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Sample records for atomic force microscopy-based

  1. Atomic Force Microscopy Based Cell Shape Index

    NASA Astrophysics Data System (ADS)

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

    PubMed

    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.

  3. Atomic force microscopy-based characterization and design of biointerfaces

    NASA Astrophysics Data System (ADS)

    Alsteens, David; Gaub, Hermann E.; Newton, Richard; Pfreundschuh, Moritz; Gerber, Christoph; Müller, Daniel J.

    2017-03-01

    Atomic force microscopy (AFM)-based methods have matured into a powerful nanoscopic platform, enabling the characterization of a wide range of biological and synthetic biointerfaces ranging from tissues, cells, membranes, proteins, nucleic acids and functional materials. Although the unprecedented signal-to-noise ratio of AFM enables the imaging of biological interfaces from the cellular to the molecular scale, AFM-based force spectroscopy allows their mechanical, chemical, conductive or electrostatic, and biological properties to be probed. The combination of AFM-based imaging and spectroscopy structurally maps these properties and allows their 3D manipulation with molecular precision. In this Review, we survey basic and advanced AFM-related approaches and evaluate their unique advantages and limitations in imaging, sensing, parameterizing and designing biointerfaces. It is anticipated that in the next decade these AFM-related techniques will have a profound influence on the way researchers view, characterize and construct biointerfaces, thereby helping to solve and address fundamental challenges that cannot be addressed with other techniques.

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

    SciTech Connect

    Xi, Xiaoning; Tittmann, Bernhard; Kim, Seong H.

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

    NASA Astrophysics Data System (ADS)

    Xi, Xiaoning; Kim, Seong H.; Tittmann, Bernhard

    2015-01-01

    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.

  6. Cutting forces related with lattice orientations of graphene using an atomic force microscopy based nanorobot

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Gao, Yang; Liu, Lianqing; Xi, Ning; Wang, Yuechao; Ma, Laipeng; Dong, Zaili; Wejinya, Uchechukwu C.

    2012-11-01

    The relationship between cutting forces and lattice orientations of monolayer graphene is investigated by using an atomic force microscopy (AFM) based nanorobot. In the beginning, the atomic resolution image of the graphene lattice is obtained by using an AFM. Then, graphene cutting experiments are performed with sample rotation method, which gets rid of the tip effect completely. The experimental results show that the cutting force along the armchair orientation is larger than the force along the zigzag orientation, and the cutting forces are almost identical every 60°, which corresponds well with the 60° symmetry in graphene honeycomb lattice structure. By using Poisson analysis method, the single cutting force along zigzag orientation is 3.9 nN, and the force along armchair is 20.5 nN. This work lays the experimental foundation to build a close-loop fabrication strategy with real-time force as a feedback sensor to control the cutting direction.

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

    PubMed Central

    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

  8. Atomic force microscopy based repeatable surface nanomachining for nanochannels on silicon substrates

    NASA Astrophysics Data System (ADS)

    Dong, Zhuxin; Wejinya, Uchechukwu C.

    2012-09-01

    The atomic force microscopy (AFM)-based repeatable nanomachining for nanochannels on bare silicon surfaces is investigated experimentally for automated nano manufacturing applications. The relationship between the normal force applied on the AFM cantilever and the channel depth is established and analyzed using both linear and logarithmic fits. Thus, current results can be regarded as the calibration reference in order to accurately predict the nanochannel depth for additional nanotechnology related applications. An accurate prediction of the depth is not only for accuracy and efficiency, but also to prevent a costly diamond tip from unnecessary wear and tear. Furthermore, the experimental results also reveal that the fabrication procedure is repeatable.

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

    NASA Astrophysics Data System (ADS)

    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

    PubMed Central

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

    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 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 (Eeff) 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. PMID:24194882

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

    PubMed

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

    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 of these cues show a significant influence on the cell elasticity assessment. Sharp AFM tips create a two-fold increase in the value of the effective Young's modulus (E(eff)) relative to that of the blunt tips. Higher indenting force at the same loading rate generates higher estimated cell elasticity. Increasing the operation temperature of the AFM leads to decreases in the cell stiffness because the structure of actin filaments becomes disorganized. The physiological cues include the presence of fetal bovine serum or extracellular matrix-coated surfaces, the culture passage number, and the culture density. Both fetal bovine serum and the extracellular matrix are critical for cells to maintain the integrity of actin filaments and consequently exhibit higher elasticity. Unlike primary cells, mouse kidney progenitor cells can be passaged and maintain their morphology and elasticity for a very long period without a senescence phenotype. Finally, cell elasticity increases with increasing culture density only in MDCK epithelial cells. In summary, for researchers who use AFM to assess cell elasticity, our results provide basic and significant information about the suitable selection of physical and physiological cues.

  12. Joint strength measurements of individual fiber-fiber bonds: An atomic force microscopy based method

    NASA Astrophysics Data System (ADS)

    Schmied, Franz J.; Teichert, Christian; Kappel, Lisbeth; Hirn, Ulrich; Schennach, Robert

    2012-07-01

    We are introducing a method to measure tensile strength of individual fiber-fiber bonds within a breaking force range of 0.01 mN-1 mN as well as the energy consumed during breaking. Until now, such a method was not available. Using a conventional atomic force microscope and a specifically designed sample holder, the desired force and the breaking behavior can be analyzed by two different approaches. First, dynamic loading can be applied, where force-versus-distance curves are employed to determine the proportions of elastic energy and energy dissipated in the bond. Second, static loading is utilized to study viscoelastic behavior and calculate viscoelastic energy contributions. To demonstrate the capability of the proposed method, we are presenting results for breaking strength of kraft pulp fiber-fiber bonds in tensile opening mode. The procedure is by no means restricted to cellulose fibers, it has the potential to quantify joint strength of micrometer-sized fibers in general.

  13. Atomic force microscopy based nanoassay: a new method to study α-Synuclein-dopamine bioaffinity interactions

    NASA Astrophysics Data System (ADS)

    Corvaglia, Stefania; Sanavio, Barbara; Hong Enriquez, Rolando P.; Sorce, Barbara; Bosco, Alessandro; Scaini, Denis; Sabella, Stefania; Pompa, Pier Paolo; Scoles, Giacinto; Casalis, Loredana

    2014-06-01

    Intrinsically Disordered Proteins (IDPs) are characterized by the lack of well-defined 3-D structure and show high conformational plasticity. For this reason, they are a strong challenge for the traditional characterization of structure, supramolecular assembly and biorecognition phenomena. We show here how the fine tuning of protein orientation on a surface turns useful in the reliable testing of biorecognition interactions of IDPs, in particular α-Synuclein. We exploited atomic force microscopy (AFM) for the selective, nanoscale confinement of α-Synuclein on gold to study the early stages of α-Synuclein aggregation and the effect of small molecules, like dopamine, on the aggregation process. Capitalizing on the high sensitivity of AFM topographic height measurements we determined, for the first time in the literature, the dissociation constant of dopamine-α-Synuclein adducts.

  14. Atomic force microscopy based nanoassay: a new method to study α-Synuclein-dopamine bioaffinity interactions

    NASA Astrophysics Data System (ADS)

    Corvaglia, Stefania; Sanavio, Barbara; Sorce, Barbara; Bosco, Alessandro; Sabella, Stefania; Pompa, Pierpaolo; Scoles, Giacinto; Casalis, Loredana

    2015-03-01

    Intrinsically Disordered Proteins (IDPs) are characterized by the lack of well-defined 3-D structure and show high conformational plasticity. For this reason, they are a strong challenge for the traditional characterization of structure, supramolecular assembly and biorecognition phenomena. We show here how the fine tuning of protein orientation on a surface turns useful in the reliable testing of biorecognition interactions of IDPs, in particular α-Synuclein. We exploited atomic force microscopy (AFM) for the selective, nanoscale confinement of α-Synuclein on gold to study the early stages of α-Synuclein aggregation and the effect of small molecules, like dopamine, on the aggregation process. Capitalizing on the high sensitivity of AFM topographic height measurements we determined, for the first time in the literature, the dissociation constant of dopamine- α-Synuclein adducts.

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

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

    We propose a novel approach in scanning thermal microscopy of layered samples. The thermal probe (ThP) (Wollaston wire) acts as a local a.c. heat source at the front of a sample layer deposited on a pyroelectric (PE) sensor. The PE signal is proportional to the heat wave transmitted through the sample. The ThP and PE signals can be used to generate complementary thermal conductivity maps and with some restrictions, thermal diffusivity maps of the sample. Additionally, the topography map is obtained in the usual way from the atomic force microscope. We give the theoretical background for the interpretation of PE signal obtained at low and at high frequency, and we demonstrate that it carries information on the thermal diffusivity of a test sample (12 μm thick PET polymer sheet). Finally, we discuss the contributions of heat transfer channels between ThP and sample, and the role of contact thermal resistance.

  16. Multiscale modeling and experimental validation for nanochannel depth control in atomic force microscopy-based nanofabrication

    SciTech Connect

    Ren, Jiaqi; Liu, Pinkuan Zhu, Xiaobo; Zhang, Fan; Chen, Guozhen

    2014-08-21

    Nanochannels are essential features of many microelectronic and biomedical devices. To date, the most commonly employed method to fabricate these nanochannels is atomic force microscopy (AFM). However, there is presently a very poor understanding on the fundamental principles underlying this process, which limits its reliability and controllability. In this study, we present a comprehensive multiscale model by incorporating strain gradient plasticity and strain gradient elasticity theories, which can predict nanochannel depths during AFM-based nanofabrication. The modeling results are directly verified with experiments performed on Cu and Pt substrates. As this model can also be extended to include many additional conditions, it has broad applicability in a wide range of AFM-based nanofabrication applications.

  17. Compact metal probes: a solution for atomic force microscopy based tip-enhanced Raman spectroscopy.

    PubMed

    Rodriguez, R D; Sheremet, E; Müller, S; Gordan, O D; Villabona, A; Schulze, S; Hietschold, M; Zahn, D R T

    2012-12-01

    There are many challenges in accomplishing tip-enhanced Raman spectroscopy (TERS) and obtaining a proper tip is probably the greatest one. Since tip size, composition, and geometry are the ultimate parameters that determine enhancement of intensity and lateral resolution, the tip becomes the most critical component in a TERS experiment. However, since the discovery of TERS the cantilevers used in atomic force microscopy (AFM) have remained basically the same: commercial silicon (or silicon nitride) tips covered by a metallic coating. The main issues of using metal-coated silicon cantilevers, such as wearing off of the metal layer or increased tip radius, can be completely overcome by using all-metal cantilevers. Until now in TERS experiments such probes have only been used in a scanning tunneling microscope or in a tuning fork-based shear force microscope but not in AFM. In this work for the first time, we show the use of compact silver cantilevers that are fully compatible with contact and tapping modes in AFM demonstrating their superb performance in TERS experiments.

  18. Atomic force microscopy based investigations of anti-inflammatory effects in lipopolysaccharide-stimulated macrophages.

    PubMed

    Pi, Jiang; Cai, Huaihong; Yang, Fen; Jin, Hua; Liu, Jianxin; Yang, Peihui; Cai, Jiye

    2016-01-01

    A new method based on atomic force microscopy (AFM) was developed to investigate the anti-inflammatory effects of drugs on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. The LPS-stimulated RAW264.7 macrophage cell line is a widely used in vitro cell model for the screening of anti-inflammatory drugs or the study of anti-inflammatory mechanisms. In this work, the inhibitory effects of dexamethasone and quercetin on LPS-CD14 receptor binding in RAW264.7 macrophages was probed by LPS-functionalized tips for the first time. Both dexamethasone and quercetin were found to inhibit LPS-induced NO production, iNOS expression, IκBα phosphorylation, and IKKα/β phosphorylation in RAW264.7 macrophages. The morphology and ultrastructure of RAW264.7 macrophages were determined by AFM, which indicated that dexamethasone and quercetin could inhibit LPS-induced cell surface particle size and roughness increase in RAW264.7 macrophages. The binding of LPS and its receptor in RAW264.7 macrophages was determined by LPS-functionalized AFM tips, which demonstrated that the binding force and binding probability between LPS and CD14 receptor on the surface of RAW264.7 macrophages were also inhibited by dexamethasone or quercetin treatment. The obtained results imply that AFM, which is very useful for the investigation of potential targets for anti-inflammatory drugs on native macrophages and the enhancement of our understanding of the anti-inflammatory effects of drugs, is expected to be developed into a promising tool for the study of anti-inflammatory drugs.

  19. Quantitative nanohistological investigation of scleroderma: an atomic force microscopy-based approach to disease characterization

    PubMed Central

    Strange, Adam P; Aguayo, Sebastian; Ahmed, Tarek; Mordan, Nicola; Stratton, Richard; Porter, Stephen R; Parekh, Susan; Bozec, Laurent

    2017-01-01

    Scleroderma (or systemic sclerosis, SSc) is a disease caused by excess crosslinking of collagen. The skin stiffens and becomes painful, while internally, organ function can be compromised by the less elastic collagen. Diagnosis of SSc is often only possible in advanced cases by which treatment time is limited. A more detailed analysis of SSc may provide better future treatment options and information of disease progression. Recently, the histological stain picrosirius red showing collagen register has been combined with atomic force microscopy (AFM) to study SSc. Skin from healthy individuals and SSc patients was biopsied, stained and studied using AFM. By investigating the crosslinking of collagen at a smaller hierarchical stage, the effects of SSc were more pronounced. Changes in morphology and Young’s elastic modulus were observed and quantified; giving rise to a novel technique, we have termed “quantitative nanohistology”. An increase in nanoscale stiffness in the collagen for SSc compared with healthy individuals was seen by a significant increase in the Young’s modulus profile for the collagen. These markers of stiffer collagen in SSc are similar to the symptoms experienced by patients, giving additional hope that in the future, nanohistology using AFM can be readily applied as a clinical tool, providing detailed information of the state of collagen. PMID:28138238

  20. Viscoelastic Properties Measurement of Human Lymphocytes by Atomic Force Microscopy Based on Magnetic Beads Cell Isolation.

    PubMed

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

    2016-03-28

    Cell mechanics has been proved to be an effective biomarker for indicating cellular states. The advent of atomic force microscopy (AFM) provides an exciting instrument for measuring the mechanical properties of single cells. However, current AFM single-cell mechanical measurements are commonly performed on cell lines cultured in vitro which are quite different from the primary cells in the human body. Investigating the mechanical properties of primary cells from clinical environments can help us to better understand cell behaviors. Here, by combining AFM with magnetic beads cell isolation, the viscoelastic properties of human primary B lymphocytes were quantitatively measured. B lymphocytes were isolated from the peripheral blood of healthy volunteers by density gradient centrifugation and CD19 magnetic beads cell isolation. The activity and specificity of the isolated cells were confirmed by fluorescence microscopy. AFM imaging revealed the surface topography and geometric parameters of B lymphocytes. The instantaneous modulus and relaxation time of living B lymphocytes were measured by AFM indenting technique, showing that the instantaneous modulus of human normal B lymphocytes was 2~3 kPa and the relaxation times were 0.03~0.06 s and 0.35~0.55 s. The differences in cellular visocoelastic properties between primary B lymphocytes and cell lines cultured in vitro were analyzed. The study proves the capability of AFM in quantifying the viscoelastic properties of individual specific primary cells from the blood sample of clinical patients, which will improve our understanding of the behaviors of cells in the human body.

  1. The study on the atomic force microscopy base nanoscale electrical discharge machining.

    PubMed

    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.

  2. Comparison of force sensors for atomic force microscopy based on quartz tuning forks and length-extensional resonators

    NASA Astrophysics Data System (ADS)

    Giessibl, Franz J.; Pielmeier, Florian; Eguchi, Toyoaki; An, Toshu; Hasegawa, Yukio

    2011-09-01

    The force sensor is key to the performance of atomic force microscopy (AFM). Nowadays, most atomic force microscopes use micromachined force sensors made from silicon, but piezoelectric quartz sensors are being applied at an increasing rate, mainly in vacuum. These self-sensing force sensors allow a relatively easy upgrade of a scanning tunneling microscope to a combined scanning tunneling/atomic force microscope. Two fundamentally different types of quartz sensors have achieved atomic resolution: the “needle sensor,” which is based on a length-extensional resonator, and the “qPlus sensor,” which is based on a tuning fork. Here, we calculate and measure the noise characteristics of these sensors. We find four noise sources: deflection detector noise, thermal noise, oscillator noise, and thermal drift noise. We calculate the effect of these noise sources as a factor of sensor stiffness, bandwidth, and oscillation amplitude. We find that for self-sensing quartz sensors, the deflection detector noise is independent of sensor stiffness, while the remaining three noise sources increase strongly with sensor stiffness. Deflection detector noise increases with bandwidth to the power of 1.5, while thermal noise and oscillator noise are proportional to the square root of the bandwidth. Thermal drift noise, however, is inversely proportional to bandwidth. The first three noise sources are inversely proportional to amplitude while thermal drift noise is independent of the amplitude. Thus, we show that the earlier finding that quoted an optimal signal-to-noise ratio for oscillation amplitudes similar to the range of the forces is still correct when considering all four frequency noise contributions. Finally, we suggest how the signal-to-noise ratio of the sensors can be improved further, we briefly discuss the challenges of mounting tips, and we compare the noise performance of self-sensing quartz sensors and optically detected Si cantilevers.

  3. Mapping of Proteomic Composition on the Surfaces of Bacillus spores by Atomic Force Microscopy-based Immunolabeling

    SciTech Connect

    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.

  4. Mapping of proteomic composition on the surfaces of bacillus spores by atomic force microscopy-based immunolabeling.

    PubMed

    Plomp, Marco; Malkin, Alexander J

    2009-01-06

    Atomic force microscopy (AFM) 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 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 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.

  5. Atomic force microscopy-based molecular studies on the recognition of immunogenic chlorinated ovalbumin by macrophage receptors.

    PubMed

    Zapotoczny, Szczepan; Biedroń, Rafał; Marcinkiewicz, Janusz; Nowakowska, Maria

    2012-02-01

    This report presents simple and reliable approach developed to study the specific recognition events between chlorinated ovalbumin (OVA) and macrophages using atomic force microscopy (AFM). Thanks to the elimination of nonspecific adhesion, the interactions of the native and chlorinated OVA with a membrane of macrophages could be quantified using exclusively the so-called adhesion frequency (AF). The proposed system not only enabled the application of AFM-based force measurements for such poorly defined ligand-receptor pairs but also significantly improved both the acquisition and the processing of the data. The proteins were immobilized on the gold-coated AFM tips from the aqueous solutions containing charged thiol adsorbates. Such surface dilution of the proteins ensured the presence of single or just a few macromolecules at the tip-surface contact. The formation of negatively charged monolayer on the tip dramatically limited its nonspecific interactions with the macrophage surface. In such systems, AF was used as a measure of the recognition events even if the interaction forces varied significantly for sets of measurements. The system with the native OVA, a weak immunogen, showed only negligible AF compared with 85% measured for the immunogenic chlorinated OVA. The AF values varied with the tip-macrophage contact time and loading velocity. Blocking of the receptors by the chlorinated OVA was also confirmed. The developed approach can be also used to study other ligand-receptor interactions in poorly defined biological systems with intrinsically broad distribution of the rupture forces, thus opening new fields for AFM-based recognition on molecular level.

  6. Label-free, atomic force microscopy-based mapping of DNA intrinsic curvature for the nanoscale comparative analysis of bent duplexes

    PubMed Central

    Buzio, Renato; Repetto, Luca; Giacopelli, Francesca; Ravazzolo, Roberto; Valbusa, Ugo

    2012-01-01

    We propose a method for the characterization of the local intrinsic curvature of adsorbed DNA molecules. It relies on a novel statistical chain descriptor, namely the ensemble averaged product of curvatures for two nanosized segments, symmetrically placed on the contour of atomic force microscopy imaged chains. We demonstrate by theoretical arguments and experimental investigation of representative samples that the fine mapping of the average product along the molecular backbone generates a characteristic pattern of variation that effectively highlights all pairs of DNA tracts with large intrinsic curvature. The centrosymmetric character of the chain descriptor enables targetting strands with unknown orientation. This overcomes a remarkable limitation of the current experimental strategies that estimate curvature maps solely from the trajectories of end-labeled molecules or palindromes. As a consequence our approach paves the way for a reliable, unbiased, label-free comparative analysis of bent duplexes, aimed to detect local conformational changes of physical or biological relevance in large sample numbers. Notably, such an assay is virtually inaccessible to the automated intrinsic curvature computation algorithms proposed so far. We foresee several challenging applications, including the validation of DNA adsorption and bending models by experiments and the discrimination of specimens for genetic screening purposes. PMID:22402493

  7. Force feedback microscopy based on an optical beam deflection scheme

    SciTech Connect

    Vitorino, Miguel V.; Rodrigues, Mario S.; Carpentier, Simon; Costa, Luca

    2014-07-07

    Force feedback microscopy circumvents the jump to contact in atomic force microscopy when using soft cantilevers and quantitatively measures the interaction properties at the nanoscale by simultaneously providing force, force gradient, and dissipation. The force feedback microscope developed so far used an optical cavity to measure the tip displacement. In this Letter, we show that the more conventional optical beam deflection scheme can be used to the same purpose. With this instrument, we have followed the evolution of the Brownian motion of the tip under the influence of a water bridge.

  8. Ion microscopy based on laser-cooled cesium atoms.

    PubMed

    Viteau, M; Reveillard, M; Kime, L; Rasser, B; Sudraud, P; Bruneau, Y; Khalili, G; Pillet, P; Comparat, D; Guerri, I; Fioretti, A; Ciampini, D; Allegrini, M; Fuso, F

    2016-05-01

    We demonstrate a prototype of a Focused Ion Beam machine based on the ionization of a laser-cooled cesium beam and adapted for imaging and modifying different surfaces in the few-tens nanometer range. Efficient atomic ionization is obtained by laser promoting ground-state atoms into a target excited Rydberg state, then field-ionizing them in an electric field gradient. The method allows obtaining ion currents up to 130pA. Comparison with the standard direct photo-ionization of the atomic beam shows, in our conditions, a 40-times larger ion yield. Preliminary imaging results at ion energies in the 1-5keV range are obtained with a resolution around 40nm, in the present version of the prototype. Our ion beam is expected to be extremely monochromatic, with an energy spread of the order of the eV, offering great prospects for lithography, imaging and surface analysis.

