness of this wide-area scanner is demonstrated by video imaging of dynamic processes in live bacterial and eukaryotic cells.

  8. Nanomechanical and topographical imaging of living cells by atomic force microscopy with colloidal probes

    Energy Technology Data Exchange (ETDEWEB)

    Puricelli, Luca; Galluzzi, Massimiliano; Schulte, Carsten; Podestà, Alessandro, E-mail: alessandro.podesta@mi.infn.it; Milani, Paolo [CIMaINa and Department of Physics, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)

    2015-03-15

    Atomic Force Microscopy (AFM) has a great potential as a tool to characterize mechanical and morphological properties of living cells; these properties have been shown to correlate with cells’ fate and patho-physiological state in view of the development of novel early-diagnostic strategies. Although several reports have described experimental and technical approaches for the characterization of cellular elasticity by means of AFM, a robust and commonly accepted methodology is still lacking. Here, we show that micrometric spherical probes (also known as colloidal probes) are well suited for performing a combined topographic and mechanical analysis of living cells, with spatial resolution suitable for a complete and accurate mapping of cell morphological and elastic properties, and superior reliability and accuracy in the mechanical measurements with respect to conventional and widely used sharp AFM tips. We address a number of issues concerning the nanomechanical analysis, including the applicability of contact mechanical models and the impact of a constrained contact geometry on the measured Young’s modulus (the finite-thickness effect). We have tested our protocol by imaging living PC12 and MDA-MB-231 cells, in order to demonstrate the importance of the correction of the finite-thickness effect and the change in Young’s modulus induced by the action of a cytoskeleton-targeting drug.

  9. High-bandwidth multimode self-sensing in bimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Michael G. Ruppert

    2016-02-01

    Full Text Available Using standard microelectromechanical system (MEMS processes to coat a microcantilever with a piezoelectric layer results in a versatile transducer with inherent self-sensing capabilities. For applications in multifrequency atomic force microscopy (MF-AFM, we illustrate that a single piezoelectric layer can be simultaneously used for multimode excitation and detection of the cantilever deflection. This is achieved by a charge sensor with a bandwidth of 10 MHz and dual feedthrough cancellation to recover the resonant modes that are heavily buried in feedthrough originating from the piezoelectric capacitance. The setup enables the omission of the commonly used piezoelectric stack actuator and optical beam deflection sensor, alleviating limitations due to distorted frequency responses and instrumentation cost, respectively. The proposed method benefits from a more than two orders of magnitude increase in deflection to strain sensitivity on the fifth eigenmode leading to a remarkable signal-to-noise ratio. Experimental results using bimodal AFM imaging on a two component polymer sample validate that the self-sensing scheme can therefore be used to provide both the feedback signal, for topography imaging on the fundamental mode, and phase imaging on the higher eigenmode.

  10. Cell wall modification in grapevine cells in response to UV stress investigated by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lesniewska, E.; Adrian, M.; Klinguer, A.; Pugin, A

    2004-08-15

    Despite cell wall reinforcement being a well-known defence mechanism of plants, it remains poorly characterized from a physical point of view. The objective of this work was to further describe this mechanism. Vitis vinifera cv Gamay cells were treated with UV-light (254 nm), a well-known elicitor of defence mechanisms in grapevines, and physical cell wall modifications were observed using the atomic force microscopy (AFM) under native conditions. The grapevine cell suspensions were continuously observed in their culture medium from 30 min to 24 h after elicitation. In the beginning, cellulose fibrils covered by a matrix surrounded the control and treated cells. After 3 h, the elicited cells displayed sprouted expansions around the cell wall that correspond to pectin chains. These expansions were not observed on untreated grapevine cells. The AFM tip was used to determine the average surface elastic modulus of cell wall that account for cell wall mechanical properties. The elasticity is diminished in UV-treated cells. In a comparative study, grapevine cells showed the same decrease in cell wall elasticity when treated with a fungal biotic elicitor of defence response. These results demonstrate cell wall strengthening by UV stress.

  11. Correlating anomalous diffusion with lipid bilayer membrane structure using single molecule tracking and atomic force microscopy

    Science.gov (United States)

    Skaug, Michael J.; Faller, Roland; Longo, Marjorie L.

    2011-06-01

    Anomalous diffusion has been observed abundantly in the plasma membrane of biological cells, but the underlying mechanisms are still unclear. In general, it has not been possible to directly image the obstacles to diffusion in membranes, which are thought to be skeleton bound proteins, protein aggregates, and lipid domains, so the dynamics of diffusing particles is used to deduce the obstacle characteristics. We present a supported lipid bilayer system in which we characterized the anomalous diffusion of lipid molecules using single molecule tracking, while at the same time imaging the obstacles to diffusion with atomic force microscopy. To explain our experimental results, we performed lattice Monte Carlo simulations of tracer diffusion in the presence of the experimentally determined obstacle configurations. We correlate the observed anomalous diffusion with obstacle area fraction, fractal dimension, and correlation length. To accurately measure an anomalous diffusion exponent, we derived an expression to account for the time-averaging inherent to all single molecule tracking experiments. We show that the length of the single molecule trajectories is critical to the determination of the anomalous diffusion exponent. We further discuss our results in the context of confinement models and the generating stochastic process.

  12. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy

    Science.gov (United States)

    Lee, Jung Ah; Rok Lim, Young; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae

    2016-10-01

    To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.

  13. Atomic force microscopy evidence for conformational changes of fibronectin adsorbed on unmodified and sulfonated polystyrene surfaces.

    Science.gov (United States)

    Kowalczyńska, Hanna M; Kołos, Robert; Nowak-Wyrzykowska, Małgorzata; Dobkowski, Jacek; Elbaum, Danek; Szczepankiewicz, Andrzej; Kamiński, Jarosław

    2009-12-15

    The effect of polystyrene surface polarity on the conformation of adsorbed fibronectin (FN) has been studied with atomic force microscopy. We demonstrated that bare sulfonated and nonsulfonated polystyrene surfaces featured similar topographies. After the FN adsorption, direct comparison of both types of substrata revealed drastically different topographies, roughness values, and also cell-adhesive properties. This was interpreted in terms of FN conformational changes induced by the surface polarity. At high-solute FN concentrations the multilayer FN adsorption took place resulting, for the sulfonated substratum, in an increase of surface roughness, whereas for the nonsulfonated one the roughness was approximately stable. Conversely, the FN conformation characteristic for the first saturative layer tended to be conserved in the consecutive layers, as evidenced by height histograms. The height of individual FN molecules indicated, consonantly with the derived thickness of the adsorbed protein layer (the latter value being 1.4 nm and 0.6 nm, respectively, for an unmodified and sulfonated polystyrene surface), that molecules are flattened on polar surfaces and more compact on nonsulfonated ones. It was also demonstrated that the FN adsorption and conformation on polymeric substrata, and hence the resultant cell-adhesive properties, depended on the chemistry of the original surface rather than on its topography. Our results also demonstrated the ability of surface polarity to influence the protein conformation and its associated biological activity.

  14. Generating and characterizing the mechanical properties of cell-derived matrices using atomic force microscopy.

    Science.gov (United States)

    Tello, Marta; Spenlé, Caroline; Hemmerlé, Joseph; Mercier, Luc; Fabre, Roxane; Allio, Guillaume; Simon-Assmann, Patricia; Goetz, Jacky G

    2016-02-01

    Mechanical interaction between cells and their surrounding extracellular matrix (ECM) controls key processes such as proliferation, differentiation and motility. For many years, two-dimensional (2D) models were used to better understand the interactions between cells and their surrounding ECM. More recently, variation of the mechanical properties of tissues has been reported to play a major role in physiological and pathological scenarios such as cancer progression. The 3D architecture of the ECM finely tunes cellular behavior to perform physiologically relevant tasks. Technical limitations prevented scientists from obtaining accurate assessment of the mechanical properties of physiologically realistic matrices. There is therefore a need for combining the production of high-quality cell-derived 3D matrices (CDMs) and the characterization of their topographical and mechanical properties. Here, we describe methods that allow to accurately measure the young modulus of matrices produced by various cellular types. In the first part, we will describe and review several protocols for generating CDMs matrices from endothelial, epithelial, fibroblastic, muscle and mesenchymal stem cells. We will discuss tools allowing the characterization of the topographical details as well as of the protein content of such CDMs. In a second part, we will report the methodologies that can be used, based on atomic force microscopy, to accurately evaluate the stiffness properties of the CDMs through the quantification of their young modulus. Altogether, such methodologies allow characterizing the stiffness and topography of matrices deposited by the cells, which is key for the understanding of cellular behavior in physiological conditions.

  15. Ultrathin Topological Insulator Bi 2 Se 3 Nanoribbons Exfoliated by Atomic Force Microscopy

    KAUST Repository

    Hong, Seung Sae

    2010-08-11

    Ultrathin topological insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi2Se 3), a single Dirac-cone topological insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi2Se3 nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1-2 QLs and 4-5 QLs. Transport measurement carried out on an exfoliated (>5 QLs) Bi2Se3 device shows nonmetallic temperature dependence of resistance, in sharp contrast to the metallic behavior seen in thick (>50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for studying the transition from quantum spin Hall surface to edge states. © 2010 American Chemical Society.

  16. Atomic force microscopy observation of the enamel roughness and depth profile after phosphoric acid etching.

    Science.gov (United States)

    Loyola-Rodriguez, Juan Pablo; Zavala-Alonso, Veronica; Reyes-Vela, Enrique; Patiño-Marin, Nuria; Ruiz, Facundo; Anusavice, Kenneth J

    2010-01-01

    The aim was to compare the enamel surface roughness (ESR) and absolute depth profile (ADP) (mean peak-to-valley height) by atomic force microscopy (AFM) before and after using four different phosphoric acids. A total of 160 enamel samples from 40 upper premolars were prepared. The inclusion criterion was that the teeth have healthy enamel. Exclusion criteria included any of the following conditions: facial restorations, caries lesions, enamel hypoplasia and dental fluorosis. Evaluations of the ESR and ADP were carried out by AFM. The Mann-Whitney U-test was used to compare continuous variables and the Wilcoxon test was used to analyze the differences between before and after etching. There were statistically significant differences (P roughness and absolute depth before and after using four different phosphoric acids in healthy enamel; Etch-37 and Scotchbond Etching Gel showed higher profiles after etching (P roughness and ADP before and after using four different phosphoric acids in healthy enamel. However, consistently Etch-37 and Scotchbond Etching Gel showed the highest increase regarding the ESR and ADP after etching healthy enamel. AFM was a useful tool to study site-specific structural topography changes in enamel after phosphoric acid etching.

  17. High-speed atomic force microscopy reveals structural dynamics of amyloid β1-42 aggregates.

    Science.gov (United States)

    Watanabe-Nakayama, Takahiro; Ono, Kenjiro; Itami, Masahiro; Takahashi, Ryoichi; Teplow, David B; Yamada, Masahito

    2016-05-24

    Aggregation of amyloidogenic proteins into insoluble amyloid fibrils is implicated in various neurodegenerative diseases. This process involves protein assembly into oligomeric intermediates and fibrils with highly polymorphic molecular structures. These structural differences may be responsible for different disease presentations. For this reason, elucidation of the structural features and assembly kinetics of amyloidogenic proteins has been an area of intense study. We report here the results of high-speed atomic force microscopy (HS-AFM) studies of fibril formation and elongation by the 42-residue form of the amyloid β-protein (Aβ1-42), a key pathogenetic agent of Alzheimer's disease. Our data demonstrate two different growth modes of Aβ1-42, one producing straight fibrils and the other producing spiral fibrils. Each mode depends on initial fibril nucleus structure, but switching from one growth mode to another was occasionally observed, suggesting that fibril end structure fluctuated between the two growth modes. This switching phenomenon was affected by buffer salt composition. Our findings indicate that polymorphism in fibril structure can occur after fibril nucleation and is affected by relatively modest changes in environmental conditions.

  18. A Semi-Automated Positioning System for contact-mode Atomic Force Microscopy (AFM).

    Science.gov (United States)

    Roy, Rajarshi; Chen, Wenjin; Cong, Lei; Goodell, Lauri A; Foran, David J; Desai, Jaydev P

    2013-04-01

    Contact mode Atomic Force Microscopy (CM-AFM) is popularly used by the biophysics community to study mechanical properties of cells cultured in petri dishes, or tissue sections fixed on microscope slides. While cells are fairly easy to locate, sampling in spatially heterogeneous tissue specimens is laborious and time-consuming at higher magnifications. Furthermore, tissue registration across multiple magnifications for AFM-based experiments is a challenging problem, suggesting the need to automate the process of AFM indentation on tissue. In this work, we have developed an image-guided micropositioning system to align the AFM probe and human breast-tissue cores in an automated manner across multiple magnifications. Our setup improves efficiency of the AFM indentation experiments considerably. Note to Practitioners: Human breast tissue is by nature heterogeneous, and in the samples we studied, epithelial tissue is formed by groups of functional breast epithelial cells that are surrounded by stromal tissue in a complex intertwined way. Therefore sampling a specific cell type on an unstained specimen is very difficult. To aid us, we use digital stained images of the same tissue annotated by a certified pathologist to identify the region of interest (ROI) at a coarse magnification and an image-guided positioning system to place the unstained tissue near the AFM probe tip. Using our setup, we could considerably reduce AFM operating time and we believe that our setup is a viable supplement to commercial AFM stages with limited X-Y range.

  19. Topographical characterization of Ar-bombarded Si(1 1 1) surfaces by atomic force microscopy

    CERN Document Server

    Niebieskikwiat, D G; Pregliasco, G R; Gayone, J E; Grizzi, O; Sanchez, E A

    2002-01-01

    We used atomic force microscopy to study the topographical changes induced on Si(1 1 1) surfaces by 10-22 keV Ar sup + bombardment. The irradiation was carried on normal to the surface with doses in the 1-60x10 sup 1 sup 6 ions/cm sup 2 range. We observed a first generation of blisters at a critical dose around 3x10 sup 1 sup 6 ions/cm sup 2 , which flakes off at 19x10 sup 1 sup 6 ions/cm sup 2 , and a second generation of smaller blisters between 35 and 45x10 sup 1 sup 6 ions/cm sup 2. Measurements of the mean surface height show that at low irradiation doses the surface inflates because of voids produced by Ar sup + implantation. For doses greater than 20x10 sup 1 sup 6 Ar sup + /cm sup 2 the height decreases linearly because of sputtering, with a slope corresponding to a sputtering yield of 1.4. Finally, we present electron spectra produced during grazing proton bombardment of samples whose topography has been modified by Ar irradiation.

