WorldWideScience

Sample records for atomic force microscopy-based

  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. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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)

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Atomic force microscopy-based antibody recognition imaging of proteins in the pathological deposits in Pseudoexfoliation Syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Creasey, Rhiannon [School of Chemical and Physical Sciences, Flinders University of SA, GPO Box 2100, Adelaide, SA 5001 (Australia); Sharma, Shiwani [School of Medicine, Ophthalmology, Flinders University of SA, GPO Box 2100, Adelaide, SA 5001 (Australia); Gibson, Christopher T. [School of Chemical and Physical Sciences, Flinders University of SA, GPO Box 2100, Adelaide, SA 5001 (Australia); Craig, Jamie E. [School of Medicine, Ophthalmology, Flinders University of SA, GPO Box 2100, Adelaide, SA 5001 (Australia); Ebner, Andreas [Institute for Biophysics, Johannes Kepler Universitaet Linz, Altenbergerstr. 69, A-4040 Linz (Austria); Becker, Thomas [Nanochemistry Research Institute, Curtin University, GPO Box U1987, Perth, 6845 WA (Australia); Hinterdorfer, Peter [Institute for Biophysics, Johannes Kepler Universitaet Linz, Altenbergerstr. 69, A-4040 Linz (Austria); Voelcker, Nicolas H., E-mail: nico.voelcker@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University of SA, GPO Box 2100, Adelaide, SA 5001 (Australia)

    2011-07-15

    The phenomenon of protein aggregation is of considerable interest to various disciplines, including the field of medicine. A range of disease pathologies are associated with this phenomenon. One of the ocular diseases hallmarked by protein aggregation is the Pseudoexfoliation (PEX) Syndrome. This condition is characterized by the deposition of insoluble proteinaceous material on the anterior human lens capsule. Genomic and proteomic analyses have revealed an association of specific genetic markers and various proteins, respectively, with PEX syndrome. However, the ultrastructure of the protein aggregates is poorly characterized. This study seeks to build capacity to determine the molecular nature of PEX aggregates on human lens capsules in their native state by AFM-based antibody recognition imaging. Lysyl oxidase-Like 1 (LOXL1), a protein identified as a component of PEX aggregates, is detected by an antibody-modified AFM probe. Topographical AFM images and antibody recognition images are obtained using three AFM-based techniques: TREC, phase and force-volume imaging. LOXL1 is found to be present on the lens capsule surface, and is localized around fibrous protein aggregates. Our evaluation shows that TREC imaging is best suited for human tissue imaging and holds significant potential for imaging of human disease tissues in their native state. -- Highlights: {yields} Atomic force microscopy techniques were applied to diseased human tissues. {yields} LOXL1 protein was detected on the small fibers of Pseudoexfoliation deposits. {yields} PicoTREC was the optimum technique for investigating protein aggregates.

  19. Interaction force microscopy based on quartz tuning fork force sensor

    Science.gov (United States)

    Qin, Yexian

    The ability to sense small changes in the interaction force between a scanning probe microscope (SPM) tip and a substrate requires cantilevers with a sharp mechanical resonance. A typical commercially available cantilever in air is characterized by a resonance with a Q factor of 100 ˜ 300. The low Q factor can be attributed to imperfections in the cantilever itself as well as damping effects of the surrounding air. To substantially increase the Q factor, novel concepts are required. For this reason, we have performed a systematic study of quartz tuning fork resonators for possible use with SPMs. We find that tuning fork resonators operating in air are characterized by Q factors in the order of 104, thereby greatly improving the SPM's ability to measure small shifts in the interaction force. By carefully attaching commercially available SPM tips to the tuning fork, it is possible to obtain SPM images using non-contact imaging techniques and analyze the tip-sample interactions. The assembly of uniform molecular monolayers on atomically flat substrates for molecular electronics applications has received widespread attention during the past ten years. Scanning probe techniques are often used to assess substrate topography, molecular ordering and electronic properties, yet little is known about the fundamental tip-molecule interaction. To address this issue we have built an Interaction Force Microscope using a quartz tuning fork to probe tip-molecular monolayer interactions using scanning probe microscopy. The high quality factor and stable resonant frequency of a quartz tuning fork allows accurate measurement of small shifts in the resonant frequency as the tip interacts with the substrate. To permit an accurate measure of surface interaction forces, the electrical and piezomechanical properties of a tuning fork have been calibrated using a fiber optical interferometer. In prior work [1], we have studied molecular layers formed from either 4-Trifluoro

  20. Carbon fibre tips for scanning probe microscopy based on quartz tuning fork force sensors

    Energy Technology Data Exchange (ETDEWEB)

    Castellanos-Gomez, A; Agrait, N; 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)

    2010-04-09

    We report the fabrication and the characterization of carbon fibre tips for use in combined scanning tunnelling and force microscopy based on piezoelectric quartz tuning fork force sensors. We find that the use of carbon fibre tips results in a minimum impact on the dynamics of quartz tuning fork force sensors, yielding a high quality factor and, consequently, a high force gradient sensitivity. This high force sensitivity, in combination with high electrical conductivity and oxidation resistance of carbon fibre tips, make them very convenient for combined and simultaneous scanning tunnelling microscopy and atomic force microscopy measurements. Interestingly, these tips are quite robust against occasionally occurring tip crashes. An electrochemical fabrication procedure to etch the tips is presented that produces a sub-100-nm apex radius in a reproducible way which can yield high resolution images.

  1. 基于原子力显微镜的单分子力谱在生物研究中的应用%Application of Atomic Force Microscopy Based Single Molecule Force Spectroscopy in Biological Research

    Institute of Scientific and Technical Information of China (English)

    黎虹颖; 古宁宇; 唐纪琳

    2012-01-01

    Atomic force microscopy(AFM) is widely used in biological research,AFM based single molecule force spectroscopy can be applied to study the intramolecular and intermolecular interactions of biomolecules at the single-molecule and single-cell levels.In this paper,we present the latest progress of AFM based single molecule force spectroscopy in biomolecular interaction,protein unfolding,cell surface biomolecules,cell mechanical properties and single molecule force spectroscopy imaging.%原子力显微镜被广泛应用于生物研究领域,基于原子力显微镜的单分子力谱可以在单分子、单细胞水平上研究生物分子内和分子间的相互作用.本文介绍了原子力显微镜单分子力谱在生物分子间相互作用、蛋白质去折叠、细胞表面生物分子、细胞力学性质和基于单分子力谱成像等研究中的最新进展.

  2. Noncontact scanning force microscopy based on a modified tuning fork sensor

    Science.gov (United States)

    Göttlich, Hagen; Stark, Robert W.; Pedarnig, Johannes D.; Heckl, Wolfgang M.

    2000-08-01

    Distance control using a tuning fork setup for the detection of shear forces is a standard configuration in scanning near-field optical microscopy (SNOM). Based on this concept, a modified sensor was developed, where a standard silicon tip for atomic force microscopy (AFM) is attached to the front end of one prong of a 100 kHz quartz tuning fork oscillator. Comparison of force curves of a standard tapping-mode AFM cantilever, a conventional fiber tip SNOM sensor and the novel AFM tip shear force sensor demonstrate an enhanced stability and sensitivity of the new sensor. Due to the rigid sensor design the force curves of the AFM tip shear force sensor indicate a perfect noncontact behavior under normal conditions in air. Noncontact images show a comparable resolution to conventional force microscopy.

  3. Atomic Force Microscope

    Energy Technology Data Exchange (ETDEWEB)

    Day, R.D.; Russell, P.E.

    1988-12-01

    The Atomic Force Microscope (AFM) is a recently developed instrument that has achieved atomic resolution imaging of both conducting and non- conducting surfaces. Because the AFM is in the early stages of development, and because of the difficulty of building the instrument, it is currently in use in fewer than ten laboratories worldwide. It promises to be a valuable tool for obtaining information about engineering surfaces and aiding the .study of precision fabrication processes. This paper gives an overview of AFM technology and presents plans to build an instrument designed to look at engineering surfaces.

  4. Atomic Force Microscope Operation

    Science.gov (United States)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation (large file) This animation is a scientific illustration of the operation of NASA's Phoenix Mars Lander's Atomic Force Microscope, or AFM. The AFM is part of Phoenix's Microscopy, Electrochemistry, and Conductivity Analyzer, or MECA. The AFM is used to image the smallest Martian particles using a very sharp tip at the end of one of eight beams. The beam of the AFM is set into vibration and brought up to the surface of a micromachined silicon substrate. The substrate has etched in it a series of pits, 5 micrometers deep, designed to hold the Martian dust particles. The microscope then maps the shape of particles in three dimensions by scanning them with the tip. At the end of the animation is a 3D representation of the AFM image of a particle that was part of a sample informally called 'Sorceress.' The sample was delivered to the AFM on the 38th Martian day, or sol, of the mission (July 2, 2008). The image shows four round pits, only 5 microns in depth, that were micromachined into the silicon substrate. A Martian particle only one micrometer, or one millionth of a meter, across is held in the upper left pit. The rounded particle shown at the highest magnification ever seen from another world is a particle of the dust that cloaks Mars. Such dust particles color the Martian sky pink, feed storms that regularly envelop the planet and produce Mars' distinctive red soil. The AFM was developed by a Swiss-led consortium, with Imperial College London producing the silicon substrate that holds sampled particles. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  5. Atom location using scanning transmission electron microscopy based on electron energy loss spectroscopy

    International Nuclear Information System (INIS)

    Full text: The technique of atom location by channelling enhanced microanalysis (ALCHEMI) using cross section data, measured as a function of electron beam orientation, has been widely implemented by many researchers. The accurate application of ALCHEMI, usually based on energy dispersive x-ray analysis (EDX), requires knowledge, from first principles, of the relative delocalization of the inner-shell ionization interaction (see for example Oxley and Allen, 1998; Oxley et al., 1999). Scanning transmission electron microscopy (STEM) based on electron energy loss spectroscopy (EELS) also provides information about the location of atoms of different types within the crystal lattice. Unlike high angle annular dark field (HAADF), EELS provides a unique signal for each atom type. In conjunction with highly focused probes, allowing near atomic resolution, this makes possible, in principle, the application of ALCHEMI like techniques to STEM images to determine the distribution of impurities within the unit cell. The accurate interpretation of STEM results requires that both the inner-shell ionization interaction and resulting ionization cross section or image be correctly modelled. We present model calculations demonstrating the in principle application of ALCHEMI type techniques to STEM images pertinent to EELS. The inner-shell ionisation interaction is modelled using Hartree-Fock wave functions to describe the atomic bound states and Hartree-Slater wave functions to describe the continuum states. The wave function within the crystal is calculated using boundary conditions appropriate for a highly focussed probe (Rossouw and Allen, 2001) and STEM images or ionisation cross sections are simulated using an inelastic cross section formulation that correctly accounts for the contribution from both dynamical electrons and those dechannelled by absorptive scattering processes such as thermal diffuse scattering (TDS). Copyright (2002) Australian Society for Electron Microscopy

  6. Coaxial atomic force microscope tweezers

    Science.gov (United States)

    Brown, K. A.; Aguilar, J. A.; Westervelt, R. M.

    2010-03-01

    We demonstrate coaxial atomic force microscope (AFM) tweezers that can trap and place small objects using dielectrophoresis (DEP). An attractive force is generated at the tip of a coaxial AFM probe by applying a radio frequency voltage between the center conductor and a grounded shield; the origin of the force is found to be DEP by measuring the pull-off force versus applied voltage. We show that the coaxial AFM tweezers can perform three-dimensional assembly by picking up a specified silica microsphere, imaging with the microsphere at the end of the tip, and placing it at a target destination.

  7. Coaxial Atomic Force Microscope Tweezers

    CERN Document Server

    Brown, K A; Westervelt, R M

    2010-01-01

    We demonstrate coaxial atomic force microscope (AFM) tweezers that can trap and place small objects using dielectrophoresis (DEP). An attractive force is generated at the tip of a coaxial AFM probe by applying a radio frequency voltage between the center conductor and a grounded shield; the origin of the force is found to be DEP by measuring the pull-off force vs. applied voltage. We show that the coaxial AFM tweezers (CAT) can perform three dimensional assembly by picking up a specified silica microsphere, imaging with the microsphere at the end of the tip, and placing it at a target destination.

  8. 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…

  9. Sensing mode atomic force microscope

    Science.gov (United States)

    Hough, Paul V. C.; Wang, Chengpu

    2003-01-01

    An atomic force microscope utilizes a pulse release system and improved method of operation to minimize contact forces between a probe tip affixed to a flexible cantilever and a specimen being measured. The pulse release system includes a magnetic particle affixed proximate the probe tip and an electromagnetic coil. When energized, the electromagnetic coil generates a magnetic field which applies a driving force on the magnetic particle sufficient to overcome adhesive forces exhibited between the probe tip and specimen. The atomic force microscope includes two independently displaceable piezo elements operable along a Z-axis. A controller drives the first Z-axis piezo element to provide a controlled approach between the probe tip and specimen up to a point of contact between the probe tip and specimen. The controller then drives the first Z-axis piezo element to withdraw the cantilever from the specimen. The controller also activates the pulse release system which drives the probe tip away from the specimen during withdrawal. Following withdrawal, the controller adjusts the height of the second Z-axis piezo element to maintain a substantially constant approach distance between successive samples.

  10. 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

  11. 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

  12. Hyperbaric hydrothermal atomic force microscope

    Science.gov (United States)

    Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

    2002-01-01

    A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

  13. Atomic Force Microscope Mediated Chromatography

    Science.gov (United States)

    Anderson, Mark S.

    2013-01-01

    The atomic force microscope (AFM) is used to inject a sample, provide shear-driven liquid flow over a functionalized substrate, and detect separated components. This is demonstrated using lipophilic dyes and normal phase chromatography. A significant reduction in both size and separation time scales is achieved with a 25-micron-length column scale, and one-second separation times. The approach has general applications to trace chemical and microfluidic analysis. The AFM is now a common tool for ultra-microscopy and nanotechnology. It has also been demonstrated to provide a number of microfluidic functions necessary for miniaturized chromatography. These include injection of sub-femtoliter samples, fluidic switching, and sheardriven pumping. The AFM probe tip can be used to selectively remove surface layers for subsequent microchemical analysis using infrared and tip-enhanced Raman spectroscopy. With its ability to image individual atoms, the AFM is a remarkably sensitive detector that can be used to detect separated components. These diverse functional components of microfluidic manipulation have been combined in this work to demonstrate AFM mediated chromatography. AFM mediated chromatography uses channel-less, shear-driven pumping. This is demonstrated with a thin, aluminum oxide substrate and a non-polar solvent system to separate a mixture of lipophilic dyes. In conventional chromatographic terms, this is analogous to thin-layer chromatography using normal phase alumina substrate with sheardriven pumping provided by the AFM tip-cantilever mechanism. The AFM detection of separated components is accomplished by exploiting the variation in the localized friction of the separated components. The AFM tip-cantilever provides the mechanism for producing shear-induced flows and rapid pumping. Shear-driven chromatography (SDC) is a relatively new concept that overcomes the speed and miniaturization limitations of conventional liquid chromatography. SDC is based on a

  14. Atomic Force Controlled Capillary Electrophoresis

    Science.gov (United States)

    Lewis, Aaron; Yeshua, Talia; Palchan, Mila; Lovsky, Yulia; Taha, Hesham

    2010-03-01

    Lithography based on scanning probe microscopic techniques has considerable potential for accurate & localized deposition of material on the nanometer scale. Controlled deposition of metallic features with high purity and spatial accuracy is of great interest for circuit edit applications in the semiconductor industry, for plasmonics & nanophotonics and for basic research in surface enhanced Raman scattering & nanobiophysics. Within the context of metal deposition we will review the development of fountain pen nanochemistry and its most recent emulation Atomic Force Controlled Capillary Electrophoresis (ACCE). Using this latter development we will demonstrate achievement of unprecedented control of nanoparticle deposition using a three-electrode geometry. Three electrodes are attached: one on the outside of a metal coated glass probe, one on the inside of a hollow probe in a solution containing Au nanoparticles in the capillary, and a third on the surface where the writing takes place. The three electrodes provide electrical pulses for accurate control of deposition and retraction of the liquid from the surface overcoming the lack of control seen in both dip pen lithography & fountain pen nanochemistry when the tip contacts the surface. With this development, we demonstrate depositing a single 1.3 nm Au nanoparticle onto surfaces such as semiconductors.

  15. Casimir-Polder forces on moving atoms

    CERN Document Server

    Scheel, Stefan

    2009-01-01

    Polarisable atoms and molecules experience the Casimir-Polder force near magnetoelectric bodies, a force that is induced by quantum fluctuations of the electromagnetic field and the matter. Atoms and molecules in relative motion to a magnetoelectric surface experience an additional, velocity-dependent force. We present a full quantum-mechanical treatment of this force and identify a generalised Doppler effect, the time delay between photon emission and reabsorption, and the Roentgen interaction as its three sources. For ground-state atoms, the force is very small and always decelerating, hence commonly known as quantum friction. For atom and molecules in electronically excited states, on the contrary, both decelerating and accelerating forces can occur depending on the magnitude of the atomic transition frequency relative to the surface plasmon frequency.

  16. Introduction to light forces, atom cooling, and atom trapping

    OpenAIRE

    Savage, Craig,

    1995-01-01

    This paper introduces and reviews light forces, atom cooling and atom trapping. The emphasis is on the physics of the basic processes. In discussing conservative forces the semi-classical dressed states are used rather than the usual quantized field dressed states.

  17. Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

    OpenAIRE

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.

    2005-01-01

    The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-di...

  18. 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...

  19. 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

  20. 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

  1. Imaging spectroscopy with the atomic force microscope

    OpenAIRE

    Baselt, David R.; Baldeschwieler, John D.

    1994-01-01

    Force curve imaging spectroscopy involves acquiring a force-distance curve at each pixel of an atomic force microscope image. Processing of the resulting data yields images of sample hardness and tip-sample adhesion. These images resemble Z modulation images and the sum of forward and reverse friction images, respectively, and like them exhibit a number of potentially misleading contrast mechanisms. In particular, XY tip motion has a pronounced effect on hardness images and the meniscus force...

  2. 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.

  3. 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...

  4. 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

  5. Measuring Forces between Oxide Surfaces Using the Atomic Force Microscope

    DEFF Research Database (Denmark)

    Pedersen, Henrik Guldberg; Høj, Jakob Weiland

    1996-01-01

    The interactions between colloidal particles play a major role in processing of ceramics, especially in casting processes. With the Atomic Force Microscope (AFM) it is possible to measure the inter-action force between a small oxide particle (a few micron) and a surface as function of surface...