  9. Magnetoelectric force microscopy based on magnetic force microscopy with modulated electric field.

    PubMed

    Geng, Yanan; Wu, Weida

    2014-05-01

    We present the realization of a mesoscopic imaging technique, namely, the Magnetoelectric Force Microscopy (MeFM), for visualization of local magnetoelectric effect. The basic principle of MeFM is the lock-in detection of local magnetoelectric response, i.e., the electric field-induced magnetization, using magnetic force microscopy. We demonstrate MeFM capability by visualizing magnetoelectric domains on single crystals of multiferroic hexagonal manganites. Results of several control experiments exclude artifacts or extrinsic origins of the MeFM signal. The parameters are tuned to optimize the signal to noise ratio.

  10. Atomic Force Microscope

    SciTech Connect

    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.

  11. Deep atomic force microscopy

    SciTech Connect

    Barnard, H.; Drake, B.; Randall, C.; Hansma, P. K.

    2013-12-15

    The Atomic Force Microscope (AFM) possesses several desirable imaging features including the ability to produce height profiles as well as two-dimensional images, in fluid or air, at high resolution. AFM has been used to study a vast selection of samples on the scale of angstroms to micrometers. However, current AFMs cannot access samples with vertical topography of the order of 100 μm or greater. Research efforts have produced AFM scanners capable of vertical motion greater than 100 μm, but commercially available probe tip lengths are still typically less than 10 μm high. Even the longest probe tips are below 100 μm and even at this range are problematic. In this paper, we present a method to hand-fabricate “Deep AFM” probes with tips of the order of 100 μm and longer so that AFM can be used to image samples with large scale vertical topography, such as fractured bone samples.

  12. Atomic Force Microscope Operation

    NASA Technical Reports Server (NTRS)

    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.

  13. Sensing mode atomic force microscope

    DOEpatents

    Hough, Paul V. C.; Wang, Chengpu

    2006-08-22

    An atomic force microscope is described having a cantilever comprising a base and a probe tip on an end opposite the base; a cantilever drive device connected to the base; a magnetic material coupled to the probe tip, such that when an incrementally increasing magnetic field is applied to the magnetic material an incrementally increasing force will be applied to the probe tip; a moveable specimen base; and a controller constructed to obtain a profile height of a specimen at a point based upon a contact between the probe tip and a specimen, and measure an adhesion force between the probe tip and the specimen by, under control of a program, incrementally increasing an amount of a magnetic field until a release force, sufficient to break the contact, is applied. An imaging method for atomic force microscopy involving measuring a specimen profile height and adhesion force at multiple points within an area and concurrently displaying the profile and adhesion force for each of the points is also described. A microscope controller is also described and is constructed to, for a group of points, calculate a specimen height at a point based upon a cantilever deflection, a cantilever base position and a specimen piezo position; calculate an adhesion force between a probe tip and a specimen at the point by causing an incrementally increasing force to be applied to the probe tip until the probe tip separates from a specimen; and move the probe tip to a new point in the group.

  14. Sensing mode atomic force microscope

    DOEpatents

    Hough, Paul V.; Wang, Chengpu

    2004-11-16

    An atomic force microscope is described having a cantilever comprising a base and a probe tip on an end opposite the base; a cantilever drive device connected to the base; a magnetic material coupled to the probe tip, such that when an incrementally increasing magnetic field is applied to the magnetic material an incrementally increasing force will be applied to the probe tip; a moveable specimen base; and a controller constructed to obtain a profile height of a specimen at a point based upon a contact between the probe tip and a specimen, and measure an adhesion force between the probe tip and the specimen by, under control of a program, incrementally increasing an amount of a magnetic field until a release force, sufficient to break the contact, is applied. An imaging method for atomic force microscopy involving measuring a specimen profile height and adhesion force at multiple points within an area and concurrently displaying the profile and adhesion force for each of the points is also described. A microscope controller is also described and is constructed to, for a group of points, calculate a specimen height at a point based upon a cantilever deflection, a cantilever base position and a specimen piezo position; calculate an adhesion force between a probe tip and a specimen at the point by causing an incrementally increasing force to be applied to the probe tip until the probe tip separates from a specimen; and move the probe tip to a new point in the group.

  15. Coffee Cup Atomic Force Microscopy

    ERIC Educational Resources Information Center

    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…

  16. Coffee Cup Atomic Force Microscopy

    ERIC Educational Resources Information Center

    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…

  17. Cell Adhesion on Dynamic Supramolecular Surfaces Probed by Fluid Force Microscopy-Based Single-Cell Force Spectroscopy

    PubMed Central

    2017-01-01

    Biomimetic and stimuli-responsive cell-material interfaces are actively being developed to study and control various cell-dynamics phenomena. Since cells naturally reside in the highly dynamic and complex environment of the extracellular matrix, attempts are being made to replicate these conditions in synthetic biomaterials. Supramolecular chemistry, dealing with noncovalent interactions, has recently provided possibilities to incorporate such dynamicity and responsiveness in various types of architectures. Using a cucurbit[8]uril-based host–guest system, we have successfully established a dynamic and electrochemically responsive interface for the display of the integrin-specific ligand, Arg-Gly-Asp (RGD), to promote cell adhesion. Due to the weak nature of the noncovalent forces by which the components at the interface are held together, we expected that cell adhesion would also be weaker in comparison to traditional interfaces where ligands are usually immobilized by covalent linkages. To assess the stability and limitations of our noncovalent interfaces, we performed single-cell force spectroscopy studies using fluid force microscopy. This technique enabled us to measure rupture forces of multiple cells that were allowed to adhere for several hours on individual substrates. We found that the rupture forces of cells adhered to both the noncovalent and covalent interfaces were nearly identical for up to several hours. We have analyzed and elucidated the reasons behind this result as a combination of factors including the weak rupture force between linear Arg-Gly-Asp and integrin, high surface density of the ligand, and increase in effective concentration of the supramolecular components under spread cells. These characteristics enable the construction of highly dynamic biointerfaces without compromising cell-adhesive properties. PMID:28319669

  18. Cell Adhesion on Dynamic Supramolecular Surfaces Probed by Fluid Force Microscopy-Based Single-Cell Force Spectroscopy.

    PubMed

    Sankaran, Shrikrishnan; Jaatinen, Leena; Brinkmann, Jenny; Zambelli, Tomaso; Vörös, Janos; Jonkheijm, Pascal

    2017-04-25

    Biomimetic and stimuli-responsive cell-material interfaces are actively being developed to study and control various cell-dynamics phenomena. Since cells naturally reside in the highly dynamic and complex environment of the extracellular matrix, attempts are being made to replicate these conditions in synthetic biomaterials. Supramolecular chemistry, dealing with noncovalent interactions, has recently provided possibilities to incorporate such dynamicity and responsiveness in various types of architectures. Using a cucurbit[8]uril-based host-guest system, we have successfully established a dynamic and electrochemically responsive interface for the display of the integrin-specific ligand, Arg-Gly-Asp (RGD), to promote cell adhesion. Due to the weak nature of the noncovalent forces by which the components at the interface are held together, we expected that cell adhesion would also be weaker in comparison to traditional interfaces where ligands are usually immobilized by covalent linkages. To assess the stability and limitations of our noncovalent interfaces, we performed single-cell force spectroscopy studies using fluid force microscopy. This technique enabled us to measure rupture forces of multiple cells that were allowed to adhere for several hours on individual substrates. We found that the rupture forces of cells adhered to both the noncovalent and covalent interfaces were nearly identical for up to several hours. We have analyzed and elucidated the reasons behind this result as a combination of factors including the weak rupture force between linear Arg-Gly-Asp and integrin, high surface density of the ligand, and increase in effective concentration of the supramolecular components under spread cells. These characteristics enable the construction of highly dynamic biointerfaces without compromising cell-adhesive properties.

  19. Sensing mode atomic force microscope

    DOEpatents

    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.

  20. Quantum state atomic force microscopy

    DOE PAGES

    Passian, Ali; Siopsis, George

    2017-04-10

    New classical modalities of atomic force microscopy continue to emerge to achieve higher spatial, spectral, and temporal resolution for nanometrology of materials. Here, we introduce the concept of a quantum mechanical modality that capitalizes on squeezed states of probe displacement. We show that such squeezing is enabled nanomechanically when the probe enters the van der Waals regime of interaction with a sample. The effect is studied in the non-contact mode, where we consider the parameter domains characterizing the attractive regime of the probe-sample interaction force.

  1. Atomically resolved force microscopy at room temperature

    SciTech Connect

    Morita, Seizo

    2014-04-24

    Atomic force microscopy (AFM) can now not only image individual atoms but also construct atom letters using atom manipulation method even at room temperature (RT). Therefore, the AFM is the second generation atomic tool following the scanning tunneling microscopy (STM). However the AFM can image even insulating atoms, and also directly measure/map the atomic force and potential at the atomic scale. Noting these advantages, we have been developing a bottom-up nanostructuring system at RT based on the AFM. It can identify chemical species of individual atoms and then manipulate selected atom species to the predesigned site one-by-one to assemble complex nanostructures consisted of multi atom species at RT. Here we introduce our results toward atom-by-atom assembly of composite nanostructures based on the AFM at RT including the latest result on atom gating of nano-space for atom-by-atom creation of atom clusters at RT for semiconductor surfaces.

  2. Rotational scanning atomic force microscopy.

    PubMed

    Ulčinas, A; Vaitekonis, Š

    2017-03-10

    A non-raster scanning technique for atomic force microscopy (AFM) imaging which combines rotational and translational motion is presented. The use of rotational motion for the fast scan axis allows us to significantly increase the scanning speed while imaging a large area (diameter > 30 μm). An image reconstruction algorithm and the factors influencing the resolution of the technique are discussed. The experimental results show the potential of the rotational scanning technique for high-throughput large area AFM investigation.

  3. Rotational scanning atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Ulčinas, A.; Vaitekonis, Š.

    2017-03-01

    A non-raster scanning technique for atomic force microscopy (AFM) imaging which combines rotational and translational motion is presented. The use of rotational motion for the fast scan axis allows us to significantly increase the scanning speed while imaging a large area (diameter > 30 μm). An image reconstruction algorithm and the factors influencing the resolution of the technique are discussed. The experimental results show the potential of the rotational scanning technique for high-throughput large area AFM investigation.

  4. Modeling noncontact atomic force microscopy resolution on corrugated surfaces.

    PubMed

    Burson, Kristen M; Yamamoto, Mahito; Cullen, William G

    2012-01-01

    Key developments in NC-AFM have generally involved atomically flat crystalline surfaces. However, many surfaces of technological interest are not atomically flat. We discuss the experimental difficulties in obtaining high-resolution images of rough surfaces, with amorphous SiO(2) as a specific case. We develop a quasi-1-D minimal model for noncontact atomic force microscopy, based on van der Waals interactions between a spherical tip and the surface, explicitly accounting for the corrugated substrate (modeled as a sinusoid). The model results show an attenuation of the topographic contours by ~30% for tip distances within 5 Å of the surface. Results also indicate a deviation from the Hamaker force law for a sphere interacting with a flat surface.

  5. Minimizing Pulling Geometry Errors in Atomic Force Microscope Single Molecule Force Spectroscopy

    PubMed Central

    Rivera, Monica; Lee, Whasil; Ke, Changhong; Marszalek, Piotr E.; Cole, Daniel G.; Clark, Robert L.

    2008-01-01

    In atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS), it is assumed that the pulling angle is negligible and that the force applied to the molecule is equivalent to the force measured by the instrument. Recent studies, however, have indicated that the pulling geometry errors can drastically alter the measured force-extension relationship of molecules. Here we describe a software-based alignment method that repositions the cantilever such that it is located directly above the molecule's substrate attachment site. By aligning the applied force with the measurement axis, the molecule is no longer undergoing combined loading, and the full force can be measured by the cantilever. Simulations and experimental results verify the ability of the alignment program to minimize pulling geometry errors in AFM-SMFS studies. PMID:18641069

  6. Minimizing pulling geometry errors in atomic force microscope single molecule force spectroscopy.

    PubMed

    Rivera, Monica; Lee, Whasil; Ke, Changhong; Marszalek, Piotr E; Cole, Daniel G; Clark, Robert L

    2008-10-01

    In atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS), it is assumed that the pulling angle is negligible and that the force applied to the molecule is equivalent to the force measured by the instrument. Recent studies, however, have indicated that the pulling geometry errors can drastically alter the measured force-extension relationship of molecules. Here we describe a software-based alignment method that repositions the cantilever such that it is located directly above the molecule's substrate attachment site. By aligning the applied force with the measurement axis, the molecule is no longer undergoing combined loading, and the full force can be measured by the cantilever. Simulations and experimental results verify the ability of the alignment program to minimize pulling geometry errors in AFM-SMFS studies.

  7. Hydrogen-related contrast in atomic force microscopy.

    PubMed

    Schmidt, René; Schwarz, Alexander; Wiesendanger, Roland

    2009-07-01

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

  8. Hydrogen-related contrast in atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Schmidt, René; Schwarz, Alexander; Wiesendanger, Roland

    2009-07-01

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

  9. Nanorheology by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Li, Tai-De; Chiu, Hsiang-Chih; Ortiz-Young, Deborah; Riedo, Elisa

    2014-12-01

    We present an Atomic Force Microscopy (AFM) based method to investigate the rheological properties of liquids confined within a nanosize gap formed by an AFM tip apex and a solid substrate. In this method, a conventional AFM cantilever is sheared parallel to a substrate surface by means of a lock-in amplifier while it is approaching and retracting from the substrate in liquid. The normal solvation forces and lateral viscoelastic shear forces experienced by the AFM tip in liquid can be simultaneously measured as a function of the tip-substrate distance with sub-nanometer vertical resolution. A new calibration method is applied to compensate for the linear drift of the piezo transducer and substrate system, leading to a more precise determination of the tip-substrate distance. By monitoring the phase lag between the driving signal and the cantilever response in liquid, the frequency dependent viscoelastic properties of the confined liquid can also be derived. Finally, we discuss the results obtained with this technique from different liquid-solid interfaces. Namely, octamethylcyclotetrasiloxane and water on mica and highly oriented pyrolytic graphite.

  10. Nanorheology by atomic force microscopy

    SciTech Connect

    Li, Tai-De; Chiu, Hsiang-Chih; Ortiz-Young, Deborah; Riedo, Elisa

    2014-12-15

    We present an Atomic Force Microscopy (AFM) based method to investigate the rheological properties of liquids confined within a nanosize gap formed by an AFM tip apex and a solid substrate. In this method, a conventional AFM cantilever is sheared parallel to a substrate surface by means of a lock-in amplifier while it is approaching and retracting from the substrate in liquid. The normal solvation forces and lateral viscoelastic shear forces experienced by the AFM tip in liquid can be simultaneously measured as a function of the tip-substrate distance with sub-nanometer vertical resolution. A new calibration method is applied to compensate for the linear drift of the piezo transducer and substrate system, leading to a more precise determination of the tip-substrate distance. By monitoring the phase lag between the driving signal and the cantilever response in liquid, the frequency dependent viscoelastic properties of the confined liquid can also be derived. Finally, we discuss the results obtained with this technique from different liquid-solid interfaces. Namely, octamethylcyclotetrasiloxane and water on mica and highly oriented pyrolytic graphite.

  11. Nanorheology by atomic force microscopy.

    PubMed

    Li, Tai-De; Chiu, Hsiang-Chih; Ortiz-Young, Deborah; Riedo, Elisa

    2014-12-01

    We present an Atomic Force Microscopy (AFM) based method to investigate the rheological properties of liquids confined within a nanosize gap formed by an AFM tip apex and a solid substrate. In this method, a conventional AFM cantilever is sheared parallel to a substrate surface by means of a lock-in amplifier while it is approaching and retracting from the substrate in liquid. The normal solvation forces and lateral viscoelastic shear forces experienced by the AFM tip in liquid can be simultaneously measured as a function of the tip-substrate distance with sub-nanometer vertical resolution. A new calibration method is applied to compensate for the linear drift of the piezo transducer and substrate system, leading to a more precise determination of the tip-substrate distance. By monitoring the phase lag between the driving signal and the cantilever response in liquid, the frequency dependent viscoelastic properties of the confined liquid can also be derived. Finally, we discuss the results obtained with this technique from different liquid-solid interfaces. Namely, octamethylcyclotetrasiloxane and water on mica and highly oriented pyrolytic graphite.

  12. Hyperbaric Hydrothermal Atomic Force Microscope

    DOEpatents

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

    2003-07-01

    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. Hyperbaric hydrothermal atomic force microscope

    DOEpatents

    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.

  14. Atomic force microscopy as nanorobot.

    PubMed

    Xi, Ning; Fung, Carmen Kar Man; Yang, Ruiguo; Lai, King Wai Chiu; Wang, Donna H; Seiffert-Sinha, Kristina; Sinha, Animesh A; Li, Guangyong; Liu, Lianqing

    2011-01-01

    Atomic force microscopy (AFM) is a powerful and widely used imaging technique that can visualize single molecules under physiological condition at the nanometer scale. In this chapter, an AFM-based nanorobot for biological studies is introduced. Using the AFM tip as an end effector, the AFM can be modified into a nanorobot that can manipulate biological objects at the single-molecule level. By functionalizing the AFM tip with specific antibodies, the nanorobot is able to identify specific types of receptors on the cell membrane. It is similar to the fluorescent optical microscopy but with higher resolution. By locally updating the AFM image based on interaction force information and objects' model during nanomanipulation, real-time visual feedback is obtained through the augmented reality interface. The development of the AFM-based nanorobotic system enables us to conduct in situ imaging, sensing, and manipulation simultaneously at the nanometer scale (e.g., protein and DNA levels). The AFM-based nanorobotic system offers several advantages and capabilities for studying structure-function relationships of biological specimens. As a result, many biomedical applications can be achieved by the AFM-based nanorobotic system.

  15. Atomic Force Microscopy in Liquids

    NASA Astrophysics Data System (ADS)

    Weisenhorn, Albrecht Ludwig

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

  16. Atom world based on nano-forces: 25 years of atomic force microscopy.

    PubMed

    Morita, Seizo

    2011-01-01

    Scanning tunneling microscopy (STM) has opened up the new nanoworlds of scanning probe microscopy. STM is the first-generation atomic tool that can image, evaluate and manipulate individual atoms and consequently can create nanostructures by true bottom-up methods based on atom-by-atom manipulation. Atomic force microscopy is a second-generation atomic tool that has followed the footsteps of STM, and which is now opening doors to a new atom world based on using nanoscale forces.

  17. Atomic Force Microscopy Based Eddy Current Imaging and Characterization of Composite and Nanocomposite Materials (Preprint)

    DTIC Science & Technology

    2007-03-01

    TERMS Carbon Fiber Composites , Nondestructive Evaluation, Interface Analysis 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON... Carbon Fiber Composites , Nondestructive Evaluation, Interface Analysis 1. INTRODUCTION Ever since the development of carbon nanotubes by...both traditional carbon fiber composites as well as nano- carbon fiber composites . The results show that the technique can be successfully used to

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

    NASA Astrophysics Data System (ADS)

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

    2001-02-01

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

  19. Atomic Force Microscope Mediated Chromatography

    NASA Technical Reports Server (NTRS)

    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

  20. Atomic Force Controlled Capillary Electrophoresis

    NASA Astrophysics Data System (ADS)

    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.

  1. Equilibrium capillary forces with atomic force microscopy.

    PubMed

    Sprakel, J; Besseling, N A M; Leermakers, F A M; Cohen Stuart, M A

    2007-09-07

    We present measurements of equilibrium forces resulting from capillary condensation. The results give access to the ultralow interfacial tensions between the capillary bridge and the coexisting bulk phase. We demonstrate this with solutions of associative polymers and an aqueous mixture of gelatin and dextran, with interfacial tensions around 10 microN/m. The equilibrium nature of the capillary forces is attributed to the combination of a low interfacial tension and a microscopic confinement geometry, based on nucleation and growth arguments.

  2. Polynomial force approximations and multifrequency atomic force microscopy.

    PubMed

    Platz, Daniel; Forchheimer, Daniel; Tholén, Erik A; Haviland, David B

    2013-01-01

    We present polynomial force reconstruction from experimental intermodulation atomic force microscopy (ImAFM) data. We study the tip-surface force during a slow surface approach and compare the results with amplitude-dependence force spectroscopy (ADFS). Based on polynomial force reconstruction we generate high-resolution surface-property maps of polymer blend samples. The polynomial method is described as a special example of a more general approximative force reconstruction, where the aim is to determine model parameters that best approximate the measured force spectrum. This approximative approach is not limited to spectral data, and we demonstrate how it can be adapted to a force quadrature picture.

  3. Chemical identification of individual surface atoms by atomic force microscopy.

    PubMed

    Sugimoto, Yoshiaki; Pou, Pablo; Abe, Masayuki; Jelinek, Pavel; Pérez, Rubén; Morita, Seizo; Custance, Oscar

    2007-03-01

    Scanning probe microscopy is a versatile and powerful method that uses sharp tips to image, measure and manipulate matter at surfaces with atomic resolution. At cryogenic temperatures, scanning probe microscopy can even provide electron tunnelling spectra that serve as fingerprints of the vibrational properties of adsorbed molecules and of the electronic properties of magnetic impurity atoms, thereby allowing chemical identification. But in many instances, and particularly for insulating systems, determining the exact chemical composition of surfaces or nanostructures remains a considerable challenge. In principle, dynamic force microscopy should make it possible to overcome this problem: it can image insulator, semiconductor and metal surfaces with true atomic resolution, by detecting and precisely measuring the short-range forces that arise with the onset of chemical bonding between the tip and surface atoms and that depend sensitively on the chemical identity of the atoms involved. Here we report precise measurements of such short-range chemical forces, and show that their dependence on the force microscope tip used can be overcome through a normalization procedure. This allows us to use the chemical force measurements as the basis for atomic recognition, even at room temperature. We illustrate the performance of this approach by imaging the surface of a particularly challenging alloy system and successfully identifying the three constituent atomic species silicon, tin and lead, even though these exhibit very similar chemical properties and identical surface position preferences that render any discrimination attempt based on topographic measurements impossible.