  20. Analysis on surface nanostructures present in hindwing of dragon fly (Sympetrum vulgatum) using atomic force microscopy.

    Science.gov (United States)

    Selvakumar, Rajendran; Karuppanan, Karthikeyan K; Pezhinkattil, Radhakrishnan

    2012-12-01

    The present study involves the analysis of surface nanostructures and its variation present in the hind wing of dragon fly (Sympetrum vulgatum) using atomic force microscopy (AFM). The hindwing was dissected into 4 parts (D1-D4) and each dissected section was analyzed using AFM in tapping mode at different locations. The AFM analysis revealed the presence of irregular shaped nanostructures on the surface of the wing membrane with size varying between 83.25±1.79 nm to 195.08±10.25 nm. The size and shape of the nanostructure varied from tip (pterostigma) to the costa part. The membrane surface of the wing showed stacked arrangement leading to increase in size of the nanostructure. Such arrangement of the nanostructures has lead to the formation of nanometer sized valleys of different depth and length on the membrane surface giving them ripple wave morphology. The average roughness of the surface nanostructures varied from 18.58±3.12 nm to 24.25±8.33 nm. Surfaces of the wings had positive skewness in D1, D2 and D4 regions and negative skewness in D3 region. These surface nanostructures may contribute asymmetric resistance under mechanical loading during the flight by increasing the bending and torsional resistance of the wing.

  1. Charge transport in CdTe solar cells revealed by conductive tomographic atomic force microscopy

    Science.gov (United States)

    Luria, Justin; Kutes, Yasemin; Moore, Andrew; Zhang, Lihua; Stach, Eric A.; Huey, Bryan D.

    2016-11-01

    The influence of microstructural defects on the device properties in CdTe remains largely unknown. This is partly because characterization techniques have been unable to image electrical pathways throughout three-dimensional grains and grain boundaries with nanoscale resolution. Here, we employ a conductive and tomographic variation of atomic force microscopy to study charge transport at the nanoscale in a functioning thin-film solar cell with 12.3% efficiency. Images of electric current collected through the device thickness reveal spatially dependent short-circuit and open-circuit performance, and confirm that grain boundaries are preferential pathways for electron transport. Results on samples with and without cadmium chloride treatment reveal little difference in grain structure at the microscale, with samples without treatment showing almost no photocurrent either at planar defects or at grain boundaries. Our results supports an energetically orthogonal transport system of grain boundaries and interconnected planar defects as contributing to optimal solar cell performance, contrary to the conventional wisdom of the deleterious role of planar defects on polycrystalline thin-film solar cells.

  2. Morphology Change of C60 Islands on Organic Crystals Observed by Atomic Force Microscopy.

    Science.gov (United States)

    Freund, Sara; Hinaut, Antoine; Pawlak, Rémy; Liu, Shi-Xia; Decurtins, Silvio; Meyer, Ernst; Glatzel, Thilo

    2016-06-28

    Organic-organic heterojunctions are nowadays highly regarded materials for light-emitting diodes, field-effect transistors, and photovoltaic cells with the prospect of designing low-cost, flexible, and efficient electronic devices.1-3 However, the key parameter of optimized heterojunctions relies on the choice of the molecular compounds as well as on the morphology of the organic-organic interface,4 which thus requires fundamental studies. In this work, we investigated the deposition of C60 molecules at room temperature on an organic layer compound, the salt bis(benzylammonium)bis(oxalato)cupurate(II), by means of noncontact atomic force microscopy. Three-dimensional molecular islands of C60 having either triangular or hexagonal shapes are formed on the substrate following a "Volmer-Weber" type of growth. We demonstrate the dynamical reshaping of those C60 nanostructures under the local action of the AFM tip at room temperature. The dissipated energy is about 75 meV and can be interpreted as the activation energy required for this migration process.

  3. RSC remodeling of oligo-nucleosomes: an atomic force microscopy study.

    Science.gov (United States)

    Montel, Fabien; Castelnovo, Martin; Menoni, Hervé; Angelov, Dimitar; Dimitrov, Stefan; Faivre-Moskalenko, Cendrine

    2011-04-01

    The 'remodels structure of chromatin' (RSC) complex is an essential chromatin remodeling factor that is required for the control of several processes including transcription, repair and replication. The ability of RSC to relocate centrally positioned mononucleosomes at the end of nucleosomal DNA is firmly established, but the data on RSC action on oligo-nucleosomal templates remains still scarce. By using atomic force microscopy (AFM) imaging, we have quantitatively studied the RSC-induced mobilization of positioned di- and trinucleosomes as well as the directionality of mobilization on mononucleosomal template labeled at one end with streptavidin. AFM imaging showed only a limited set of distinct configurational states for the remodeling products. No stepwise or preferred directionality of the nucleosome motion was observed. Analysis of the corresponding reaction pathways allows deciphering the mechanistic features of RSC-induced nucleosome relocation. The final outcome of RSC remodeling of oligosome templates is the packing of the nucleosomes at the edge of the template, providing large stretches of DNA depleted of nucleosomes. This feature of RSC may be used by the cell to overcome the barrier imposed by the presence of nucleosomes.

  4. Single-Molecular Imaging of Anticoagulation Factor I from Snake Venom by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    XU,Xiao-Long(徐小龙); ZHOU,Yun-Shen(周云申); LIU,Qing-Liang(刘清亮); HOU,Jian-Guo(侯建国); YANG,Jing-Long(杨金龙); XIE,Yong-Shu(解永树)

    2002-01-01

    Anticoagulation factor I (ACF I) from the venom of Agkistrodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy (AFM) with high-resolution using glutaraldehyde as a coupling agent. The physical adsorption and covalent binding of ACF I onto the mica show very different surface topographies. The former exhibits the characteristic strand-like structure with much less reproducibility, the latter displays a elliptic granular structure with better reproducibility, which suggests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde. A small-scale AFM amplitude-mode image clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7.4 nm× 3.6 nm × 3.1 nm, which is very similar to the size determined from the crystal structure of ACF I.

  5. Single—Molecular Imaging of Anticoagulation Factor I From Snake Venom by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    徐小龙; 刘清亮; 等

    2002-01-01

    Anticoagulation factor I( ACF I) from the venom of Agki-strodom acutus is a binding protein to activanted coagulation fac tor X(FXa) and possesses marked anticoagulant acivity,Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy(AFM) with high-resolu-tion using glutaraldehyde as a coupling agent.The physical adsoprtion and covalent binding of ACF I onto the mica show very different surface topographies,The former exhibits the characteristic strand-like structure with much less reproducibility,the latter displays a elliptic granular structure with better repro-ducibility,which sugests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde.A small-scale AFM amplitude -mode impage clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7.4nm×3.6nm×3.1nm ,which is very similar to the size determined from the crystal structure of ACF I.

  6. Conductive Atomic Force Microscopy Applied to CdTe/CdS Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Moutinho, H. R.; Dhere, R. G.; Jiang, C. -S.; Al-Jassim, M. M.; Kazmerski, L. L.

    2004-08-01

    In this work we describe for the first time the use of conductive atomic force microscopy (C-AFM) in the study of CdTe/CdS solar cells, before and after the etching processes used in device fabrication. C-AFM is a new technique that provides information on the electrical properties of the sample in conjunction with topographic images with high lateral resolution. At the same time, this technique allows for the generation of I-V curves at very well-defined locations. A potential is applied between the sample and a very sharp tip, which scans the sample in contact mode. The current images showed that different CdTe grains produce different contrast. Etching the CdTe with a bromine/methanol solution enhanced the current along grains boundaries when compared to the intragrain material. Etching with a solution of nitric and phosphoric acids did not show this effect. Instead, it increased the current through the whole sample surface.

  7. Electrical properties of CdTe/CdS solar cells investigated with conductive atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Moutinho, H.R. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401 (United States)]. E-mail: helio_moutinho@nrel.gov; Dhere, R.G. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401 (United States); Jiang, C.-S. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401 (United States); Al-Jassim, M.M. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401 (United States); Kazmerski, L.L. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401 (United States)

    2006-08-30

    We report on the application of conductive atomic force microscopy (C-AFM) for studying the electrical properties of CdTe/CdS solar cells, and discuss the advantages and limitations of this technique. C-AFM is a new technique that uses the tip of an AFM to apply a potential between the tip and the sample, resulting in high spatial-resolution current images, as well as current versus voltage curves. The analyses were made before and after the standard vapor CdCl{sub 2} treatment, as well as two etching processes, using solutions of bromine/methanol and nitric-phosphoric acids. The current images from the untreated and CdCl{sub 2}-treated samples showed grains with different contrasts, due to differences in electrical conductivity or a nonuniform surface. The bromine/methanol etch resulted in more conductive grain boundaries as compared to intragrain material, while the nitric/phosphoric etch increased the conductivity of the whole film close to the surface and resulted in films with significant photocurrent.

  8. Atomic force microscopy study of nano-physiological response of ladybird beetles to photostimuli.

    Directory of Open Access Journals (Sweden)

    Natalia V Guz

    Full Text Available BACKGROUND: Insects are of interest not only as the most numerous and diverse group of animals but also as highly efficient bio-machines varying greatly in size. They are the main human competitors for crop, can transmit various diseases, etc. However, little study of insects with modern nanotechnology tools has been done. METHODOLOGY/PRINCIPAL FINDINGS: Here we applied an atomic force microscopy (AFM method to study stimulation of ladybird beetles with light. This method allows for measuring of the internal physiological responses of insects by recording surface oscillations in different parts of the insect at sub-nanometer amplitude level and sub-millisecond time. Specifically, we studied the sensitivity of ladybird beetles to light of different wavelengths. We demonstrated previously unknown blindness of ladybird beetles to emerald color (∼500nm light, while being able to see UV-blue and green light. Furthermore, we showed how one could study the speed of the beetle adaptation to repetitive flashing light and its relaxation back to the initial stage. CONCLUSIONS: The results show the potential of the method in studying insects. We see this research as a part of what might be a new emerging area of "nanophysiology" of insects.

  9. Practical loss tangent imaging with amplitude-modulated atomic force microscopy

    Science.gov (United States)

    Proksch, Roger; Kocun, Marta; Hurley, Donna; Viani, Mario; Labuda, Aleks; Meinhold, Waiman; Bemis, Jason

    2016-04-01

    Amplitude-modulated (AM) atomic force microscopy (AFM), also known as tapping or AC mode, is a proven, reliable, and gentle imaging method with widespread applications. Previously, the contrast in AM-AFM has been difficult to quantify. AFM loss tangent imaging is a recently introduced technique that recasts AM mode phase imaging into a single term tan δ that includes both the dissipated and stored energy of the tip-sample interaction. It promises fast, versatile mapping of variations in near-surface viscoelastic properties. However, experiments to date have generally obtained values larger than expected for the viscoelastic loss tangent of materials. Here, we explore and discuss several practical considerations for AFM loss tangent imaging experiments. A frequent limitation to tapping in air is Brownian (thermal) motion of the cantilever. This fundamental noise source limits the accuracy of loss tangent estimation to approximately 0.01 phase transitions, even in the presence of such non-ideal interactions. These results help understand the limits and opportunities not only of this particular technique but also of AM mode with phase imaging in general.

  10. Cantilever tilt causing amplitude related convolution in dynamic mode atomic force microscopy.

    Science.gov (United States)

    Wang, Chunmei; Sun, Jielin; Itoh, Hiroshi; Shen, Dianhong; Hu, Jun

    2011-01-01

    It is well known that the topography in atomic force microscopy (AFM) is a convolution of the tip's shape and the sample's geometry. The classical convolution model was established in contact mode assuming a static probe, but it is no longer valid in dynamic mode AFM. It is still not well understood whether or how the vibration of the probe in dynamic mode affects the convolution. Such ignorance complicates the interpretation of the topography. Here we propose a convolution model for dynamic mode by taking into account the typical design of the cantilever tilt in AFMs, which leads to a different convolution from that in contact mode. Our model indicates that the cantilever tilt results in a dynamic convolution affected by the absolute value of the amplitude, especially in the case that corresponding contact convolution has sharp edges beyond certain angle. The effect was experimentally demonstrated by a perpendicular SiO(2)/Si super-lattice structure. Our model is useful for quantitative characterizations in dynamic mode, especially in probe characterization and critical dimension measurements.

  11. Nanoscale Quantifying the Effects of Targeted Drug on Chemotherapy in Lymphoma Treatment Using Atomic Force Microscopy.

    Science.gov (United States)

    Li, Mi; Xiao, Xiubin; Liu, Lianqing; Xi, Ning; Wang, Yuechao

    2016-10-01

    The applications of targeted drugs in treating cancers have significantly improved the survival rates of patients. However, in the clinical practice, targeted drugs are commonly combined with chemotherapy drugs, causing that the exact contribution of targeted drugs to the clinical outcome is difficult to evaluate. Quantitatively investigating the effects of targeted drugs on chemotherapy drugs on cancer cells is useful for us to understand drug actions and design better drugs. The advent of atomic force microscopy (AFM) provides a powerful tool for probing the nanoscale physiological activities of single live cells. In this paper, the detailed changes in cell morphology and mechanical properties were quantified on single lymphoma cells during the actions of rituximab (a monoclonal antibody targeted drug) and two chemotherapy drugs (cisplatin and cytarabine) by AFM. AFM imaging revealed the distinct changes of cellular ultramicrostructures induced by the drugs. The changes of cellular mechanical properties after the drug stimulations were measured by AFM indenting. The statistical histograms of cellular surface roughness and mechanical properties quantitatively showed that rituximab could remarkably strengthen the killing effects of chemotherapy drugs. The study offers a new way to quantify the synergistic interactions between targeted drugs and chemotherapy drugs at the nanoscale, which will have potential impacts on predicting the efficacies of drug combinations before clinical treatments.

  12. DNA Studies Using Atomic Force Microscopy: Capabilities for Measurement of Short DNA Fragments

    Directory of Open Access Journals (Sweden)

    Dalong ePang

    2015-01-01

    Full Text Available Short DNA fragments, resulting from ionizing radiation induced DNA double strand breaks (DSBs, or released from cells as a result of physiological processes and circulating in the blood stream, may play important roles in cellular function and potentially in disease diagnosis and early intervention. The size distribution of DNA fragments contribute to knowledge of underlining biological processes. Traditional techniques used in radiation biology for DNA fragment size measurements lack the resolution to quantify short DNA fragments. For the measurement of cell-free circulating DNA (ccfDNA, real time quantitative Polymerase Chain Reaction (q-PCR provides quantification of DNA fragment sizes, concentration and specific gene mutation. A complementary approach, the imaging-based technique using Atomic Force Microscopy (AFM provides direct visualization and measurement of individual DNA fragments. In this review, we summarize and discuss the application of AFM-based measurements of DNA fragment sizes. Imaging of broken plasmid DNA, as a result of exposure to ionizing radiation, as well as ccfDNA in clinical specimens offer an innovative approach for studies of short DNA fragments and their biological functions.

