WorldWideScience

Sample records for atomic force microscopy

  1. Dynamic atomic force microscopy methods

    Science.gov (United States)

    García, Ricardo; Pérez, Rubén

    2002-09-01

    In this report we review the fundamentals, applications and future tendencies of dynamic atomic force microscopy (AFM) methods. Our focus is on understanding why the changes observed in the dynamic properties of a vibrating tip that interacts with a surface make possible to obtain molecular resolution images of membrane proteins in aqueous solutions or to resolve atomic-scale surface defects in ultra high vacuum (UHV). Our description of the two major dynamic AFM modes, amplitude modulation atomic force microscopy (AM-AFM) and frequency modulation atomic force microscopy (FM-AFM) emphasises their common points without ignoring the differences in experimental set-ups and operating conditions. Those differences are introduced by the different feedback parameters, oscillation amplitude in AM-AFM and frequency shift and excitation amplitude in FM-AFM, used to track the topography and composition of a surface. The theoretical analysis of AM-AFM (also known as tapping-mode) emphasises the coexistence, in many situations of interests, of two stable oscillation states, a low and high amplitude solution. The coexistence of those oscillation states is a consequence of the presence of attractive and repulsive components in the interaction force and their non-linear dependence on the tip-surface separation. We show that key relevant experimental properties such as the lateral resolution, image contrast and sample deformation are highly dependent on the oscillation state chosen to operate the instrument. AM-AFM allows to obtain simultaneous topographic and compositional contrast in heterogeneous samples by recording the phase angle difference between the external excitation and the tip motion (phase imaging). Significant applications of AM-AFM such as high-resolution imaging of biomolecules and polymers, large-scale patterning of silicon surfaces, manipulation of single nanoparticles or the fabrication of single electron devices are also reviewed. FM-AFM (also called non

  2. 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

  3. 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…

  4. Biomolecular Interactions Measured by Atomic Force Microscopy

    NARCIS (Netherlands)

    Willemsen, Oscar H.; Snel, Margot M.E.; Cambi, Alessandra; Greve, Jan; Grooth, de Bart G.; Figdor, Carl G.

    2000-01-01

    Atomic force microscopy (AFM) is nowadays frequently applied to determine interaction forces between biological molecules. Starting with the detection of the first discrete unbinding forces between ligands and receptors by AFM only several years ago, measurements have become more and more quantitati

  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. Electrostatic interaction in atomic force microscopy

    OpenAIRE

    Butt, Hans-Jüurgen

    1991-01-01

    In atomic force microscopy, the stylus experiences an electrostatic force when imaging in aqueous medium above a charged surface. This force has been calculated numerically with continuum theory for a silicon nitrite or silicon oxide stylus. For comparison, the Van der Waals force was also calculated. In contrast to the Van der Waals attraction, the electrostatic force is repulsive. At a distance of 0.5 nm the electrostatic force is typically 10-12-10-10 N and thus comparable in strength to t...

  7. Reconstruction of Undersampled Atomic Force Microscopy Images

    DEFF Research Database (Denmark)

    Jensen, Tobias Lindstrøm; Arildsen, Thomas; Østergaard, Jan;

    2013-01-01

    Atomic force microscopy (AFM) is one of the most advanced tools for high-resolution imaging and manipulation of nanoscale matter. Unfortunately, standard AFM imaging requires a timescale on the order of seconds to minutes to acquire an image which makes it complicated to observe dynamic processes...

  8. Energy dissipation in multifrequency atomic force microscopy.

    Science.gov (United States)

    Pukhova, Valentina; Banfi, Francesco; Ferrini, Gabriele

    2014-01-01

    The instantaneous displacement, velocity and acceleration of a cantilever tip impacting onto a graphite surface are reconstructed. The total dissipated energy and the dissipated energy per cycle of each excited flexural mode during the tip interaction is retrieved. The tip dynamics evolution is studied by wavelet analysis techniques that have general relevance for multi-mode atomic force microscopy, in a regime where few cantilever oscillation cycles characterize the tip-sample interaction. PMID:24778976

  9. Energy dissipation in multifrequency atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Valentina Pukhova

    2014-04-01

    Full Text Available The instantaneous displacement, velocity and acceleration of a cantilever tip impacting onto a graphite surface are reconstructed. The total dissipated energy and the dissipated energy per cycle of each excited flexural mode during the tip interaction is retrieved. The tip dynamics evolution is studied by wavelet analysis techniques that have general relevance for multi-mode atomic force microscopy, in a regime where few cantilever oscillation cycles characterize the tip–sample interaction.

  10. Force modulation for improved conductive-mode atomic force microscopy

    NARCIS (Netherlands)

    Koelmans, Wabe W.; Sebastian, Abu; Despont, Michel; Pozidis, Haris

    2010-01-01

    We present an improved conductive-mode atomic force microscopy (C-AFM) method by modulating the applied loading force on the tip. Unreliable electrical contact and tip wear are the primary challenges for electrical characterization at the nanometer scale. The experiments show that force modulation r

  11. Atomic force microscopy of biological samples.

    Science.gov (United States)

    Allison, David P; Mortensen, Ninell P; Sullivan, Claretta J; Doktycz, Mitchel J

    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). PMID:20672388

  12. 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).

  13. Atom inlays performed at room temperature using atomic force microscopy

    Science.gov (United States)

    Sugimoto, Yoshiaki; Abe, Masayuki; Hirayama, Shinji; Oyabu, Noriaki; Custance, Óscar; Morita, Seizo

    2005-02-01

    The ability to manipulate single atoms and molecules laterally for creating artificial structures on surfaces is driving us closer to the ultimate limit of two-dimensional nanoengineering. However, experiments involving this level of manipulation have been performed only at cryogenic temperatures. Scanning tunnelling microscopy has proved, so far, to be a unique tool with all the necessary capabilities for laterally pushing, pulling or sliding single atoms and molecules, and arranging them on a surface at will. Here we demonstrate, for the first time, that it is possible to perform well-controlled lateral manipulations of single atoms using near-contact atomic force microscopy even at room temperature. We report the creation of 'atom inlays', that is, artificial atomic patterns formed from a few embedded atoms in the plane of a surface. At room temperature, such atomic structures remain stable on the surface for relatively long periods of time.

  14. 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.

  15. 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.

  16. Robust atomic force microscopy using multiple sensors.

    Science.gov (United States)

    Baranwal, Mayank; Gorugantu, Ram S; Salapaka, Srinivasa M

    2016-08-01

    Atomic force microscopy typically relies on high-resolution high-bandwidth cantilever deflection measurements based control for imaging and estimating sample topography and properties. More precisely, in amplitude-modulation atomic force microscopy (AM-AFM), the control effort that regulates deflection amplitude is used as an estimate of sample topography; similarly, contact-mode AFM uses regulation of deflection signal to generate sample topography. In this article, a control design scheme based on an additional feedback mechanism that uses vertical z-piezo motion sensor, which augments the deflection based control scheme, is proposed and evaluated. The proposed scheme exploits the fact that the piezo motion sensor, though inferior to the cantilever deflection signal in terms of resolution and bandwidth, provides information on piezo actuator dynamics that is not easily retrievable from the deflection signal. The augmented design results in significant improvements in imaging bandwidth and robustness, especially in AM-AFM, where the complicated underlying nonlinear dynamics inhibits estimating piezo motions from deflection signals. In AM-AFM experiments, the two-sensor based design demonstrates a substantial improvement in robustness to modeling uncertainties by practically eliminating the peak in the sensitivity plot without affecting the closed-loop bandwidth when compared to a design that does not use the piezo-position sensor based feedback. The contact-mode imaging results, which use proportional-integral controllers for cantilever-deflection regulation, demonstrate improvements in bandwidth and robustness to modeling uncertainties, respectively, by over 30% and 20%. The piezo-sensor based feedback is developed using H∞ control framework. PMID:27587128

  17. Robust atomic force microscopy using multiple sensors

    Science.gov (United States)

    Baranwal, Mayank; Gorugantu, Ram S.; Salapaka, Srinivasa M.

    2016-08-01

    Atomic force microscopy typically relies on high-resolution high-bandwidth cantilever deflection measurements based control for imaging and estimating sample topography and properties. More precisely, in amplitude-modulation atomic force microscopy (AM-AFM), the control effort that regulates deflection amplitude is used as an estimate of sample topography; similarly, contact-mode AFM uses regulation of deflection signal to generate sample topography. In this article, a control design scheme based on an additional feedback mechanism that uses vertical z-piezo motion sensor, which augments the deflection based control scheme, is proposed and evaluated. The proposed scheme exploits the fact that the piezo motion sensor, though inferior to the cantilever deflection signal in terms of resolution and bandwidth, provides information on piezo actuator dynamics that is not easily retrievable from the deflection signal. The augmented design results in significant improvements in imaging bandwidth and robustness, especially in AM-AFM, where the complicated underlying nonlinear dynamics inhibits estimating piezo motions from deflection signals. In AM-AFM experiments, the two-sensor based design demonstrates a substantial improvement in robustness to modeling uncertainties by practically eliminating the peak in the sensitivity plot without affecting the closed-loop bandwidth when compared to a design that does not use the piezo-position sensor based feedback. The contact-mode imaging results, which use proportional-integral controllers for cantilever-deflection regulation, demonstrate improvements in bandwidth and robustness to modeling uncertainties, respectively, by over 30% and 20%. The piezo-sensor based feedback is developed using H∞ control framework.

  18. Investigating cell mechanics with atomic force microscopy.

    Science.gov (United States)

    Haase, Kristina; Pelling, Andrew E

    2015-03-01

    Transmission of mechanical force is crucial for normal cell development and functioning. However, the process of mechanotransduction cannot be studied in isolation from cell mechanics. Thus, in order to understand how cells 'feel', we must first understand how they deform and recover from physical perturbations. Owing to its versatility, atomic force microscopy (AFM) has become a popular tool to study intrinsic cellular mechanical properties. Used to directly manipulate and examine whole and subcellular reactions, AFM allows for top-down and reconstitutive approaches to mechanical characterization. These studies show that the responses of cells and their components are complex, and largely depend on the magnitude and time scale of loading. In this review, we generally describe the mechanotransductive process through discussion of well-known mechanosensors. We then focus on discussion of recent examples where AFM is used to specifically probe the elastic and inelastic responses of single cells undergoing deformation. We present a brief overview of classical and current models often used to characterize observed cellular phenomena in response to force. Both simple mechanistic models and complex nonlinear models have been used to describe the observed cellular behaviours, however a unifying description of cell mechanics has not yet been resolved. PMID:25589563

  19. 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.

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

    Science.gov (United States)

    van der Heijden, Nadine J.; Smith, Daniël; Calogero, Gaetano; Koster, Rik S.; Vanmaekelbergh, Daniel; van Huis, Marijn A.; Swart, Ingmar

    2016-06-01

    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 Δ 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 on Cu(111) and Ir(111). The results are corroborated by density functional theory calculations employing a van der Waals functional.

  1. Atomic Force Microscopy Based Cell Shape Index

    Science.gov (United States)

    Adia-Nimuwa, Usienemfon; Mujdat Tiryaki, Volkan; Hartz, Steven; Xie, Kan; Ayres, Virginia

    2013-03-01

    Stellation is a measure of cell physiology and pathology for several cell groups including neural, liver and pancreatic cells. In the present work, we compare the results of a conventional two-dimensional shape index study of both atomic force microscopy (AFM) and fluorescent microscopy images with the results obtained using a new three-dimensional AFM-based shape index similar to sphericity index. The stellation of astrocytes is investigated on nanofibrillar scaffolds composed of electrospun polyamide nanofibers that has demonstrated promise for central nervous system (CNS) repair. Recent work by our group has given us the ability to clearly segment the cells from nanofibrillar scaffolds in AFM images. The clear-featured AFM images indicated that the astrocyte processes were longer than previously identified at 24h. It was furthermore shown that cell spreading could vary significantly as a function of environmental parameters, and that AFM images could record these variations. The new three-dimensional AFM-based shape index incorporates the new information: longer stellate processes and cell spreading. The support of NSF PHY-095776 is acknowledged.

  2. 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

  3. Dielectrophoretic immobilization of proteins: Quantification by atomic force microscopy.

    Science.gov (United States)

    Laux, Eva-Maria; Knigge, Xenia; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

    2015-09-01

    The combination of alternating electric fields with nanometer-sized electrodes allows the permanent immobilization of proteins by dielectrophoretic force. Here, atomic force microscopy is introduced as a quantification method, and results are compared with fluorescence microscopy. Experimental parameters, for example the applied voltage and duration of field application, are varied systematically, and the influence on the amount of immobilized proteins is investigated. A linear correlation to the duration of field application was found by atomic force microscopy, and both microscopical methods yield a square dependence of the amount of immobilized proteins on the applied voltage. While fluorescence microscopy allows real-time imaging, atomic force microscopy reveals immobilized proteins obscured in fluorescence images due to low S/N. Furthermore, the higher spatial resolution of the atomic force microscope enables the visualization of the protein distribution on single nanoelectrodes. The electric field distribution is calculated and compared to experimental results with very good agreement to atomic force microscopy measurements. PMID:26010162

  4. 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.

  5. 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.

  6. Combined scanning electrochemical-atomic force microscopy.

    Science.gov (United States)

    Macpherson, J V; Unwin, P R

    2000-01-15

    A combined scanning electrochemical microscope (SECM)-atomic force microscope (AFM) is described. The instrument permits the first simultaneous topographical and electrochemical measurements at surfaces, under fluid, with high spatial resolution. Simple probe tips suitable for SECM-AFM, have been fabricated by coating flattened and etched Pt microwires with insulating, electrophoretically deposited paint. The flattened portion of the probe provides a flexible cantilever (force sensor), while the coating insulates the probe such that only the tip end (electrode) is exposed to the solution. The SECM-AFM technique is illustrated with simultaneous electrochemical-probe deflection approach curves, simultaneous topographical and electrochemical imaging studies of track-etched polycarbonate ultrafiltration membranes, and etching studies of crystal surfaces. PMID:10658320

  7. 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.

  8. 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

  9. Depletion interaction measured by colloidal probe atomic force microscopy

    NARCIS (Netherlands)

    Wijting, W.K.; Knoben, W.; Besseling, N.A.M.; Leermakers, F.A.M.; Cohen Stuart, M.A.

    2004-01-01

    We investigated the depletion interaction between stearylated silica surfaces in cyclohexane in the presence of dissolved polydimethylsiloxane by means of colloidal probe atomic force microscopy. We found that the range of the depletion interaction decreases with increasing concentration. Furthermor

  10. Phase contrast and operation regimes in multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Sergio [Departament de Disseny i Programació de Sistemes Electrònics, UPC—Universitat Politècnica de Catalunya Av. Bases, 61, 08242 Manresa (Barcelona) (Spain)

    2014-04-07

    In amplitude modulation atomic force microscopy the attractive and the repulsive force regimes induce phase shifts above and below 90°, respectively. In the more recent multifrequency approach, however, multiple operation regimes have been reported and the theory should be revisited. Here, a theory of phase contrast in multifrequency atomic force microscopy is developed and discussed in terms of energy transfer between modes, energy dissipation and the kinetic energy and energy transfer associated with externally driven harmonics. The single frequency virial that controls the phase shift might undergo transitions in sign while the average force (modal virial) remains positive (negative)

  11. Controlled nanostructure fabrication using atomic force microscopy

    OpenAIRE

    Sapcharoenkun, Chaweewan

    2013-01-01

    Scanning probe microscopy (SPM) nanolithography has been found to be a powerful and low-cost approach for sub-100 nm patterning. In this thesis, the possibility of using a state-of-the-art SPM system to controllably deposit nanoparticles on patterned Si substrates with high positional control has been explored. These nanoparticles have a range of interesting properties and have been characterised by electron microscopy and scanning probe microscopy. The influence of differen...

  12. Atomic force microscopy and direct surface force measurements

    NARCIS (Netherlands)

    Ralston, J.; Larson, I.; Rutland, M.; Feiler, A.; Kleijn, J.M.

    2005-01-01

    The atomic force microscope (AFM) is designed to provide high-resolution (in the ideal case, atomic) topographical analysis, applicable to both conducting and nonconducting surfaces. The basic imaging principle is very simple: a sample attached to a piezoelectric positioner is rastered beneath a sha

  13. 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.

  14. Advances in Atomic Force Microscopy and Scanning Tunneling Microscopy

    Science.gov (United States)

    Albrecht, Thomas Robert

    The scanning tunneling microscope (STM) and the more recently developed atomic force microscope (AFM) are high resolution scanning probe microscopes capable of three dimensional atomic-scale surface profiling. In the AFM, minute forces acting between the tip of a flexible cantilever stylus and the surface of the sample cause deflections of the cantilever which are detected by a tunneling or optical sensor with subangstrom sensitivity. The AFM work presented here involves surface profiling via repulsive contact forces between 10^{-6} and 10^{-9} N in magnitude. In this contact profiling (repulsive) mode the AFM is capable of atomic resolution on both electrically conducting and insulating surfaces (unlike the STM). AFM instrumentation for room temperature and low temperature operation is discussed. The critical component of the AFM is the cantilever stylus assembly, which should have a small mass. Several microfabrication processes have been developed to produce thin film SiO_2 and Si_3N_4 microcantilevers with integrated sharp tips. Atomic resolution has been achieved with the AFM in air on a number of samples, including graphite, MoS _2, TaSe_2, WTe_2, TaS_2, and BN (the first insulator imaged with atomic resolution by any means). Various organic and molecular samples have been imaged with nanometer resolution. The difference between STM and AFM response is shown in images of TaS _2 (a charge density wave material), and in simultaneous STM/AFM images of lattice defects and adsorbates on graphite and MoS_2. A number of artifacts make STM and AFM image interpretation subtle, such as tip shape effects, frictional effects, and tracking in atomic grooves. STM images of moire patterns near grain boundaries confirm the importance of tip shape effects. Various surface modification and lithography techniques have been demonstrated with the STM and AFM, including an STM voltage pulse technique which reproducibly creates 40 A diameter holes on the surface of graphite, and a

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

    OpenAIRE

    Putman, Constant A.J.; Grooth, de, B.G.; Hansma, Paul K.; Hulst, van der, R.W.M.; 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 immunolabeling method using the monoclonal antibody anti-CD3 and a secondary antibody (Goat-anti-Mouse) linked to 30 nm colloidal gold particles. Some of the samples were enhanced by silver deposition...

  16. Measurement adhesion force between fine particle and effect of humidity: An study with Atomic Force Microscopy

    International Nuclear Information System (INIS)

    Adhesion force is interaction between particle- particle and particle surface. First Hertz in 1882 calculated adhesion force between spherical particle and planar surface. Adhesion force in interested for scientist and different industries such as paint, foot, pharmaceutical, etc. In this study we measured adhesion force between fine particle such as silica and silicon and mica surface, with Atomic Force Microscopy. The adhesion force measured between particle-planar surfaces with Atomic Force Microscopy on different humidity and simulated results.

  17. Theory of Atomic-Force Microscopy(STM Theory)

    OpenAIRE

    Sasaki, Naruo; Tsukada, Masaru

    1997-01-01

    The mechanism of force detection of Atomic-Force Microscopy (AFM) is theoretically investigated. First, a theoretical simulation of contact AFM images is performed, and a tip apex structure is studied. It is clarified how the AFM images and the force distributions change as the load varies. It is also revealed that the characteristics of the AFM images such as their detailed microscopic pattern, the symmetry, and the corrugation amplitude, depend strongly on the tip apex structure. Secondly, ...

  18. Capillary forces in tapping mode atomic force microscopy

    NARCIS (Netherlands)

    Zitzler, L.; Herminghaus, S.; Mugele, F.

    2002-01-01

    We investigated the influence of the relative humidity on amplitude and phase of the cantilever oscillation while operating an atomic force microscope (AFM) in the tapping mode. If the free oscillation amplitude A0 exceeds a certain critical amplitude Ac, the amplitude- and phase-distance curves sho

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. Adsorption Geometry Determination of Single Molecules by Atomic Force Microscopy

    OpenAIRE

    Schuler, Bruno; Liu, Wei; Tkatchenko, Alexandre; Moll, Nikolaj; Meyer, Gerhard; Mistry, Anish; Fox, David; GROSS, Leo

    2013-01-01

    We measured the adsorption geometry of single molecules with intramolecular resolution using noncontact atomic force microscopy with functionalized tips. The lateral adsorption position was determined with atomic resolution, adsorption height differences with a precision of 3 pm, and tilts of the molecular plane within 0.2 degrees. The method was applied to five pi-conjugated molecules, including three molecules from the olympicene family, adsorbed on Cu(111). For the olympicenes, we found th...

  4. 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....

  5. Independent analysis of mechanical data from atomic force microscopy

    International Nuclear Information System (INIS)

    Present atomic force microscopes are capable of acquiring large data volumes by point using point force–distance spectroscopic measurements. Even if different trade names and different technical implementations are used, for most of these techniques a force–distance curve in every image pixel is measured, this curve is immediately fitted by some theoretical dependence and results are displayed as a mechanical properties channel (Young modulus, adhesion, etc). Results are processed during the measurement directly in the scanning probe microscopy controller or, after it, by manufacturer provided software. In this paper, we present a software tool for independent numerical processing of such data, including more numerical models for the force–distance curve evaluation and including a simple estimate of uncertainties related to the fitting procedure. This can improve the reliability and the analytical possibilities of mechanical properties mapping methods in an atomic force microscopy. (paper)

  6. 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

  7. Investigating self-assembled protein nanotubes using atomic force microscopy

    OpenAIRE

    Niu, Lijiang

    2009-01-01

    Self-assembled protein nanotubular materials are attractive as putative building blocks for a variety of applications. Knowledge of the three-dimensional structures and the physical properties of these protein nanotubes then becomes a prerequisite for their use in rational materials design. The main purpose of the work presented in this thesis is to investigate both the structural and mechanical properties of protein nanotubes utilizing atomic force microscopy (AFM). Several different protein...

  8. 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.

  9. Comparative study of clinical pulmonary surfactants using atomic force microscopy

    OpenAIRE

    Zhang, Hong; Fan, Qihui; Wang, Yi E.; Neal, Charles R.; Zuo, Yi Y.

    2011-01-01

    Clinical pulmonary surfactant is routinely used to treat premature newborns with respiratory distress syndrome, and has shown great potential in alleviating a number of neonatal and adult respiratory diseases. Despite extensive study of chemical composition, surface activity, and clinical performance of various surfactant preparations, a direct comparison of surfactant films is still lacking. In this study, we use atomic force microscopy to characterize and compare four animal-derived clinica...

  10. Self-oscillating tapping mode atomic force microscopy

    Science.gov (United States)

    Manning, L.; Rogers, B.; Jones, M.; Adams, J. D.; Fuste, J. L.; Minne, S. C.

    2003-09-01

    A piezoelectric microcantilever probe is demonstrated as a self-oscillator used for tapping mode atomic force microscopy. The integrated piezoelectric film on the cantilever serves as the frequency-determining component of an oscillator circuit; oscillation near the cantilever's resonant frequency is maintained by applying positive feedback to the film via this circuit. This new mode, which is a step towards more compact and parallel tapping mode AFM imaging, is demonstrated by imaging an evaporated gold film on a silicon substrate. A self-oscillating frequency spectrum and a force-distance curve are also presented.

  11. 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.

  12. Bifurcation, chaos, and scan instability in dynamic atomic force microscopy

    Science.gov (United States)

    Cantrell, John H.; Cantrell, Sean A.

    2016-03-01

    The dynamical motion at any point on the cantilever of an atomic force microscope can be expressed quite generally as a superposition of simple harmonic oscillators corresponding to the vibrational modes allowed by the cantilever shape. Central to the dynamical equations is the representation of the cantilever-sample interaction force as a polynomial expansion with coefficients that account for the interaction force "stiffness," the cantilever-to-sample energy transfer, and the displacement amplitude of cantilever oscillation. Renormalization of the cantilever beam model shows that for a given cantilever drive frequency cantilever dynamics can be accurately represented by a single nonlinear mass-spring model with frequency-dependent stiffness and damping coefficients [S. A. Cantrell and J. H. Cantrell, J. Appl. Phys. 110, 094314 (2011)]. Application of the Melnikov method to the renormalized dynamical equation is shown to predict a cascade of period doubling bifurcations with increasing cantilever drive force that terminates in chaos. The threshold value of the drive force necessary to initiate bifurcation is shown to depend strongly on the cantilever setpoint and drive frequency, effective damping coefficient, nonlinearity of the cantilever-sample interaction force, and the displacement amplitude of cantilever oscillation. The model predicts the experimentally observed interruptions of the bifurcation cascade for cantilevers of sufficiently large stiffness. Operational factors leading to the loss of image quality in dynamic atomic force microscopy are addressed, and guidelines for optimizing scan stability are proposed using a quantitative analysis based on system dynamical parameters and choice of feedback loop parameter.

  13. 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

  14. 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…

  15. 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

  16. 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.

  17. 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.

  18. Visualisation of xanthan conformation by atomic force microscopy.

    Science.gov (United States)

    Moffat, Jonathan; Morris, Victor J; Al-Assaf, Saphwan; Gunning, A Patrick

    2016-09-01

    Direct visual evidence obtained by atomic force microscopy demonstrates that when xanthan is adsorbed from aqueous solution onto the heterogeneously charged substrate mica, its helical conformation is distorted. Following adsorption it requires annealing for several hours to restore its ordered helical state. Once the helix state reforms, the AFM images obtained showed clear resolution of the periodicity with a value of 4.7nm consistent with the previously predicted models. In addition, the images also reveal evidence that the helix is formed by a double strand, a clarification of an ambiguity of the xanthan ultrastructure that has been outstanding for many years. PMID:27185152

  19. Microstructural Characterization of Hierarchical Structured Surfaces by Atomic Force Microscopy

    Science.gov (United States)

    Ponomareva, A. A.; Moshnikov, V. A.; Suchaneck, G.

    2013-12-01

    In this work, we evaluate the hierarchical surface topography of reactively sputtered nanocrystalline Pb(Zr,Ti)O3 and TiO2 thin films as well as plasma-treated antireflective PET films by means of determining the fractal dimension and power spectral density (PSD) of surface topography recorded by atomic force microscopy (AFM). Local fractal dimension was obtained using the triangulation method. The PSDs of all samples were fitted to the k-correlation model (also called ABC model) valid for a self-affine surface topography. Fractal analysis of AFM images was shown to be an appropriate and easy to use tool for the characterization of hierarchical nanostructures.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Single xanthan molecule preparation and atomic force microscopy observation

    International Nuclear Information System (INIS)

    A newly developed sample preparation technique termed multi-step spin-coating method was used to prepare well-dispersed xanthan molecules on bare mica, 3-aminopropyl triethoxysilane treated mica, nickel ion treated mica and highly oriented pyrolytic graphite, which are widely used as supporting surfaces in the atomic force microscopy (AFM) study. The substrate effects on conformation of single xanthan molecules were also investigated. We believe that this study is of great importance for the in-depth studies on xanthan molecules at the single-molecular level. (authors)

  6. Analysis of Immunolabeled Cells by Atomic Force Microscopy, Optical Microscopy, and Flow Cytometry

    OpenAIRE

    Neagu, C.; Werf, van der, W.; Putman, C.A.J.; Kraan, Y.M.; Grooth, de, B.G.; Hulst, van der, R.W.M.; Greve, J de

    1994-01-01

    In this study we investigated the applicability of the (silver- enhanced) immunogold labeling method for atomic force microscopy. Human lymphocytes were labeled with anti-CD3 conjugated to fluorescein isothiocyanate and a secondary antibody (goat anti-mouse) linked with 1- or 30-nm colloidal gold particles. Silver enhancement was applied o­n these labeled cells to increase the size of the labels. In a setup combining an inverted optical microscope and a stand-alone atomic force microscope, a ...

  7. Microrheology of cells with magnetic force modulation atomic force microscopy.

    Science.gov (United States)

    Rebêlo, L M; de Sousa, J S; Mendes Filho, J; Schäpe, J; Doschke, H; Radmacher, M

    2014-04-01

    We propose a magnetic force modulation method to measure the stiffness and viscosity of living cells using a modified AFM apparatus. An oscillating magnetic field makes a magnetic cantilever oscillate in contact with the sample, producing a small AC indentation. By comparing the amplitude of the free cantilever motion (A0) with the motion of the cantilever in contact with the sample (A1), we determine the sample stiffness and viscosity. To test the method, the frequency-dependent stiffness of 3T3 fibroblasts was determined as a power law k(s)(f) = α + β(f/f¯)(γ) (α = 7.6 × 10(-4) N m(-1), β = 1.0 × 10(-4) N m(-1), f¯ = 1 Hz, γ = 0.6), where the coefficient γ = 0.6 is in good agreement with rheological data of actin solutions with concentrations similar to those in cells. The method also allows estimation of the internal friction of the cells. In particular we found an average damping coefficient of 75.1 μN s m(-1) for indentation depths ranging between 1.0 μm and 2.0 μm. PMID:24651941

  8. 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…

  9. Analysis of force-deconvolution methods in frequency-modulation atomic force microscopy

    OpenAIRE

    Joachim Welker; Esther Illek; Giessibl, Franz J.

    2012-01-01

    In frequency-modulation atomic force microscopy the direct observable is the frequency shift of an oscillating cantilever in a force field. This frequency shift is not a direct measure of the actual force, and thus, to obtain the force, deconvolution methods are necessary. Two prominent methods proposed by Sader and Jarvis (Sader–Jarvis method) and Giessibl (matrix method) are investigated with respect to the deconvolution quality. Both methods show a nontrivial dependence of the deconv...

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Atomic force microscopy analysis of rat pulmonary surfactant films.

    Science.gov (United States)

    Jiao, Xiujun; Keating, Eleonora; Tadayyon, Seyed; Possmayer, Fred; Zuo, Yi Y; Veldhuizen, Ruud A W

    2011-10-01

    Pulmonary surfactant facilitates breathing by forming a surface tension reducing film at the air-liquid interface of the alveoli. The objective was to characterize the structure of surfactant films using endogenous rat surfactant. Solid-support surfactant films, at different surface pressures, were obtained using a Langmuir balance and were analyzed using atomic force microscopy. The results showed a lipid film structure with three distinct phases: liquid expanded, liquid ordered and liquid condensed. The area covered by the liquid condensed domains increased as surface pressure increased. The presence of liquid ordered phase within these structures correlated with the cholesterol content. At a surface pressure of 50 mN/m, stacks of bilayers appeared. Several structural details of these films differ from previous observations made with goat and exogenous surfactants. Overall, the data indicate that surfactant films demonstrate phase separation at low surface pressures and multilayer formation at higher pressure, features likely important for normal surfactant function. PMID:21704443

  16. Unlocking higher harmonics in atomic force microscopy with gentle interactions

    Directory of Open Access Journals (Sweden)

    Sergio Santos

    2014-03-01

    Full Text Available In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.

  17. 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.