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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...

  11. 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.

  12. 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

  13. 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.

  14. Electrical Analogy to an Atomic Force Microscope

    Directory of Open Access Journals (Sweden)

    O. Kucera

    2010-04-01

    Full Text Available Several applications of the atomic force microscopy (AFM, such as measurement of soft samples, manipulation with molecules, etc., require mechanical analysis of the AFM probe behavior. In this article we suggest the electrical circuit analogy to AFM cantilever tip motion. Well developed circuit theories in connection with fairly accessible software for circuit analysis make this alternative method easy to use for a wide community of AFM users.

  15. First Atomic Force Microscope Image from Mars

    Science.gov (United States)

    2008-01-01

    This calibration image presents three-dimensional data from the atomic force microscope on NASA's Phoenix Mars Lander, showing surface details of a substrate on the microscope station's sample wheel. It will be used as an aid for interpreting later images that will show shapes of minuscule Martian soil particles. The area imaged by the microscope is 40 microns by 40 microns, small enough to fit on an eyelash. The grooves in this substrate are 14 microns (0.00055 inch) apart, from center to center. The vertical dimension is exaggerated in the image to make surface details more visible. The grooves are 300 nanometers (0.00001 inch) deep. This is the first atomic force microscope image recorded on another planet. It was taken on July 9, 2008, during the 44th Martian day, or sol, of the Phoenix mission since landing. Phoenix's Swiss-made atomic force microscope builds an image of the surface shape of a particle by sensing it with a sharp tip at the end of a spring, all microfabricated out of a silicon wafer. A strain gauge records how far the spring flexes to follow the contour of the surface. It can provide details of soil-particle shapes smaller than one-hundredth the width of a human hair. This is about 20 times smaller than what can be resolved with Phoenix's optical microscope, which has provided much higher-magnification imaging than anything seen on Mars previously. Both microscopes are part of Phoenix's Microscopy, Electrochemistry and Conductivity Analyzer.

  16. 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.

  17. 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.

  18. 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

  19. Friction forces on atoms after acceleration

    International Nuclear Information System (INIS)

    The aim of this paper is to revisit the calculation of atom–surface quantum friction in the quantum field theory formulation put forward by Barton (2010 New J. Phys. 12 113045). We show that the power dissipated into field excitations and the associated friction force depend on how the atom is boosted from being initially at rest to a configuration in which it is moving at constant velocity (v) parallel to the planar interface. In addition, we point out that there is a subtle cancellation between the one-photon and part of the two-photon dissipating power, resulting in a leading order contribution to the frictional power which goes as v4. These results are also confirmed by an alternative calculation of the average radiation force, which scales as v3. (paper)

  20. Rectified optical force on dark-state atoms

    Science.gov (United States)

    Korsunsky, E. A.; Kosachiov, D. V.

    1997-12-01

    We show that an imperfection of velocity-selective coherent population trapping (VSCPT) in three-level atoms excited by standing light waves causes a rectified force on cooled atoms. The rectified force as well as the cooling force are calculated both analytically and numerically for 0953-4075/30/24/010/img5 and cascade three-level systems. Combination of these forces with the VSCPT mechanism can lead to localization of very cold atoms in potential wells created by the rectified force. This effect should be taken into account in experiments with VSCPT in standing waves, and can be used for realizing superlattices of cold atoms, in particular, cold Rydberg atoms.

  1. 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.

  2. 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

  3. 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

  4. 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).

  5. 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.

  6. Sharp Tips on the Atomic Force Microscope

    Science.gov (United States)

    2008-01-01

    This image shows the eight sharp tips of the NASA's Phoenix Mars Lander's Atomic Force Microscope, or AFM. The AFM is part of Phoenix's Microscopy, Electrochemistry, and Conductivity Analyzer, or MECA. The microscope maps the shape of particles in three dimensions by scanning them with one of the tips at the end of a beam. For the AFM image taken, the tip at the end of the upper right beam was used. The tip pointing up in the enlarged image is the size of a smoke particle at its base, or 2 microns. This image was taken with a scanning electron microscope before Phoenix launched on August 4, 2007. The AFM was developed by a Swiss-led consortium in collaboration with Imperial College London. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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)

  18. 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

  19. Dissipation and oscillatory solvation forces in confined liquids studied by small-amplitude atomic force spectroscopy

    NARCIS (Netherlands)

    Beer, de Sissi; Ende, van den Dirk; Mugele, Frieder

    2010-01-01

    We determine conservative and dissipative tip–sample interaction forces from the amplitude and phase response of acoustically driven atomic force microscope (AFM) cantilevers using a non-polar model fluid (octamethylcyclotetrasiloxane, which displays strong molecular layering) and atomically flat su

  20. 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...

  1. 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.

  2. 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.

  3. Study of adhesive forces on a silicon nanotip by atomic force microscope in contact mode

    Science.gov (United States)

    Agache, Vincent; Legrand, Bernard; Collard, Dominique; Buchaillot, Lionel

    2002-04-01

    Atomic Force Microscope operating in contact mode is used in this paper for probing the spatial distribution of adhesive forces versus the topography of a silicon nanotip. This nanotip consists in an ultra sha4rp silicon tip with radius less than 15 nm fabricated using a combination of high- resolution electron beam lithography and plasma dry etching. The amplitude of the forces is determined from force versus distance curve measurements. Hence, by determining the contact point and the pull-off force from the force curves, the surface topography and the adhesive forces are simultaneously obtained at various locations on the surface. This paper reports both measurements and the modeling of adhesive forces versus the contact point on the nanotip. As the nanotip is sharper and has got a smaller aperture angle than the employed Atomic Force Microscope tip, the measurements are focused on the nanotip apex.

  4. Adhesive forces investigation on a silicon tip by contact-mode atomic force microscope

    Science.gov (United States)

    Agache, Vincent; Legrand, Bernard; Collard, Dominique; Buchaillot, Lionel

    2002-09-01

    An atomic force microscope operating in contact mode is used in this letter for probing the adhesive forces at the apex of a silicon nanotip with typical radius smaller than 15 nm, fabricated using a combination of high-resolution electron beam lithography and plasma dry etching. The amplitude of the forces is deduced from force versus distance curve measurements. By determining the contact point and the pull-off force from the force curves, the surface topography and the adhesive forces are simultaneously obtained at various locations on the surface. This letter reports both measurements and modeling of adhesive forces versus the contact point on the nanotip. As the nanotip is sharper and has a smaller aperture angle than the employed atomic force microscope tip, the measurements are focused on the nanotip apex.

  5. 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, ...

  6. Manipulation of cadmium selenide nanorods with an atomic force microscope

    International Nuclear Information System (INIS)

    We have used an atomic force microscope (AFM) to manipulate and study ligand-capped cadmium selenide nanorods deposited on highly oriented pyrolitic graphite (HOPG). The AFM tip was used to manipulate (i.e., translate and rotate) the nanorods by applying a force perpendicular to the nanorod axis. The manipulation result was shown to depend on the point of impact of the AFM tip with the nanorod and whether the nanorod had been manipulated previously. Forces applied parallel to the nanorod axis, however, did not give rise to manipulation. These results are interpreted by considering the atomic-scale interactions of the HOPG substrate with the organic ligands surrounding the nanorods. The vertical deflection of the cantilever was recorded during manipulation and was combined with a model in order to estimate the value of the horizontal force between the tip and nanorod during manipulation. This horizontal force is estimated to be on the order of a few tens of nN.

  7. 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

  8. 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...

  9. 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

  10. Edge Effects and Coupling Effects in Atomic Force Microscope Images

    Institute of Scientific and Technical Information of China (English)

    ZHANGXiang-jun; MENGYong-gang; WENShi-zhu

    2004-01-01

    The AFM images were obtained by an atomic force microscope (AFM) and transformed from the deformation of AFM micro cantilever probe. However, due to the surface topography and surface forces applied on the AFM tip of sample, the deformation of AFM probe results in obvious edge effects and coupling effects in the AFM images. The deformation of AFM probe was analyzed,the mechanism of the edge effects and the coupling effects was investigated, and their results in the AFM images were studied. It is demanstrated by the theoretical analysis and AFM experiments that the edge effects make lateral force images more clear than the topography images, also make extraction of frictional force force from lateral force images mare complex and difficult. While the coupling effects make the comparison between topography images and lateral force images mare advantage to acquire precise topography information by AFM.

  11. 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.

  12. 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...

  13. Nonequilibrium Atom-Dielectric Forces Mediated by a Quantum Field

    OpenAIRE

    Behunin, Ryan Orson; Hu, Bei-Lok

    2011-01-01

    In this paper we give a first principles microphysics derivation of the nonequilibrium forces between an atom, treated as a three dimensional harmonic oscillator, and a bulk dielectric medium modeled as a continuous lattice of oscillators coupled to a reservoir. We assume no direct interaction between the atom and the medium but there exist mutual influences transmitted via a common electromagnetic field. By employing concepts and techniques of open quantum systems we introduce coarse-grainin...

  14. 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.

  15. 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…

  16. Learning scheme to predict atomic forces and accelerate materials simulations

    Science.gov (United States)

    Botu, V.; Ramprasad, R.

    2015-09-01

    The behavior of an atom in a molecule, liquid, or solid is governed by the force it experiences. If the dependence of this vectorial force on the atomic chemical environment can be learned efficiently with high fidelity from benchmark reference results—using "big-data" techniques, i.e., without resorting to actual functional forms—then this capability can be harnessed to enormously speed up in silico materials simulations. The present contribution provides several examples of how such a force field for Al can be used to go far beyond the length-scale and time-scale regimes presently accessible using quantum-mechanical methods. It is argued that pathways are available to systematically and continuously improve the predictive capability of such a learned force field in an adaptive manner, and that this concept can be generalized to include multiple elements.

  17. Properties of Atoms in Molecules:  Caged Atoms and the Ehrenfest Force.

    Science.gov (United States)

    Bader, Richard F W; Fang, De-Cai

    2005-05-01

    This paper uses the properties of atom X enclosed within an adamantane cage, denoted by X@C10H16, as a vehicle to introduce the Ehrenfest force into the discussion of bonding, the properties being determined by the physics of an open system. This is the force acting on an atom in a molecule and determining the potential energy appearing in Slater's molecular virial theorem. The Ehrenfest force acting across the interatomic surface of a bonded pair atoms [Formula: see text] atoms linked by a bond path [Formula: see text] is attractive, each atom being drawn toward the other, and the associated surface virial that measures the contribution to the energy arising from the formation of the surface is stabilizing. It is the Ehrenfest force that determines the adhesive properties of surfaces. The endothermicity of formation for X = He or Ne is not a result of instabilities incurred in the interaction of X with the four methine carbons to which it is bonded, interactions that are stabilizing both in terms of the changes in the atomic energies and in the surface virials. The exothermicity for X = Be(2+), B(3+), and Al(3+) is a consequence of the transfer of electron density from the hydrogen atoms to the carbon and X atoms, the exothermicity increasing with charge transfer despite an increase in the contained volume of X. PMID:26641507

  18. Properties of Atoms in Molecules:  Caged Atoms and the Ehrenfest Force.

    Science.gov (United States)

    Bader, Richard F W; Fang, De-Cai

    2005-05-01

    This paper uses the properties of atom X enclosed within an adamantane cage, denoted by X@C10H16, as a vehicle to introduce the Ehrenfest force into the discussion of bonding, the properties being determined by the physics of an open system. This is the force acting on an atom in a molecule and determining the potential energy appearing in Slater's molecular virial theorem. The Ehrenfest force acting across the interatomic surface of a bonded pair atoms [Formula: see text] atoms linked by a bond path [Formula: see text] is attractive, each atom being drawn toward the other, and the associated surface virial that measures the contribution to the energy arising from the formation of the surface is stabilizing. It is the Ehrenfest force that determines the adhesive properties of surfaces. The endothermicity of formation for X = He or Ne is not a result of instabilities incurred in the interaction of X with the four methine carbons to which it is bonded, interactions that are stabilizing both in terms of the changes in the atomic energies and in the surface virials. The exothermicity for X = Be(2+), B(3+), and Al(3+) is a consequence of the transfer of electron density from the hydrogen atoms to the carbon and X atoms, the exothermicity increasing with charge transfer despite an increase in the contained volume of X.

  19. Using Atom Interferometry to Search for New Forces

    Energy Technology Data Exchange (ETDEWEB)

    Wacker, Jay G.; /SLAC

    2009-12-11

    Atom interferometry is a rapidly advancing field and this Letter proposes an experiment based on existing technology that can search for new short distance forces. With current technology it is possible to improve the sensitivity by up to a factor of 10{sup 2} and near-future advances will be able to rewrite the limits for forces with ranges from 100 {micro}m to 1km.

  20. Quantitative Membrane Electrostatics with the Atomic Force Microscope

    OpenAIRE

    Yang, Yi; Mayer, Kathryn M.; Hafner, Jason H.

    2006-01-01

    The atomic force microscope (AFM) is sensitive to electric double layer interactions in electrolyte solutions, but provides only a qualitative view of interfacial electrostatics. We have fully characterized silicon nitride probe tips and other experimental parameters to allow a quantitative electrostatic analysis by AFM, and we have tested the validity of a simple analytical force expression through numerical simulations. As a test sample, we have measured the effective surface charge density...

  1. Large momentum transfer atom interferometry with Coriolis force compensation

    Science.gov (United States)

    Kuan, Pei-Chen; Lan, Shau-Yu; Estey, Brian; Haslinger, Philipp; Mueller, Holger

    2012-06-01

    Light-pulse atom interferometers use atom-photon interactions to coherently split, guide, and recombine freely falling matter-waves. Because of Earth's rotation, however, the matter-waves do not recombine precisely, which causes severe loss of contrast in large space-time atom interferometers. I will present our recent progress in using a tip-tilt mirror to remove the influence of the Coriolis force from Earth's rotation. Therefore, we improve the contrast and suppress systematic effects, also reach what is to our knowledge the largest spacetime area.

  2. Will a decaying atom feel a friction force?

    CERN Document Server

    Sonnleitner, Matthias; Barnett, Stephen M

    2016-01-01

    We show how a simple calculation leads to the surprising result that an excited two-level atom moving through vacuum sees a tiny friction force of first order in v/c. At first sight this seems to be in obvious contradiction to other calculations showing that the interaction with the vacuum does not change the velocity of an atom. It is yet more surprising that this change in the atom's momentum turns out to be a necessary result of energy and momentum conservation in special relativity.

  3. Cooperative scattering and radiation pressure force in dense atomic clouds

    CERN Document Server

    Bachelard, Romain; Courteille, Philippe

    2011-01-01

    We consider the collective scattering by a cloud of $N$ two-level atoms driven by an uniform radiation field. Dense atomic clouds can be described by a continuous density and the problem reduces to deriving the spectrum of the atom-atom coupling operator. For clouds much larger than the optical wavelength, the spectrum is treated as a continuum, and analytical expressions for several macroscopic quantities, such as scattered radiation intensity and radiation pressure force, are derived. The analytical results are then compared to the exact $N$-body solution and with those obtained assuming a symmetric timed Dicke state. In contrast with the symmetric timed Dicke state, our calculations takes account of the back action of the atoms on the driving field leading to phase shifts due to the finite refraction of the cloud.

  4. 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

  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. Experimental Investigation of the Velocity Effect on Adhesion Forces with an Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    魏征; 赵亚溥

    2004-01-01

    Capillary forces are significantly dominant in adhesive forces measured with an atomic force microscope (AFM)in ambient air, which are always thought to be dependent on water film thickness, relative humidity, and the free energy of water film. We study the nature of the pull-off force on a variety of surfaces as a function of tip velocity.It is found that the capillary forces are of relatively strong dependence on tip velocity. The present experiment is expected to provide a better understanding of the work mechanism of AFM in ambient air.

  7. Athermalization in atomic force microscope based force spectroscopy using matched microstructure coupling

    OpenAIRE

    Torun, H.; Finkler, O.; Degertekin, F. L.

    2009-01-01

    The authors describe a method for athermalization in atomic force microscope (AFM) based force spectroscopy applications using microstructures that thermomechanically match the AFM probes. The method uses a setup where the AFM probe is coupled with the matched structure and the displacements of both structures are read out simultaneously. The matched structure displaces with the AFM probe as temperature changes, thus the force applied to the sample can be kept constant without the need for a ...

  8. Atomic Force Analysis of Elastic Deformations of CD

    Directory of Open Access Journals (Sweden)

    A. Kuzmenko

    2013-12-01

    Full Text Available The procedure for the determination of elastic parameters according to reference nanometer lithographic marks by atomic force microscopy on samples with up to microscopic sizes is proposed. Analysis of dynamic changes of elastic characteristics that makes it possible to establish the critical rotation velocity of a CD without plastic deformations has been made.

  9. 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.

  10. 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.

  11. New approaches to atomic force microscope lithography on silicon

    DEFF Research Database (Denmark)

    Birkelund, Karen; Thomsen, Erik Vilain; Rasmussen, Jan Pihl;

    1997-01-01

    We have investigated new approaches to the formation of conducting nanowires on crystalline silicon surfaces using atomic force microscope (AFM) lithography. To increase processing speed and reduce wear of the AFM tip, large-scale structures are formed with a direct laser write setup, while the AFM...

  12. Fabrication of an all-metal atomic force microscope probe

    DEFF Research Database (Denmark)

    Rasmussen, Jan Pihl; Tang, Peter Torben; Hansen, Ole;

    1997-01-01

    This paper presents a method for fabrication of an all-metal atomic force microscope probe (tip, cantilever and support) for optical read-out, using a combination of silicon micro-machining and electroforming. The paper describes the entire fabrication process for a nickel AFM-probe. In addition...

  13. 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...

  14. 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...

  15. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-03-15

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

  17. 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.