  13. Finite element simulation for the mechanical characterization of soft biological materials by atomic force microscopy.

    Science.gov (United States)

    Valero, C; Navarro, B; Navajas, D; García-Aznar, J M

    2016-09-01

    The characterization of the mechanical properties of soft materials has been traditionally performed through uniaxial tensile tests. Nevertheless, this method cannot be applied to certain extremely soft materials, such as biological tissues or cells that cannot be properly subjected to these tests. Alternative non-destructive tests have been designed in recent years to determine the mechanical properties of soft biological tissues. One of these techniques is based on the use of atomic force microscopy (AFM) to perform nanoindentation tests. In this work, we investigated the mechanical response of soft biological materials to nanoindentation with spherical indenters using finite element simulations. We studied the responses of three different material constitutive laws (elastic, isotropic hyperelastic and anisotropic hyperelastic) under the same process and analyzed the differences thereof. Whereas linear elastic and isotropic hyperelastic materials can be studied using an axisymmetric simplification, anisotropic hyperelastic materials require three-dimensional analyses. Moreover, we established the limiting sample size required to determine the mechanical properties of soft materials while avoiding boundary effects. Finally, we compared the results obtained by simulation with an estimate obtained from Hertz theory. Hertz theory does not distinguish between the different material constitutive laws, and thus, we proposed corrections to improve the quantitative measurement of specific material properties by nanoindentation experiments.

  14. Effect of aging on the morphology of bitumen by atomic force microscopy.

    Science.gov (United States)

    Zhang, H L; Yu, J Y; Feng, Z G; Xue, L H; Wu, S P

    2012-04-01

    Effect of aging on the morphology of bitumen was investigated. Two bitumens were aged according to the thin film oven test (TFOT), pressure aging vessel (PAV) test and ultraviolet (UV) radiation, respectively. The morphology of the binders before and after aging was characterized by atomic force microscopy. The physical properties and chemical compositions of the binders were also measured. The results showed that aging affected the bitumen morphology significantly. Aging increased the overall surface stiffness of the bitumen and made the bitumen surface more solid-like. The extent of these changes was dependent on aging conditions. TFOT decreased the contrast between the dispersed domains and the matrix, which contributed to the single-phase trend of the binders. The effect of PAV aging on morphology of the binders was dependent on the base bitumen. In one case, it further accelerated the single-phase trend of bitumen in comparison with that after TFOT. In the other case, it caused the phase separation of bitumen. In both cases, PAV aging increased the surface roughness of the binders obviously. As a result of UV aging, the contrast between the matrix phase and dispersed phase was increased due to the difference in sensitivity to UV radiation of the bitumen molecules, which caused or further promoted the phase separation in the binders. Regardless of the aging procedure carried out, a strong correlation was observed between the changes in morphology and physical properties as well as chemical compositions of the binders before and after aging.

  15. Atomic force microscopy study of the antibacterial effects of chitosans on Escherichia coli and Staphylococcus aureus

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, Peter [REQUIMTE, Departamento de Quimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto (Portugal)], E-mail: peter.eaton@fc.up.pt; Fernandes, Joao C. [Departamento de Quimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto (Portugal); Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, Rua Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal); Pereira, Eulalia [REQUIMTE, Departamento de Quimica, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto (Portugal); Pintado, Manuela E.; Xavier Malcata, F. [Escola Superior de Biotecnologia, Universidade Catolica Portuguesa, Rua Dr. Antonio Bernardino de Almeida, 4200-072 Porto (Portugal)

    2008-09-15

    Chitosan has been reported to be a non-toxic, biodegradable antibacterial agent. The aim of this work was to elucidate the relationship between the molecular weight of chitosan and its antimicrobial activity upon two model microorganisms, one Gram-positive (Staphylococcus aureus) and one Gram-negative (Escherichia coli). Atomic force microscopy (AFM) imaging was used to obtain high-resolution images of the effect of chitosans on the bacterial morphology. The AFM measurements were correlated with viable cell numbers, which show that the two species reacted differently to the high- and low-molecular-weight chitosan derivatives. The images obtained revealed not only the antibacterial effects, but also the response strategies used by the bacteria; cell wall collapse and morphological changes reflected cell death, whereas clustering of bacteria appeared to be associated with cell survival. In addition, nanoindentation experiments with the AFM revealed mechanical changes in the bacterial cell wall induced by the treatment. The nanoindentation results suggested that despite little modification observed in the Gram-positive bacteria in morphological studies, cell wall damage had indeed occurred, since cell wall stiffness was reduced after chitooligosaccharide treatment.

  16. Quantitative nanohistological investigation of scleroderma: an atomic force microscopy-based approach to disease characterization

    Science.gov (United States)

    Strange, Adam P; Aguayo, Sebastian; Ahmed, Tarek; Mordan, Nicola; Stratton, Richard; Porter, Stephen R; Parekh, Susan; Bozec, Laurent

    2017-01-01

    Scleroderma (or systemic sclerosis, SSc) is a disease caused by excess crosslinking of collagen. The skin stiffens and becomes painful, while internally, organ function can be compromised by the less elastic collagen. Diagnosis of SSc is often only possible in advanced cases by which treatment time is limited. A more detailed analysis of SSc may provide better future treatment options and information of disease progression. Recently, the histological stain picrosirius red showing collagen register has been combined with atomic force microscopy (AFM) to study SSc. Skin from healthy individuals and SSc patients was biopsied, stained and studied using AFM. By investigating the crosslinking of collagen at a smaller hierarchical stage, the effects of SSc were more pronounced. Changes in morphology and Young’s elastic modulus were observed and quantified; giving rise to a novel technique, we have termed “quantitative nanohistology”. An increase in nanoscale stiffness in the collagen for SSc compared with healthy individuals was seen by a significant increase in the Young’s modulus profile for the collagen. These markers of stiffer collagen in SSc are similar to the symptoms experienced by patients, giving additional hope that in the future, nanohistology using AFM can be readily applied as a clinical tool, providing detailed information of the state of collagen. PMID:28138238

  17. Atomic force microscopy study, kinetic roughening and multifractal analysis of electrodeposited silver films

    Science.gov (United States)

    Nasehnejad, M.; Gholipour Shahraki, M.; Nabiyouni, G.

    2016-12-01

    We used atomic force microscopy (AFM) to study surface morphology and kinetic roughening of Ag films. X-ray diffraction (XRD) technique is used to verify the films crystalline structure. The influence of film thickness on the kinetic roughening was investigated using AFM data and roughness calculation. It is revealed that the surface roughness increases with increasing the film thickness. The data also consist with a complex behavior which is called as anomalous scaling. Scaling laws analysis for Ag films presents two distinct dynamics including large local and scale roughness and indicates a power law dependency on the thickness of film. AFM images have been characterized by the multifractal analysis. This analysis shows that the self-similar and multifractal characteristics as well as anomalous scaling exist in the Ag film morphologies. Description of the quantitative growth and surface morphology was done by the multifractal spectra, f (α) - α . It is found that the multifractal spectrum shape is left hook-like (that is difference of height interval of the multifractal spectrum, Δf = f (αmin) - f (αmax) > 0). The results indicate that the surfaces having greater roughness give rise the wider multifractal spectrum width (Δα) and the greater Δf, thus, the nonuniformity of the height probabilities becomes larger. It indicates that the multifractality of the films becomes more pronounced at the higher thickness.

  18. Deposition and Characterization of Molybdenum Thin Film Using Direct Current Magnetron and Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Muhtade Mustafa Aqil

    2017-01-01

    Full Text Available In this paper, pure molybdenum (Mo thin film has been deposited on blank Si substrate by DC magnetron sputtering technique. The deposition condition for all samples has not been changed except for the deposition time in order to study the influence of time on the thickness and surface morphology of molybdenum thin film. The surface profiler has been used to measure the surface thickness. Atomic force microscopy technique was employed to investigate the roughness and grain structure of Mo thin film. The thickness and grain of molybdenum thin film layer has been found to increase with respect to time, while the surface roughness decreases. The average roughness, root mean square roughness, surface skewness, and surface kurtosis parameters are used to analyze the surface morphology of Mo thin film. Smooth surface has been observed. From grain analysis, a uniform grain distribution along the surface has been found. The obtained results allowed us to decide the optimal time to deposit molybdenum thin film layer of 20–100 nm thickness and subsequently patterned as electrodes (source/drain in carbon nanotube-channel transistor.

  19. Prior Surface Integrity Assessment of Coated and Uncoated Carbide Inserts Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Abdulla Almazrouee

    2011-04-01

    Full Text Available Coated carbide inserts are considered vital components in machining processes and advanced functional surface integrity of inserts and their coating are decisive factors for tool life. Atomic Force Microscopy (AFM implementation has gained acceptance over a wide spectrum of research and science applications. When used in a proper systematic manner, the AFM features can be a valuable tool for assessment of tool surface integrity. The aim of this paper is to assess the integrity of coated and uncoated carbide inserts using AFM analytical parameters. Surface morphology of as-received coated and uncoated carbide inserts is examined, analyzed, and characterized through the determination of the appropriate scanning setting, the suitable data type imaging techniques and the most representative data analysis parameters using the MultiMode AFM microscope in contact mode. The results indicate that it is preferable to start with a wider scan size in order to get more accurate interpretation of surface topography. Results are found credible to support the idea that AFM can be used efficiently in detecting flaws and defects of coated and uncoated carbide inserts using specific features such as “Roughness” and “Section” parameters. A recommended strategy is provided for surface examination procedures of cutting inserts using various AFM controlling parameters.

  20. Direct measurement of attachment of {sup 220}Rn progeny on aerosols by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Leung, J.K.C. E-mail: jkcleung@hku.hk; Tso, M.Y.W.; Lam, J.H.C.; Zhau, Q.F

    2003-08-11

    Atomic force microscopy (AFM) is becoming a powerful tool for the study of nuclear tracks in materials such as CR-39. Coupled with its capability of observing near nm aerosol particles, we have utilized the AFM to observe the radon progeny-loaded aerosol particles deposited on surfaces of CR-39 and to observe the corresponding etch pits produced by the {alpha}-particles emitted from the radon progenies. A special platform was built so that after the aerosol particles on the CR-39 have been scanned and recorded, the CR-39 can be etched and then scanned for the etch pits at the same location. Both {sup 222}Rn and {sup 220}Rn progenies were used in the study. The progenies were generated by the appropriate radon sources and mixed with aerosol particles generated by aerosol generators. The aerosol size distributions were analyzed by a scanning mobility particle sizer. Some of the limitations and difficulties of the technique will be described. The results enable us to examine the attachment process including multiple attachments of radon progenies on aerosols.

  1. Dental enamel roughness with different acid etching times: Atomic force microscopy study

    Directory of Open Access Journals (Sweden)

    Bruno Bochnia Cerci

    2012-01-01

    Full Text Available Objective: An important characteristic of human dental enamel not yet studied in detail is its surface roughness in mesoscopic scale. This study evaluated quantitatively and qualitatively the surface topography of acid etched enamel with different etching times. Materials and Methods: Ninety-six human maxillary bicuspids were randomly distributed into three groups (n=32: T0 (control, pumiced; T15, 35% phosphoric acid etched enamel for 15 s; T30, 35% phosphoric acid etched enamel for 30 s. Roughness measurements Ra, Rz and root mean square (RMS and 3D images of enamel′s topography were obtained with atomic force microscopy (AFM, which is a powerful technique to obtain direct measurements on microscale features. Results and Conclusions: Roughness variables Ra, Rz and RMS presented statistically significant differences to all groups (P<0.000, with values increasing with etching time. This increase was greater from T0 to T15 than from T15 to T30. Enamel surface alterations T15 to T30 occur mainly due to increase in height and deepening of prisms central region.

  2. Morphology and current-voltage characteristics of nanostructured pentacene thin films probed by atomic force microscopy.

    Science.gov (United States)

    Zorba, S; Le, Q T; Watkins, N J; Yan, L; Gao, Y

    2001-09-01

    Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene.

  3. Calculation of the effect of tip geometry on noncontact atomic force microscopy using a qPlus sensor

    Directory of Open Access Journals (Sweden)

    Julian Stirling

    2013-01-01

    Full Text Available In qPlus atomic force microscopy the tip length can in principle approach the length of the cantilever. We present a detailed mathematical model of the effects this has on the dynamic properties of the qPlus sensor. The resulting, experimentally confirmed motion of the tip apex is shown to have a large lateral component, raising interesting questions for both calibration and force-spectroscopy measurements.

  4. Topological Structures and Membrane Nanostructures of Erythrocytes after Splenectomy in Hereditary Spherocytosis Patients via Atomic Force Microscopy.

    Science.gov (United States)

    Li, Ying; Lu, Liyuan; Li, Juan

    2016-09-01

    Hereditary spherocytosis is an inherited red blood cell membrane disorder resulting from mutations of genes encoding erythrocyte membrane and cytoskeletal proteins. Few equipments can observe the structural characteristics of hereditary spherocytosis directly expect for atomic force microscopy In our study, we proved atomic force microscopy is a powerful and sensitive instrument to describe the characteristics of hereditary spherocytosis. Erythrocytes from hereditary spherocytosis patients were small spheroidal, lacking a well-organized lattice on the cell membrane, with smaller cell surface particles and had reduced valley to peak distance and average cell membrane roughness vs. those from healthy individuals. These observations indicated defects in the certain cell membrane structural proteins such as α- and β-spectrin, ankyrin, etc. Until now, splenectomy is still the most effective treatment for symptoms relief for hereditary spherocytosis. In this study, we further solved the mysteries of membrane nanostructure changes of erythrocytes before and after splenectomy in hereditary spherocytosis by atomic force microscopy. After splenectomy, the cells were larger, but still spheroidal-shaped. The membrane ultrastructure was disorganized and characterized by a reduced surface particle size and lower than normal Ra values. These observations indicated that although splenectomy can effectively relieve the symptoms of hereditary spherocytosis, it has little effect on correction of cytoskeletal membrane defects of hereditary spherocytosis. We concluded that atomic force microscopy is a powerful tool to investigate the pathophysiological mechanisms of hereditary spherocytosis and to monitor treatment efficacy in clinical practices. To the best of our knowledge, this is the first report to study hereditary spherocytosis with atomic force microscopy and offers important mechanistic insight into the underlying role of splenectomy.