  4. Magnetic exchange force microscopy with atomic resolution.

    PubMed

    Kaiser, Uwe; Schwarz, Alexander; Wiesendanger, Roland

    2007-03-29

    The ordering of neighbouring atomic magnetic moments (spins) leads to important collective phenomena such as ferromagnetism and antiferromagnetism. A full understanding of magnetism on the nanometre scale therefore calls for information on the arrangement of spins in real space and with atomic resolution. Spin-polarized scanning tunnelling microscopy accomplishes this but can probe only conducting materials. Force microscopy can be used on any sample independent of its conductivity. In particular, magnetic force microscopy is well suited to exploring ferromagnetic domain structures. However, atomic resolution cannot be achieved because data acquisition involves the sensing of long-range magnetostatic forces between tip and sample. Magnetic exchange force microscopy has been proposed for overcoming this limitation: by using an atomic force microscope with a magnetic tip, it should be possible to detect the short-range magnetic exchange force between tip and sample spins. Here we show for a prototypical antiferromagnetic insulator, the (001) surface of nickel oxide, that magnetic exchange force microscopy can indeed reveal the arrangement of both surface atoms and their spins simultaneously. In contrast with previous attempts to implement this method, we use an external magnetic field to align the magnetic polarization at the tip apex so as to optimize the interaction between tip and sample spins. This allows us to observe the direct magnetic exchange coupling between the spins of the tip atom and sample atom that are closest to each other, and thereby demonstrate the potential of magnetic exchange force microscopy for investigations of inter-spin interactions at the atomic level.

  5. Measuring the elasticity of plant cells with atomic force microscopy.

    PubMed

    Braybrook, Siobhan A

    2015-01-01

    The physical properties of biological materials impact their functions. This is most evident in plants where the cell wall contains each cell's contents and connects each cell to its neighbors irreversibly. Examining the physical properties of the plant cell wall is key to understanding how plant cells, tissues, and organs grow and gain the shapes important for their respective functions. Here, we present an atomic force microscopy-based nanoindentation method for examining the elasticity of plant cells at the subcellular, cellular, and tissue level. We describe the important areas of experimental design to be considered when planning and executing these types of experiments and provide example data as illustration. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Electronegativity determination of individual surface atoms by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Onoda, Jo; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Yoshiaki

    2017-04-01

    Electronegativity is a fundamental concept in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we find characteristic linear relations between the bond energies of different chemical species. We show that the linear relation can be rationalized by Pauling's equation for polar covalent bonds. This opens the possibility to characterize the electronegativity of individual surface atoms. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up ways of analysing surface chemical reactivity at the atomic scale.

  7. Electronegativity determination of individual surface atoms by atomic force microscopy

    PubMed Central

    Onoda, Jo; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Yoshiaki

    2017-01-01

    Electronegativity is a fundamental concept in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we find characteristic linear relations between the bond energies of different chemical species. We show that the linear relation can be rationalized by Pauling's equation for polar covalent bonds. This opens the possibility to characterize the electronegativity of individual surface atoms. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up ways of analysing surface chemical reactivity at the atomic scale. PMID:28443645

  8. Electronegativity determination of individual surface atoms by atomic force microscopy.

    PubMed

    Onoda, Jo; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Yoshiaki

    2017-04-26

    Electronegativity is a fundamental concept in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we find characteristic linear relations between the bond energies of different chemical species. We show that the linear relation can be rationalized by Pauling's equation for polar covalent bonds. This opens the possibility to characterize the electronegativity of individual surface atoms. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up ways of analysing surface chemical reactivity at the atomic scale.

  9. Electrostatic interaction in atomic force microscopy

    PubMed Central

    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 the Van der Waals force. The electrostatic force increases with increasing surface charge density and decreases roughly exponentially with distance. It can be reduced by imaging in high salt concentrations. Below surface potentials of ≈50 mV, a simple analytical approximation of the electrostatic force is described. PMID:19431803

  10. Phase imaging with intermodulation atomic force microscopy.

    PubMed

    Platz, Daniel; Tholén, Erik A; Hutter, Carsten; von Bieren, Arndt C; Haviland, David B

    2010-05-01

    Intermodulation atomic force microscopy (IMAFM) is a dynamic mode of atomic force microscopy (AFM) with two-tone excitation. The oscillating AFM cantilever in close proximity to a surface experiences the nonlinear tip-sample force which mixes the drive tones and generates new frequency components in the cantilever response known as intermodulation products (IMPs). We present a procedure for extracting the phase at each IMP and demonstrate phase images made by recording this phase while scanning. Amplitude and phase images at intermodulation frequencies exhibit enhanced topographic and material contrast.

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

    PubMed

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

    2014-05-27

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

  12. Fidelity imaging for atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Ghosal, Sayan; Salapaka, Murti

    2015-01-01

    Atomic force microscopy is widely employed for imaging material at the nanoscale. However, real-time measures on image reliability are lacking in contemporary atomic force microscopy literature. In this article, we present a real-time technique that provides an image of fidelity for a high bandwidth dynamic mode imaging scheme. The fidelity images define channels that allow the user to have additional authority over the choice of decision threshold that facilitates where the emphasis is desired, on discovering most true features on the sample with the possible detection of high number of false features, or emphasizing minimizing instances of false detections. Simulation and experimental results demonstrate the effectiveness of fidelity imaging.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Reconstructing the distributed force on an atomic force microscope cantilever

    NASA Astrophysics Data System (ADS)

    Wagner, Ryan; Killgore, Jason

    2017-03-01

    A methodology is developed to reconstruct the force applied to an atomic force microscopy (AFM) cantilever given the shape in which it vibrates. This is accomplished by rewriting Bernoulli-Euler beam theory such that the force on the cantilever is approximated as a linear superposition of the theoretical cantilever eigenmodes. The weighting factors in this summation are calculated from the amplitude and phase measured along the length of the cantilever. The accuracy of the force reconstruction is shown to depend on the frequency at which the measurement is performed, the number of discrete points measured along the length of the cantilever, and the signal-to-noise ratio of the measured signal. In contrast to other AFM force reconstruction techniques, this method can reconstruct the distribution of force applied over the length of the AFM cantilever. However, this method performs poorly for localized forces applied to the cantilever, such as is typical of most tip-sample interaction forces. Proof of concept experiments are performed on an electrostatically excited cantilever and the expected force distribution is recovered. This force reconstruction technique offers previously unavailable insight into the distributed forces experienced by an AFM cantilever.

  15. Reconstructing the distributed force on an atomic force microscope cantilever.

    PubMed

    Wagner, Ryan; Killgore, Jason

    2017-03-10

    A methodology is developed to reconstruct the force applied to an atomic force microscopy (AFM) cantilever given the shape in which it vibrates. This is accomplished by rewriting Bernoulli-Euler beam theory such that the force on the cantilever is approximated as a linear superposition of the theoretical cantilever eigenmodes. The weighting factors in this summation are calculated from the amplitude and phase measured along the length of the cantilever. The accuracy of the force reconstruction is shown to depend on the frequency at which the measurement is performed, the number of discrete points measured along the length of the cantilever, and the signal-to-noise ratio of the measured signal. In contrast to other AFM force reconstruction techniques, this method can reconstruct the distribution of force applied over the length of the AFM cantilever. However, this method performs poorly for localized forces applied to the cantilever, such as is typical of most tip-sample interaction forces. Proof of concept experiments are performed on an electrostatically excited cantilever and the expected force distribution is recovered. This force reconstruction technique offers previously unavailable insight into the distributed forces experienced by an AFM cantilever.

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

    PubMed

    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.

  17. Trapping atoms using nanoscale quantum vacuum forces

    PubMed Central

    Chang, D. E.; Sinha, K.; Taylor, J. M.; Kimble, H. J.

    2014-01-01

    Quantum vacuum forces dictate the interaction between individual atoms and dielectric surfaces at nanoscale distances. For example, their large strengths typically overwhelm externally applied forces, which makes it challenging to controllably interface cold atoms with nearby nanophotonic systems. Here we theoretically show that it is possible to tailor the vacuum forces themselves to provide strong trapping potentials. Our proposed trapping scheme takes advantage of the attractive ground-state potential and adiabatic dressing with an excited state whose potential is engineered to be resonantly enhanced and repulsive. This procedure yields a strong metastable trap, with the fraction of excited-state population scaling inversely with the quality factor of the resonance of the dielectric structure. We analyse realistic limitations to the trap lifetime and discuss possible applications that might emerge from the large trap depths and nanoscale confinement. PMID:25008119

  18. Trapping atoms using nanoscale quantum vacuum forces.

    PubMed

    Chang, D E; Sinha, K; Taylor, J M; Kimble, H J

    2014-07-10

    Quantum vacuum forces dictate the interaction between individual atoms and dielectric surfaces at nanoscale distances. For example, their large strengths typically overwhelm externally applied forces, which makes it challenging to controllably interface cold atoms with nearby nanophotonic systems. Here we theoretically show that it is possible to tailor the vacuum forces themselves to provide strong trapping potentials. Our proposed trapping scheme takes advantage of the attractive ground-state potential and adiabatic dressing with an excited state whose potential is engineered to be resonantly enhanced and repulsive. This procedure yields a strong metastable trap, with the fraction of excited-state population scaling inversely with the quality factor of the resonance of the dielectric structure. We analyse realistic limitations to the trap lifetime and discuss possible applications that might emerge from the large trap depths and nanoscale confinement.

  19. Automated force controller for amplitude modulation atomic force microscopy

    SciTech Connect

    Miyagi, Atsushi E-mail: simon.scheuring@inserm.fr; Scheuring, Simon E-mail: simon.scheuring@inserm.fr

    2016-05-15

    Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed.

  20. Calibration of frictional forces in atomic force microscopy

    SciTech Connect

    Ogletree, D.F.; Carpick, R.W.; Salmeron, M.

    1996-09-01

    The atomic force microscope can provide information on the atomic-level frictional properties of surfaces, but reproducible quantitative measurements are difficult to obtain. Parameters that are either unknown or difficult to precisely measure include the normal and lateral cantilever force constants (particularly with microfabricated cantilevers), the tip height, the deflection sensor response, and the tip structure and composition at the tip-surface contact. We present an {ital in} {ital situ} experimental procedure to determine the response of a cantilever to lateral forces in terms of its normal force response. This procedure is quite general. It will work with any type of deflection sensor and does not require the knowledge or direct measurement of the lever dimensions or the tip height. In addition, the shape of the tip apex can be determined. We also discuss a number of specific issues related to force and friction measurements using optical lever deflection sensing. We present experimental results on the lateral force response of commercially available V-shaped cantilevers. Our results are consistent with estimates of lever mechanical properties using continuum elasticity theory. {copyright} {ital 1996 American Institute of Physics.}

  1. High-resolution noncontact atomic force microscopy.

    PubMed

    Pérez, Rubén; García, Ricardo; Schwarz, Udo

    2009-07-01

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

  2. Neuron Biomechanics Probed by Atomic Force Microscopy

    PubMed Central

    Spedden, Elise; Staii, Cristian

    2013-01-01

    Mechanical interactions play a key role in many processes associated with neuronal growth and development. Over the last few years there has been significant progress in our understanding of the role played by the substrate stiffness in neuronal growth, of the cell-substrate adhesion forces, of the generation of traction forces during axonal elongation, and of the relationships between the neuron soma elastic properties and its health. The particular capabilities of the Atomic Force Microscope (AFM), such as high spatial resolution, high degree of control over the magnitude and orientation of the applied forces, minimal sample damage, and the ability to image and interact with cells in physiologically relevant conditions make this technique particularly suitable for measuring mechanical properties of living neuronal cells. This article reviews recent advances on using the AFM for studying neuronal biomechanics, provides an overview about the state-of-the-art measurements, and suggests directions for future applications. PMID:23921683

  3. Atomic force microscopy on liquid crystals

    NASA Astrophysics Data System (ADS)

    Bahr, Christian; Schulz, Benjamin

    This chapter provides an introduction to the atomic force microscopy (AFM) on thermotropic liquid crystals. We first give a general introduction to the technique of AFM and then describe the special requirements that have to be met for the imaging of liquid-crystalline surfaces. We also discuss the relation between the quality or reliability of the imaging results and various parameters of the scanning conditions. We briey review the existing work on AFM on liquid crystals and finally describe applications beyond the imaging, such as molecular force spectroscopy or manipulation of surface structures.

  4. Atomic Force Microscopy of Biological Membranes

    PubMed Central

    Frederix, Patrick L.T.M.; Bosshart, Patrick D.; Engel, Andreas

    2009-01-01

    Abstract Atomic force microscopy (AFM) is an ideal method to study the surface topography of biological membranes. It allows membranes that are adsorbed to flat solid supports to be raster-scanned in physiological solutions with an atomically sharp tip. Therefore, AFM is capable of observing biological molecular machines at work. In addition, the tip can be tethered to the end of a single membrane protein, and forces acting on the tip upon its retraction indicate barriers that occur during the process of protein unfolding. Here we discuss the fundamental limitations of AFM determined by the properties of cantilevers, present aspects of sample preparation, and review results achieved on reconstituted and native biological membranes. PMID:19167286

  5. Spectroscopy and atomic force microscopy of biomass.

    PubMed

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

    2010-05-01

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

  6. Imaging DNA Structure by Atomic Force Microscopy.

    PubMed

    Pyne, Alice L B; Hoogenboom, Bart W

    2016-01-01

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

  7. Atomic Force Microscope for Imaging and Spectroscopy

    NASA Technical Reports Server (NTRS)

    Pike, W. T.; Hecht, M. H.; Anderson, M. S.; Akiyama, T.; Gautsch, S.; deRooij, N. F.; Staufer, U.; Niedermann, Ph.; Howald, L.; Mueller, D.

    2000-01-01

    We have developed, built, and tested an atomic force microscope (AFM) for extraterrestrial applications incorporating a micromachined tip array to allow for probe replacement. It is part of a microscopy station originally intended for NASA's 2001 Mars lander to identify the size, distribution, and shape of Martian dust and soil particles. As well as imaging topographically down to nanometer resolution, this instrument can be used to reveal chemical information and perform infrared and Raman spectroscopy at unprecedented resolution.

  8. Atomic Force Microscope for Imaging and Spectroscopy

    NASA Technical Reports Server (NTRS)

    Pike, W. T.; Hecht, M. H.; Anderson, M. S.; Akiyama, T.; Gautsch, S.; deRooij, N. F.; Staufer, U.; Niedermann, Ph.; Howald, L.; Mueller, D.

    2000-01-01

    We have developed, built, and tested an atomic force microscope (AFM) for extraterrestrial applications incorporating a micromachined tip array to allow for probe replacement. It is part of a microscopy station originally intended for NASA's 2001 Mars lander to identify the size, distribution, and shape of Martian dust and soil particles. As well as imaging topographically down to nanometer resolution, this instrument can be used to reveal chemical information and perform infrared and Raman spectroscopy at unprecedented resolution.

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

    PubMed

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

    2014-10-01

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

  10. First Atomic Force Microscope Image from Mars

    NASA Technical Reports Server (NTRS)

    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.

  11. First Atomic Force Microscope Image from Mars

    NASA Technical Reports Server (NTRS)

    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.

  12. Periodicity in bimodal atomic force microscopy

    SciTech Connect

    Lai, Chia-Yun; Santos, Sergio Chiesa, Matteo; Barcons, Victor

    2015-07-28

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

  13. Friction forces on atoms after acceleration

    SciTech Connect

    Intravaia, Francesco; Mkrtchian, Vanik E.; Buhmann, Stefan Yoshi; Scheel, Stefan; Dalvit, Diego A. R.; Henkel, Carsten

    2015-05-12

    The aim of this study 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.

  14. Friction forces on atoms after acceleration

    DOE PAGES

    Intravaia, Francesco; Mkrtchian, Vanik E.; Buhmann, Stefan Yoshi; ...

    2015-05-12

    The aim of this study 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 contributionmore » 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.« less

  15. Ultrastable Atomic Force Microscopy for Biophysics

    NASA Astrophysics Data System (ADS)

    Churnside, Allison B.

    Atomic force microscopy (AFM) is a multifunctional workhorse of nanoscience and molecular biophysics, but instrumental drift remains a critical issue that limits the precision and duration of experiments. We have significantly reduced the two most important types of drift: in position and in force. The first, position drift, is defined as uncontrolled motion between the tip and the sample, which occurs in all three dimensions. By scattering a laser off the apex of a commercial AFM tip, we locally measured and thereby actively controlled its three-dimensional position above a sample surface to <0.4 A (Deltaf = 0.01--10 Hz) in air at room temperature. With this enhanced stability, we demonstrated atomic-scale (˜1 A) tip-sample stability and registration over tens of minutes with a series of AFM images. The second type of drift is force drift. We found that the primary source of force drift for a popular class of soft cantilevers is their gold coating, even though they are coated on both sides to minimize drift. When the gold coating was removed through a simple chemical etch, this drift in deflection was reduced by more than an order of magnitude over the first 2 hours after wetting the tip. Removing the gold also led to ˜ 10-fold reduction in reflected light, yet short-term (0.1--10 s) force precision improved. With both position and force drift greatly reduced, the utility of the AFM is enhanced. These improvements led to several new AFM abilities, including a five-fold increase in the image signal-to-noise ratio; tip-registered, label-free optical imaging; registered tip return to a particular point on the sample; and dual-detection force spectroscopy, which enables a new extension clamp mode. We have applied these abilities to folding of both membrane and soluble proteins. In principle, the techniques we describe can be fully incorporated into many types of scanning probe microscopy, making this work a general improvement to scanning probe techniques.

  16. Technique to measure contact angle of micro/nanodroplets using atomic force microscopy

    SciTech Connect

    Jung, Yong Chae; Bhushan, Bharat

    2008-07-15

    Contact angle is the primary parameter that characterizes wetting; however, the measurement techniques have been limited to droplets with a diameter as low as about 50 {mu}m. The authors developed an atomic force microscopy-based technique to measure the contact angle of micro- and nanodroplets deposited using a modified nanoscale dispensing tip. The obtained contact angle results were compared with those of a macrodroplet (2.1 mm diameter). It was found that the contact angle on various surfaces decreases with decreasing the droplet size.

  17. Microfluidics, Chromatography, and Atomic-Force Microscopy

    NASA Technical Reports Server (NTRS)

    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.

  18. Applications of Atomic Resolution Atomic Force Microscopy to Nanoscience & Nanotechnology

    NASA Astrophysics Data System (ADS)

    Rhodin, Thor

    2001-03-01

    New developments in nanophysical scanning probe microscopy in terms of its unique relatonship to nanoscience, together with specific applications to nanoelectronic and biotechnology, will be discussed(1).Innovative examples of chemical physics at interfaces are analyzed where state-of-the-art non contact atomic force microscopy(nc-AFM) measurement of a specific physical or chemical property is correlated with position, orientation and/or location with atomic resolution. Analysis of specific current as well as future applications of nc-AFM to the detection, manipulation and fabrication of nanostructures on the molecular scale will be presented.Design features of nano-instrumentation based on carbon nanotube technology, high frequency solid state micro-oscillators and variable temperature applications will be presented.Specific examples pertaining to, (1) chemical bonding interaction on a semiconductor,(2) surface structure of an ionic insulator,(3) structural features in a biological interface and (4) nanofabrication of a quantum electron device, will be reviewed in terms of their innovativeness and significance to nanoscience and nanotechnology. 1 ``Scanning Probe Microscopies,Nanoscience & Nanotechnology" T.N. Rhodin, Proceedings of nc-AFM Workshop, July 2000, Hamburg, Germany. Springer Verlag U. Schwarz, H. Hoelscher and M. Wiesendanger, guest editors.

  19. Exploring atomic-scale lateral forces in the attractive regime: a case study on graphite (0001).

    PubMed

    Baykara, Mehmet Z; Schwendemann, Todd C; Albers, Boris J; Pilet, Nicolas; Mönig, Harry; Altman, Eric I; Schwarz, Udo D

    2012-10-12

    A non-contact atomic force microscopy-based method has been used to map the static lateral forces exerted on an atomically sharp Pt/Ir probe tip by a graphite surface. With measurements carried out at low temperatures and in the attractive regime, where the atomic sharpness of the tip can be maintained over extended time periods, the method allows the quantification and directional analysis of lateral forces with piconewton and picometer resolution as a function of both the in-plane tip position and the vertical tip-sample distance, without limitations due to a finite contact area or to stick-slip-related sudden jumps of tip apex atoms. After reviewing the measurement principle, the data obtained in this case study are utilized to illustrate the unique insight that the method offers. In particular, the local lateral forces that are expected to determine frictional resistance in the attractive regime are found to depend linearly on the normal force for small tip-sample distances.

  20. Investigating cell mechanics with atomic force microscopy

    PubMed Central

    Haase, Kristina; Pelling, Andrew E.

    2015-01-01

    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

  1. Atomic force microscopy of biological samples.

    PubMed

    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). © 2010 John Wiley & Sons, Inc.

  2. Investigating cell mechanics with atomic force microscopy.

    PubMed

    Haase, Kristina; Pelling, Andrew E

    2015-03-06

    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.

  3. Atomic force microscopy of biological samples

    SciTech Connect

    Doktycz, Mitchel John

    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).

  4. Atomic Force Microscopy for Soil Analysis

    NASA Astrophysics Data System (ADS)

    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.

  5. Atomic Force Microscopy: Theory and Experiment

    NASA Astrophysics Data System (ADS)

    Gould, Scot A. C.

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

  6. Atomic force microscopy of Precambrian microscopic fossils

    PubMed Central

    Kempe, André; Schopf, J. William; Altermann, Wladyslaw; Kudryavtsev, Anatoliy B.; Heckl, Wolfgang M.