  18. 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

  19. Atomic force microscopy-based shape analysis of heart mitochondria.

    Science.gov (United States)

    Lee, Gi-Ja; Park, Hun-Kuk

    2015-01-01

    Atomic force microscopy (AFM) has become an important medical and biological tool for the noninvasive imaging of cells and biomaterials in medical, biological, and biophysical research. The major advantages of AFM over conventional optical and electron microscopes for bio-imaging include the facts that no special coating is required and that imaging can be done in all environments-air, vacuum, or aqueous conditions. In addition, it can also precisely determine pico-nano Newton force interactions between the probe tip and the sample surface from force-distance curve measurements.It is widely known that mitochondrial swelling is one of the most important indicators of the opening of the mitochondrial permeability transition (MPT) pore. As mitochondrial swelling is an ultrastructural change, quantitative analysis of this change requires high-resolution microscopic methods such as AFM. Here, we describe the use of AFM-based shape analysis for the characterization of nanostructural changes in heart mitochondria resulting from myocardial ischemia-reperfusion injury. PMID:25634291

  20. Silicon Carbide Epitaxial Films Studied by Atomic Force Microscopy

    Science.gov (United States)

    1996-01-01

    Silicon carbide (SiC) holds great potential as an electronic material because of its wide band gap energy, high breakdown electric field, thermal stability, and resistance to radiation damage. Possible aerospace applications of high-temperature, high-power, or high-radiation SiC electronic devices include sensors, control electronics, and power electronics that can operate at temperatures up to 600 C and beyond. Commercially available SiC devices now include blue light-emitting diodes (LED's) and high-voltage diodes for operation up to 350 C, with other devices under development. At present, morphological defects in epitaxially grown SiC films limit their use in device applications. Research geared toward reducing the number of structural inhomogeneities can benefit from an understanding of the type and nature of problems that cause defects. The Atomic Force Microscope (AFM) has proven to be a useful tool in characterizing defects present on the surface of SiC epitaxial films. The in-house High-Temperature Integrated Electronics and Sensors (HTIES) Program at the NASA Lewis Research Center not only extended the dopant concentration range achievable in epitaxial SiC films, but it reduced the concentration of some types of defects. Advanced structural characterization using the AFM was warranted to identify the type and structure of the remaining film defects and morphological inhomogeneities. The AFM can give quantitative information on surface topography down to molecular scales. Acquired, in part, in support of the Advanced High Temperature Engine Materials Technology Program (HITEMP), the AFM had been used previously to detect partial fiber debonding in composite material cross sections. Atomic force microscopy examination of epitaxial SiC film surfaces revealed molecular-scale details of some unwanted surface features. Growth pits propagating from defects in the substrate, and hillocks due, presumably, to existing screw dislocations in the substrates, were

  1. 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.

  2. Simultaneous differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Adelaide; De Beule, Pieter A. A., E-mail: pieter.de-beule@inl.int [Applied Nano-Optics Laboratory, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, s/n, 4715-330 Braga (Portugal); Martins, Marco [Nano-ICs Group, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, s/n, 4715-330 Braga (Portugal)

    2015-09-15

    Combined microscopy techniques offer the life science research community a powerful tool to investigate complex biological systems and their interactions. Here, we present a new combined microscopy platform based on fluorescence optical sectioning microscopy through aperture correlation microscopy with a Differential Spinning Disk (DSD) and nanomechanical mapping with an Atomic Force Microscope (AFM). The illumination scheme of the DSD microscope unit, contrary to standard single or multi-point confocal microscopes, provides a time-independent illumination of the AFM cantilever. This enables a distortion-free simultaneous operation of fluorescence optical sectioning microscopy and atomic force microscopy with standard probes. In this context, we discuss sample heating due to AFM cantilever illumination with fluorescence excitation light. Integration of a DSD fluorescence optical sectioning unit with an AFM platform requires mitigation of mechanical noise transfer of the spinning disk. We identify and present two solutions to almost annul this noise in the AFM measurement process. The new combined microscopy platform is applied to the characterization of a DOPC/DOPS (4:1) lipid structures labelled with a lipophilic cationic indocarbocyanine dye deposited on a mica substrate.

  3. Simultaneous differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping atomic force microscopy

    International Nuclear Information System (INIS)

    Combined microscopy techniques offer the life science research community a powerful tool to investigate complex biological systems and their interactions. Here, we present a new combined microscopy platform based on fluorescence optical sectioning microscopy through aperture correlation microscopy with a Differential Spinning Disk (DSD) and nanomechanical mapping with an Atomic Force Microscope (AFM). The illumination scheme of the DSD microscope unit, contrary to standard single or multi-point confocal microscopes, provides a time-independent illumination of the AFM cantilever. This enables a distortion-free simultaneous operation of fluorescence optical sectioning microscopy and atomic force microscopy with standard probes. In this context, we discuss sample heating due to AFM cantilever illumination with fluorescence excitation light. Integration of a DSD fluorescence optical sectioning unit with an AFM platform requires mitigation of mechanical noise transfer of the spinning disk. We identify and present two solutions to almost annul this noise in the AFM measurement process. The new combined microscopy platform is applied to the characterization of a DOPC/DOPS (4:1) lipid structures labelled with a lipophilic cationic indocarbocyanine dye deposited on a mica substrate

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

    Science.gov (United States)

    Kreplak, Laurent

    2016-01-01

    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. PMID:27479503

  5. 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.

  6. Nanomechanical cutting of boron nitride nanotubes by atomic force microscopy.

    Science.gov (United States)

    Zheng, Meng; Chen, Xiaoming; Park, Cheol; Fay, Catharine C; Pugno, Nicola M; Ke, Changhong

    2013-12-20

    The length of nanotubes is a critical structural parameter for the design and manufacture of nanotube-based material systems and devices. High-precision length control of nanotubes by means of mechanical cutting using a scriber has not materialized due to the lack of the knowledge of the appropriate cutting conditions and the tube failure mechanism. In this paper, we present a quantitative nanomechanical study of the cutting of individual boron nitride nanotubes (BNNTs) using atomic force microscopy (AFM) probes. In our nanotube cutting measurements, a nanotube standing still on a flat substrate was laterally scribed by an AFM tip. The tip-tube collision force deformed the tube, and eventually fractured the tube at the collision site by increasing the cutting load. The mechanical response of nanotubes during the tip-tube collision process and the roles of the scribing velocity and the frictional interaction on the tip-tube collision contact in cutting nanotubes were quantitatively investigated by cutting double-walled BNNTs of 2.26-4.28 nm in outer diameter. The fracture strength of BNNTs was also quantified based on the measured collision forces and their structural configurations using contact mechanics theories. Our analysis reports fracture strengths of 9.1-15.5 GPa for the tested BNNTs. The nanomechanical study presented in this paper demonstrates that the AFM-based nanomechanical cutting technique not only enables effective control of the length of nanotubes with high precision, but is also promising as a new nanomechanical testing technique for characterizing the mechanical properties of tubular nanostructures. PMID:24285263

  7. 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...

  8. Simulating photoconductive atomic-force microscopy on disordered photovoltaic materials

    Science.gov (United States)

    Blakesley, James C.; Castro, Fernando A.

    2015-04-01

    We present a tool for simulating photoconductive atomic-force microscopy (Pc-AFM) on bulk heterojunction (BHJ) materials with a minimal set of empirical parameters. The simulation is a master-equation solution of a three-dimensional hopping charge transport model which includes donor-acceptor domain morphology, energetic and spatial disorder, exciton transport and splitting, charge-pair generation and recombination, and tip-substrate electrostatics. A simplifying aspect of the model is that electron transport, hole transport, and electron-hole recombination are treated as the same electron-transfer process. The model recreates realistic bulk recombination rates, without requiring short-range Coulombic effects to be calculated. We demonstrate the tool by simulating line scans of a Pc-AFM tip passing over the surface of a buried or exposed acceptor cluster in a BHJ film. The simulations confirm experimental observations that such defects can be detected by open-circuit mode Pc-AFM imaging, even when the clusters are buried below the surface.

  9. 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.

  10. 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.

  11. Conductive-probe atomic force microscopy characterization of silicon nanowire

    Directory of Open Access Journals (Sweden)

    Yu Linwei

    2011-01-01

    Full Text Available Abstract The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs were investigated using a conductive-probe atomic force microscopy (AFM. Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V. Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated.

  12. Immobilization of different biomolecules by atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Hölzel Ralph

    2010-05-01

    Full Text Available Abstract Background Micrometer resolution placement and immobilization of probe molecules is an important step in the preparation of biochips and a wide range of lab-on-chip systems. Most known methods for such a deposition of several different substances are costly and only suitable for a limited number of probes. In this article we present a flexible procedure for simultaneous spatially controlled immobilization of functional biomolecules by molecular ink lithography. Results For the bottom-up fabrication of surface bound nanostructures a universal method is presented that allows the immobilization of different types of biomolecules with micrometer resolution. A supporting surface is biotinylated and streptavidin molecules are deposited with an AFM (atomic force microscope tip at distinct positions. Subsequent incubation with a biotinylated molecule species leads to binding only at these positions. After washing streptavidin is deposited a second time with the same AFM tip and then a second biotinylated molecule species is coupled by incubation. This procedure can be repeated several times. Here we show how to immobilize different types of biomolecules in an arbitrary arrangement whereas most common methods can deposit only one type of molecules. The presented method works on transparent as well as on opaque substrates. The spatial resolution is better than 400 nm and is limited only by the AFM's positional accuracy after repeated z-cycles since all steps are performed in situ without moving the supporting surface. The principle is demonstrated by hybridization to different immobilized DNA oligomers and was validated by fluorescence microscopy. Conclusions The immobilization of different types of biomolecules in high-density microarrays is a challenging task for biotechnology. The method presented here not only allows for the deposition of DNA at submicrometer resolution but also for proteins and other molecules of biological relevance that

  13. Controlled evaluation of silver nanoparticle dissolution using atomic force microscopy.

    Science.gov (United States)

    Kent, Ronald D; Vikesland, Peter J

    2012-07-01

    Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7.0, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ≥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, the in-plane radius decreased by 5-11 nm, and the height increased by 6-12 nm. Subsequently, particle height and in-plane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of unaggregated AgNP dissolution. PMID:22191460

  14. 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...

  15. 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...

  16. 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.

  17. 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

  18. Is atomic-scale dissipation in NC-AFM real? Investigation using virtual atomic force microscopy

    International Nuclear Information System (INIS)

    Using a virtual dynamic atomic force microscope, that explicitly simulates the operation of a non-contact AFM experiment, we have performed calculations to investigate the formation of atomic-scale contrast in dissipation images. A non-conservative tip-surface interaction was implemented using the theory of dynamical response in scanning probe microscopy with energies and barriers derived from realistic atomistic modelling. It is shown how contrast in the damping signal is due to the hysteresis in the tip-surface force and not an artefact of the finite response of the complicated instrumentation. Topography and dissipation images of the CaO(001) surface are produced which show atomic-scale contrast in the dissipation with a corrugation of approximately 0.1 eV, which is typical of that observed in images of similar binary ionic surfaces. The effect of the fast-direction scanning speed on the image formation is also investigated and discussed

  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. Atomic force microscopy investigations of peptide self-assembly

    OpenAIRE

    Sedman, Victoria L.

    2006-01-01

    The ability of short peptide fragments to self-assemble in isolation as amyloid and amyloid-like structures has prompted their use as model systems for the study of amyloid formation and recently also for their utilisation as novel nanofibrillar material. The atomic force microscope (AFM) is used here to investigate the self-assembly of two peptide systems and the development of strategies to directly manipulate and control the structures they form. The studies presented in Chapter 2 addr...

  1. Nonlinear Dynamics of Tapping Mode Atomic Force Microscopy

    OpenAIRE

    Bahrami, Arash

    2012-01-01

    A mathematical model is developed to investigate the grazing dynamics of tapping mode atomic force microscopes (AFM) subjected to a base harmonic excitation. The nonlinear dynamics of the AFM microcantilever are studied in both of the monostable and bistable phases with the microcantilever tip being, respectively, located in the monostable and bistable regions of the static bifurcation diagram in the reference configuration. Free-vibration responses of the AFM probes, including the microcanti...

  2. 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.

  3. 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.

  4. 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.

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

    Science.gov (United States)

    Kim, Byung I; Boehm, Ryan D

    2013-02-01

    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 0.2s per frame, suggesting that the force-feedback HSAFM was stable for various imaging speeds in imaging softer adhesive biological samples. PMID:23274682

  6. Calibration of lateral force measurements in atomic force microscopy with a piezoresistive force sensor

    International Nuclear Information System (INIS)

    We present here a method to calibrate the lateral force in the atomic force microscope. This method makes use of an accurately calibrated force sensor composed of a tipless piezoresistive cantilever and corresponding signal amplifying and processing electronics. Two ways of force loading with different loading points were compared by scanning the top and side edges of the piezoresistive cantilever. Conversion factors between the lateral force and photodiode signal using three types of atomic force microscope cantilevers with rectangular geometries (normal spring constants from 0.092 to 1.24 N/m and lateral stiffness from 10.34 to 101.06 N/m) were measured in experiments using the proposed method. When used properly, this method calibrates the conversion factors that are accurate to ±12.4% or better. This standard has less error than the commonly used method based on the cantilever's beam mechanics. Methods such of this allow accurate and direct conversion between lateral forces and photodiode signals without any knowledge of the cantilevers and the laser measuring system

  7. Plastic-to-Elastic Transition in Aggregated Emulsion Networks, Studied with Atomic Force Microscopy-Confocal Scanning Laser Microscopy Microrheology

    NARCIS (Netherlands)

    Filip, D.; Duits, M.H.G.; Uricanu, V.I.; Mellema, J.

    2006-01-01

    In this paper, we demonstrate how the simultaneous application of atomic force microscopy (AFM) and confocal scanning laser microscopy (CSLM) can be used to characterize the (local) rheological properties of soft condensed matter at micrometer length scales. Measurement of AFM force curves as a func

  8. The Influence of Physical and Physiological Cues on Atomic Force Microscopy-Based Cell Stiffness Assessment

    OpenAIRE

    Yu-Wei Chiou; Hsiu-Kuan Lin; Ming-Jer Tang; Hsi-Hui Lin; Ming-Long Yeh

    2013-01-01

    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...

  9. Combined atomic force microscopy and voltage pulse technique to accurately measure electrostatic force

    Science.gov (United States)

    Inami, Eiichi; Sugimoto, Yoshiaki

    2016-08-01

    We propose a new method of extracting electrostatic force. The technique is based on frequency modulation atomic force microscopy (FM-AFM) combined with a voltage pulse. In this method, the work that the electrostatic field does on the oscillating tip is measured through the cantilever energy dissipation. This allows us to directly extract capacitive forces including the longer range part, to which the conventional FM-AFM is insensitive. The distance-dependent contact potential difference, which is modulated by local charges distributed on the surfaces of the tip and/or sample, could also be correctly obtained. In the absence of local charges, our method can perfectly reproduce the electrostatic force as a function of the distance and the bias voltage. Furthermore, we demonstrate that the system serves as a sensitive sensor enabling us to check the existence of the local charges such as trapped charges and patch charges.

  10. Microtensile Tests Using In Situ Atomic Force Microscopy

    Science.gov (United States)

    Lang, Udo; Dual, Jurg

    In recent years a new field in the micromechanical characterization of materials has emerged. Researchers started to integrate atomic force microscopes (AFM) into microtensile tests. This allowed to investigate surface deformation of layers with thicknesses in the range of micrometers. In the first part of this article experiments on organic samples are presented followed by developments on anorganic specimens. In the second part of the paper latest developments at the Center of Mechanics of ETH Zurich are presented. The setup allows to monitor crack growth with micrometer resolution. At the same time forces can be measured in the millinewton range. Specimens are made from photodefinable polyimide. The stress-crack- length diagrams of two experiments are presented which enables to identify different stages of crack growth and therefore of fracture behaviour. Finally, possible extensions of the setup employing digital image correlation (DIC) are envisioned by analyzing the displacement field around the crack tip.

  11. 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.

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

    International Nuclear Information System (INIS)

    Highlights: ► Localization of single virus particle. ► Force measurements. ► 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.

  13. 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.

  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. 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

  16. Mechanical manifestations of rare atomic jumps in dynamic force microscopy

    Science.gov (United States)

    Hoffmann, R.; Baratoff, A.; Hug, H. J.; Hidber, H. R.; Löhneysen, H. v.; Güntherodt, H.-J.

    2007-10-01

    The resonance frequency and the excitation amplitude of a silicon cantilever have been measured as a function of distance to a cleaved KBr(001) surface with a low-temperature scanning force microscope (SFM) in ultrahigh vacuum. We identify two regimes of tip-sample distances. Above a site-dependent critical tip-sample distance reproducible data with low noise and no interaction-induced energy dissipation are measured. In this regime reproducible SFM images can be recorded. At closer tip-sample distances, above two distinct atomic sites, the frequency values jump between two limiting curves on a timescale of tens of milliseconds. Furthermore, additional energy dissipation occurs wherever jumps are observed. We attribute both phenomena to rarely occurring changes in the tip apex configuration which are affected by short-range interactions with the sample. Their respective magnitudes are related to each other. A specific candidate two-level system is also proposed.

  17. Analysis of environmental particles by atomic force microscopy, scanning and transmission electron microscopy.

    Science.gov (United States)

    Mavrocordatos, D; Pronk, W; Boiler, M

    2004-01-01

    Due to their large specific surface and their abundance, micro and nano particles play an important role in the transport of micropollutants in the environment. Natural particles are usually composed of a mixture of inorganic amorphous or crystalline material (mainly FeOOH, Fe(x)Oy, Mn(x)Oy and clays) and organic material (humics and polysaccharides). They all tend to occur as very small particles (1-1,000 nm in diameter). Most natural amorphous particles are unstable and tend to transform with time towards more crystalline forms, either by aging or possibly, by dissolution and re-crystallization. Such transformations affect the fate of sorbed micropollutants and the scavenging properties are therefore changed. As these entities are sensitive to dehydration (aggregation, changes in the morphology), it is highly important to observe their morphology in their natural environment and understand their composition at the scale of the individual particles. Also for the understanding and optimization of water treatment technologies, the knowledge of the occurrence and behavior of nano-particles is of high importance. Some of the possible particle analysis methods are presented: aggregation processes, biomineralization, bacterial adhesion, biofilms in freshwaters, ferrihydrite as heavy metals remover from storm water. These examples demonstrate the capabilities and focus of the microscopes. Atomic Force Microscopy (AFM) allows to analyze the particles in their own environment, meaning in air or in the water. Thus, native aspects of particles can be observed. As well, forces of interactions between particles or between particles and other surfaces such as membranes will be highly valuable data. Scanning Electron Microscopy (SEM) and for higher lateral resolution, Transmission Electron Microscopy (TEM) allow measurement of the morphology and composition. Especially, TEM coupled with Electron Energy Loss Spectroscopy (TEM-EELS) is a powerful technique for elemental analysis

  18. Amplitude modulation Atomic Force Microscopy, is acoustic driving in liquid quantitatively reliable?

    NARCIS (Netherlands)

    Liu, F.; Zhao, C.; Mugele, F.; Ende, van den H.T.M.

    2015-01-01

    Measuring quantitative tip–sample interaction forces in dynamic atomic force microscopy in fluids is challenging because of the strong damping of the ambient viscous medium and the fluid-mediated driving forces. This holds in particular for the commonly used acoustic excitation of the cantilever osc

  19. On averaging force curves over heterogeneous surfaces in atomic force microscopy.

    Science.gov (United States)

    Sokolov, I; Kalaparthi, V; Kreshchuk, M; Dokukin, M E

    2012-10-01

    Atomic force microscopy (AFM) can be used to study mechanics at the nanoscale. Biological surfaces and nanocomposites have typically heterogeneous surfaces, both mechanically and chemically. When studying such surfaces with AFM, one needs to collect a large amount of data to make statistically sound conclusions. It is time- and resource-consuming to process each force curve separately. The analysis of an averaged raw force data is a simple and time saving option, which also averages out the noise and measurement artifacts of the force curves being analyzed. Moreover, some biomedical applications require just an average number per biological cell. Here we investigate such averaging, study the possible artifacts due to the averaging, and demonstrate how to minimize or even to avoid them. We analyze two ways of doing the averaging: over the force data for each particular distance (method 1, the most commonly used way), and over the distances for each particular force (method 2). We derive the errors of the methods in finding to the true average rigidity modulus. We show that both methods are accurate (the error is 100×), method 2 underestimates the average rigidity modulus by a factor of 2, whereas the error of method 1 is only 15%. However, when analyzing the different surface chemistry, which reveals itself in the changing long-range forces, the accuracy of the methods behave oppositely: method 1 can produce a noticeable averaging artifact in the deriving of the long-range forces; whereas method 2 can be successfully used to derive the averaged long-range force parameters without artifacts. We exemplify our conclusions by the study of human cervical cancer and normal epithelial cells, which demonstrate different degrees of heterogeneity. PMID:22917859

  20. 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.

  1. 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.

  2. 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

  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. 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.

  5. 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.

  6. 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.

  7. Probing the compressibility of tumor cell nuclei by combined atomic force-confocal microscopy

    NARCIS (Netherlands)

    Krause, M.; Riet, J. te; Wolf, K. van der

    2013-01-01

    The cell nucleus is the largest and stiffest organelle rendering it the limiting compartment during migration of invasive tumor cells through dense connective tissue. We here describe a combined atomic force microscopy (AFM)-confocal microscopy approach for measurement of bulk nuclear stiffness toge

  8. 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.

  9. Surface structure of polymers and their model compounds observed by atomic force microscopy

    NARCIS (Netherlands)

    Stocker, W.; Bickmann, B.; Magonov, S.N.; Cantow, H.-J.; Lotz, B.; Wittmann, J.-C.; Möller, M.

    1992-01-01

    Results of atomic force microscopy (AFM) of normal alkanes, polyethylene, isotactic polypropylene and of a diblock copolymer are presented. Various types of surfaces - naturally and epitaxially grown on different substrates - have been examined from hundreds of nanometers down to the atomic scale. S

  10. High viscosity environments: an unexpected route to obtain true atomic resolution with atomic force microscopy

    International Nuclear Information System (INIS)

    Atomic force microscopy (AFM) is widely used in liquid environments, where true atomic resolution at the solid–liquid interface can now be routinely achieved. It is generally expected that AFM operation in more viscous environments results in an increased noise contribution from the thermal motion of the cantilever, thereby reducing the signal-to-noise ratio (SNR). Thus, viscous fluids such as ionic and organic liquids have been generally avoided for high-resolution AFM studies despite their relevance to, e.g. energy applications. Here, we investigate the thermal noise limitations of dynamic AFM operation in both low and high viscosity environments theoretically, deriving expressions for the amplitude, phase and frequency noise resulting from the thermal motion of the cantilever, thereby defining the performance limits of amplitude modulation, phase modulation and frequency modulation AFM. We show that the assumption of a reduced SNR in viscous environments is not inherent to the technique and demonstrate that SNR values comparable to ultra-high vacuum systems can be obtained in high viscosity environments under certain conditions. Finally, we have obtained true atomic resolution images of highly ordered pyrolytic graphite and mica surfaces, thus revealing the potential of high-resolution imaging in high viscosity environments. (paper)

  11. A Physical Approach to Reduce Nonspecific Adhesion in Molecular Recognition Atomic Force Microscopy

    NARCIS (Netherlands)

    Willemsen, Oscar H.; Snel, Margot M.E.; Kuipers, Laurens; Figdor, Carl G.; Greve, J.; Grooth, de Bart G.

    1999-01-01

    Atomic force microscopy is one of the few techniques that allow analysis of biological recognition processes at the single-molecule level. A major limitation of this approach is the nonspecific interaction between the force sensor and substrate. We have modeled the nonspecific interaction by looking

  12. 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...

  13. 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.

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

    OpenAIRE

    Spedden, Elise; White, James D.; 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 ganglio...

  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 Lithography"…

  16. Probing biofouling resistant polymer brush surfaces by atomic force microscopy based force spectroscopy.

    Science.gov (United States)

    Schön, Peter; Kutnyanszky, Edit; ten Donkelaar, Bas; Santonicola, M Gabriella; Tecim, Tugba; Aldred, Nick; Clare, Anthony S; Vancso, G Julius

    2013-02-01

    The protein repellency and biofouling resistance of zwitterionic poly(sulfobetaine methacrylate)(pSBMA) brushes grafted via surface initiated polymerization (SIP) from silicon and glass substrata was assessed using atomic force microscopy (AFM) adherence experiments. Laboratory settlement assays were conducted with cypris larvae of the barnacle Balanus amphitrite. AFM adherence includes the determination of contact rupture forces when AFM probe tips are withdrawn from the substratum. When the surface of the AFM tip is modified, adherence can be assessed with chemical specifity using a method known as chemical force microscopy (CFM). In this study, AFM tips were chemically functionalized with (a) fibronectin- here used as model for a nonspecifically adhering protein - and (b) arginine-glycine-aspartic acid (RGD) peptide motifs covalently attached to poly(methacrylic acid) (PMAA) brushes as biomimics of cellular adhesion receptors. Fibronectin functionalized tips showed significantly reduced nonspecific adhesion to pSBMA-modified substrata compared to bare gold (2.3±0.75 nN) and octadecanethiol (ODT) self-assembled monolayers (1.3±0.75 nN). PMAA and PMAA-RGD modified probes showed no significant adhesion to pSBMA modified silicon substrata. The results gathered through AFM protein adherence studies were complemented by laboratory fouling studies, which showed no adhesion of cypris larvae of Balanus amphitrite on pSBMA. With regard to its unusually high non-specific adsorption to a wide variety of materials the behavior of fibronectin is analogous to the barnacle cyprid temporary adhesive that also binds well to surfaces differing in polarity, charge and free energy. The antifouling efficacy of pSBMA may, therefore, be directly related to the ability of this surface to resist nonspecific protein adsorption. PMID:23138001

  17. 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.

  18. 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

  19. Distributed force probe bending model of critical dimension atomic force microscopy bias

    Science.gov (United States)

    Ukraintsev, Vladimir A.; Orji, Ndubuisi G.; Vorburger, Theodore V.; Dixson, Ronald G.; Fu, Joseph; Silver, Rick M.

    2013-04-01

    Critical dimension atomic force microscopy (CD-AFM) is a widely used reference metrology technique. To characterize modern semiconductor devices, small and flexible probes, often 15 to 20 nm in diameter, are used. Recent studies have reported uncontrolled and significant probe-to-probe bias variation during linewidth and sidewall angle measurements. To understand the source of these variations, tip-sample interactions between high aspect ratio features and small flexible probes, and their influence on measurement bias, should be carefully studied. Using theoretical and experimental procedures, one-dimensional (1-D) and two-dimensional (2-D) models of cylindrical probe bending relevant to carbon nanotube (CNT) AFM probes were developed and tested. An earlier 1-D bending model was refined, and a new 2-D distributed force (DF) model was developed. Contributions from several factors were considered, including: probe misalignment, CNT tip apex diameter variation, probe bending before snapping, and distributed van der Waals-London force. A method for extracting Hamaker probe-surface interaction energy from experimental probe-bending data was developed. Comparison of the new 2-D model with 1-D single point force (SPF) model revealed a difference of about 28% in probe bending. A simple linear relation between biases predicted by the 1-D SPF and 2-D DF models was found. The results suggest that probe bending can be on the order of several nanometers and can partially explain the observed CD-AFM probe-to-probe variation. New 2-D and three-dimensional CD-AFM data analysis software is needed to take full advantage of the new bias correction modeling capabilities.

  20. The atomic force (AFM), scanning tunneling (STM) and scanning force (SFM) microscopies

    International Nuclear Information System (INIS)

    This work deals with the atomic force (AFM), scanning tunneling (STM) and scanning force (SFM) microscopies. These analysis methods are based on different physical principles. Nevertheless, in all of them, a probe is situated at a few angstroms or at the direct contact of the studied sample and carries out a controlled scanning of the sample surface. Their physical principles and their running ways are described. Their potentialities and limits are given too. With these analysis methods, and more particularly with the AFM can be observed the crystal structure of isolated biological molecules and the tri dimensional structure of biological molecules which are inserted in artificial membranes. One of the future prospect of the AFM in biology is the direct observation of living cells. Indeed, it will offer the opportunity to follow, with time and in space, the individual cells behaviour and their morphological modifications. Others uses and developments of the AFM concerns the in situ analysis of mechanisms which govern the crystal growth or the direct viewing of a protein enzymatic activity. (O.M.). 37 refs., 7 figs

  1. Scanning-tunneling and atomic-force microscopy

    Science.gov (United States)

    (STM and AFM) are allowing for in situ (in air and under water) imaging of mineral surfaces at previously unattainable nanometer to atomic scales. The four images, which represent a range of STM/AFM applications, were all taken on [001] surfaces of hematite. Counterclockwise from bottom left, these micrographs are described as follows: (1) An STM image of oxygen sites on terraces separated by steps—imaged under oil at -300-mV sample bias. The difference in tunneling current between terrace (blue) and step-edge (pink) sites can be related to differences in local electronic structure that may affect the reactivity of the different sites Terraces step downward toward the lower left. A kink site is apparent along one step. (2) An AFM image in air showing the molecular-scale structure of the hematite surface.

  2. Study of surface forces dependence on pH by atomic force microscopy.

    Science.gov (United States)

    Gavoille, J; Takadoum, J

    2002-06-01

    We used an atomic force microscope to investigate silicon nitride tip interactions with various materials (copper, nickel, silicon carbide) as a function of pH. The electrolyte used was 10(-3) M NaCl and the interactions observed through force versus distance curves (attraction or repulsion) depended on the pH value. Interaction forces calculation was derived from force versus distance curve data and the results are discussed in terms of electrostatic interactions using Zeta potential theory. PMID:16290640

  3. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Morawski, Ireneusz [Peter Grünberg Institut (PGI-3) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich (Germany); Institute of Experimental Physics, University of Wrocław, pl. M. Borna 9, 50-204 Wrocław (Poland); Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert [Peter Grünberg Institut (PGI-3) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich (Germany)

    2015-12-15

    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.

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

    Science.gov (United States)

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

    2016-10-21

    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. PMID:27631885

  6. 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.

  7. Mapping Electrostatic Forces Using Higher Harmonics Tapping Mode Atomic Force Microscopy in Liquid

    NARCIS (Netherlands)

    Noort, van S. John T.; Willemsen, Oscar H.; Werf, van der Kees O.; Grooth, de Bart G.; Greve, Jan

    1999-01-01

    A simple model of a damped, harmonic oscillator is used to describe the motion of an atomic force microscope cantilever tapping in fluid. By use of experimentally obtained parameters, excellent agreement is found between theory and experimental results. From the model we estimate that the force appl

  8. Mapping of laser diode radiation intensity by atomic-force microscopy

    Science.gov (United States)

    Alekseev, P. A.; Dunaevskii, M. S.; Slipchenko, S. O.; Podoskin, A. A.; Tarasov, I. S.

    2015-09-01

    The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

  9. Stereological characterization of the γ' particles in a nickel base superalloy: Comparison between transmission electron microscopy and atomic force microscopy techniques

    International Nuclear Information System (INIS)

    Critical comparison of transmission electron microscopy and atomic force microscopy techniques was provided concerning size measurements of γ' precipitates in a nickel-base superalloy. The divergence between results is explained in terms of the resolution limit for atomic force microscopy, linked both to the tip dimension and the diameter of the investigated particles

  10. 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...

  11. Chemical Composition of Polymer Surfaces Imaged by Atomic Force Microscopy and Complementary Approaches

    NARCIS (Netherlands)

    Vancso, G. Julius; Hillborg, Henrik; Schönherr, Holger

    2005-01-01

    In this article we review the recent developments in the field of high resolution lateral mapping of the surface chemical composition of polymers by atomic force microscopy (AFM) and other complementary imaging techniques. The different AFM approaches toward nanometer scale mapping with chemical sen

  12. Metrological investigation of nanostructured polymer surfaces replication using atomic force microscopy

    DEFF Research Database (Denmark)

    Quagliotti, D.; Tosello, G.; Hansen, H. N.

    2015-01-01

    Polymer specimens have been manufactured by injection moulding and measured by atomic force microscopy (AFM) with the aim to investigate the possibility of replicating their surfaces with good fidelity at the sub-μm dimensional scale. Three different cases with surface features in the 100 nm ampl...

  13. 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.

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

    International Nuclear Information System (INIS)

    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

  15. Sample Preparation and Imaging of Single Adenovirus Particle Using Atomic Force Microscopy in Liquid

    NARCIS (Netherlands)

    Liang, Yan; Li Chen, [Unknown; van Rosmalen, Mariska G M; Wuite, Gijs J L; Roos, Wouter H

    2015-01-01

    Atomic force microscopy (AFM), as a sophisticated imaging tool with nanoscale resolution, is widely used in virus research and the application of functional viral particles. To investigate single viruses by AFM in a physiologically relevant environment (liquid), an appropriate surface treatment to p

  16. 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

    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...

  17. An atomic force microscopy study of the interactions between indolicidin and supported planar bilayers

    DEFF Research Database (Denmark)

    Askou, Hans Jakob; Jakobsen, Rasmus Neergaard; Fojan, Peter

    2008-01-01

    Indolicidin, a tryptophane-rich antimicrobial peptide , was used to investigate the interactions with a zwitterionic phosphatidylcholine as a model membrane system. In situ atomic force microscopy in liquid medium and phosphatidylcholine supported planar bilayers enabled the study of the interact...