  18. Atomic force microscope probe-based nanometric scribing

    International Nuclear Information System (INIS)

    Miniaturization of machine components is recognized by many as a significant technological development for a vast spectrum of products. An atomic force microscope (AFM) probe that can exert forces onto a variety of engineering materials is used to perform mechanical scribing at the nanoscale. The success of nanomechanical machining at such fine scales is based on the understanding of microstructural machining mechanics. This paper investigates the cutting behaviour in the nanoscale of a chromium workpiece by using a retrofitted commercial AFM with an acoustic emission sensor, in order to scratch the surface and measure forces. The calibration procedure for acquiring the forces is discussed. The cutting force model, which incorporates the flow stress and friction coefficient in the nano-scale machining, is also presented

  19. Resonant difference-frequency atomic force ultrasonic microscope

    Science.gov (United States)

    Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

    2010-01-01

    A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), 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 one of the contact resonance frequencies 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 contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

  20. Direct observation of uncoated spectrin with atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    张平城; 白春礼; 成英俊; 方晔; 冯立明; 潘华珍

    1996-01-01

    Spectrin molecules extracted from human blood ceil membrane have been examined by atomic force microscopy (AFM) without using shadowing or staining procedures. A drop of the solution containing spectrin molecules was deposited on the freshly deaved mica substrate. After about 1 min, the residual solution was removed with a piece of filter paper. Afterwards the sample was imaged with a home-made atomic force microscope (AFM) in air in a constant force mode. The obtained AFM images revealed that the spectrin molecules prepared from the above procedures exhibit several kinds of structures as follows: (i) the compact rod-like spectrin heterodimers with a length of around 100 nm; (ii) bent or curved linear tetramers with a length of around 200 nm; (iii) somewhat curved spectrin hexamers, octomers or decamers with lengths of about 300, 400, or 500 nm; and (iv) high oligomers with a length above 1 000 nm.

  1. Influence of atomic force microscope (AFM) probe shape on adhesion force measured in humidity environment

    Institute of Scientific and Technical Information of China (English)

    阳丽; 涂育松; 谭惠丽

    2014-01-01

    In micro-manipulation, the adhesion force has very important influence on behaviors of micro-objects. Here, a theoretical study on the effects of humidity on the adhesion force is presented between atomic force microscope (AFM) tips and substrate. The analysis shows that the precise tip geometry plays a critical role on humidity depen-dence of the adhesion force, which is the dominant factor in manipulating micro-objects in AFM experiments. For a blunt (paraboloid) tip, the adhesion force versus humidity curves tends to the apparent contrast (peak-to-valley corrugation) with a broad range. This paper demonstrates that the abrupt change of the adhesion force has high correla-tion with probe curvatures, which is mediated by coordinates of solid-liquid-vapor contact lines (triple point) on the probe profiles. The study provides insights for further under-standing nanoscale adhesion forces and the way to choose probe shapes in manipulating micro-objects in AFM experiments.

  2. 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...

  3. Advances in Bichromatic Force Slowing of Atoms and Molecules

    Science.gov (United States)

    Chieda, M. A.; Eyler, E. E.

    2012-06-01

    The optical bichromatic force (BCF) holds promise as an efficient, simple, and compact means to slow atoms and molecules to MOT capture velocities.ootnotetextM. Cashen and H. Metcalf, JOSA B 20, 915 (2003).^,ootnotetextM. A. Chieda and E. E. Eyler, PRA 84, 063401 (2011). Metastable helium beams, with v˜1000 m/s, are especially worthwhile atomic candidates since they presently require Zeeman slowers with lengths of 2--3 m. We present a novel BCF decelerator in which the Doppler shifts are chirped to keep the force centered on the atoms as they slow. This is made possible by recent advances in high-power diode lasers and electronics, and avoids many of the problems of alternative designs using large detunings. Initial tests on He* atoms show encouraging results. Unlike atoms, direct laser slowing of molecules remains exceedingly difficult, although success with SrF has very recently been reported.ootnotetextJ. F. Barry, E. S. Shuman, E. B. Norrgard, and D. DeMille, to be published. We calculate that for molecules with near-cycling transitions, rapid laser BCF slowing should be possible.ootnotetextChieda, op. sit. For the CaF molecule, we predict slowing by δv = 150 m/s, enough to bring a buffer-gas cooled beam to rest. An experimental demonstration is in progress.

  4. 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

  5. Influence of the Coriolis force in atom interferometry.

    Science.gov (United States)

    Lan, Shau-Yu; Kuan, Pei-Chen; Estey, Brian; Haslinger, Philipp; Müller, Holger

    2012-03-01

    In a light-pulse atom interferometer, we use a tip-tilt mirror to remove the influence of the Coriolis force from Earth's rotation and to characterize configuration space wave packets. For interferometers with a large momentum transfer and large pulse separation time, we improve the contrast by up to 350% and suppress systematic effects. We also reach what is to our knowledge the largest space-time area enclosed in any atom interferometer to date. We discuss implications for future high-performance instruments.

  6. 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.

  7. Imaging using lateral bending modes of atomic force microscope cantilevers

    Science.gov (United States)

    Caron, A.; Rabe, U.; Reinstädtler, M.; Turner, J. A.; Arnold, W.

    2004-12-01

    Using scanning probe techniques, surface properties such as shear stiffness and friction can be measured with a resolution in the nanometer range. The torsional deflection or buckling of atomic force microscope cantilevers has previously been used in order to measure the lateral forces acting on the tip. This letter shows that the flexural vibration modes of cantilevers oscillating in their width direction parallel to the sample surface can also be used for imaging. These lateral cantilever modes exhibit vertical deflection amplitudes if the cantilever is asymmetric in thickness direction, e.g., by a trapezoidal cross section.

  8. 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.

  9. Dissipative binding of atoms by non-conservative forces

    CERN Document Server

    Lemeshko, Mikhail

    2013-01-01

    The formation of molecules and supramolecular structures results from bonding by conservative forces acting among electrons and nuclei and giving rise to equilibrium configurations defined by minima of the interaction potential. Here we show that bonding can also occur by the non-conservative forces responsible for interaction-induced coherent population trapping. The bound state arises in a dissipative process and manifests itself as a stationary state at a preordained interatomic distance. Remarkably, such a dissipative bonding is present even when the interactions among the atoms are purely repulsive. The dissipative bound states can be created and studied spectroscopically in present-day experiments with ultracold atoms or molecules and can potentially serve for cooling strongly interacting quantum gases.

  10. Nanoindentation of gold nanorods with an atomic force microscope

    Science.gov (United States)

    Reischl, B.; Kuronen, A.; Nordlund, K.

    2014-12-01

    The atomic force microscope (AFM) can be used to measure mechanical properties of nanoscale objects, which are too small to be studied using a conventional nanoindenter. The contact mechanics at such small scales, in proximity of free surfaces, deviate substantially from simple continuum models. We present results from atomistic computer simulations of the indentation of gold nanorods using a diamond AFM tip and give insight in the atomic scale processes, involving creation and migration of dislocations, leading to the plastic deformation of the sample under load, and explain the force-distance curves observed for different tip apex radii of curvature, as well as different crystallographic structure and orientation of the gold nanorod samples.

  11. 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....

  12. 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)

  13. Theoretical Study on the Capillary Force between an Atomic Force Microscope Tip and a Nanoparticle

    Institute of Scientific and Technical Information of China (English)

    LI Zhao-Xia; ZHANG Li-Juan; YI Hou-Hui; FANG Hai-Ping

    2007-01-01

    @@ Considering that capillary force is one of the most important forces between nanoparticles and atomic force microscope (AFM) tips in ambient atmosphere, we develop an analytic approach on the capillary force between an AFM tip and a nanoparticle. The results show that the capillary forces are considerably affected by the geometry of the AFM tip, the humidity of the environment, the vertical distance between the AFM tip and the nanoparticle, as well as the contact angles of the meniscus with an AFM tip and a nanoparticle. It is found that the sharper the AFM tip, the smaller the capillary force. The analyses and results are expected to be helpful for the quantitative imaging and manipulating of nanoparticles by AFMs.

  14. 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.

  15. Atomic force microscopic study on lipid bilayer nanoscale phase separation

    OpenAIRE

    Liu, Rui

    2014-01-01

    Phase separation of copolymers or lipid membranes in nanoscale has attracted increasing interests for their applications in the synthesis of inorganic nanomaterial. The nanoscale phase separation of liquid bilayer as a supported membrane is systematically investigated by atomic force microscope (AFM). Moreover, the position of the fluorescence indicator, which is commonly used in the phase separation study in optical microscope, is also probed in this study to complete the knowledge of tradit...

  16. 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...

  17. 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...

  18. 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...

  19. Probing stem cell differentiation using atomic force microscopy

    Science.gov (United States)

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

    2016-03-01

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

  20. 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...

  1. Atomic force microscope observations of otoconia in the newt

    Science.gov (United States)

    Hallworth, R.; Wiederhold, M. L.; Campbell, J. B.; Steyger, P. S.

    1995-01-01

    Calcitic and aragonitic otoconia from the Japanese red-bellied newt, Cynops pyrrhogaster, were examined using an atomic force microscope. The surface structure of both otoconial polymorphs consisted of arrays of elements approximately 50 nm in diameter. Elements were generally round and were separated by shallow depressions of no more than 20 nm. The elements are suggested to be single crystals of calcium carbonate. The relationship of these observations to theories of otoconial genesis is discussed.

  2. Cooperative scattering and radiation pressure force in dense atomic clouds

    Energy Technology Data Exchange (ETDEWEB)

    Bachelard, R. [University of Nova Gorica, School of Applied Sciences, Vipavska 11c SI-5270 Ajdovscina (Slovenia); Piovella, N. [Dipartimento di Fisica, Universita Degli Studi di Milano, Via Celoria 16, I-20133 Milano (Italy); Courteille, Ph. W. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, 13560-970 Sao Carlos, SP (Brazil)

    2011-07-15

    Atomic clouds prepared in ''timed Dicke'' states, i.e. states where the phase of the oscillating atomic dipole moments linearly varies along one direction of space, are efficient sources of superradiant light emission [Scully et al., Phys. Rev. Lett. 96, 010501 (2006)]. Here, we show that, in contrast to previous assertions, timed Dicke states are not the states automatically generated by incident laser light. In reality, the atoms act back on the driving field because of the finite refraction of the cloud. This leads to nonuniform phase shifts, which, at higher optical densities, dramatically alter the cooperative scattering properties, as we show by explicit calculation of macroscopic observables, such as the radiation pressure force.

  3. 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.

  4. 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.

  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. 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

  7. Hierarchical atom type definitions and extensible all-atom force fields.

    Science.gov (United States)

    Jin, Zhao; Yang, Chunwei; Cao, Fenglei; Li, Feng; Jing, Zhifeng; Chen, Long; Shen, Zhe; Xin, Liang; Tong, Sijia; Sun, Huai

    2016-03-15

    The extensibility of force field is a key to solve the missing parameter problem commonly found in force field applications. The extensibility of conventional force fields is traditionally managed in the parameterization procedure, which becomes impractical as the coverage of the force field increases above a threshold. A hierarchical atom-type definition (HAD) scheme is proposed to make extensible atom type definitions, which ensures that the force field developed based on the definitions are extensible. To demonstrate how HAD works and to prepare a foundation for future developments, two general force fields based on AMBER and DFF functional forms are parameterized for common organic molecules. The force field parameters are derived from the same set of quantum mechanical data and experimental liquid data using an automated parameterization tool, and validated by calculating molecular and liquid properties. The hydration free energies are calculated successfully by introducing a polarization scaling factor to the dispersion term between the solvent and solute molecules. © 2015 Wiley Periodicals, Inc.

  8. Hierarchical atom type definitions and extensible all-atom force fields.

    Science.gov (United States)

    Jin, Zhao; Yang, Chunwei; Cao, Fenglei; Li, Feng; Jing, Zhifeng; Chen, Long; Shen, Zhe; Xin, Liang; Tong, Sijia; Sun, Huai

    2016-03-15

    The extensibility of force field is a key to solve the missing parameter problem commonly found in force field applications. The extensibility of conventional force fields is traditionally managed in the parameterization procedure, which becomes impractical as the coverage of the force field increases above a threshold. A hierarchical atom-type definition (HAD) scheme is proposed to make extensible atom type definitions, which ensures that the force field developed based on the definitions are extensible. To demonstrate how HAD works and to prepare a foundation for future developments, two general force fields based on AMBER and DFF functional forms are parameterized for common organic molecules. The force field parameters are derived from the same set of quantum mechanical data and experimental liquid data using an automated parameterization tool, and validated by calculating molecular and liquid properties. The hydration free energies are calculated successfully by introducing a polarization scaling factor to the dispersion term between the solvent and solute molecules. © 2015 Wiley Periodicals, Inc. PMID:26537332

  9. 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

  10. Investigation of penetration force of living cell using an atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Eun Young; Kim, Young Tae; Kim, Dae Eun [Yonsei University, Seoul (Korea, Republic of)

    2009-07-15

    Recently, the manipulation of a single cell has been receiving much attention in transgenesis, in-vitro fertilization, individual cell based diagnosis, and pharmaceutical applications. As these techniques require precise injection and manipulation of cells, issues related to penetration force arise. In this work the penetration force of living cell was studied using an atomic force microscope (AFM). L929, HeLa, 4T1, and TA3 HA II cells were used for the experiments. The results showed that the penetration force was in the range of 2{approx}22 nN. It was also found that location of cell penetration and stiffness of the AFM cantilever affected the penetration force significantly. Furthermore, double penetration events could be detected, due to the multi-membrane layers of the cell. The findings of this work are expected to aid in the development of precision micro-medical instruments for cell manipulation and treatment

  11. 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.

  12. 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.

  13. 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.

  14. Atomic force microscope study of three-dimensional nanostructure sidewalls

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Muhammad Mustafa [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States); Gondran, Carolyn F H [Advanced Technology Development Facility, 2706 Montopolis Drive, Austin, TX 78741 (United States); Michelson, Diane K [International SEMATECH Manufacturing Initiative, 2706 Montopolis Drive, Austin, TX 78741 (United States)

    2007-08-22

    Next generation planar and non-planar complementary metal oxide semiconductor (CMOS) structures are three-dimensional nanostructures with multi-layer stacks that can contain films thinner than ten atomic layers. The high resolution of transmission electron microscopy (TEM) is typically chosen for studying properties of these stacks such as film thickness, interface and interfacial roughness. However, TEM sample preparation is time-consuming and destructive, and TEM analysis is expensive and can provide problematic results for surface and interface roughness. Therefore, in this paper, we present the use of direct measurements of sidewall surface structures by conventional atomic force microscopy (AFM) as an alternative or complementary method for studying multi-layer film stacks and as the preferred method for studying FinFET sidewall surface roughness. In addition to these semiconductor device applications, this AFM sidewall measurement technique could be used for other three-dimensional nanostructures.

  15. Diagonal control design for atomic force microscope piezoelectric tube nanopositioners.

    Science.gov (United States)

    Bhikkaji, B; Yong, Y K; Mahmood, I A; Moheimani, S O R

    2013-02-01

    Atomic Force Microscopes (AFM) are used for generating surface topography of samples at micro to atomic resolutions. Many commercial AFMs use piezoelectric tube nanopositioners for scanning. Scanning rates of these microscopes are hampered by the presence of low frequency resonant modes. When inadvertently excited, these modes lead to high amplitude mechanical vibrations causing the loss of accuracy, while scanning, and eventually to break down of the tube. Feedback control has been used to damp these resonant modes. Thereby, enabling higher scanning rates. Here, a multivariable controller is designed to damp the first resonant mode along both the x and y axis. Exploiting the inherent symmetry in the piezoelectric tube, the multivariable control design problem is recast as independent single-input single-output (SISO) designs. This in conjunction with integral resonant control is used for damping the first resonant mode. PMID:23464216

  16. 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.

  17. Interlaboratory comparison of traceable atomic force microscope pitch measurements

    Science.gov (United States)

    Dixson, Ronald; Chernoff, Donald A.; Wang, Shihua; Vorburger, Theodore V.; Tan, Siew Leng; Orji, Ndubuisi G.; Fu, Joseph

    2010-06-01

    The National Institute of Standards and Technology (NIST), Advanced Surface Microscopy (ASM), and the National Metrology Centre (NMC) of the Agency for Science, Technology, and Research (A*STAR) in Singapore have completed a three-way interlaboratory comparison of traceable pitch measurements using atomic force microscopy (AFM). The specimen being used for this comparison is provided by ASM and consists of SiO2 lines having a 70 nm pitch patterned on a silicon substrate. NIST has a multifaceted program in atomic force microscope (AFM) dimensional metrology. One component of this effort is a custom in-house metrology AFM, called the calibrated AFM (C-AFM). The NIST C-AFM has displacement metrology for all three axes traceable to the 633 nm wavelength of the iodine-stabilized He-Ne laser - a recommended wavelength for realization of the SI (Système International d'Unités, or International System of Units) meter. NIST used the C-AFM to participate in this comparison. ASM used a commercially available AFM with an open-loop scanner, calibrated by a 144 nm pitch transfer standard. In a prior collaboration with Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, ASM's transfer standard was calibrated using PTB's traceable optical diffractometry instrument. Thus, ASM's measurements are also traceable to the SI meter. NMC/A*STAR used a large scanning range metrological atomic force microscope (LRM-AFM). The LRM-AFM integrates an AFM scanning head into a nano-stage equipped with three built-in He-Ne laser interferometers so that its measurement related to the motion on all three axes is directly traceable to the SI meter. The measurements for this interlaboratory comparison have been completed and the results are in agreement within their expanded uncertainties and at the level of a few parts in 104.

  18. 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.

  19. Scanned-cantilever atomic force microscope with large scanning range

    Institute of Scientific and Technical Information of China (English)

    Jintao Yang; Wendong Xu

    2006-01-01

    A scanned-cantilever atomic force microscope (AFM) with large scanning range is proposed, which adopts a new design named laser spot tracking. The scanned-cantilever AFM uses the separate flexure x-y scanner and z scanner instead of the conventional piezoelectric tube scanner. The closed-loop control and integrated capacitive sensors of these scanners can insure that the images of samples have excellent linearity and stability. According to the experimental results, the scanned-cantilever AFM can realize maximal 100 × 100 (μm) scanning range, and 1-nm resolution in z direction, which can meet the requirements of large scale sample testing.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Nonlinear control techniques for an atomic force microscope system

    Institute of Scientific and Technical Information of China (English)

    Yongchun FANG; Matthew FEEMSTER; Darren DAWSON; Nader M.JALILI

    2005-01-01

    Two nonlinear control techniques are proposed for an atomic force microscope system.Initially,a learning-based control algorithm is developed for the microcantilever-sample system that achieves asymptotic cantilever tip tracking for periodic trajectories.Specifically,the control approach utilizes a learning-based feedforward term to compensate for periodic dynamics and high-gain terms to account for non-periodic dynamics.An adaptive control algorithm is then developed to achieve asymptotic cantilever tip tracking for bounded tip trajectories despite uncertainty throughout the system parameters.Simulation results are provided to illustrate the efficacy and performance of the control strategies.