    2002-01-01

    Atomic force microscopy (AFM) is a technique used routinely in material science to image substances at a submicron (including nm) scale. We apply this technique to analysis of the fine structure of organic-walled Precambrian fossils, microscopic sphaeromorph acritarchs (cysts of planktonic unicellular protists) permineralized in ≈650-million-year-old cherts of the Chichkan Formation of southern Kazakhstan. AFM images, backed by laser-Raman spectroscopic analysis of individual specimens, demonstrate that the walls of these petrified fossils are composed of stacked arrays of ≈200-nm-sized angular platelets of polycyclic aromatic kerogen. Together, AFM and laser-Raman spectroscopy provide means by which to elucidate the submicron-scale structure of individual microscopic fossils, investigate the geochemical maturation of ancient organic matter, and, potentially, distinguish true fossils from pseudofossils and probe the mechanisms of fossil preservation by silica permineralization. PMID:12089337

  7. High-frequency multimodal atomic force microscopy

    PubMed Central

    Nievergelt, Adrian P; Adams, Jonathan D; Odermatt, Pascal D

    2014-01-01

    Summary 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. PMID:25671141

  8. Measuring molecular weight by atomic force microscopy.

    PubMed

    Sheiko, Sergei S; da Silva, Marcelo; Shirvaniants, David; LaRue, Isaac; Prokhorova, Svetlana; Moeller, Martin; Beers, Kathryn; Matyjaszewski, Krzysztof

    2003-06-04

    Absolute-molecular-weight distribution of cylindrical brush molecules were determined using a combination of the Langmuir Blodget (LB) technique and Atomic Force Microscopy (AFM). The LB technique gives mass density of a monolayer, i.e., mass per unit area, whereas visualization of individual molecules by AFM enables accurate measurements of the molecular density, i.e., number of molecules per unit area. From the ratio of the mass density to the molecular density, one can determine the absolute value for the number average molecular weight. Assuming that the structure of brush molecules is uniform along the backbone, the length distribution should be virtually identical to the molecular weight distribution. Although we used only brush molecules for demonstration purpose, this approach can be applied for a large variety of molecular and colloidal species that can be visualized by a microscopic technique.

  9. Atomic force microscopy of model lipid membranes.

    PubMed

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

    2013-02-01

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

  10. Atomic force microscopy of Precambrian microscopic fossils.

    PubMed

    Kempe, André; Schopf, J William; Altermann, Wladyslaw; Kudryavtsev, Anatoliy B; Heckl, Wolfgang M

    2002-07-09

    Atomic force microscopy (AFM) is a technique used routinely in material science to image substances at a submicron (including nm) scale. We apply this technique to analysis of the fine structure of organic-walled Precambrian fossils, microscopic sphaeromorph acritarchs (cysts of planktonic unicellular protists) permineralized in approximately 650-million-year-old cherts of the Chichkan Formation of southern Kazakhstan. AFM images, backed by laser-Raman spectroscopic analysis of individual specimens, demonstrate that the walls of these petrified fossils are composed of stacked arrays of approximately 200-nm-sized angular platelets of polycyclic aromatic kerogen. Together, AFM and laser-Raman spectroscopy provide means by which to elucidate the submicron-scale structure of individual microscopic fossils, investigate the geochemical maturation of ancient organic matter, and, potentially, distinguish true fossils from pseudofossils and probe the mechanisms of fossil preservation by silica permineralization.

  11. Atomic force microscopy of biochemically tagged DNA.

    PubMed Central

    Murray, M N; Hansma, H G; Bezanilla, M; Sano, T; Ogletree, D F; Kolbe, W; Smith, C L; Cantor, C R; Spengler, S; Hansma, P K

    1993-01-01

    Small fragments of DNA of known length were made with the polymerase chain reaction. These fragments had biotin molecules covalently attached at their ends. They were subsequently labeled with a chimeric protein fusion between streptavidin and two immunoglobulin G-binding domains of staphylococcal protein A. This tetrameric species was expected to bind up to four DNA molecules via their attached biotin moieties. The DNA-protein complex was deposited on mica and imaged with an atomic force microscope. The images revealed the protein chimera at the expected location at the ends of the strands of DNA as well as the expected dimers, trimers, and tetramers of DNA bound to a single protein. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8483898

  12. Atomic Force Microscopy for DNA SNP Identification

    NASA Astrophysics Data System (ADS)

    Valbusa, Ugo; Ierardi, Vincenzo

    The knowledge of the effects of single-nucleotide polymorphisms (SNPs) in the human genome greatly contributes to better comprehension of the relation between genetic factors and diseases. Sequence analysis of genomic DNA in different individuals reveals positions where variations that involve individual base substitutions can occur. Single-nucleotide polymorphisms are highly abundant and can have different consequences at phenotypic level. Several attempts were made to apply atomic force microscopy (AFM) to detect and map SNP sites in DNA strands. The most promising approach is the study of DNA mutations producing heteroduplex DNA strands and identifying the mismatches by means of a protein that labels the mismatches. MutS is a protein that is part of a well-known complex of mismatch repair, which initiates the process of repairing when the MutS binds to the mismatched DNA filament. The position of MutS on the DNA filament can be easily recorded by means of AFM imaging.

  13. Lewy bodies under atomic force microscope.

    PubMed

    Tercjak, Agnieszka; Bergareche, Alberto; Caballero, Cristina; Tuñon, Teresa; Linazasoro, Gurutz

    2014-02-01

    Lewy bodies are the hallmark of Parkinson disease and their sophisticated analysis will undoubtedly elucidate the pathogenic process. They have been studied by using different microscopic tools. The authors have used atomic force microscopy (AFM) to study the ultramicrotom cut postmortem brain tissue of Parkinson disease patients. Under the same preparation conditions, they have found aggregated fibrillary nanostructures in Lewy bodies, as well as a loss of connections between neurons located in other parts of the substantia nigra. Although these results are preliminary and descriptive in nature, this paper reports the application of a novel and intriguing technique. Further studies including the study of cortical LB and Lewy neurites will be needed to determine the full potential of AFM in the study of the pathogenesis of cell death in Parkinson disease and other synucleinopathies.

  14. Ab Initio Based 2D Continuum Mechanics - Sensitivity Prediction for Contact Resonance Atomic Force Microscopy Based Structure Fingerprints

    NASA Astrophysics Data System (ADS)

    Tu, Qing; Lange, Björn; Lopes, J. Marcelo J.; Zauscher, Stefan; Blum, Volker

    Contact resonance AFM is demonstrated as a powerful tool for mapping differences in the mechanical properties of 2D materials and heterostructures, permitting to resolve surface and subsurface structural differences of different domains. Measured contact resonance frequencies are related to the contact stiffness of the combined tip-sample system. Based on first principles predicted elastic properties and a continuum approach to model the mechanical impedance, we find contact stiffness ratios between different domains of few-layer graphene on 3C-SiC(111) in excellent agreement with experiment. We next demonstrate that the approach is able to quantitatively resolve differences between other 2D materials domains, e.g., for h-BN, MoS2 and MoO3 on graphene on SiC. We show that the combined effect of several materials parameters, especially the in-plane elastic properties and the layer thickness, determines the contact stiffness, therefore boosting the sensitivity even if the out-of-plane elastic properties are similar.

  15. Intermodulation Atomic Force Microscopy and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hutter, Carsten; Platz, Daniel; Tholen, Erik; Haviland, David; Hansson, Hans

    2009-03-01

    We present a powerful new method of dynamic AFM, which allows to gain far more information about the tip-surface interaction than standard amplitude or phase imaging, while scanning at comparable speed. Our method, called intermodulation atomic force microscopy (ImAFM), employs the manifestly nonlinear phenomenon of intermodulation to extract information about tip-surface forces. ImAFM uses one eigenmode of a mechanical resonator, the latter driven at two frequencies to produce many spectral peaks near its resonace, where sensitivity is highest [1]. We furthermore present a protocol for decoding the combined information encoded in the spectrum of intermodulation peaks. Our theoretical framework suggests methods to enhance the gained information by using a different parameter regime as compared to Ref. [1]. We also discuss strategies for solving the inverse problem, i.e., for extracting the nonlinear tip-surface interaction from the response, also naming limitations of our theoretical analysis. We will further report on latest progress to experimentally employ our new protocol.[3pt] [1] D. Platz, E. A. Tholen, D. Pesen, and D. B. Haviland, Appl. Phys. Lett. 92, 153106 (2008).

  16. EDITORIAL: High-resolution noncontact atomic force microscopy High-resolution noncontact atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Pérez, Rubén; García, Ricardo; Schwarz, Udo

    2009-06-01

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

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

    PubMed

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

    2011-02-01

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

  18. Measuring and Understanding Forces on Atomic Length Scales with the Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Cleveland, Jason Paul

    Most microscopes can be used with little understanding of how they work--much can be learned looking through a light microscope without ever knowing what a photon is or who Maxwell was--and the Atomic Force Microscope (AFM) is no exception. Many AFM images don't look much different from a mountainous landscape, and much is learned interpreting them as such; however, to really push a microscope to its limits means understanding the interactions creating the contrast in the picture. For a Scanning Electron Microscope, this means understanding how electrons interact with matter, for an AFM it means understanding forces. The focus of this thesis is understanding the forces acting (especially in liquids) between tip and sample in AFM and a better understanding the instrument itself. Chapters I, II and VI involve better characterizing and improving the most important part of the AFM, the tiny cantilever used to measure forces. Chapter I describes a solution to one of the most basic problems that must be solved before forces can be accurately measured--measuring the stiffness of these cantilevers. Many limitations in AFM are set by physical characteristics of the cantilever itself, such as resonance frequency, spring constant, and quality factor. If an external force can be applied to the cantilever, feedback can be used to improve these characteristics. Chapter II shows how to do this using a magnetically applied external force, which has the advantage of working in liquids. These physical characteristics also change drastically when the cantilever is immersed in fluid. The resonance frequency of common cantilevers drops by as much as a factor of six in going from air to water. Chapter VI studies these changes and shows how further miniaturization of cantilevers can improve imaging speeds and signal-to-noise ratio. Early in its career, the AFM was heralded as having atomic resolution, but as the field matured researchers realized that the contact area between tip and

  19. Atomic Force Microscopy on Its Way to Adolescence

    NASA Astrophysics Data System (ADS)

    Giessibl, Franz J.

    2003-12-01

    When the atomic force microscope (AFM) was introduced in 1986, its potential to resolve surfaces with true atomic resolution was already proposed. However, substantial problems had to be overcome before atomic resolution became possible by AFM. Today, true atomic resolution by AFM is standard practice. This article discusses the influence of the cantilever stiffness and — amplitude on noise and short-range force sensitivity and introduces a sensor operating at near optimal conditions (qPlus sensor). The data achieved with this optimized sensing technology show substructures within single atom images, attributed to atomic orbitals.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  1. Atomic force microscopy of virus shells.

    PubMed

    Moreno-Madrid, Francisco; Martín-González, Natalia; Llauró, Aida; Ortega-Esteban, Alvaro; Hernando-Pérez, Mercedes; Douglas, Trevor; Schaap, Iwan A T; de Pablo, Pedro J

    2017-04-15

    Microscopes are used to characterize small objects with the help of probes that interact with the specimen, such as photons and electrons in optical and electron microscopies, respectively. In atomic force microscopy (AFM), the probe is a nanometric tip located at the end of a microcantilever which palpates the specimen under study just as a blind person manages a walking stick. In this way, AFM allows obtaining nanometric resolution images of individual protein shells, such as viruses, in a liquid milieu. Beyond imaging, AFM also enables not only the manipulation of single protein cages, but also the characterization of every physicochemical property capable of inducing any measurable mechanical perturbation to the microcantilever that holds the tip. In the present revision, we start revising some recipes for adsorbing protein shells on surfaces. Then, we describe several AFM approaches to study individual protein cages, ranging from imaging to spectroscopic methodologies devoted to extracting physical information, such as mechanical and electrostatic properties. We also explain how a convenient combination of AFM and fluorescence methodologies entails monitoring genome release from individual viral shells during mechanical unpacking.

  2. Atomic force microscopy investigation of viruses.

    PubMed

    McPherson, Alexander; Kuznetsov, Yurii G

    2011-01-01

    Atomic force microscopy (AFM) has proven to be a valuable approach to delineate the architectures and detailed structural features of a wide variety of viruses. These have ranged from small plant satellite viruses of only 17 nm to the giant mimivirus of 750 nm diameter, and they have included diverse morphologies such as those represented by HIV, icosahedral particles, vaccinia, and bacteriophages. Because it is a surface technique, it provides images and information that are distinct from those obtained by electron microscopy, and in some cases, at even higher resolution. By enzymatic and chemical dissection of virions, internal structures can be revealed, as well as DNA and RNA. The method is relatively rapid and can be carried out on both fixed and unfixed samples in either air or fluids, including culture media. It is nondestructive and even non-perturbing. It can be applied to individual isolated virus, as well as to infected cells. AFM is still in its early development and holds great promise for further investigation of biological systems at the nanometer scale.

  3. Sharp Tips on the Atomic Force Microscope

    NASA Technical Reports Server (NTRS)

    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.

  4. Atomic force microscopy study of enamel remineralization.

    PubMed

    Poggio, Claudio; Ceci, Matteo; Beltrami, Riccardo; Lombardini, Marco; Colombo, Marco

    2014-07-01

    The aim of the present in vitro study was the evaluation of two products: a CPP-ACP paste (GC Tooth Mousse, GC Corp.) and a desensitizing toothpaste (Colgate Sensitive Pro Relief, Colgate-Palmolive) on preventing enamel erosion produced by a soft drink (Coca Cola) by using Atomic Force Microscopy (AFM). Thirty enamel specimens were assigned to 6 groups of 5 specimens each. 1: intact enamel, 2: enamel + soft drink, 3: intact enamel + Colgate Sensitive Pro Relief, 4: enamel + soft drink + Colgate Sensitive Pro Relief, 5: intact enamel + GC Tooth Mousse, 6: enamel + soft drink + GC Tooth Mousse. The surface of each specimen was imaged by AFM. The root mean-square roughness (Rrms) was obtained from the AFM images and the differences in the averaged values among the groups were analyzed by ANOVA test. Comparing groups 4 and 6 (soft drink + toothpastes) with group 2 (eroded enamel) a statistical difference (P<0.05) was registered, suggesting effectiveness in protecting enamel against erosion of the products investigated. The use of new formulation toothpastes can prevent enamel demineralization.

  5. Atomic force microscopy study of enamel remineralization

    PubMed Central

    Poggio, Claudio; Ceci, Matteo; Beltrami, Riccardo; Lombardini, Marco; Colombo, Marco

    2014-01-01

    Summary Aim The aim of the present in vitro study was the evaluation of two products: a CPP-ACP paste (GC Tooth Mousse, GC Corp.) and a desensitizing toothpaste (Colgate Sensitive Pro Relief, Colgate-Palmolive) on preventing enamel erosion produced by a soft drink (Coca Cola) by using Atomic Force Microscopy (AFM). Methods Thirty enamel specimens were assigned to 6 groups of 5 specimens each. 1: intact enamel, 2: enamel + soft drink, 3: intact enamel + Colgate Sensitive Pro Relief, 4: enamel + soft drink + Colgate Sensitive Pro Relief, 5: intact enamel + GC Tooth Mousse, 6: enamel + soft drink + GC Tooth Mousse. The surface of each specimen was imaged by AFM. The root mean-square roughness (Rrms) was obtained from the AFM images and the differences in the averaged values among the groups were analyzed by ANOVA test. Results Comparing groups 4 and 6 (soft drink + toothpastes) with group 2 (eroded enamel) a statistical difference (P<0.05) was registered, suggesting effectiveness in protecting enamel against erosion of the products investigated. Conclusions The use of new formulation toothpastes can prevent enamel demineralization. PMID:25506414

  6. Sharp Tips on the Atomic Force Microscope

    NASA Technical Reports Server (NTRS)

    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. Investigating bioconjugation by atomic force microscopy

    PubMed Central

    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

  8. Dispersion forces between ultracold atoms and a carbon nanotube.

    PubMed

    Schneeweiss, P; Gierling, M; Visanescu, G; Kern, D P; Judd, T E; Günther, A; Fortágh, J

    2012-08-01

    Dispersion forces are long-range interactions between polarizable objects that arise from fluctuations in the electromagnetic field between them. Dispersion forces have been observed between microscopic objects such as atoms and molecules (the van der Waals interaction), between macroscopic objects (the Casimir interaction) and between an atom and a macroscopic object (the Casimir-Polder interaction). Dispersion forces are known to increase the attractive forces between the components in nanomechanical devices, to influence adsorption rates onto nanostructures, and to influence the interactions between biomolecules in biological systems. In recent years, there has been growing interest in studying dispersion forces in nanoscale systems and in exploring the interactions between carbon nanotubes and cold atoms. However, there are considerable difficulties in developing dispersion force theories for general, finite geometries such as nanostructures. Thus, there is a need for new experimental methods that are able to go beyond measurements of planar surfaces and nanoscale gratings and make measurements on isolated nanostructures. Here, we measure the dispersion force between a rubidium atom and a multiwalled carbon nanotube by inserting the nanotube into a cloud of ultracold rubidium atoms and monitoring the loss of atoms from the cloud as a function of time. We perform these experiments with both thermal clouds of ultracold atoms and with Bose-Einstein condensates. The results obtained with this approach will aid the development of theories describing quantum fields near nanostructures, and hybrid cold-atom/solid-state devices may also prove useful for applications in quantum sensing and quantum information.

  9. Atomic force microscopy study of tooth surfaces.

    PubMed

    Farina, M; Schemmel, A; Weissmüller, G; Cruz, R; Kachar, B; Bisch, P M

    1999-03-01

    Atomic force microscopy (AFM) was used to study tooth surfaces in order to compare the pattern of particle distribution in the outermost layer of the tooth surfaces. Human teeth and teeth from a rodent (Golden hamster), from a fish (piranha), and from a grazing mollusk (chiton) with distinct feeding habits were analyzed in terms of particle arrangement, packing, and size distribution. Scanning electron microscopy and transmission electron microscopy were used for comparison. It was found that AFM gives high-contrast, high-resolution images and is an important tool as a source of complementary and/or new structural information. All teeth were cleaned and some were etched with acidic solutions before analysis. It was observed that human enamel (permanent teeth) presents particles tightly packed in the outer surface, whereas enamel from the hamster (continuously growing teeth) shows particles of less dense packing. The piranha teeth have a thin cuticle covering the long apatite crystals of the underlying enameloid. This cuticle has a rough surface of particles that have a globular appearance after the brief acidic treatment. The similar appearance of the in vivo naturally etched tooth surface suggests that the pattern of globule distribution may be due to the presence of an organic material. Elemental analysis of this cuticle indicated that calcium, phosphorus, and iron are the main components of the structure while electron microdiffraction of pulverized cuticle particles showed a pattern consistent with hydroxyapatite. The chiton mineralized tooth cusp had a smooth surface in an unabraded region and a very rough structure with the magnetite crystals (already known to make part of the structure) protruding from the surface. It was concluded that the structures analyzed are optimized for efficiency in feeding mechanism and life span of the teeth.

  10. Advanced atomic force microscopy: Development and application

    NASA Astrophysics Data System (ADS)

    Walters, Deron A.

    Over the decade since atomic force microscopy (AFM) was invented, development of new microscopes has been closely intertwined with application of AFM to problems of interest in physics, chemistry, biology, and engineering. New techniques such as tapping mode AFM move quickly in our lab from the designer's bench to the user's table-since this is often the same piece of furniture. In return, designers get ample feedback as to what problems are limiting current instruments, and thus need most urgent attention. Tip sharpness and characterization are such a problem. Chapter 1 describes an AFM designed to operate in a scanning electron microscope, whose electron beam is used to deposit sharp carbonaceous tips. These tips can be tested and used in situ. Another limitation is addressed in Chapter 2: the difficulty of extracting more than just topographic information from a sample. A combined AFM/confocal optical microscope was built to provide simultaneous, independent images of the topography and fluorescence of a sample. In combination with staining or antibody labelling, this could provide submicron information about the composition of a sample. Chapters 3 and 4 discuss two generations of small cantilevers developed for lower-noise, higher-speed AFM of biological samples. In Chapter 4, a 26 mum cantilever is used to image the process of calcite growth from solution at a rate of 1.6 sec/frame. Finally, Chapter 5 explores in detail a biophysics problem that motivates us to develop fast, quiet, and gentle microscopes; namely, the control of crystal growth in seashells by the action of soluble proteins on a growing calcite surface.

  11. Velocity-dependent dipole forces on an excited atom

    NASA Astrophysics Data System (ADS)

    Donaire, M.; Lambrecht, A.

    2016-02-01

    We present a time-dependent calculation of the velocity-dependent forces which act on an excited atomic dipole in relative motion with respect to ground state atoms of a different kind. Both its interaction with a single atom and with a dilute atomic plate are evaluated. In either case, the total force consists of a conservative van der Waals component and a nonconservative Röntgen component. On physical grounds, the former corresponds to the velocity-dependent recoil experienced by the excited atom in the processes of absorption and emission of the photons that it exchanges with the ground-state atoms on a periodic basis. The latter corresponds to the time-variation of the Röntgen momentum, which is also mediated by the periodic exchange of quasiresonant photons. We find that, at leading order, all these interactions are linear in velocity. In the nonretarded regime the van der Waals force dominates, being antiparallel to the velocity. On the contrary, in the retarded regime the velocity-dependent forces oscillate in space, van der Waals and Röntgen forces are of the same order in the atom-atom interaction, and the Röntgen component dominates in the atom-surface interaction.

  12. Surface Biology of DNA by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Hansma, Helen G.

    2001-10-01

    The atomic force microscope operates on surfaces. Since surfaces occupy much of the space in living organisms, surface biology is a valid and valuable form of biology that has been difficult to investigate in the past owing to a lack of good technology. Atomic force microscopy (AFM) of DNA has been used to investigate DNA condensation for gene therapy, DNA mapping and sizing, and a few applications to cancer research and to nanotechnology. Some of the most exciting new applications for atomic force microscopy of DNA involve pulling on single DNA molecules to obtain measurements of single-molecule mechanics and thermodynamics.

  13. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

    PubMed Central

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

  14. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy.