  18. Hierarchical Networks of Casein Proteins: An Elasticity Study Based on Atomic Force Microscopy

    NARCIS (Netherlands)

    Uricanu, V.I.; Duits, M.H.G.; Mellema, J.

    2004-01-01

    2D- and 3D-atomic force microscopy (AFM) experiments were performed on single casein micelles (CM) in native state, submerged in liquid, using a home-built AFM instrument. The micelles were immobilized via carbodiimide chemistry to a self-assembled monolayer supported on gold-coated slides. Off-line

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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...... over 300-μm-wide apertures, where the membranes are stable toward hundreds of nanoindentations without breakage. © 2010 American Chemical Society....

  4. A physical approach to reduce nonspecific adhesion in molecular recognition atomic force microscopy.

    OpenAIRE

    Willemsen, O H; Snel, M M; Kuipers, L.; Figdor, C.G.; De Greve, J; de Grooth, B G

    1999-01-01

    Atomic force microscopy is one of the few techniques that allow analysis of biological recognition processes at the single-molecule level. A major limitation of this approach is the nonspecific interaction between the force sensor and substrate. We have modeled the nonspecific interaction by looking at the interaction potential between a conical Si3N4 tip with a spherical end face and a mica surface in solution, using DLVO (Derjaguin, Landau, Verwey, Overbeek) theory and numerical calculation...

  5. Quantitative measurement of tip-sample interactions in amplitude modulation atomic force microscopy

    Science.gov (United States)

    Hölscher, H.

    2006-09-01

    The author introduces an algorithm for the reconstruction of the tip-sample interactions in amplitude modulation atomic force microscopy ("tapping mode"). The method is based on the recording of amplitude and phase versus distance curves and allows the reconstruction of tip-sample force and energy dissipation as a function of the actual tip-sample distance. The proposed algorithm is verified by a numerical simulation and applied to a silicon sample in ambient conditions.

  6. Measuring the Elasticity of Clathrin-Coated Vesicles via Atomic Force Microscopy

    OpenAIRE

    Jin, Albert J.; Prasad, Kondury; Smith, Paul D.; Lafer, Eileen M.; Nossal, Ralph

    2006-01-01

    Using a new scheme based on atomic force microscopy (AFM), we investigate mechanical properties of clathrin-coated vesicles (CCVs). CCVs are multicomponent protein and lipid complexes of ∼100 nm diameter that are implicated in many essential cell-trafficking processes. Our AFM imaging resolves clathrin lattice polygons and provides height deformation in quantitative response to AFM-substrate compression force. We model CCVs as multilayered elastic spherical shells and, from AFM measurements, ...

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

    Science.gov (United States)

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

    2016-09-01

    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.

  8. 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. PMID:27420398

  9. High Resolution Imaging by Atomic Force Microscopy: Contribution of short-range force to the imaging

    Science.gov (United States)

    Eguchi, Toyoaki; Kotone, Akiyama; Masanori, Ono; Toshio, Sakurai; Yukio, Hasegawa

    2003-03-01

    Recent developments in force detection technique have made us possible to obtain atomically resolved images of the Si(111)-(7x7) surface by AFM. Compared with STM, however, its spatial resolution remains limited. In this presentation, we demonstrate that with careful pretreatment and appropriate experimental parameters, the structure of the rest-atom layer can be imaged using AFM by detecting the short-range force due to the single chemical bonding. The detection of the short-range force is verified by analysis of the frequency-shift versus distance curve (force curve). This unprecedented high resolution is achieved by reducing background forces due to the long-range interactions with small oscillation amplitude of the cantilever and an atomically sharp tip. The high temperature annealing of the cantilever assists in obtaining a bare silicon tip on the cantilever without unwanted tip-blunting, and improving the Q-factor of the cantilever. This study implies that characterization of the AFM tip in nanometer scale, not only on the apex atoms but also its shape near the apex, is important and critical for AFM high resolution imaging.

  10. Force Spectroscopy of Hyaluronan by Atomic Force Microscopy: From Hydrogen-Bonded Networks toward Single-Chain Behavior

    NARCIS (Netherlands)

    Giannotti, Marina I.; Rinaudo, Marguerite; Vancso, G. Julius

    2007-01-01

    The conformational behavior of hyaluronan (HA) polysaccharide chains in aqueous NaCl solution was characterized directly at the single-molecule level. This comunication reports on one of the first single-chain atomic force microscopy (AFM) experiments performed at variable temperatures, investigatin

  11. 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

    2013-01-01

    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. PMID:24336094

  12. 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.

  13. A simple model of molecular imaging with noncontact atomic force microscopy

    Science.gov (United States)

    Moll, Nikolaj; Gross, Leo; Mohn, Fabian; Curioni, Alessandro; Meyer, Gerhard

    2012-08-01

    Using functionalized tips, the atomic resolution of a single organic molecule can be achieved by noncontact atomic force microscopy (nc-AFM) operating in the regime of short-ranged repulsive Pauli forces. To theoretically describe the atomic contrast in such AFM images, we propose a simple model in which the Pauli repulsion is assumed to follow a power law as a function of the probed charge density. As the exponent in this power law is found to be largely independent of the sample molecule, our model provides a general method for simulating atomically resolved AFM images of organic molecules. For a single perylene-tetracarboxylic-dianhydride (PTCDA) molecule imaged with a CO-terminated tip, we find excellent agreement with the experimental data. Our model eliminates the need to take into account the full tip and sample system and therefore reduces computational cost by three orders of magnitude.

  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. 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.

  16. Noncontact atomic force and Kelvin probe force microscopy on MgO(100) and MgO(100)-supported Ba

    Science.gov (United States)

    Pang, Chi Lun; Sasahara, Akira; Onishi, Hiroshi

    2016-08-01

    Atomically-flat MgO(100) surfaces were prepared by sputtering and annealing. Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) were used to characterize the MgO(100) surfaces. The NC-AFM images revealed the presence of point defects on an atomically-resolved surface. The surface potential at these point defects, as well as features such as step edges and deposited Ba nanoparticles were mapped using KPFM. The Kelvin images show that the surface potential increases at the point defects and at the step edges. On the other hand, a decrease in the potential was found over Ba nanoparticles which can be explained by electron charge transfer from the Ba to the MgO.

  17. Enhanced atomic corrugation in dynamic force microscopy - The role of repulsive forces

    OpenAIRE

    Lichtenstein, L; Büchner, C.; Stuckenholz, S.; Heyde, M; Freund, H.

    2012-01-01

    Full range two dimensional (2D) force mapping was performed by means of low temperature dynamic force microscopy (DFM) on a highly complex surface structure. For this purpose, we used a thin film of vitreous silica on a Ru(0001)-support, which is a 2D structural equivalent to silica glass. The 2D spectroscopy shows that the contrast generating shift in vertical distance between two sites on the surface is twice as large on the repulsive branch of the frequency shift-distance curve as compared...

  18. 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.

  19. 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.

  20. Friction force microscopy

    OpenAIRE

    Roland Bennewitz

    2005-01-01

    Friction force microscopy (FFM) can detect lateral force variations on the atomic scale when sliding a sharp tip over a flat surface. The sliding often takes the form of a stick-slip movement with the same periodicity as the atomic lattice. Here, I discuss how the occurrence of stick-slip instabilities is related to the onset of dissipation. The velocity and load dependence of atomic friction on various materials are discussed in the light of simple classical laws of friction.

  1. Stiffness and heterogeneity of the pulmonary endothelial glycocalyx measured by atomic force microscopy

    OpenAIRE

    O'Callaghan, Ryan; Job, Kathleen M.; Dull, Randal O; Hlady, Vladimir

    2011-01-01

    The mechanical properties of endothelial glycocalyx were studied using atomic force microscopy with a silica bead (diameter ∼18 μm) serving as an indenter. Even at indentations of several hundred nanometers, the bead exerted very low compressive pressures on the bovine lung microvascular endothelial cell (BLMVEC) glycocalyx and allowed for an averaging of stiffness in the bead-cell contact area. The elastic modulus of BLMVEC glycocalyx was determined as a pointwise function of the indentation...

  2. Atomic force microscopy reveals the mechanical design of a modular protein

    OpenAIRE

    Li, Hongbin; Oberhauser, Andres F.; Fowler, Susan B.; Clarke, Jane; Fernandez, Julio M.

    2000-01-01

    Tandem modular proteins underlie the elasticity of natural adhesives, cell adhesion proteins, and muscle proteins. The fundamental unit of elastic proteins is their individually folded modules. Here, we use protein engineering to construct multimodular proteins composed of Ig modules of different mechanical strength. We examine the mechanical properties of the resulting tandem modular proteins by using single protein atomic force microscopy. We show that by combining modules of known mechanic...

  3. Atomic force microscopy: a powerful tool for high-resolution imaging of spermatozoa

    OpenAIRE

    Sen Prasenjit; Chaudhury Koel; Kumar Sunil; Guha Sujoy K

    2005-01-01

    Abstract Atomic force microscopy (AFM) has emerged as the only technique capable of real-time imaging of the surface of a living cell at nano-resolution. Since AFM provides the advantage of directly observing living biological cells in their native environment, this technique has found many applications in pharmacology, biotechnology, microbiology, structural and molecular biology, genetics and other biology-related fields. AFM has also proved to be a valuable tool for reproductive biologists...

  4. 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.

  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. Harnessing the damping properties of materials for high-speed atomic force microscopy

    Science.gov (United States)

    Adams, Jonathan D.; Erickson, Blake W.; Grossenbacher, Jonas; Brugger, Juergen; Nievergelt, Adrian; Fantner, Georg E.

    2016-02-01

    The success of high-speed atomic force microscopy in imaging molecular motors, enzymes and microbes in liquid environments suggests that the technique could be of significant value in a variety of areas of nanotechnology. However, the majority of atomic force microscopy experiments are performed in air, and the tapping-mode detection speed of current high-speed cantilevers is an order of magnitude lower in air than in liquids. Traditional approaches to increasing the imaging rate of atomic force microscopy have involved reducing the size of the cantilever, but further reductions in size will require a fundamental change in the detection method of the microscope. Here, we show that high-speed imaging in air can instead be achieved by changing the cantilever material. We use cantilevers fabricated from polymers, which can mimic the high damping environment of liquids. With this approach, SU-8 polymer cantilevers are developed that have an imaging-in-air detection bandwidth that is 19 times faster than those of conventional cantilevers of similar size, resonance frequency and spring constant.

  7. Effectiveness of Modal Decomposition for Tapping Atomic Force Microscopy Microcantilevers in Liquid Environment.

    Science.gov (United States)

    Kim, Il Kwang; Lee, Soo Il

    2016-05-01

    The modal decomposition of tapping mode atomic force microscopy microcantilevers in liquid environments was studied experimentally. Microcantilevers with different lengths and stiffnesses and two sample surfaces with different elastic moduli were used in the experiment. The response modes of the microcantilevers were extracted as proper orthogonal modes through proper orthogonal decomposition. Smooth orthogonal decomposition was used to estimate the resonance frequency directly. The effects of the tapping setpoint and the elastic modulus of the sample under test were examined in terms of their multi-mode responses with proper orthogonal modes, proper orthogonal values, smooth orthogonal modes and smooth orthogonal values. Regardless of the stiffness of the microcantilever under test, the first mode was dominant in tapping mode atomic force microscopy under normal operating conditions. However, at lower tapping setpoints, the flexible microcantilever showed modal distortion and noise near the tip when tapping on a hard sample. The stiff microcantilever had a higher mode effect on a soft sample at lower tapping setpoints. Modal decomposition for tapping mode atomic force microscopy can thus be used to estimate the characteristics of samples in liquid environments. PMID:27483758

  8. 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.

  9. 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.

  10. Opto-mechanical probe for combining atomic force microscopy and optical near-field surface analysis

    OpenAIRE

    Hoorn, van der, T.; Chavan, D.C.; B. Tiribilli; Margheri, G.; Mank, A.J.G.; Ariese, F.; Iannuzzi, D.

    2014-01-01

    We have developed a new easy-to-use probe that can be used to combine atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). We show that, using this device, the evanescent field, obtained by total internal reflection conditions in a prism, can be visualized by approaching the surface with the scanning tip. Furthermore, we were able to obtain simultaneous AFM and SNOM images of a standard test grating in air and in liquid. The lateral resolution in AFM and SNOM mode ...

  11. Co-axial Electrospun Polyacrylonitrile-Poly(methylmethacrylate) Nanofibers: Atomic Force Microscopy and Compositional Characterization

    Science.gov (United States)

    Zander, N.E.; Strawhecker, K.E.; Orlicki, J.A.; Rawlett, A.M.; Beebe, T.P.

    2011-01-01

    Poly(methylmethacrylate) (PMMA)- Polyacrylonitrile (PAN) fibers were prepared using a conventional single-nozzle electrospinning technique. The as-spun fibers exhibited core-shell morphology as verified by transmission electron microscopy (TEM) and atomic force microscopy (AFM). AFM-phase and modulus mapping images of the fiber cross-section and x-ray photoelectron spectroscopy (XPS) analysis indicated PAN formed the shell and PMMA the core material. XPS, thermal gravimetric analysis (TGA), and elemental analysis were used to determine fiber compositional information. Soaking the fibers in solvent demonstrated removal of the core material, generating hollow PAN fibers. PMID:21928836

  12. 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. PMID:27018633

  13. 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.

  14. 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.

  15. Probing intra-molecular mechanics of single circularly permuted green fluorescent protein with atomic force microscopy

    International Nuclear Information System (INIS)

    We investigated the mechanical unfolding of single circularly permuted green fluorescent protein (cpGFP) with atomic force microscopy (AFM). The molecule was stretched from its N- and C-termini by an external force causing an elongation of the polypeptide chain up to its full length. The features of the force-extension (F-E) curves were found to depend on the stretching speed. At fast speeds, we detected one peak in the F-E curves before final rupture of the extended molecule, which we interpreted as the unfolding of two terminal halves within cpGFP. We observed several more force peaks in a sawtooth pattern at much slower speeds, and explained the appearance of such force peaks as cooperative unfolding of the hidden sub-structures inside each terminal half

  16. 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.

  17. 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

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

    International Nuclear Information System (INIS)

    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*. 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

  20. 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.

  1. Interaction forces between silica surfaces in cationic surfactant solutions: an atomic force microscopy study.

    Science.gov (United States)

    Lüderitz, Liset A C; v Klitzing, Regine

    2013-07-15

    The interaction forces between silicon oxide surfaces in the presence of surfactant solutions were studied. Based on the qualitative and quantitative analysis of these interaction forces the correlation with the structure of the aggregates on the surfaces is analyzed. A colloidal probe atomic force microscope (AFM) was used to measure the forces between two colloidal silica particles and between a colloidal particle and a silicon wafer in the presence of hexadecyltrimethylammonium bromide (CTAB) at concentrations between 0.005 mM and 1.2 mM. Different interaction forces were obtained for the silica particle-silica particle system when compared to those for the silica particle-silicon wafer system for the same studied concentration. This indicates that the silica particles and the silicon wafer have different aggregate morphologies on their surfaces. The point of zero charge (pzc) was obtained at 0.05 mM CTAB concentration for the silica particles and at 0.3mM for the silica particle-silicon wafer system. This indicates a higher charge at the silicon wafer than at the silica particles. The observed long range attractions are explained by nanobubbles present at the silicon oxide surfaces and/or by attractive electrostatic interactions between the surfaces, induced by oppositely charged patches at the opposing Si oxide surfaces. PMID:23647691

  2. Measurements of elastic modulus for human anterior lens capsule with atomic force microscopy: the effect of loading force.

    Science.gov (United States)

    Tsaousis, Konstantinos T; Karagiannidis, Panagiotis G; Kopsachilis, Nikolaos; Symeonidis, Chrysanthos; Tsinopoulos, Ioannis T; Karagkiozaki, Varvara; Lamprogiannis, Lampros P; Logothetidis, Stergios

    2014-06-01

    The purpose of the study was to appraise the effect of loading force magnitude on the determination of the elastic modulus of the anterior lens capsule through atomic force microscopy. Four human anterior lens capsules taken during phacoemulsification cataract surgery were studied, free of epithelial cells, with atomic force microscopy. For the experiment, five different indentation loading forces were applied to near areas of the specimen. Experimental data was exported and analyzed according to the Hertz model to obtain the Young's modulus with regards to the elastic behavior of the material. Force-distance curves were acquired by applying a load of 2, 5, 10, 20 and 30 nN. When examining the results it was evident that determination of Young's modulus of the anterior lens capsule is dependent on the loading force concerning the examined range. Loading forces of 10 and 20 nN led to results without significant difference (p > 0.05) and more reproducible (coefficients of variation 12.4 and 11.7 %, respectively). PMID:24037592

  3. Noncontact Atomic Force Microscopy: An Emerging Tool for Fundamental Catalysis Research.

    Science.gov (United States)

    Altman, Eric I; Baykara, Mehmet Z; Schwarz, Udo D

    2015-09-15

    Although atomic force microscopy (AFM) was rapidly adopted as a routine surface imaging apparatus after its introduction in 1986, it has not been widely used in catalysis research. The reason is that common AFM operating modes do not provide the atomic resolution required to follow catalytic processes; rather the more complex noncontact (NC) mode is needed. Thus, scanning tunneling microscopy has been the principal tool for atomic scale catalysis research. In this Account, recent developments in NC-AFM will be presented that offer significant advantages for gaining a complete atomic level view of catalysis. The main advantage of NC-AFM is that the image contrast is due to the very short-range chemical forces that are of interest in catalysis. This motivated our development of 3D-AFM, a method that yields quantitative atomic resolution images of the potential energy surfaces that govern how molecules approach, stick, diffuse, and rebound from surfaces. A variation of 3D-AFM allows the determination of forces required to push atoms and molecules on surfaces, from which diffusion barriers and variations in adsorption strength may be obtained. Pushing molecules towards each other provides access to intermolecular interaction between reaction partners. Following reaction, NC-AFM with CO-terminated tips yields textbook images of intramolecular structure that can be used to identify reaction intermediates and products. Because NC-AFM and STM contrast mechanisms are distinct, combining the two methods can produce unique insight. It is demonstrated for surface-oxidized Cu(100) that simultaneous 3D-AFM/STM yields resolution of both the Cu and O atoms. Moreover, atomic defects in the Cu sublattice lead to variations in the reactivity of the neighboring O atoms. It is shown that NC-AFM also allows a straightforward imaging of work function variations which has been used to identify defect charge states on catalytic surfaces and to map charge transfer within an individual

  4. [Comparison of cell elasticity analysis methods based on atomic force microscopy indentation].

    Science.gov (United States)

    Wang, Zhe; Hao, Fengtao; Chen, Xiaohu; Yang, Zhouqi; Ding, Chong; Shang, Peng

    2014-10-01

    In order to investigate in greater detail the two methods based on Hertz model for analyzing force-distance curve obtained by atomic force microscopy, we acquired the force-distance curves of Hela and MCF-7 cells by atomic force microscopy (AFM) indentation in this study. After the determination of contact point, Young's modulus in different indentation depth were calculated with two analysis methods of "two point" and "slope fitting". The results showed that the Young's modulus of Hela cell was higher than that of MCF-7 cell,which is in accordance with the F-actin distribution of the two types of cell. We found that the Young's modulus of the cells was decreased with increasing indentation depth and the curve trends by "slope fitting". This indicated that the "slope fitting" method could reduce the error caused by the miscalculation of contact point. The purpose of this study was to provide a guidance for researcher to choose an appropriate method for analyzing AFM indentation force-distance curve. PMID:25764725

  5. Competition of elastic and adhesive properties of carbon nanotubes anchored to atomic force microscopy tips

    International Nuclear Information System (INIS)

    In this paper we address the mechanical properties of carbon nanotubes anchored to atomic force microscopy (AFM) tips in a detailed analysis of experimental results and exhaustive description of a simple model. We show that volume elastic and surface adhesive forces both contribute to the dynamical AFM experimental signals. Their respective weights depend on the nanotube properties and on an experimental parameter: the oscillation amplitude. To quantify the elastic and adhesive contributions, a simple analytical model is used. It enables analytical expressions of the resonance frequency shift and dissipation that can be measured in the atomic force microscopy dynamical frequency modulation mode. It includes the nanotube adhesive contribution to the frequency shift. Experimental data for single-wall and multi-wall carbon nanotubes compare well to the model predictions for different oscillation amplitudes. Three parameters can be extracted: the distance necessary to unstick the nanotube from the surface and two spring constants corresponding to tube compression and to the elastic force required to overcome the adhesion force

  6. 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.

  7. Accurate spring constant calibration for very stiff atomic force microscopy cantilevers

    Energy Technology Data Exchange (ETDEWEB)

    Grutzik, Scott J.; Zehnder, Alan T. [Field of Theoretical and Applied Mechanics, Cornell University, Ithaca, New York 14853 (United States); Gates, Richard S.; Gerbig, Yvonne B.; Smith, Douglas T.; Cook, Robert F. [Nanomechanical Properties Group, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

    2013-11-15

    There are many atomic force microscopy (AFM) applications that rely on quantifying the force between the AFM cantilever tip and the sample. The AFM does not explicitly measure force, however, so in such cases knowledge of the cantilever stiffness is required. In most cases, the forces of interest are very small, thus compliant cantilevers are used. A number of methods have been developed that are well suited to measuring low stiffness values. However, in some cases a cantilever with much greater stiffness is required. Thus, a direct, traceable method for calibrating very stiff (approximately 200 N/m) cantilevers is presented here. The method uses an instrumented and calibrated nanoindenter to determine the stiffness of a reference cantilever. This reference cantilever is then used to measure the stiffness of a number of AFM test cantilevers. This method is shown to have much smaller uncertainty than previously proposed methods. An example application to fracture testing of nanoscale silicon beam specimens is included.

  8. 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.

  9. On the atomic force microscopy characterization of void evolution in severely plastic deformed pure iron

    Science.gov (United States)

    Forouzanmehr, N.; Nili-Ahmadabadi, N.

    2014-08-01

    Different severe plastic deformation comprise equal channel angular pressing (ECAP), shaped cold rolling and drawing, or combined were applied on pure iron to obtain nano structured grains. The results show the formation of high concentration of excess free volume up to about 4% in the cold rolled and drawn specimens. Emphasis has been placed on atomic force microscopy (AFM) observations as additional characterization tools that complement the information provided by other techniques. Since the surface of the materials can be observed with atomic-scale resolution, the AFM is a powerful technique to study porous materials. The microscopy observations detect voids in the nanocrystalline Fe sample- processed by shaped rolling followed by drawing with applied true strain of 7- from nano to sub-micrometer in size. It seems that the coalescence of nanovoids could lead to the formation of micro-voids in the structure of deformed samples.

  10. Amplitude modulation atomic force microscopy, is acoustic driving in liquid quantitatively reliable?

    Science.gov (United States)

    Liu, Fei; Zhao, Cunlu; Mugele, Frieder; van den Ende, Dirk

    2015-09-25

    Measuring quantitative tip-sample interaction forces in dynamic atomic force microscopy in fluids is challenging because of the strong damping of the ambient viscous medium and the fluid-mediated driving forces. This holds in particular for the commonly used acoustic excitation of the cantilever oscillation. Here we present measurements of tip-sample interactions due to conservative DLVO and hydration forces and viscous dissipation forces in aqueous electrolytes using tips with radii varying from typical 20 nm for the DLVO and hydration forces, to 1 μm for the viscous dissipation. The measurements are analyzed using a simple harmonic oscillator model, continuous beam theory with fluid-mediated excitation and thermal noise spectroscopy (TNS). In all cases consistent conservative forces, deviating less than 40% from each other, are obtained for all three approaches. The DLVO forces are even within 5% of the theoretical expectations for all approaches. Accurate measurements of dissipative forces within 15% of the predictions of macroscopic fluid dynamics require the use of TNS or continuous beam theory including fluid-mediated driving. Taking this into account, acoustic driving in liquid is quantitatively reliable. PMID:26335613

  11. 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.

  12. Detection of magnetic-labeled antibody specific recognition events by combined atomic force and magnetic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hong Xia [Center for Advanced Optoelectronic Functional Materials Research, Key Laboratory of UV Light-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun 130024 (China); College of Chemistry, Jilin University, Changchun 130023 (China)], E-mail: xiahong@nenu.edu.cn; Liu Yanmei; Li Jun; Guo Wei; Bai Yubai [College of Chemistry, Jilin University, Changchun 130023 (China)

    2009-09-15

    Atomic force (AFM) and magnetic force microscopy (MFM) were developed to detect biomolecular specific interaction. Goat anti-mouse immunoglobulin (anti-IgG) was covalently attached onto gold substrate modified by a self-assembly monolayer of thioctic acid via 1-ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC) activation. Magnetic-labeled IgG then specifically adsorbed onto anti-IgG surface. The morphological variation was identified by AFM. MFM was proved to be a fine assistant tool to distinguish the immunorecognized nanocomposites from the impurities by detection of the magnetic signal from magnetic-labeled IgG. It would enhance the understanding of biomolecular recognition process.

  13. Detection of magnetic-labeled antibody specific recognition events by combined atomic force and magnetic force microscopy

    Science.gov (United States)

    Hong, Xia; Liu, Yanmei; Li, Jun; Guo, Wei; Bai, Yubai

    2009-09-01

    Atomic force (AFM) and magnetic force microscopy (MFM) were developed to detect biomolecular specific interaction. Goat anti-mouse immunoglobulin (anti-IgG) was covalently attached onto gold substrate modified by a self-assembly monolayer of thioctic acid via 1-ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC) activation. Magnetic-labeled IgG then specifically adsorbed onto anti-IgG surface. The morphological variation was identified by AFM. MFM was proved to be a fine assistant tool to distinguish the immunorecognized nanocomposites from the impurities by detection of the magnetic signal from magnetic-labeled IgG. It would enhance the understanding of biomolecular recognition process.

  14. Detection of magnetic-labeled antibody specific recognition events by combined atomic force and magnetic force microscopy

    International Nuclear Information System (INIS)

    Atomic force (AFM) and magnetic force microscopy (MFM) were developed to detect biomolecular specific interaction. Goat anti-mouse immunoglobulin (anti-IgG) was covalently attached onto gold substrate modified by a self-assembly monolayer of thioctic acid via 1-ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC) activation. Magnetic-labeled IgG then specifically adsorbed onto anti-IgG surface. The morphological variation was identified by AFM. MFM was proved to be a fine assistant tool to distinguish the immunorecognized nanocomposites from the impurities by detection of the magnetic signal from magnetic-labeled IgG. It would enhance the understanding of biomolecular recognition process.

  15. 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.

  16. 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.

  17. A comparative study of surface energy data from atomic force microscopy and from contact angle goniometry

    Energy Technology Data Exchange (ETDEWEB)

    Lamprou, Dimitrios A.; Smith, James R.; Nevell, Thomas G.; Barbu, Eugen [Biomaterials and Drug Delivery Group, School of Pharmacy and Biomedical Sciences, University of Portsmouth, St. Michael' s Building, White Swan Road, Portsmouth PO1 2DT (United Kingdom); Stone, Corinne; Willis, Colin R. [Physical Sciences Department, Dstl Porton Down, Salisbury SP4 0JQ (United Kingdom); Tsibouklis, John, E-mail: john.tsibouklis@port.ac.uk [Biomaterials and Drug Delivery Group, School of Pharmacy and Biomedical Sciences, University of Portsmouth, St. Michael' s Building, White Swan Road, Portsmouth PO1 2DT (United Kingdom)

    2010-06-01

    Forces of adhesion have been measured for interactions involving self-assembled monolayers or polymer-film structures that had each been deposited onto a gold-coated glass substrate and a probing, gold-coated cantilever. The data have been fitted into mathematical models that allow the calculation of surface energy by considering the work done for the separation of the identically coated contacting surfaces. These values of surface energy are in close agreement with those from corresponding contact angle determinations, highlighting the potential usefulness of the technique for the study of surfaces at a resolution level approaching 1000 atoms. Comparative studies show that the employment of the atomic force microscopy technique may be preferable for the study of samples that are susceptible to penetration by liquids or for investigations under conditions that exceed the useful limits of conventional probing techniques involving liquids.

  18. 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.

  19. Demonstration of atomic scale stick-slip events stimulated by the force versus distance mode using atomic force microscopy

    Science.gov (United States)

    Watson, Gregory S.; Dinte, Bradley P.; Blach, Jolanta A.; Myhra, Sverre

    2002-08-01

    It has been shown that longitudinal deformation of the force-sensing/imposing lever can be stimulated by the conventional force versus distance (F-d), analytical mode of a scanning force microscope. Accordingly it is possible to measure simultaneously both in-plane and out-of-plane force components acting between a tip and a surface. Discrete atomic scale stick-slip events have been observed by F-d generated friction loop analysis of cleaved WTe2, Mica and HOPG single crystals, and of a Langmuir-Blodgett film. Due to the lever geometry, the lateral resolution arising from z-stage movement is better by an order of magnitude than that obtained from translation of the x-y-stage.

  20. Structural evaluation of probucol nanoparticles in water by atomic force microscopy.

    Science.gov (United States)

    Moribe, Kunikazu; Limwikrant, Waree; Higashi, Kenjirou; Yamamoto, Keiji

    2012-05-10

    Structural evaluation of probucol nanoparticles coground with polyvinylpyrrolidone K17 and sodium dodecyl sulfate for 90 min was performed by solid-state nuclear magnetic resonance (NMR) spectroscopy and atomic force microscopy (AFM) with force-distance curve analysis. The results of solid-state NMR indicated that the cogrinding changed crystalline probucol to amorphous form. The number-averaged mean heights of probucol particles in the ground mixture (GM) suspension were determined by AFM to be 6 and 15 nm for freshly prepared and 24h-stored samples, respectively. Nucleation and the subsequent crystal growth might have occurred after the GM was dispersed in water. The presence of probucol nanocrystals and agglomeration of the primary probucol nanoparticles were recognized by AFM force-distance curve analysis. AFM could be a promising tool to evaluate the structure of nanoparticles as well as their agglomeration behavior in aqueous media. PMID:22370474

  1. Atomic Force Microscopy in Dynamic Mode with Displacement Current Detection in Double Cantilever Devices

    Science.gov (United States)

    Müller, Falk; Müller, Anne‑Dorothea; Hietschold, Michael; Gessner, Thomas

    2006-03-01

    A cantilever array for dynamic mode atomic force microscopy (AFM) is presented, the vertical displacement of which is analyzed by the detection of displacement currents in the electrodes. Each cantilever in the array consists of an actuation part that allows an independent vertical movement, and a sensor part. The lateral distance between the tips of the different cantilevers is fixed to 10 μm. When operated as an actuator, a voltage is applied between the silicon membrane and the underlaying electrode. Due to the resulting coulomb forces, the vertical position of the tip is controllable. The reaction time in this mode is shorter than the response time of a piezostack. The sensor part, on the other hand, allows the device to work in dynamic mode without a laser deflection system. The vertical resolution achieved is below 1 nm. The dependence of force distance curves on the excitation amplitude is shown.

  2. 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.

  3. Minimising the effect of nanoparticle deformation in intermittent contact amplitude modulation atomic force microscopy measurements

    Science.gov (United States)

    Babic, Bakir; Lawn, Malcolm A.; Coleman, Victoria A.; Jämting, Åsa K.; Herrmann, Jan

    2016-06-01

    The results of systematic height measurements of polystyrene (PS) nanoparticles using intermittent contact amplitude modulation atomic force microscopy (IC-AM-AFM) are presented. The experimental findings demonstrate that PS nanoparticles deform during AFM imaging, as indicated by a reduction in the measured particle height. This deformation depends on the IC-AM-AFM imaging parameters, material composition, and dimensional properties of the nanoparticles. A model for nanoparticle deformation occurring during IC-AM-AFM imaging is developed as a function of the peak force which can be calculated for a particular set of experimental conditions. The undeformed nanoparticle height can be estimated from the model by extrapolation to zero peak force. A procedure is proposed to quantify and minimise nanoparticle deformation during IC-AM-AFM imaging, based on appropriate adjustments of the experimental control parameters.