  5. Atomic force microscope characterization of a resonating nanocantilever

    DEFF Research Database (Denmark)

    Abadal, G.; Davis, Zachary James; Borrise, X.;

    2003-01-01

    An atomic force microscope (AFM) is used as a nanometer-scale resolution tool for the characterization of the electromechanical behaviour of a resonant cantilever-based mass sensor. The cantilever is actuated electrostatically by applying DC and AC voltages from a driver electrode placed closely ...... and of the oscillation amplitude on the frequency of the AC voltage is measured by this technique and the results are fitted by a simple non-linear electromechanical model. (C) 2003 Elsevier Science B.V. All rights reserved....

  6. An atomic force microscope tip as a light source

    OpenAIRE

    Lulevich, V.; Honig, Christopher D. F.; Ducker, William A.

    2005-01-01

    We present a simple method for causing the end of a silicon nitride atomic force microscope (AFM) tip to emit light, and we use this emitted light to perform scanning near-field optical microscopy. Illumination of a silicon nitride AFM tip by blue (488 nm) or green (532 nm) laser light causes the sharp part of the tip to emit orange light. Orange light is emitted when the tip is immersed in either air or water; and while under illumination, emission continues for a period of many hours withou...

  7. Fountain pen nanochemistry: Atomic force control of chrome etching

    Science.gov (United States)

    Lewis, Aaron; Kheifetz, Yuri; Shambrodt, Efim; Radko, Anna; Khatchatryan, Edward; Sukenik, Chaim

    1999-10-01

    In this report we demonstrate a general method for affecting chemical reactions with a high degree of spatial control that has potentially wide applicability in science and technology. Our technique is based on complexing the delivery of liquid or gaseous materials through a cantilevered micropipette with an atomic force microscope that is totally integrated into a conventional optical microscope. Controlled etching of chrome is demonstrated without detectable effects on the underlying glass substrate. This simple combination allows for the nanometric spatial control of the whole world of chemical reactions in defined regions of surfaces. Applications of the technique in critical areas such as mask repair are likely.

  8. 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.

  9. 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.

  10. Thermal writing using a heated atomic force microscope tip

    Science.gov (United States)

    Mamin, H. J.

    1996-07-01

    Resistive heating of an atomic force microscope tip was used to perform thermally induced surface modifications. Heating was achieved by dissipating power in the legs of an electrically conducting silicon cantilever. Temperatures of up to 170 °C were obtained using 40 mW of input power. Electrical measurements used to monitor the temperature showed thermal time constants of 0.35-0.45 ms, depending on whether the tip was in contact with a substrate. The heated tip was used to demonstrate thermomechanical writing on a polycarbonate substrate, as well as thermal writing of an optical phase change material.

  11. A Compact Vertical Scanner for Atomic Force Microscopes

    Directory of Open Access Journals (Sweden)

    Jae Hong Park

    2010-11-01

    Full Text Available A compact vertical scanner for an atomic force microscope (AFM is developed. The vertical scanner is designed to have no interference with the optical microscope for viewing the cantilever. The theoretical stiffness and resonance of the scanner are derived and verified via finite element analysis. An optimal design process that maximizes the resonance frequency is performed. To evaluate the scanner’s performance, experiments are performed to evaluate the travel range, resonance frequency, and feedback noise level. In addition, an AFM image using the proposed vertical scanner is generated.

  12. 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.

  13. 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)

  14. 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.

  15. 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.

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

    Institute of Scientific and Technical Information of China (English)

    张英鸽; 白春礼; 王琛; 赵德禄; 苏明; 林璋; 田芳

    1999-01-01

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

  17. 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

  18. MIDAS: Lessons learned from the first spaceborne atomic force microscope

    CERN Document Server

    Bentley, Mark S; Butler, Bart; Gavira, Jose; Jeszenszky, Harald; Mannel, Thurid; Romstedt, Jens; Schmied, Roland; Torkar, Klaus

    2016-01-01

    The Micro-Imaging Dust Analysis System (MIDAS) atomic force microscope (AFM) onboard the Rosetta orbiter was the first such instrument launched into space in 2004. Designed only a few years after the technique was invented, MIDAS is currently orbiting comet 67P Churyumov-Gerasimenko and producing the highest resolution 3D images of cometary dust ever made in situ. After more than a year of continuous operation much experience has been gained with this novel instrument. Coupled with operations of the Flight Spare and advances in terrestrial AFM a set of "lessons learned" has been produced, cumulating in recommendations for future spaceborne atomic force microscopes. The majority of the design could be reused as-is, or with incremental upgrades to include more modern components (e.g. the processor). Key additional recommendations are to incorporate an optical microscope to aid the search for particles and image registration, to include a variety of cantilevers (with different spring constants) and a variety of ...

  19. MIDAS: Lessons learned from the first spaceborne atomic force microscope

    Science.gov (United States)

    Bentley, Mark Stephen; Arends, Herman; Butler, Bart; Gavira, Jose; Jeszenszky, Harald; Mannel, Thurid; Romstedt, Jens; Schmied, Roland; Torkar, Klaus

    2016-08-01

    The Micro-Imaging Dust Analysis System (MIDAS) atomic force microscope (AFM) onboard the Rosetta orbiter was the first such instrument launched into space in 2004. Designed only a few years after the technique was invented, MIDAS is currently orbiting comet 67P Churyumov-Gerasimenko and producing the highest resolution 3D images of cometary dust ever made in situ. After more than a year of continuous operation much experience has been gained with this novel instrument. Coupled with operations of the Flight Spare and advances in terrestrial AFM a set of "lessons learned" has been produced, cumulating in recommendations for future spaceborne atomic force microscopes. The majority of the design could be reused as-is, or with incremental upgrades to include more modern components (e.g. the processor). Key additional recommendations are to incorporate an optical microscope to aid the search for particles and image registration, to include a variety of cantilevers (with different spring constants) and a variety of tip geometries.

  20. A comparison of dynamic atomic force microscope set-ups for performing atomic scale manipulation experiments

    International Nuclear Information System (INIS)

    We present the results of calculations performed to investigate the process of single-atom manipulation with the non-contact atomic force microscope comparing the two most common experimental set-ups: a conventional large amplitude silicon cantilever and a small amplitude quartz tuning fork. The manipulation of a model system-an oxygen vacancy in the MgO(001) surface by a single vertical approach at a fixed lateral position-is simulated for each set-up using a detailed and realistic atomistic model that accounts for temperature and the tip trajectory, and it is found that both approaches produce the manipulation event in approximately the same way. The behaviour of the tip dynamics and the resulting response of the instrumentation to the manipulation event is studied using a virtual dynamic atomic force microscope that includes a realistic description of noise for each type of set-up. The results of these calculations indicate how a single-atom manipulation can be performed and recognized by each type of experiment

  1. 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

  2. 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.

  3. 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.

  4. Scratch direction and threshold force in nanoscale scratching using atomic force microscopes

    Science.gov (United States)

    Tseng, Ampere A.; Kuo, Chung-Feng Jeffrey; Jou, Shyankay; Nishimura, Shinya; Shirakashi, Jun-ichi

    2011-09-01

    The nanoscaled tip in an AFM (atomic force microscope) has become an effective scratching tool for material removing in nanofabrication. In this article, the characteristics of using a diamond-coated pyramidal tip to scratch Ni-Fe thin film surfaces was experimentally investigated with the focus on the evaluation of the influence of the scratch or scan direction on the final shape of the scratched geometry as well as the applied scratch force. Results indicated that both the scratched profile and the scratch force were greatly affected by the scratch direction. It has been found that, to minimize the formation of protuberances along the groove sides and to have a better control of the scratched geometry, the tip face should be perpendicular to the scratching direction, which is also known as orthogonal cutting condition. To demonstrate the present findings, three groove patterns have been scratched with the tip face perpendicular to the scratching direction and very little amount of protuberances was observed. The threshold scratch force was also predicted based on the Hertz contact theory. Without considering the surface friction and adhesive forces between the tip and substrate, the threshold force predicted was twice smaller than the measurement value. Finally, recommendations for technical improvement and research focuses are provided.

  5. A new ion sensing deep atomic force microscope

    Science.gov (United States)

    Drake, Barney; Randall, Connor; Bridges, Daniel; Hansma, Paul K.

    2014-08-01

    Here we describe a new deep atomic force microscope (AFM) capable of ion sensing. A novel probe assembly incorporates a micropipette that can be used both for sensing ion currents and as the tip for AFM imaging. The key advance of this instrument over previous ion sensing AFMs is that it uses conventional micropipettes in a novel suspension system. This paper focuses on sensing the ion current passively while using force feedback for the operation of the AFM in contact mode. Two images are obtained simultaneously: (1) an AFM topography image and (2) an ion current image. As an example, two images of a MEMS device with a microchannel show peaks in the ion current as the pipette tip goes over the edges of the channel. This ion sensing AFM can also be used in other modes including tapping mode with force feedback as well as in non-contact mode by utilizing the ion current for feedback, as in scanning ion conductance microscopy. The instrument is gentle enough to be used on some biological samples such as plant leaves.

  6. A new ion sensing deep atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Drake, Barney; Randall, Connor; Bridges, Daniel; Hansma, Paul K. [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

    2014-08-15

    Here we describe a new deep atomic force microscope (AFM) capable of ion sensing. A novel probe assembly incorporates a micropipette that can be used both for sensing ion currents and as the tip for AFM imaging. The key advance of this instrument over previous ion sensing AFMs is that it uses conventional micropipettes in a novel suspension system. This paper focuses on sensing the ion current passively while using force feedback for the operation of the AFM in contact mode. Two images are obtained simultaneously: (1) an AFM topography image and (2) an ion current image. As an example, two images of a MEMS device with a microchannel show peaks in the ion current as the pipette tip goes over the edges of the channel. This ion sensing AFM can also be used in other modes including tapping mode with force feedback as well as in non-contact mode by utilizing the ion current for feedback, as in scanning ion conductance microscopy. The instrument is gentle enough to be used on some biological samples such as plant leaves.

  7. 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.

  8. A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

    OpenAIRE

    Manfred Lange; Dennis van Vörden; Rolf Möller

    2012-01-01

    Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip–sample system, and the process can be understood as a hysteresis of forces between...

  9. 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.

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

    Directory of Open Access Journals (Sweden)

    Emrecan Soylemez

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

  11. A subsurface add-on for standard atomic force microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Verbiest, G. J., E-mail: Verbiest@physik.rwth-aachen.de [JARA-FIT and II. Institute of Physics, RWTH Aachen University, 52074 Aachen (Germany); Zalm, D. J. van der; Oosterkamp, T. H.; Rost, M. J., E-mail: Rost@physics.leidenuniv.nl [Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands)

    2015-03-15

    The application of ultrasound in an Atomic Force Microscope (AFM) gives access to subsurface information. However, no commercially AFM exists that is equipped with this technique. The main problems are the electronic crosstalk in the AFM setup and the insufficiently strong excitation of the cantilever at ultrasonic (MHz) frequencies. In this paper, we describe the development of an add-on that provides a solution to these problems by using a special piezo element with a lowest resonance frequency of 2.5 MHz and by separating the electronic connection for this high frequency piezo element from all other connections. In this sense, we support researches with the possibility to perform subsurface measurements with their existing AFMs and hopefully pave also the way for the development of a commercial AFM that is capable of imaging subsurface features with nanometer resolution.

  12. 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

  13. 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.

  14. Mathematical modeling of nanomachining with atomic force microscope cantilevers

    International Nuclear Information System (INIS)

    This article theoretically analyzes the cutting depth and material removal rate of an atomic force microscope (AFM) cantilever during nanomachining. An analytical expression for the vibration frequency and displacement of the cantilever has been obtained by using the modified couple stress theory. The theory includes one additional material length scale parameter revealing the micro-scale effect. According to the analysis, the results show that the effect of size-dependent on the vibration behavior of the AFM cantilever is obvious. The maximum displacement of nanomachining with the AFM cantilever represents the cutting depth. The area under the displacement-time curve is related to the material removal rate. When the excitation frequency is closer to the nature frequency of the cantilever, a larger material removal rate is obtained

  15. Nanodot deposition and its application with atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Liu Zenglei, E-mail: liuzenglei@sia.cn; Jiao Niandong, E-mail: ndjiao@sia.cn [Chinese Academy of Sciences, State Key Laboratory of Robotics, Shenyang Institute of Automation (China); Xu Ke [Shenyang Jianzhu University (China); Wang, Zhidong [Chiba Institute of Technology (Japan); Dong Zaili; Liu Lianqing [Chinese Academy of Sciences, State Key Laboratory of Robotics, Shenyang Institute of Automation (China)

    2013-06-15

    Nanodot deposition using atomic force microscope (AFM) is investigated. To realize repeatable and precise deposition of nanodots, the detailed control method is discussed. The electric field between AFM tip and substrate is analyzed, and a convenient method to control tip-substrate separation is proposed. In experiments, two nanodot matrixes are fabricated and the heights of the nanodots are analyzed. Experimental results testify that the control method can lead to repeatable and precise fabrication of deposited nanodots. As an application of deposited nanodots, a carbon nanotube (CNT) is soldered on gold electrodes with deposited Au nanodots. After soldering, the contact resistances between the CNT and the electrodes decrease greatly. AFM-based nanodot deposition can be used to fabricate special nanopatterns; also it can be used to solder nanomaterials on substrates to improve the electrical connection, which has a promising future for nanodevice fabrication.

  16. Visualization of Cytoskeletal Elements by the Atomic Force Microscope

    CERN Document Server

    Berdyyeva, T; Sokolov, I

    2004-01-01

    We describe a novel application of atomic force microscopy (AFM) to directly visualize cytoskeletal fibers in human foreskin epithelial cells. The nonionic detergent Triton X-100 in a low concentration was used to remove the membrane, soluble proteins, and organelles from the cell. The remaining cytoskeleton can then be directly visualized in either liquid or air-dried ambient conditions. These two types of scanning provide complimentary information. Scanning in liquid visualizes the surface filaments of the cytoskeleton, whereas scanning in air shows both the surface filaments and the total "volume" of the cytoskeletal fibers. The smallest fibers observed were ca. 50 nm in diameter. The lateral resolution of this technique was ca.20 nm, which can be increased to a single nanometer level by choosing sharper AFM tips. Because the AFM is a true three dimensional technique, we are able to quantify the observed cytoskeleton by its density and volume. The types of fibers can be identified by their size, similar to...

  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. A Conceptual Atomic Force Microscope using LEGO for Nanoscience Education

    Directory of Open Access Journals (Sweden)

    Tsung-Han Hsieh

    2014-05-01

    Full Text Available A lack of effective educational materials is limited general public awareness of, and interest in, nanoscience. This paper presents a conceptual atomic force microscope (AFM model built by using the LEGO® MINDSTORMS series. AFMs are perhaps one of the most fundamental and widely-used instruments in nanoscience and nanotechnology, thus the introduction of this LEGO® AFM should be beneficial to nanoscience education. Programmed in LabVIEW, this LEGO® model has the ability to scan the samples and construct a three-dimensional (3D surface graphs of the sample, based on the mechanism used for AFM. With this LEGO® AFM, the students can directly access nanoscience concepts through hands-on experience constructing an AFM model. This interaction will lead to a better understanding of nanoscience principles, and motivate learners to further explore both the theoretical and experimental aspects of the domain.

  19. 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

  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. 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

  3. 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.

  4. The atomic force microscope as a mechano–electrochemical pen

    Directory of Open Access Journals (Sweden)

    Christian Obermair

    2011-10-01

    Full Text Available We demonstrate a method that allows the controlled writing of metallic patterns on the nanometer scale using the tip of an atomic force microscope (AFM as a “mechano–electrochemical pen”. In contrast to previous experiments, no voltage is applied between the AFM tip and the sample surface. Instead, a passivated sample surface is activated locally due to lateral forces between the AFM tip and the sample surface. In this way, the area of tip–sample interaction is narrowly limited by the mechanical contact between tip and sample, and well-defined metallic patterns can be written reproducibly. Nanoscale structures and lines of copper were deposited, and the line widths ranged between 5 nm and 80 nm, depending on the deposition parameters. A procedure for the sequential writing of metallic nanostructures is introduced, based on the understanding of the passivation process. The mechanism of this mechano–electrochemical writing technique is investigated, and the processes of site-selective surface depassivation, deposition, dissolution and repassivation of electrochemically deposited nanoscale metallic islands are studied in detail.

  5. Atomic force microscope chamber for in situ studies of ice

    Science.gov (United States)

    Zepeda, Salvador; Yeh, Yin; Orme, Christine A.

    2001-11-01

    To investigate the surface morphologies of biological systems in a controlled gaseous environment (e.g., the temperature, humidity and composition), most commercial atomic force microscopes require modification. We have designed a double-jacketed environmental chamber specifically for a Nanoscope IIIa (Digital Instruments, Santa Barbara, CA) force microscope. We use cold nitrogen and thermoelectric devices to control the temperature in the chamber; the nitrogen simultaneously serves to create an inert environment. We have also designed a temperature controlled sample stage utilizing thermoelectric devices for fine temperature regulation. A variation of this sample stage allows us to image samples in fluids at cold temperatures with an O-ringless configuration. The relative humidity within the chamber is also measured with commercially available relative humidity sensors. We investigate the surface morphology of ice Ih in its pure phase and shall extend the study to ice in the presence of biological molecules, such as antifreeze proteins. We present a detailed description of our design and our first images of polycrystalline ice and single crystals of ice grown in situ from the vapor.

  6. 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

  7. 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

  8. Quantitative comparison of two independent lateral force calibration techniques for the atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Barkley, Sarice S.; Cannara, Rachel J. [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Deng Zhao [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Maryland NanoCenter, University of Maryland, College Park, Maryland 20742 (United States); Gates, Richard S.; Reitsma, Mark G. [Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

    2012-02-15

    Two independent lateral-force calibration methods for the atomic force microscope (AFM)--the hammerhead (HH) technique and the diamagnetic lateral force calibrator (D-LFC)--are systematically compared and found to agree to within 5% or less, but with precision limited to about 15%, using four different tee-shaped HH reference probes. The limitations of each method, both of which offer independent yet feasible paths toward traceable accuracy, are discussed and investigated. We find that stiff cantilevers may produce inconsistent D-LFC values through the application of excessively high normal loads. In addition, D-LFC results vary when the method is implemented using different modes of AFM feedback control, constant height and constant force modes, where the latter is more consistent with the HH method and closer to typical experimental conditions. Specifically, for the D-LFC apparatus used here, calibration in constant height mode introduced errors up to 14 %. In constant force mode using a relatively stiff cantilever, we observed an {approx_equal} 4 % systematic error per {mu}N of applied load for loads {<=} 1 {mu}N. The issue of excessive load typically emerges for cantilevers whose flexural spring constant is large compared with the normal spring constant of the D-LFC setup (such that relatively small cantilever flexural displacements produce relatively large loads). Overall, the HH method carries a larger uncertainty, which is dominated by uncertainty in measurement of the flexural spring constant of the HH cantilever as well as in the effective length dimension of the cantilever probe. The D-LFC method relies on fewer parameters and thus has fewer uncertainties associated with it. We thus show that it is the preferred method of the two, as long as care is taken to perform the calibration in constant force mode with low applied loads.