    PubMed

    Neuman, Keir C; Nagy, Attila

    2008-06-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

  15. Optical force on atoms with periodic adiabatic rapid passage sequences

    NASA Astrophysics Data System (ADS)

    Miao, Xiyue

    Adiabatic Rapid Passage (ARP) is a long-existing method to invert the population of a two-level nuclear spin system. Its extension to the optical domain necessitates a frequency chirped light pulse to interact with a two-level atom through dipole interaction. In this dissertation ARP processes for various pulse schemes and pulse parameters have been studied theoretically and experimentally. The non-adiabatic transition probability of ARP was quantified to characterize the efficiency of ARP for population transfer. Unanticipated regularities were found in the pulse parameter space. ARP sequences in periodic phase coherent counter-propagating light pulses can be used to produce large optical forces on atoms. The magnitude of the force is proportional to the pulse repetition rate. So the force can be much larger than the usual radiative force if the pulse repetition rate is much higher than the spontaneous emission rate. The behavior of the atoms in such periodic ARP fields without spontaneous emission is well described by a periodic Hamiltonian. By investigating the evolution of the Bloch vector on the Bloch sphere, we related the average optical force on atoms to the non-adiabatic transition probability of a single pulse. Syncopation time has to be introduced in the pulsing scheme to produce a directional force in the presence of spontaneous emission. Experimentally, we observed the force on He* atoms by the deflection of the atomic beam with periodic chirped pulses from counter-propagating pulse trains. The chirped pulse train was realized by synchronized phase and amplitude modulation of the light from a cw diode laser. The Fourier spectrum of the modulated light was monitored to guarantee the quality of the chirped pulses. The measured ARP forces are about half of the theoretical predictions. Not only have we shown that such forces are huge and robust, but we have also been able to map the forces in the two dimensional pulse parameter space. The force

  16. The role of nonlinear dynamics in quantitative atomic force microscopy.

    PubMed

    Platz, Daniel; Forchheimer, Daniel; Tholén, Erik A; Haviland, David B

    2012-07-05

    Various methods of force measurement with the atomic force microscope are compared for their ability to accurately determine the tip-surface force from analysis of the nonlinear cantilever motion. It is explained how intermodulation, or the frequency mixing of multiple drive tones by the nonlinear tip-surface force, can be used to concentrate the nonlinear motion in a narrow band of frequency near the cantilever's fundamental resonance, where accuracy and sensitivity of force measurement are greatest. Two different methods for reconstructing tip-surface forces from intermodulation spectra are explained. The reconstruction of both conservative and dissipative tip-surface interactions from intermodulation spectra are demonstrated on simulated data.

  17. [Atomic force microscopy fishing of gp120 on immobilized aptamer and its mass spectrometry identification].

    PubMed

    Bukharina, N S; Ivanov, Yu D; Pleshakova, T O; Frantsuzov, P A; Andreeva, E Yu; Kaysheva, A L; Izotov, A A; Pavlova, T I; Ziborov, V S; Radko, S P; Archakov, A I

    2015-01-01

    A method of atomic force microscopy-based fishing (AFM fishing) has been developed for protein detection in the analyte solution using a chip with an immobilized aptamer. This method is based on the biospecific fishing of a target protein from a bulk solution onto the small AFM chip area with the immobilized aptamer to this protein used as the molecular probe. Such aptamer-based approach allows to increase an AFM image contrast compared to the antibody-based approach. Mass spectrometry analysis used after the biospecific fishing to identify the target protein on the AFM chip has proved complex formation. Use of the AFM chip with the immobilized aptamer avoids interference of the antibody and target protein peaks in a mass spectrum.

  18. CO Tip Functionalization Inverts Atomic Force Microscopy Contrast via Short-Range Electrostatic Forces

    NASA Astrophysics Data System (ADS)

    Schneiderbauer, Maximilian; Emmrich, Matthias; Weymouth, Alfred J.; Giessibl, Franz J.

    2014-04-01

    We investigate insulating Cu2N islands grown on Cu(100) by means of combined scanning tunneling microscopy and atomic force microscopy with two vastly different tips: a bare metal tip and a CO-terminated tip. We use scanning tunneling microscopy data as proposed by Choi, Ruggiero, and Gupta to unambiguously identify atomic positions. Atomic force microscopy images taken with the two different tips show an inverted contrast over Cu2N. The observed force contrast can be explained with an electrostatic model, where the two tips have dipole moments of opposite directions. This highlights the importance of short-range electrostatic forces in the formation of atomic contrast on polar surfaces in noncontact atomic force microscopy.

  19. CO tip functionalization inverts atomic force microscopy contrast via short-range electrostatic forces.

    PubMed

    Schneiderbauer, Maximilian; Emmrich, Matthias; Weymouth, Alfred J; Giessibl, Franz J

    2014-04-25

    We investigate insulating Cu2N islands grown on Cu(100) by means of combined scanning tunneling microscopy and atomic force microscopy with two vastly different tips: a bare metal tip and a CO-terminated tip. We use scanning tunneling microscopy data as proposed by Choi, Ruggiero, and Gupta to unambiguously identify atomic positions. Atomic force microscopy images taken with the two different tips show an inverted contrast over Cu2N. The observed force contrast can be explained with an electrostatic model, where the two tips have dipole moments of opposite directions. This highlights the importance of short-range electrostatic forces in the formation of atomic contrast on polar surfaces in noncontact atomic force microscopy.

  20. Controlled manipulation of atoms in insulating surfaces with the virtual atomic force microscope.

    PubMed

    Trevethan, T; Watkins, M; Kantorovich, L N; Shluger, A L

    2007-01-12

    We predict how single oxygen ions can be manipulated on the MgO (100) surface and demonstrate the possibility of detecting a single-atom event using a noncontact atomic force microscope. The manipulation process is simulated explicitly in real time with a virtual dynamic atomic force microscope including the full response of the instrumentation and demonstrates a strong dependence on temperature. The proposed new atomistic mechanism and protocols for the controlled manipulation of single atoms and vacancies on insulating surfaces may be relevant for anchoring molecules and metal clusters at these surfaces and controlling their electronic properties.

  1. Quantitative measurements of shear displacement using atomic force microscopy

    SciTech Connect

    Wang, Wenbo; Wu, Weida; Sun, Ying; Zhao, Yonggang

    2016-03-21

    We report a method to quantitatively measure local shear deformation with high sensitivity using atomic force microscopy. The key point is to simultaneously detect both torsional and buckling motions of atomic force microscopy (AFM) cantilevers induced by the lateral piezoelectric response of the sample. This requires the quantitative calibration of torsional and buckling response of AFM. This method is validated by measuring the angular dependence of the in-plane piezoelectric response of a piece of piezoelectric α-quartz. The accurate determination of the amplitude and orientation of the in-plane piezoelectric response, without rotation, would greatly enhance the efficiency of lateral piezoelectric force microscopy.

  2. Dressed-atom description of the bichromatic force

    SciTech Connect

    Yatsenko, Leonid; Metcalf, Harold

    2004-12-01

    We develop a dressed-atom picture of the bichromatic force in two standing waves using a Floquet approach. It is based on previous work, but the approach allows for an interpretation of the velocity range of the force. It is limited to two-level atoms and one dimension, and the Floquet frequency is the beat between the two bichromatic optical fields. The force is mediated by Landau-Zener transitions between the dressed states of the Floquet Hamiltonian. Related topics have been addressed before in the literature, but not applied to this particular case.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Effect of dispersion forces on squeezing with Rydberg atoms

    NASA Technical Reports Server (NTRS)

    Ng, S. K.; Muhamad, M. R.; Wahiddin, M. R. B.

    1994-01-01

    We report exact results concerning the effect of dipole-dipole interaction (dispersion forces) on dynamic and steady-state characteristics of squeezing in the emitted fluorescent field from two identical coherently driven two-level atoms. The atomic system is subjected to three different damping baths in particular the normal vacuum, a broad band thermal field and a broad band squeezed vacuum. The atomic model is the Dicke model, hence possible experiments are most likely to agree with theory when performed on systems of Rydberg atoms making microwave transitions. The presence of dipole-dipole interaction can enhance squeezing for realizable values of the various parameters involved.

  5. Measurement methods in atomic force microscopy.

    PubMed

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

    2011-01-01

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

  6. Complex patterning by vertical interchange atom manipulation using atomic force microscopy.

    PubMed

    Sugimoto, Yoshiaki; Pou, Pablo; Custance, Oscar; Jelinek, Pavel; Abe, Masayuki; Perez, Ruben; Morita, Seizo

    2008-10-17

    The ability to incorporate individual atoms in a surface following predetermined arrangements may bring future atom-based technological enterprises closer to reality. Here, we report the assembling of complex atomic patterns at room temperature by the vertical interchange of atoms between the tip apex of an atomic force microscope and a semiconductor surface. At variance with previous methods, these manipulations were produced by exploring the repulsive part of the short-range chemical interaction between the closest tip-surface atoms. By using first-principles calculations, we clarified the basic mechanisms behind the vertical interchange of atoms, characterizing the key atomistic processes involved and estimating the magnitude of the energy barriers between the relevant atomic configurations that leads to these manipulations.

  7. Lorentz force actuation of a heated atomic force microscope cantilever

    NASA Astrophysics Data System (ADS)

    Lee, Byeonghee; Prater, Craig B.; King, William P.

    2012-02-01

    We report Lorentz force-induced actuation of a silicon microcantilever having an integrated resistive heater. Oscillating current through the cantilever interacts with the magnetic field around a NdFeB permanent magnet and induces a Lorentz force that deflects the cantilever. The same current induces cantilever heating. With AC currents as low as 0.2 mA, the cantilever can be oscillated as much as 80 nm at resonance with a DC temperature rise of less than 5 °C. By comparison, the AC temperature variation leads to a thermomechanical oscillation that is about 1000 times smaller than the Lorentz deflection at the cantilever resonance. The cantilever position in the nonuniform magnetic field affects the Lorentz force-induced deflection, with the magnetic field parallel to the cantilever having the largest effect on cantilever actuation. We demonstrate how the cantilever actuation can be used for imaging, and for measuring the local material softening temperature by sensing the contact resonance shift.

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

    PubMed

    Tranvouez, E; Orieux, A; Boer-Duchemin, E; Devillers, C H; Huc, V; Comtet, G; Dujardin, G

    2009-04-22

    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.

  9. MATCH: An Atom- Typing Toolset for Molecular Mechanics Force Fields

    PubMed Central

    Yesselman, Joseph D.; Price, Daniel J.; Knight, Jennifer L.; Brooks, Charles L.

    2011-01-01

    We introduce a toolset of program libraries collectively titled MATCH (Multipurpose Atom-Typer for CHARMM) for the automated assignment of atom types and force field parameters for molecular mechanics simulation of organic molecules. The toolset includes utilities for the conversion from multiple chemical structure file formats into a molecular graph. A general chemical pattern-matching engine using this graph has been implemented whereby assignment of molecular mechanics atom types, charges and force field parameters is achieved by comparison against a customizable list of chemical fragments. While initially designed to complement the CHARMM simulation package and force fields by generating the necessary input topology and atom-type data files, MATCH can be expanded to any force field and program, and has core functionality that makes it extendable to other applications such as fragment-based property prediction. In the present work, we demonstrate the accurate construction of atomic parameters of molecules within each force field included in CHARMM36 through exhaustive cross validation studies illustrating that bond increment rules derived from one force field can be transferred to another. In addition, using leave-one-out substitution it is shown that it is also possible to substitute missing intra and intermolecular parameters with ones included in a force field to complete the parameterization of novel molecules. Finally, to demonstrate the robustness of MATCH and the coverage of chemical space offered by the recent CHARMM CGENFF force field (Vanommeslaeghe, et al., JCC., 2010, 31, 671–690), one million molecules from the PubChem database of small molecules are typed, parameterized and minimized. PMID:22042689

  10. Correct height measurement in noncontact atomic force microscopy.

    PubMed

    Sadewasser, Sascha; Lux-Steiner, Martha Ch

    2003-12-31

    We demonstrate that topography measurements by noncontact atomic force microscopy are subject to residual electrostatic forces. On highly oriented pyrolitic graphite (HOPG) with a submonolayer coverage of C60, we monitor the step height from C60 to HOPG as a function of dc bias between tip and sample. Because of the different contact potential of C60 and HOPG ( approximately 50 mV), the step height is strongly dependent on the dc bias. The presented results and additional simulations demonstrate clearly that for correct height measurements it is mandatory to use a Kelvin probe force microscopy method with active compensation of electrostatic forces.

  11. Single ricin detection by atomic force microscopy chemomechanical mapping

    NASA Astrophysics Data System (ADS)

    Chen, Guojun; Zhou, Jianfeng; Park, Bosoon; Xu, Bingqian

    2009-07-01

    The authors report on a study of detecting ricin molecules immobilized on chemically modified Au (111) surface by chemomechanically mapping the molecular interactions with a chemically modified atomic force microscopy (AFM) tip. AFM images resolved the different fold-up conformations of single ricin molecule as well as their intramolecule structure of A- and B-chains. AFM force spectroscopy study of the interaction indicates that the unbinding force has a linear relation with the logarithmic force loading rate, which agrees well with calculations using one-barrier bond dissociation model.

  12. Universal aspects of adhesion and atomic force microscopy

    NASA Technical Reports Server (NTRS)

    Banerjea, Amitava; Smith, John R.; Ferrante, John

    1990-01-01

    Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

  13. Universal aspects of adhesion and atomic force microscopy

    NASA Technical Reports Server (NTRS)

    Banerjea, Amitava; Smith, John R.; Ferrante, John

    1990-01-01

    Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

  14. Improved atomic force microscope using a laser diode interferometer

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; Pax, Paul; Yi, Leon; Howells, Sam; Gallagher, Mark; Chen, Ting; Elings, Virgil; Bocek, Dan

    1992-08-01

    The performance of an atomic force microscope using a laser diode interferometer has been improved to the point where its resolution is comparable to that of laser beam deflection systems. We describe the structure of this microscope, present a model that takes into account the main parameters associated with its operation, and demonstrate its sensitivity by showing images of a small area scan with atomic resolution as well as a large area scan in a stand-alone configuration.

  15. A Dressed Atom Description of the Bichromatic Force

    NASA Astrophysics Data System (ADS)

    Yatsenko, Leonid; Metcalf, Harold

    2004-05-01

    We have elaborated on the dressed atom description of the bichromatic force initially proposed by Grimm et al(R. Grimm et al., Opt. Lett. 19), 658 (1994).^,(R. Grimm et al., Proceeding of the International School of Physics, ``Enrico Fermi", Course CXXXI, IOS Press, Amsterdam 1996.). We present two completely equivalent Floquet Hamiltonians that mimic the ``atom plus field" system of the dressed atom spectrum. One is best for high velocities and the other for small velocities (kv relative to 2δ, the bichromatic frequency difference). Then we argue that the force arises from the exchange of kinetic energy with the ``atom plus field" system. But transitions between the dressed states must occur by Landau-Zener (LZ) transitions as the atoms pass through exact or small crossings, and calculate these rates from the eigenstates of the Floquet Hamiltonian. We find that some ``anti-crossings" are passed adiabatically and some non-adiabatically, and the criterion is the atomic velocity. We find two LZ velocities that bound the range of the force, thus enabling a description of its velocity range. This is the first time that the observed capture range ± δ/2k has been calculated.

  16. Probe-rotating atomic force microscopy for determining material properties

    SciTech Connect

    Lee, Sang Heon

    2014-03-15

    In this paper, we propose a probe-rotating atomic force microscope that enables scan in an arbitrary direction in the contact imaging mode, which is difficult to achieve using a conventional atomic force microscope owing to the orientation-dependent probe and the inability to rotate the probe head. To enable rotation of the probe about its vertical axis, we employed a compact and light probe head, the sensor of which is made of an optical disk drive pickup unit. Our proposed mechanical configuration, operating principle, and control system enables axial and lateral scan in various directions.

  17. Will a Decaying Atom Feel a Friction Force?

    NASA Astrophysics Data System (ADS)

    Sonnleitner, Matthias; Trautmann, Nils; Barnett, Stephen M.

    2017-02-01

    We show how a simple calculation leads to the surprising result that an excited two-level atom moving through a 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 even 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.

  18. Will a Decaying Atom Feel a Friction Force?

    PubMed

    Sonnleitner, Matthias; Trautmann, Nils; Barnett, Stephen M

    2017-02-03

    We show how a simple calculation leads to the surprising result that an excited two-level atom moving through a 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 even 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.

  19. Universal aspects of brittle fracture, adhesion, and atomic force microscopy

    NASA Technical Reports Server (NTRS)

    Banerjea, Amitava; Ferrante, John; Smith, John R.

    1989-01-01

    This universal relation between binding energy and interatomic separation was originally discovered for adhesion at bimetallic interfaces involving the simple metals Al, Zn, Mg, and Na. It is shown here that the same universal relation extends to adhesion at transition-metal interfaces. Adhesive energies have been computed for the low-index interfaces of Al, Ni, Cu, Ag, Fe, and W, using the equivalent-crystal theory (ECT) and keeping the atoms in each semiinfinite slab fixed rigidly in their equilibrium positions. These adhesive energy curves can be scaled onto each other and onto the universal adhesion curve. The effect of tip shape on the adhesive forces in the atomic-force microscope (AFM) is studied by computing energies and forces using the ECT. While the details of the energy-distance and force-distance curves are sensitive to tip shape, all of these curves can be scaled onto the universal adhesion curve.

  20. Universal aspects of brittle fracture, adhesion, and atomic force microscopy

    NASA Technical Reports Server (NTRS)

    Banerjea, Amitava; Ferrante, John; Smith, John R.

    1989-01-01

    This universal relation between binding energy and interatomic separation was originally discovered for adhesion at bimetallic interfaces involving the simple metals Al, Zn, Mg, and Na. It is shown here that the same universal relation extends to adhesion at transition-metal interfaces. Adhesive energies have been computed for the low-index interfaces of Al, Ni, Cu, Ag, Fe, and W, using the equivalent-crystal theory (ECT) and keeping the atoms in each semiinfinite slab fixed rigidly in their equilibrium positions. These adhesive energy curves can be scaled onto each other and onto the universal adhesion curve. The effect of tip shape on the adhesive forces in the atomic-force microscope (AFM) is studied by computing energies and forces using the ECT. While the details of the energy-distance and force-distance curves are sensitive to tip shape, all of these curves can be scaled onto the universal adhesion curve.

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

    SciTech Connect

    Braunsmann, Christoph; Schäffer, Tilman E.

    2014-05-15

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

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

    PubMed Central

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

    2012-01-01

    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. PMID:23202925

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

    PubMed

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

    2012-10-08

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

  4. Dispersion forces at arbitrary distances. [between closed-shell atoms

    NASA Technical Reports Server (NTRS)

    Jacobi, N.; Csanak, G.

    1975-01-01

    The formalism of Boehm and Yaris is used to evaluate explicitly the leading term of the London dispersion force between closed-shell atoms. Instead of using the usual multipole expansion, which breaks down at intermediate internuclear distances, an analytic representation of the Born amplitude together with a general angular momentum analysis is used. As a result, expressions are obtained which reduce to the usual dispersion forces at large distances and are finite at all distances.

  5. Dispersion forces at arbitrary distances. [between closed-shell atoms

    NASA Technical Reports Server (NTRS)

    Jacobi, N.; Csanak, G.

    1975-01-01

    The formalism of Boehm and Yaris is used to evaluate explicitly the leading term of the London dispersion force between closed-shell atoms. Instead of using the usual multipole expansion, which breaks down at intermediate internuclear distances, an analytic representation of the Born amplitude together with a general angular momentum analysis is used. As a result, expressions are obtained which reduce to the usual dispersion forces at large distances and are finite at all distances.

  6. Imaging proteins with atomic force microscopy: an overview.

    PubMed

    Silva, Luciano Paulino

    2005-08-01

    Atomic force microscopy (AFM) has become a common tool for biophysical studies of proteins; mainly due its property to perform characterizations near physiological conditions. The tertiary and quaternary structures, forces driving folding-unfolding processes, and secondary structure elements can be studied in their native environments allowing high resolution level associated with small distortions. This review outlines the operational principles and applications of AFM for protein biophysics.

  7. Using Atom Interferometry to Search for New Forces

    SciTech Connect

    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.

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

    PubMed

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

    2014-04-07

    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.

  9. High-speed force mapping on living cells with a small cantilever atomic force microscope

    SciTech Connect

    Braunsmann, Christoph; Seifert, Jan; Rheinlaender, Johannes; Schäffer, Tilman E.

    2014-07-15

    The imaging speed of the wide-spread force mapping mode for quantitative mechanical measurements on soft samples in liquid with the atomic force microscope (AFM) is limited by the bandwidth of the z-scanner and viscous drag forces on the cantilever. Here, we applied high-speed, large scan-range atomic force microscopy and small cantilevers to increase the speed of force mapping by ≈10−100 times. This allowed resolving dynamic processes on living mouse embryonic fibroblasts. Cytoskeleton reorganization during cell locomotion, growth of individual cytoskeleton fibers, cell blebbing, and the formation of endocytic pits in the cell membrane were observed. Increasing the force curve rate from 2 to 300 Hz increased the measured apparent Young's modulus of the cells by about 10 times, which facilitated force mapping measurements at high speed.

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

    ERIC Educational Resources Information Center

    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…

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

    ERIC Educational Resources Information Center

    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…

  12. Uncertainty quantification in nanomechanical measurements using the atomic force microscope

    Treesearch

    Ryan Wagner; Robert Moon; Jon Pratt; Gordon Shaw; Arvind Raman

    2011-01-01

    Quantifying uncertainty in measured properties of nanomaterials is a prerequisite for the manufacture of reliable nanoengineered materials and products. Yet, rigorous uncertainty quantification (UQ) is rarely applied for material property measurements with the atomic force microscope (AFM), a widely used instrument that can measure properties at nanometer scale...

  13. Atomic force microscopy of torus-bearing pit membranes

    Treesearch

    Roland R. Dute; Thomas Elder

    2011-01-01

    Atomic force microscopy was used to compare the structures of dried, torus-bearing pit membranes from four woody species, three angiosperms and one gymnosperm. Tori of Osmanthus armatus are bipartite consisting of a pustular zone overlying parallel sets of microfibrils that form a peripheral corona. Microfibrils of the corona form radial spokes as they traverse the...

  14. Unifying theory of tapping-mode atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Paulo, Álvaro San; García, Ricardo

    2002-07-01

    We propose a general method for describing tapping-mode atomic-force microscopy. The combined participation of attractive and repulsive interactions determines the multivalued nature of the resonance curve. This, in turn, implies the coexistence of two different stable oscillations for some excitation frequencies. The coexistence of two stable oscillations depends on the driving force and tip-surface separation. Increasing the driving force inhibits the low-amplitude oscillation state. Because resolution depends on the oscillation state, we propose that the absence of the low amplitude solution is responsible for the inconsistencies observed in high-resolution imaging of biomolecules.