  5. Atomic Force Microscopy Reveals Important Differences in Axonal Resistance to Injury

    Science.gov (United States)

    Magdesian, Margaret H.; Sanchez, Fernando S.; Lopez, Monserratt; Thostrup, Peter; Durisic, Nela; Belkaid, Wiam; Liazoghli, Dalinda; Grütter, Peter; Colman, David R.

    2012-01-01

    Axonal degeneration after traumatic brain injury and nerve compression is considered a common underlying cause of temporary as well as permanent disability. Because a proper functioning of neural network requires phase coherence of all components, even subtle changes in circuitry may lead to network failure. However, it is still not possible to determine which axons will recover or degenerate after injury. Several groups have studied the pressure threshold for axonal injury within a nerve, but difficulty accessing the injured region; insufficient imaging methods and the extremely small dimensions involved have prevented the evaluation of the response of individual axons to injury. We combined microfluidics with atomic force microscopy and in vivo imaging to estimate the threshold force required to 1), uncouple axonal transport without impairing axonal survival, and 2), compromise axonal survival in both individual and bundled axons. We found that rat hippocampal axons completely recover axonal transport with no detectable axonal loss when compressed with pressures up to 65 ± 30 Pa for 10 min, while dorsal root ganglia axons can resist to pressures up to 540 ± 220 Pa. We investigated the reasons for the differential susceptibility of hippocampal and DRG axons to mechanical injury and estimated the elasticity of live axons. We found that dorsal root ganglia axons have a 20% lower elastic modulus than hippocampal axons. Our results emphasize the importance of the integrity of the axonal cytoskeleton in deciding the axonal fate after damage and open up new avenues to improve injury diagnosis and to identify ways to protect axons. PMID:22947856

  6. Mapping molecular adhesion sites inside SMIL coated capillaries using atomic force microscopy recognition imaging

    Energy Technology Data Exchange (ETDEWEB)

    Leitner, Michael [Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz (Austria); Stock, Lorenz G. [Division of Chemistry and Bioanalytics, Department of Molecular Biology, University Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg (Austria); Christian Doppler Laboratory for Innovative Tools for the Characterization of Biosimilars, University Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg (Austria); Traxler, Lukas [Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz (Austria); Leclercq, Laurent [Institut des Biomolécules Max Mousseron (IBMM, UMR 5247, CNRS, Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier), Place Eugène Bataillon, CC 1706, 34095 Montpellier (France); Bonazza, Klaus; Friedbacher, Gernot [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164, 1060 Vienna (Austria); Cottet, Hervé [Institut des Biomolécules Max Mousseron (IBMM, UMR 5247, CNRS, Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier), Place Eugène Bataillon, CC 1706, 34095 Montpellier (France); Stutz, Hanno [Division of Chemistry and Bioanalytics, Department of Molecular Biology, University Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg (Austria); Christian Doppler Laboratory for Innovative Tools for the Characterization of Biosimilars, University Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg (Austria); Ebner, Andreas, E-mail: andreas.ebner@jku.at [Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz (Austria)

    2016-08-03

    Capillary zone electrophoresis (CZE) is a powerful analytical technique for fast and efficient separation of different analytes ranging from small inorganic ions to large proteins. However electrophoretic resolution significantly depends on the coating of the inner capillary surface. High technical efforts like Successive Multiple Ionic Polymer Layer (SMIL) generation have been taken to develop stable coatings with switchable surface charges fulfilling the requirements needed for optimal separation. Although the performance can be easily proven in normalized test runs, characterization of the coating itself remains challenging. Atomic force microscopy (AFM) allows for topographical investigation of biological and analytical relevant surfaces with nanometer resolution and yields information about the surface roughness and homogeneity. Upgrading the scanning tip to a molecular biosensor by adhesive molecules (like partly inverted charged molecules) allows for performing topography and recognition imaging (TREC). As a result, simultaneously acquired sample topography and adhesion maps can be recorded. We optimized this technique for electrophoresis capillaries and investigated the charge distribution of differently composed and treated SMIL coatings. By using the positively charged protein avidin as a single molecule sensor, we compared these SMIL coatings with respect to negative charges, resulting in adhesion maps with nanometer resolution. The capability of TREC as a functional investigation technique at the nanoscale was successfully demonstrated. - Highlights: • SMIL coating allows generation of homogeneous ultra-flat surfaces. • Molecular electrostatic adhesion forces can be determined in the inner wall of CZE capillary with picoNewton accuracy. • Topographical images and simultaneously acquired adhesion maps yield morphological and chemical information at the nanoscale.

  7. Investigation of adhesion and mechanical properties of human glioma cells by single cell force spectroscopy and atomic force microscopy.

    Science.gov (United States)

    Andolfi, Laura; Bourkoula, Eugenia; Migliorini, Elisa; Palma, Anita; Pucer, Anja; Skrap, Miran; Scoles, Giacinto; Beltrami, Antonio Paolo; Cesselli, Daniela; Lazzarino, Marco

    2014-01-01

    Active cell migration and invasion is a peculiar feature of glioma that makes this tumor able to rapidly infiltrate into the surrounding brain tissue. In our recent work, we identified a novel class of glioma-associated-stem cells (defined as GASC for high-grade glioma--HG--and Gasc for low-grade glioma--LG) that, although not tumorigenic, act supporting the biological aggressiveness of glioma-initiating stem cells (defined as GSC for HG and Gsc for LG) favoring also their motility. Migrating cancer cells undergo considerable molecular and cellular changes by remodeling their cytoskeleton and cell interactions with surrounding environment. To get a better understanding about the role of the glioma-associated-stem cells in tumor progression, cell deformability and interactions between glioma-initiating stem cells and glioma-associated-stem cells were investigated. Adhesion of HG/LG-cancer cells on HG/LG-glioma-associated stem cells was studied by time-lapse microscopy, while cell deformability and cell-cell adhesion strengths were quantified by indentation measurements by atomic force microscopy and single cell force spectroscopy. Our results demonstrate that for both HG and LG glioma, cancer-initiating-stem cells are softer than glioma-associated-stem cells, in agreement with their neoplastic features. The adhesion strength of GSC on GASC appears to be significantly lower than that observed for Gsc on Gasc. Whereas, GSC spread and firmly adhere on Gasc with an adhesion strength increased as compared to that obtained on GASC. These findings highlight that the grade of glioma-associated-stem cells plays an important role in modulating cancer cell adhesion, which could affect glioma cell migration, invasion and thus cancer aggressiveness. Moreover this work provides evidence about the importance of investigating cell adhesion and elasticity for new developments in disease diagnostics and therapeutics.

  8. Investigation of adhesion and mechanical properties of human glioma cells by single cell force spectroscopy and atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Laura Andolfi

    Full Text Available Active cell migration and invasion is a peculiar feature of glioma that makes this tumor able to rapidly infiltrate into the surrounding brain tissue. In our recent work, we identified a novel class of glioma-associated-stem cells (defined as GASC for high-grade glioma--HG--and Gasc for low-grade glioma--LG that, although not tumorigenic, act supporting the biological aggressiveness of glioma-initiating stem cells (defined as GSC for HG and Gsc for LG favoring also their motility. Migrating cancer cells undergo considerable molecular and cellular changes by remodeling their cytoskeleton and cell interactions with surrounding environment. To get a better understanding about the role of the glioma-associated-stem cells in tumor progression, cell deformability and interactions between glioma-initiating stem cells and glioma-associated-stem cells were investigated. Adhesion of HG/LG-cancer cells on HG/LG-glioma-associated stem cells was studied by time-lapse microscopy, while cell deformability and cell-cell adhesion strengths were quantified by indentation measurements by atomic force microscopy and single cell force spectroscopy. Our results demonstrate that for both HG and LG glioma, cancer-initiating-stem cells are softer than glioma-associated-stem cells, in agreement with their neoplastic features. The adhesion strength of GSC on GASC appears to be significantly lower than that observed for Gsc on Gasc. Whereas, GSC spread and firmly adhere on Gasc with an adhesion strength increased as compared to that obtained on GASC. These findings highlight that the grade of glioma-associated-stem cells plays an important role in modulating cancer cell adhesion, which could affect glioma cell migration, invasion and thus cancer aggressiveness. Moreover this work provides evidence about the importance of investigating cell adhesion and elasticity for new developments in disease diagnostics and therapeutics.

  9. Single Molecule Science for Personalized Nanomedicine: Atomic Force Microscopy of Biopolymer-Protein Interactions

    Science.gov (United States)

    Hsueh, Carlin

    Nanotechnology has a unique and relatively untapped utility in the fields of medicine and dentistry at the level of single-biopolymer and -molecule diagnostics. In recent years atomic force microscopy (AFM) has garnered much interest due to its ability to obtain atomic-resolution of molecular structures and probe biophysical behaviors of biopolymers and proteins in a variety of biologically significant environments. The work presented in this thesis focuses on the nanoscale manipulation and observation of biopolymers to develop an innovative technology for personalized medicine while understanding complex biological systems. These studies described here primarily use AFM to observe biopolymer interactions with proteins and its surroundings with unprecedented resolution, providing a better understanding of these systems and interactions at the nanoscale. Transcriptional profiling, the measure of messenger RNA (mRNA) abundance in a single cell, is a powerful technique that detects "behavior" or "symptoms" at the tissue and cellular level. We have sought to develop an alternative approach, using our expertise in AFM and single molecule nanotechnology, to achieve a cost-effective high throughput method for sensitive detection and profiling of subtle changes in transcript abundance. The technique does not require amplification of the mRNA sample because the AFM provides three-dimensional views of molecules with unprecedented resolution, requires minimal sample preparation, and utilizes a simple tagging chemistry on cDNA molecules. AFM images showed collagen polymers in teeth and of Drebrin-A remodeling of filamentous actin structure and mechanics. AFM was used to image collagen on exposed dentine tubules and confirmed tubule occlusion with a desensitizing prophylaxis paste by Colgate-Palmolive. The AFM also superseded other microscopy tools in resolving F-actin helix remodeling and possible cooperative binding by a neuronal actin binding protein---Drebrin-A, an

  10. Cross Kelvin force microscopy and conductive atomic force microscopy studies of organic bulk heterojunction blends for local morphology and electrical behavior analysis

    Energy Technology Data Exchange (ETDEWEB)

    Villeneuve-Faure, C., E-mail: Christina.villeneuve@laplace.unvi-tlse.fr [LAPLACE, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse (France); UPS, INPT, Université de Toulouse, LCC 31077 Toulouse (France); Le Borgne, D. [LAPLACE, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse (France); UPS, INPT, Université de Toulouse, LCC 31077 Toulouse (France); LCC-CNRS, 205 route de Narbonne, F-31077 Toulouse Cedex 4 (France); Bedel-Pereira, E.; Séguy, I. [UPS, INPT, Université de Toulouse, LCC 31077 Toulouse (France); LAAS-CNRS, 7 Avenue du Colonel Roche, 31077 Toulouse Cedex 4 (France); Moineau Chane-Ching, K. I.; Hernandez-Maldonado, D. [UPS, INPT, Université de Toulouse, LCC 31077 Toulouse (France); LCC-CNRS, 205 route de Narbonne, F-31077 Toulouse Cedex 4 (France)

    2015-02-07

    Bulk Heterojunction (BHJ) organic photovoltaic devices performances depend on the relative organization and physical properties of the electron-donor and -acceptor materials. In this paper, BHJs of poly(3-hexyl-thiophene) (P3HT) associated with an electron acceptor material, 1-(3-methoxycarbonyl)-propyl-1-phenyl[6,6]C6 (PCBM) or [Ni(4dodpedt){sub 2}], are studied in terms of morphology, ordering, and electrical properties. First, comparison between the two BHJs performed by Atomic Force Microscopy (AFM) and Raman characterizations shows that P3HT structuration is improved by blending with [Ni(4dodpedt){sub 2}]. Then, the relationship between charges trapping, electrical properties, and film morphology is investigated using conductive AFM and Kelvin Force Microscopy. Measurements in dark condition and under solar cell simulator provide complementary information on electrical phenomena in these organic nanostructures. Finally, time dependent measurement highlights the influence of charges stacking on conduction. Specifically, we demonstrate that charge accumulation initiated by illumination remains valid after switching off the light, and induces the modification in current versus voltage characteristic of P3HT: PCBM blend. Finally, we observe a current increasing which can be attributed to the energy barrier decreasing due to charges trapping in PCBM.

  11. Visualization of recombinant DNA and protein complexes using atomic force microscopy.

    Science.gov (United States)

    Murphy, Patrick J M; Shannon, Morgan; Goertz, John

    2011-07-18

    Atomic force microscopy (AFM) allows for the visualizing of individual proteins, DNA molecules, protein-protein complexes, and DNA-protein complexes. On the end of the microscope's cantilever is a nano-scale probe, which traverses image areas ranging from nanometers to micrometers, measuring the elevation of macromolecules resting on the substrate surface at any given point. Electrostatic forces cause proteins, lipids, and nucleic acids to loosely attach to the substrate in random orientations and permit imaging. The generated data resemble a topographical map, where the macromolecules resolve as three-dimensional particles of discrete sizes (Figure 1). Tapping mode AFM involves the repeated oscillation of the cantilever, which permits imaging of relatively soft biomaterials such as DNA and proteins. One of the notable benefits of AFM over other nanoscale microscopy techniques is its relative adaptability to visualize individual proteins and macromolecular complexes in aqueous buffers, including near-physiologic buffered conditions, in real-time, and without staining or coating the sample to be imaged. The method presented here describes the imaging of DNA and an immunoadsorbed transcription factor (i.e. the glucocorticoid receptor, GR) in buffered solution (Figure 2). Immunoadsorbed proteins and protein complexes can be separated from the immunoadsorbing antibody-bead pellet by competition with the antibody epitope and then imaged (Figure 2A). This allows for biochemical manipulation of the biomolecules of interest prior to imaging. Once purified, DNA and proteins can be mixed and the resultant interacting complex can be imaged as well. Binding of DNA to mica requires a divalent cation, such as Ni(2+) or Mg(2+), which can be added to sample buffers yet maintain protein activity. Using a similar approach, AFM has been utilized to visualize individual enzymes, including RNA polymerase and a repair enzyme, bound to individual DNA strands. These experiments provide

  12. Current mapping of low-energy (120 eV) helium and hydrogen irradiated tungsten by conductive atomic force microscopy

    Science.gov (United States)

    Fan, Hongyu; Endo, Takashi; Bi, Zhenghua; Yan, Weibin; Ohnuki, Somei; Yang, Qi; Ni, Weiyuan; Liu, Dongping

    2017-04-01

    Both conductive atomic force microscopy (CAFM) and transmission electron microscopy have been used to characterize the defects or He bubbles in low-energy (120 eV) H and He irradiated tungsten (W). By a comparative study, we find that the current mapping from CAFM is very sensitive in the detection of nanometer-sized defects in low-energy H and He irradiated W. Our calculation confirms that the resistance change in H and He irradiated W is strongly affected by the distance between atomic force microscopy tip and defects/He bubbles. CAFM can accurately detect defects/He bubbles in the W surface layer, however, it is infeasible to measure them in the deep layer (>20 nm), especially due to the existence of defects in the surface layer.