  9. Novel parallel plate condenser for single particle electrostatic force measurements in atomic force microscope

    KAUST Repository

    Kwek, Jin Wang

    2011-07-01

    A combination of small parallel plate condenser with Indium Tin Oxide (ITO) glass slides as electrodes and an atomic force microscope (AFM) is used to characterize the electrostatic behavior of single glass bead microparticles (105-150 μm) glued to the AFM cantilever. This novel setup allows measurements of the electrostatic forces acting on a particle in an applied electrical field to be performed in ambient air conditions. By varying the position of the microparticle between the electrodes and the strength of the applied electric field, the relative contributions of the particle net charge, induced and image charges were investigated. When the microparticle is positioned in the middle of the electrodes, the force acting on the microparticle was linear with the applied electric field and proportional to the microparticle net charge. At distances close to the bottom electrode, the force follows a parabolic relationship with the applied electric field reflecting the contributions of induced and image charges. The method can be used for the rapid evaluation of the charging and polarizability properties of the microparticle as well as an alternative to the conventional Faraday\\'s pail technique. © 2011 Elsevier B.V.

  10. 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.

  11. Manipulation and Graphene local oxidation lithography using an Atomic Force Microscope

    International Nuclear Information System (INIS)

    in this work, SPM nano lithography in Atomic Force Microscope mode was used to etching and manipulate graphene films on a nanoscopic length scale in order to produce electronic nano structures. By means of local anodic oxidation with an Atomic Force Microscope which is an electrochemical process applying voltage between Atomic Force Microscope probe and graphene surface, we are able to structure isolating trenches into single-layer and few-layer graphene flakes. Trench sizes of less than 30 nm in width are attainable with this technique. Besides oxidation, the influence of mechanical peeling and scratching with an Atomic Force Microscope of few layer graphene sheets was investigated.

  12. Modelling atomic scale manipulation with the non-contact atomic force microscope

    International Nuclear Information System (INIS)

    We present the results of calculations performed to model the process of lateral manipulation of an oxygen vacancy in the MgO(001) surface using the non-contact atomic force microscope (NC-AFM). The potential energy surfaces for the manipulation as a function of tip position are determined from atomistic modelling of the MgO(001) surface interacting with a Mg terminated MgO tip. These energies are then used to model the dynamical evolution of the system as the tip oscillates and at a finite temperature using a kinetic Monte Carlo method. The manipulation process is strongly dependent on the lateral position of the tip and the system temperature. It is also found that the expectation value of the point at which the vacancy jumps depends on the trajectory of the oscillating cantilever as the surface is approached. The effect of the manipulation on the operation of the NC-AFM is modelled with a virtual dynamic AFM, which explicitly simulates the entire experimental instrumentation and control loops. We show how measurable experimental signals can result from a single controlled atomic scale event and suggest the most favourable conditions for achieving successful atomic scale manipulation experimentally

  13. 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)

  14. 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.

  15. 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.

  16. 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...

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. z calibration of the atomic force microscope by means of a pyramidal tip

    DEFF Research Database (Denmark)

    Jensen, Flemming

    1993-01-01

    A new method for imaging the probe tip of an atomic force microscope cantilever by the atomic force microscope itself (self-imaging) is presented. The self-imaging is accomplished by scanning the probe tip across a sharper tip on the surface. By using a pyramidal probe tip with a very well...

  5. 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

  6. Observation of three-level rectified dipole forces acting on trapped atoms

    Science.gov (United States)

    Grove, T. T.; Duncan, B. C.; Sanchez-Villicana, V.; Gould, P. L.

    1995-06-01

    We have observed rectified dipole forces acting on three-level atoms in the cascade configuration. Laser cooled and trapped rubidium atoms are illuminated with an intense bichromatic standing wave (780 and 776 nm) tuned near resonance with the 5S1/2-->5P3/2-->5D5/2 transitions. The resulting rectified forces produce periodic potential wells (71-μm period), which localize the cold atoms. Experimental results are in reasonable agreement with theoretical predictions. These forces may be useful in atom optics and laser traps.

  7. 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

  8. Contact resonances of U-shaped atomic force microscope probes

    Energy Technology Data Exchange (ETDEWEB)

    Rezaei, E.; Turner, J. A., E-mail: jaturner@unl.edu [Mechanical and Materials Engineering, University of Nebraska-Lincoln, W342 Nebraska Hall, Lincoln, Nebraska 68588 (United States)

    2016-01-21

    Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes.

  9. Contact resonances of U-shaped atomic force microscope probes

    International Nuclear Information System (INIS)

    Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. Atomic Forces for Geometry-Dependent Point Multipole and Gaussian Multipole Models

    OpenAIRE

    Elking, Dennis M.; Perera, Lalith; Duke, Robert; Darden, Thomas; Pedersen, Lee G.

    2010-01-01

    In standard treatments of atomic multipole models, interaction energies, total molecular forces, and total molecular torques are given for multipolar interactions between rigid molecules. However, if the molecules are assumed to be flexible, two additional multipolar atomic forces arise due to 1) the transfer of torque between neighboring atoms, and 2) the dependence of multipole moment on internal geometry (bond lengths, bond angles, etc.) for geometry-dependent multipole models. In the curr...

  17. 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.

  18. Radiation forces on a three-level atom in the high-order Bessel beams

    Institute of Scientific and Technical Information of China (English)

    Wang Zheng-Ling; Yin Jian-Ping

    2008-01-01

    The general expressions of the average dissipative and dipole forces acting on a A-configuration three-level atom in an arbitrary light field are derived by means of the optical Bloch equations based on the atomic density matrix elements, and the general properties of the average dissipative and dipole forces on a three-level atom in the linearly-polarized high-order Bessel beams (HBBs) are analysed. We find a resonant property (with two resonant peaks) of the dissipative force and a non-resonant property (with two pairs of non-resonant peaks) of the dipole force on the three-level atom, which are completely different from those on the two-level atom. Meanwhile we find a saturation effect of the average dissipative force in the HBB, which comes from the saturation of the upper-level population. Our study shows that the general expressions of the average dissipative and dipole forces on the three-level atom will be simplified to those of the two-level atom under the approximation of large detuning. Finally, we study the axial and azimuthal Doppler cooling of atoms in 1D optical molasses composed of two counter-propagating HBBs and discuss the azimuthal influence of the HBB on the Doppler cooling limit. We also find that the Doppler limit of atoms in the molasses HBB is slightly below the conventional Doppler limit of hг/(2кB) due to the orbital angular momentum lh of the HBB.

  19. Interplay between radiation pressure force and scattered light intensity in the cooperative scattering by cold atoms

    CERN Document Server

    Bienaime, Tom; Chabe, Julien; Rouabah, Mohamed-Taha; Bellando, Louis; Courteille, Philippe W; Piovella, Nicola; Kaiser, Robin

    2013-01-01

    The interplay between the superradiant emission of a cloud of cold two-level atoms and the radiation pressure force is discussed. Using a microscopic model of coupled atomic dipoles driven by an external laser, the radiation field and the average radiation pressure force are derived. A relation between the far-field scattered intensity and the force is derived, using the optical theorem. Finally, the scaling of the sample scattering cross section with the parameters of the system is studied.

  20. Force on a neutral atom near conducting microstructures

    OpenAIRE

    Eberlein, Claudia; Zietal, Robert

    2006-01-01

    We derive the nonretarded energy shift of a neutral atom for two different geometries. For an atom close to a cylindrical wire we find an integral representation for the energy shift, give asymptotic expressions, and interpolate numerically. For an atom close to a semi-infinite half plane we determine the exact Green's function of the Laplace equation and use it to derive the exact energy shift for an arbitrary position of the atom. These results can be used to estimate the energy shift of an...

  1. 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

  2. A new united atom force field for adsorption of alkenes in zeolites

    NARCIS (Netherlands)

    B. Liu; B. Smit; F. Rey; S. Valencia; S. Calero

    2008-01-01

    A new united atom force field was developed that accurately describes the adsorption properties of linear alkenes in zeolites. The force field was specifically designed for use in the inhomogeneous system and therefore a truncated and shifted potential was used. With the determined force field, we p

  3. 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

  4. 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

  5. Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope

    DEFF Research Database (Denmark)

    Jensen, Carsten P.

    Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope......Calibrated atomic force microscope measurements of vickers hardness indentations and tip production and characterisation for scanning tunelling microscope...

  6. 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.

  7. 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

  8. Atom-wall dispersive forces from master equation formalism

    CERN Document Server

    Mendes, T N C

    2007-01-01

    Using the general expressions for level shifts obtained from the master equation for a small system interacting with a large one considered as a reservoir, we calculate the dispersive potentials between an atom and a wall in the dipole approximation. We analyze in detail the particular case of a two-level atom in the presence of a perfectly conducting wall. We study the van der Waals as well as the resonant interactions. All distance regimes as well as the high and low temperature regimes are considered. We show that the Casimir-Polder interaction can not be considered as a direct result of the vacuum fluctuations only. Concerning the interaction between the atom and the wall at high temperature, which show that a saturation of the potential for all distances occurs. This saturated potential coincides exactly with that obtained in the London-van der Waals limit.

  9. Casimir-Polder forces on atoms in the presence of magnetoelectronic bodies

    Energy Technology Data Exchange (ETDEWEB)

    Buhmann, S.Y.

    2007-07-05

    In this work, the CP force between a single neutral atom or molecule and neutral magnetoelectric bodies is studied. The focus lies on the pure vacuum CP force, i.e., the electromagnetic field is in general understood to be in its ground state. Furthermore, we assume that the atom-body separation is sufficiently large to ensure that the atom is adequately characterised as an electric dipole, while the body can be described by its macroscopic magnetoelectric properties; and that repulsive exchange forces due to the overlap between the electronic wave functions of the atom and the bodies can be neglected. Interactions due to non-vanishing net charges, permanent electric dipole moments, magnetisability, quadrupole (or higher multipole) polarisabilities of the atom and those resulting from non-local or anisotropic magnetoelectric properties of the bodies are ignored. (orig.)

  10. Atom-wall dispersive forces from master equation formalism

    OpenAIRE

    Mendes, T. N. C.; Farina, C.

    2007-01-01

    Using the general expressions for level shifts obtained from the master equation for a small system interacting with a large one considered as a reservoir, we calculate the dispersive potentials between an atom and a wall in the dipole approximation. We analyze in detail the particular case of a two-level atom in the presence of a perfectly conducting wall. We study the van der Waals as well as the resonant interactions. All distance regimes as well as the high and low temperature regimes are...

  11. Synthetic Lorentz force in classical atomic gases via Doppler effect and radiation pressure

    CERN Document Server

    Dubček, T; Jukić, D; Aumiler, D; Ban, T; Buljan, H

    2014-01-01

    We theoretically predict a novel type of synthetic Lorentz force for classical (cold) atomic gases, which is based on the Doppler effect and radiation pressure. A fairly uniform and strong force can be constructed for gases in macroscopic volumes of several cubic millimeters and more. This opens the possibility to mimic classical charged gases in magnetic fields, such as those in a tokamak, in cold atom experiments.

  12. 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 ...

  13. 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

  14. 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

  15. 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

  16. Torque and atomic forces for Cartesian tensor atomic multipoles with an application to crystal unit cell optimization.

    Science.gov (United States)

    Elking, Dennis M

    2016-08-15

    New equations for torque and atomic force are derived for use in flexible molecule force fields with atomic multipoles. The expressions are based on Cartesian tensors with arbitrary multipole rank. The standard method for rotating Cartesian tensor multipoles and calculating torque is to first represent the tensor with n indexes and 3(n) redundant components. In this work, new expressions for directly rotating the unique (n + 1)(n + 2)/2 Cartesian tensor multipole components Θpqr are given by introducing Cartesian tensor rotation matrix elements X(R). A polynomial expression and a recursion relation for X(R) are derived. For comparison, the analogous rotation matrix for spherical tensor multipoles are the Wigner functions D(R). The expressions for X(R) are used to derive simple equations for torque and atomic force. The torque and atomic force equations are applied to the geometry optimization of small molecule crystal unit cells. In addition, a discussion of computational efficiency as a function of increasing multipole rank is given for Cartesian tensors. © 2016 Wiley Periodicals, Inc. PMID:27349179

  17. 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

  18. Higher Harmonics Generation in Tapping Mode Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    LI Yuan; QIAN Jian-Qiang

    2009-01-01

    The contribution of higher harmonics to the movement of a micro rectangular cantilever in tapping mode AFM is investigated. The dependence between the phase lag of the higher harmonic components and tip-sample separation are found to be an order of magnitude higher than the base one, reflecting an increasing sensitivity to local variations of surface properties compared to the normal phase signal.The strong correlation between the higher harmonic amplitude and average sample deformation implies that the higher harmonic amplitude can be taken to monitor the tapping force or as feedback variable to fulfill a constant repulsive force mode.

  19. Four-Color Stimulated Optical Forces for Atomic and Molecular Slowing

    CERN Document Server

    Galica, S E; Eyler, E E

    2013-01-01

    Stimulated optical forces offer a simple and efficient method for providing optical forces far in excess of the saturated radiative force. The bichromatic force, using a counterpropagating pair of two-color beams, has so far been the most effective of these stimulated forces for deflecting and slowing atomic beams. We have numerically studied the evolution of a two-level system under several different bichromatic and polychromatic light fields, while retaining the overall geometry of the bichromatic force. New insights are gained by studying the time-dependent trajectory of the Bloch vector, including a better understanding of the remarkable robustness of bi- and polychromatic forces with imbalanced beam intensities. We show that a four-color polychromatic force exhibits great promise. By adding new frequency components at the third harmonic of the original bichromatic detuning, the force is increased by nearly 50% and its velocity range is extended by a factor of three, while the required laser power is incr...

  20. 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.

  1. 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

  2. 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...

  3. Origin of current-induced forces in an atomic gold wire: A first-principles study

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Stokbro, Kurt; Taylor, Jeremy Philip;

    2003-01-01

    We address the microscopic origin of the current-induced forces by analyzing results of first principles density functional calculations of atomic gold wires connected to two gold electrodes with different electrochemical potentials. We find that current induced forces are closely related to the ...

  4. 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.

  5. 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

  6. 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

  7. 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...

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

    Science.gov (United States)

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

    2016-09-01

    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.

  9. 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

  10. 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.

    2016-01-01

    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

  11. Dispersion forces II. Many-body effects, excited atoms, finite temperature and quantum friction

    Energy Technology Data Exchange (ETDEWEB)

    Buhmann, Stefan Yoshi [Imperial College London (United Kingdom). Quantum Optics and Laser Science

    2012-07-01

    Presents the unified theory of dispersion forces. Gives a thorough overview over recent results of dispersion forces. Deals with applied macroscopic quantum electrodynamics. Gives guidance to simulation of realistic material properties. In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contexts.

  12. 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

  13. 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...

  14. 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.

  15. 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.

  16. Development of Atomic Force Microscope for Arthroscopic Knee Cartilage Inspection

    Science.gov (United States)

    Imer, Raphaël; Akiyama, Terunobu; de Rooij, Nicolaas F.; Stolz, Martin; Aebi, Ueli; Friederich, Niklaus F.; Koenig, Uwe; Wirz, Dieter; Daniels, A. U.; Staufer, Urs

    2006-03-01

    A recent study, based on ex vivo unconfined compression testing of normal, diseased, and enzymatically altered cartilage, revealed that a scanning force microscope (SFM), used as a nano-intender, is sensitive enough to enable measurement of alterations in the biomechanical properties of cartilage. Based on these ex vivo measurements, we have designed a quantitative diagnosis tool, the scanning force arthroscope (SFA), able to perform in vivo measurements during a standard arthroscopic procedure. For stabilizing and positioning the instrument relative to the surface under investigation, a pneumatic system has been developed. A segmented piezoelectric tube was used to perform the indentation displacement, and a pyramidal nanometer-scale silicon tip mounted on a cantilever with an integrated deflection sensor measured the biomechanical properties of cartilage. Mechanical means were designed to protect the fragile cantilever during the insertion of the instrument into the knee joint. The stability of the pneumatic stage was checked with a prototype SFA. In a series of tests, load-displacement curves were recorded in a knee phantom and, more recently, in a pig’s leg.

  17. Measurement of the gold–gold bond rupture force at 4 K in a single-atom chain using photon-momentum-based force calibration

    International Nuclear Information System (INIS)

    We present instrumentation and methodology for simultaneously measuring force and displacement at the atomic scale at 4 K. The technique, which uses a macroscopic cantilever as a force sensor and high-resolution, high-stability fiber-optic interferometers for displacement measurement, is particularly well-suited to making accurate, traceable measurements of force and displacement in nanometer- and atomic-scale mechanical deformation experiments. The technique emphasizes accurate co-location of force and displacement measurement and measures cantilever stiffness at the contact point in situ at 4 K using photon momentum. We present preliminary results of measurements made of the force required to rupture a single atomic bond in a gold single-atom chain formed between a gold flat and a gold tip. Finally, we discuss the possible use of the gold–gold bond rupture force as an intrinsic force calibration value for forces near 1 nN. (paper)

  18. 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

  19. 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.

  20. Analysis of Atomic Force Curve Data for Mapping of Surface Properties in Water

    Science.gov (United States)

    Sirghi, Lucel; Nakagiri, Nobuyuki; Sugimura, Hiroyuki; Takai, Osamu

    2001-03-01

    This paper presents an analysis of atomic force versus distance curves for a silicon nitride probe and a silicon sample immersed in water. A custom-built atomic force microscope (AFM) was adapted for working in water by building a water cell from a liquid drop caught between a glass lamella fixed on the top of the cantilever base and the sample surface. An algorithm for processing of force curve data for long- and short-range forces is described. The force curve data taken for a sample consisting of a silicon wafer Si(111) patterned with V-shaped grooves and a silicon nitride cantilever in water were digitally acquired and automatically processed for mapping of surface properties. A weak repulsive double layer force with no relevant dependence on sample topography was observed on the force curves taken during approach movement of the cantilever. On the other hand, the attractive hydration force showed a strong dependence on the sample topography. Large hydration force values were noticed on the inclined faces of the V-shaped grooves while small hydration force values were noticed outside the grooves. The result was explained by the dependence of the tip curvature radius at the contact region on the tilt of the sample surface.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope.