  15. Resolving amorphous solid-liquid interfaces by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Burson, Kristen M.; Gura, Leonard; Kell, Burkhard; Büchner, Christin; Lewandowski, Adrian L.; Heyde, Markus; Freund, Hans-Joachim

    2016-05-01

    Recent advancements in liquid atomic force microscopy make it an ideal technique for probing the structure of solid-liquid interfaces. Here, we present a structural study of a two-dimensional amorphous silica bilayer immersed in an aqueous solution utilizing liquid atomic force microscopy with sub-nanometer resolution. Structures show good agreement with atomically resolved ultra-high vacuum scanning tunneling microscopy images obtained on the same sample system, owing to the structural stability of the silica bilayer and the imaging clarity from the two-dimensional sample system. Pair distance histograms of ring center positions are utilized to develop quantitative metrics for structural comparison, and the physical origin of pair distance histogram peaks is addressed by direct assessment of real space structures.

  16. Resolving amorphous solid-liquid interfaces by atomic force microscopy

    SciTech Connect

    Burson, Kristen M.; Gura, Leonard; Kell, Burkhard; Büchner, Christin; Lewandowski, Adrian L.; Heyde, Markus Freund, Hans-Joachim

    2016-05-16

    Recent advancements in liquid atomic force microscopy make it an ideal technique for probing the structure of solid-liquid interfaces. Here, we present a structural study of a two-dimensional amorphous silica bilayer immersed in an aqueous solution utilizing liquid atomic force microscopy with sub-nanometer resolution. Structures show good agreement with atomically resolved ultra-high vacuum scanning tunneling microscopy images obtained on the same sample system, owing to the structural stability of the silica bilayer and the imaging clarity from the two-dimensional sample system. Pair distance histograms of ring center positions are utilized to develop quantitative metrics for structural comparison, and the physical origin of pair distance histogram peaks is addressed by direct assessment of real space structures.

  17. Elasticity measurement of breast cancer cells by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Xu, Chaoxian; Wang, Yuhua; Jiang, Ningcheng; Yang, Hongqin; Lin, Juqiang; Xie, Shusen

    2014-09-01

    Mechanical properties of living cells play an important role in understanding various cells' function and state. Therefore cell biomechanics is expected to become a useful tool for cancer diagnosis. In this study, atomic force microscopy (AFM) using a square pyramid probe was performed to investigate cancerous (MCF-7) and benign (MCF-10A) human breast epithelial cells. The new QITM mode was used to acquire high-resolution topographic images and elasticity of living cells. Furthermore, individual force curves were recorded at maximum loads of 0.2, 0.5 and 1 nN, and the dependence of cell's elasticity with loading force was discussed. It was showed that the cancerous cells exhibited smaller elasticity modulus in comparison to non-cancerous counterparts. The elasticity modulus increased as the loading force increased from 0.2 nN to 1 nN. This observation indicates that loading force affects the cell's apparent elasticity and it is important to choose the appropriate force applied to cells in order to distinguish normal and cancer cells. The results reveal that the mechanical properties of living cells measured by atomic force microscopy may be a useful indicator of cell type and disease.

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

    SciTech Connect

    Cantrell, John H.; Cantrell, Sean A.

    2016-03-28

    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.

  19. Resonant difference-frequency atomic force ultrasonic microscope

    NASA Technical Reports Server (NTRS)

    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. Dual-frequency resonance-tracking atomic force microscopy

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

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

  1. Analytical model of atomic-force-microscopy force curves in viscoelastic materials exhibiting power law relaxation

    NASA Astrophysics Data System (ADS)

    de Sousa, J. S.; Santos, J. A. C.; Barros, E. B.; Alencar, L. M. R.; Cruz, W. T.; Ramos, M. V.; Mendes Filho, J.

    2017-01-01

    We propose an analytical model for the force-indentation relationship in viscoelastic materials exhibiting a power law relaxation described by an exponent n, where n = 1 represents the standard viscoelastic solid (SLS) model and n < 1 represents a fractional SLS model. To validate the model, we perform nanoindentation measurements of polyacrylamide gels with atomic force microscopy (AFM) force curves. We found exponents n < 1 that depend on the bisacrylamide concentration. We also demonstrate that the fitting of AFM force curves for varying load speeds can reproduce the dynamic viscoelastic properties of those gels measured with dynamic force modulation methods.

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

    PubMed

    Miyake, Shojiro; Wang, Mei

    2015-01-01

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

  3. Simulation of liquid jet atomization coupled with forced perturbation

    NASA Astrophysics Data System (ADS)

    Yang, Xiaochuan; Turan, Ali

    2017-02-01

    In this paper, the physical coupling processes between atomization and forced perturbation are considered. The effect of perturbation frequency and amplitude has been numerically investigated via a tree-based adaptive algorithm incorporating a time-dependent incompressible two-phase Navier-Stokes solver to simulate the atomization process. An open source code Gerris is validated using theoretical, numerical, and experimental results to demonstrate the generic capability and accuracy regarding atomization both in the low- and high-speed regimes. For a low speed jet, the breakup length and droplet diameter are examined to study the effect on breakup behaviour. For the high speed case, the frequency response of the jet is essentially classified into three distinct regimes. The jet shows a strong response for the low frequency and a correspondingly weak response for the high frequency. Perturbation amplitude also affects the atomization significantly.

  4. Relative microelastic mapping of living cells by atomic force microscopy.

    PubMed Central

    A-Hassan, E; Heinz, W F; Antonik, M D; D'Costa, N P; Nageswaran, S; Schoenenberger, C A; Hoh, J H

    1998-01-01

    The spatial and temporal changes of the mechanical properties of living cells reflect complex underlying physiological processes. Following these changes should provide valuable insight into the biological importance of cellular mechanics and their regulation. The tip of an atomic force microscope (AFM) can be used to indent soft samples, and the force versus indentation measurement provides information about the local viscoelasticity. By collecting force-distance curves on a time scale where viscous contributions are small, the forces measured are dominated by the elastic properties of the sample. We have developed an experimental approach, using atomic force microscopy, called force integration to equal limits (FIEL) mapping, to produce robust, internally quantitative maps of relative elasticity. FIEL mapping has the advantage of essentially being independent of the tip-sample contact point and the cantilever spring constant. FIEL maps of living Madine-Darby canine kidney (MDCK) cells show that elasticity is uncoupled from topography and reveal a number of unexpected features. These results present a mode of high-resolution visualization in which the contrast is based on the mechanical properties of the sample. PMID:9512052

  5. Advances in Bichromatic Force Slowing of Atoms and Molecules

    NASA Astrophysics Data System (ADS)

    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.

  6. Revealing the hidden atom in graphite by low-temperature atomic force microscopy

    PubMed Central

    Hembacher, Stefan; Giessibl, Franz J.; Mannhart, Jochen; Quate, Calvin F.

    2003-01-01

    Carbon, the backbone material of life on Earth, comes in three modifications: diamond, graphite, and fullerenes. Diamond develops tetrahedral sp3 bonds, forming a cubic crystal structure, whereas graphite and fullerenes are characterized by planar sp2 bonds. Polycrystalline graphite is the basis for many products of everyday life: pencils, lubricants, batteries, arc lamps, and brushes for electric motors. In crystalline form, highly oriented pyrolytic graphite is used as a diffracting element in monochromators for x-ray and neutron scattering and as a calibration standard for scanning tunneling microscopy (STM). The graphite surface is easily prepared as a clean atomically flat surface by cleavage. This feature is attractive and is used in many laboratories as the surface of choice for “seeing atoms.” Despite the proverbial ease of imaging graphite by STM with atomic resolution, every second atom in the hexagonal surface unit cell remains hidden, and STM images show only a single atom in the unit cell. Here we present measurements with a low-temperature atomic force microscope with pico-Newton force sensitivity that reveal the hidden surface atom. PMID:14504395

  7. Revealing the hidden atom in graphite by low-temperature atomic force microscopy.

    PubMed

    Hembacher, Stefan; Giessibl, Franz J; Mannhart, Jochen; Quate, Calvin F

    2003-10-28

    Carbon, the backbone material of life on Earth, comes in three modifications: diamond, graphite, and fullerenes. Diamond develops tetrahedral sp3 bonds, forming a cubic crystal structure, whereas graphite and fullerenes are characterized by planar sp2 bonds. Polycrystalline graphite is the basis for many products of everyday life: pencils, lubricants, batteries, arc lamps, and brushes for electric motors. In crystalline form, highly oriented pyrolytic graphite is used as a diffracting element in monochromators for x-ray and neutron scattering and as a calibration standard for scanning tunneling microscopy (STM). The graphite surface is easily prepared as a clean atomically flat surface by cleavage. This feature is attractive and is used in many laboratories as the surface of choice for "seeing atoms." Despite the proverbial ease of imaging graphite by STM with atomic resolution, every second atom in the hexagonal surface unit cell remains hidden, and STM images show only a single atom in the unit cell. Here we present measurements with a low-temperature atomic force microscope with pico-Newton force sensitivity that reveal the hidden surface atom.

  8. Single-shell carbon nanotubes imaged by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Höper, Ralf; Workman, Richard K.; Chen, Dong; Sarid, Dror; Yadav, Tapesh; Withers, James C.; Loutfy, Raouf O.

    1994-05-01

    Single-shell carbon nanotubes, approximately 1 nm in diameter, have been imaged for the first time by atomic force microscopy operating in both the contact and tapping modes. For the contact mode, the height of the imaged nanotubes has been calibrated using the atomic steps of the silicon substrate on which the nanotubes were deposited. For the tapping mode, the calibration was performed using an industry-standard grating. The paper discusses substrate and sample preparation methods for the characterization by scanning probe microscopy of nanotubes deposited on a substrate.

  9. Influence of the Coriolis force in atom interferometry.

    PubMed

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

    2012-03-02

    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.

  10. Adhesion Force Measurements Using an Atomic Force Microscope Upgraded with a Linear Position Sensitive Detector

    PubMed Central

    Pierce, M.; Stuart, J.; Pungor, A.; Dryden, P.

    2012-01-01

    The atomic force microscope (AFM), in addition to providing images on an atomic scale, can be used to measure the forces between surfaces and the AFM probe. The potential uses of mapping the adhesive forces on the surface include a spatial determination of surface energy and a direct identification of surface proteins through specific protein–ligand binding interactions. The capabilities of the AFM to measure adhesive forces can be extended by replacing the four-quadrant photodiode detection sensor with an external linear position sensitive detector and by utilizing a dedicated user-programmable signal generator and acquisiton system. Such an upgrade enables the microscope to measure in the larger dynamic range of adhesion forces, improves the sensitivity and linearity of the measurement, and eliminates the problems inherent to the multiple repetitious contacts between the AFM probe and the specimen surface. PMID:25125792

  11. Atomic-scale mechanical properties of orientated C60 molecules revealed by noncontact atomic force microscopy.

    PubMed

    Pawlak, Rémy; Kawai, Shigeki; Fremy, Sweetlana; Glatzel, Thilo; Meyer, Ernst

    2011-08-23

    In this work, the mechanical properties of C(60) molecules adsorbed on Cu(111) are measured by tuning-fork-based noncontact atomic force microscopy (nc-AFM) and spectroscopy at cryogenic conditions. Site-specific tip-sample force variations are detected above the buckyball structure. Moreover, high-resolution images obtained by nc-AFM show the chemical structure of this molecule and describes unambiguously its orientations on the surface.

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

    PubMed Central

    Miyahara, Yoichi; Aeschimann, Laure; Grütter, Peter

    2015-01-01

    Summary Optical beam deflection systems are widely used in cantilever based atomic force microscopy (AFM). Most commercial cantilevers have a reflective metal coating on the detector side to increase the reflectivity in order to achieve a high signal on the photodiode. Although the reflective coating is usually much thinner than the cantilever, it can still significantly contribute to the damping of the cantilever, leading to a lower mechanical quality factor (Q-factor). In dynamic mode operation in high vacuum, a cantilever with a high Q-factor is desired in order to achieve a lower minimal detectable force. The reflective coating can also increase the low-frequency force noise. In contact mode and force spectroscopy, a cantilever with minimal low-frequency force noise is desirable. We present a study on cantilevers with a partial reflective coating on the detector side. For this study, soft (≈0.01 N/m) and stiff (≈28 N/m) rectangular cantilevers were used with a custom partial coating at the tip end of the cantilever. The Q-factor, the detection and the force noise of fully coated, partially coated and uncoated cantilevers are compared and force distance curves are shown. Our results show an improvement in low-frequency force noise and increased Q-factor for the partially coated cantilevers compared to fully coated ones while maintaining the same reflectivity, therefore making it possible to combine the best of both worlds. PMID:26199849

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

    PubMed

    Schumacher, Zeno; Miyahara, Yoichi; Aeschimann, Laure; Grütter, Peter

    2015-01-01

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

  14. Quantification of cell-substratum interactions by atomic force microscopy.

    PubMed

    Li, Qian; Becker, Thomas; Sand, Wolfgang

    2017-08-30

    Microorganisms adhere to surfaces and, subsequently, form biofilms. This process is of major interest in biotechnology, environmental sciences and medicine. It is crucial to understand the mechanisms of interactions between substratum and cells or biofilms. By combining force mapping-based atomic force microscopy (AFM) with pyrite-modified cantilevers we quantified the adhesion forces between undenatured planktonic or biofilm cells of Sulfobacillus thermosulfidooxidans and the substratum pyrite with values of 2.6±0.3nN and 77.3±7.1pN, respectively. This was achieved under natural conditions without any artefact resulting from the use of denaturing chemicals such as glutaraldehyde. This new technique is unique for quantifying the real interaction forces between cells or biofilms and their substrata. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Interplay between Switching Driven by the Tunneling Current and Atomic Force of a Bistable Four-Atom Si Quantum Dot.

    PubMed

    Yamazaki, Shiro; Maeda, Keisuke; Sugimoto, Yoshiaki; Abe, Masayuki; Zobač, Vladimír; Pou, Pablo; Rodrigo, Lucia; Mutombo, Pingo; Pérez, Ruben; Jelínek, Pavel; Morita, Seizo

    2015-07-08

    We assemble bistable silicon quantum dots consisting of four buckled atoms (Si4-QD) using atom manipulation. We demonstrate two competing atom switching mechanisms, downward switching induced by tunneling current of scanning tunneling microscopy (STM) and opposite upward switching induced by atomic force of atomic force microscopy (AFM). Simultaneous application of competing current and force allows us to tune switching direction continuously. Assembly of the few-atom Si-QDs and controlling their states using versatile combined AFM/STM will contribute to further miniaturization of nanodevices.

  16. Molecular determinants of bacterial adhesion monitored by atomic force microscopy

    PubMed Central

    Razatos, Anneta; Ong, Yea-Ling; Sharma, Mukul M.; Georgiou, George

    1998-01-01

    Bacterial adhesion and the subsequent formation of biofilm are major concerns in biotechnology and medicine. The initial step in bacterial adhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic interactions. The precise manner in which the force of interaction is affected by cell surface components and by the physiochemical properties of materials is not well understood. Here, we show that atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution. Interactions between the cantilever tip and confluent monolayers of isogenic strains of Escherichia coli mutants exhibiting subtle differences in cell surface composition were measured. It was shown that the adhesion force is affected by the length of core lipopolysaccharide molecules on the E. coli cell surface and by the production of the capsular polysaccharide, colanic acid. Furthermore, by modifying the atomic force microscope tip we developed a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest. This information will be critical for the design of materials that are resistant to bacterial adhesion. PMID:9736689

  17. Sampling Protein Form and Function with the Atomic Force Microscope*

    PubMed Central

    Baclayon, Marian; Roos, Wouter H.; Wuite, Gijs J. L.

    2010-01-01

    To study the structure, function, and interactions of proteins, a plethora of techniques is available. Many techniques sample such parameters in non-physiological environments (e.g. in air, ice, or vacuum). Atomic force microscopy (AFM), however, is a powerful biophysical technique that can probe these parameters under physiological buffer conditions. With the atomic force microscope operating under such conditions, it is possible to obtain images of biological structures without requiring labeling and to follow dynamic processes in real time. Furthermore, by operating in force spectroscopy mode, it can probe intramolecular interactions and binding strengths. In structural biology, it has proven its ability to image proteins and protein conformational changes at submolecular resolution, and in proteomics, it is developing as a tool to map surface proteomes and to study protein function by force spectroscopy methods. The power of AFM to combine studies of protein form and protein function enables bridging various research fields to come to a comprehensive, molecular level picture of biological processes. We review the use of AFM imaging and force spectroscopy techniques and discuss the major advances of these experiments in further understanding form and function of proteins at the nanoscale in physiologically relevant environments. PMID:20562411

  18. Method for lateral force calibration in atomic force microscope using MEMS microforce sensor.

    PubMed

    Dziekoński, Cezary; Dera, Wojciech; Jarząbek, Dariusz M

    2017-06-14

    In this paper we present a simple and direct method for the lateral force calibration constant determination. Our procedure does not require any knowledge about material or geometrical parameters of an investigated cantilever. We apply a commercially available microforce sensor with advanced electronics for direct measurement of the friction force applied by the cantilever's tip to a flat surface of the microforce sensor measuring beam. Due to the third law of dynamics, the friction force of the equal value tilts the AFM cantilever. Therefore, torsional (lateral force) signal is compared with the signal from the microforce sensor and the lateral force calibration constant is determined. The method is easy to perform and could be widely used for the lateral force calibration constant determination in many types of atomic force microscopes. Copyright © 2017. Published by Elsevier B.V.

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

    PubMed

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

    2009-07-01

    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 separate feedback loop for thermal drift compensation, and the differential signal can be used to cancel the shift in zero-force level of the AFM.

  20. Ubiquitous mechanisms of energy dissipation in noncontact atomic force microscopy.

    PubMed

    Ghasemi, S Alireza; Goedecker, Stefan; Baratoff, Alexis; Lenosky, Thomas; Meyer, Ernst; Hug, Hans J

    2008-06-13

    Atomistic simulations considering larger tip structures than hitherto assumed reveal novel dissipation mechanisms in noncontact atomic force microscopy. The potential energy surfaces of realistic silicon tips exhibit many energetically close local minima that correspond to different structures. Most of them easily deform, thus causing dissipation arising from hysteresis in force versus distance characteristics. Furthermore, saddle points which connect local minima can suddenly switch to connect different minima. Configurations driven into metastability by the tip motion can thus suddenly access lower energy structures when thermal activation becomes allowed within the time required to detect the resulting average dissipation.

  1. [Atomic force microscopy: a tool to analyze the viral cycle].

    PubMed

    Bernaud, Julien; Castelnovo, Martin; Muriaux, Delphine; Faivre-Moskalenko, Cendrine

    2015-05-01

    Each step of the HIV-1 life cycle frequently involves a change in the morphology and/or mechanical properties of the viral particle or core. The atomic force microscope (AFM) constitutes a powerful tool for characterizing these physical changes at the scale of a single virus. Indeed, AFM enables the visualization of viral capsids in a controlled physiological environment and to probe their mechanical properties by nano-indentation. Finally, AFM force spectroscopy allows to characterize the affinities between viral envelope proteins and cell receptors at the single molecule level.

  2. Non-Markovianity in atom-surface dispersion forces

    DOE PAGES

    Intravaia, F.; Behunin, R. O.; Henkel, C.; ...

    2016-10-18

    Here, we discuss the failure of the Markov approximation in the description of atom-surface fluctuation-induced interactions, both in equilibrium (Casimir-Polder forces) and out of equilibrium (quantum friction). Using general theoretical arguments, we show that the Markov approximation can lead to erroneous predictions of such phenomena with regard to both strength and functional dependencies on system parameters. Particularly, we show that the long-time power-law tails of two-time dipole correlations and their corresponding low-frequency behavior, neglected in the Markovian limit, affect the prediction of the force. These findings highlight the importance of non-Markovian effects in dispersion interactions.

  3. Surface modifications with Lissajous trajectories using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Cai, Wei; Yao, Nan

    2015-09-01

    In this paper, we report a method for atomic force microscopy surface modifications with single-tone and multiple-resolution Lissajous trajectories. The tip mechanical scratching experiments with two series of Lissajous trajectories were carried out on monolayer films. The scratching processes with two scan methods have been illustrated. As an application, the tip-based triboelectrification phenomenon on the silicon dioxide surface with Lissajous trajectories was investigated. The triboelectric charges generated within the tip rubbed area on the surface were characterized in-situ by scanning Kelvin force microscopy. This method would provide a promising and cost-effective approach for surface modifications and nanofabrication.

  4. Mapping and control of atomic force on Si(1 1 1)square root(3) x square root(3)-Ag surface using noncontact atomic force microscope.

    PubMed

    Morita, S; Sugawara, Y

    2002-05-01

    We demonstrated the possibility of measuring the three-dimensional force-related map with true atomic resolution between an Si tip and Si(1 1 1)square root(3) x square root(3)-Ag sample surface by measuring the tip-sample distance dependence of noncontact atomic force microscope (NC-AFM) image, i.e. atomically resolved atomic force spectroscopy. Furthermore, we demonstrated the possibility of controlling the interaction force between the atom on the tip apex and a sample atom of Si(1 1 1)square root(3) x square root(3)-Ag surface on an atomic scale by placing an Ag atom on the Si tip apex instead of Si atom.

  5. Mechanical characterization of cellulose single nanofiber by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Zhai, Lindong; Kim, Jeong Woong; Lee, Jiyun; Kim, Jaehwan

    2017-04-01

    Cellulose fibers are strong natural fibers and they are renewable, biodegradable and the most abundant biopolymer in the world. So to develop new cellulose fibers based products, the mechanical properties of cellulose nanofibers would be a key. The atomic microscope is used to measure the mechanical properties of cellulose nanofibers based on 3-points bending of cellulose nanofiber. The cellulose nanofibers were generated for an aqueous counter collision system. The cellulose microfibers were nanosized under 200 MPa high pressure. The cellulose nanofiber suspension was diluted with DI water and sprayed on the silicon groove substrate. By performing a nanoscale 3-points bending test using the atomic force microscopy, a known force was applied on the center of the fiber. The elastic modulus of the single nanofiber is obtained by calculating the fiber deflection and several parameters. The elastic modulus values were obtained from different resources of cellulose such as hardwood, softwood and cotton.