  4. Frequency, amplitude, and phase measurements in contact resonance atomic force microscopies

    Directory of Open Access Journals (Sweden)

    Gheorghe Stan

    2014-03-01

    Full Text Available The resonance frequency, amplitude, and phase response of the first two eigenmodes of two contact-resonance atomic force microscopy (CR-AFM configurations, which differ in the method used to excite the system (cantilever base vs sample excitation, are analyzed in this work. Similarities and differences in the observables of the cantilever dynamics, as well as the different effect of the tip–sample contact properties on those observables in each configuration are discussed. Finally, the expected accuracy of CR-AFM using phase-locked loop detection is investigated and quantification of the typical errors incurred during measurements is provided.

  5. 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.......32 ± 0.06) lm, i.e., with 1% accuracy, while the ROC linearly increases by (0.52 ± 0.03) lm from the top to the bottom of the sidewalls. Nanometer sized surface defects are also well replicated. In addition, the method allows combining multiple features from differently processed wafers into a single...

  6. Adsorption behavior of hexadecyltrimethylammonium bromide (CTAB) to mica substrates as observed by atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Feng; DU Yukou; YANG Ping; LI Xingchang; TANG Ji'an

    2005-01-01

    Atomic force microscopy is employed to study the adsorption behavior of CTAB to mica surfaces. Results show that conformational transitions from globular micelles→cylindrical micelles→flat films are observed in the process of the adsorption of CTAB to mica at twice the bulk critical concentration. However, in 0.5 cmc CTAB solution, the adsorbed CTAB molecules to mica form the layered film structures, and apparent conformational transitions do not appear. Meanwhile, the phenomena of the adsorption of CTAB to mica and the dissociation of mica surfaces are periodically observed.

  7. 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.

  8. 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.

  9. 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...

  10. The Use of Atomic Force Microscopy for Cytomorphological Analysis of Bacterial Infection Agents.

    Science.gov (United States)

    Nemova, I S; Falova, O E; Potaturkina-Nesterova, N I

    2016-02-01

    Cytomorphological signs of bacterial infection agents were studied by atomic force microscopy. Analysis of the elastic mechanical characteristics of Staphylococcus spp. from the skin of patients with chronic dermatoses showed lower elasticity of S. aureus cell membrane in comparison with that of transitory flora representatives. Significant differences in characteristics of cell membrane relief and presence of fimA pathogenicity factor were detected in E. coli isolated from the reproductive tract mucosa of clinically healthy women and patients with inflammatory urogenital infections. PMID:26899849

  11. Analysis of various sequence-specific triplexes by electron and atomic force microscopies.

    OpenAIRE

    Cherny, D I; Fourcade, A; Svinarchuk, F; Nielsen, P E; Malvy, C; Delain, E

    1998-01-01

    Sequence-specific interactions of 20-mer G,A-containing triple helix-forming oligonucleotides (TFOs) and bis-PNAs (peptide nucleic acids) with double-stranded DNA was visualized by electron (EM) and atomic force (AFM) microscopies. Triplexes formed by biotinylated TFOs are easily detected by both EM and AFM in which streptavidin is a marker. AFM images of the unlabeled triplex within a long plasmid DNA show a approximately 0.4-nm height increment of the double helix within the target site pos...

  12. 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.

  13. 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.

  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. Multimode resistive switching in nanoscale hafnium oxide stack as studied by atomic force microscopy

    Science.gov (United States)

    Hou, Y.; Celano, U.; Goux, L.; Liu, L.; Degraeve, R.; Cheng, Y.; Kang, J.; Jurczak, M.; Vandervorst, W.

    2016-07-01

    The nanoscale resistive switching in hafnium oxide stack is investigated by the conductive atomic force microscopy (C-AFM). The initial oxide stack is insulating and electrical stress from the C-AFM tip induces nanometric conductive filaments. Multimode resistive switching can be observed in consecutive operation cycles at one spot. The different modes are interpreted in the framework of a low defect quantum point contact theory. The model implies that the optimization of the conductive filament active region is crucial for the future application of nanoscale resistive switching devices.

  16. 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...... synthesis process the nanoparticle s' sizes were obtained. To demonstrate the applicability and the reliability of the proposed experimental approach we studied the nanoparticles growth at two different temperatures by spectrophotometric measurements and compared them with the results from AFM experimental...

  17. Atomic force microscopy-coupled microcoils for cellular-scale nuclear magnetic resonance spectroscopy

    Science.gov (United States)

    Mousoulis, Charilaos; Maleki, Teimour; Ziaie, Babak; Neu, Corey P.

    2013-04-01

    We present the coupling of atomic force microscopy (AFM) and nuclear magnetic resonance (NMR) technologies to enable topographical, mechanical, and chemical profiling of biological samples. Here, we fabricate and perform proof-of-concept testing of radiofrequency planar microcoils on commercial AFM cantilevers. The sensitive region of the coil was estimated to cover an approximate volume of 19.4 × 103 μm3 (19.4 pl). Functionality of the spectroscopic module of the prototype device is illustrated through the detection of 1Η resonance in deionized water. The acquired spectra depict combined NMR capability with AFM that may ultimately enable biophysical and biochemical studies at the single cell level.

  18. Atomic force microscopy study of the adsorption of protein molecules on transferred Langmuir monolayer

    International Nuclear Information System (INIS)

    Ordered protein films have been obtained by the adsorption of protein molecules on a Langmuir monolayer, which had previously formed on a silicon substrate, using the Langmuir-Blodgett and molecular self-organization methods. A mixture of cholesterol with dipalmitoylphosphatidylcholine (DPPC) and a polymer-cellulose acetopivalinate-were used as immobilization materials. Protein molecules (catalase and alkaline phosphatase) immobilized on solid substrates have been investigated by atomic force micros-copy. It was shown that the developed combined technique provides a deposition of homogeneous ultrathin protein films with a high degree of filling.

  19. 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...

  20. 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.

  1. Atomic force microscopy studies of domain structures in phase-separated monolayers

    Science.gov (United States)

    Xiao, Shou-Jun; Wu, Hai-Ming; Yang, Xiao-Min; Wei, Yu; Tai, Zi-Hou; Sun, Xing-Zhong

    1994-10-01

    Domain structures were studied with atomic force microscopy (AFM) in binary phase-separated monolayer films composed of 5, 10, 15-triphenyl-20-(4-dl-α-phenylalanylamindo) phenyl porphyrin (TPPP) and one of a series of fatty acids which are arachidic acid (AA), palmitic acid (PA), and lauric acid (LA). The liquid-condensed (LC) domain structures of AA and PA were observed in their corresponding mixed monolayers. However, instead of the fatty acid domain, a liquid-expanded (LE) domain structure of TPPP appears in the mixed monolayer of LA/TPPP.

  2. 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

    2016-09-01

    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.

  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. 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.

  5. 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

  6. 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)

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

    2016-10-28

    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. PMID:27655211

  7. 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.

  8. The Use of Atomic Force Microscopy as a Technique for the Identification of Cancerous Cells

    International Nuclear Information System (INIS)

    The monograph presents the use of atomic force microscopy (AFM) as a tool for the identification of cancerous cells by studies of the expression of different types of molecules directly on the surface of living cells. The full quantitative description (that is not accessible by other techniques) performed for a given type of molecular interactions has been obtained by using the following quantities: an unbinding force, probability, rupture length and the effective spring constant taking into account the stiffness of a single complex. All, these parameters were extracted from AFM measurements The analysis of the interaction forces performed by AFM allows the quantitative determination of: i) the static properties of a single molecular complex where its strength of interaction and stiffness of the studied complex can be obtained, ii) dynamic properties, on the basis of which the kinetic properties of the unbinding process can be delivered, and iii) properties of adhesion clusters, where the interrelation between single complexes can be characterized, in particular the mechanism of the unbinding can be obtained. The presented characterization of the interaction force between single molecules demonstrates that atomic force microscopy can be used as exceptional technique to study the expression of molecules on a cell surface. Such measurements are not limited to a typical interactions occurring between single molecules but also it is possible to study the interactions between parts of molecules. The results presented in this monograph point to a novel approach to identify cancer-related changes in a quantitative way what can be used for describing and confirming the pathological state of a single cell. (author)

  9. 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

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

    Science.gov (United States)

    Harris, Andrew R.; Charras, G. T.

    2011-08-01

    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 ~ 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.

  11. 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.

  12. Characterization of virus-like particles by atomic force microscopy in ambient conditions

    Science.gov (United States)

    Oropesa, Reinier; Ramos, Jorge R.; Falcón, Viviana; Felipe, Ariel

    2013-06-01

    Recombinant virus-like particles (VLPs) are attractive candidates for vaccine design since they resemble native viroids in size and morphology, but they are non-infectious due to the absence of a viral genome. The visualization of surface morphologies and structures can be used to deepen the understanding of physical, chemical, and biological phenomena. Atomic force microscopy (AFM) is a useful tool for the visualization of soft biological samples in a nanoscale resolution. In this work we have investigated the morphology of recombinant surface antigens of hepatitis B (rHBsAg) VLPs from Cuban vaccine against hepatitis B. The rHBsAg VLPs sizes estimated by AFM between 15 and 30 nm are similar to those reported on previous transmission electron microscopy (TEM) studies.

  13. Characterization of virus-like particles by atomic force microscopy in ambient conditions

    International Nuclear Information System (INIS)

    Recombinant virus-like particles (VLPs) are attractive candidates for vaccine design since they resemble native viroids in size and morphology, but they are non-infectious due to the absence of a viral genome. The visualization of surface morphologies and structures can be used to deepen the understanding of physical, chemical, and biological phenomena. Atomic force microscopy (AFM) is a useful tool for the visualization of soft biological samples in a nanoscale resolution. In this work we have investigated the morphology of recombinant surface antigens of hepatitis B (rHBsAg) VLPs from Cuban vaccine against hepatitis B. The rHBsAg VLPs sizes estimated by AFM between 15 and 30 nm are similar to those reported on previous transmission electron microscopy (TEM) studies. (paper)

  14. 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...

  15. 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.

  16. Effect of Alginate Lyase on Biofilm-Grown Helicobacter pylori Probed by Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Alessandro Maiorana

    2015-01-01

    Full Text Available Helicobacter pylori (H. pylori is a microorganism with a pronounced capability of adaptation under environmental stress solicitations. Its persistence and antimicrobial resistance to the drugs commonly used in the anti-H. pylori therapy are associated with the development of a biofilm mainly composed of DNA, proteins, and polysaccharides. A fundamental step to increase the success of clinical treatments is the development of new strategies and molecules able to interfere with the biofilm architecture and thus able to enhance the effects of antibiotics. By using Atomic Force Microscopy and Scanning Electron Microscopy we analyzed the effects of the alginate lyase (AlgL, an enzyme able to degrade a wide class of polysaccharides, on the H. pylori shape, surface morphology, and biofilm adhesion properties. We demonstrated that AlgL generates a noticeable loss of H. pylori coccoid form in favor of the bacillary form and reduces the H. pylori extracellular polymeric substances (EPS.

  17. A study of molecular adsorption of a cationic surfactant on complex surfaces with atomic force microscopy.

    Science.gov (United States)

    Sokolov, I; Zorn, G; Nichols, J M

    2016-02-01

    The study of molecular adsorption on solid surfaces is of broad interest. However, so far the study has been restricted to idealized flat smooth rigid surfaces which are rarely the case in real world applications. Here we describe a study of molecular adsorption on a complex surface of the submicron fibers of a fibrous membrane of regenerated cellulose in aqueous media. We use a cationic surfactant, cetyltrimethylammonium chloride (CTAC), as the adsorbing molecule. We study the equilibrium adsorption of CTAC molecules on the same area of the fibers by sequentially immersing the membrane in pure water, 1 mM and then a 20 mM solution of CTAC. Atomic force microscopy (AFM) is applied to study the adsorption. The force-volume mode is used to record the force-deformation curves of the adsorbed molecules on the fiber surface. We suggest a model to separate the forces due to the adsorbed molecules from the elastic deformation of the fiber. Interestingly, knowledge of the surface geometry is not required in this model provided the surface is made of elastically homogeneous material. Different models are investigated to estimate the amount of the adsorbed molecules based on the obtained force curves. The exponential steric repulsion model fits the force data the best. The amount of the adsorbed surfactant molecules and its dependence on the concentration are found to be reasonable compared to the data previously measured by means of Raman scattering done on a flat surface of silica. PMID:26730682

  18. Investigation of integrin expression on the surface of osteoblast-like cells by atomic force microscopy

    International Nuclear Information System (INIS)

    The transforming growth factor β1 (TGF-β1) is a human cytokine which has been demonstrated to modulate cell surface integrin repertoire. In this work integrin expression in response to TGF-β1 stimulation has been investigated on the surface of human osteoblast-like cells. We used atomic force microscopy (AFM) and confocal laser scanning microscopy to assess integrin expression and to evaluate their distribution over the dorsal side of the plasma membrane. AFM probes have been covalently functionalised with monoclonal antibodies specific to the β1 integrin subunit. Force curves have been collected in order to obtain maps of the interaction between the immobilized antibody and the respective cell membrane receptors. Adhesion peaks have been automatically detected by means of an ad hoc developed data analysis software. The specificity of the detected interactions has been assessed by adding free antibody in the solution and monitoring the dramatic decrease in the recorded interactions. In addition, the effect of TGF-β1 treatment on both the fluorescence signal and the adhesion events has been tested. The level of expression of the β1 integrin subunit was enhanced by TGF-β1. As a further analysis, the adhesion force of the single living cells to the substrate was measured by laterally pushing the cell with the AFM tip and measuring the force necessary to displace it. The treatment with TGF-β1 resulted in a decrease of the cell/substrate adhesion force. Results obtained by AFM have been validated by confocal laser scanning microscopy thus demonstrating the high potential of the AFM technique for the investigation of cell surface receptors distribution and trafficking at the nanoscale.

  19. Investigation of Self Assembled Monolayers (SAM) Applied on Si(100) Surfaces by Atomic Force Microscopy

    International Nuclear Information System (INIS)

    Miniaturization of analytical instrumentation in a molecular and nanometer level has technologically significant. The fabrication of nanopatterns with high resolution SPM nanolithograpy may be applied on atomically flat surfaces. Self Assembled-Monolayers (SAMs) are well-ordered two dimensional molecular assemblies formed by a strong adsorption of an active surfactant on a solid surface. In this study, SAM organic thin film method is applied on silicon surfaces. We used various cleaning procedures such as chemical cleaning, ion beam treatment, on p-type Si(1OO) surfaces. SAMs films were produced from bipolar amphiphiles, Octadecylamine ODA-HCl, 1,12-diaminododecane (DAD) and n-tridecylamine (TDA) molecules on Si wafers. Contact mode scanning method and roughness analysis on the scan images were utilized on the SAM coated and uncoated surfaces by Atomic Force Microscopy

  20. 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.

  1. 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.

  2. Friction force microscopy

    Directory of Open Access Journals (Sweden)

    Roland Bennewitz

    2005-05-01

    Full Text Available Friction force microscopy (FFM can detect lateral force variations on the atomic scale when sliding a sharp tip over a flat surface. The sliding often takes the form of a stick-slip movement with the same periodicity as the atomic lattice. Here, I discuss how the occurrence of stick-slip instabilities is related to the onset of dissipation. The velocity and load dependence of atomic friction on various materials are discussed in the light of simple classical laws of friction.

  3. Single-molecule imaging of DNA polymerase I (Klenow fragment) activity by atomic force microscopy

    Science.gov (United States)

    Chao, J.; Zhang, P.; Wang, Q.; Wu, N.; Zhang, F.; Hu, J.; Fan, C. H.; Li, B.

    2016-03-01

    We report a DNA origami-facilitated single-molecule platform that exploits atomic force microscopy to study DNA replication. We imaged several functional activities of the Klenow fragment of E. coli DNA polymerase I (KF) including binding, moving, and dissociation from the template DNA. Upon completion of these actions, a double-stranded DNA molecule was formed. Furthermore, the direction of KF activities was captured and then confirmed by shifting the KF binding sites on the template DNA.We report a DNA origami-facilitated single-molecule platform that exploits atomic force microscopy to study DNA replication. We imaged several functional activities of the Klenow fragment of E. coli DNA polymerase I (KF) including binding, moving, and dissociation from the template DNA. Upon completion of these actions, a double-stranded DNA molecule was formed. Furthermore, the direction of KF activities was captured and then confirmed by shifting the KF binding sites on the template DNA. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06544e

  4. 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

  5. Quantitative Roughness Analysis of Post-harvest Agaricus bisporus by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    YANGHong-Shun; FENGGuo-Ping; ANHong-Jie; LIYun-Fei

    2004-01-01

    The moisture loss degree is important in determining the quality of post-harvest mushroom (Agaricus bisporus (Lange) Sing). Quantitative roughness analyzed by atomic force microscopy (AFM) was proposed to denote the degree of shrinkage, with arithmetic average roughness (Ra) and root mean square roughness (Rq) as parameters, The initial value of Ra was (30.035±1.839)nm, while those of 2℃, 25℃ and dynamic temperature on the 2nd day were (40.139±3.359) nm, (54.393±13.534) nm and (41.197±6.555) nm, respectively. There is a similar tendency for the results of Ra and Rq Both values of roughness increased in duration of storage and with increasing temperatures. The three-dimensional profile of the pileus epicutis could signify the process of water evaporation intuitionally. The tendency was in accordance with the roughness results, especially for the earlier stage of the storage (0-2 d). The outcome of roughness analysis could signify the differences of storage conditions. It was shown that the roughness measured by atomic force microscopy effectively reflected the moisture loss degree of the mushroom pileus epicutis during post-harvest storage.

  6. 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.

  7. Stiffness and heterogeneity of the pulmonary endothelial glycocalyx measured by atomic force microscopy.

    Science.gov (United States)

    O'Callaghan, Ryan; Job, Kathleen M; Dull, Randal O; Hlady, Vladimir

    2011-09-01

    The mechanical properties of endothelial glycocalyx were studied using atomic force microscopy with a silica bead (diameter ∼18 μm) serving as an indenter. Even at indentations of several hundred nanometers, the bead exerted very low compressive pressures on the bovine lung microvascular endothelial cell (BLMVEC) glycocalyx and allowed for an averaging of stiffness in the bead-cell contact area. The elastic modulus of BLMVEC glycocalyx was determined as a pointwise function of the indentation depth before and after enzymatic degradation of specific glycocalyx components. The modulus-indentation depth profiles showed the cells becoming progressively stiffer with increased indentation. Three different enzymes were used: heparinases III and I and hyaluronidase. The main effects of heparinase III and hyaluronidase enzymes were that the elastic modulus in the cell junction regions increased more rapidly with the indentation than in BLMVEC controls, and that the effective thickness of glycocalyx was reduced. Cytochalasin D abolished the modulus increase with the indentation. The confocal profiling of heparan sulfate and hyaluronan with atomic force microscopy indentation data demonstrated marked heterogeneity of the glycocalyx composition between cell junctions and nuclear regions. PMID:21705487

  8. Local elasticity and mobility of twin boundaries in martensitic films studied by atomic force acoustic microscopy

    Science.gov (United States)

    Luo, Yuansu; Büchsenschütz-Göbeler, Matthias; Arnold, Walter; Samwer, Konrad

    2014-01-01

    Nanoscale elastic properties of twinned martensite NiMnGa films were characterized by means of atomic force acoustic microscopy using cantilever contact-resonance spectra to measure the local contact stiffness k* and the local damping Q-1, which contains information on the crystallographic anisotropy of martensitic twin variants and the dissipative motion of twin boundaries (TBs). Images of k* and indentation modulus maps were obtained. Similar to topography images measured by conventional atomic force microscopy in contact mode, they show the nature of the twin structure and thus a regular variation in local elastic modulus. A correlation between k* and Q-1 was observed and mirrors the motion of the TB accompanied by a viscoelastic procedure. The k*-image and the topography image measured are opposite in contrast, which likely arises from mobile and immobile TBs depending on the geometry of twinning. Multi-resonance spectra were measured, which can be related to martensitic multivariants and are explainable as different types of nanotwins. A critical stress, defined as the starting point of softening due to TB movement was determined to be about 0.5 GPa for a thick film (1 μm) and 0.75 GPa for a thin film (0.15 μm), respectively. The values are much larger than that measured for bulk materials, but reasonable due to a large internal stress in the films.

  9. Activity investigation of pinostrobin towards herpes simplex virus-1 as determined by atomic force microscopy.

    Science.gov (United States)

    Wu, Nan; Kong, Yu; Zu, Yuangang; Fu, Yujie; Liu, Zhiguo; Meng, Ronghua; Liu, Xia; Efferth, Thomas

    2011-01-15

    In the present study, the antiviral activity of pinostrobin towards herpes simplex virus-1 (HSV-1) was investigated by MTT assay and atomic force microscopy. Pinostrobin can inhibit HSV-1 replication with 50% effective concentration (EC(50)) of 22.71 ± 1.72 μg/ml. MTT assay showed HSV-1 was significantly inhibited when pretreated with pinostrobin, with the inhibition of 85.69 ± 2.59%. Significant changes in morphology and size of HSV-1 were observed by atomic force microscopy (AFM) in response to pinostrobin treatment. AFM topography and phase images showed that with increasing time, the envelope was shedded and damaged, finally leading to virus inactivation. With increasing concentration, pinostrobin caused a gradual leakage, also contributing to breakage of the envelope and virus inactivation. Treatment effect of oral pinostrobin in vivo showed that pinostrobin (50mg/kg/dose) possesses definite therapeutical effect in the development of lesion score. In general, the results showed that AFM represents a powerful technique for the investigation of morphology and size of HSV-1 treated by antiviral agents. AFM is applicable to study chemically induced morphological changes at the nanometer level. PMID:20739162

  10. Atomic force microscopy study of the antibacterial effect of fosfomycin on methicillin-resistant Staphylococcus pseudintermedius

    Science.gov (United States)

    Neethirajan, Suresh; DiCicco, Matthew

    2014-08-01

    The influence of fosfomycin on methicillin-resistant Staphylococcus pseudintermedius (MRSP) as the target cell was studied by atomic force microscopy (AFM). Nanoscale images of the effects of the antibiotic fosfomycin on this gram-positive bacterium's cell were obtained in situ without fixing agents. Our study has demonstrated substantial morphological and topographical differences between the control and fosfomycin-treated MRSP cells. The AFM investigations further revealed the rough surface morphology and a 30 % shrinkage in size of the fosfomycin-treated cell and the leakage of cytoplasmic components from the cell. The damage of cell membrane integrity and the cell surface degradation as observed elaborates the antibacterial activity of fosfomycin. The AFM image analysis also reveals that the fosfomycin inhibits cell division, and prevents the adhesion on the surface discouraging the biofilm attachment. The micro-titre plate assay results conform to the atomic force microscopy image analysis. This is the first visual demonstration of the effect of fosfomycin on MRSP cells.

  11. Atomic force microscopy and mechanical testing of bovine pericardium irradiated to radiotherapy doses

    International Nuclear Information System (INIS)

    Within the context of radiotherapy our work investigates the feasibility of identifying changes in structural and biomechanical properties of pericardium resulting from exposure to penetrating photon irradiation. Collagen fibres extracted from bovine pericardium were chosen as a model of pericardium extracellular matrix as these form the main fibrous component of the medium. Tests of mechanical properties, controlled by the various structural elements of the tissues, were performed on frontal pericardium, including uni-axial tests and atomic force microscopy (AFM). While the irradiated collagen fibres showed no significant change in D-band spacing up to doses of 80 Gy, the fibre width was found to increase by 34±9% at 80 Gy when compared with that for un-irradiated samples. - Highlights: • Methods for identifying changes in tissue biophysical properties following photon irradiation. • Tests made using collagen fibres extracted from bovine pericardium. • Sensitivity of uni-axial tests and atomic force microscopy (AFM) investigated. • Radiotherapy doses investigated up to 80 Gy, delivered by 6 MV photons

  12. 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.

  13. Ab initio simulations of subatomic resolution images in noncontact atomic force microscopy

    Science.gov (United States)

    Kim, Minjung; Chelikowsky, James R.

    2015-03-01

    Direct imaging of polycyclic aromatic molecules with a subatomic resolution has recently been achieved with noncontact atomic force microscopy (nc-AFM). Specifically, nc-AFM employing a CO functionalized tip has provided details of the chemical bond in aromatic molecules, including the discrimination of bond order. However, the underlying physics of such high resolution imaging remains problematic. By employing new, efficient algorithms based on real space pseudopotentials, we calculate the forces between the nc-AFM tip and specimen. We simulate images of planar organic molecules with two different approaches: 1) with a chemically inert tip and 2) with a CO functionalized tip. We find dramatic differences in the resulting images, which are consistent with recent experimental work. Our work is supported by the DOE under DOE/DE-FG02-06ER46286 and by the Welch Foundation under Grant F-1837. Computational resources were provided by NERSC and XSEDE.

  14. Accurate formula for dissipative interaction in frequency modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Kazuhiro; Matsushige, Kazumi; Yamada, Hirofumi [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan); Kobayashi, Kei [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan); The Hakubi Center for Advanced Research, Kyoto University, Katsura, Nishikyo, Kyoto 615-8520 (Japan); Labuda, Aleksander [Department of Physics, McGill University, Montreal H3A 2T8 (Canada)

    2014-12-08

    Much interest has recently focused on the viscosity of nano-confined liquids. Frequency modulation atomic force microscopy (FM-AFM) is a powerful technique that can detect variations in the conservative and dissipative forces between a nanometer-scale tip and a sample surface. We now present an accurate formula to convert the dissipation power of the cantilever measured during the experiment to damping of the tip-sample system. We demonstrated the conversion of the dissipation power versus tip-sample separation curve measured using a colloidal probe cantilever on a mica surface in water to the damping curve, which showed a good agreement with the theoretical curve. Moreover, we obtained the damping curve from the dissipation power curve measured on the hydration layers on the mica surface using a nanometer-scale tip, demonstrating that the formula allows us to quantitatively measure the viscosity of a nano-confined liquid using FM-AFM.

  15. Accurate formula for dissipative interaction in frequency modulation atomic force microscopy

    Science.gov (United States)

    Suzuki, Kazuhiro; Kobayashi, Kei; Labuda, Aleksander; Matsushige, Kazumi; Yamada, Hirofumi

    2014-12-01

    Much interest has recently focused on the viscosity of nano-confined liquids. Frequency modulation atomic force microscopy (FM-AFM) is a powerful technique that can detect variations in the conservative and dissipative forces between a nanometer-scale tip and a sample surface. We now present an accurate formula to convert the dissipation power of the cantilever measured during the experiment to damping of the tip-sample system. We demonstrated the conversion of the dissipation power versus tip-sample separation curve measured using a colloidal probe cantilever on a mica surface in water to the damping curve, which showed a good agreement with the theoretical curve. Moreover, we obtained the damping curve from the dissipation power curve measured on the hydration layers on the mica surface using a nanometer-scale tip, demonstrating that the formula allows us to quantitatively measure the viscosity of a nano-confined liquid using FM-AFM.

  16. 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.

  17. Exploring the tip-sample interaction regimes in the presence of hysteretic forces in the tapping mode atomic force microscopy

    Science.gov (United States)

    Korayem, M. H.; Eghbal, M. M.; Ebrahimi, N.

    2011-07-01

    In this article, the tip-sample interaction regimes in the presence of hysteretic forces are investigated using atomic force microscopy in the tapping mode. For this purpose, two samples that cause the formation of hysteretic forces, namely, silicon (stiff sample) with an adsorbed water film and polyethylene (compliant sample), are used. Also, for deriving the equation of motion of the microcantilever, the continuous beam model is used, and for determining the contact forces, depending on the sample under investigation, the Derjaguin-Muller-Toporov and Johnson-Kendall-Roberts contact mechanics models are used. The results indicate that the hysteretic interaction forces generate high-periodic and irregular responses at certain tip-sample separation distances. In fact, at these distances, a family of steady-state attractors is found that can be observed in one branch on the minimum tip-sample separation curves and in two separate branches on the average force curves. The reason for this occurrence might be the alternate formation of a liquid column between the probe tip and the sample (in the presence of ambient moisture), and for the compliant sample, the reason might be the alternate formation of an adhesion neck. In this article, the role of hysteretic forces in producing the hysteresis of the amplitude-separation curves is also explored.

  18. 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.

  19. Nano-rheology of hydrogels using direct drive force modulation atomic force microscopy.

    Science.gov (United States)

    Nalam, Prathima C; Gosvami, Nitya N; Caporizzo, Matthew A; Composto, Russell J; Carpick, Robert W

    2015-11-01

    We present a magnetic force-based direct drive modulation method to measure local nano-rheological properties of soft materials across a broad frequency range (10 Hz to 2 kHz) using colloid-attached atomic force microscope (AFM) probes in liquid. The direct drive method enables artefact-free measurements over several decades of excitation frequency, and avoids the need to evaluate medium-induced hydrodynamic drag effects. The method was applied to measure the local mechanical properties of polyacrylamide hydrogels. The frequency-dependent storage stiffness, loss stiffness, and loss tangent (tan δ) were quantified for hydrogels having high and low crosslinking densities by measuring the amplitude and the phase response of the cantilever while the colloid was in contact with the hydrogel. The frequency bandwidth was further expanded to lower effective frequencies (0.1 Hz to 10 Hz) by obtaining force-displacement (FD) curves. Slow FD measurements showed a recoverable but highly hysteretic response, with the contact mechanical behaviour dependent on the loading direction: approach curves showed Hertzian behaviour while retraction curves fit the JKR contact mechanics model well into the adhesive regime, after which multiple detachment instabilities occurred. Using small amplitude dynamic modulation to explore faster rates, the load dependence of the storage stiffness transitioned from Hertzian to a dynamic punch-type (constant contact area) model, indicating significant influence of material dissipation coupled with adhesion. Using the appropriate contact model across the full frequency range measured, the storage moduli were found to remain nearly constant until an increase began near ∼100 Hz. The softer gels' storage modulus increased from 7.9 ± 0.4 to 14.5 ± 2.1 kPa (∼85%), and the stiffer gels' storage modulus increased from 16.3 ± 1.1 to 31.7 ± 5.0 kPa (∼95%). This increase at high frequencies may be attributed to a contribution from solvent

  20. 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.

  1. 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.

  2. 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.

  3. Interpreting atomic force microscopy nanoindentation of hierarchical biological materials using multi-regime analysis.

    Science.gov (United States)

    Bonilla, M R; Stokes, J R; Gidley, M J; Yakubov, G E

    2015-02-01

    We present a novel Multi-Regime Analysis (MRA) routine for interpreting force indentation measurements of soft materials using atomic force microscopy. The MRA approach combines both well established and semi-empirical theories of contact mechanics within a single framework to deconvolute highly complex and non-linear force-indentation curves. The fundamental assumption in the present form of the model is that each structural contribution to the mechanical response acts in series with other 'mechanical resistors'. This simplification enables interpretation of the micromechanical properties of materials with hierarchical structures and it allows automated processing of large data sets, which is particularly indispensable for biological systems. We validate the algorithm by demonstrating for the first time that the elastic modulus of polydimethylsiloxane (PDMS) films is accurately predicted from both approach and retraction branches of force-indentation curves. For biological systems with complex hierarchical structures, we show the unique capability of MRA to map the micromechanics of live plant cells, revealing an intricate sequence of mechanical deformations resolved with precision that is unattainable using conventional methods of analysis. We recommend the routine use of MRA to interpret AFM force-indentation measurements for other complex soft materials including mammalian cells, bacteria and nanomaterials. PMID:25569139

  4. Individual globular domains and domain unfolding visualized in overstretched titin molecules with atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Zsolt Mártonfalvi

    Full Text Available Titin is a giant elastomeric protein responsible for the generation of passive muscle force. Mechanical force unfolds titin's globular domains, but the exact structure of the overstretched titin molecule is not known. Here we analyzed, by using high-resolution atomic force microscopy, the structure of titin molecules overstretched with receding meniscus. The axial contour of the molecules was interrupted by topographical gaps with a mean width of 27.7 nm that corresponds well to the length of an unfolded globular (immunoglobulin and fibronectin domain. The wide gap-width distribution suggests, however, that additional mechanisms such as partial domain unfolding and the unfolding of neighboring domain multimers may also be present. In the folded regions we resolved globules with an average spacing of 5.9 nm, which is consistent with a titin chain composed globular domains with extended interdomain linker regions. Topographical analysis allowed us to allocate the most distal unfolded titin region to the kinase domain, suggesting that this domain systematically unfolds when the molecule is exposed to overstretching forces. The observations support the prediction that upon the action of stretching forces the N-terminal ß-sheet of the titin kinase unfolds, thus exposing the enzyme's ATP-binding site and hence contributing to the molecule's mechanosensory function.