    Science.gov (United States)

    Lange, Manfred; van Vörden, Dennis; Möller, Rolf

    2012-01-01

    Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM) allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip-sample system, and the process can be understood as a hysteresis of forces between approach and retraction of the tip. In this paper, we present the direct measurement of the whole hysteresis loop in force-spectroscopy curves at 77 K on the PTCDA/Ag/Si(111) √3 × √3 surface by means of a tuning-fork-based NC-AFM with an oscillation amplitude smaller than the distance range of the hysteresis loop. The hysteresis effect is caused by the making and breaking of a bond between PTCDA molecules on the surface and a PTCDA molecule at the tip. The corresponding energy loss was determined to be 0.57 eV by evaluation of the force-distance curves upon approach and retraction. Furthermore, a second dissipation process was identified through the damping of the oscillation while the molecule on the tip is in contact with the surface. This dissipation process occurs mainly during the retraction of the tip. It reaches a maximum value of about 0.22 eV/cycle. PMID:22496993

  6. 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...

  7. 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...

  8. 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.

  9. 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.

  10. Protein simulations combining an all-atom force field with a Go term

    International Nuclear Information System (INIS)

    Using a variant of parallel tempering, we study the changes in sampling within a simulation, when the all-atom model is coupled to a Go-like potential. We find that the native structure is not the lowest-energy configuration in the all-atom force field. Adding a Go term deforms the energy landscape in such a way that the native configuration becomes the global minimum but does not lead to faster thermalization

  11. Atomic scale imaging and spectroscopy of individual electron trap states using force detected dynamic tunnelling

    International Nuclear Information System (INIS)

    We report the first atomic scale imaging and spectroscopic measurements of electron trap states in completely non-conducting surfaces by dynamic tunnelling force microscopy/spectroscopy. Single electrons are dynamically shuttled to/from individual states in thick films of hafnium silicate and silicon dioxide. The new method opens up surfaces that are inaccessible to the scanning tunnelling microscope for imaging and spectroscopy on an atomic scale.

  12. Influence of measuring parameters on the accuracy of atomic force microscope in industrial applications

    DEFF Research Database (Denmark)

    Tosello, Guido; Antico, Andrea; Hansen, Hans Nørgaard;

    2009-01-01

    Atomic Force Microscopy (AFM) is a powerful technique providing 3D surface topographies with very high resolution in both lateral and vertical direction. Thanks to its relatively easy use, AFM can be well introduced in process control, gaining great advantage in research as well as in the evaluat......Atomic Force Microscopy (AFM) is a powerful technique providing 3D surface topographies with very high resolution in both lateral and vertical direction. Thanks to its relatively easy use, AFM can be well introduced in process control, gaining great advantage in research as well...

  13. Experimental Demonstration of Synthetic Lorentz Force on Cold Atoms by Using Radiation Pressure

    Science.gov (United States)

    Ban, Ticijana; Santic, Neven; Dubcek, Tena; Aumiler, Damir; Buljan, Hrvoje

    2015-05-01

    The quest for synthetic magnetism in quantum degenerate atomic gases is motivated by producing controllable quantum emulators, which could mimic complex quantum systems such as interacting electrons in magnetic fields. Experiments on synthetic magnetic fields for neutral atoms have enabled realization of the Hall effect, Harper and Haldane Hamiltonians, and other intriguing topological effects. Here we present the first demonstration of a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, in cold atomic gases captured in a Magneto-Optical Trap (MOT). Synthetic Lorentz force on cold atomic cloud is measured by recording the cloud trajectory. The observed force is perpendicular to the cloud velocity, and it is zero for the atomic cloud at rest. The proposed concept is straightforward to implement in a large volume and different geometries, it is applicable for a broad range of velocities, and it can be realized for different atomic species. The experiment is based on the theoretical proposal introduced in. This work was supported by the UKF Grant No. 5/13 and Croatian MZOS.

  14. 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.

  15. 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

  16. A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

    Directory of Open Access Journals (Sweden)

    Manfred Lange

    2012-03-01

    Full Text Available Measurements of the frequency shift versus distance in noncontact atomic force microscopy (NC-AFM allow measurements of the force gradient between the oscillating tip and a surface (force-spectroscopy measurements. When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip–sample system, and the process can be understood as a hysteresis of forces between approach and retraction of the tip. In this paper, we present the direct measurement of the whole hysteresis loop in force-spectroscopy curves at 77 K on the PTCDA/Ag/Si(111 √3 × √3 surface by means of a tuning-fork-based NC-AFM with an oscillation amplitude smaller than the distance range of the hysteresis loop. The hysteresis effect is caused by the making and breaking of a bond between PTCDA molecules on the surface and a PTCDA molecule at the tip. The corresponding energy loss was determined to be 0.57 eV by evaluation of the force–distance curves upon approach and retraction. Furthermore, a second dissipation process was identified through the damping of the oscillation while the molecule on the tip is in contact with the surface. This dissipation process occurs mainly during the retraction of the tip. It reaches a maximum value of about 0.22 eV/cycle.

  17. 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.

  18. 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.

  19. 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.

  20. Average Dissipative and Dipole Forces on a Three-Level Atom in a Laguerre-Gaussian Beam

    Institute of Scientific and Technical Information of China (English)

    WANG Zheng-Ling; YIN Jian-Ping

    2005-01-01

    @@ By means of the optical Bloch equations based on the atomic density matrix elements, the general expressions of the average dissipative force, dipole force and the mechanical torque acting on a A-configuration three-level atom in a linearly-polarized Laguerre-Gaussian beam (LGB) with an angular momentum of lh are derived, and the general properties of the average dissipative and dipole force on the three-level atom in the linearly-polarized LGB are analysed. We find a resonant property (with two resonant peaks) of the dissipative force and a non-resonant property (with two pairs of non-resonant peaks) of the dipole force on the three-level atom, which are completely different from those on the two-level atom. Our study also shows that all of general expressions on the three-level atom will be simplified to those on the two-level atom in the approximation of large detuning.

  1. 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...

  2. 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.

  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. 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...

  5. 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...

  6. 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.

  7. 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...

  8. Sensitive measurement of forces at the micron scale using Bloch oscillations of ultracold atoms.

    Science.gov (United States)

    Carusotto, I; Pitaevskii, L; Stringari, S; Modugno, G; Inguscio, M

    2005-08-26

    We show that Bloch oscillations of ultracold fermionic atoms in the periodic potential of an optical lattice can be used for a sensitive measurement of forces at the micrometer length scale, e.g., in the vicinity of a dielectric surface. In particular, the proposed approach allows us to perform a local and direct measurement of the Casimir-Polder force which is, for realistic experimental parameters, as large as 10(-4) gravity.

  9. 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, ...

  10. 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

  11. 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...

  12. 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

  13. Development of novel and sensitive sensors based on microcantilever of atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    JIN Yan; WANG Kemin; JIN Rong

    2006-01-01

    Recently, the development of sensors based on microfabricated cantilevers of atomic force microscope (AFM) has attracted considerable attention from the designers of novel physical, chemical, and biological sensors. Many kinds of sensors have been developed taking the advantages of its high-resolution imaging, force measurement and force sensitivity, such as immunosensor and DNA biosensor and the sensors for detection of intermolecular interaction. This paper reviews the progress made in this field and discusses the signal transfer principles by which the design of the sensors is achieved.

  14. Atomic Force Microscope Studies of the Fusion of Floating Lipid Bilayers

    OpenAIRE

    Abdulreda, Midhat H.; Moy, Vincent T.

    2007-01-01

    This study investigated the fusion of apposing floating bilayers of egg L-α-phosphatidylcholine (egg PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine. Atomic force microscope measurements of fusion forces under different compression rates were acquired to reveal the energy landscape of the fusion process under varied lipid composition and temperature. Between compression rates of ∼1000 and ∼100,000 pN/s, applied forces in the range from ∼100 to ∼500 pN resulted in fusion of floating bilayer...

  15. 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}.

  16. Serum induced degradation of 3D DNA box origami observed by high speed atomic force microscope

    DEFF Research Database (Denmark)

    Jiang, Zaixing; Zhang, Shuai; Yang, Chuanxu;

    2015-01-01

    DNA box origami in serum using high-speed atomic force microscope optimized for imaging 3D DNA origami in real time. The time resolution allows characterizing the stages of serum effects on individual 3D DNA box origami with nanometer resolution. Our results indicate that the whole digest process...

  17. 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…

  18. 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...

  19. 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

  20. Atomic Radii in Molecules for Use in a Polarizable Force Field

    NARCIS (Netherlands)

    Swart, Marcel; Van Duijnen, Piet Th

    2011-01-01

    We report here the results for an ab initio approach to obtain the parameters needed for molecular simulations using a polarizable force field. These parameters consist of the atomic charges, polarizabilities, and radii. The former two are readily obtained using methods reported previously (van Duij

  1. 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

  2. Polymerized LB films imaged with a combined atomic force microscope-fluorescence microscope

    NARCIS (Netherlands)

    Putman, Constant A.J.; Hansma, Helen G.; Gaub, Hermann E.; Hansma, Paul K.

    1992-01-01

    The first results obtained with a new stand-alone atomic force microscope (AFM) integrated with a standard Zeiss optical fluorescence microscope are presented. The optical microscope allows location and selection of objects to be imaged with the high-resolution AFM. Furthermore, the combined microsc

  3. A Computer-Controlled Classroom Model of an Atomic Force Microscope

    Science.gov (United States)

    Engstrom, Tyler A.; Johnson, Matthew M.; Eklund, Peter C.; Russin, Timothy J.

    2015-01-01

    The concept of "seeing by feeling" as a way to circumvent limitations on sight is universal on the macroscopic scale--reading Braille, feeling one's way around a dark room, etc. The development of the atomic force microscope (AFM) in 1986 extended this concept to imaging in the nanoscale. While there are classroom demonstrations that use…

  4. A Cost-Effective Atomic Force Microscope for Undergraduate Control Laboratories

    Science.gov (United States)

    Jones, C. N.; Goncalves, J.

    2010-01-01

    This paper presents a simple, cost-effective and robust atomic force microscope (AFM), which has been purposely designed and built for use as a teaching aid in undergraduate controls labs. The guiding design principle is to have all components be open and visible to the students, so the inner functioning of the microscope has been made clear to…

  5. 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...

  6. 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.

  7. 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

  8. Atomic force microscope with combined FTIR-Raman spectroscopy having a micro thermal analyzer

    Science.gov (United States)

    Fink, Samuel D.; Fondeur, Fernando F.

    2011-10-18

    An atomic force microscope is provided that includes a micro thermal analyzer with a tip. The micro thermal analyzer is configured for obtaining topographical data from a sample. A raman spectrometer is included and is configured for use in obtaining chemical data from the sample.

  9. 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

  10. 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...

  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. Presentation to the Atomic Energy Commission and the Air Force, June 14, 1962

    Energy Technology Data Exchange (ETDEWEB)

    none

    1962-10-01

    This volume contains the charts and backup material presented to the Atomic Energy Commission and Air Force on June 14, 1962 concerning General Electric's Nuclear Materials and Propulsion Operation (formerly the Aircraft Nuclear Propulsion Department), during its work on the development of a nuclear power plant for manned aircraft.

  13. Nano Goes to School: A Teaching Model of the Atomic Force Microscope

    Science.gov (United States)

    Planinsic, Gorazd; Kovac, Janez

    2008-01-01

    The paper describes a teaching model of the atomic force microscope (AFM), which proved to be successful in the role of an introduction to nanoscience in high school. The model can demonstrate the two modes of operation of the AFM (contact mode and oscillating mode) as well as some basic principles that limit the resolution of the method. It can…

  14. 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...

  15. 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

  16. 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

  17. 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

  18. Intermittent contact interaction between an atomic force microscope cantilever and a nanowire

    Science.gov (United States)

    Knittel, I.; Ungewitter, L.; Hartmann, U.

    2012-05-01

    We investigate in theory and experiment the intermittent contact interaction between an atomic force microscope (AFM) cantilever and a nanowire under ambient conditions. The nanowire is modeled as a spring reacting instantaneously to any change of the force between the wire and the cantilever. This implies that the cantilever is subject to an "effective" force-distance relation, containing not only the surface forces but also the deflection of the nanowire. Experimentally, CVD-grown tin oxide nanowires and lithographically structured silicon nanowire arrays were investigated by intermittent contact AFM. By comparison of experimental and simulated distance-dependent resonance curves it is found that the nanowires behave like "fast nanosprings" and that the adhesion force is one of the key factors determining distance-dependent resonance curves. The results are fully applicable to a scenario in which a cantilever equipped by a nanowire interacts with a surface.

  19. 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.

  20. Force Field Analysis Suggests a Lowering of Diffusion Barriers in Atomic Manipulation Due to Presence of STM Tip

    Science.gov (United States)

    Emmrich, Matthias; Schneiderbauer, Maximilian; Huber, Ferdinand; Weymouth, Alfred J.; Okabayashi, Norio; Giessibl, Franz J.

    2015-04-01

    We study the physics of atomic manipulation of CO on a Cu(111) surface by combined scanning tunneling microscopy and atomic force microscopy at liquid helium temperatures. In atomic manipulation, an adsorbed atom or molecule is arranged on the surface using the interaction of the adsorbate with substrate and tip. While previous experiments are consistent with a linear superposition model of tip and substrate forces, we find that the force threshold depends on the force field of the tip. Here, we use carbon monoxide front atom identification (COFI) to characterize the tip's force field. Tips that show COFI profiles with an attractive center can manipulate CO in any direction while tips with a repulsive center can only manipulate in certain directions. The force thresholds are independent of bias voltage in a range from 1 to 10 mV and independent of temperature in a range of 4.5 to 7.5 K.

  1. Force field analysis suggests a lowering of diffusion barriers in atomic manipulation due to presence of STM tip.

    Science.gov (United States)

    Emmrich, Matthias; Schneiderbauer, Maximilian; Huber, Ferdinand; Weymouth, Alfred J; Okabayashi, Norio; Giessibl, Franz J

    2015-04-10

    We study the physics of atomic manipulation of CO on a Cu(111) surface by combined scanning tunneling microscopy and atomic force microscopy at liquid helium temperatures. In atomic manipulation, an adsorbed atom or molecule is arranged on the surface using the interaction of the adsorbate with substrate and tip. While previous experiments are consistent with a linear superposition model of tip and substrate forces, we find that the force threshold depends on the force field of the tip. Here, we use carbon monoxide front atom identification (COFI) to characterize the tip's force field. Tips that show COFI profiles with an attractive center can manipulate CO in any direction while tips with a repulsive center can only manipulate in certain directions. The force thresholds are independent of bias voltage in a range from 1 to 10 mV and independent of temperature in a range of 4.5 to 7.5 K. PMID:25910137

  2. 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

  3. 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.

  4. Surface features on Sahara soil dust particles made visible by atomic force microscope (AFM phase images

    Directory of Open Access Journals (Sweden)

    M. O. Andreae

    2008-10-01

    Full Text Available We show that atomic force microscopy (AFM phase images can reveal surface features of soil dust particles, which are not evident using other microscopic methods. The non-contact AFM method is able to resolve topographical structures in the nanometer range as well as to uncover repulsive atomic forces and attractive van der Waals' forces, and thus gives insight to surface properties. Though the method does not allow quantitative assignment in terms of chemical compound description, it clearly shows deposits of distinguishable material on the surface. We apply this technique to dust aerosol particles from the Sahara collected over the Atlantic Ocean and describe micro-features on the surfaces of such particles.

  5. Surface features on Sahara soil dust particles made visible by atomic force microscope (AFM phase images

    Directory of Open Access Journals (Sweden)

    G. Helas

    2008-08-01

    Full Text Available We show that atomic force microscopy (AFM phase images can reveal surface features of soil dust particles, which are not evident using other microscopic methods. The non-contact AFM method is able to resolve topographical structures in the nanometer range as well as to uncover repulsive atomic forces and attractive van der Waals' forces, and thus gives insight to surface properties. Though the method does not allow quantitative assignment in terms of chemical compound description, it clearly shows deposits of distinguishable material on the surface. We apply this technique to dust aerosol particles from the Sahara collected over the Atlantic Ocean and describe micro-features on the surfaces of such particles.

  6. 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

  7. Measuring the van der Waals forces between a Rydberg atom and a metallic surface

    International Nuclear Information System (INIS)

    We have observed the deflection of Rydberg atoms towards a metallic surface by the van der Waals force. Cs and Na atoms in states of principal quantum number n were sent between two parallel gold-coated mirrors, spaced by a gap w (2.1 μm≤w≤8.5 μm). We measured the value n/sub m/ at which the transmission cuts off and from the variation of n/sub m/ versus w, we obtained a measure of the atom-surface interaction. For 12< n<30 this interaction is 3--4 orders of magnitude larger than for ground-state atoms, and it obeys the scaling laws of the Lennard-Jones model

  8. 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.

  9. 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 ...

  10. An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics

    Science.gov (United States)

    Pyzer-Knapp, Edward O.; Thompson, Hugh P. G.; Day, Graeme M.

    2016-01-01

    We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%. PMID:27484370

  11. An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics.

    Science.gov (United States)

    Pyzer-Knapp, Edward O; Thompson, Hugh P G; Day, Graeme M

    2016-08-01

    We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%. PMID:27484370

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Inter-atomic force constants of BaF{sub 2} by diffuse neutron scattering measurement

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, Takashi, E-mail: sakuma@mx.ibaraki.ac.jp; Makhsun,; Sakai, Ryutaro [Institute of Applied Beam Science, Ibaraki University, Mito 310-8512 (Japan); Xianglian [College of Physics and Electronics Information, Inner Mongolia University for the Nationalities, Tongliao 028043 (China); Takahashi, Haruyuki [Institute of Applied Beam Science, Ibaraki University, Hitachi 316-8511 (Japan); Basar, Khairul [Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung 40132 (Indonesia); Igawa, Naoki [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai 319-1195 (Japan); Danilkin, Sergey A. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Kirrawee DC NSW 2232 (Australia)

    2015-04-16

    Diffuse neutron scattering measurement on BaF{sub 2} crystals was performed at 10 K and 295 K. Oscillatory form in the diffuse scattering intensity of BaF{sub 2} was observed at 295 K. The correlation effects among thermal displacements of F-F atoms were obtained from the analysis of oscillatory diffuse scattering intensity. The force constants among neighboring atoms in BaF{sub 2} were determined and compared to those in ionic crystals and semiconductors.