  6. Frequency-dependent viscoelasticity measurement by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Nan; Wong, Kenneth Kar Ho; de Bruyn, John R.; Hutter, Jeffrey L.

    2009-02-01

    We demonstrate a new technique for investigating viscoelastic properties of soft materials using the atomic force microscope. A small oscillatory voltage is added to the deflection signal of the atomic force microscope causing a vertical oscillatory sample motion. Monitoring the amplitude and phase of this motion allows determination of the viscous and elastic moduli of the sample as a function of frequency during contact imaging. This technique is applied to suspended poly(vinyl alcohol) nanofibers and poly(vinyl alcohol) hydrogels, giving results similar to those measured using traditional static methods. However, the moduli of both the fibers and the hydrogels show a significant frequency dependence. The Young's modulus of the fibers increases with frequency, while for the viscoelastic hydrogels, the storage modulus dominates the mechanical response at low frequency whereas the loss modulus dominates at high frequency.

  7. Atomic force microscopy images of lyotropic lamellar phases.

    PubMed

    Garza, C; Thieghi, L T; Castillo, R

    2007-02-07

    For the very first time, atomic force microscope images of lamellar phases were observed combined with a freeze fracture technique that does not involve the use of replicas. Samples are rapidly frozen, fractured, and scanned directly with atomic force microscopy, at liquid nitrogen temperature and in high vacuum. This procedure can be used to investigate micro-structured liquids. The lamellar phases in Sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water and in C12E5/water systems were used to asses this new technique. Our observations were compared with x-ray diffraction measurements and with other freeze fracture methods reported in the literature. Our results show that this technique is useful to image lyotropic lamellar phases and the estimated repeat distances for lamellar periodicity are consistent with those obtained by x-ray diffraction.

  8. Automated manipulation of carbon nanotubes using atomic force microscopy.

    PubMed

    Zhang, Chao; Wu, Sen; Fu, Xing

    2013-01-01

    The manipulation of carbon nanotubes is an important and essential step for carbon-based nanodevice or nanocircuit assembly. However, the conventional push-and-image approach of manipulating carbon nanotubes using atomic force microscopy has low efficiency on account of the reduplicated scanning process during manipulation. In this article, an automated manipulation system is designed and tested. This automated manipulation system, which includes an atomic force microscope platform and a self-developed computer program for one-dimensional manipulation, is capable of automatically moving any assigned individual carbon nanotube to a defined target location without any intermediate scanning procedure. To demonstrate the high-efficiency of this automated manipulation system and its potential applications in nanoassembly, two experiments were conducted. The first experiment used this system to manipulate a carbon nanotube to a defined target location. In the second experiment, this system was used to automatically manipulate several carbon nanotubes for generating and translating a defined pattern of nanotubes.

  9. Nanoindentation of gold nanorods with an atomic force microscope

    NASA Astrophysics Data System (ADS)

    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.

  10. Atomic Force Microscopy of the Nacreous Layer in Mollusc Shells

    DTIC Science & Technology

    1994-02-25

    studies of the nacreous layers of molluscan shells . In particular, our studies of native and treated samples have highlighted significant morphological...sUnh S. PUNOWNG NUMIEMS Atomic Force Microscopy of the Nacreous Layer N00014-90-J-1159 in Mollusc Shells -. AUThORtS) S. Manne, C. M. Zaremba, R. Giles...tablets which comprise the mineral portion of nacre, in two types of molluscs, a bivalve (Arrina serrate) and a gastropod (Haliois rufescens). By

  11. Model based control of dynamic atomic force microscope

    SciTech Connect

    Lee, Chibum; Salapaka, Srinivasa M.

    2015-04-15

    A model-based robust control approach is proposed that significantly improves imaging bandwidth for the dynamic mode atomic force microscopy. A model for cantilever oscillation amplitude and phase dynamics is derived and used for the control design. In particular, the control design is based on a linearized model and robust H{sub ∞} control theory. This design yields a significant improvement when compared to the conventional proportional-integral designs and verified by experiments.

  12. Atomic force microscope observations of otoconia in the newt

    NASA Technical Reports Server (NTRS)

    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.

  13. Model based control of dynamic atomic force microscope

    NASA Astrophysics Data System (ADS)

    Lee, Chibum; Salapaka, Srinivasa M.

    2015-04-01

    A model-based robust control approach is proposed that significantly improves imaging bandwidth for the dynamic mode atomic force microscopy. A model for cantilever oscillation amplitude and phase dynamics is derived and used for the control design. In particular, the control design is based on a linearized model and robust H∞ control theory. This design yields a significant improvement when compared to the conventional proportional-integral designs and verified by experiments.

  14. Model based control of dynamic atomic force microscope.

    PubMed

    Lee, Chibum; Salapaka, Srinivasa M

    2015-04-01

    A model-based robust control approach is proposed that significantly improves imaging bandwidth for the dynamic mode atomic force microscopy. A model for cantilever oscillation amplitude and phase dynamics is derived and used for the control design. In particular, the control design is based on a linearized model and robust H(∞) control theory. This design yields a significant improvement when compared to the conventional proportional-integral designs and verified by experiments.

  15. Probing starch-iodine interaction by atomic force microscopy.

    PubMed

    Du, Xiongwei; An, Hongjie; Liu, Zhongdong; Yang, Hongshun; Wei, Lijuan

    2014-01-01

    We explored the interaction of iodine with three crystalline type starches, corn, potato, and sweet potato starches using atomic force microscopy. Results revealed that starch molecules aggregated through interaction with iodine solution as well as iodine vapor. Detailed fine structures such as networks, chains, and super-helical structures were found in iodide solution tests. The nanostructures formed due to iodine adsorption could help to understand the formation and properties of the starch-iodine complex. © 2013 Wiley Periodicals, Inc.

  16. Probing stem cell differentiation using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    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.

  17. A simple method for producing flattened atomic force microscopy tips.

    PubMed

    Biagioni, P; Farahani, J N; Mühlschlegel, P; Eisler, H-J; Pohl, D W; Hecht, B

    2008-01-01

    We describe a simple and reliable procedure for obtaining a flat plateau on top of standard silicon nitride atomic force microscopy tips by scanning them over the focus of a high-numerical-aperture objective illuminated by near-infrared ultrashort laser pulses. Flattened tips produced this way exhibit a plateau that is parallel to the substrate when the cantilever is mounted. They represent a valid and cost-effective alternative to commercially available plateau tips.

  18. Atomic force microscope observations of otoconia in the newt

    NASA Technical Reports Server (NTRS)

    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.

  19. Non-contact atomic-level interfacial force microscopy

    SciTech Connect

    Houston, J.E.; Fleming, J.G.

    1997-02-01

    The scanning force microscopies (notably the Atomic Force Microscope--AFM), because of their applicability to nearly all materials, are presently the most widely used of the scanning-probe techniques. However, the AFM uses a deflection sensor to measure sample/probe forces which suffers from an inherent mechanical instability that occurs when the rate of change of the force with respect to the interfacial separation becomes equal to the spring constant of the deflecting member. This instability dramatically limits the breadth of applicability of AFM-type techniques to materials problems. In the course of implementing a DOE sponsored basic research program in interfacial adhesion, a self-balancing force sensor concept has been developed and incorporated into an Interfacial Force Microscopy (IFM) system by Sandia scientists. This sensor eliminates the instability problem and greatly enhances the applicability of the scanning force-probe technique to a broader range of materials and materials parameters. The impact of this Sandia development was recognized in 1993 by a Department of Energy award for potential impact on DOE programs and by an R and D 100 award for one of the most important new products of 1994. However, in its present stage of development, the IFM is strictly a research-level tool and a CRADA was initiated in order to bring this sensor technology into wide-spread availability by making it accessible in the form of a commercial instrument. The present report described the goals, approach and results of this CRADA effort.

  20. Manipulation of Proteins on Mica by Atomic Force Microscopy

    PubMed Central

    Lea, A. S.; Pungor, A; Hlady, V; Andrade, J. D.; Herron, J. N.; Voss, E. W.

    2012-01-01

    The atomic force microscope was used to image adsorption of a monoclonal IgM on mica in real time. Under the smallest possible force we could achieve (<4 nN), the cantilever tip behaved as a molecular broom and was observed to orient protein aggregates in strands oriented perpendicularly to the facet of the cantilever tip. Rotating the scan direction preserved the orientational relationship, as seen by the formation of rotated strands. When the applied force was increased, the distance between the strands increased, indicating the amount of protein that can be swept depends on the applied force. The effect of scanning increased the apparent surface coverage of IgM. Manipulation of a deposited fibrinogen layer with a 4-nN repulsive force was observed only after tens of minutes, but not to the extent that strands formed, indicating a greater adhesion between the fibrinogen and mica than between IgM and mica. With an applied repulsive force of 30 nN, fibrinogen strands formed and the protein was manipulated to produce the block letter U. At a much higher repulsive force, the entire scanning area was swept clean. PMID:25147425

  1. Atomic force microscopy application in biological research: a review study.

    PubMed

    Vahabi, Surena; Nazemi Salman, Bahareh; Javanmard, Anahita

    2013-06-01

    Atomic force microscopy (AFM) is a three-dimensional topographic technique with a high atomic resolution to measure surface roughness. AFM is a kind of scanning probe microscope, and its near-field technique is based on the interaction between a sharp tip and the atoms of the sample surface. There are several methods and many ways to modify the tip of the AFM to investigate surface properties, including measuring friction, adhesion forces and viscoelastic properties as well as determining the Young modulus and imaging magnetic or electrostatic properties. The AFM technique can analyze any kind of samples such as polymers, adsorbed molecules, films or fibers, and powders in the air whether in a controlled atmosphere or in a liquid medium. In the past decade, the AFM has emerged as a powerful tool to obtain the nanostructural details and biomechanical properties of biological samples, including biomolecules and cells. The AFM applications, techniques, and -in particular- its ability to measure forces, are not still familiar to most clinicians. This paper reviews the literature on the main principles of the AFM modality and highlights the advantages of this technique in biology, medicine, and- especially- dentistry. This literature review was performed through E-resources, including Science Direct, PubMed, Blackwell Synergy, Embase, Elsevier, and Scholar Google for the references published between 1985 and 2010.

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

    PubMed

    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.

  3. Fabrication of electron beam deposited tip for atomic-scale atomic force microscopy in liquid.

    PubMed

    Miyazawa, K; Izumi, H; Watanabe-Nakayama, T; Asakawa, H; Fukuma, T

    2015-03-13

    Recently, possibilities of improving operation speed and force sensitivity in atomic-scale atomic force microscopy (AFM) in liquid using a small cantilever with an electron beam deposited (EBD) tip have been intensively explored. However, the structure and properties of an EBD tip suitable for such an application have not been well-understood and hence its fabrication process has not been established. In this study, we perform atomic-scale AFM measurements with a small cantilever and clarify two major problems: contaminations from a cantilever and tip surface, and insufficient mechanical strength of an EBD tip having a high aspect ratio. To solve these problems, here we propose a fabrication process of an EBD tip, where we attach a 2 μm silica bead at the cantilever end and fabricate a 500-700 nm EBD tip on the bead. The bead height ensures sufficient cantilever-sample distance and enables to suppress long-range interaction between them even with a short EBD tip having high mechanical strength. After the tip fabrication, we coat the whole cantilever and tip surface with Si (30 nm) to prevent the generation of contamination. We perform atomic-scale AFM imaging and hydration force measurements at a mica-water interface using the fabricated tip and demonstrate its applicability to such an atomic-scale application. With a repeated use of the proposed process, we can reuse a small cantilever for atomic-scale measurements for several times. Therefore, the proposed method solves the two major problems and enables the practical use of a small cantilever in atomic-scale studies on various solid-liquid interfacial phenomena.

  4. Fabrication of electron beam deposited tip for atomic-scale atomic force microscopy in liquid

    NASA Astrophysics Data System (ADS)

    Miyazawa, K.; Izumi, H.; Watanabe-Nakayama, T.; Asakawa, H.; Fukuma, T.

    2015-03-01

    Recently, possibilities of improving operation speed and force sensitivity in atomic-scale atomic force microscopy (AFM) in liquid using a small cantilever with an electron beam deposited (EBD) tip have been intensively explored. However, the structure and properties of an EBD tip suitable for such an application have not been well-understood and hence its fabrication process has not been established. In this study, we perform atomic-scale AFM measurements with a small cantilever and clarify two major problems: contaminations from a cantilever and tip surface, and insufficient mechanical strength of an EBD tip having a high aspect ratio. To solve these problems, here we propose a fabrication process of an EBD tip, where we attach a 2 μm silica bead at the cantilever end and fabricate a 500-700 nm EBD tip on the bead. The bead height ensures sufficient cantilever-sample distance and enables to suppress long-range interaction between them even with a short EBD tip having high mechanical strength. After the tip fabrication, we coat the whole cantilever and tip surface with Si (30 nm) to prevent the generation of contamination. We perform atomic-scale AFM imaging and hydration force measurements at a mica-water interface using the fabricated tip and demonstrate its applicability to such an atomic-scale application. With a repeated use of the proposed process, we can reuse a small cantilever for atomic-scale measurements for several times. Therefore, the proposed method solves the two major problems and enables the practical use of a small cantilever in atomic-scale studies on various solid-liquid interfacial phenomena.

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

    PubMed

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

    2014-09-15

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

  6. Observation of Individual Fluorine Atom from Highly Oriented Poly (tetrafluoroethylene) Films by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.,; Paley, Mark S.

    1999-01-01

    Direct observation of the film thickness, molecular structure and individual fluorine atoms from highly oriented poly(tetrafluoroethylene) (PTFE) films were achieved using atomic force microscopy (AFM). A thin PTFE film is mechanically deposited onto a smooth glass substrate at specific temperatures by a friction transfer technique. Atomic resolution images of these films show that the chain-like helical structures of the PTFE macromolecules are aligned parallel to each other with an intermolecular spacing of 5.72 A, and individual fluorine atoms are clearly observed along these twisted molecular chains with an interatomic spacing of 2.75 A. Furthermore, the first direct AFM measurements for the radius of the fluorine-helix, and of the carbon-helix in sub-angstrom scale are reported as 1.70 A and 0.54 A respectively.

  7. Observation of Individual Fluorine Atoms from Highly Oriented Poly(Tetrafluoroethylene) Films by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Lee, J. A.

    2000-01-01

    Direct observation of the film thickness, molecular structure, and individual fluorine atoms from highly oriented poly(tetrafluoroethylene) (PTFE) films were achieved using atomic force microscopy (AFM). A thin PTFE film is mechanically deposited onto a smooth glass substrate at specific temperatures by a friction-transfer technique. Atomic resolution images of these films show that the chain-like helical structures of the PTFE macromolecules are aligned parallel to each other with an intermolecular spacing of 5.72 A, and individual fluorine atoms are clearly observed along these twisted molecular chains with an interatomic spacing of 2.75 A. Furthermore, the first direct AFM measurements for the radius of the fluorine-helix, and of the carbon-helix in sub-angstrom scale are reported as 1.7 and 0.54 A respectively.

  8. Observation of Individual Fluorine Atom from Highly Oriented Poly (tetrafluoroethylene) Films by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.,; Paley, Mark S.

    1999-01-01

    Direct observation of the film thickness, molecular structure and individual fluorine atoms from highly oriented poly(tetrafluoroethylene) (PTFE) films were achieved using atomic force microscopy (AFM). A thin PTFE film is mechanically deposited onto a smooth glass substrate at specific temperatures by a friction transfer technique. Atomic resolution images of these films show that the chain-like helical structures of the PTFE macromolecules are aligned parallel to each other with an intermolecular spacing of 5.72 A, and individual fluorine atoms are clearly observed along these twisted molecular chains with an interatomic spacing of 2.75 A. Furthermore, the first direct AFM measurements for the radius of the fluorine-helix, and of the carbon-helix in sub-angstrom scale are reported as 1.70 A and 0.54 A respectively.

  9. Atomic species identification at the (101) anatase surface by simultaneous scanning tunnelling and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Stetsovych, Oleksandr; Todorović, Milica; Shimizu, Tomoko K.; Moreno, César; Ryan, James William; León, Carmen Pérez; Sagisaka, Keisuke; Palomares, Emilio; Matolín, Vladimír; Fujita, Daisuke; Perez, Ruben; Custance, Oscar

    2015-06-01

    Anatase is a pivotal material in devices for energy-harvesting applications and catalysis. Methods for the accurate characterization of this reducible oxide at the atomic scale are critical in the exploration of outstanding properties for technological developments. Here we combine atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), supported by first-principles calculations, for the simultaneous imaging and unambiguous identification of atomic species at the (101) anatase surface. We demonstrate that dynamic AFM-STM operation allows atomic resolution imaging within the material's band gap. Based on key distinguishing features extracted from calculations and experiments, we identify candidates for the most common surface defects. Our results pave the way for the understanding of surface processes, like adsorption of metal dopants and photoactive molecules, that are fundamental for the catalytic and photovoltaic applications of anatase, and demonstrate the potential of dynamic AFM-STM for the characterization of wide band gap materials.

  10. Atomic species identification at the (101) anatase surface by simultaneous scanning tunnelling and atomic force microscopy

    PubMed Central

    Stetsovych, Oleksandr; Todorović, Milica; Shimizu, Tomoko K.; Moreno, César; Ryan, James William; León, Carmen Pérez; Sagisaka, Keisuke; Palomares, Emilio; Matolín, Vladimír; Fujita, Daisuke; Perez, Ruben; Custance, Oscar

    2015-01-01

    Anatase is a pivotal material in devices for energy-harvesting applications and catalysis. Methods for the accurate characterization of this reducible oxide at the atomic scale are critical in the exploration of outstanding properties for technological developments. Here we combine atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), supported by first-principles calculations, for the simultaneous imaging and unambiguous identification of atomic species at the (101) anatase surface. We demonstrate that dynamic AFM-STM operation allows atomic resolution imaging within the material's band gap. Based on key distinguishing features extracted from calculations and experiments, we identify candidates for the most common surface defects. Our results pave the way for the understanding of surface processes, like adsorption of metal dopants and photoactive molecules, that are fundamental for the catalytic and photovoltaic applications of anatase, and demonstrate the potential of dynamic AFM-STM for the characterization of wide band gap materials. PMID:26118408

  11. Adhesion Forces between Lewis(X) Determinant Antigens as Measured by Atomic Force Microscopy.

    PubMed

    Tromas, C; Rojo, J; de la Fuente, J M; Barrientos, A G; García, R; Penadés, S

    2001-01-01

    The adhesion forces between individual molecules of Lewis(X) trisaccharide antigen (Le(X) ) have been measured in water and in calcium solution by using atomic force microscopy (AFM, see graph). These results demonstrate the self-recognition capability of this antigen, and reinforce the hypothesis that carbohydrate-carbohydrate interaction could be considered as the first step in the cell-adhesion process in nature. Copyright © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

  12. Cooperatively enhanced dipole forces from artificial atoms in trapped nanodiamonds

    NASA Astrophysics Data System (ADS)

    Juan, Mathieu L.; Bradac, Carlo; Besga, Benjamin; Johnsson, Mattias; Brennen, Gavin; Molina-Terriza, Gabriel; Volz, Thomas

    2017-03-01

    Optical trapping is a powerful tool to manipulate small particles, from micrometre-size beads in liquid environments to single atoms in vacuum. The trapping mechanism relies on the interaction between a dipole and the electric field of laser light. In atom trapping, the dominant contribution to the associated force typically comes from the allowed optical transition closest to the laser wavelength, whereas for mesoscopic particles it is given by the polarizability of the bulk material. Here, we show that for nanoscale diamond crystals containing a large number of artificial atoms, nitrogen-vacancy colour centres, the contributions from both the nanodiamond and the colour centres to the optical trapping strength can be simultaneously observed in a noisy liquid environment. For wavelengths around the zero-phonon line transition of the colour centres, we observe a 10% increase of overall trapping strength. The magnitude of this effect suggests that due to the large density of centres, cooperative effects between the artificial atoms contribute to the observed modification of the trapping strength. Our approach may enable the study of cooperativity in nanoscale solid-state systems and the use of atomic physics techniques in the field of nano-manipulation.

  13. Atomically resolved scanning force studies of vicinal Si(111)

    NASA Astrophysics Data System (ADS)

    Pérez León, Carmen; Drees, Holger; Wippermann, Stefan Martin; Marz, Michael; Hoffmann-Vogel, Regina

    2017-06-01

    Well-ordered stepped semiconductor surfaces attract intense attention owing to the regular arrangements of their atomic steps that makes them perfect templates for the growth of one-dimensional systems, e.g., nanowires. Here, we report on the atomic structure of the vicinal Si (111 ) surface with 10∘ miscut investigated by a joint frequency-modulation scanning force microscopy (FM-SFM) and ab initio approach. This popular stepped surface contains 7 ×7 -reconstructed terraces oriented along the Si (111 ) direction, separated by a stepped region. Recently, the atomic structure of this triple step based on scanning tunneling microscopy (STM) images has been subject of debate. Unlike STM, SFM atomic resolution capability arises from chemical bonding of the tip apex with the surface atoms. Thus, for surfaces with a corrugated density of states such as semiconductors, SFM provides complementary information to STM and partially removes the dependency of the topography on the electronic structure. Our FM-SFM images with unprecedented spatial resolution on steps coincide with the model based on a (7 7 10 ) orientation of the surface and reveal structural details of this surface. Two different FM-SFM contrasts together with density functional theory calculations explain the presence of defects, buckling, and filling asymmetries on the surface. Our results evidence the important role of charge transfers between adatoms, restatoms, and dimers in the stabilisation of the structure of the vicinal surface.

  14. Atomic force microscopy force mapping in the study of supported lipid bilayers.

    PubMed

    Li, James K; Sullan, Ruby May A; Zou, Shan

    2011-02-15

    Investigating the structural and mechanical properties of lipid bilayer membrane systems is vital in elucidating their biological function. One route to directly correlate the morphology of phase-segregated membranes with their indentation and rupture mechanics is the collection of atomic force microscopy (AFM) force maps. These force maps, while containing rich mechanical information, require lengthy processing time due to the large number of force curves needed to attain a high spatial resolution. A force curve analysis toolset was created to perform data extraction, calculation and reporting specifically in studying lipid membrane morphology and mechanical stability. The procedure was automated to allow for high-throughput processing of force maps with greatly reduced processing time. The resulting program was successfully used in systematically analyzing a number of supported lipid membrane systems in the investigation of their structure and nanomechanics.