  5. 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

  6. Shape-dependent adhesion and friction of Au nanoparticles probed with atomic force microscopy

    International Nuclear Information System (INIS)

    The relation between surface structure and friction and adhesion is a long-standing question in tribology. Tuning the surface structure of the exposed facets of metal nanoparticles is enabled by shape control. We investigated the effect of the shape of Au nanoparticles on friction and adhesion. Two nanoparticle systems, cubic nanoparticles with a low-index (100) surface and hexoctahedral nanoparticles with a high-index (321) surface, were used as model nanoparticle surfaces. Atomic force microscopy was used to probe the nanoscale friction and adhesion on the nanoparticle surface. Before removing the capping layers, the friction results include contributions from both the geometric factor and the presence of capping layers. After removing the capping layers, we can see the exclusive effect of the surface atomic structure while the geometric effect is maintained. We found that after removing the capping layer, the cubic Au nanoparticles exhibited higher adhesion and friction, compared with cubes capped with layers covering 25% and 70%, respectively. On the other hand, the adhesion and friction of hexoctahedral Au nanoparticles decreased after removing the capping layers, compared with nanoparticles with capping layers. The difference in adhesion and friction forces between the bare Au surfaces and Au nanoparticles with capping layers cannot be explained by geometric factors, such as the slope of the nanoparticle surfaces. The higher adhesion and friction forces on cubic nanoparticles after removing the capping layers is associated with the atomic structure of (100) and (321) (i.e., the flat (100) surfaces of the cubic nanoparticles have a larger contact area, compared with the rough (321) surfaces of the hexoctahedral nanoparticles). This study implies an intrinsic relation between atomic structure and nanomechanical properties, with potential applications for controlling nanoscale friction and adhesion via colloid chemistry. (paper)

  7. 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.

  8. 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.

  9. Towards 3D charge localization by a method derived from atomic force microscopy: the electrostatic force distance curve

    Science.gov (United States)

    Villeneuve-Faure, C.; Boudou, L.; Makasheva, K.; Teyssedre, G.

    2014-11-01

    Charges injection and accumulation in the dielectric remains a critical issue, mainly because these phenomena are involved in a great number of failure mechanisms in cables or electronic components. Achieving a better understanding of the mechanisms leading to charge injection, transport and trapping under electrical stress and of the relevant interface phenomena is a high priority. The classical methods used for space charge density profile measurements have a limited spatial resolution, which prevents them being used for investigating thin dielectric layers or interface processes. Thus, techniques derived from atomic force microscopy (AFM) have been investigated more and more for this kind of application, but so far they have been limited by their lack of in-depth sensitivity. In this paper a new method for space charge probing is described, the electrostatic force distance curve (EFDC), which is based on electrostatic force measurements using AFM. A comparison with the results obtained using kelvin force microscopy (KFM) allowed us to highlight the fact that EFDC is sensitive to charges localized in the third-dimension.

  10. 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.

  11. 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

  12. 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

    2016-02-12

    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. PMID:26683826

  13. 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.

  14. 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.

    2016-06-01

    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.

  15. 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.

  16. 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

  17. A study of interaction forces at the solid-liquid interface using atomic force microscopy

    OpenAIRE

    Liu, Fei

    2016-01-01

    Solid-liquid interfaces are not only omnipresent in our daily lives, but also in many applications in industry and technology. However, our fundamental understanding of the physical properties of these interfaces is far from complete. In this thesis, we study properties, such as solvation forces, DLVO forces and electro-hydrodynamic dissipation of solid-liquid interfaces by the use of AFM. Thereby, we study various methods of AFM force spectroscopy, to find reliable and efficient measurements...

  18. Characterization of mitochondria isolated from normal and ischemic hearts in rats utilizing atomic force microscopy.

    Science.gov (United States)

    Lee, Gi-Ja; Chae, Su-Jin; Jeong, Jae Hoon; Lee, So-Ra; Ha, Sang-Jin; Pak, Youngmi Kim; Kim, Weon; Park, Hun-Kuk

    2011-04-01

    Mitochondria play critical roles in both the life and the death of cardiac myocytes. Various factors, such as the loss of ATP synthesis and increase of ATP hydrolysis, impairment in ionic homeostasis, formation of reactive oxygen species (ROS), and release of proapoptotic proteins are related to the generation of irreversible damage. It has been proposed that the release of cytochrome c is caused by a swelling of the mitochondrial matrix triggered by the apoptotic stimuli. However, there is a controversy about whether or not the mitochondria, indeed, swell during apoptosis. The major advantages of atomic force microscopy (AFM) over conventional optical and electron microscopes for bio-imaging include the fact that no special coating and vacuum are required and imaging can be done in all environments--air, vacuum or aqueous conditions. In addition, AFM force-distance curve measurements have become a fundamental tool in the fields of surface chemistry, biochemistry, and material science. In this study, we used AFM to observe the morphological and property changes in heart mitochondria that were isolated from a rat myocardial infarction model. From the shape parameters of the mitochondria in the AFM topographic image, it seemed that myocardial infarction caused the mitochondrial swelling. Also, the results of force-distance measurements showed that the adhesion force of heart mitochondria was significantly decreased by myocardial in infarction. Therefore, we suggested that myocardial infarction might be the cause of mitochondrial swelling and the changes in outer membrane of heart mitochondria. PMID:21050769

  19. 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. PMID:27115043

  20. 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.

  1. 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.

  2. 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.

  3. 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...

  4. Strain energy and lateral friction force distributions of carbon nanotubes manipulated into shapes by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Strus, Mark C; Lahiji, Roya R; Raman, Arvind; Reifenberger, Ron [Birck Nanotechnology Center, Purdue University, West Lafayette, IN (United States); Ares, Pablo [Nanotec Electronica, Madrid (Spain); Lopez, Vicente, E-mail: mark.strus@nist.go [Universidad Autonoma de Madrid, Madrid (Spain)

    2009-09-23

    The interplay between local mechanical strain energy and lateral frictional forces determines the shape of carbon nanotubes on substrates. In turn, because of its nanometer-size diameter, the shape of a carbon nanotube strongly influences its local electronic, chemical, and mechanical properties. Few, if any, methods exist for resolving the strain energy and static frictional forces along the length of a deformed nanotube supported on a substrate. We present a method using nonlinear elastic rod theory in which we compute the flexural strain energy and static frictional forces along the length of single walled carbon nanotubes (SWCNTs) manipulated into various shapes on a clean SiO{sub 2} substrate. Using only high resolution atomic force microscopy images of curved single walled nanotubes, we estimate flexural strain energy distributions on the order of attojoules per nanometer and the static frictional forces between a SWCNT and SiO{sub 2} surface to be a minimum of 230 pN nm{sup -1}.

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

    NARCIS (Netherlands)

    Gross, L.; Mohn, F.; Moll, N.; Liljeroth, P.; 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

  6. Probing living bacterial adhesion by single cell force spectroscopy using atomic force microscopy

    DEFF Research Database (Denmark)

    Zeng, Guanghong; Ogaki, Ryosuke; Regina, Viduthalai R.;

    ) coatings on titanium. We investigate the ability of a high density poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) coating to resist bacterial adhesion and biofilm formation from three clinically relevant bacteria: Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermis. The high...... density PLL-g-PEG coatings were about eight times as thick as the conventional PLL-g-PEG coatings. Adhesion forces toward high density PLL-g-PEG coatings were low (P. aeruginosa) or close to zero (S. aureus and S. epidermidis) compared to bare titanium surface. However, no decrease in adhesion force...... was observed for S. epidermidis toward conventional PLL-g-PEG coatings, whereas significantly lower adhesion forces were observed for S. aureus and P. aeruginosa. The adhesion force patterns were reflected by the colonization of bacteria after 48 h incubation of the coatings in bacterial cultures. The high...

  7. 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.

  8. 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.

  9. Single-molecule studies of DNA transcription using atomic force microscopy

    International Nuclear Information System (INIS)

    Atomic force microscopy (AFM) can detect single biomacromolecules with a high signal-to-noise ratio on atomically flat biocompatible support surfaces, such as mica. Contrast arises from the innate forces and therefore AFM does not require imaging contrast agents, leading to sample preparation that is relatively straightforward. The ability of AFM to operate in hydrated environments, including humid air and aqueous buffers, allows structure and function of biological and biomolecular systems to be retained. These traits of the AFM are ensuring that it is being increasingly used to study deoxyribonucleic acid (DNA) structure and DNA–protein interactions down to the secondary structure level. This report focuses in particular on reviewing the applications of AFM to the study of DNA transcription in reductionist single-molecule bottom-up approaches. The technique has allowed new insights into the interactions between ribonucleic acid (RNA) polymerase to be gained and enabled quantification of some aspects of the transcription process, such as promoter location, DNA wrapping and elongation. More recently, the trend is towards studying the interactions of more than one enzyme operating on a single DNA template. These methods begin to reveal the mechanics of gene expression at the single-molecule level and will enable us to gain greater understanding of how the genome is transcribed and translated into the proteome. (topical review)

  10. 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.

  11. 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

  12. Detection of atomic force microscopy cantilever displacement with a transmitted electron beam

    Science.gov (United States)

    Wagner, R.; Woehl, T. J.; Keller, R. R.; Killgore, J. P.

    2016-07-01

    The response time of an atomic force microscopy (AFM) cantilever can be decreased by reducing cantilever size; however, the fastest AFM cantilevers are currently nearing the smallest size that can be detected with the conventional optical lever approach. Here, we demonstrate an electron beam detection scheme for measuring AFM cantilever oscillations. The oscillating AFM tip is positioned perpendicular to and in the path of a stationary focused nanometer sized electron beam. As the tip oscillates, the thickness of the material under the electron beam changes, causing a fluctuation in the number of scattered transmitted electrons that are detected. We demonstrate detection of sub-nanometer vibration amplitudes with an electron beam, providing a pathway for dynamic AFM with cantilevers that are orders of magnitude smaller and faster than the current state of the art.

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

    Science.gov (United States)

    Cai, Jiandong; Wang, Michael Yu; Zhang, Li

    2015-12-01

    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. PMID:26724066

  14. 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.

  15. 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.

  16. 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.

  17. Analysis of the coagulation of human blood cells on diamond surfaces by atomic force microscopy

    Science.gov (United States)

    Baranauskas, V.; Fontana, M.; Guo, Zhao Jing; Ceragioli, H. J.; Peterlevitz, A. C.

    2004-11-01

    Atomic force microscopy (AFM) was used to study the morphology and coagulation of human blood cells in contact with solid surfaces. Blood was extracted from the veins of healthy adult donors and the samples were used immediately after extraction, deposited either on borosilicate glass or diamond substrates. Some blood samples were anti-coagulated by adding heparin for single cell AFM imaging. No chemicals were used for attaching or immobilizing the cells. The diamond substrates were produced by chemical vapour deposition (CVD diamond) using a hot-filament CVD system fed with ethanol highly diluted in hydrogen. AFM imaging of isolated cells (anti-coagulated by heparin) was only possible on the glass substrates due to the lack of adherence of the cells to the diamond surface. The coagulation results suggest that blood clotting on diamond produces a less rough surface than blood clotting on glass.

  18. PTCDA molecules on an InSb(001) surface studied with atomic force microscopy

    International Nuclear Information System (INIS)

    PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) molecular structures assembled on an InSb(001) c(8 x 2) reconstructed surface have been studied using frequency modulated atomic force microscopy. The high-resolution imaging of the structures is possible through repulsive interactions, using the constant height scanning mode. During initial stages of growth the [110] diffusion channel dominates as indicated by formation of long PTCDA molecular chains parallel to the [110] crystallographic direction on the InSb surface. For a single monolayer coverage a wetting layer of PTCDA is formed. Finally it is shown that the PTCDA/InSb is a promising system for building molecular nanostructures by manipulation of single molecules with the AFM tip

  19. A Fabrication Technique for Nano-gap Electrodes by Atomic Force Microscopy Nano lithography

    International Nuclear Information System (INIS)

    A simple technique is introduced for fabrication of nano-gap electrodes by using nano-oxidation atomic force microscopy (AFM) lithography with a Cr/ Pt coated silicon tip. AFM local anodic oxidation was performed on silicon-on-insulator (SOI) surfaces by optimization of desired conditions to control process in contact mode. Silicon electrodes with gaps of sub 31 nm were fabricated by nano-oxidation method. This technique which is simple, controllable, inexpensive and fast is capable of fabricating nano-gap structures. The current-voltage measurements (I-V) of the electrodes demonstrated very good insulating characteristics. The results show that silicon electrodes have a great potential for fabrication of single molecule transistors (SMT), single electron transistors (SET) and the other nano electronic devices. (author)

  20. Current status and perspectives in atomic force microscopy-based identification of cellular transformation

    Science.gov (United States)

    Dong, Chenbo; Hu, Xiao; Dinu, Cerasela Zoica

    2016-01-01

    Understanding the complex interplay between cells and their biomechanics and how the interplay is influenced by the extracellular microenvironment, as well as how the transforming potential of a tissue from a benign to a cancerous one is related to the dynamics of both the cell and its surroundings, holds promise for the development of targeted translational therapies. This review provides a comprehensive overview of atomic force microscopy-based technology and its applications for identification of cellular progression to a cancerous phenotype. The review also offers insights into the advancements that are required for the next user-controlled tool to allow for the identification of early cell transformation and thus potentially lead to improved therapeutic outcomes. PMID:27274238

  1. 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.

  2. 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.

  3. 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.

  4. Electron Spin Resonance and Atomic Force Microscopy Study on Gadolinium Doped Ceria

    Directory of Open Access Journals (Sweden)

    Cesare Oliva

    2015-01-01

    Full Text Available A combined electron spin resonance (ESR and atomic force microscopy (AFM study on Ce1−xGdxO2−x/2 samples is here presented, aimed at investigating the evolution of the ESR spectral shape as a function of x in a wide composition range. At low x=0.02, the spectrum is composed of features at geff≈2; 2.8; 6. With increasing x, this pattern merges into a single geff≈2 broad ESR curve, which assumes a Dysonian-shaped profile at x≥0.5, whereas, at these x values, AFM measurements show an increasing surface roughness. It is suggested that the last could cause the formation of surface polaritons at the origin of the particular ESR spectral profile observed at these high Gd doping levels.

  5. 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.

  6. Characterization of single-crystal sapphire substrates by X-ray methods and atomic force microscopy

    International Nuclear Information System (INIS)

    The possibility of characterizing a number of practically important parameters of sapphire substrates by X-ray methods is substantiated. These parameters include wafer bending, traces of an incompletely removed damaged layer that formed as a result of mechanical treatment (scratches and marks), surface roughness, damaged layer thickness, and the specific features of the substrate real structure. The features of the real structure of single-crystal sapphire substrates were investigated by nondestructive methods of double-crystal X-ray diffraction and plane-wave X-ray topography. The surface relief of the substrates was investigated by atomic force microscopy and X-ray scattering. The use of supplementing analytical methods yields the most complete information about the structural inhomogeneities and state of crystal surface, which is extremely important for optimizing the technology of substrate preparation for epitaxy.

  7. Advanced tip design for liquid phase vibration mode atomic force microscopy

    International Nuclear Information System (INIS)

    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 μm. 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

  8. 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.

  9. Surface morphology of sputter deposited W-Si-N composite coatings characterized by atomic force microscopy

    International Nuclear Information System (INIS)

    Tungsten-silicon-nitride (W-Si-N) composite coatings on Si(100) substrates were sputter deposited at various silicon target currents, and their surface morphology was studied with scaling analysis and fractal analysis based on atomic force microscopy (AFM). The root-mean-square (rms) roughness σ, roughness exponent α, the correlation length ξ and the average magnitude of the lateral surface slope ρ decrease with the silicon target current, which is caused by the impeding effect of amorphous Si3N4 on the grain growth of W2N and W5Si3. The competition of surface diffusion and shadowing effect together with other processes drives the formation of columnar grains with mould-like tops. The fractal dimensions obtained using power spectrum method and the R/S method are 2.16 ± 0.04 and 2.15 ± 0.01, respectively, and they both increase with the silicon target current

  10. Observations of xenon gas-treated barley cells in solution by atomic force microscopy.

    Science.gov (United States)

    Yoshino, T; Sotome, I; Ohtani, T; Isobe, S; Oshita, S; Maekawa, T

    2000-01-01

    Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution. PMID:11108038

  11. 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...

  12. 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 ...

  13. Advanced tip design for liquid phase vibration mode atomic force microscopy.

    Science.gov (United States)

    Muramatsu, Hiroshi; Yamamoto, Yuji; Shigeno, Masatsugu; Shirakawabe, Yoshiharu; Inoue, Akira; Kim, Woo-Sik; Kim, Seung Jin; Chang, Sang-Mok; Kim, Jong Min

    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 microm. 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. PMID:18328326

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

    International Nuclear Information System (INIS)

    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 y0c, at which the liquid film jumps to contact the AFM tip. It is found that there are three distinct regimes in the variation of y0c 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 film 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. (condensed matter: structure, mechanical and thermal properties)

  15. 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.

  16. Measuring the loss tangent of polymer materials with atomic force microscopy based methods

    International Nuclear Information System (INIS)

    Atomic force microscopy (AFM) quantitatively maps viscoelastic parameters of polymers on the nanoscale by several methods. The loss tangent, the ratio between dissipated and stored energy, was measured on a blend of thermoplastic polymer materials by a dynamic contact method, contact resonance, and by a recently developed loss tangent measurement by amplitude modulation AFM. Contact resonance measurements were performed both with dual AC resonance tracking and band excitation (BE), allowing for a reference-free measurement of the loss tangent. Amplitude modulation AFM was performed where a recent interpretation of the phase signal under certain operating conditions allows for the loss tangent to be calculated. The loss tangent measurements were compared with values expected from time–temperature superposed frequency-dependent dynamical mechanical curves of materials and reveal that the loss tangents determined from the BE contact resonance method provide the most accurate values. (paper)

  17. Multi-frequency tapping-mode atomic force microscopy beyond three eigenmodes in ambient air

    Directory of Open Access Journals (Sweden)

    Santiago D. Solares

    2014-09-01

    Full Text Available We present an exploratory study of multimodal tapping-mode atomic force microscopy driving more than three cantilever eigenmodes. We present tetramodal (4-eigenmode imaging experiments conducted on a thin polytetrafluoroethylene (PTFE film and computational simulations of pentamodal (5-eigenmode cantilever dynamics and spectroscopy, focusing on the case of large amplitude ratios between the fundamental eigenmode and the higher eigenmodes. We discuss the dynamic complexities of the tip response in time and frequency space, as well as the average amplitude and phase response. We also illustrate typical images and spectroscopy curves and provide a very brief description of the observed contrast. Overall, our findings are promising in that they help to open the door to increasing sophistication and greater versatility in multi-frequency AFM through the incorporation of a larger number of driven eigenmodes, and in highlighting specific future research opportunities.

  18. 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.

  19. Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

    International Nuclear Information System (INIS)

    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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Daniell method for power spectral density estimation in atomic force microscopy.

    Science.gov (United States)

    Labuda, Aleksander

    2016-03-01

    An alternative method for power spectral density (PSD) estimation--the Daniell method--is revisited and compared to the most prevalent method used in the field of atomic force microscopy for quantifying cantilever thermal motion--the Bartlett method. Both methods are shown to underestimate the Q factor of a simple harmonic oscillator (SHO) by a predictable, and therefore correctable, amount in the absence of spurious deterministic noise sources. However, the Bartlett method is much more prone to spectral leakage which can obscure the thermal spectrum in the presence of deterministic noise. By the significant reduction in spectral leakage, the Daniell method leads to a more accurate representation of the true PSD and enables clear identification and rejection of deterministic noise peaks. This benefit is especially valuable for the development of automated PSD fitting algorithms for robust and accurate estimation of SHO parameters from a thermal spectrum. PMID:27036781

  6. 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

  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. Submolecular Imaging by Noncontact Atomic Force Microscopy with an Oxygen Atom Rigidly Connected to a Metallic Probe.

    Science.gov (United States)

    Mönig, Harry; Hermoso, Diego R; Díaz Arado, Oscar; Todorović, Milica; Timmer, Alexander; Schüer, Simon; Langewisch, Gernot; Pérez, Rubén; Fuchs, Harald

    2016-01-26

    In scanning probe microscopy, the imaging characteristics in the various interaction channels crucially depend on the chemical termination of the probe tip. Here we analyze the contrast signatures of an oxygen-terminated copper tip with a tetrahedral configuration of the covalently bound terminal O atom. Supported by first-principles calculations we show how this tip termination can be identified by contrast analysis in noncontact atomic force and scanning tunneling microscopy (NC-AFM, STM) on a partially oxidized Cu(110) surface. After controlled tip functionalization by soft indentations of only a few angstroms in an oxide nanodomain, we demonstrate that this tip allows imaging an organic molecule adsorbed on Cu(110) by constant-height NC-AFM in the repulsive force regime, revealing its internal bond structure. In established tip functionalization approaches where, for example, CO or Xe is deliberately picked up from a surface, these probe particles are only weakly bound to the metallic tip, leading to lateral deflections during scanning. Therefore, the contrast mechanism is subject to image distortions, artifacts, and related controversies. In contrast, our simulations for the O-terminated Cu tip show that lateral deflections of the terminating O atom are negligible. This allows a detailed discussion of the fundamental imaging mechanisms in high-resolution NC-AFM experiments. With its structural rigidity, its chemically passivated state, and a high electron density at the apex, we identify the main characteristics of the O-terminated Cu tip, making it a highly attractive complementary probe for the characterization of organic nanostructures on surfaces. PMID:26605698

  9. 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...

  10. 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.

  11. A study of interaction forces at the solid-liquid interface using atomic force microscopy

    NARCIS (Netherlands)

    Liu, Fei

    2016-01-01

    Solid-liquid interfaces are not only omnipresent in our daily lives, but also in many applications in industry and technology. However, our fundamental understanding of the physical properties of these interfaces is far from complete. In this thesis, we study properties, such as solvation forces, DL

  12. 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 ...

  13. Tip localization of an atomic force microscope in transmission microscopy with nanoscale precision

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, Fabian; Pippig, Diana A., E-mail: diana.pippig@physik.uni-muenchen.de; Gaub, Hermann E. [Center for Nanoscience and Department of Physics, University of Munich, Amalienstraße 54, 80799 Munich (Germany); Heucke, Stephan F. [Center for Integrated Protein Science Munich (CIPSM), University of Munich, Butenandtstraße 5-13, 81377 Munich (Germany)

    2015-03-15

    Since the atomic force microscope (AFM) has evolved into a general purpose platform for mechanical experiments at the nanoscale, the need for a simple and generally applicable localization of the AFM cantilever in the reference frame of an optical microscope has grown. Molecular manipulations like in single molecule cut and paste or force spectroscopy as well as tip mediated nanolithography are prominent examples for the broad variety of applications implemented to date. In contrast to the different kinds of superresolution microscopy where fluorescence is used to localize the emitter, we, here, employ the absorbance of the tip to localize its position in transmission microscopy. We show that in a low aperture illumination, the tip causes a significant reduction of the intensity in the image plane of the microscope objective when it is closer than a few hundred nm. By independently varying the z-position of the sample slide, we could verify that this diffraction limited image of the tip is not caused by a near field effect but is rather caused by the absorbance of the transmitted light in the low apex needle-like tip. We localized the centroid position of this tip image with a precision of better than 6 nm and used it in a feedback loop to position the tip into nano-apertures of 110 nm radius. Single-molecule force spectroscopy traces on the unfolding of individual green fluorescent proteins within the nano-apertures showed that their center positions were repeatedly approached with very high fidelity leaving the specific handle chemistry on the tip’s surface unimpaired.

  14. Statistical Analysis of Long- and Short-Range Forces Involved in Bacterial Adhesion to Substratum Surfaces as Measured Using Atomic Force Microscopy

    OpenAIRE

    CHEN, YUN; Henk J Busscher; van der Mei, Henny C.; Norde, Willem

    2011-01-01

    Surface thermodynamic analyses of microbial adhesion using measured contact angles on solid substrata and microbial cell surfaces are widely employed to determine the nature of the adhesion forces, i.e., the interplay between Lifshitz-van der Waals and acid-base forces. While surface thermodynamic analyses are often viewed critically, atomic force microscopy (AFM) can also provide information on the nature of the adhesion forces by means of Poisson analysis of the measured forces. This review...

  15. Long-tip high-speed atomic force microscopy for nanometer-scale imaging in live cells

    Science.gov (United States)

    Shibata, Mikihiro; Uchihashi, Takayuki; Ando, Toshio; Yasuda, Ryohei

    2015-03-01

    Visualization of morphological dynamics of live cells with nanometer resolution under physiological conditions is highly desired, but challenging. It has been demonstrated that high-speed atomic force microscopy is a powerful technique for visualizing dynamics of biomolecules under physiological conditions. However, application of high-speed atomic force microscopy for imaging larger objects such as live mammalian cells has been complicated because of the collision between the cantilever and samples. Here, we demonstrate that attaching an extremely long (~3 μm) and thin (~5 nm) tip by amorphous carbon to the cantilever allows us to image the surface structure of live cells with the spatiotemporal resolution of nanometers and seconds. We demonstrate that long-tip high-speed atomic force microscopy is capable of imaging morphogenesis of filopodia, membrane ruffles, pit formation, and endocytosis in COS-7, HeLa cells and hippocampal neurons.

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

    Energy Technology Data Exchange (ETDEWEB)

    Marinello, Francesco, E-mail: francesco.marinello@unipd.it; Pezzuolo, Andrea; Sartori, Luigi; Cavalli, Raffaele [University of Padova, Department of Land, Environment, Agriculture and Forestry, Viale dell’Università 16, 35020 Legnaro, Padova (Italy); Carmignato, Simone [University of Padova, Department of Management and Engineering, Stradella San Nicola 3, 36100 Vicenza (Italy); Savio, Enrico [University of Padova, Department of Industrial Engineering, Via Venezia 1, 35131 Padova (Italy); De Chiffre, Leonardo [Technical University of Denmark, Department of Mechanical Engineering, Produktionstorvet 425, 2800 Kgs. Lyngby (Denmark)

    2015-06-23

    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. To this regard, some open issues are of particular interest: low depth of penetration, high lateral resolution and measurements at elevated temperatures. An interesting solution is given by acoustic microscopy techniques, which can be successfully implemented for advanced research in surface elasticity, allowing 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 during scanning, in order to allow exploitation of high resolution measurements at relatively high temperatures. Such instrument set up was undergone a set of calibration experiments in order to allow not only qualitative but also quantitative characterization of surfaces. The work was completed with a feasibility study with mechanical and topography measurements at temperatures as high as 150°C, with lateral resolution lower than 100 nm.

  17. 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.

  18. 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.

  19. Atomic force microscopy of collagen structure in bone and dentine revealed by osteoclastic resorption

    International Nuclear Information System (INIS)

    Mineralised tissues such as bone consist of two material phases: collagen protein fibrils, secreted by osteoblasts, form model structures for subsequent deposition of mineral, calcium hydroxyapatite. Collagen and mineral are removed in a three-dimensional manner by osteoclasts during bone turnover in skeletal growth or repair. Bone active drugs have recently been developed for skeletal diseases, and there is revived interest in changes in the structure of mineralised tissues seen in disease and upon treatment. The resolution of atomic force microscopy and use of unmodified samples has enabled us to image bone and dentine collagen exposed by the natural process of cellular dissolution of mineralised matrix. The morphology of bone and dentine has been analysed when fully mineralised and after osteoclast-mediated bone resorption, and compared with results from other microscopy techniques. Banded type I collagen, with 66.5±1.4 nm axial D-periodicity and 62.2±7.0 nm diameter, has been identified within resorption lacunae in bone and 69.4±4.3 nm axial D-periodicity and 140.6±12.4 nm diameter in dentine substrates formed by human and rabbit osteoclasts, respectively. This observation suggests a route by which the material and morphological properties of bone collagen can be analysed in situ, compared with collagen from non-skeletal sites, and contrasted in diseases of medical importance, such as osteoporosis, where skeletal tissue is mechanically weakened

  20. A New Method for Characterization of Natural Zeolites and Organic Nanostructure Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Domenico Fuoco

    2012-03-01

    Full Text Available In order to study and develop an economical solution to environmental pollution in water, a wide variety of materials have been investigated. Natural zeolites emerge from that research as the best in class of this category. Zeolites are natural materials which are relatively abundant and non biodegradable, economical and serve to perform processes of environmental remediation. This paper contains a full description of a new method to characterize the superficial properties of natural zeolites of exotic provenience (Caribbean Islets with atomic force microscopy (AFM. AFM works with the simplicity of the optical microscope and the high resolution typical of a transmission electron microscope (TEM. If the sample is conductive, structural information of mesoporous material is obtained using scanning and transmission electron microscopy (SEM and TEM, otherwise the sample has to be processed through the grafitation technique, but this procedure induces errors of topography. Therefore, the existing AFM method, to observe zeolite powders, is made in a liquid cell-head scanner. This work confirms that it is possible to use an ambient air-head scanner to obtain a new kind of microtopography. Once optimized, this new method will allow investigation of organic micelles, a very soft nanostructure of cetyltriammonium bromide (CTAB, upon an inorganic surface such as natural zeolites. The data also demonstrated some correlation between SEM microphotographies and AFM 3D images.