  13. Exploring nanoscale electrical and electronic properties of organic and polymeric functional materials by atomic force microscopy based approaches.

    Science.gov (United States)

    Palermo, Vincenzo; Liscio, Andrea; Palma, Matteo; Surin, Mathieu; Lazzaroni, Roberto; Samorì, Paolo

    2007-08-28

    Beyond imaging, atomic force microscopy (AFM) based methodologies enable the quantitative investigation of a variety of physico-chemical properties of (multicomponent) materials with a spatial resolution of a few nanometers. This Feature Article is focused on two AFM modes, i.e. conducting and Kelvin probe force microscopies, which allow the study of electrical and electronic properties of organic thin films, respectively. These nanotools provide a wealth of information on (dynamic) characteristics of tailor-made functional architectures, opening pathways towards their technological application in electronics, catalysis and medicine.

  14. Sharing my fifteen years experiences in the research field of Atomic Force Microscopy (AFM)

    OpenAIRE

    Guha T

    2014-01-01

    Atomic Force Microscope (AFM) was developed by Binnig and his coworkers in the year 1986. He was awarded Nobel Prize in physics for this work in 1986 in sharing with Rohrer and Ruska. Rationale to develop AFM: Scanning Tunneling Microscope (STM), the precursor to AFM is efficient in imaging electrically conducting specimen at atomic resolution. The impetus for development of AFM came to Binnig’s mind because of relatively poor efficiency of STM to image electrically non-conducting bi...

  15. The architecture of neutrophil extracellular traps investigated by atomic force microscopy

    Science.gov (United States)

    Pires, Ricardo H.; Felix, Stephan B.; Delcea, Mihaela

    2016-07-01

    Neutrophils are immune cells that engage in a suicidal pathway leading to the release of partially decondensed chromatin, or neutrophil extracellular traps (NETs). NETs behave as a double edged sword; they can bind to pathogens thereby ensnaring them and limiting their spread during infection; however, they may bind to host circulating materials and trigger thrombotic events, and are associated with autoimmune disorders. Despite the fundamental role of NETs as part of an immune system response, there is currently a very poor understanding of how their nanoscale properties are reflected in their macroscopic impact. In this work, using a combination of fluorescence and atomic force microscopy, we show that NETs appear as a branching filament network that results in a substantially organized porous structure with openings with 0.03 +/- 0.04 μm2 on average and thus in the size range of small pathogens. Topological profiles typically up to 3 +/- 1 nm in height are compatible with a ``beads on a string'' model of nucleosome chromatin. Typical branch lengths of 153 +/- 103 nm appearing as rigid rods and height profiles of naked DNA in NETs of 1.2 +/- 0.5 nm are indicative of extensive DNA supercoiling throughout NETs. The presence of DNA duplexes could also be inferred from force spectroscopy and the occurrence of force plateaus that ranged from ~65 pN to 300 pN. Proteolytic digestion of NETs resulted in widespread disassembly of the network structure and considerable loss of mechanical properties. Our results suggest that the underlying structure of NETs is considerably organized and that part of its protein content plays an important role in maintaining its mesh architecture. We anticipate that NETs may work as microscopic mechanical sieves with elastic properties that stem from their DNA-protein composition, which is able to segregate particles also as a result of their size. Such a behavior may explain their participation in capturing pathogens and their association

  16. Three-dimensional atomic force microscopy mapping at the solid-liquid interface with fast and flexible data acquisition.

    Science.gov (United States)

    Söngen, Hagen; Nalbach, Martin; Adam, Holger; Kühnle, Angelika

    2016-06-01

    We present the implementation of a three-dimensional mapping routine for probing solid-liquid interfaces using frequency modulation atomic force microscopy. Our implementation enables fast and flexible data acquisition of up to 20 channels simultaneously. The acquired data can be directly synchronized with commercial atomic force microscope controllers, making our routine easily extendable for related techniques that require additional data channels, e.g., Kelvin probe force microscopy. Moreover, the closest approach of the tip to the sample is limited by a user-defined threshold, providing the possibility to prevent potential damage to the tip. The performance of our setup is demonstrated by visualizing the hydration structure above the calcite (10.4) surface in water.

  17. Comparison of photothermal and piezoacoustic excitation methods for frequency and phase modulation atomic force microscopy in liquid environments

    Directory of Open Access Journals (Sweden)

    A. Labuda

    2011-06-01

    Full Text Available In attempting to perform frequency modulation atomic force microscopy (FM-AFM in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM which lies in between phase modulation atomic force microscopy (PM-AFM and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard FM-AFM theory no longer applies. Although our recovery procedure applies to all cantilever excitation methods in principle, its practical implementation may be difficult, or even impossible, if the cantilever is driven piezoacoustically. Specifically, we contrast the piezoacoustic excitation method to the photothermal method in the context of force spectroscopy of hydration structures at the mica-water interface. The results clearly demonstrate that photothermal excitation is superior to piezoacoustic excitation, as it allows for accurate quantitative interpretation of the acquired data.

  18. Atomic force microscopy study of cellulose surface interaction controlled by cellulose binding domains

    OpenAIRE

    Nigmatullin, R.; Lovitt, R.; Wright, C; Linder, M.; Nakari-Setälä, T; Gama, F. M.

    2004-01-01

    Colloidal probe microscopy has been used to study the interaction between model cellulose surfaces and the role of cellulose binding domain (CBD), peptides specifically binding to cellulose, in interfacial interaction of cellulose surfaces modified with CBDs. The interaction between pure cellulose surfaces in aqueous electrolyte solution is dominated by double layer repulsive forces with the range and magnitude of the net force dependent on electrolyte concentration. AFM imaging reve...

  19. Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

    Directory of Open Access Journals (Sweden)

    M. Kalyan Phani

    2015-03-01

    Full Text Available The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V measured by using atomic force acoustic microscopy (AFAM is reported in the present study. The real and imaginary parts of the contact stiffness k* are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α′- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD and electron back-scatter diffraction (EBSD studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM.

  20. Chitosan nanoparticles as non-viral gene delivery vehicles based on atomic force microscopy study

    Institute of Scientific and Technical Information of China (English)

    Yujing Yuan; Jieyi Tan; Yifei Wang; Chuiwen Qian; Meiying Zhang

    2009-01-01

    Chitosan (CS), a biocompatible and biodegradable material, can act as a non-viral delivery vehicle with low toxicity. In this study, plasmid DNA (pDNA) and siRNA were encapsulated in CS nanoparticles (NPs) to prepare CS-DNA and CS-siRNA NPs using a complex coacervation process. The CS-DNA particle size was within the range of 180-370 nm with a surface charge ranging from 0 to 18 mV at pH 5.5. The stability of pDNA in CS-DNA was investigated by pDNA release study and DNase I protection assay. The release of pDNA from NPs was studied in pH 7.4 phosphatebuffered saline at 37℃ and the CS-DNA NPs could delay the DNA release. Results of DNase I protection assay showed that CS-DNA NPs could protect the encapsulated pDNA from nuclease degradation. In the transfection study, it was found that the transfection efficiency in vitro was dependent on the molecular weight, charge ratio, and DNA concentration of the CS-DNA NP as well as the type of cell transfected. Moreover, the morphology of HeLa cells transfected with CS-siRNA complexes was studied using atomic force microscopy. The results suggest that CS may be more capable than liposome in delivering siRNA to target cells. In summary,our analysis suggests that pDNA and siRNA can be encapsulated in CS NPs without being damaged.

  1. Fabrication and characterization of mesoscale protein patterns using atomic force microscopy (AFM)

    Science.gov (United States)

    Gao, Pei

    2011-07-01

    A versatile AFM local oxidation lithography was developed for fabricating clean protein patterns ranging from nanometer to sub-millimeter scale on octadecyltrichlorosilane (OTS) layer of Si (100) wafer. This protein patterning method can generate bio-active protein pattern with a clean background without the need of the anti-fouling the surface or repetitive rinsing. As a model system, lysozyme protein patterns were investigated through their binding reactions with antibodies and aptamers by AFM. Polyclonal anti-lysozyme antibodies and anti-lysozyme aptamer are found to preferentially bind to the lysozyme molecules on the edge of a protein pattern before their binding to the interior ones. It was also demonstrated that the topography of the immobilized protein pattern affects the antibody binding direction. We found that the anti-lysozyme antibodies binding to the edge lysozyme molecules on the half-buried pattern started from the top but the binding on the extruded pattern started from the side because of their different spatial accessibility. In addition, after incubating lysozyme pattern with anti-lysozyme aptamer in buffer solution for enough long time, some fractal-shaped aptamer fibers with 1-6nm high and up to tens of micrometers long were formed by the self-assembling of aptamer molecules on the surface. The aptamer fibers anchor specifically on the edge of protein patterns, which originates from the biospecific recognition between the aptamer and its target protein. Once these edge-bound fibers have formed, they can serve as scaffolds for further assembly processes. We used these aptamer fibers as templates to fabricate palladium and streptavidin nanowires, which anchored on the pattern edges and never cross over or collapse over each other. The aptamer fiber scaffold potentially can lead to an effective means to fabricate and interface nanowires to existing surface patterns. KEYWORDS: Atomic Force Microscopy (AFM), Protein Patterns, Lysozyme, Aptamer

  2. Kinetic Defects Induced by Melittin in Model Lipid Membranes: A Solution Atomic Force Microscopy Study.

    Science.gov (United States)

    Pan, Jianjun; Khadka, Nawal K

    2016-05-26

    Quantitative characterization of membrane defects (pores) is important for elucidating the molecular basis of many membrane-active peptides. We study kinetic defects induced by melittin in vesicular and planar lipid bilayers. Fluorescence spectroscopy measurements indicate that melittin induces time-dependent calcein leakage. Solution atomic force microscopy (AFM) is used to visualize melittin-induced membrane defects. After initial equilibration, the most probable defect radius is ∼3.8 nm in 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) bilayers. Unexpectedly, defects become larger with longer incubation, accompanied by substantial shape transformation. The initial defect radius is ∼4.7 nm in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers. Addition of 30 mol % cholesterol to DOPC bilayers suppresses defect kinetics, although the inhibitory impact is negated by longer incubation. Overall, the kinetic rate of defect development follows DLPC > DOPC > DOPC/cholesterol. Kinetic defects are also observed when anionic lipids are present. Based on the observation that defects can occupy as large as 40% of the bilayer surface, we propose a kinetic defect growth model. We also study the effect of melittin on the phase behavior of DOPC/egg-sphingomyelin/cholesterol bilayers. We find that melittin initially suppresses or eliminates liquid-ordered (Lo) domains; Lo domains gradually emerge and become the dominant species with longer incubation; and defects in phase-coexisting bilayers have a most probable radius of ∼5 nm and are exclusively localized in the liquid-disordered (Ld) phase. Our experimental data highlight that melittin-induced membrane defects are not static; conversely, spontaneous defect growth is intrinsically associated with membrane permeabilization exerted by melittin.

  3. Use of in situ atomic force microscopy to image copper electrodeposits on platinum

    Energy Technology Data Exchange (ETDEWEB)

    Rynders, R.M.; Alkire, R.C. (Univ. of Illinois, Urbana, IL (United States). Dept. of Chemical Engineering and Materials Research Lab.)

    1994-05-01

    In situ atomic force microscopy (AFM) was used to observe growth morphology during copper electrodeposition on Pt(100) and Pt(111) surfaces from 0.25 M CuSO[sub 4]/0.5M H[sub 2]SO[sub 4] containing 0, 10, and 100 [mu]M benzotriazole (BTA). The Pt(100) crystal was misoriented [approximately]2 [degree] to give terraces that were approximately 1 [mu]m in length and 25 to 50 [angstrom] high. Deposit morphology was monitored primarily during growth at current densities between 1 and 15 mA/cm[sup 2] under stagnant conditions. In the absence of BTA, copper selectively deposited on the larger step sites rather than on the smaller steps or terrace regions. From solutions containing 10[mu]M BTA, copper deposited in clumps along the steps. From solutions containing 100 [mu]m BTA, deposition occurred without regard to substrate features. On Pt(111), three-dimensional nucleations of copper was monitored at the nanoscale level during cathodic deposition from 0.25M CuSO[sub 4]/0.5M H[sub 2]SO[sub 4]. At over potentials <70 mV, no nuclei were observed. At 120 and 170 mV overpotential, individual 3-D clusters were observed, and additional clusters nucleated over time. At higher over potentials ([>=]200 mV), uniform nucleation and overlap were observed. The current transients and AFM images recorded during the deposition experiments were compared with theory for 3-D, solution-diffusion-controlled, multiple nucleation with overlap. At high over potentials, the current transients were consistent with theory, and AFM images indicated that nucleation was three-dimensional with overlap. At low over potentials, the current transients were not consistent with theory, and AFM images confirmed that nuclei did not overlap.