  19. Derivation of Inter-Atomic Force Constants of Cu2O from Diffuse Neutron Scattering Measurement

    International Nuclear Information System (INIS)

    Neutron scattering intensity from Cu2O compound has been measured at 10 K and 295 K with High Resolution Powder Diffractometer at JRR-3 JAEA. The oscillatory diffuse scattering related to correlations among thermal displacements of atoms was observed at 295 K. The correlation parameters were determined from the observed diffuse scattering intensity at 10 and 295 K. The force constants between the neighboring atoms in Cu2O were estimated from the correlation parameters and compared to those of Ag2O (author)

  20. Derivation of Inter-Atomic Force Constants of Cu2O from Diffuse Neutron Scattering Measurement

    Directory of Open Access Journals (Sweden)

    T. Makhsun

    2013-04-01

    Full Text Available Neutron scattering intensity from Cu2O compound has been measured at 10 K and 295 K with High Resolution Powder Diffractometer at JRR-3 JAEA. The oscillatory diffuse scattering related to correlations among thermal displacements of atoms was observed at 295 K. The correlation parameters were determined from the observed diffuse scattering intensity at 10 and 295 K. The force constants between the neighboring atoms in Cu2O were estimated from the correlation parameters and compared to those of Ag2O

  1. 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

  2. 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

  3. [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

  4. 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

  5. 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.

  6. Probing molecular interaction between transferrin and anti-transferrin by atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The interaction between transferrin (Tf) and its antibody was investigated by atomic force microscope. Tf-antibody was immobilized on the Au-coated glass slide, and the specific combination between antibody and antigen was also characterized by AFM. The results showed that holo-transferrin was jogged with anti-transferrin, and binded anti-tran- sferrin more tightly than apo-transferrin. The force- distance curves revealed that the affinity of anti-trans- ferrin and holo-transferrin was much stronger than that of apo-transferrin.

  7. Refined OPLS All-Atom Force Field for Saturated Phosphatidylcholine Bilayers at Full Hydration

    DEFF Research Database (Denmark)

    Maciejewski, A.; Pasenkiewicz-Gierula, M.; Cramariuc, O.;

    2014-01-01

    We report parametrization of dipalmitoyl-phosphatidylcholine (DPPC) in the framework of the Optimized Parameters for Liquid Simulations all-atom (OPLS-AA) force field. We chose DPPC as it is one of the most studied phospholipid species and thus has plenty of experimental data necessary for model...... validation, and it is also one of the highly important and abundant lipid types, e.g., in lung surfactant. Overall, PCs have not been previously parametrized in the OPLS-AA force field; thus, there is a need to derive its bonding and nonbonding parameters for both the polar and nonpolar parts of the molecule...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Central-force decomposition of spline-based modified embedded atom method potential

    Science.gov (United States)

    Winczewski, S.; Dziedzic, J.; Rybicki, J.

    2016-10-01

    Central-force decompositions are fundamental to the calculation of stress fields in atomic systems by means of Hardy stress. We derive expressions for a central-force decomposition of the spline-based modified embedded atom method (s-MEAM) potential. The expressions are subsequently simplified to a form that can be readily used in molecular-dynamics simulations, enabling the calculation of the spatial distribution of stress in systems treated with this novel class of empirical potentials. We briefly discuss the properties of the obtained decomposition and highlight further computational techniques that can be expected to benefit from the results of this work. To demonstrate the practicability of the derived expressions, we apply them to calculate stress fields due to an edge dislocation in bcc Mo, comparing their predictions to those of linear elasticity theory.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. A direct micropipette-based calibration method for atomic force microscope cantilevers

    OpenAIRE

    Liu, Baoyu; Yu, Yan; Yao, Da-Kang; Shao, Jin-Yu

    2009-01-01

    In this report, we describe a direct method for calibrating atomic force microscope (AFM) cantilevers with the micropipette aspiration technique (MAT). A closely fitting polystyrene bead inside a micropipette is driven by precisely controlled hydrostatic pressures to apply known loads on the sharp tip of AFM cantilevers, thus providing a calibration at the most functionally relevant position. The new method is capable of calibrating cantilevers with spring constants ranging from 0.01 to hundr...

  19. Visualization of Cellulose Microfibrils of Phyllostachys pubescens Fibers with Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Atomic force microscope(AFM) was used to investigate the arrangement of cellulose microfibrils (CMF) in Moso bamboo (Phyllostachys pubescens) fibers. Two methods of sample preparation were used here for different purposes. The first method was chemical maceration with a mixture of hydrogen peroxide and glacial acetic acid, through which the obtained fibers were suitable for observing the orientation of CMF in the primary wal1. The other method was to prepare tangential microtomed sections with a thickness o...

  20. 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...

  1. 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...

  2. 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.

  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. Polymerized LB films imaged with a combined atomic force microscope-fluorescence microscope

    OpenAIRE

    Putman, Constant A.J.; Hansma, Helen G.; Gaub, Hermann E.; Hansma, Paul K.

    1992-01-01

    The first results obtained with a new stand-alone atomic force microscope (AFM) integrated with a standard Zeiss optical fluorescence microscope are presented. The optical microscope allows location and selection of objects to be imaged with the high-resolution AFM. Furthermore, the combined microscope enables a direct comparison between features observed in the fluorescence microscope and those observed in the images obtained with the AFM, in air or under liquid. The cracks in polymerized La...

  6. Effect of hydration film on scanning images of atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope (AFM). The results showed that the hydration films greatly affect the imaging resolution for the tapping mode, but no evident effect on the contact mode. The possible reasons for the effect of hydration films on scanning images of AFM are also brought forward here.

  7. 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.

  8. 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.

  9. 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

  10. Minimal Basis Iterative Stockholder: Atoms in Molecules for Force-Field Development

    CERN Document Server

    Verstraelen, Toon; Heidar-Zadeh, Farnaz; Vanduyfhuys, Louis; Van Speybroeck, Veronique; Waroquier, Michel; Ayers, Paul W

    2016-01-01

    Atomic partial charges appear in the Coulomb term of many force-field models and can be derived from electronic structure calculations with a myriad of atoms-in-molecules (AIM) methods. More advanced models have also been proposed, using the distributed nature of the electron cloud and atomic multipoles. In this work, an electrostatic force field is defined through a concise approximation of the electron density, for which the Coulomb interaction is trivially evaluated. This approximate "pro-density" is expanded in a minimal basis of atom-centered s-type Slater density functions, whose parameters are optimized by minimizing the Kullback-Leibler divergence of the pro-density from a reference electron density, e.g. obtained from an electronic structure calculation. The proposed method, Minimal Basis Iterative Stockholder (MBIS), is a variant of the Hirshfeld AIM method but it can also be used as a density-fitting technique. An iterative algorithm to refine the pro-density is easily implemented with a linear-sca...

  11. 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

  12. Modular apparatus for electrostatic actuation of common atomic force microscope cantilevers

    Energy Technology Data Exchange (ETDEWEB)

    Long, Christian J., E-mail: christian.long@nist.gov [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Maryland Nanocenter, University of Maryland, College Park, Maryland 20742 (United States); Cannara, Rachel J. [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

    2015-07-15

    Piezoelectric actuation of atomic force microscope (AFM) cantilevers often suffers from spurious mechanical resonances in the loop between the signal driving the cantilever and the actual tip motion. These spurious resonances can reduce the accuracy of AFM measurements and in some cases completely obscure the cantilever response. To address these limitations, we developed a specialized AFM cantilever holder for electrostatic actuation of AFM cantilevers. The holder contains electrical contacts for the AFM cantilever chip, as well as an electrode (or electrodes) that may be precisely positioned with respect to the back of the cantilever. By controlling the voltages on the AFM cantilever and the actuation electrode(s), an electrostatic force is applied directly to the cantilever, providing a near-ideal transfer function from drive signal to tip motion. We demonstrate both static and dynamic actuations, achieved through the application of direct current and alternating current voltage schemes, respectively. As an example application, we explore contact resonance atomic force microscopy, which is a technique for measuring the mechanical properties of surfaces on the sub-micron length scale. Using multiple electrodes, we also show that the torsional resonances of the AFM cantilever may be excited electrostatically, opening the door for advanced dynamic lateral force measurements with improved accuracy and precision.

  13. Simulating atomic force microscope images with density functional theory: The role of nonclassical contributions to the force

    Science.gov (United States)

    Schaffhauser, Philipp; Kümmel, Stephan

    2016-07-01

    We discuss a scheme for calculating atomic force microscope images within the framework of density functional theory (DFT). As in earlier works [T. L. Chan et al., Phys. Rev. Lett. 102, 176101 (2009), 10.1103/PhysRevLett.102.176101; M. Kim and J. R. Chelikowsky, Appl. Surf. Sci. 303, 163 (2014), 10.1016/j.apsusc.2014.02.127] we do not simulate the cantilever explicitly, but consider it as a polarizable object. We go beyond previous studies by discussing the role of exchange and correlation effects; i.e., we approximately take into account the Pauli interaction between sample and cantilever. The good agreement that we find when comparing our calculated images to experimental images for the difficult case of the 8-hydroxyquinoline molecule demonstrates that exchange-correlation effects can play an important role in the DFT-based interpretation of AFM images.

  14. Observation on Surface and Cross Section of Thin Film Solar Cells Using Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    FENG Liang-huan; WU Li-li; CAI Wei; CAI Ya-ping; ZHENG Jia-gui; ZHANG Jing-quan; LI Bing; LI Wei

    2005-01-01

    Atomic force microscope (AFM) is able to produce three-dimensional digital data in both forcemode and height-mode and its applications are not limited to map the surfaces of conducting materials. It can use the force-mode to image the repulsive and attractive force patterns. The cross sections of polycrystalline CdS/CdTe and amorphous silicon heterojunction solar cells are observed with AFM. In case of short circuit,the microstructures of different layers in the samples are clearly displayed. When the cells are open circuit, the topographical images are altered, the potential outline due to the space charge in junction region is observed.Obviously, AFM can be employed to investigate experimentally built-in potential in junction of semiconductor devices, such as solar cells.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. A virtual instrument to standardise the calibration of atomic force microscope cantilevers

    CERN Document Server

    Sader, John E; Gibson, Christopher T; Haviland, David B; Higgins, Michael J; Kilpatrick, Jason I; Lu, Jianing; Mulvaney, Paul; Shearer, Cameron J; Slattery, Ashley D; Thorén, Per-Anders; Tran, Jim; Zhang, Heyou; Zhang, Hongrui; Zheng, Tian

    2016-01-01

    Atomic force microscope (AFM) users often calibrate the spring constants of cantilevers using functionality built into individual instruments. This is performed without reference to a global standard, which hinders robust comparison of force measurements reported by different laboratories. In this article, we describe a virtual instrument (an internet-based initiative) whereby users from all laboratories can instantly and quantitatively compare their calibration measurements to those of others - standardising AFM force measurements - and simultaneously enabling non-invasive calibration of AFM cantilevers of any geometry. This global calibration initiative requires no additional instrumentation or data processing on the part of the user. It utilises a single website where users upload currently available data. A proof-of-principle demonstration of this initiative is presented using measured data from five independent laboratories across three countries, which also allows for an assessment of current calibratio...

  20. 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.

  1. 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

  2. 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

  3. [Atomic force field FFsol for calculation of molecular interactions of in water environment].

    Science.gov (United States)

    Pereiaslavets, L B; Finkel'shtein, A V

    2010-01-01

    Detailed calculations of protein interactions with explicitly considered water takes enormous computer time. The calculation becomes faster if water is considered implicitly (as a continuous media rather than as molecules); however, these calculations are much less precise, unless one uses an additional (and also volumes) computation of the solvent-accessible areas of protein atoms. The aim of our study was to obtain parameters for non-bonded atom-atom interactions for the case when water surrounding is considered implicitly and the solvent-accessible areas are not computed. Since the "in-vacuum" interactions of atoms are obtained from experimental structures of crystals and enthalpies of their sublimation, the "in-water" interactions of atoms must be corrected using solvation free energies of molecules, which can be obtained from the Henry constants. Taken 58 structures of molecular crystals and thermodynamic data on their sublimation and solubility, we obtained parameters for "in-water" attraction and repulsion of atoms typical of protein structures (H, C, N, O, S) in various covalently-bonded states, as well as parameters for electrostatic interactions. All necessary for calculations parameters of covalent interactions have been taken from the ENCAD force field, and partial charges of all atoms of separate molecules of a crystal have been obtained from quantum-mechanical calculations. The sought parameters of the "in-water" van der Waals and electrostatic interactions were optimized so as to achieve the best description of equilibrium crystal structures and their sublimation and solvation at the room temperature. With the optimized parameters, the average error in calculation of the effective cohesion energy of molecules in crystals was less than 10% both in the "in-vacuum" and "in-water" cases. PMID:20586195

  4. 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)

  5. Optical Force on Two-level Atoms by Few-cycle Pulsed Gaussian Laser field beyond the Rotating Wave Approximation

    OpenAIRE

    Kumar, Parvendra; Sarma, Amarendra K.

    2011-01-01

    We report a study on light force on a beam of neutral two-level atoms superimposed upon a few-cycle pulsed Gaussian laser field under both resonant and off-resonant condition. The phenomena of focusing, defocusing and steering of the neutral atoms in the laser field is analysed by solving the optical Bloch equation beyond the rotating wave approximation and the force equation self-consistently .We find that two-level atoms in an atomic beam could be focused and defocused for large, positively...

  6. 'Sub-atomic' resolution of non-contact atomic force microscope images induced by a heterogeneous tip structure: a density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Campbellova, Anna; Klapetek, Petr [Czech Metrology Institute, OkruznI 31, 638 00, Brno (Czech Republic); Ondracek, Martin; JelInek, Pavel [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 00 Prague (Czech Republic); Pou, Pablo; Perez, Ruben, E-mail: jelinekp@fzu.cz [Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2011-07-22

    A Si adatom on a Si(111)-(7 x 7) reconstructed surface is a typical atomic feature that can rather easily be imaged by a non-contact atomic force microscope (nc-AFM) and can be thus used to test the atomic resolution of the microscope. Based on our first principles density functional theory (DFT) calculations, we demonstrate that the structure of the termination of the AFM tip plays a decisive role in determining the appearance of the adatom image. We show how the AFM image changes depending on the tip-surface distance and the composition of the atomic apex at the end of the tip. We also demonstrate that contaminated tips may give rise to image patterns displaying so-called 'sub-atomic' features even in the attractive force regime.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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)

  13. Nanoscale spatially resolved simultaneous measurement of in-plane and out-of-plane force components on surfaces: a novel operational mode in atomic force microscopy

    Science.gov (United States)

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

    2002-11-01

    The atomic force microscope (AFM) allows investigation of the properties of surfaces and interfaces at atomic scale resolution. However, several different operational modes, (imaging, force versus distance and lateral force modes), need to be deployed in order to gain insight into the structure, tribological and mechanical properties. A new method, based on a variation of the force versus distance mode, has been developed. In essence, a coupling of the deformational modes of the probe is exploited whereby the tip is induced to undergo lateral travel in response to application of an out-of-plane force (and thus normal bending of the force-sensing lever). The lateral travel induces in-plane forces that are then measurable as a consequence of stimulation of the 'buckling' deformational mode of the lever. Due to the lever geometry, the technique offers an increase in resolution of an order of magnitude over existing AFM methods for measurement of atomic scale stick-slip events. In addition, the method allows measurement of the lateral deformation of the sample as well as scanner calibration. Outcomes will be demonstrated for atomically flat surfaces such as WTe2 and highly oriented pyrolytic graphite.

  14. 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.

  15. 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.

  16. Hidden momentum in a hydrogen atom and the Lorentz force law

    CERN Document Server

    Filho, J S Oliveira

    2015-01-01

    By using perturbation theory, we show that an hydrogen atom with magnetic moment due to the orbital angular momentum of the electron has hidden momentum in the presence of an external electric field. This means that the atomic electronic cloud has a nonzero linear momentum in its center of mass rest frame due to a relativistic effect. This is completely analogous to the hidden momentum that a classical current loop has in the presence of an external electric field. We discuss that this effect is essential for the validity of the Lorentz force law in quantum systems. We also connect our results to the secular Abraham-Minkowski debate about the momentum of light in material media.

  17. 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

  18. Development of nanomanipulator using a high-speed atomic force microscope coupled with a haptic device

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, F., E-mail: tmfiwat@ipc.shizuoka.ac.jp [Faculty of Engineering, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8011 (Japan); Ohashi, Y.; Ishisaki, I. [Faculty of Engineering, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Picco, L.M. [H Will Physics Laboratory and IRC in Nanotechnology, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Ushiki, T. [Graduate School of Medical and Dental Sciences, Niigata University, Asahimachidori, Niigata, 951-8122 (Japan)

    2013-10-15

    The atomic force microscope (AFM) has been widely used for surface fabrication and manipulation. However, nanomanipulation using a conventional AFM is inefficient because of the sequential nature of the scan-manipulation scan cycle, which makes it difficult for the operator to observe the region of interest and perform the manipulation simultaneously. In this paper, a nanomanipulation technique using a high-speed atomic force microscope (HS-AFM) is described. During manipulation using the AFM probe, the operation is periodically interrupted for a fraction of a second for high-speed imaging that allows the topographical image of the manipulated surface to be periodically updated. With the use of high-speed imaging, the interrupting time for imaging can be greatly reduced, and as a result, the operator almost does not notice the blink time of the interruption for imaging during the manipulation. This creates a more intuitive interface with greater feedback and finesse to the operator. Nanofabrication under real-time monitoring was performed to demonstrate the utility of this arrangement for real-time nanomanipulation of sample surfaces under ambient conditions. Furthermore, the HS-AFM is coupled with a haptic device for the human interface, enabling the operator to move the HS-AFM probe to any position on the surface while feeling the response from the surface during the manipulation. - Highlights: • A nanomanipulater based on a high-speed atomic force microscope was developped. • High-speed imaging provides a valuable feedback during the manipulation operation. • Operator can feel the response from the surface via a haptic device during manipulation. • Nanofabrications under real-time monitoring were successfully performed.

  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. 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.

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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 ...

  7. 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.

  8. 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

  9. Track sensitivity and the surface roughness measurements of CR-39 with atomic force microscope

    CERN Document Server

    Yasuda, N; Amemiya, K; Takahashi, H; Kyan, A; Ogura, K

    1999-01-01

    Atomic Force Microscope (AFM) has been applied to evaluate the surface roughness and the track sensitivity of CR-39 track detector. We experimentally confirmed the inverse correlation between the track sensitivity and the roughness of the detector surface after etching. The surface of CR-39 (CR-39 doped with antioxidant (HARZLAS (TD-1)) and copolymer of CR-39/NIPAAm (TNF-1)) with high sensitivity becomes rough by the etching, while the pure CR-39 (BARYOTRAK) with low sensitivity keeps its original surface clarity even for the long etching.