  1. Short unligated sticky ends enable the observation of circularised DNA by atomic force and electron microscopies.

    Science.gov (United States)

    Révet, B; Fourcade, A

    1998-05-01

    A comparative study of the stabilisation of DNA sticky ends by divalent cations was carried out by atomic force microscopy (AFM), electron microscopy and agarose gel electrophoresis. At room temperature, molecules bearing such extremities are immediately oligomerised or circularised by addition of Mg2+or Ca2+. This phenomenon, more clearly detected by AFM, requires the presence of uranyl salt, which stabilises the structures induced by Mg2+or Ca2+. DNA fragments were obtained by restriction enzymes producing sticky ends of 2 or 4 nucleotides (nt) in length with different guanine plus cytosine (GC) contents. The stability of the pairing is high when ends of 4 nt display a 100% GC-content. In that case, 95% of DNA fragments are maintained circular by the divalent cations, although 2 nt GC-sticky ends are sufficient for a stable pairing. DNA fragments with one blunt end and the other sticky appear as dimers in the presence of Mg2+. Dimerisation was analysed by varying the lengths and concentrations of DNA fragments, the base composition of the sticky ends, and also the temperature. Our observation provides a new powerful tool for construction of inverted dimers, and circularisation, ligation analysis or short bases sequence interaction studies. PMID:9547265

  2. Nanostructure of native pectin sugar acid gels visualized by atomic force microscopy.

    Science.gov (United States)

    Fishman, Marshall L; Cooke, Peter H; Coffin, David R

    2004-01-01

    Height and phase shift images of high methoxyl sugar acid gels (HMSAG) of pectin were obtained by atomic force microscopy in the tapping mode. Images revealed that pores in these gels were fluid and flattened out when measured as a function of time. These images revealed for the first time the structure of adsorbed sugar on pectin in the hydrated native gels and how the pectin framework is organized within these gels. Segmentation of images revealed that the underlying pectin framework contained combinations of rods, segmented rods, and kinked rods connected end to end and laterally. The open network of strands was similar to pectin aggregates from 5 mM NaCl solution imaged earlier by electron microscopy (Fishman et al., Arch. Biochem. Biophys. 1992, 294, 253). Area measurements revealed that the ratio of bound sugar to pectin was in excess of 100 to 1 (w/w). Furthermore, images indicated relatively small differences in the organization of native commercial citrus pectin, orange albedo pectin, and lime albedo pectin gels at optimal pH as determined in this study. The findings are consistent with earlier gel strength measurements of these gels. In addition, values of gel strength were consistent with values of molar mass and viscosity of the constituent pectins in that they increased in the same order. Finally, we demonstrated the advantage of simultaneous visualization of height and phase shift images for observing and quantitating the nanostructure of relatively soft gels which are fully hydrated with a buffer. PMID:15002992

  3. Probing the mechanical properties of TNF-α stimulated endothelial cell with atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Sei-Young Lee

    2011-01-01

    Full Text Available Sei-Young Lee1,2, Ana-Maria Zaske3, Tommaso Novellino1,4*, Delia Danila3, Mauro Ferrari1,5*, Jodie Conyers3, Paolo Decuzzi1,6*1Department of Nanomedicine and Biomedical Engineering, The University of Texas Medical School at Houston, Houston, TX, USA; 2Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, USA; 3CeTIR – Center for Translational Injury Research, The University of Texas Health Science Center at Houston, Houston, TX, USA; 4Department of Biomedical Engineering, Biomedical Campus University of Rome, Italy; 5MD Anderson Cancer Center, Houston, TX, USA; 6BioNEM – Center of Bio-Nanotechnology and Engineering for Medicine, University of Magna Graecia, Catanzaro, Italy; *Currently at Department of Nanomedicine and Biomedical Engineering, The Methodist Hospital Research Institute, Houston, TX, USAAbstract: TNF-α (tumor necrosis factor-α is a potent pro-inflammatory cytokine that regulates the permeability of blood and lymphatic vessels. The plasma concentration of TNF-α is elevated (> 1 pg/mL in several pathologies, including rheumatoid arthritis, atherosclerosis, cancer, pre-eclampsia; in obese individuals; and in trauma patients. To test whether circulating TNF-α could induce similar alterations in different districts along the vascular system, three endothelial cell lines, namely HUVEC, HPMEC, and HCAEC, were characterized in terms of 1 mechanical properties, employing atomic force microscopy; 2 cytoskeletal organization, through fluorescence microscopy; and 3 membrane overexpression of adhesion molecules, employing ELISA and immunostaining. Upon stimulation with TNF-α (10 ng/mL for 20 h, for all three endothelial cells, the mechanical stiffness increased by about 50% with a mean apparent elastic modulus of E ~5 ± 0.5 kPa (~3.3 ± 0.35 kPa for the control cells; the density of F-actin filaments increased in the apical and median planes; and the ICAM-1 receptors were overexpressed compared with

  4. Optimization of adhesion mode atomic force microscopy resolves individual molecules in topography and adhesion

    NARCIS (Netherlands)

    Willemsen, O.H.; Snel, M.M.E.; Noort, van S.J.T.; Werf, van der K.O.; Grooth, de B.G.; Figdor, C.G.; Greve, J.

    1999-01-01

    The force sensor of an atomic force microscope (AFM) is sensitive enough to measure single molecular binding strengths by means of a force–distance curve. In order to combine high-force sensitivity with the spatial resolution of an AFM in topography mode, adhesion mode has been developed. Since this

  5. [Preliminary application of atomic force microscopy on identification of native habitat of Chinese medicine decoction pieces].

    Science.gov (United States)

    Jiao, Ligong; Liu, Jing; Chen, Hao; Liao, Fulong; Han, Dong

    2012-04-01

    Identification of the native habitat of Chinese medicine decoction pieces plays an important role in the use of Chinese Heber medicine. However, the traditional method always based on subjective description, lack of quantitative information. In this study, nanomechanical analysis of Ophiopogonis Radix, Polygonati Odorati Rhizoma and Curcumae Aromaticae Radix coming from different districts was carried out by using the force-distance curve of atomic force microscopy (AFM), including stiffness (represented by the slope of the force curve) and adhesion work (calculated via the adhesion area of the retrace line in force-distance curve). The results showed that the Ophiopogonis Radix from Sichuan province (slope 0.03 +/- 0.001) was significantly stiffer but less sticky [adhesion work 393.98 +/- 49.21 x 10(-10)) J] in comparison with that from Hubei province [slope 0.018 +/- 0.001, adhesion work (985.67 +/- 91.61) x 10(-10) J]; the Polygonati Odorati Rhizoma Hunan province was stiffer (slope 0.03 +/- 0.002) and stickier [adhesion work (413.67 +/- 92.58) x10(-10) J] than that from Dongbei province [slope 0.019 +/- 0.002, adhesion work (27.37 +/- 11.05) x 10(-10) J]; the Curcumae Aromaticae Radix from Sichuan province was also stiffer (slope 0.019 +/- 0.0017) but less stickier [adhesion work (1179.79 +/- 225.05) x 10(-10) J] than that from Hubei province [slope 0.013 +/- 0.0006, adhesion work (2831.27 +/- 93.71) x 10(-10)]. It is indicated that changes in mechanical properties of Chinese medicine decoction pieces correlate well with their origin. This method may provide quantitative information for the identification of the native habitat of Chinese medicine decoction pieces. PMID:22779365

  6. Spring constants and adhesive properties of native bacterial biofilm cells measured by atomic force microscopy.

    Science.gov (United States)

    Volle, C B; Ferguson, M A; Aidala, K E; Spain, E M; Núñez, M E

    2008-11-15

    Bacterial biofilms were imaged by atomic force microscopy (AFM), and their elasticity and adhesion to the AFM tip were determined from a series of tip extension and retraction cycles. Though the five bacterial strains studied included both Gram-negative and -positive bacteria and both environmental and laboratory strains, all formed simple biofilms on glass surfaces. Cellular spring constants, determined from the extension portion of the force cycle, varied between 0.16+/-0.01 and 0.41+/-0.01 N/m, where larger spring constants were measured for Gram-positive cells than for Gram-negative cells. The nonlinear regime in the extension curve depended upon the biomolecules on the cell surface: the extension curves for the smooth Gram-negative bacterial strains with the longest lipopolysaccharides on their surface had a larger nonlinear region than the rough bacterial strain with shorter lipopolysaccharides on the surface. Adhesive forces between the retracting silicon nitride tip and the cells varied between cell types in terms of the force components, the distance components, and the number of adhesion events. The Gram-negative cells' adhesion to the tip showed the longest distance components, sometimes more than 1 microm, whereas the shortest distance adhesion events were measured between the two Gram-positive cell types and the tip. Fixation of free-swimming planktonic cells by NHS and EDC perturbed both the elasticity and the adhesive properties of the cells. Here we consider the biochemical meaning of the measured physical properties of simple biofilms and implications to the colonization of surfaces in the first stages of biofilm formation. PMID:18815013

  7. 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

    2016-08-01

    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. PMID:27404764

  8. Localizing chemical groups while imaging single native proteins by high-resolution atomic force microscopy.

    Science.gov (United States)

    Pfreundschuh, Moritz; Alsteens, David; Hilbert, Manuel; Steinmetz, Michel O; Müller, Daniel J

    2014-05-14

    Simultaneous high-resolution imaging and localization of chemical interaction sites on single native proteins is a pertinent biophysical, biochemical, and nanotechnological challenge. Such structural mapping and characterization of binding sites is of importance in understanding how proteins interact with their environment and in manipulating such interactions in a plethora of biotechnological applications. Thus far, this challenge remains to be tackled. Here, we introduce force-distance curve-based atomic force microscopy (FD-based AFM) for the high-resolution imaging of SAS-6, a protein that self-assembles into cartwheel-like structures. Using functionalized AFM tips bearing Ni(2+)-N-nitrilotriacetate groups, we locate specific interaction sites on SAS-6 at nanometer resolution and quantify the binding strength of the Ni(2+)-NTA groups to histidine residues. The FD-based AFM approach can readily be applied to image any other native protein and to locate and structurally map histidine residues. Moreover, the surface chemistry used to functionalize the AFM tip can be modified to map other chemical interaction sites. PMID:24766578

  9. 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.

  10. 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.

  11. Fast Stiffness Mapping of Cells Using High-Bandwidth Atomic Force Microscopy.

    Science.gov (United States)

    Wang, Andrew; Vijayraghavan, Karthik; Solgaard, Olav; Butte, Manish J

    2016-01-26

    The cytoskeleton controls cellular morphology and mediates the mechanical interactions between a cell and its environment. Atomic force microscopy (AFM) has the unique capability to map cytoskeletal mechanics and structures with nanometer resolution. However, whole-cell cytomechanical imaging with conventional AFM techniques is limited by low imaging speed. Here, we present fast nanomechanical mapping of cells using high-bandwidth AFM (HB-AFM), where >10(6) nanoindentation measurements were acquired in ∼10 min-a task that would take weeks to finish using conventional AFM. High-bandwidth measurements enabled capture of the entire tip-sample interaction for each tap on cells, engendering a new measurement ("force phase") that exceeds the contrast of conventional tapping mode and enabling spectral visualization of >10 harmonics. The abundance of measurements allowed discovery of subtle cytomechanical features, including the stiffness of fibers of the cellular spectrin network in situ. This approach bridges HB-AFM and high-harmonic imaging and opens future opportunities for measuring the dynamic mechanical properties of living cells. PMID:26554581

  12. 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.

  13. 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.

  14. 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.

  15. RAPID COMMUNICATION: Frequency and force modulation atomic force microscopy: low-impact tapping-mode imaging without bistability

    Science.gov (United States)

    Solares, Santiago D.

    2007-07-01

    Since the 1980s, atomic force microscopy (AFM) has rapidly developed into a versatile, high-resolution characterization technique, available in a variety of imaging modes. Within intermittent-contact tapping-mode, imaging bistability and sample mechanical damage continue to be two of the most important challenges faced daily by AFM users. Recently, a new double-control-loop tapping-mode imaging algorithm (frequency and amplitude modulation AFM, FAM-AFM) was proposed and evaluated within numerical simulations, demonstrating a reduction in the repulsive tip sample forces and the absence of bistability. This article presents a much simpler algorithm, frequency and force modulation AFM (FFM-AFM), which requires only a single control loop and offers the same benefits as FAM-AFM. The concept is applied to calculate the cross-sectional scan of a carbon nanotube sample resting on a silicon surface, which is then compared to a previously reported image obtained in conventional amplitude-modulation tapping-mode, shown to be in agreement with the experimental result.

  16. Probing the nanoadhesion of Streptococcus sanguinis to titanium implant surfaces by atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Aguayo S

    2016-04-01

    Full Text Available Sebastian Aguayo,1 Nikolaos Donos,2 Dave Spratt,3 Laurent Bozec11Department of Biomaterials and Tissue Engineering, 2Periodontology Unit, 3Division of Microbial Diseases, UCL Eastman Dental Institute, University College London, London, UKAbstract: As titanium (Ti continues to be utilized in great extent for the fabrication of artificial implants, it is important to understand the crucial bacterium–Ti interaction occurring during the initial phases of biofilm formation. By employing a single-cell force spectroscopy technique, the nanoadhesive interactions between the early-colonizing Streptococcus sanguinis and a clinically analogous smooth Ti substrate were explored. Mean adhesion forces between S. sanguinis and Ti were found to be 0.32±0.00, 1.07±0.06, and 4.85±0.56 nN for 0, 1, and 60 seconds contact times, respectively; while adhesion work values were reported at 19.28±2.38, 104.60±7.02, and 1,317.26±197.69 aJ for 0, 1, and 60 seconds, respectively. At 60 seconds surface delays, minor-rupture events were modeled with the worm-like chain model yielding an average contour length of 668±12 nm. The mean force for S. sanguinis minor-detachment events was 1.84±0.64 nN, and Poisson analysis decoupled this value into a short-range force component of -1.60±0.34 nN and a long-range force component of -0.55±0.47 nN. Furthermore, a solution of 2 mg/mL chlorhexidine was found to increase adhesion between the bacterial probe and substrate. Overall, single-cell force spectroscopy of living S. sanguinis cells proved to be a reliable way to characterize early-bacterial adhesion onto machined Ti implant surfaces at the nanoscale.Keywords: atomic force microscopy, biophysics, bacterial adhesion, dental implants, titanium

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Investigating the adsorption of the gemini surfactant "12-2-12" onto mica using atomic force microscopy and surface force apparatus measurements

    NARCIS (Netherlands)

    Fielden, ML; Claesson, PM; Verrall, RE

    1999-01-01

    The adsorption of the cationic gemini surfactant 1,2-bis(n-dodecyldimethylammonium)ethane dibromide on mica was followed by measuring forces between mica surfaces and by atomic force microscopy (AFM) imaging. The surface charge was found to be neutralized at total surfactant concentrations between 8

  2. Quantitative Assessment of Friction Characteristics of Single-Layer MoS2 and Graphene Using Atomic Force Microscopy.

    Science.gov (United States)

    Khac, Bien-cuong tran; Chung, Koo-hyun

    2016-05-01

    Atomically thin layered materials such as MoS2 and graphene have attracted a lot of interest as protective coating layers for micro- and nano-electromechanical devices based on their superior mechanical properties and chemical inertness. In this work, the frictional characteristics of single layer MoS2 and graphene prepared by the mechanical exfoliation method were quantitatively investigated using atomic force microscopy. The results showed that both MoS2 and graphene exhibited relatively low friction forces of 1-3 nN under normal forces ranging from 1 to 30 nN. However, a higher increase in the friction force as the normal force increased was observed in the case of MoS2. The differences in the adhesion characteristics and mechanical properties of atomically thin layered materials may influence the puckering of the layer, which in turn influences the frictional behavior. PMID:27483768

  3. Relating the physical properties of Pseudomonas aeruginosa lipopolysaccharides to virulence by atomic force microscopy.

    Science.gov (United States)

    Ivanov, Ivan E; Kintz, Erica N; Porter, Laura A; Goldberg, Joanna B; Burnham, Nancy A; Camesano, Terri A

    2011-03-01

    Lipopolysaccharides (LPS) are an important class of macromolecules that are components of the outer membrane of Gram-negative bacteria such as Pseudomonas aeruginosa. P. aeruginosa contains two different sugar chains, the homopolymer common antigen (A band) and the heteropolymer O antigen (B band), which impart serospecificity. The characteristics of LPS are generally assessed after isolation rather than in the context of whole bacteria. Here we used atomic force microscopy (AFM) to probe the physical properties of the LPS of P. aeruginosa strain PA103 (serogroup O11) in situ. This strain contains a mixture of long and very long polymers of O antigen, regulated by two different genes. For this analysis, we studied the wild-type strain and four mutants, ΔWzz1 (producing only very long LPS), ΔWzz2 (producing only long LPS), DΔM (with both the wzz1 and wzz2 genes deleted), and Wzy::GM (producing an LPS core oligosaccharide plus one unit of O antigen). Forces of adhesion between the LPS on these strains and the silicon nitride AFM tip were measured, and the Alexander and de Gennes model of steric repulsion between a flat surface and a polymer brush was used to calculate the LPS layer thickness (which we refer to as length), compressibility, and spacing between the individual molecules. LPS chains were longest for the wild-type strain and ΔWzz1, at 170.6 and 212.4 nm, respectively, and these values were not statistically significantly different from one another. Wzy::GM and DΔM have reduced LPS lengths, at 34.6 and 37.7 nm, respectively. Adhesion forces were not correlated with LPS length, but a relationship between adhesion force and bacterial pathogenicity was found in a mouse acute pneumonia model of infection. The adhesion forces with the AFM probe were lower for strains with LPS mutations, suggesting that the wild-type strain is optimized for maximal adhesion. Our research contributes to further understanding of the role of LPS in the adhesion and virulence of

  4. Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Trogisch, S.; Simpson, M.J.; Taub, H.;

    2005-01-01

    We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional...

  5. 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

  6. Structural investigation of ionic liquid/rubrene single crystal interfaces by using frequency-modulation atomic force microscopy.

    Science.gov (United States)

    Yokota, Yasuyuki; Hara, Hisaya; Harada, Tomohiro; Imanishi, Akihito; Uemura, Takafumi; Takeya, Jun; Fukui, Ken-ichi

    2013-11-21

    Frequency-modulation atomic force microscopy (FM-AFM) was employed to reveal the structural properties of a rubrene single crystal immersed in an ionic liquid. We found large vacancies formed by the anisotropic dissolution of rubrene molecules. Molecular resolution imaging revealed that structures of FM-AFM images deviated from the bulk-terminated structure. PMID:24091742

  7. A method for the direct measurement of surface tension of atmospherically relevant aerosol particles using atomic force microscopy

    OpenAIRE

    Hritz, A. D.; Raymond, T. M.; Dutcher, D. D.

    2016-01-01

    Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect sufficiently large volumes of atmospheric aerosol for use in typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A...

  8. 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.

  9. Atomic force microscopy analysis of progenitor corneal epithelial cells fractionated by a rapid centrifugation isolation technique.

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    Full Text Available PURPOSE: To investigate the use of atomic force microscopy (AFM to image the three groups of corneal epithelial cells fractionated by a novel rapid centrifugation isolation technique. METHODS: Epithelial cells harvested from primary cultures of rabbit limbal rings were centrifuged onto uncoated dishes, first at 1400 rpm and then at 1800 rpm. The adherent cells after centrifugation at 1400 rpm (ATC1, the adherent cells at 1800 rpm (ATC2 and the non-adherent cells at 1800 rpm (NAC were investigated for BrdU retention and were subjected to contact mode AFM and Transmission Electron Microscopy (TEM. RESULTS: Compared with unfractionated cells, the ATC1 group, accounting for about 10% of the whole population, was enriched in BrdU label-retaining cells. There were dramatic overall shape, surface membrane and intra-cellular ultrastructure differences noted among ATC1, ATC2 and NAC populations. The whole cell roughness measurements were 21.1±1.5 nm, 79.5±3.4 nm and 103±4.6 nm for the ATC1, ATC2 and NAC groups, respectively. The mero-nucleus roughness measurements were 34.2±1.7 nm, 13.0±0.8 nm and 8.5±0.5 nm in the ATC1, ATC2 and NAC populations, respectively. CONCLUSIONS: AFM was found to be a good tool for distinguishing among the three groups of cells. BrdU label retention, the AFM parameters and TEM together suggest that the ATC1, ATC2 and NAC populations may be progenitor corneal epithelial cells, transit amplifying cells and terminal differentiation cells, respectively.

  10. Frequency-modulated atomic force microscopy localises viscoelastic remodelling in the ageing sheep aorta.

    Science.gov (United States)

    Akhtar, R; Graham, H K; Derby, B; Sherratt, M J; Trafford, A W; Chadwick, R S; Gavara, N

    2016-12-01

    Age-related aortic stiffening is associated with cardiovascular diseases such as heart failure. The mechanical functions of the main structural components of the aorta, such as collagen and elastin, are determined in part by their organisation at the micrometer length scale. With age and disease both components undergo aberrant remodelling, hence, there is a need for accurate characterisation of the biomechanical properties at this length scale. In this study we used a frequency-modulated atomic force microscopy (FM-AFM) technique on a model of ageing in female sheep aorta (young: ~18 months, old: >8 years) to measure the micromechanical properties of the medial layer of the ascending aorta. The novelty of our FM-AFM method, operated at 30kHz, is that it is non-contact and can be performed on a conventional AFM using the ׳cantilever tune' mode, with a spatial (areal) resolution of around 1.6μm(2). We found significant changes in the elastic and viscoelastic properties within the medial lamellar unit (elastic lamellae and adjacent inter-lamellar space) with age. In particular, there was an increase in elastic modulus (Young; geometric mean (geometric SD)=42.9 (2.26)kPa, Old=113.9 (2.57)kPa, Pmodulus respectively) (Young; G'=14.3 (2.26)kPa, Old G'=38.0 (2.57)kPa, PYoung; G″=14.5 (2.56)kPa, Old G″=32.8 (2.52)kPa, P<0.0001). The trends observed in the elastic properties with FM-AFM matched those we have previously found using scanning acoustic microscopy (SAM). The utility of the FM-AFM method is that it does not require custom AFM hardware and can be used to simultaneously determine the elastic and viscoelastic behaviour of a biological sample.

  11. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy.

    Science.gov (United States)

    Lee, Jung Ah; Lim, Young Rok; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae

    2016-10-21

    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. PMID:27640642

  12. 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.

  13. Atomic force microscopy studies on phase transitions and surface morphology transformation of CMTC crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, X.N.; Xu, D.; Yuan, D.R.; Sun, D.L.; Lu, M.K.; Jiang, M.H. [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan (China)

    2002-11-01

    Atomic force microscopy (AFM) has been used to investigate the phase transitions and surface morphology transformation of cadmium mercury thiocyanate (CMTC) crystals, which are highly efficient nonlinear optical (NLO) materials for generating blue-violet light by laser frequency doubling. Amorphous aggregates at the crystalline steps become greatly contracted and much more crystalloid after the crystal was kept for one day. Elimination of dangling bonds, which lower the surface free energy at the crystal surface, and structural adjustment inside the crystal are assumed to cause this phase transition. Surface morphology transformations were also observed in CMTC crystals during and after multiple scanning by AFM tips. We have visualized the continuous translation process from two-dimensional nuclei to trigonal microcrystals with almost equal sizes during multiple scanning. In other cases, however, the surface morphology did not change at all during scanning, but became greatly altered hours after scanning. These experimental results suggest that reconstruction is a characteristic growth phenomenon on CMTC crystal surfaces. Reconstruction probably results from the formation of intervening metastable phases that have the potential to arrive at more stable stages; however, multiple scanning of AFM tips greatly affects this translation process. (orig.)

  14. 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.

  15. An intelligent control scheme for precise tip-motion control in atomic force microscopy.

    Science.gov (United States)

    Wang, Yanyan; Hu, Xiaodong; Xu, Linyan

    2016-03-01

    The paper proposes a new intelligent control method to precisely control the tip motion of the atomic force microscopy (AFM). The tip moves up and down at a high rate along the z direction during scanning, requiring the utilization of a rapid feedback controller. The standard proportional-integral (PI) feedback controller is commonly used in commercial AFMs to enable topography measurements. The controller's response performance is determined by the set of the proportional (P) parameter and the integral (I) parameter. However, the two parameters cannot be automatically altered simultaneously according to the scanning speed and the surface topography during continuors scanning, leading to an inaccurate measurement. Thus a new intelligent controller combining the fuzzy controller and the PI controller is put forward in the paper. The new controller automatically selects the most appropriate PI parameters to achieve a fast response rate on basis of the tracking errors. In the experimental setup, the new controller is realized with a digital signal process (DSP) system, implemented in a conventional AFM system. Experiments are carried out by comparing the new method with the standard PI controller. The results demonstrate that the new method is more robust and effective for the precise tip motion control, corresponding to the achievement of a highly qualified image by shortening the response time of the controller. SCANNING 38:93-99, 2016. © 2015 Wiley Periodicals, Inc. PMID:26183109

  16. Substrate dependent morphologies of self-assembled nanocrystalline manganite films: An atomic force microscopy study

    International Nuclear Information System (INIS)

    Thin films of La0.7Sr0.3MnO3 (LSMO) have been deposited on different substrates: Si (001), Al2O3 (AlO) (0001) and LaAlO3 (LAO) (001), using a pulsed laser deposition system. 100 nm films have been deposited at substrate temperature of 700 deg C and oxygen partial pressure of 400 mTorr. X-Ray diffraction analysis shows a polycrystalline growth of both layers on Si and Al2O3 substrates, while a c-axis oriented growth on LAO substrate. Atomic force microscopy images exhibit interesting island-like morphology of grain size ∼ 250 nm on Si substrate. Similar morphology with much smaller (∼ 150 nm), closely packed islands are seen to grow on AlO substrate. Films on LAO show comparatively a smooth morphology with the grains size less than 100 nm, decorated by characteristic depressions at the grain boundaries. The formation of self-assembled nanostructures can be understood on the basis of film-substrate lattice misfit, strains in the systems and eventual growth of the films to attain energy minimization (author)

  17. 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.

  18. Mapping molecular adhesion sites inside SMIL coated capillaries using atomic force microscopy recognition imaging.

    Science.gov (United States)

    Leitner, Michael; Stock, Lorenz G; Traxler, Lukas; Leclercq, Laurent; Bonazza, Klaus; Friedbacher, Gernot; Cottet, Hervé; Stutz, Hanno; Ebner, Andreas

    2016-08-01

    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. PMID:27265903

  19. A variable-width harmonic probe for 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); Xia, Qi, E-mail: qxia@mail.hust.edu.cn, E-mail: michael.wang@nus.edu.sg [State Key Laboratory of Digital Manufacturing Equipment of Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Luo, Yangjun [State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Wang, Michael Yu, E-mail: qxia@mail.hust.edu.cn, 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)

    2015-02-16

    In multifrequency atomic force microscopy (AFM) to simultaneously measure topography and material properties of specimens, it is highly desirable that the higher order resonance frequencies of the cantilever probe are assigned to be integer harmonics of the excitation frequency. The harmonic resonances are essential for significant enhancement of the probe's response at the specified harmonic frequencies. In this letter, a structural optimization technique is employed to design cantilever probes so that the ratios between one or more higher order resonance frequencies and the fundamental natural frequency are ensured to be equal to specified integers and, in the meantime, that the fundamental natural frequency is maximized. Width profile of the cantilever probe is the design variable in optimization. Thereafter, the probes were prepared by modifying a commercial probe through the focused ion beam (FIB) milling. The resonance frequencies of the FIB fabricated probes were measured with an AFM. Results of the measurement show that the optimal design of probe is as effective as design prediction.

  20. Characterization of lignin using multi-angle laser light scattering and atomic force microscopy

    International Nuclear Information System (INIS)

    Small differences in the isolation techniques of lignin can result in significant changes in its molecular structure and configuration. Light scattering (evaluated at 18 different angles in a plane), Atomic Force Microscopy (AFM) and Near Infrared Spectroscopy (NIR) proved very effective for evaluating the characteristics of lignin. Zimm plots were generated using Zimm, Debye and Berry formalisms to evaluate the weight average molecular weight (MW), radius of gyration (r g), hydrodynamic radius (r h) and second virial coefficient (A 2). Two types of lignin and nine different solvents were used for the study, to analyze the conformation of lignin molecules in different solvents expected to be used in lignin degradation and subsequent analysis. Absolute MW and r g decreased and the dn/dc increased when the solvent used for lignin was changed from water to sodium hydroxide. The two types of lignin also exhibited different values for all the above estimated parameters. This study also highlighted the differences between the unlyophilized and lyophilized lignin in terms of aggregation, pH dependence and stability over time. This aggregation has never been seen on a ultraviolet (UV) or refractive index (RI) detector that has been used so far for liquid chromatography (LC) reducing the reliability of lignin depolymerization data obtained without light scattering

  1. Fabrication of a polymer-metal combined atomic force microscopy probe for coarse food surface imaging.

    Science.gov (United States)

    Kang, Hyen-Wook; Muramatsu, Hiroshi; Kwon, Young-Soo

    2013-05-01

    We fabricated a polymer-metal combined atomic force microscopy (AFM) probe by two steps; a polymeric resin was used at first step, and a metal-ion was used at second step which needs more fabricating time than the resin. At first step, we fabricated a cylindrical base on to a commercial cantilever. At second step, we fabricated a conical probe on to the fabricated cylindrical base. To make the conical probe composed with silver, a 0.2 M aqueous solution of silver nitrate (AgNO3) was used. A 50 microm length polymeric-metallic hybrid tip has been fabricated to observe large bio and food samples. Generally, the AFM images of bio/food samples show cliff-like sharp patters in vertical. However, the AFM image by fabricated long tip shows clear structure of each brown rice flours. As most of commercial tips have three-angular pyramidal, the scanned results should be influenced by the lateral face of the three-angular pyramid, which results in cliff-like images. Because the sample size is large, the side area of the sample was adversely affected by the pyramidal structure during imaging. This problem may be resolved by designing conical structure tips. As the conical structure has no edge, the AFM image becomes clear. The fabricated tip has conical structure, and a clear AFM image was achieved. PMID:23858900

  2. Elastic and viscoelastic characterization of inhomogeneous polymers by bimodal atomic force microscopy

    Science.gov (United States)

    Nguyen, Hung K.; Ito, Makiko; Nakajima, Ken

    2016-08-01

    The elastic and viscoelastic responses of inhomogeneous polymers upon interacting with an atomic force microscopy (AFM) probe are simultaneously characterized by a bimodal AFM approach namely the amplitude- and frequency-modulation (AM–FM) method. In this approach, the AFM probe is operated in the AM mode at the first flexural frequency and in the FM mode at a higher flexural frequency. The AM mode provides information about the viscoelasticity of polymers in terms of the mechanical loss tangent, whereas the modulus of polymers is obtained as a function of the frequency shift of flexural frequencies in both modes. For a glassy polymer blend, the AM–FM method provides a consistent result in both the elastic modulus and loss tangent in comparison with those obtained by other methods. Moreover, a significant improvement of the contrast and lateral resolution in the AM–FM modulus image can be observed. However, the current approach shows a substantial increase in the modulus of rubbery polymers.

  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. Atomic force microscopy analysis of synthetic membranes applied in release studies

    Science.gov (United States)

    Olejnik, Anna; Nowak, Izabela

    2015-11-01

    Synthetic membranes are commonly used in drug release studies and are applied mostly in quality control. They contain pores through which the drug can be diffused directly into the receptor fluid. Investigation of synthetic membranes permits determination of their structure and characterization of their properties. We suggest that the preliminary characterization of the membranes can be relevant to the interpretation of the release results. The aim of this study was to compare eight synthetic membranes by using atomic force microscopy in order to predict and understand their behavior in the release experiments. The results proved that polytetrafluoroethylene membrane was not suitable for the release study of tetrapeptide due to its hydrophobic nature, thickness and the specific structure with high trapezoid shaped blocks. The additional substructures in pores of mixed cellulose esters and nylon membranes detected by AFM influenced the diffusion rate of the active compound. These findings indicate that the selection of the membrane for the release studies should be performed cautiously by taking into consideration the membrane properties and by analyzing them prior the experiment.

  5. Imaging Water Thin Films in Ambient Conditions Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Sergio Santos

    2016-03-01

    Full Text Available All surfaces exposed to ambient conditions are covered by a thin film of water. Other than at high humidity conditions, i.e., relative humidity higher than 80%, those water films have nanoscale thickness. Nevertheless, even the thinnest film can profoundly affect the physical and chemical properties of the substrate. Information on the structure of these water films can be obtained from spectroscopic techniques based on photons, but these usually have poor lateral resolution. When information with nanometer resolution in the three dimensions is needed, for example for surfaces showing heterogeneity in water affinity at the nanoscale, Atomic Force Microscopy (AFM is the preferred tool since it can provide such resolution while being operated in ambient conditions. A complication in the interpretation of the data arises when using AFM, however, since, in most cases, direct interaction between a solid probe and a solid surface occurs. This induces strong perturbations of the liquid by the probe that should be controlled or avoided. The aim of this review is to provide an overview of different AFM methods developed to overcome this problem, measuring different interactions between the AFM probe and the water films, and to discuss the type of information about the water film that can be obtained from these interactions.

  6. Characterization of designed cobaltacarborane porphyrins using conductive probe atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Venetia D. Lyles

    2016-03-01

    Full Text Available Porphyrins and metalloporphyrins have unique chemical and electronic properties and thus provide useful model structures for studies of nanoscale electronic properties. The rigid planar structures and -conjugated backbones of porphyrins convey robust electrical characteristics. For our investigations, cobaltacarborane porphyrins were synthesized using a ring-opening zwitterionic reaction to produce isomers with selected arrangements of carborane clusters on each macrocycle. Experiments were designed to investigate how the molecular structure influences the self-organization, surface assembly, and conductive properties of three molecular structures with 2, 4, or 8 cobaltacarborane substituents. Current versus voltage (I-V spectra for designed cobaltacarborane porphyrins deposited on conductive gold substrates were acquired using conductive probe atomic force microscopy (CP-AFM. Characterizations with CP-AFM provide capabilities for obtaining physical measurements and structural information with unprecedented sensitivity. We found that the morphology of cobaltacarborane porphyrin structures formed on surfaces depends on a complex interplay of factors such as the solvent used for dissolution, the nature of the substrate, and the design of the parent molecule. The conductive properties of cobaltacarborane porphyrins were observed to change according to the arrangement of cobaltacarborane substituents. Specifically, the number and placement of the cobaltacarborane ligands on the porphyrin macrocycle affect the interactions that drive porphyrin self-assembly and crystallization. Interestingly, coulombic staircase I-V profiles were detected for a porphyrin with two cobaltacarborane substituents.