  4. Improved method for Mica functionalization used in single molecule imaging of DNA with atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Hana Zapletalová

    2016-07-01

    Full Text Available The modified procedure of 1-(3-aminopropylsilatrane (APS compound synthesis based on a new derivative (3‑aminopropyltrimethoxysilane for the purpose of DNA immobilization for AFM single imaging is described. New reaction pathway based on kinetically driven reaction approach is described. Necessity of two‑step purification process is proved; ability of purified APS to provide four times smoother surfaces in comparison with a crude product is demonstrated. Various analytical methods such mass spectroscopy and 1H NMR were used to show structure and enhanced purity of the APS product. APS mediates fixation of DNA molecules to mica substrates to be used for DNA imaging under Atomic Force Microscope. The use of an APS compound for simple and rapid silanization of mica surface is demonstrated. The advantages of APS‑based method are based mainly on low roughness of modified mica and homogeneous surface coverage by short sequence dsDNA (246 bp. The product obtained by the condensation reaction was purified in a two step process whose effectiveness was demonstrated not only by reduction of the silanized surface roughness, but also by mass spectroscopy (MS‑ESi, MALDI‑TOF method and proton magnetic resonance spectroscopy. Experiments demonstrate that 1‑(3‑aminopropylsilatrane can be used to fix dsDNA molecules to a mica surface to be visualized by either the tapping mode or the force‑volume mode of AFM microscopy, as demonstrated by experiments. Moreover, necessity of advanced purification protocol is demonstrated by AFM based roughness measurements – pure vs crude APS product. The kinetics of APS‑layer aging, caused by silicon oxide growth on silanized layers, was studied by water contact angle measurements and is discussed.

  5. Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Jannis Lübbe

    2013-01-01

    Full Text Available The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM consists of cantilever thermal noise, tip–surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density dz at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density dΔf at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip–surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured dz, we predict dΔf for specific filter settings, a given level of detection-system noise spectral density dzds and the cantilever-thermal-noise spectral density dzth. We find an excellent agreement between the calculated and measured values for dΔf. Furthermore, we demonstrate that thermal noise in dΔf, defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth.

  6. The electronic behavior of a photosynthetic reaction center monitored by conductive atomic force microscopy.

    Science.gov (United States)

    Mikayama, Takeshi; Iida, Kouji; Suemori, Yoshiharu; Dewa, Takehisa; Miyashita, Tokuji; Nango, Mamoru; Gardiner, Alastair T; Cogdell, Richard J

    2009-01-01

    The conductivity of a photosynthetic reaction center (RC) from Rhodobacter sphaeroides was measured with conductive atomic force microscopy (CAFM) on SAM-modified Au(111) substrates. 2-mercaptoethanol (2ME), 2-mercaptoacetic acid (MAC), 2-mercaptopyridine (2MP) and 4-mercaptopyridine (4MP) were prepared as SAM materials to investigate the stability and morphology of RCs on the substrate by using near-IR absorption spectroscopy and AFM, respectively. The clear presence of the three well known RC near-IR absorption peaks indicates that the RCs were native on the SAM-modified Au(111). Dense grains with various diameters of 5-20 nm, which corresponded to mixtures of single RCs up to aggregates of 10, were observed in topographs of RCs adsorbed on all the different SAM-modified Au(111) substrates. The size of currents obtained from the RC using a bare conductive cantilever were produced in the following order for SAM molecules: 2MP > 2ME > 4MP > MAC. A clear rectification of this current was observed for the modification of the Au(111) substrate with the pi-conjugated thiol, 2MP, indicating that 2MP was effective in both promoting the specific orientation of the RCs on the electrode and electron injection into the RC. Cyclic voltammetry measurements indicate that the 2MP is better mediator for the electron transfer between a quinone and substrate. The current with 2MP-modified cantilever was twice as high as that obtained with the Au-coated one alone, indicating that 2MP has an important role in lowering the electron injection barrier between special pair side of RC and gold electrode.

  7. Recent investigations of silk fibers utilizing x-ray scattering and atomic force microscopy

    Science.gov (United States)

    Miller, Lance D.

    1998-12-01

    Silks from the mulberry silkworm, Bombyx mori, and the golden-orb spider, Nephila clavipes, are materials that possess respectable properties. Even pitted against the high performance fibers of Kevlar, polyethylene, and carbon, the advantages of some of nature's fibers are clear. The tensile strength of the golden-orb spider dragline is of the same order of magnitude as many synthetic fibers, yet the dragline's compressive strength as a percentage of its tensile strength is greater. The spider's ampullate glands, responsible for the manufacture of the dragline, also excel. The spider spins its fiber from a liquid crystalline solution that is water based versus the solutions at high temperatures containing volatile solvents that are required for current synthetic fibers. Understanding the morphology of silks will provide the basis for improved manufacturing and better performing synthetic fibers. The studies presented here have centered on the use of small-angle x-ray scattering, SAXS, to describe the large-scale morphology of silk fibers. We have determined minimum scattering dimensions on the order of 150-300 nm. A detailed analysis of the Porod scattering region has revealed correlation lengths of the same magnitude. Both of these dimensions are similar to with direct atomic force microscopy, AFM, measurements of nanofibers found in samples of abraded or peeled silk. The incorporation of discrete Fourier transform theory and AFM topographic information has yielded results in general agreement with measured SAXS patterns. This incorporation allows the materials scientist a way of visualizing the relationship between a material and its resulting scattering function. We have also found that x-ray scattering gives insight to new periodic distances of the morphology of golden-orb dragline. All of these studies yield a more complete view of the silk morphology and give a new method of model building from scattering experiments.

  8. Hydration effects on gypsum dissolution revealed by in situ nanoscale atomic force microscopy observations

    Science.gov (United States)

    Burgos-Cara, A.; Putnis, C. V.; Rodriguez-Navarro, C.; Ruiz-Agudo, E.

    2016-04-01

    Recent work has suggested that the rates of mineral dissolution in aqueous solutions are dependent on the kinetics of dehydration of the ions building the crystal. Dehydration kinetics will be ultimately determined by the competition between ion-water and water-water interactions, which can be significantly modified by the presence of background ions in solution. At low ionic strength, the effect of electrolytes on ion-water (electrostatic) interactions will dominate (Kowacz et al., 2007). By performing macroscopic and in situ, microscopic (atomic force microscopy) dissolution experiments, the effect of background electrolytes on the dissolution kinetics of gypsum (CaSO4·2H2O) {0 1 0} cleavage surfaces is tested at constant, low ionic strength (IS = 0.05) and undersaturation (saturation index, SI = -0.045). Dissolution rates are systematically lower in the presence of 1:1 background electrolytes than in an electrolyte-free solution, regardless of the nature of the electrolyte tested. We hypothesize that stabilization of the hydration shell of calcium by the presence of background ions can explain this result, based on the observed correlations in dissolution rates with the ionic surface tension increment of the background ion in solution. Stabilization of the cation hydration shell should favor dissolution. However, in the case of strongly hydrated ions such as Ca2+, this has a direct entropic effect that reduces the overall ΔG of the system, so that dissolution is energetically less favorable. Overall, these results provide new evidence that supports cation dehydration being the rate-controlling step for gypsum dissolution, as proposed for other minerals such as barite, dolomite and calcite.

  9. Modes of Escherichia coli Dps Interaction with DNA as Revealed by Atomic Force Microscopy.

    Directory of Open Access Journals (Sweden)

    Vladislav V Melekhov

    Full Text Available Multifunctional protein Dps plays an important role in iron assimilation and a crucial role in bacterial genome packaging. Its monomers form dodecameric spherical particles accumulating ~400 molecules of oxidized iron ions within the protein cavity and applying a flexible N-terminal ends of each subunit for interaction with DNA. Deposition of iron is a well-studied process by which cells remove toxic Fe2+ ions from the genetic material and store them in an easily accessible form. However, the mode of interaction with linear DNA remained mysterious and binary complexes with Dps have not been characterized so far. It is widely believed that Dps binds DNA without any sequence or structural preferences but several lines of evidence have demonstrated its ability to differentiate gene expression, which assumes certain specificity. Here we show that Dps has a different affinity for the two DNA fragments taken from the dps gene regulatory region. We found by atomic force microscopy that Dps predominantly occupies thermodynamically unstable ends of linear double-stranded DNA fragments and has high affinity to the central part of the branched DNA molecule self-assembled from three single-stranded oligonucleotides. It was proposed that Dps prefers binding to those regions in DNA that provide more contact pads for the triad of its DNA-binding bundle associated with one vertex of the protein globule. To our knowledge, this is the first study revealed the nucleoid protein with an affinity to branched DNA typical for genomic regions with direct and inverted repeats. As a ubiquitous feature of bacterial and eukaryotic genomes, such structural elements should be of particular care, but the protein system evolutionarily adapted for this function is not yet known, and we suggest Dps as a putative component of this system.

  10. Mismatch detection in DNA monolayers by atomic force microscopy and electrochemical impedance spectroscopy

    Directory of Open Access Journals (Sweden)

    Maryse D. Nkoua Ngavouka

    2016-02-01

    Full Text Available Background: DNA hybridization is at the basis of most current technologies for genotyping and sequencing, due to the unique properties of DNA base-pairing that guarantee a high grade of selectivity. Nonetheless the presence of single base mismatches or not perfectly matched sequences can affect the response of the devices and the major challenge is, nowadays, to distinguish a mismatch of a single base and, at the same time, unequivocally differentiate devices read-out of fully and partially matching sequences.Results: We present here two platforms based on different sensing strategies, to detect mismatched and/or perfectly matched complementary DNA strands hybridization into ssDNA oligonucleotide monolayers. The first platform exploits atomic force microscopy-based nanolithography to create ssDNA nano-arrays on gold surfaces. AFM topography measurements then monitor the variation of height of the nanostructures upon biorecognition and then follow annealing at different temperatures. This strategy allowed us to clearly detect the presence of mismatches. The second strategy exploits the change in capacitance at the interface between an ssDNA-functionalized gold electrode and the solution due to the hybridization process in a miniaturized electrochemical cell. Through electrochemical impedance spectroscopy measurements on extended ssDNA self-assembled monolayers we followed in real-time the variation of capacitance, being able to distinguish, through the difference in hybridization kinetics, not only the presence of single, double or triple mismatches in the complementary sequence, but also the position of the mismatched base pair with respect to the electrode surface.Conclusion: We demonstrate here two platforms based on different sensing strategies as sensitive and selective tools to discriminate mismatches. Our assays are ready for parallelization and can be used in the detection and quantification of single nucleotide mismatches in microRNAs or

  11. The study on the atomic force microscopy base nanoscale electrical discharge machining.

    Science.gov (United States)

    Huang, Jen-Ching; Chen, Chung-Ming

    2012-01-01

    This study proposes an innovative atomic force microscopy (AFM) based nanoscale electrical discharge machining (AFM-based nanoEDM) system which combines an AFM with a self-produced metallic probe and a high-voltage generator to create an atmospheric environment AFM-based nanoEDM system and a deionized water (DI water) environment AFM-based nanoEDM system. This study combines wire-cut processing and electrochemical tip sharpening techniques on a 40-µm thick stainless steel sheet to produce a high conductive AFM probes, the production can withstand high voltage and large current. The tip radius of these probes is approximately 40 nm. A probe test was executed on the AFM using probes to obtain nanoscales morphology of Si wafer surface. The silicon wafer was as a specimen to carry out AFM-base nanoEDM process in atmospheric and DI water environments by AFM-based nanoEDM system. After experiments, the results show that the atmospheric and DI water environment AFM-based nanoEDM systems operate smoothly. From experimental results, it can be found that the electric discharge depth of the silicon wafer at atmospheric environments is a mere 14.54 nm. In a DI water environment, the depth of electric discharge of the silicon wafer can reach 25.4 nm. This indicates that the EDM ability of DI water environment AFM-based nanoEDM system is higher than that of atmospheric environment AFM-based nanoEDM system. After multiple nanoEDM process, the tips become blunt. After applying electrochemical tip sharpening techniques, the tip radius can return to approximately 40 nm. Therefore, AFM probes produced in this study can be reused.

  12. Nanomechanical assessment of human and murine collagen fibrils via atomic force microscopy cantilever-based nanoindentation.

    Science.gov (United States)

    Andriotis, Orestis G; Manuyakorn, Wiparat; Zekonyte, Jurgita; Katsamenis, Orestis L; Fabri, Sebastien; Howarth, Peter H; Davies, Donna E; Thurner, Philipp J

    2014-11-01

    The nanomechanical assessment of collagen fibrils via atomic force microscopy (AFM) is of increasing interest within the biomedical research community. In contrast to conventional nanoindentation there exists no common standard for conducting experiments and analysis of data. Currently used analysis approaches vary between studies and validation of quantitative results is usually not performed, which makes comparison of data from different studies difficult. Also there are no recommendations with regards to the maximum indentation depth that should not be exceeded to avoid substrate effects. Here we present a methodology and analysis approach for AFM cantilever-based nanoindentation experiments that allows efficient use of captured data and relying on a reference sample for determination of tip shape. Further we show experimental evidence that maximum indentation depth on collagen fibrils should be lower than 10-15% of the height of the fibril to avoid substrate effects and we show comparisons between our and other approaches used in previous works. While our analysis approach yields similar values for indentation modulus compared to the Oliver-Pharr method we found that Hertzian analysis yielded significantly lower values. Applying our approach we successfully and efficiently indented collagen fibrils from human bronchi, which were about 30 nm in size, considerably smaller compared to collagen fibrils obtained from murine tail-tendon. In addition, derived mechanical parameters of collagen fibrils are in agreement with data previously published. To establish a quantitative validation we compared indentation results from conventional and AFM cantilever-based nanoindentation on polymeric samples with known mechanical properties. Importantly we can show that our approach yields similar results when compared to conventional nanoindentation on polymer samples. Introducing an approach that is reliable, efficient and taking into account the AFM tip shape, we anticipate

  13. Quantitative nanohistological investigation of scleroderma: an atomic force microscopy-based approach to disease characterization

    Directory of Open Access Journals (Sweden)

    Strange AP

    2017-01-01

    Full Text Available Adam P Strange,1 Sebastian Aguayo,1 Tarek Ahmed,1 Nicola Mordan,1 Richard Stratton,2 Stephen R Porter,3 Susan Parekh,4 Laurent Bozec1 1Department of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, 2Centre for Rheumatology and Connective Tissue Diseases, Royal Free Hospital, UCL Medical School, 3UCL Eastman Dental Institute, 4Department of Pediatrics, UCL Eastman Dental Institute, London, UK Abstract: Scleroderma (or systemic sclerosis, SSc is a disease caused by excess crosslinking of collagen. The skin stiffens and becomes painful, while internally, organ function can be compromised by the less elastic collagen. Diagnosis of SSc is often only possible in advanced cases by which treatment time is limited. A more detailed analysis of SSc may provide better future treatment options and information of disease progression. Recently, the histological stain picrosirius red showing collagen register has been combined with atomic force microscopy (AFM to study SSc. Skin from healthy individuals and SSc patients was biopsied, stained and studied using AFM. By investigating the crosslinking of collagen at a smaller hierarchical stage, the effects of SSc were more pronounced. Changes in morphology and Young’s elastic modulus were observed and quantified; giving rise to a novel technique, we have termed “quantitative nanohistology”. An increase in nanoscale stiffness in the collagen for SSc compared with healthy individuals was seen by a significant increase in the Young’s modulus profile for the collagen. These markers of stiffer collagen in SSc are similar to the symptoms experienced by patients, giving additional hope that in the future, nanohistology using AFM can be readily applied as a clinical tool, providing detailed information of the state of collagen. Keywords: rheumatology, adjunct diagnosis, picrosirius red, collagen, nanohistology

  14. Defects, detection and measurement on polished silicon wafer surface by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, W.P.; Seow, W.S. [S.E.H. (M) Sdn. Kuala Lumpur (Malaysia); Yow, H.K.; Tou, T.Y. [Multimedia Univ., Faculty of Engineering, Cyberjaya (Malaysia)

    2000-01-01

    Crystal originated ''particles'' (COPs) have been recognized as surface defects or micro-pits which originate from grown-in defects. The basic microstructure of the COP is an octahedral void with faces along the {l_brace}111{r_brace} orientation. In this paper, COPs were detected using an optical scattering technique and the change of their widths in an etching solution of NH{sub 4}OH:H{sub 2}O{sub 2}:H{sub 2}O (SC-1) was measured using atomic force microscopy (AFM). The rate of change in the width, r, of these COPs in the SC-1 solution was determined. r can be used to determine if a COP emanated from either the upper or lower portion of the void. For a single type COP originating from the lower portion of the void, r was measured to be 0.94 nm/min along the left angle 011 right angle direction. However, a single type COP from the upper portion has an r value of 2.5 nm/min. For this case, two factors are responsible for the higher rate; the etching of silicon horizontally along the left angle 011 right angle direction and the sloping {l_brace}111{r_brace} surface of the octahedral void during the removal of the silicon (100) plane. Further, a single type COP might also develop into a twin type COP after repeated SC-1 dipping if there is a second void located close to the first COP but lying just below the wafer surface. (orig.)