  10. 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...

  11. 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

  12. 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...

  13. A Study on HA Titanium Surface with Atomic Force Microscope (AFM)

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Three kinds of titanium surface especially the HA surface are analyzed. Titanium was treated by 3 kinds of methods that were acid & alkali, calcic solution and apatite solution. Samples were observed by optic microscope and atomic force microscope ( AFM). The typical surface morphology of the acid and alkali group is little holes, and on the two HA surface the tiny protuberances is typical. The surface treated by apatite solution was smoother than the two formers. The rough surface treated with acid and alkali was propitious to Ca + , Pand proteins' adhesion, and the relatively smooth HA surface was of benefit to the cell adhesion.

  14. 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.

  15. 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.

  16. Reliable measurement of elastic modulus of cells by nanoindentation in an atomic force microscope

    KAUST Repository

    Zhou, Zhoulong

    2012-04-01

    The elastic modulus of an oral cancer cell line UM1 is investigated by nanoindentation in an atomic force microscope with a flat-ended tip. The commonly used Hertzian method gives apparent elastic modulus which increases with the loading rate, indicating strong effects of viscoelasticity. On the contrary, a rate-jump method developed for viscoelastic materials gives elastic modulus values which are independent of the rate-jump magnitude. The results show that the rate-jump method can be used as a standard protocol for measuring elastic stiffness of living cells, since the measured values are intrinsic properties of the cells. © 2011 Elsevier Ltd.

  17. Aligning DNA on Si surface and cutting off by tips of atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    DNA is a kind of promising molecule as nano-lead to build or connect nano-devices due to its stable linear structure and certain conductivity. Many methods have been applied to constructing nano-patterns by using DNA molecule. In this report it is presented that (-DNA was aligned on Si substrate by using the free-flowing method and then imaged by an atomic force microscope (AFM). After the second liquid flow, a catenary-like pattern and a crossed network of -DNA were formed. In addition, the aligned (-DNA was successfully cut off by tips of AFM.

  18. 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.

  19. Micropore Structure Representation of Sandstone in Petroleum Reservoirs Using an Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    BAI Yong-Qiang; ZHU Xing; WU Jun-Zheng; BAI Wen-Guang

    2011-01-01

    @@ The pore structure of sandstone in an oil reservoir is investigated using atomic force microscopy(AFM).At nanoscale resolution,AFM images of sandstone show us the fine structure.The real height data of images display the three-dimensional space structure of sandstone effectively.The three-dimensional analysis results show that the AFM images of sandstone have unique characteristics that,like fingerprints,can identify different structural properties of sandstones.The results demonstrate that AFM is an effective method used to represent original sandstone in petroleum reservoirs,and may help geologists to appreciate the sandstone in oil reservoirs fully.

  20. 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

  1. 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...

  2. 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.

  3. 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.

  4. 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...

  5. 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.

  6. 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.

  7. Visualization of interaction between ribosome-inactivating proteins and supercoiled DNA with an atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    吴晓华; 刘望夷; 欧阳振乾; 李民乾

    1997-01-01

    The interaction between ribosome-inactivating proteins (RIPs) and supercoiled DNA was observed with an atomic force microscope (AFM). It was found that RIPs can bind to both supercoiled DNA and the unwound double stranded loop region in supercoiled DNA. The RIPs hound to the supercoils can induce the conformational change of supercoiled DNA. Furthermore, the supercoiled DNA was relaxed and cleaved into nick or linear form by RIPs. It indicated that RIP seemed to be a supercoil-dependent DNA binding protein and exhibited the activity of su-percoil-dependent DNA endonuclease.

  8. 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.

  9. 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

  10. Quantitative measurements of electromechanical response with a combined optical beam and interferometric atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Labuda, Aleksander; Proksch, Roger [Asylum Research an Oxford Instruments Company, Santa Barbara, California 93117 (United States)

    2015-06-22

    An ongoing challenge in atomic force microscope (AFM) experiments is the quantitative measurement of cantilever motion. The vast majority of AFMs use the optical beam deflection (OBD) method to infer the deflection of the cantilever. The OBD method is easy to implement, has impressive noise performance, and tends to be mechanically robust. However, it represents an indirect measurement of the cantilever displacement, since it is fundamentally an angular rather than a displacement measurement. Here, we demonstrate a metrological AFM that combines an OBD sensor with a laser Doppler vibrometer (LDV) to enable accurate measurements of the cantilever velocity and displacement. The OBD/LDV AFM allows a host of quantitative measurements to be performed, including in-situ measurements of cantilever oscillation modes in piezoresponse force microscopy. As an example application, we demonstrate how this instrument can be used for accurate quantification of piezoelectric sensitivity—a longstanding goal in the electromechanical community.

  11. 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)

  12. 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.

  13. 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.

  14. 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.

  15. Surface Electromechanical Coupling on DLC Film with Conductive Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    朱守星; 丁建宁; 范真; 李长生; 蔡兰; 杨继昌

    2004-01-01

    Diamond-like carbon (DLC) film composed of microscopically insulation but microscopically a mixture of conducting (sp2) and insulating (spa) phases was discussed on the local modification with a conductive atomic force microscope (C-AFM). Especially, a topographic change was observed when a direct current (DC) bias-voltage was applied to the DLC film. Experimental results show that a nanoscale pit on DLC surface was formed when applying a positive 25 V on DLC film. According to the interacting force between CoCr-coated microelectronic scanning probe (MESP) tip and DLC surface, as well as the Sondheimer oscillation theory, the "scalewing effect" of the pit was explained. Electromechanical coupling on DLC film suggested that the depth of pits increased with an increase of load applied to surface when the cantilever-deflected signal was less than a certain threshold voltage.

  16. 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.

  17. Effect of cholesterol on the physical properties of pulmonary surfactant films: Atomic force measurements study

    International Nuclear Information System (INIS)

    Atomic force measurements were performed on supported pulmonary surfactant (PS) films to address the effect of cholesterol on the physical properties of lung surfactant films. We recently found that cholesterol in excess of a physiological proportion abolishes surfactant function, and is the reason that surfactant fails to lower the surface tension upon compression. In this study, we investigated how the loss of mechanical stability observed earlier is related to the local mechanical properties of the film by local force measurements. The presence of 20% of cholesterol in bovine lipid extract surfactant (BLES) resulted in a decrease of the observed adhesive interaction, and an increase in rigidity of the film. We discuss the implication the increased rigidity might have on the functional failure of PS

  18. Biophysical Measurements of Cells, Microtubules, and DNA with an Atomic Force Microscope

    CERN Document Server

    Devenica, Luka M; Cabrejo, Raysa; Kurek, Matthew; Deveney, Edward F; Carter, Ashley R

    2015-01-01

    Atomic force microscopes (AFMs) are ubiquitous in research laboratories and have recently been priced for use in teaching laboratories. Here we review several AFM platforms (Dimension 3000 by Digital Instruments, EasyScan2 by Nanosurf, ezAFM by Nanomagnetics, and TKAFM by Thorlabs) and describe various biophysical experiments that could be done in the teaching laboratory using these instruments. In particular, we focus on experiments that image biological materials and quantify biophysical parameters: 1) imaging cells to determine membrane tension, 2) imaging microtubules to determine their persistence length, 3) imaging the random walk of DNA molecules to determine their contour length, and 4) imaging stretched DNA molecules to measure the tensional force.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Imaging and Manipulating Molecules on a Zeolite Surface with an Atomic Force Microscope

    Science.gov (United States)

    Weisenhorn, A. L.; Mac Dougall, J. E.; Gould, S. A. C.; Cox, S. D.; Wise, W. S.; Massie, J.; Maivald, P.; Elings, V. B.; Stucky, G. D.; Hansma, P. K.

    1990-03-01

    The adsorption of neutral molecules and ions on the surfaces of zeolites was observed in real time with an atomic force microscope (AFM). Direct imaging of the surface of the zeolite clinoptilolite was possible by using a diluted tert-butyl ammonium chloride solution as a medium. Images of the crystal in different liquids revealed that molecules could be bound to the surface in different ways; neutral molecules of tert-butanol formed an ordered array, whereas tert-butyl ammonium ions formed clusters. These absorbed molecules were not rearranged by the AFM tip when used in an imaging mode. However, when a sufficiently large force was applied, the tip of the AFM could rearrange the tert-butyl ammonium ions on the zeolite surface. This demonstration of molecular manipulation suggests new applications, including biosensors and lithography.

  5. 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.

  6. 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.

  7. 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

  8. An Atomic Force Microscope with Dual Actuation Capability for Biomolecular Experiments

    Science.gov (United States)

    Sevim, Semih; Shamsudhin, Naveen; Ozer, Sevil; Feng, Luying; Fakhraee, Arielle; Ergeneman, Olgaç; Pané, Salvador; Nelson, Bradley J.; Torun, Hamdi

    2016-06-01

    We report a modular atomic force microscope (AFM) design for biomolecular experiments. The AFM head uses readily available components and incorporates deflection-based optics and a piezotube-based cantilever actuator. Jetted-polymers have been used in the mechanical assembly, which allows rapid manufacturing. In addition, a FeCo-tipped electromagnet provides high-force cantilever actuation with vertical magnetic fields up to 0.55 T. Magnetic field calibration has been performed with a micro-hall sensor, which corresponds well with results from finite element magnetostatics simulations. An integrated force resolution of 1.82 and 2.98 pN, in air and in DI water, respectively was achieved in 1 kHz bandwidth with commercially available cantilevers made of Silicon Nitride. The controller and user interface are implemented on modular hardware to ensure scalability. The AFM can be operated in different modes, such as molecular pulling or force-clamp, by actuating the cantilever with the available actuators. The electromagnetic and piezoelectric actuation capabilities have been demonstrated in unbinding experiments of the biotin-streptavidin complex.

  9. 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.

  10. 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

  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. 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.

  13. Pairwise energies for polypeptide coarse-grained models derived from atomic force fields

    Science.gov (United States)

    Betancourt, Marcos R.; Omovie, Sheyore J.

    2009-05-01

    The energy parametrization of geometrically simplified versions of polypeptides, better known as polypeptide or protein coarse-grained models, is obtained from molecular dynamics and statistical methods. Residue pairwise interactions are derived by performing atomic-level simulations in explicit water for all 210 pairs of amino acids, where the amino acids are modified to closer match their structure and charges in polypeptides. Radial density functions are computed from equilibrium simulations for each pair of residues, from which statistical energies are extracted using the Boltzmann inversion method. The resulting models are compared to similar potentials obtained by knowledge based methods and to hydrophobic scales, resulting in significant similarities in spite of the model simplicity. However, it was found that glutamine, asparagine, lysine, and arginine are more attractive to other residues than anticipated, in part, due to their amphiphilic nature. In addition, equally charged residues appear more repulsive than expected. Difficulties in the calculation of knowledge based potentials and hydrophobicity scale for these cases, as well as sensitivity of the force field to polarization effects are suspected to cause this discrepancy. It is also shown that the coarse-grained model can identify native structures in decoy databases nearly as well as more elaborate knowledge based methods, in spite of its resolution limitations. In a test conducted with several proteins and corresponding decoys, the coarse-grained potential was able to identify the native state structure but not the original atomic force field.

  14. Combined laser and atomic force microscope lithography on aluminum: Mask fabrication for nanoelectromechanical systems

    DEFF Research Database (Denmark)

    Berini, Abadal Gabriel; Boisen, Anja; Davis, Zachary James;

    1999-01-01

    A direct-write laser system and an atomic force microscope (AFM) are combined to modify thin layers of aluminum on an oxidized silicon substrate, in order to fabricate conducting and robust etch masks with submicron features. These masks are very well suited for the production of nanoelectromecha......A direct-write laser system and an atomic force microscope (AFM) are combined to modify thin layers of aluminum on an oxidized silicon substrate, in order to fabricate conducting and robust etch masks with submicron features. These masks are very well suited for the production...... of nanoelectromechanical systems (NEMS) by reactive ion etching. In particular, the laser-modified areas can be subsequently locally oxidized by AFM and the oxidized regions can be selectively removed by chemical etching. This provides a straightforward means to define the overall conducting structure of a device by laser...... writing, and to perform submicron modifications by AFM oxidation. The mask fabrication for a nanoscale suspended resonator bridge is used to illustrate the advantages of this combined technique for NEMS. (C) 1999 American Institute of Physics. [S0003-6951(99)00221-1]....

  15. 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

  16. 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.

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

    Directory of Open Access Journals (Sweden)

    Ivanov YD

    2014-10-01

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

  18. Quantitative 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Biomolecular Force Field Parameterization via Atoms-in-Molecule Electron Density Partitioning.

    Science.gov (United States)

    Cole, Daniel J; Vilseck, Jonah Z; Tirado-Rives, Julian; Payne, Mike C; Jorgensen, William L

    2016-05-10

    Molecular mechanics force fields, which are commonly used in biomolecular modeling and computer-aided drug design, typically treat nonbonded interactions using a limited library of empirical parameters that are developed for small molecules. This approach does not account for polarization in larger molecules or proteins, and the parametrization process is labor-intensive. Using linear-scaling density functional theory and atoms-in-molecule electron density partitioning, environment-specific charges and Lennard-Jones parameters are derived directly from quantum mechanical calculations for use in biomolecular modeling of organic and biomolecular systems. The proposed methods significantly reduce the number of empirical parameters needed to construct molecular mechanics force fields, naturally include polarization effects in charge and Lennard-Jones parameters, and scale well to systems comprised of thousands of atoms, including proteins. The feasibility and benefits of this approach are demonstrated by computing free energies of hydration, properties of pure liquids, and the relative binding free energies of indole and benzofuran to the L99A mutant of T4 lysozyme. PMID:27057643

  7. 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)

  8. 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

  9. Uncertainty compensation methods for quantitative hardness measurement of materials using atomic force microscope nanoindentation technique

    International Nuclear Information System (INIS)

    We suggest uncertainty compensation methods for the quantification of nanoscale indentation using atomic force microscopy (AFM). The main error factors in the force–distance curves originated from the difference between theoretical and real shape of AFM tip during nanoscale indentation measurements. For the uncertainty compensations of tip shapes and misalignment of loading axis, we applied the enhanced tip geometry function and Y-scanner moving to the AFM measurements. Three different materials such as Si wafer, glass, and Au film were characterized with these compensation methods. By applying compensation methods, our results show the decreased values from 167% to 39% below 100 nm indenting depth compared with the literature values. These compensation methods applied to thin films will show the advanced quantitative analysis of hardness measurements using nanoscale indenting AFM. - Highlights: • We suggest uncertainty compensation methods for quantitative hardness measurement. • The main errors during indentation are tip geometry and non-uniform loading. • 3D tip characterization is obtained by using atomic force microscope scan. • The compensation methods perform well in thin films below thickness of 100 nm

  10. Atomic force spectroscopy and density-functional study of graphene corrugation on Ru(0001)

    Science.gov (United States)

    Voloshina, Elena; Dedkov, Yuriy

    2016-06-01

    Graphene, the thinnest material in the world, can form moiré structures on different substrates, including graphite, h -BN, or metal surfaces. In such systems, the structure of graphene, i.e., its corrugation, as well as its electronic and elastic properties, are defined by the combination of the system geometry and local interaction strength at the interface. The corrugation in such structures on metals is heavily extracted from diffraction or local probe microscopy experiments, and it can be obtained only via comparison with theoretical data, which usually simulate the experimental findings. Here we show that graphene corrugation on metals can be measured directly employing atomic force spectroscopy, and the obtained value coincides with state-of-the-art theoretical results. The presented results demonstrate an unexpected space selectivity for the Δ f (z ) signal in the atomic force spectroscopy in the moiré graphene lattice on Ru(0001), which is explained by the different response of the graphene layer on the indentation process. We also address the elastic reaction of the formed graphene nanodoms on the indentation process by the scanning tip that is important for the modeling and fabrication of graphene-based nanoresonators on the nanoscale.

  11. 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.

  12. Refined tip preparation by electrochemical etching and ultrahigh vacuum treatment to obtain atomically sharp tips for scanning tunneling microscope and atomic force microscope.

    Science.gov (United States)

    Hagedorn, Till; El Ouali, Mehdi; Paul, William; Oliver, David; Miyahara, Yoichi; Grütter, Peter

    2011-11-01

    A modification of the common electrochemical etching setup is presented. The described method reproducibly yields sharp tungsten tips for usage in the scanning tunneling microscope and tuning fork atomic force microscope. In situ treatment under ultrahigh vacuum (p ≤10(-10) mbar) conditions for cleaning and fine sharpening with minimal blunting is described. The structure of the microscopic apex of these tips is atomically resolved with field ion microscopy and cross checked with field emission.

  13. 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.

  14. Probing the interaction of individual amino acids with inorganic surfaces using atomic force spectroscopy.

    Science.gov (United States)

    Razvag, Yair; Gutkin, Vitaly; Reches, Meital

    2013-08-13

    This article describes single-molecule force spectroscopy measurements of the interaction between individual amino acid residues and inorganic surfaces in an aqueous solution. In each measurement, there is an amino acid residue, lysine, glutamate, phenylalanine, leucine, or glutamine, and each represents a class of amino acids (positively or negatively charged, aromatic, nonpolar, and polar). Force-distance curves measured the interaction of the individual amino acid bound to a silicon atomic force microscope (AFM) tip with a silcon substrate, cut from a single-crystal wafer, or mica. Using this method, we were able to measure low adhesion forces (below 300 pN) and could clearly determine the strength of interactions between the individual amino acid residues and the inorganic substrate. In addition, we observed how changes in the pH and ionic strength of the solution affected the adsorption of the residues to the substrates. Our results pinpoint the important role of hydrophobic interactions among the amino acids and the substrate, where hydrophobic phenylalanine exhibited the strongest adhesion to a silicon substrate. Additionally, electrostatic interactions also contributed to the adsorption of amino acid residues to inorganic substrates. A change in the pH or ionic strength values of the buffer altered the strength of interactions among the amino acids and the substrate. We concluded that the interplay between the hydrophobic forces and electrostatic interactions will determine the strength of adsorption among the amino acids and the surface. Overall, these results contribute to our understanding of the interaction at the organic-inorganic interface. These results may have implications for our perception of the specificity of peptide binding to inorganic surfaces. Consequently, it would possibly lead to a better design of composite materials and devices.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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...