  7. High-resolution atomic force microscopy of duplex and triplex DNA molecules

    International Nuclear Information System (INIS)

    Double-stranded poly(dG)-poly(dC) and triple-stranded poly(dG)-poly(dG)-poly(dC) DNA were deposited on the modified surface of highly oriented pyrolitic graphite (HOPG) and visualized using atomic force microscopy with high-resolution (radius of ∼1 nm) tips. The high resolution attained by this technique enabled us to detect single-stranded regions in double-stranded poly(dG)-poly(dC) and double-stranded and single-stranded regions in poly(dG)-poly(dG)-poly(dC) triplexes, as well as to resolve the helical pitch of the triplex molecules. We could also follow the reaction of G-strand extension in poly(dG)-poly(dC) by the Klenow exo- fragment of DNA polymerase I. This approach to molecular visualization could serve as a useful tool for the investigation of irregular structures in canonical DNA and other biopolymers, as well as studies of the molecular mechanisms of DNA replication and transcription

  8. High-resolution atomic force microscopy of duplex and triplex DNA molecules

    Energy Technology Data Exchange (ETDEWEB)

    Klinov, Dmitry [Laboratory of Physics of Nanostructures, Ecole Polytechnique Federale de Lausanne (EPFL), Station 3, CH-1015 Lausanne (Switzerland); Dwir, Benjamin [Laboratory of Physics of Nanostructures, Ecole Polytechnique Federale de Lausanne (EPFL), Station 3, CH-1015 Lausanne (Switzerland); Kapon, Eli [Laboratory of Physics of Nanostructures, Ecole Polytechnique Federale de Lausanne (EPFL), Station 3, CH-1015 Lausanne (Switzerland); Borovok, Natalia [Department of Biochemistry, George S Wise Faculty of Life Sciences, Tel-Aviv University (Israel); Molotsky, Tatiana [Department of Biochemistry, George S Wise Faculty of Life Sciences, Tel-Aviv University (Israel); Kotlyar, Alexander [Department of Biochemistry, George S Wise Faculty of Life Sciences, Tel-Aviv University (Israel)

    2007-06-06

    Double-stranded poly(dG)-poly(dC) and triple-stranded poly(dG)-poly(dG)-poly(dC) DNA were deposited on the modified surface of highly oriented pyrolitic graphite (HOPG) and visualized using atomic force microscopy with high-resolution (radius of {approx}1 nm) tips. The high resolution attained by this technique enabled us to detect single-stranded regions in double-stranded poly(dG)-poly(dC) and double-stranded and single-stranded regions in poly(dG)-poly(dG)-poly(dC) triplexes, as well as to resolve the helical pitch of the triplex molecules. We could also follow the reaction of G-strand extension in poly(dG)-poly(dC) by the Klenow exo{sup -} fragment of DNA polymerase I. This approach to molecular visualization could serve as a useful tool for the investigation of irregular structures in canonical DNA and other biopolymers, as well as studies of the molecular mechanisms of DNA replication and transcription.

  9. High-resolution atomic force microscopy of duplex and triplex DNA molecules

    Science.gov (United States)

    Klinov, Dmitry; Dwir, Benjamin; Kapon, Eli; Borovok, Natalia; Molotsky, Tatiana; Kotlyar, Alexander

    2007-06-01

    Double-stranded poly(dG)-poly(dC) and triple-stranded poly(dG)-poly(dG)-poly(dC) DNA were deposited on the modified surface of highly oriented pyrolitic graphite (HOPG) and visualized using atomic force microscopy with high-resolution (radius of ~1 nm) tips. The high resolution attained by this technique enabled us to detect single-stranded regions in double-stranded poly(dG)-poly(dC) and double-stranded and single-stranded regions in poly(dG)-poly(dG)-poly(dC) triplexes, as well as to resolve the helical pitch of the triplex molecules. We could also follow the reaction of G-strand extension in poly(dG)-poly(dC) by the Klenow exo- fragment of DNA polymerase I. This approach to molecular visualization could serve as a useful tool for the investigation of irregular structures in canonical DNA and other biopolymers, as well as studies of the molecular mechanisms of DNA replication and transcription.

  10. 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.

  11. 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.

  12. An atomic force microscopy statistical analysis of laser-induced azo-polyimide periodic tridimensional nanogrooves.

    Science.gov (United States)

    Stoica, Iuliana; Epure, Luiza; Sava, Ion; Damian, Victor; Hurduc, Nicolae

    2013-09-01

    The surface morphology of azo-polyimide films was investigated after 355 nm Nd: YAG laser irradiation with two different incident fluencies. Atomic force microscopy (AFM) was employed to correlate the laser-induced tridimensional nanogrooved surface relief with the incident fluence and the number of irradiation pulses. The height images revealed that the grooves depth increased even tens of times by increasing the incident fluence, using the same numbers of irradiation pulses. For low incident fluence, the films were uniformly patterned till 100 pulses of irradiation. Instead, when using higher fluence, after 15 pulses of irradiation the accuracy of the surface relief definition was reduced. This behavior could be explained by means of two different mechanisms, one that suppose the film photo-fluidization due to the cis-trans isomerization processes of the azo-groups and the second one responsible for the directional mass displacement. The dominant surface direction and parameters like isotropy, periodicity, and period were evaluated from the polar representation for texture analysis, revealing the appearance of ordered and directionated nanostructures for most of the experimental conditions. Also, the graphical studies of the functional volume parameters have evidenced the improvement of the relief structuration during surface nanostructuration. The correlation of these statistical texture parameters with the irradiation characteristics is important in controlling the alignment of either the liquid crystals or the cells/tissues on patterned azo-polyimide surfaces for optoelectronic devices and implantable biomaterials, respectively. PMID:23801415

  13. Visualisation of the interaction between Acidithiobacillus ferrooxidans and oil shale by atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Milić Jelena S.

    2012-01-01

    Full Text Available This study visually documents the mechanical contact and interaction between the bacterial cells of two biogeocenotically different strains of Acidithiobacillus ferrooxidans (At. ferrooxidans and oil shale containing pyrite. Atomic force microscopy (AFM imaging was used to visualise initial interaction between the microorganisms and the surface minerals of an oil shale and to evaluate bacterial effects in the first hours of the bioleaching process. Acidithiobacillus ferrooxidans was attached to the shale surface already after 2 h, and after 48 h, numerous cells covered the surface with a biofilm. After 5 day incubation with At. ferrooxidans, AFM imaging revealed ellipsoid etched pits that represent footprints left by detached cells. Combining AFM surface imaging and leaching analysis following bacterial colonisation of oil shale layers demonstrates that an initial attachment to the surface is necessary for the leaching and that later on, once a sufficient concentration of Fe2+ ions in the solution is achieved, cells detach to become free cells, and leaching occurs primarily by the Fe3+. This experiment confirmed that microorganisms isolated from sites in which a particular substrate is found will demonstrate stronger binding to that substrate.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. A monolithic MEMS position sensor for closed-loop high-speed atomic force microscopy.

    Science.gov (United States)

    Hosseini, N; Nievergelt, A P; Adams, J D; Stavrov, V T; Fantner, G E

    2016-04-01

    The accuracy and repeatability of atomic force microscopy (AFM) imaging significantly depend on the accuracy of the piezoactuator. However, nonlinear properties of piezoactuators can distort the image, necessitating sensor-based closed-loop actuators to achieve high accuracy AFM imaging. The advent of high-speed AFM has made the requirements on the position sensors in such a system even more stringent, requiring higher bandwidths and lower sensor mass than traditional sensors can provide. In this paper, we demonstrate a way for high-speed, high-precision closed-loop AFM nanopositioning using a novel, miniaturized micro-electro-mechanical system position sensor in conjunction with a simple PID controller. The sensor was developed to respond to the need for small, lightweight, high-bandwidth, long-range and sub-nm-resolution position measurements in high-speed AFM applications. We demonstrate the use of this sensor for closed-loop operation of conventional as well as high-speed AFM operation to provide distortion-free images. The presented implementation of this closed-loop approach allows for positioning precision down to 2.1 Å, reduces the integral nonlinearity to below 0.2%, and allows for accurate closed loop imaging at line rates up to 300 Hz.

  19. 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.

  20. 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. PMID:27162352

  1. A monolithic MEMS position sensor for closed-loop high-speed atomic force microscopy.

    Science.gov (United States)

    Hosseini, N; Nievergelt, A P; Adams, J D; Stavrov, V T; Fantner, G E

    2016-04-01

    The accuracy and repeatability of atomic force microscopy (AFM) imaging significantly depend on the accuracy of the piezoactuator. However, nonlinear properties of piezoactuators can distort the image, necessitating sensor-based closed-loop actuators to achieve high accuracy AFM imaging. The advent of high-speed AFM has made the requirements on the position sensors in such a system even more stringent, requiring higher bandwidths and lower sensor mass than traditional sensors can provide. In this paper, we demonstrate a way for high-speed, high-precision closed-loop AFM nanopositioning using a novel, miniaturized micro-electro-mechanical system position sensor in conjunction with a simple PID controller. The sensor was developed to respond to the need for small, lightweight, high-bandwidth, long-range and sub-nm-resolution position measurements in high-speed AFM applications. We demonstrate the use of this sensor for closed-loop operation of conventional as well as high-speed AFM operation to provide distortion-free images. The presented implementation of this closed-loop approach allows for positioning precision down to 2.1 Å, reduces the integral nonlinearity to below 0.2%, and allows for accurate closed loop imaging at line rates up to 300 Hz. PMID:26894523

  2. 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.

  3. Adsorption of chitosan onto carbonaceous surfaces and its application: atomic force microscopy study

    International Nuclear Information System (INIS)

    The adsorption of chitosan onto highly ordered pyrolytic graphite(HOPG) surfaces and its applications have been studied by atomic force microscopy (AFM). The results indicated that chitosan topography formed on the HOPG surface significantly depends on the pH conditions and its concentration for the incubation. Under strongly acidic conditions (pH -1, chitosan formed into uniform network structures composed of fine chains. When the solution pH was changed from 3.5 to 6.5, chitosan tends to form a thicker film. Under neutral and basic conditions, chitosan changed into spherical nanoparticles, and their sizes were increased with increasing pH. Dendritic structures have been observed when the chitosan concentration was increased up to 5 mg ml-1. In addition, the chitosan topography can also be influenced by ionic strength and the addition of different metal ions. When 0.1 M metal ions Na+, Mg2+, Ca2+ and Cu2+ were added into the chitosan solution at pH 3.0 for the incubation, network structures, branched chains, block structures and dense networks attached with many small particles were observed, respectively. The potential applications of these chitosan structures on HOPG have been explored. Preliminary results characterized by AFM and XPS indicated that the chitosan network formed on the HOPG surface can be used for AFM lithography, selective adsorption of gold nanoparticles and DNA molecules.

  4. 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.

  5. 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.

  6. 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. PMID:27214690

  7. 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.

  8. Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions in Atomic Force Microscopy

    OpenAIRE

    Cantrell, John H.; Cantrell, Sean A.

    2010-01-01

    The various dynamical implementations of the atomic force microscope have become important nanoscale characterization tools for the development of novel materials and devices. One of the most significant factors affecting all dynamical AFM modalities is the cantilever tip-sample surface interaction force. We have developed a detailed mathematical model of this interaction that includes a quantitative consideration of the nonlinearity of the interaction force as a function of the cantilever ti...

  9. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

    International Nuclear Information System (INIS)

    The air-lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air-liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C). Effects of surface compression and the presence of SP-C on the monolayer structure and surface potential distribution were investigated using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We show that topography and locally variable surface potential of DPPC-eggPG lipid mixture are similar to those of pulmonary surfactant BLES in the presence of SP-C and differ in surface potential when SP-C is absent.

  10. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Hane, Francis [Department of Biology, Faculty of Science, University of Waterloo, Ontario (Canada); Moores, Brad [Department of Physics and Astronomy, Faculty of Science, University of Waterloo, Ontario (Canada); Amrein, Matthias [Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Alberta, Canada. (Canada); Leonenko, Zoya, E-mail: zleonenk@uwaterloo.ca [Department of Biology, Faculty of Science, University of Waterloo, Ontario (Canada); Department of Physics and Astronomy, Faculty of Science, University of Waterloo, Ontario (Canada)

    2009-07-15

    The air-lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air-liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C). Effects of surface compression and the presence of SP-C on the monolayer structure and surface potential distribution were investigated using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We show that topography and locally variable surface potential of DPPC-eggPG lipid mixture are similar to those of pulmonary surfactant BLES in the presence of SP-C and differ in surface potential when SP-C is absent.

  11. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    International Nuclear Information System (INIS)

    Research highlights: → The surface roughness of the bare substrate influence the oxide layer growth. → The oxide layer roughness follows power laws and belongs to universality class. → At low growth temperature, the p-n heterojunction disappears in some places. → SKPFM images allow the direct visualization of local corrosion sites. → Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  12. Bowstring Stretching and Quantitative Imaging of Single Collagen Fibrils via Atomic Force Microscopy.

    Science.gov (United States)

    Quigley, Andrew S; Veres, Samuel P; Kreplak, Laurent

    2016-01-01

    Collagen is the primary structural protein in animals. Serving as nanoscale biological ropes, collagen fibrils are responsible for providing strength to a variety of connective tissues such as tendon, skin, and bone. Understanding structure-function relationships in collagenous tissues requires the ability to conduct a variety of mechanical experiments on single collagen fibrils. Though significant advances have been made, certain tests are not possible using the techniques currently available. In this report we present a new atomic force microscopy (AFM) based method for tensile manipulation and subsequent nanoscale structural assessment of single collagen fibrils. While the method documented here cannot currently capture force data during loading, it offers the great advantage of allowing structural assessment after subrupture loading. To demonstrate the utility of this technique, we describe the results of 23 tensile experiments in which collagen fibrils were loaded to varying levels of strain and subsequently imaged in both the hydrated and dehydrated states. We show that following a dehydration-rehydration cycle (necessary for sample preparation), fibrils experience an increase in height and decrease in radial modulus in response to one loading-unloading cycle to strain 5%. In fibril segments that ruptured during their second loading cycle, we show that the fibril structure is affected away from the rupture site in the form of discrete permanent deformations. By comparing the severity of select damage sites in both hydrated and dehydrated conditions, we demonstrate that dehydration masks damage features, leading to an underestimate of the degree of structural disruption. Overall, the method shows promise as a powerful tool for the investigation of structure-function relationships in nanoscale fibrous materials. PMID:27598334

  13. Rapid recognition and functional analysis of membrane proteins on human cancer cells using atomic force microscopy.

    Science.gov (United States)

    Li, Mi; Xiao, Xiubin; Liu, Lianqing; Xi, Ning; Wang, Yuechao

    2016-09-01

    Understanding the physicochemical properties of cell surface signalling molecules is important for us to uncover the underlying mechanisms that guide the cellular behaviors. Atomic force microscopy (AFM) has become a powerful tool for detecting the molecular interactions on individual cells with nanometer resolution. In this paper, AFM peak force tapping (PFT) imaging mode was applied to rapidly locate and visually map the CD20 molecules on human lymphoma cells using biochemically sensitive tips. First, avidin-biotin system was used to test the effectiveness of using PFT imaging mode to probe the specific molecular interactions. The adhesion images obtained on avidin-coated mica using biotin-tethered tips obviously showed the recognition spots which corresponded to the avidins in the simultaneously obtained topography images. The experiments confirmed the specificity and reproducibility of the recognition results. Then, the established procedure was applied to visualize the nanoscale organization of CD20s on the surface of human lymphoma Raji cells using rituximab (a monoclonal anti-CD20 antibody)-tethered tips. The experiments showed that the recognition spots in the adhesion images corresponded to the specific CD20-rituximab interactions. The cluster sizes of CD20s on lymphoma Raji cells were quantitatively analyzed from the recognition images. Finally, under the guidance of fluorescence recognition, the established procedure was applied to cancer cells from a clinical lymphoma patient. The results showed that there were significant differences between the adhesion images obtained on cancer cells and on normal cells (red blood cell). The CD20 distributions on ten cancer cells from the patient were quantified according to the adhesion images. The experimental results demonstrate the capability of applying PFT imaging to rapidly investigate the nanoscale biophysical properties of native membrane proteins on the cell surface, which is of potential significance in

  14. 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.

  15. Attempts to test an alternative electrodynamic theory of superconductors by low-temperature scanning tunneling and atomic force microscopy

    OpenAIRE

    Peronio, Angelo; Giessibl, Franz J

    2016-01-01

    We perform an experiment to test between two theories of the electrodynamics of superconductors: the standard London theory and an alternative proposed by J. E. Hirsch. The two alternatives give different predictions with respect to the screening of an electric field by a superconductor, and we try to detect this effect using atomic force microscopy on a niobium sample. We also perform the reverse experiment, where we demonstrate that a superconductive tip mounted on a qPlus force sensor with...

  16. Nano-scale mechanical probing of supported lipid bilayers with atomic force microscopy

    OpenAIRE

    Das, Chinmay; Sheik, Khizar H.; Olmsted, Peter D.; Connell, Simon D.

    2010-01-01

    We present theory and experiments for the force-distance curve $F(z_0)$ of an atomic force microscope (AFM) tip (radius $R$) indenting a supported fluid bilayer (thickness $2d$). For realistic conditions the force is dominated by the area compressibility modulus $\\kappa_A$ of the bilayer, and, to an excellent approximation, given by $F= \\pi \\kappa_A R z_0^2/(2d-z_0)^2$. The experimental AFM force curves from coexisting liquid ordered and liquid disordered domains in 3-component lipid bilayers...

  17. Optical and mechanical detection of near-field light by atomic force microscopy using a piezoelectric cantilever

    Science.gov (United States)

    Satoh, Nobuo; Kobayashi, Kei; Watanabe, Shunji; Fujii, Toru; Matsushige, Kazumi; Yamada, Hirofumi

    2016-08-01

    In this study, we developed an atomic force microscopy (AFM) system with scanning near-field optical microscopy (SNOM) using a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film. Both optical and mechanical detection techniques were adopted in SNOM to detect scattered light induced by the interaction of the PZT cantilever tip apex and evanescent light, and SNOM images were obtained for each detection scheme. The mechanical detection technique did allow for a clear observation of the light scattered from the PZT cantilever without the interference observed by the optical detection technique, which used an objective lens, a pinhole, and a photomultiplier tube.

  18. 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.

  19. 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

  20. Haptics and Graphic Analogies for the Understanding of Atomic Force Microscopy

    OpenAIRE

    Millet, Guillaume; LECUYER, Anatole; BURKHARDT, Jean Marie; Haliyo, Sinan; Regnier, Stéphane

    2013-01-01

    This paper aims to evaluate the benefits of using virtual reality and force-feedback to help teaching nanoscale applications. We propose a teaching aid that combines graphic analogies and haptics intended to improve the grasp of non-intuitive nanoscale phenomena for people without prior knowledge of nanophysics. We look specifically at the most important nanophysical phenomenon, namely, the behavior of the probe of an Atomic Force Microscope (AFM) as it approaches a sample. The results from e...

  1. Measurement of the absolute separation for atomic force microscopy measurements in the presence of adsorbed polymer

    OpenAIRE

    McKee, C. T.; Mosse, W. K. J.; Ducker, W. A.

    2006-01-01

    We demonstrate that the absolute separation between an atomic force microscope (AFM) tip and a solid substrate can be measured in the presence of an irreversibly adsorbed polymer film. The separation is obtained from the analysis of a scattered evanescent wave that is generated at the surface of the solid. By comparing our scattering measurements to conventional AFM measurements, we also show an example where a conventional AFM measurement gives the incorrect force-distance profile. We valida...

  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. PMID:27167473

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.)

  9. 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.

  10. Grain boundary sliding quantification by atomic force microscopy: contribution to high temperature embrittlement analyses

    International Nuclear Information System (INIS)

    We developed an original experimental method for measuring grain boundary sliding by atomic force microscopy. The analysed alloys were previously tested at high temperatures and low strain rates, for short time tests. We measured grain boundary sliding along his perpendicular component to the sample surface. The detection limit is of 10 nm. Thin and flat austenitic stainless steels and superalloys samples were tested at high temperature (360 C to 750 C), under ultra high vacuum atmosphere, with slow rate tensile tests and constant load tests. After short times tests, AFM characterization showed that grain boundary sliding could be activated at the loading, within amplitudes of several tens of nm. Furthermore, after short time tests, grain boundary sliding amplitudes are independent of the geometrical orientation of the boundary trace compared with loading direction. On the other hand crystallographic misorientation has a strong influence on boundaries propensity to slide. Intergranular segregation was also analyzed by AES for two alloys (304H austenitic stainless steel and X- 750 nickel-base alloy), previously submitted to high temperature slow strain rate tensile tests. AES analysis showed preferential segregation of S and P near 304H triple junctions. Whereas, AES analysis on X-750 alloy showed P segregation at the bottom of microvoids distributed on a micro-ductile grain facet and a strong segregation of S at the location of grain boundary precipitate. Our experimental methods allows the study of the correlation between two main phenomena contributing to high temperature embrittlement: grain boundary sliding and intergranular segregation embrittlement. Determining grain boundary sliding kinetics should confirm our method of step measure by AFM as a way to indicate high temperature embrittlement sensitivity of alloys in service conditions and also give information about the contribution of grain boundary sliding to stress corrosion cracking initiation and

  11. 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.

  12. Nanomechanics of silicon surfaces with atomic force microscopy: An insight to the first stages of plastic deformation

    Science.gov (United States)

    Garcia-Manyes, Sergi; Güell, Aleix G.; Gorostiza, Pau; Sanz, Fausto

    2005-09-01

    The use of stiff cantilevers with diamond tips allows us to perform nanoindentations on hard covalent materials such as silicon with atomic force microscopy. Thanks to the high sensitivity in the force measurements together with the high resolution upon imaging the surface, we can study nanomechanical properties. At this scale, the surface deforms, following a simple non-Hertzian spring model. The plastic onset can be assessed from a discontinuity in the force-distance curves. Hardness measurements with penetration depths as small as 1nm yield H =˜25GPa, thus showing a drastic increase with penetration depths below 5nm.

  13. 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.

  14. 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.

  15. Evaluation of elastic modulus of ultra-thin vermiculite membranes by contact mode atomic force microscopy imaging

    International Nuclear Information System (INIS)

    Mechanical properties of nanometer-thick multilayer vermiculite, a layered silicate, were investigated by atomic force microscopy (AFM) contact mode imaging. Membranes suspended over circular holes were with exfoliated vermiculite platelets. The elastic modulus and pre-stress of each membrane were obtained using AFM combined with finite element analysis. The exfoliated multilayer vermiculite membranes had an average in-plane elastic modulus and average pre-stress of 175 ± 16 GPa and 55 ± 13 MPa, respectively. - Highlights: ► We have investigated mechanical properties of nanometer-thick multilayer vermiculite. ► Suspended vermiculite membranes were characterized by atomic force microscopy. ► Mechanical deformation of the membranes was analyzed with finite element analysis. ► In-plane elastic modulus of the exfoliated multilayer vermiculite was 175 ± 16 GPa

  16. 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.

  17. Nanoscale mechanical probing of supported lipid bilayers with atomic force microscopy.

    Science.gov (United States)

    Das, Chinmay; Sheikh, Khizar H; Olmsted, Peter D; Connell, Simon D

    2010-10-01

    We present theory and experiments for the force-distance curve F(z(0)) of an atomic force microscope (AFM) tip (radius R) indenting a supported fluid bilayer (thickness 2d). For realistic conditions the force is dominated by the area compressibility modulus κ(A) of the bilayer and, to an excellent approximation, given by F=πκ(A)Rz(0)(2)/(2d-z(0))(2). The experimental AFM force curves from coexisting liquid ordered and liquid disordered domains in three-component lipid bilayers are well described by our model, which provides κ(A) in agreement with literature values. The liquid ordered phase has a yieldlike response that we model as due to the breaking of hydrogen bonds. PMID:21230326

  18. Nano-scale mechanical probing of supported lipid bilayers with atomic force microscopy

    CERN Document Server

    Das, Chinmay; Olmsted, Peter D; Connell, Simon D

    2010-01-01

    We present theory and experiments for the force-distance curve $F(z_0)$ of an atomic force microscope (AFM) tip (radius $R$) indenting a supported fluid bilayer (thickness $2d$). For realistic conditions the force is dominated by the area compressibility modulus $\\kappa_A$ of the bilayer, and, to an excellent approximation, given by $F= \\pi \\kappa_A R z_0^2/(2d-z_0)^2$. The experimental AFM force curves from coexisting liquid ordered and liquid disordered domains in 3-component lipid bilayers are well-described by our model, and provides $\\kappa_A$ in agreement with literature values. The liquid ordered phase has a yield like response that we model by hydrogen bond breaking.

  19. 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.

  20. 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.

  1. 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

  2. Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results

    International Nuclear Information System (INIS)

    We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In0.48Ga0.52P buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, k-vector ⋅ p-vector 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 k-vector ⋅ p-vector 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

  3. Porphyrin effect on the surface morphology of amphiphilic polymers as observed by atomic force microscopy.

    Science.gov (United States)

    Kotova, S L; Timofeeva, V A; Belkova, G V; Aksenova, N A; Solovieva, A B

    2012-02-01

    Complexes of porphyrin photosensitizers (PPS) with triblock copolymers of ethylene- and propylene oxide - Pluronics(®) - exhibit markedly increased activity in the generation of singlet oxygen in aqueous media, as compared to pure porphyrins. Pluronics are amphiphilic polymers with surfactant properties suitable for a number of medical applications. PPS-Pluronic systems are considered as promising agents for photodynamic therapy which implies generation of singlet oxygen in the water-based human tissue. Importantly, Pluronics are capable of solubilization of not only water-soluble, but also hydrophobic PPS providing their transfer into the aqueous phase. It has been shown earlier that specific interactions of PPS with Pluronics must play a primary role for the photocatalytic properties of PPS-Pluronic systems. In the process of solubilization of a hydrophobic porphyrin by a Pluronic, both components are dissolved in an organic solvent, which is then removed, and the dry film is re-dissolved in water. Apparently, the initial binding between the porphyrin and the lipophilic part of the polymer takes place already at the stage of the film formation. We applied atomic force microscopy (AFM) to visualize structures formed by Pluronics upon their interactions with meso-tetraphenylporphyrin (TPP). We studied the surface structure of Pluronics(®) F87, F108 and F127 crystallized alone or together with TPP on silicon substrates from chloroform solutions. We found Pluronics to form similar dendritic structures independently of their molecular weight and degree of hydrophobicity. In the presence of TPP, though, we observed formation of distinct convex structures on top of the Pluronic dendrites. These structures appeared to consist of multiple flat layers placed on top of each other. Their sizes varied among the three Pluronics. We believe that TPP aggregates interact with the hydrophobic units of Pluronics causing the polymer chains to pack themselves in a distinct manner

  4. Studies of single walled carbon nanotubes for biomedical, mechanical and electrical applications using atomic force microscopy

    Science.gov (United States)

    Lahiji, Roya Roientan

    The promise of carbon nanotubes to provide high-strength composites implies that carbon nanotubes might find widespread use throughout the world, implying that humans everywhere will be exposed to carbon nanotube-containing materials. In order to study what effects if any carbon nanotubes might have on the function of living cells, we have studied the association of single stranded DNA (ssDNA) with single wall carbon nanotubes (SWCNTs) as a first step toward understanding the interaction of SWCNTs with living matter. Studies have been performed on both as-received and chemically oxidized SWCNTs to better understand the preferential association of ssDNA with SWCNTs. Samples of T30 ssDNA:SWCNT were examined under ambient conditions using non-contact Atomic Force Microscopy (AFM)) techniques. AFM images of well-dispersed, as-received SWCNTs revealed isolated features on the SWCNT that are 1.4 to 2.8 nm higher than the bare SWCNT itself. X-ray Photoemission Spectroscopy (XPS) confirmed these features to be T30 ssDNA in nature. Chemically oxidizing SWCNTs before dispersion by sonication is found to be an effective way to increase the number of T30 ssDNA features. A series of experiments showed that free radical scavengers such as ascorbic acid and trolox can effectively prevent the conjugation of ssDNA to SWCNTs, suggesting a significant role of free radicals in this association. Also hybridization of the complimentary ssDNA sequences showed the covalent nature of this association. These results are important to understanding the precise mechanism of ssDNA:SWCNT association and provide valuable information for future use in electronics, biosensors and as a possible drug carrier into individual cells. If SWCNTs are used in biosensor or circuit design applications then it is important to note how much energy can be stored in a SWCNT based on its shape and configuration before a permanent damage is introduced to it. Therefore a study has been done on bending SWCNTs into

  5. Raman-atomic force microscopy of the ommatidial surfaces of Dipteran compound eyes

    Science.gov (United States)

    Anderson, Mark S.; Gaimari, Stephen D.

    2003-01-01

    The ommatidial lens surfaces of the compound eyes in several species of files (Insecta: Diptera) and a related order (Mecoptera) were analyzed using a recently developed Raman-atomic force microscope. We demonstrate in this work that the atomic force microscope (AFM) is a potentially useful instrument for gathering phylogenetic data and that the newly developed Raman-AFM may extend this application by revealing nanometer-scale surface chemistry. This is the first demonstration of apertureless near-field Raman spectroscopy on an intact biological surface. For Chrysopilus testaceipes Bigot (Rhagionidae), this reveals unique cerebral cortex-like surface ridges with periodic variation in height and surface chemistry. Most other Brachyceran flies, and the "Nematoceran" Sylvicola fenestralis (Scopoli) (Anisopodidae), displayed the same morphology, while other taxa displayed various other characteristics, such as a nodule-like (Tipula (Triplicitipula) sp. (Tipulidae)) or coalescing nodule-like (Tabanus punctifer Osten Sacken (Tabanidae)) morphology, a smooth morphology with distinct pits and grooves (Dilophus orbatus (Say) (Bibionidae)), or an entirely smooth surface (Bittacus chlorostigma MacLachlan (Mecoptera: Bittacidae)). The variation in submicrometer structure and surface chemistry provides a new information source of potential phylogenetic importance, suggesting the Raman-atomic force microscope could provide a new tool useful to systematic and evolutionary inquiry.

  6. Repulsive tip tilting as the dominant mechanism for hydrogen bond-like features in atomic force microscopy imaging

    Science.gov (United States)

    Lee, Alex J.; Sakai, Yuki; Kim, Minjung; Chelikowsky, James R.

    2016-05-01

    Experimental atomic force microscopy (AFM) studies have reported distinct features in regions with little electron density for various organic systems. These unexpected features have been proposed to be a direct visualization of intermolecular hydrogen bonding. Here, we apply a computational method using ab initio real-space pseudopotentials along with a scheme to account for tip tilting to simulate AFM images of the 8-hydroxyquinoline dimer and related systems to develop an understanding of the imaging mechanism for hydrogen bonds. We find that contrast for the observed "hydrogen bond" feature comes not from the electrostatic character of the bonds themselves but rather from repulsive tip tilting induced by neighboring electron-rich atoms.