  15. Silicone hydrogel contact lens surface analysis by atomic force microscopy: shape parameters

    Science.gov (United States)

    Giraldez, M. J.; Garcia-Resua, C.; Lira, M.; Sánchez-Sellero, C.; Yebra-Pimentel, E.

    2011-05-01

    Purpose: Average roughness (Ra) is generally used to quantify roughness; however it makes no distinction between spikes and troughs. Shape parameters as kurtosis (Rku) and skewness (Rsk) serve to distinguish between two profiles with the same Ra. They have been reported in many biomedical fields, but they were no applied to contact lenses before. The aim of this study is to analyze surface properties of four silicone hydrogel contact lenses (CL) by Atomic Force Microscopy (AFM) evaluating Ra, Rku and Rsk. Methods: CL used in this study were disposable silicone hydrogel senofilcon A, comfilcon A, balafilcon A and lotrafilcon B. Unworn CL surfaces roughness and topography were measured by AFM (Veeco, multimode-nanoscope V) in tapping modeTM. Ra, Rku and Rsk for 25 and 196 μm2 areas were determined. Results: Surface topography and parameters showed different characteristics depending on the own nature of the contact lens (Ra/Rku/Rsk for 25 and 196 μm2 areas were: senofilcon A 3,33/3,74/0,74 and 3,76/18,16/1,75; comfilcon A: 1,56/31,09/2,93 and 2,76/45,82/3,60; balafilcon A: 2,01/33,62/-2,14 and 2,54/23,36/-1,96; lotrafilcon B: 26,97/4,11/-0,34 and 29,25/2,82/-0,23). In lotrafilcon B, with the highest Ra, Rku showed a lower degree of peakedness of its distribution. Negative Rsk value obtained for balafilcon A showed a clear predominance of valleys in this lens. Conclusions: Kku and Rsk are two statistical parameters useful to analyse CL surfaces, which complete information from Ra. Differences in values distribution and symmetry were observed between CL.

  16. Surface nanoscale imaging of collagen thin films by Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stylianou, Andreas, E-mail: styliand@mail.ntua.gr; Yova, Dido

    2013-07-01

    Collagen, the most abundant protein in mammals, due to its unique properties is widely used as biomaterial, scaffold and culture substrate for cell and tissue regeneration studies. Since the majority of biological reactions occur on surfaces and structures at the nanoscale level it is of great importance to image the nanostructural surface of collagen based materials. The aim of this paper was to characterize, with Atomic Force Microscopy (AFM), collagen thin films formed on different substrates (glass, mica, polystyrene latex particle surfaces) and correlate their morphology with the used substrates, formation methodologies (spin coating, hydrodynamic flow) and original collagen solution. The results demonstrated that, by altering a number of parameters, it was possible to control the formation of collagen nanostructured films consisting of naturally occurring fibrils. The spin coating procedure enabled the formation of films with random oriented fibrils, while substrates influenced the fibril packing and surface roughness. The hydrodynamic flow was used for guiding fibril major orientation, while adsorption time, rinsing with buffer and solution concentration influenced the fibril orientation. The clarification of the contribution that different parameters had on thin film formation will enable the design and control of collagen nanobiomaterials with pre-determined characteristics. Highlights: • Nanocharacterization of collagen thin films with AFM • Correlation of collagen thin film morphology with the characteristics of different substrates • Correlation of collagen thin film morphology with the formation methodologies • Formation of collagen nanostructure films consisting of natural occurring fibrils was achieved • Controlled surface characteristics and orientation of collagen fibrils on thin films were achieved.

  17. STUDY OF MAGNETOSTRICTIVE PROPERTIES OF MATERIALS BY MEANS OF METHOD OF ATOMIC FORCE MICROSCOPY

    Directory of Open Access Journals (Sweden)

    D. A. Stepanenko

    2014-01-01

    Full Text Available The article studies and experimentally proves possibility of application of atomic force microscope for measurement of small magnetostrictive deformations of materials. Exemplary results of measurements for the samples made of technically pure nickel exhibiting strong magnetostrictive effect are presented.

  18. Wideband phase-locked loop circuit with real-time phase correction for frequency modulation atomic force microscopy

    OpenAIRE

    Fukuma, Takeshi; Yoshioka, Shunsuke; Asakawa, Hitoshi

    2011-01-01

    We have developed a wideband phase-locked loop (PLL) circuit with real-time phase correction for high-speed and accurate force measurements by frequency modulation atomic force microscopy (FM-AFM) in liquid. A high-speed operation of FM-AFM requires the use of a high frequency cantilever which, however, increases frequency-dependent phase delay caused by the signal delay within the cantilever excitation loop. Such phase delay leads to an error in the force measurements by FM-AFM especially wi...

  19. Atomic force microscopy measurements reveal multiple bonds between Helicobacter pylori blood group antigen binding adhesin and Lewis b ligand.

    Science.gov (United States)

    Parreira, P; Shi, Q; Magalhaes, A; Reis, C A; Bugaytsova, J; Borén, T; Leckband, D; Martins, M C L

    2014-12-01

    The strength of binding between the Helicobacter pylori blood group antigen-binding adhesin (BabA) and its cognate glycan receptor, the Lewis b blood group antigen (Le(b)), was measured by means of atomic force microscopy. High-resolution measurements of rupture forces between single receptor-ligand pairs were performed between the purified BabA and immobilized Le(b) structures on self-assembled monolayers. Dynamic force spectroscopy revealed two similar but statistically different bond populations. These findings suggest that the BabA may form different adhesive attachments to the gastric mucosa in ways that enhance the efficiency and stability of bacterial adhesion.

  20. Modern Atomic Force Microscopy and Its Application to the Study of Genome Architecture

    Science.gov (United States)

    Takeyasu, Kunio; Maruyama, Hugo; Suzuki, Yuki; Hizume, Kohji; Yoshimura, Shige H.

    Recent development of atomic force microscopy (AFM) has been accomplished by various technical and instrumental innovation including high-resolution imaging technology in solution, fast-scanning AFM, and general methods for cantilever modification and force measurement. These modern AFM technologies have made it possible to conduct biological studies under physiological conditions. Application of the recognition imaging mode that can simultaneously obtain a topographic image together with a recognition signal is now successful by using protein- (antibody-) coupled cantilever, and revealed the specific protein bindings on the chromatin. AFM can also be combined with biochemical and cytochemical methods. Recent AFM researches involving series of reconstitution experiments have shown that the efficiency of the chromatin reconstitution by salt-dialysis method is drastically increased simply by using longer ( > 100 kb) and supercoiled DNA. This suggests that the physical properties of DNA are critical for the higher-order chromatin folding. Since double-stranded DNA, like other polymer chains, carries certain elasticity and flexibility, the length of DNA could affect the stability of nucleosome and chromatin fiber. This notion is well supported by the fact that in eukaryotic chromosome, the averaged length of a single chromatin loop is ˜ 100 kb. On the contrary, the large-scale structure of chromatin fiber is affected by a local protein binding. Indeed, histone H1 is essential for the reconstitution of 30 nm fibers. Type II topoisomerase (Topo II) has been known as a major component of chromosomal scaffold and an essential protein for mitotic chromosome condensation. AFM has shown that Topo II binds to bear DNA and clamps two DNA strands even in the absence of ATP, and promotes chromatin compaction depending on the existence of histone H1. Namely, H1-induced 30-nm chromatin fibers were converted into large complex by the effect of Topo II. On the basis of these results

  1. Visualization of subsurface nanoparticles in a polymer matrix using resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy

    Science.gov (United States)

    Kimura, Kuniko; Kobayashi, Kei; Yao, Atsushi; Yamada, Hirofumi

    2016-10-01

    A visualization technique of subsurface features with a nanometer-scale spatial resolution is strongly demanded. Some research groups have demonstrated the visualization of subsurface features using various techniques based on atomic force microscopy. However, the imaging mechanisms have not yet been fully understood. In this study, we demonstrated the visualization of subsurface Au nanoparticles buried in a polymer matrix 900 nm from the surface using two techniques; i.e., resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy. It was clarified that the subsurface features were visualized by the two techniques as the area with a higher contact resonance frequency and a higher Q-factor than those in the surrounding area, which suggests that the visualization is realized by the variation of the contact stiffness and damping of the polymer matrix due to the existence of the buried nanoparticles.

  2. Mapping of Proteomic Composition on the Surfaces of Bacillus spores by Atomic Force Microscopy-based Immunolabeling

    Energy Technology Data Exchange (ETDEWEB)

    Plomp, M; Malkin, A J

    2008-06-02

    Atomic force microscopy provides a unique capability to image high-resolution architecture and structural dynamics of pathogens (e.g. viruses, bacteria and bacterial spores) at near molecular resolution in native conditions. Further development of atomic force microscopy in order to enable the correlation of pathogen protein surface structures with specific gene products is essential to understand the mechanisms of the pathogen life cycle. We have applied an AFM-based immunolabeling technique for the proteomic mapping of macromolecular structures through the visualization of the binding of antibodies, conjugated with nanogold particles, to specific epitopes on Bacillus spore surfaces. This information is generated while simultaneously acquiring the surface morphology of the pathogen. The immunospecificity of this labeling method was established through the utilization of specific polyclonal and monoclonal antibodies that target spore coat and exosporium epitopes of Bacillus atrophaeus and Bacillus anthracis spores.

  3. The effect of electrolytes on dolomite dissolution: nanoscale observations using in situ Atomic Force Microscopy

    Science.gov (United States)

    Urosevic, Maja; Ruiz-Agudo, Encarnacion; Putnis, Christine V.; Cardell, Carolina; Rodriguez-Navarro, Carlos; Putnis, Andrew

    2010-05-01

    carbonate rocks, both in the natural environment, as well as in stone buildings and statuary, where the amount of solutes in pore waters is significant and can vary depending on evaporation and condensation phenomena. References Higgins, S.R.; Hu, X. Self-limiting growth on dolomite: Experimental observations with in situ atomic force microscopy. Geochimica et Cosmochimica Acta, 2005, 69 (8), 2085-2094. Morse, J.W.; Arvidson, R.S. The dissolution kinetics of major sedimentary carbonate minerals. Earth-Science Reviews, 2002, 58, 51-84. Ruiz-Agudo, E.; Kowacz, M.; Putnis, C.V.; Putnis, A. The role of background electrolytes on the kinetics and mechanism of calcite dissolution. Geochimica et Cosmochimica Acta, 2010, 74, 1256-1267.

  4. Gaining insight into the physics of dynamic atomic force microscopy in complex environments using the VEDA simulator

    OpenAIRE

    Kiracofe, Daniel; Melcher, John; Raman, Arvind

    2012-01-01

    Dynamic atomic force microscopy (dAFM) continues to grow in popularity among scientists in many different fields, and research on new methods and operating modes continues to expand the resolution, capabilities, and types of samples that can be studied. But many promising increases in capability are accompanied by increases in complexity. Indeed, interpreting modern dAFM data can be challenging, especially on complicated material systems, or in liquid environments where the behavior is often ...

  5. Probing characteristics of collagen molecules on various surfaces via atomic force microscopy

    Science.gov (United States)

    Su, Hao-Wei; Ho, Mon-Shu; Cheng, Chao-Min

    2012-06-01

    We examine, herein, specific dynamic responses of collagen molecules (i.e., observations of self-assembly and nanometric adhesion force measurements of type-I collagen molecules) as they interact with either a hydrophobic or a hydrophilic surface at two distinct temperatures, using a liquid-type atomic force microscope. We conclude that, regardless of surface hydrophobicity/hydrophilicity, assembled microfibrils eventually distribute homogeneously in accordance with changes in surface-related mechanical properties of collagen molecules at different self-assembly stages.

  6. Nanoscale Subsurface Imaging via Resonant Difference-Frequency Atomic Force Ultrasonic Microscopy

    Science.gov (United States)

    Cantrell, Sean A.; Cantrell, John H.; Lilehei, Peter T.

    2007-01-01

    A novel scanning probe microscope methodology has been developed that employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by the fundamental resonance frequency of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever fundamental resonance. The resonance-enhanced difference-frequency signals are used to create images of embedded nanoscale features.