  7. Dielectric spectroscopy at the nanoscale by atomic force microscopy: A simple model linking materials properties and experimental response

    International Nuclear Information System (INIS)

    The use of an atomic force microscope for studying molecular dynamics through dielectric spectroscopy with spatial resolution in the nanometer scale is a recently developed approach. However, difficulties in the quantitative connection of the obtained data and the material dielectric properties, namely, frequency dependent dielectric permittivity, have limited its application. In this work, we develop a simple electrical model based on physically meaningful parameters to connect the atomic force microscopy (AFM) based dielectric spectroscopy experimental results with the material dielectric properties. We have tested the accuracy of the model and analyzed the relevance of the forces arising from the electrical interaction with the AFM probe cantilever. In this way, by using this model, it is now possible to obtain quantitative information of the local dielectric material properties in a broad frequency range. Furthermore, it is also possible to determine the experimental setup providing the best sensitivity in the detected signal

  8. Direct visualization of triplex DNA molecular dynamics by fluorescence resonance energy transfer and atomic force microscopy measurements

    Science.gov (United States)

    Chang, Chia-Ching; Lin, Po-Yen; Chen, Yen-Fu; Chang, Chia-Seng; Kan, Lou-Sing

    2007-11-01

    We have detected the dynamics of 17-mer DNA triplex dissociation mechanism at the molecular level. Fluorescence resonance energy transfer (FRET) was used as an indicator of intermolecular interaction in nanometer range, whereas atomic force microscopy (AFM) was employed to address single molecule with sub-angstrom precision. The maximum rupture force of DNA triplex was found at pH 4.65, consistent with macroscopic observations. These results indicated that the FRET together with an AFM detection system could be used to reveal the DNA triplex interaction in nanometer scale unambiguously.

  9. 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.

  10. 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.

  11. Characterization of microfabricated probes for combined atomic force and high-resolution scanning electrochemical microscopy.

    Science.gov (United States)

    Gullo, Maurizio R; Frederix, Patrick L T M; Akiyama, Terunobu; Engel, Andreas; deRooij, Nico F; Staufer, Urs

    2006-08-01

    A combined atomic force and scanning electrochemical microscope probe is presented. The probe is electrically insulated except at the very apex of the tip, which has a radius of curvature in the range of 10-15 nm. Steady-state cyclic voltammetry measurements for the reduction of Ru(NH3)6Cl3 and feedback experiments showed a distinct and reproducible response of the electrode. These experimental results agreed with finite element simulations for the corresponding diffusion process. Sequentially topographical and electrochemical studies of Pt lines deposited onto Si3N4 and spaced 100 nm apart (edge to edge) showed a lateral electrochemical resolution of 10 nm. PMID:16878880

  12. The study of 3-dimensional structures of IgG with atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    YU Yi-gang; XU Ru-xiang; JIANG Xiao-dan; KE Yi-quan

    2005-01-01

    Objective: To detect 3-dimensional images of anti-N-methyl-D-aspartate receptor Nr1 (NMDAr1) polycolonal IgG affixed on mica in physiological environment. Methods: The images and data were obtained from a contact mode and commercial Si3N4 probed tip by using atomic force microscope (AFM). Conclusions: Using AFM to investigate biomacromolecule can make us deeply understand the structure of IgG, which will instruct us to detect the membrane receptor protein as a labelling agent.

  13. Gentle and fast atomic force microscopy with a piezoelectric scanning probe for nanorobotics applications

    International Nuclear Information System (INIS)

    A novel dual tip nanomanipulation atomic force microscope (AFM) platform operating in ambient conditions is presented. The system is equipped with a high frequency quartz piezoelectric self-sensing scanning probe for fast imaging and a passive cantilever for manipulation. The system is validated by imaging and selective pushing/pulling of gold colloid beads (diameters from 80 to 180 nm). This provides a more compact integration compared to an external optical lever and avoids several of its drawbacks such as optical interference and noise, and recalibration in the case of a moving cantilever and a fixed laser source and photodiode sensor. Moreover, as the quartz oscillator exhibits oscillation amplitudes in the sub-picometer range with a resonant frequency in the megahertz range, this dynamic force sensor is ideal for fast AFM imaging. Experiments show an increase by five times in imaging speed compared to a classical AFM system. (paper)

  14. Atomic force microscopy images of T4 bacteriophages on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kolbe, W.F.; Ogletree, D.F.; Salmeron, M.B.

    1991-08-01

    A new atomic force microscope incorporating microfabricated cantilevers and employing laser beam deflection for force detection has been constructed and is being applied to studied of biological material. In this study, T4 bacteriophage virus particles were deposited from solution onto electronic grade flat silicon wafers and imaged in air with the microscope. Microliter droplets of the solution were deposited and either allowed to dry or removed with blotting paper. The images show both isolated viruses and aggregates of various sizes. The external structure as well as strands believed to be DNA streaming out of the virus could be observed. The construction of the microscope and its performance are also described. 19 refs., 4 figs.

  15. Elastic properties of polystyrene nanospheres evaluated with atomic force microscopy: size effect and error analysis.

    Science.gov (United States)

    Guo, Dan; Li, Jingnan; Xie, Guoxin; Wang, Yuanyuan; Luo, Jianbin

    2014-06-24

    The mechanical properties of polystyrene (PS) nanospheres of ca. 50-1000 nm in diameter were evaluated by using an atomic force microscope (AFM). The compressive elastic moduli of individual nanospheres were obtained by analyzing the AFM force-displacement curves on the basis of the Hertz and JKR contact theories. The results showed that the elastic moduli of PS nanospheres of different sizes were in the range of 2-8 GPa. The elastic modulus of PS nanospheres increased with the decrease of the sphere diameter, especially when the diameter was less than 200 nm. The measurement errors due to tip wear and the deformation at the bottom of the sphere were analyzed. Mechanisms for the size dependence on the elastic modulus of PS nanospheres were also discussed. PMID:24892186

  16. An Atomic Force Microscopy based investigation of specific biomechanical properties for various types of neuronal cells

    Science.gov (United States)

    Spedden, Elise; White, James; Kaplan, David; Staii, Cristian

    2012-02-01

    Here we describe the use of Atomic Force Microscope (AFM) based techniques to characterize and explore the influence of biochemical and biomechanical cues on the growth and interaction of neuronal cells with surrounding guidance factors. Specifically, we use AFM topography and AFM force spectroscopy measurements to systematically investigate the morphology, elasticity, and real time growth of neuronal processes in the presence of different types of extracellular matrix proteins and growth factors. We therefore create a series of systems containing specified neuron densities where the type of the underlying growth promoting protein is different from sample to sample. For each system we measure key biomechanical parameters related to neuronal growth such as height and elastic modulus at multiple growth points on several types of neurons. We show that systematic measurements of these parameters yield fundamental information about the role played by substrate-plated guidance factors in determining elastic and morphological properties of neurons during growth.

  17. A comparative analysis of bleached and sound enamel structure through scanning electron microscopy and atomic force microscopy

    International Nuclear Information System (INIS)

    To analyze the effects of bleaching agent on enamel structure and to characterize the morphological and chemical changes in enamel due to bleaching. Study Design: Experimental study. Place and Duration of Study: School of Chemical and Material Engineering (SCME), NUST Islamabad from Feb to May 2013. Materials and Methods: Ten recently extracted pre molars between the 12-22 years age group were randomly assigned into two groups. Group one was a non-bleached control group with sound enamel. Group two was bleached with Everbrite In office tooth whitening system after specimen preparation, surface morphology was observed under SEM (scanned electron microscope) and AFM (Atomic force microscope). Results: The detrimental effects of hydrogen per-oxide on enamel were evident in bleached specimens under SEM, and AFM analysis. Conclusion: There were significant surface alterations found in the bleached specimens as compared to control group. However salivary buffering potentials could overcome the demineralizing effect of bleaching gel. (author)

  18. Characterization of chemically and enzymatically treated hemp fibres using atomic force microscopy and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    George, Michael; Mussone, Paolo G. [Biorefining Conversions and Fermentations Laboratory, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6E 2P5 (Canada); Abboud, Zeinab [Biorefining Conversions and Fermentations Laboratory, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6E 2P5 (Canada); Department of Physics, University of Guelph, Guelph, ON, Canada N1G 2W1 (Canada); Bressler, David C., E-mail: david.bressler@ualberta.ca [Biorefining Conversions and Fermentations Laboratory, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6E 2P5 (Canada)

    2014-09-30

    The mechanical and moisture resistance properties of natural fibre reinforced composites are dependent on the adhesion between the matrix of choice and the fibre. The main goal of this study was to investigate the effect of NaOH swelling of hemp fibres prior to enzymatic treatment and a novel chemical sulfonic acid method on the physical properties of hemp fibres. The colloidal properties of treated hemp fibres were studied exclusively using an atomic force microscope. AFM imaging in tapping mode revealed that each treatment rendered the surface topography of the hemp fibres clean and exposed the individual fibre bundles. Hemp fibres treated with laccase had no effect on the surface adhesion forces measured. Interestingly, mercerization prior to xylanase + cellulase and laccase treatments resulted in greater enzyme access evident in the increased adhesion force measurements. Hemp fibres treated with sulfonic acid showed an increase in surface de-fibrillation and smoothness. A decrease in adhesion forces for 4-aminotoulene-3-sulfonic acid (AT3S) treated fibres suggested a reduction in surface polarity. This work demonstrated that AFM can be used as a tool to estimate the surface forces and roughness for modified fibres and that enzymatic coupled with chemical methods can be used to improve the surface properties of natural fibres for composite applications. Further, this work is one of the first that offers some insight into the effect of mercerization prior to enzymes and the effect on the surface topography. AFM will be used to selectively screen treated fibres for composite applications based on the adhesion forces associated with the colloidal interface between the AFM tip and the fibre surfaces.

  19. Characterization of chemically and enzymatically treated hemp fibres using atomic force microscopy and spectroscopy

    Science.gov (United States)

    George, Michael; Mussone, Paolo G.; Abboud, Zeinab; Bressler, David C.

    2014-09-01

    The mechanical and moisture resistance properties of natural fibre reinforced composites are dependent on the adhesion between the matrix of choice and the fibre. The main goal of this study was to investigate the effect of NaOH swelling of hemp fibres prior to enzymatic treatment and a novel chemical sulfonic acid method on the physical properties of hemp fibres. The colloidal properties of treated hemp fibres were studied exclusively using an atomic force microscope. AFM imaging in tapping mode revealed that each treatment rendered the surface topography of the hemp fibres clean and exposed the individual fibre bundles. Hemp fibres treated with laccase had no effect on the surface adhesion forces measured. Interestingly, mercerization prior to xylanase + cellulase and laccase treatments resulted in greater enzyme access evident in the increased adhesion force measurements. Hemp fibres treated with sulfonic acid showed an increase in surface de-fibrillation and smoothness. A decrease in adhesion forces for 4-aminotoulene-3-sulfonic acid (AT3S) treated fibres suggested a reduction in surface polarity. This work demonstrated that AFM can be used as a tool to estimate the surface forces and roughness for modified fibres and that enzymatic coupled with chemical methods can be used to improve the surface properties of natural fibres for composite applications. Further, this work is one of the first that offers some insight into the effect of mercerization prior to enzymes and the effect on the surface topography. AFM will be used to selectively screen treated fibres for composite applications based on the adhesion forces associated with the colloidal interface between the AFM tip and the fibre surfaces.

  20. Measuring anisotropic friction on WTe2 using atomic force microscopy in the force-distance and friction modes.

    Science.gov (United States)

    Watson, Gregory S; Myhra, Sverre; Watson, Jolanta A

    2010-04-01

    Layered materials which can be easily cleaved have proved to be excellent samples for the study of atomic scale friction. The layered transition metal dichalcogenides have been particularly popular. These materials exhibit a number of interesting properties ranging from superconductivity to low frictional coefficients. In this paper we have investigated the tribology of the dichalcogenide-WTe2. The coefficient of friction is less than 0.040 along the Te rows and increases to over 0.045 across the rows. The frictional forces almost doubled at normal loads of 5000 nN when scanning in the [010] direction in comparison to the [100] direction. The frictional responses of the AFM probe have been monitored in the frictional force and force-versus-distance (f-d) mode. A comparison between the outcomes using the two different modes demonstrates the factors which need to be considered for accurate measurements. PMID:20355449

  1. Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination.

    Science.gov (United States)

    Narchi, Paul; Alvarez, Jose; Chrétien, Pascal; Picardi, Gennaro; Cariou, Romain; Foldyna, Martin; Prod'homme, Patricia; Kleider, Jean-Paul; I Cabarrocas, Pere Roca

    2016-12-01

    Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 100-μm distance in order to compare data from the same area and provide a consistent interpretation. In both measurements, modifications under illumination are observed in accordance with the theory of PIN junctions. Moreover, an unintentional doping during the deposition of the epitaxial silicon intrinsic layer in the solar cell is suggested from the comparison between photovoltage and photocurrent measurements. PMID:26831693

  2. Attempts to test an alternative electrodynamic theory of superconductors by low-temperature scanning tunneling and atomic force microscopy

    Science.gov (United States)

    Peronio, Angelo; Giessibl, Franz J.

    2016-09-01

    We perform an experiment to test between two theories of the electrodynamics of superconductors: the standard London theory and an alternative proposed by J. E. Hirsch [Phys. Rev. B 69, 214515 (2004), 10.1103/PhysRevB.69.214515]. The two alternatives give different predictions with respect to the screening of an electric field by a superconductor, and we try to detect this effect using atomic force microscopy on a niobium sample. We also perform the reverse experiment, where we demonstrate a superconductive tip mounted on a qPlus force sensor. Due to limited accuracy, we are able neither to prove nor to disprove Hirsch's hypothesis. Within our accuracy of 0.17 N/m, the superconductive transition does not alter the atomic-scale interaction between tip and sample.

  3. In-situ scanning electron microscopy and atomic force microscopy Young's modulus determination of indium oxide microrods for micromechanical resonator applications

    Energy Technology Data Exchange (ETDEWEB)

    Bartolomé, Javier; Hidalgo, Pedro; Maestre, David; Cremades, Ana, E-mail: cremades@fis.ucm.es; Piqueras, Javier [Departamento de Física de Materiales, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2014-04-21

    Electric field induced mechanical resonances of In{sub 2}O{sub 3} microrods are studied by in-situ measurements in the chamber of a scanning electron microscope. Young's moduli of rods with different cross-sectional shapes are calculated from the resonance frequency, and a range of values between 131 and 152 GPa are obtained. A quality factor of 1180–3780 is measured from the amplitude-frequency curves, revealing the suitability of In{sub 2}O{sub 3} microrods as micromechanical resonators. The Young's modulus, E, of one of the rods is also measured from the elastic response in the force-displacement curve recorded in an atomic force microscope. E values obtained by in-situ scanning electron microscopy and by atomic force microscopy are found to differ in about 8%. The results provide data on Young's modulus of In{sub 2}O{sub 3} and confirm the suitability of in-situ scanning electron microscopy mechanical resonance measurements to investigate the elastic behavior of semiconductor microrods.

  4. Visualization and quantification of magnetic nanoparticles into vesicular systems by combined atomic and magnetic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dong, C. [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161, Rome (Italy); Department of Physics, SAPIENZA University of Rome, Piazzale A. Moro 5, 00185, Rome (Italy); Corsetti, S.; Passeri, D. [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161, Rome (Italy); Rossi, M. [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161, Rome (Italy); Research Center for Nanotechnology applied to Engineering of SAPIENZA University of Rome (CNIS), Piazzale A. Moro 5, 00185, Rome (Italy); Carafa, M.; Marianecci, C., E-mail: carlotta.marianecci@uniroma1.it [Department of Drug Chemistry and Technologies, SAPIENZA University of Rome, Piazzale A. Moro 5, 00185, Rome (Italy); Pantanella, F. [Department of Public Health and Infectious Diseases, SAPIENZA University of Rome, Piazzale A. Moro 5, 00185, Rome (Italy); Research Center for Nanotechnology applied to Engineering of SAPIENZA University of Rome (CNIS), Piazzale A. Moro 5, 00185, Rome (Italy); Rinaldi, F.; Ingallina, C. [Center for Life Nano Science @ Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161, Rome (Italy); Sorbo, A. [Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità (ISS), Viale Regina Elena 299, 00161, Rome (Italy)

    2015-06-23

    We report a phenomenological approach for the quantification of the diameter of magnetic nanoparticles (MNPs) incorporated in non-ionic surfactant vesicles (niosomes) using magnetic force microscopy (MFM). After a simple specimen preparation, i.e., by putting a drop of solution containing MNPs-loaded niosomes on flat substrates, topography and MFM phase images are collected. To attempt the quantification of the diameter of entrapped MNPs, the method is calibrated on the sole MNPs deposited on the same substrates by analyzing the MFM signal as a function of the MNP diameter (at fixed tip-sample distance) and of the tip-sample distance (for selected MNPs). After calibration, the effective diameter of the MNPs entrapped in some niosomes is quantitatively deduced from MFM images.

  5. Visualization and quantification of magnetic nanoparticles into vesicular systems by combined atomic and magnetic force microscopy

    International Nuclear Information System (INIS)

    We report a phenomenological approach for the quantification of the diameter of magnetic nanoparticles (MNPs) incorporated in non-ionic surfactant vesicles (niosomes) using magnetic force microscopy (MFM). After a simple specimen preparation, i.e., by putting a drop of solution containing MNPs-loaded niosomes on flat substrates, topography and MFM phase images are collected. To attempt the quantification of the diameter of entrapped MNPs, the method is calibrated on the sole MNPs deposited on the same substrates by analyzing the MFM signal as a function of the MNP diameter (at fixed tip-sample distance) and of the tip-sample distance (for selected MNPs). After calibration, the effective diameter of the MNPs entrapped in some niosomes is quantitatively deduced from MFM images

  6. Atomic Force Microscopy-based Cell Nanostructure for Ligand-conjugated Quantum Dot Endocytosis

    Institute of Scientific and Technical Information of China (English)

    Yun-Long PAN; Ji-Ye CAI; Li QIN; Hao WANG

    2006-01-01

    While it has been well demonstrated that quantum dots (QDs) play an important role in biological labeling both in vitro and in vivo,there is no report describing the cellular nanostructure basis of receptor-mediated endocytosis. Here, nanostructure evolution responses to the endocytosis of transferrin force microscopy (AFM). AFM-based nanostructure analysis demonstrated that the Tf-conjugated QDs were specifically and tightly bound to the cell receptors rrelated with the cell membrane receptor-mediated transduction.Consistently, confocal microscopic and flow cytometry results have demonstrated the specificity and the internalization of Tf-QD is linearly related to time. Moreover, while the nanoparticles on the cell membrane increased, the endocytosis was still nanoparticles did not interfere sterically with the binding and function of receptors. Therefore, ligand-conjugated QDs are potentially useful in biological labeling of cells at a nanometer scale.

  7. The investigation of nanotribology of UHMWPE in fluid using atomic force microscopy.

    Science.gov (United States)

    Wu, Jingping; Peng, Zhongxiao

    2015-05-01

    The fundamental understanding of the nanowear behavior of ultrahigh molecular weight polyethylene (UHMWPE) at a nanometer scale needs to be achieved to provide a better understanding of the initiating wear process and the potential causes of the wear particles generation of joint replacement. A nanotribology study was performed using atomic force microscope (AFM) tips sliding against UHMWPE surfaces in both water and bovine serum lubricants. Frictional properties of the nanocontact, and the geometry and mechanical features of the resulting scratches have been quantitatively characterized using AFM lateral force and PeakForce QNM modes. The results in this work indicated that the friction force and friction coefficient were smaller in serum lubricant than that in water. A normal load of 120 nN was the transition point for the plastic deformation of the material. The plastic deformation and material accumulation evolute with the increase of applied normal loads. Material pileup formed at the edges of the scratch, but they were not symmetrical due to the asymmetrical geometry of the silicon AFM tip. The height of the material pileup on the right side was approximately 40-70% of the pileup on the left side. The information may be useful for developing strategies for surface finishing techniques, which can control and minimize the production of asymmetric asperity and the resulting pileup with particular features. Furthermore, the moduli of the pileups were much larger than that of the fresh UHMWPE, which had the moduli greater than those of the inner scratch area. This suggested that stress concentration at these points could cause the pileup to be more susceptible to further wear processes, and eventually result in detaching from the bulk material.

  8. Visualization of chromatin folding patterns in chicken erythrocytes by atomic force microscopy (AFM)

    Institute of Scientific and Technical Information of China (English)

    QIANRUOLAN; ZHENGXIALIU; 等

    1997-01-01

    The organization of the higher order structure of chromatin in chicken erythrocytes has been examined with tapping-mode scanning force microscopy under conditions close to their native envirinment.Reproducible highresolution AFM images of chromatin compaction at several levels can be demonstrated.An extended beads-on-astring (width of - 15-20nm,height of - 2-3nm for each individual nucleosome) can be consistently observed.Furthermore,superbeade (width of - 40nm,height of - 7nm) are demonstrated.Visualization of the solenoid conformation at the level of 30nm chromatin fiber is attained either by using AFM or by using electron microscopy.In addition,tightly coiled chromatin fibers (- 50-60nm and - 90-110nm) can be revealed.Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning the folding pattern of interphase chromatin fibers.

  9. Atomic force microscopy identification of Al-sites on ultrathin aluminum oxide film on NiAl(110)

    Science.gov (United States)

    Li, Yan Jun; Brndiar, J.; Naitoh, Y.; Sugawara, Y.; Štich, I.

    2015-12-01

    Ultrathin alumina film formed by oxidation of NiAl(110) was studied by non-contact atomic force microscopy in an ultra high vacuum at room temperature with the quest to provide the ultimate understanding of structure and bonding of this complicated interface. Using a very stiff Si cantilever with significantly improved resolution, we have obtained images of this system with unprecedented resolution, surpassing all the previous results. In particular, we were able to unambiguously resolve all the differently coordinated aluminum atoms. This is of importance as the previous images provide very different image patterns, which cannot easily be reconciled with the existing structural models. Experiments are supported by extensive density functional theory modeling. We find that the system is strongly ionic and the atomic force microscopy images can reliably be understood from the electrostatic potential which provides an image model in excellent agreement with the experiments. However, in order to resolve the finer contrast features we have proposed a more sophisticated model based on more realistic approximants to the incommensurable alumina interface.

  10. Study of atomic force microscopy nanoindentation for the development of nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Sirena, M., E-mail: sirena@cab.cnea.gov.a [Unite Mixte de Physique CNRS/Thales, Campus de Polytechnique. 1 Avenue A. Fresnel, 91767 Palaiseau (France); Fusil, S. [Universite d' Evry, Batiment des Sciences, rue du pere Jarlan, 91205 Every (France); Bouzehouane, K.; George, J.-M.; Cros, V. [Unite Mixte de Physique CNRS/Thales, Campus de Polytechnique. 1 Avenue A. Fresnel, 91767 Palaiseau (France)

    2009-10-01

    We have studied the fabrication of atomic force microscope (AFM) based nanotemplates using electrically controlled indentation (ECI) and a composite barrier (photoresist/alumina) that is resistant to the lithography process and presents good mechanical properties for indentation. The indentation process is affected by several factors such as the indentation speed, the trigger voltage and the barrier type. We have used the nanotemplate technique to fabricate small gold-gold nanocontacts (1-10 nm). In this limit, the size of the contacts that is obtained through the indentation process seems to be stochastic. However, low dimension, clean metallic contacts were achieved with high temporal stability and compatible with low temperature measurements. The fabricated nanotemplates are versatile and can be used in a wide range of applications, from nanojunctions to connecting a single nano-object. Small area metallic contacts can be used to study spin injection or ballistic transport.

  11. Atomic force microscopy of surface topography of nitrogen plasma treated steel

    CERN Document Server

    Mahboubi, F

    2002-01-01

    Nitriding of steels, using plasma environments has been practiced for many years. A lot of efforts have been put on developing new methods, such as plasma immersion ion implantation (Pl sup 3) and radio frequency (RF) plasma nitriding, for mass transfer of nitrogen into the surface of the work piece. This article presents the results obtained from an in depth investigation of the surface morphology of the treated samples, carried out using an atomic force microscope. Samples from a microalloyed steel, were treated by both methods for 5 hours at different temperatures ranging from 350 to 550 sup d eg sup C in 75% N sub 2 -25% H sub 2 atmosphere. It has been found that the surface of the samples treated by PI sup 3 technique, although having more favorable properties, were rougher than the surfaces treated by RF plasma nitriding.

  12. Low-noise humidity controller for imaging water mediated processes in atomic force microscopy

    Science.gov (United States)

    Gaponenko, I.; Gamperle, L.; Herberg, K.; Muller, S. C.; Paruch, P.

    2016-06-01

    We demonstrate the construction of a novel low-noise continuous flow humidity controller and its integration with a commercial variable-temperature atomic force microscope fluid cell, allowing precise control of humidity and temperature at the sample during nanoscale measurements. Based on wet and dry gas mixing, the design allows a high mechanical stability to be achieved by means of an ultrasonic atomiser for the generation of water-saturated gas, improving upon previous bubbler-based architectures. Water content in the flow is measured both at the inflow and outflow of the fluid cell, enabling the monitoring of water condensation and icing, and allowing controlled variation of the sample temperature independently of the humidity. To benchmark the performance of the controller, the results of detailed noise studies and time-based imaging of the formation of ice layers on highly oriented pyrolytic graphite are shown.

  13. Resistance of single polyaniline fibers and their junctions measured by double-probe atomic force microscopy

    Science.gov (United States)

    Higuchi, Rintaro; Shingaya, Yoshitaka; Nakayama, Tomonobu

    2016-08-01

    Electrical properties of polyaniline (PANI) fibers are of our interest as a component of network materials. Using a multiple-probe atomic force microscope with tuning fork probes, we investigated the resistance of single PANI fibers and their cross-point junction where the fibers contact each other. The resistivity of single PANI fibers was measured to be on the order of 10 Ω cm, and the contact resistance between PANI fibers was on the order of GΩ. The resistances through single cross-point junctions between two PANI fibers were very much dependent on the experimental condition, that is, the cross-point junction is stabilized or destabilized by physically placing the probes onto the two fibers. This suggests the nanomechanical instability of the cross-point junctions and a possibility to construct strain-responsive PANI fiber networks.

  14. Atomic force microscopy observation on nuclear reassembly in a cell-free system

    Institute of Scientific and Technical Information of China (English)

    YANG Ning; CHEN Zhongcai; ZHANG Zhaohui; ZHU Xing; ZHAI Zhonghe; TANG Xiaowei

    2003-01-01

    Cell-free system is interesting and useful for studying nuclear assembly in mitosis. Atomic force micro- scopy (AFM), which is a simple way for imaging fixed reassemble nuclei with high resolution, has not been used in the cell-free system. In this paper, we put forward an air-drying sample preparation for AFM. Using AFM, we observed nuclear reassembly process within 100 nm resolution ina cell-free system. As a result, we found that the images were artifact-free, and with higher resolution compared with fluorescent optical microscope images. Furthermore, the morphology of membrane vesicles was obtained clearly, and a dynamic change of morphology during the vesicles' approaching to nuclear envelope was also observed, which is enlightened to understand the mechanism of nuclear envelope assembly.

  15. Determination of silicone coating Young's modulus using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Thome, T. [PSA Peugeot Citroen, Centre Technique de Velizy, DTI/DITV/PMXP/TAC/PSM, Route de Gisy, 78943 Velizy-Villacoublay (France)], E-mail: tristan.thome@mpsa.com; Fouchez, S.; Delalande, S. [PSA Peugeot Citroen, Centre Technique de Velizy, DTI/DITV/PMXP/TAC/PSM, Route de Gisy, 78943 Velizy-Villacoublay (France)

    2009-01-15

    The polymerisation degree of thin polymer coatings was checked by following the variation of their local mechanical properties. Atomic force microscope (AFM) was used in an indentation mode to investigate the mechanical characteristics of silicone coatings on polycarbonate substrates. The evolution of Young's modulus of the silicone coatings was determined as a function of the polymer annealing time. We have used a relative method to measure Young's moduli, which involves a calibration step with a set of reference polymers. No variation was observed for the modulus of silicone coatings annealed during more than 40 min at 130 deg. C. This result indicates that over-heating does not modify the mechanical properties of the coating.

  16. Atomic force microscopy study of the rabbit skeletal muscle ryanodine receptors in different functional states

    Institute of Scientific and Technical Information of China (English)

    WEI; Qingqing(魏青青); CHENG; Xiaoyang(程晓阳); CHEN; Keying(陈克樱); HU; Jun(胡钧); LI; Minqian(李民乾); ZHU; Peihong(朱培闳)

    2002-01-01

    Atomic force microscope was applied to investigate the effect of extrinsic phospholipid on the structure of rabbit skeletal muscle ryanodine receptor/calcium release channel (RyR1). In addition, in the presence of extrinsic phospholipid, the height and elasticity of the RyR1s in different functional states were also measured. The results indicate: (i) most of the RyR1s showed a normal structure only in the presence of extrinsic phospholipid; (ii) treatment of the RyR1s with AMP and Ca2+ together could increase their Young's Modulus but not change their apparent height; (iii) no detectable change in either height or Young's Modulus of the RyR1s appeared, if the RyR1s were treated with other activators or inhibitors.

  17. Mechanical stimulation of individual stereocilia of living cochlear hair cells by atomic force microscopy.

    Science.gov (United States)

    Langer, M G; Koitschev, A; Haase, H; Rexhausen, U; Hörber, J K; Ruppersberg, J P

    2000-02-01

    This paper describes the investigation of elastical properties and imaging of living cochlear hair bundles of inner (IHC) and outer hair cells (OHC) on the level of individual stereocilia. A custom-made AFM-setup was used, allowing to scan the mechano-sensitive structures of the inner ear under direct control of an upright differential interference contrast (DIC) microscope with a water-immersion objective. Scanning electron microscopy (SEM) images of the identical hair bundles obtained after AFM investigation demonstrated that forces up to 1.5 nanonewton (nN) did not cause obvious damage of the surface morphology of the stereocilia. These are the first images of hair bundles of living sensory cells of the organ of Corti by AFM. They display the tips of individual stereocilia and the typical V-shape of ciliary bundles. Since line scans clearly show that slope and force interaction depend on the elastical properties of stereocilia, quantitative stiffness measurements and stimulation of single transduction channels are suggested. PMID:10741679

  18. High-speed atomic force microscopy for large scan sizes using small cantilevers

    Science.gov (United States)

    Braunsmann, Christoph; Schäffer, Tilman E.

    2010-06-01

    We present a high-speed atomic force microscope that exhibits a number of practical advantages over previous designs. Its central component is a high-speed scanner with a maximum scan size of 23 µm × 23 µm and a conveniently large sample stage area (6.5 mm × 6.5 mm). In combination with small cantilevers, image rates of up to 46 images s - 1 in air and 13 images s - 1 in liquid are reached under z-feedback control. By large scan size imaging of collagen fibrils in air, sample velocities of 8.8 mm s - 1 in the xy-direction and 11 mm s - 1 in the z-direction are reached. To provide optimized imaging conditions for both large and small scan sizes, a modular scanner design allows easily exchanging the x- and y-piezos. The scanner is therefore also suited for investigations on the molecular and atomic scale, which is demonstrated by imaging the step dynamics of a calcite surface during dissolution and the hexagonal lattice of a mica surface in liquid.

  19. Probing the elastic response of microalga Scenedesmus dimorphus in dry and aqueous environments through atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Warren, K. M.; Mpagazehe, J. N.; Higgs, C. F., E-mail: prl@andrew.cmu.edu, E-mail: higgs@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213 (United States); LeDuc, P. R., E-mail: prl@andrew.cmu.edu, E-mail: higgs@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213 (United States); Departments of Biomedical Engineering and Biological Sciences, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213 (United States)

    2014-10-20

    With the re-emergence of microalgae as a replacement feedstock for petroleum-derived oils, researchers are working to understand its chemical and mechanical behavior. In this work, the mechanical properties of microalgae, Scenedesmus dimorphus, were investigated at the subcellular level to determine the elastic response of cells that were in an aqueous and dried state using nano-scale indentation through atomic force microscopy. The elastic modulus of single-celled S. dimorphus cells increased over tenfold from an aqueous state to a dried state, which allows us to better understand the biophysical response of microalgae to stress.

  20. Electric transport through nanometric CoFe2O4 thin films investigated by conducting atomic force microscopy

    International Nuclear Information System (INIS)

    A systematic study of electric transport through thin (2-8 nm) CoFe2O4 films deposited on epitaxial SrRuO3 bottom electrodes was performed by conducting atomic force microscopy (CAFM). Experimental procedures to investigate transport through thin insulating films by CAFM are critically revised, and the potential of CoFe2O4 films for the use as spin-filtering barriers is assessed. It is concluded that, at room-temperature, a non-tunnel channel significantly contributes to the electric transport, thus limiting the spin-filtering efficiency.