  7. Atomic Force Microscopy as a Tool for Applied Virology and Microbiology

    Science.gov (United States)

    Zaitsev, Boris

    2003-12-01

    Atomic force microscope (AFM) can be successfully used for simple and fast solution of many applied biological problems. In this paper the survey of the results of the application of atomic force microscope SolverP47BIO (NT-MDT, Russia) in State Research Center of Virology and Biotechnology "Vector" is presented. The AFM has been used: - in applied virology for the counting of viral particles and examination of virus-cell interaction; - in microbiology for measurements and indication of bacterial spores and cells; - in biotechnology for control of biotechnological processes and evaluation of the distribution of particle dimension for viral and bacterial diagnostic assays. The main advantages of AFM in applied researches are simplicity of the processing of sample preparation and short time of the examination.

  8. An observation of nanotwin lamellae in Cd 0.6Mn 0.4Te crystal by atomic force microscopy

    Science.gov (United States)

    George, M. A.; Azoulay, M.; Collins, W. E.; Burger, A.; Silberman, E.

    1993-05-01

    Atomic force microscopy (AFM) is used to examine the structure of freshly cleaved Cd 0.6Mn 0.4Te surfaces. The present report complements previous results obtained with X-ray diffraction and optical microscopy which showed the existence of microtwins. The AFM analysis was performed under ambient conditions and yielded nanometer scale resolution images of single twin lamellae that ranged between 20 and 100 nm in width. This is a first observation using AFM of such a substructure, which we interpret as evidence for the presence of nonotwins.

  9. Effects of conditioners on surface hardness of hair fibers: an investigation using atomic force microscopy.

    Science.gov (United States)

    Ruetsch, S B; Kamath, Y K; Kintrup, L; Schwark, H-J

    2003-01-01

    Conditioners are known to have a prophylactic effect on hair damage caused by cosmetic chemical treatments or mechanical grooming procedures. They are known to impart softness and smoothness to hair by moisturizing the fiber. Since the amount of conditioners deposited on the fiber is very small in quantity, it is conceivable that mainly the surface is moisturized. This is especially true of polymeric conditioners, which deposit preferentially on the surface of the fiber, rather than penetrate into the cortex. Therefore, this study strictly investigates whether cationic polymeric conditioners impart softness to the surface cuticle cell as a result of their hydrophilicity, with no regard to its applicability to cosmetic effects. Such softening can be detected by indentation of the surface and can be quantified by measuring the depth of the indent in real time. Atomic force microscopy (AFM), equipped with nano-indentation capability, is ideally suited for this purpose. In this work it was used to determine changes in the microhardness (micromechanical properties) of the hair fiber surface as a result of fiber/conditioner/moisture interactions. In a preliminary study, we observed that the scale faces of hair treated with Polyquaternium 10 (PQ-10) conditioner gave deeper indents, while scale edges yielded shallower ones in comparison to cuticle cells of untreated hair. This suggests that the conditioner softens the scale face and hardens the scale edges. However, because of significant amounts of conditioner residues left on the scale face, this conclusion was rather ambiguous. Therefore, the study was repeated in which multiple indentations were made on the surface cuticle cells of a larger number of the same hair fibers before and after multiple applications of the conditioner. This reduces errors due to fiber-to-fiber variation in pre-existing microhardness differences in surface cuticle cells. Also, the larger number of fibers investigated in the current work

  10. Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results.

    Science.gov (United States)

    Barettin, Daniele; De Angelis, Roberta; Prosposito, Paolo; Auf der Maur, Matthias; Casalboni, Mauro; Pecchia, Alessandro

    2014-05-16

    We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In₀.₄₈Ga₀.₅₂ buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, [Formula: see text] bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband [Formula: see text] approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further verifications, which have clarified some aspects of the experimental

  11. Microplasticity of surfaces and small volumes: An investigation by atomic force microscopy

    Science.gov (United States)

    Kramer, Donald Eugene

    This study uses atomic force microscopy (AFM) to study the evolution of microplasticity at surfaces and small volumes. It is at these length scales that the assumptions of isotropic and homogenous material properties, two assumptions that underpin much of continuum mechanics, begin to break down. The study begins by examining the indentation of metallic single crystals. It has been suggested that nanoindentation provides a means by which energies associated with dislocation nucleation can be measured. AFM combined with indentation tests on tungsten and Fe 3%-Si single crystals at variable temperature and humidity demonstrates that asperities and oxide thickness play a significant role in the initial deformation process. A flaw based oxide fracture model is proposed that accounts for the asperity and oxide film thickness effects. Plastic zones around nano-contacts are then observed using AFM. This is done first for a range of bulk metals and is used to evaluate a simple model that allows determination of the yield strength from knowledge of the contact load and the extent of the plastic zone. The model is found to accurately predict the yield strength for a variety of metals. However, limits are placed on its applicability. The same technique is then applied to Al 2%-Si thin films on silicon and sapphire substrates. AFM is used to evaluate the evolution of the plastic zone around these contacts. It is demonstrated that the constraint between indenter and substrate controls the evolution of the plastic zone. Based on experimental plastic zone measurements, a first-order model for composite hardness is proposed that accounts for the increasing constraint on mean contact pressure. Finally, a bending fatigue system is developed with an eye toward investigating the fatigue response of thin films and the interaction between contact defects and cyclic loading. AFM is then used to measure slip upset in titanium subjected to large amplitude fully reversed bending fatigue

  12. Nanoplough-constrictions on thin YBCO films made with atomic force microscopy.

    Science.gov (United States)

    Elkaseh, A A O; Büttner, U; Meincken, M; Hardie, G L; Srinivasu, V V; Perold, W J

    2007-09-01

    Utilizing atomic force microscope (AFM) with a diamond tip, we were able to successfully plough nano-constrictions on epitaxially grown YBa2Cu3O(7-x) thin films deposited on MgO substrates. The thickness, width, and length of the obtained constrictions were in the range of a few 100 nm. Furthermore, we managed to produce a new S-type constriction, of which the dimensions are easier to control than for conventional constrictions.

  13. Wideband phase-locked loop circuit with real-time phase correction for frequency modulation atomic force microscopy

    Science.gov (United States)

    Fukuma, Takeshi; Yoshioka, Shunsuke; Asakawa, Hitoshi

    2011-07-01

    We have developed a wideband phase-locked loop (PLL) circuit with real-time phase correction for high-speed and accurate force measurements by frequency modulation atomic force microscopy (FM-AFM) in liquid. A high-speed operation of FM-AFM requires the use of a high frequency cantilever which, however, increases frequency-dependent phase delay caused by the signal delay within the cantilever excitation loop. Such phase delay leads to an error in the force measurements by FM-AFM especially with a low Q factor. Here, we present a method to compensate this phase delay in real time. Combined with a wideband PLL using a subtraction-based phase comparator, the method allows to perform an accurate and high-speed force measurement by FM-AFM. We demonstrate the improved performance by applying the developed PLL to three-dimensional force measurements at a mica/water interface.

  14. Interactions between synaptic vesicle fusion proteins explored by atomic force microscopy.

    Science.gov (United States)

    Yersin, A; Hirling, H; Steiner, P; Magnin, S; Regazzi, R; Hüni, B; Huguenot, P; De los Rios, P; Dietler, G; Catsicas, S; Kasas, S

    2003-07-22

    Measuring the biophysical properties of macromolecular complexes at work is a major challenge of modern biology. The protein complex composed of vesicle-associated membrane protein 2, synaptosomal-associated protein of 25 kDa, and syntaxin 1 [soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) complex] is essential for docking and fusion of neurotransmitter-filled synaptic vesicles with the presynaptic membrane. To better understand the fusion mechanisms, we reconstituted the synaptic SNARE complex in the imaging chamber of an atomic force microscope and measured the interaction forces between its components. Each protein was tested against the two others, taken either individually or as binary complexes. This approach allowed us to determine specific interaction forces and dissociation kinetics of the SNAREs and led us to propose a sequence of interactions. A theoretical model based on our measurements suggests that a minimum of four complexes is probably necessary for fusion to occur. We also showed that the regulatory protein neuronal Sec1 injected into the atomic force microscope chamber prevented the complex formation. Finally, we measured the effect of tetanus toxin protease on the SNARE complex and its activity by on-line registration during tetanus toxin injection. These experiments provide a basis for the functional study of protein microdomains and also suggest opportunities for sensitive screening of drugs that can modulate protein-protein interactions.

  15. Topographic Mapping and Compression Elasticity Analysis of Skinned Cardiac Muscle Fibers in Vitro with Atomic Force Microscopy and Nanoindentation

    OpenAIRE

    2009-01-01

    Surface topography and compression elasticity of bovine cardiac muscle fibers in rigor and relaxing state has been studied with atomic force microscopy. Characteristic sarcomere patterns running along the longitudinal axis of the fibers were clearly observed, and Z-lines, M-lines, I-bands, and A-bands can be distinguished through comparing with TEM images and force curves. AFM height images of fibers had shown a sarcomere length of 1.22±0.02μm (n=5) in rigor with a significant 9% increase in ...

  16. The Tip-Sample Interaction in Atomic Force Microscopy and its Implications for Biological Applications.

    Science.gov (United States)

    Baselt, David Randall

    This thesis describes the construction of an atomic force microscope and its application to the study of tip -sample interactions, primarily through the use of friction and hardness (elasticity) imaging. Part one describes the atomic force microscope, which consists of a scanned-cantilever stage (chapter 2); a versatile digital signal processor-based control system with self-optimizing feedback, lock-in amplifier emulation (for hardness imaging), and macro programmability (chapter 3); and image processing software (chapter 4). Part two describes a number of results that have helped to characterize the tip-sample interaction and the contact imaging modes used for its study. Meniscus forces act laterally as well as normally, and that they vary with position (chapter 5). Friction measurements couple with scanner position and feedback, and the meniscus effects friction images (chapter 6). Sliding of the tip over the sample surface introduces slope-dependence into hardness measurements (chapter 7). Dull tips can create prominent topography artifacts even on very flat surfaces (chapter 8). In an investigation of collagen fibrils, AFM has revealed the characteristic 65 nm banding pattern, a second, minor banding pattern, and microfibrils that run along the fibril axis. The distribution of proteoglycans along the fibrils creates a characteristic pattern in friction images. Although imaging in water reduces interaction forces, water can also make biological samples more sensitive to force. However, for robust biological samples imaged in air, tip shape presents a greater obstacle than tip -sample interaction forces to obtaining high-resolution images. Tip contamination increases tip-sample friction and can occasionally improve resolution (chapter 9). For a separate project I have designed a general -purpose nearfield scanning optical microscope (chapter 10).

  17. Investigation of SNARE-Mediated Membrane Fusion Mechanism Using Atomic Force Microscopy

    Science.gov (United States)

    Abdulreda, Midhat H.; Moy, Vincent T.

    2009-01-01

    Membrane fusion is driven by specialized proteins that reduce the free energy penalty for the fusion process. In neurons and secretory cells, soluble N-ethylmaleimide-sensitive factor-attachment protein (SNAP) receptors (SNAREs) mediate vesicle fusion with the plasma membrane during vesicular content release. Although, SNAREs have been widely accepted as the minimal machinery for membrane fusion, the specific mechanism for SNARE-mediated membrane fusion remains an active area of research. Here, we summarize recent findings based on force measurements acquired in a novel experimental system that uses atomic force microscope (AFM) force spectroscopy to investigate the mechanism(s) of membrane fusion and the role of SNAREs in facilitating membrane hemifusion during SNARE-mediated fusion. In this system, protein-free and SNARE-reconstituted lipid bilayers are formed on opposite (trans) substrates and the forces required to induce membrane hemifusion and fusion or to unbind single v-/t-SNARE complexes are measured. The obtained results provide evidence for a mechanism by which the pulling force generated by interacting trans-SNAREs provides critical proximity between the membranes and destabilizes the bilayers at fusion sites by broadening the hemifusion energy barrier and consequently making the membranes more prone to fusion. PMID:20228892

  18. Imaging and modification of polymers by scanning tunneling and atomic force microscopy

    Science.gov (United States)

    Albrecht, T. R.; Dovek, M. M.; Lang, C. A.; Grütter, P.; Quate, C. F.; Kuan, S. W. J.; Frank, C. W.; Pease, R. F. W.

    1988-08-01

    Direct imaging of ultrathin organic films on solid surfaces is important for a variety of reasons; in particular, the use of such films as ultrathin resists for nanometer scale fabrication and information recording requires that we understand their microstrucure. We have used the Langmuir-Blodgett technique to prepare monolayer and submonolayer films of poly(octadecylacrylate) (PODA) and poly(methylmethacrylate) (PMMA) on graphite substrates. Atomic scale images obtained with the scanning tunneling microscope (STM) and the atomic force microscope of the PODA films showed a variety of structures, including isolated narrow fibrils, parallel groups of fibrils, and an ordered structure consistent with the side chain crystallization expected with that material. The fibrils observed are interpreted as individual polymer chains or small bundles of parallel chains. Images of the PMMA samples show no ordered regions. By applying voltage pulses on the STM tip, we were able to locally modify and apparently cut through the PODA fibrils.

  19. Atomic force microscopy and thermodynamics on taro, a self-cleaning plant leaf

    Science.gov (United States)

    Hüger, E.; Rothe, H.; Frant, M.; Grohmann, S.; Hildebrand, G.; Liefeith, K.

    2009-07-01

    The evolution-optimized leaves of Colocasia esculenta (taro) and Nelumbo nucifera (lotus) are the best optimized self-cleaning surfaces known to date. Using an atomic force microscope device equipped with a piezodriven sample stage which enables a z-range of 100 μm we measured the surface morphology of dried and undried leaves of Colocasia esculenta. Thermodynamic calculations were done to investigate the interaction strength of a water droplet with the surfaces of the morphology shown in the images. The results show that the hierarchical structure produces a stable superhydrophobic state with optimal self-cleaning properties.

  20. Atomic force microscopy characterization of kinase-mediated phosphorylation of a peptide monolayer

    Science.gov (United States)

    Zhuravel, Roman; Amit, Einav; Elbaz, Shir; Rotem, Dvir; Chen, Yu-Ju; Friedler, Assaf; Yitzchaik, Shlomo; Porath, Danny

    2016-11-01

    We describe the detailed microscopic changes in a peptide monolayer following kinase-mediated phosphorylation. A reversible electrochemical transformation was observed using square wave voltammetry (SWV) in the reversible cycle of peptide phosphorylation by ERK2 followed by dephosphorylation by alkaline phosphatase. A newly developed method for analyzing local roughness, measured by atomic force microscope (AFM), showed a bimodal distribution. This may indicate either a hole-formation mechanism and/or regions on the surface in which the peptide changed its conformation upon phosphorylation, resulting in increased roughness and current. Our results provide the mechanistic basis for developing biosensors for detecting kinase-mediated phosphorylation in disease.