  15. Interpreting atomic force microscopy measurements of hydrodynamic and surface forces with nonlinear parametric estimation.

    PubMed

    Cui, Song; Manica, Rogerio; Tabor, Rico F; Chan, Derek Y C

    2012-10-01

    A nonlinear parameter estimation method has been developed to extract the separation-dependent surface force and cantilever spring constant from atomic force microscope data taken at different speeds for the interaction between a silica colloidal probe and plate in aqueous solution. The distinguishing feature of this approach is that it exploits information from the velocity dependence of the force-displacement data due to hydrodynamic interaction to provide an unbiased estimate of the functional form of the separation-dependent surface force. An assumed function for the surface force with unknown parameters is not required. In addition, the analysis also yields a consistent estimate of the in situ cantilever spring constant. In combination with data from static force measurements, this approach can further be used to quantify the extent of hydrodynamic slip.

  16. Dielectric constants by multifrequency non-contact atomic force microscopy.

    PubMed

    Kumar, Bharat; Bonvallet, Joseph C; Crittenden, Scott R

    2012-01-20

    We present a method to obtain capacitive forces and dielectric constants of ultra-thin films on metallic substrates using multifrequency non-contact atomic force microscopy with amplitude feedback in air. Capacitive forces are measured via cantilever oscillations induced at the second bending mode and dielectric constants are calculated by fitting an analytic expression for the capacitance (Casuso et al 2007 Appl. Phys. Lett. 91 063111) to the experimental data. Dielectric constants for self-assembled monolayers of thiol molecules on gold (2.0±0.1) and sputtered SiO2 (3.6±0.07) were obtained under dry conditions, in good agreement with previous measurements. The high Q-factor of the second bending mode of the cantilever increases the accuracy of the capacitive measurements while the low applied potentials minimize the likelihood of variation of the dielectric constants at high field strength and of damage from dielectric breakdown of air.

  17. Noninvasive determination of optical lever sensitivity in atomic force microscopy

    SciTech Connect

    Higgins, M.J.; Proksch, R.; Sader, J.E.; Polcik, M.; Mc Endoo, S.; Cleveland, J.P.; Jarvis, S.P.

    2006-01-15

    Atomic force microscopes typically require knowledge of the cantilever spring constant and optical lever sensitivity in order to accurately determine the force from the cantilever deflection. In this study, we investigate a technique to calibrate the optical lever sensitivity of rectangular cantilevers that does not require contact to be made with a surface. This noncontact approach utilizes the method of Sader et al. [Rev. Sci. Instrum. 70, 3967 (1999)] to calibrate the spring constant of the cantilever in combination with the equipartition theorem [J. L. Hutter and J. Bechhoefer, Rev. Sci. Instrum. 64, 1868 (1993)] to determine the optical lever sensitivity. A comparison is presented between sensitivity values obtained from conventional static mode force curves and those derived using this noncontact approach for a range of different cantilevers in air and liquid. These measurements indicate that the method offers a quick, alternative approach for the calibration of the optical lever sensitivity.

  18. Subatomic-scale force vector mapping above a Ge(001) dimer using bimodal atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Naitoh, Yoshitaka; Turanský, Robert; Brndiar, Ján; Li, Yan Jun; Štich, Ivan; Sugawara, Yasuhiro

    2017-07-01

    Probing physical quantities on the nanoscale that have directionality, such as magnetic moments, electric dipoles, or the force response of a surface, is essential for characterizing functionalized materials for nanotechnological device applications. Currently, such physical quantities are usually experimentally obtained as scalars. To investigate the physical properties of a surface on the nanoscale in depth, these properties must be measured as vectors. Here we demonstrate a three-force-component detection method, based on multi-frequency atomic force microscopy on the subatomic scale and apply it to a Ge(001)-c(4 × 2) surface. We probed the surface-normal and surface-parallel force components above the surface and their direction-dependent anisotropy and expressed them as a three-dimensional force vector distribution. Access to the atomic-scale force distribution on the surface will enable better understanding of nanoscale surface morphologies, chemical composition and reactions, probing nanostructures via atomic or molecular manipulation, and provide insights into the behaviour of nano-machines on substrates.

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

    PubMed

    Sweetman, Adam; Stannard, Andrew

    2014-01-01

    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.

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

    PubMed Central

    Stannard, Andrew

    2014-01-01

    Summary 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. PMID:24778964

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

    PubMed

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

    2007-06-01

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

  2. Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

    1988-01-01

    The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  3. Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

    1988-01-01

    The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  4. Method for characterizing nanoscale wear of atomic force microscope tips.

    PubMed

    Liu, Jingjing; Notbohm, Jacob K; Carpick, Robert W; Turner, Kevin T

    2010-07-27

    Atomic force microscopy (AFM) is a powerful tool for studying tribology (adhesion, friction, and lubrication) at the nanoscale and is emerging as a critical tool for nanomanufacturing. However, nanoscale wear is a key limitation of conventional AFM probes that are made of silicon and silicon nitride (SiNx). Here we present a method for systematically quantifying tip wear, which consists of sequential contact-mode AFM scans on ultrananocrystalline diamond surfaces with intermittent measurements of the tip properties using blind reconstruction, adhesion force measurements, and transmission electron microscopy (TEM). We demonstrate direct measurement of volume loss over the wear test and agreement between blind reconstruction and TEM imaging. The geometries of various types of tips were monitored over a scanning distance of approximately 100 mm. The results show multiple failure mechanisms for different materials, including nanoscale fracture of a monolithic Si tip upon initial engagement with the surface, film failure of a SiNx-coated Si tip, and gradual, progressive wear of monolithic SiNx tips consistent with atom-by-atom attrition. Overall, the method provides a quantitative and systematic process for examining tip degradation and nanoscale wear, and the experimental results illustrate the multiple mechanisms that may lead to tip failure.

  5. Discriminating short-range from van der Waals forces using total force data in noncontact atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kuhn, Stefan; Rahe, Philipp

    2014-06-01

    Noncontact atomic force microscopy (NC-AFM) features the measurement of forces with highest spatial resolution and sensitivity, resolving forces of the order of pico-Newtons with submolecular resolution. However, the measured total force is a mixture composed of various interactions. While some interactions such as electrostatic or magnetic forces can be excluded by a careful design of the experiment, the subtraction of van der Waals forces, which mainly originate from London dispersion interactions between the macroscopic tip shank and the bulk sample, remains a challenge. We present the determination of the inherently present van der Waals forces in total interaction force data from fitting a suitable model, allowing for extraction of the short-range force component. We compare the applicability of several van der Waals models based on experimental interaction data from the calcite(101¯4) surface. The feasibility to fit these models to experimental data is critically discussed. We furthermore introduce criteria to assess the transition point from pure long-range interaction to mixed short- and long-range forces based on the variance of lateral and vertical force data. This determination allows us to extract the short-range interaction forces, which remained a challenge so far in NC-AFM experiments.

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

    PubMed

    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.

  7. Preparation of DOPC and DPPC Supported Planar Lipid Bilayers for Atomic Force Microscopy and Atomic Force Spectroscopy

    PubMed Central

    Attwood, Simon J.; Choi, Youngjik; Leonenko, Zoya

    2013-01-01

    Cell membranes are typically very complex, consisting of a multitude of different lipids and proteins. Supported lipid bilayers are widely used as model systems to study biological membranes. Atomic force microscopy and force spectroscopy techniques are nanoscale methods that are successfully used to study supported lipid bilayers. These methods, especially force spectroscopy, require the reliable preparation of supported lipid bilayers with extended coverage. The unreliability and a lack of a complete understanding of the vesicle fusion process though have held back progress in this promising field. We document here robust protocols for the formation of fluid phase DOPC and gel phase DPPC bilayers on mica. Insights into the most crucial experimental parameters and a comparison between DOPC and DPPC preparation are presented. Finally, we demonstrate force spectroscopy measurements on DOPC surfaces and measure rupture forces and bilayer depths that agree well with X-ray diffraction data. We also believe our approach to decomposing the force-distance curves into depth sub-components provides a more reliable method for characterising the depth of fluid phase lipid bilayers, particularly in comparison with typical image analysis approaches. PMID:23389046

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Molecular dynamics simulation of amplitude modulation atomic force microscopy.

    PubMed

    Hu, Xiaoli; Egberts, Philip; Dong, Yalin; Martini, Ashlie

    2015-06-12

    Molecular dynamics (MD) simulations were used to model amplitude modulation atomic force microscopy (AM-AFM). In this novel simulation, the model AFM tip responds to both tip-substrate interactions and to a sinusoidal excitation signal. The amplitude and phase shift of the tip oscillation observed in the simulation and their variation with tip-sample distance were found to be consistent with previously reported trends from experiments and theory. These simulation results were also fit to an expression enabling estimation of the energy dissipation, which was found to be smaller than that in a corresponding experiment. The difference was analyzed in terms of the effects of tip size and substrate thickness. Development of this model is the first step toward using MD to gain insight into the atomic-scale phenomena that occur during an AM-AFM measurement.

  10. Application of atomic force microscopy in bacterial research.

    PubMed

    Dorobantu, Loredana S; Gray, Murray R

    2010-01-01

    The atomic force microscope (AFM) has evolved from an imaging device into a multifunctional and powerful toolkit for probing the nanostructures and surface components on the exterior of bacterial cells. Currently, the area of application spans a broad range of interesting fields from materials sciences, in which AFM has been used to deposit patterns of thiol-functionalized molecules onto gold substrates, to biological sciences, in which AFM has been employed to study the undesirable bacterial adhesion to implants and catheters or the essential bacterial adhesion to contaminated soil or aquifers. The unique attribute of AFM is the ability to image bacterial surface features, to measure interaction forces of functionalized probes with these features, and to manipulate these features, for example, by measuring elongation forces under physiological conditions and at high lateral resolution (<1 A). The first imaging studies showed the morphology of various biomolecules followed by rapid progress in visualizing whole bacterial cells. The AFM technique gradually developed into a lab-on-a-tip allowing more quantitative analysis of bacterial samples in aqueous liquids and non-contact modes. Recently, force spectroscopy modes, such as chemical force microscopy, single-cell force spectroscopy, and single-molecule force spectroscopy, have been used to map the spatial arrangement of chemical groups and electrical charges on bacterial surfaces, to measure cell-cell interactions, and to stretch biomolecules. In this review, we present the fascinating options offered by the rapid advances in AFM with emphasizes on bacterial research and provide a background for the exciting research articles to follow. 2010 Wiley Periodicals, Inc.

  11. Atomic-scale sharpening of silicon tips in noncontact atomic force microscopy.

    PubMed

    Caciuc, V; Hölscher, H; Blügel, S; Fuchs, H

    2006-01-13

    The atomic-scale stability of clean silicon tips used in noncontact atomic force microscopy (NC-AFM) is simulated by ab initio calculations based on density functional theory. The tip structures are modeled by silicon clusters with and termination. For the often assumed Si(111)-type tip we observe the sharpening of the initially blunt tip via short-range chemical forces during the first approach and retraction cycle. The structural changes corresponding to this intrinsic process are irreversible and lead to stable NC-AFM imaging conditions. In opposition to the picture used in literature, the Si(001)-type tip does not exhibit the so-called "two-dangling bond" feature as a bulklike termination suggests.

  12. Applications of Atomic Force Microscopy in Macromolecular Crystal Growth

    NASA Astrophysics Data System (ADS)

    McPherson, Alexander

    1997-03-01

    A series of protein and virus crystals was investigated, in situ, using atomic force microscopy. Most of the crystals grew principally on steps generated by two dimensional nucleation on surfaces, though some, such as canavalin, grew by development of spiral dislocations. Apoferritin grew by a rarely encountered mechanism, normal growth, usually associated only with melt or vapor phase crystallization. Cubic crystals of satellite tobacco mosaic virus (STMV) grew, at moderate to high levels of supersaturation, by the direct addition of three- dimensional nuclei followed by their rapid normal growth and lateral expansion, a mechanism not previously described to promote controlled and reproducible crystal growth from solutions. Biological macromolecules apparently utilize a more diverse range of growth mechanisms in their crystallization than any previously studied material. High resolution AFM analyses have allowed us to record the first, real time, in situ atomic force microscope images, on the nanometer scale, of the incorporation of molecules into the growth steps of crystals grown from solution. The molecular structure of the growth step edge and surface layer on the (101) faces of tetragonal thaumatin crystals were resolved. It was shown that, although the growth step height corresponds to the unit cell containing eight thaumatin molecules, its advancement occurs by the addition of individual protein molecules rather than molecular clusters. Models for the packing of molecules on the surface layer, and of the structure of the step edge were developed which agree well with experimental data. Again, using high resolution, in situ atomic force microscopy, the initial stages of the formation and development of two- and three-dimensional nuclei on the surface of protein crystals were recorded. From these we conclude that non crystalline aggregates, with short range order, present both on the crystal-solution interface, and in the volume of the solution, give rise to

  13. Digital force-feedback for protein unfolding experiments using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Bippes, Christian A.; Janovjak, Harald; Kedrov, Alexej; Muller, Daniel J.

    2007-01-01

    Since its invention in the 1990s single-molecule force spectroscopy has been increasingly applied to study protein (un-)folding, cell adhesion, and ligand-receptor interactions. In most force spectroscopy studies, the cantilever of an atomic force microscope (AFM) is separated from a surface at a constant velocity, thus applying an increasing force to folded bio-molecules or bio-molecular bonds. Recently, Fernandez and co-workers introduced the so-called force-clamp technique. Single proteins were subjected to a defined constant force allowing their life times and life time distributions to be directly measured. Up to now, the force-clamping was performed by analogue PID controllers, which require complex additional hardware and might make it difficult to combine the force-feedback with other modes such as constant velocity. These points may be limiting the applicability and versatility of this technique. Here we present a simple, fast, and all-digital (software-based) PID controller that yields response times of a few milliseconds in combination with a commercial AFM. We demonstrate the performance of our feedback loop by force-clamp unfolding of single Ig27 domains of titin and the membrane proteins bacteriorhodopsin (BR) and the sodium/proton antiporter NhaA.

  14. Measuring Force-Induced Dissociation Kinetics of Protein Complexes Using Single-Molecule Atomic Force Microscopy.

    PubMed

    Manibog, K; Yen, C F; Sivasankar, S

    2017-01-01

    Proteins respond to mechanical force by undergoing conformational changes and altering the kinetics of their interactions. However, the biophysical relationship between mechanical force and the lifetime of protein complexes is not completely understood. In this chapter, we provide a step-by-step tutorial on characterizing the force-dependent regulation of protein interactions using in vitro and in vivo single-molecule force clamp measurements with an atomic force microscope (AFM). While we focus on the force-induced dissociation of E-cadherins, a critical cell-cell adhesion protein, the approaches described here can be readily adapted to study other protein complexes. We begin this chapter by providing a brief overview of theoretical models that describe force-dependent kinetics of biomolecular interactions. Next, we present step-by-step methods for measuring the response of single receptor-ligand bonds to tensile force in vitro. Finally, we describe methods for quantifying the mechanical response of single protein complexes on the surface of living cells. We describe general protocols for conducting such measurements, including sample preparation, AFM force clamp measurements, and data analysis. We also highlight critical limitations in current technologies and discuss solutions to these challenges. © 2017 Elsevier Inc. All rights reserved.

  15. CO tip functionalization in subatomic resolution atomic force microscopy

    SciTech Connect

    Kim, Minjung; Chelikowsky, James R.

    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.

  16. Visualizing water molecule distribution by atomic force microscopy.

    PubMed

    Kimura, Kenjiro; Ido, Shinichiro; Oyabu, Noriaki; Kobayashi, Kei; Hirata, Yoshiki; Imai, Takashi; Yamada, Hirofumi

    2010-05-21

    Hydration structures at biomolecular surfaces are essential for understanding the mechanisms of the various biofunctions and stability of biomolecules. Here, we demonstrate the measurement of local hydration structures using an atomic force microscopy system equipped with a low-noise deflection sensor. We applied this method to the analysis of the muscovite mica/water interface and succeeded in visualizing a hydration structure that is site-specific on a crystal. Furthermore, at the biomolecule/buffer solution interface, we found surface hydration layers that are more packed than those at the muscovite mica/water interface.

  17. Thermal calibration of photodiode sensitivity for atomic force microscopy

    SciTech Connect

    Attard, Phil; Pettersson, Torbjoern; Rutland, Mark W.

    2006-11-15

    The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.

  18. Atomic force microscopy of lead iodide crystal surfaces

    NASA Astrophysics Data System (ADS)

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

    1994-03-01

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

  19. Electrochemical atomic force microscopy: In situ monitoring of electrochemical processes

    NASA Astrophysics Data System (ADS)

    Reggente, Melania; Passeri, Daniele; Rossi, Marco; Tamburri, Emanuela; Terranova, Maria Letizia

    2017-08-01

    The in-situ electrodeposition of polyaniline (PANI), one of the most attractive conducting polymers (CP), has been monitored performing electrochemical atomic force microscopy (EC-AFM) experiments. The electropolymerization of PANI on a Pt working electrode has been observed performing cyclic voltammetry experiments and controlling the evolution of current flowing through the electrode surface, together with a standard AFM image. The working principle and the potentialities of this emerging technique are briefly reviewed and factors limiting the studying of the in-situ electrosynthesis of organic compounds discussed.

  20. Chromatin Imaging with Time-Lapse Atomic Force Microscopy

    PubMed Central

    Lyubchenko, Yuri L.; Shlyakhtenko, Luda S.

    2016-01-01

    Time-lapse atomic force microscopy (AFM) is widely used for direct visualization of the nanoscale dynamics of various biological systems. The advent of high-speed AFM instrumentation made it possible to image the dynamics of proteins and protein-DNA complexes within millisecond time range. This chapter describes protocols for studies of structure and dynamics of nucleosomes with time-lapse AFM including the high-speed AFM instrument. The necessary specifics for the preparation of chromatin samples for imaging with AFM including the protocols for the surface preparation are provided. PMID:25827873

  1. Magnetostriction-driven cantilevers for dynamic atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Penedo, M.; Fernández-Martínez, I.; Costa-Krämer, J. L.; Luna, M.; Briones, F.

    2009-10-01

    An actuation mode is presented to drive the mechanical oscillation of cantilevers for dynamic atomic force microscopy. The method is based on direct mechanical excitation of the cantilevers coated with amorphous Fe-B-N thin films, by means of the film magnetostriction, i.e., the dimensional change in the film when magnetized. These amorphous magnetostrictive Fe-B-N thin films exhibit soft magnetic properties, excellent corrosion resistance in liquid environments, nearly zero accumulated stress when properly deposited, and good chemical stability. We present low noise and high resolution topographic images acquired in liquid environment to demonstrate the method capability.

  2. Nanoindentation of Pseudomonas aeruginosa bacterial biofilm using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Baniasadi, Mahmoud; Xu, Zhe; Gandee, Leah; Du, Yingjie; Lu, Hongbing; Zimmern, Philippe; Minary-Jolandan, Majid

    2014-12-01

    Bacterial biofilms are a source of many chronic infections. Biofilms and their inherent resistance to antibiotics are attributable to a range of health issues including affecting prosthetic implants, hospital-acquired infections, and wound infection. Mechanical properties of biofilm, in particular, at micro- and nano-scales, are governed by microstructures and porosity of the biofilm, which in turn may contribute to their inherent antibiotic resistance. We utilize atomic force microscopy (AFM)-based nanoindentation and finite element simulation to investigate the nanoscale mechanical properties of Pseudomonas aeruginosa bacterial biofilm. This biofilm was derived from human samples and represents a medically relevant model.

  3. Understanding the plasmonics of nanostructured atomic force microscopy tips

    NASA Astrophysics Data System (ADS)

    Sanders, A.; Bowman, R. W.; Zhang, L.; Turek, V.; Sigle, D. O.; Lombardi, A.; Weller, L.; Baumberg, J. J.

    2016-10-01

    Structured metallic tips are increasingly important for optical spectroscopies such as tip-enhanced Raman spectroscopy, 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 the 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Atomic force microscopy of electrospun organic-inorganic lipid nanofibers

    NASA Astrophysics Data System (ADS)

    Zhang, Jinhong; Cohn, Celine; Qiu, Weiguo; Zha, Zhengbao; Dai, Zhifei; Wu, Xiaoyi

    2011-09-01

    An organic-inorganic hybridization strategy has been proposed to synthesize polymerizable lipid-based materials for the creation of highly stable lipid-mimetic nanostructures. We employ atomic force microscopy (AFM) to analyze the surface morphology and mechanical property of electrospun cholesteryl-succinyl silane (CSS) nanofibers. The AFM nanoindentation of the CSS nanofibers reveals elastic moduli of 55.3 ± 27.6 to 70.8 ± 35 MPa, which is significantly higher than the moduli of natural phospholipids and cholesterols. The study shows that organic-inorganic hybridization is useful in the design of highly stable lipid-based materials.

  6. Atomic force microscopy combined with optical microscopy for cells investigation.

    PubMed

    Cascione, Mariafrancesca; de Matteis, Valeria; Rinaldi, Rosaria; Leporatti, Stefano

    2017-01-01

    This review reports on the combined use of the atomic force microscopy (AFM) and several type of optical/fluorescence/laser scanning microscopy for investigating cells. It is shown that the hybrid systems of AFM with optical-derived microscopies enable to study in detail cell surface properties (such as topography), their mechanical properties (e.g., Young's modulus) mechanotransduction phenomena and allow to gain insight into biological-related pathways and mechanisms in the complex nanoworld of cells. Microsc. Res. Tech. 80:109-123, 2017. © 2016 Wiley Periodicals, Inc.

  7. Atomic force microscopy probing in the measurement of cell mechanics

    PubMed Central

    Kirmizis, Dimitrios; Logothetidis, Stergios

    2010-01-01

    Atomic force microscope (AFM) has been used incrementally over the last decade in cell biology. Beyond its usefulness in high resolution imaging, AFM also has unique capabilities for probing the viscoelastic properties of living cells in culture and, even more, mapping the spatial distribution of cell mechanical properties, providing thus an indirect indicator of the structure and function of the underlying cytoskeleton and cell organelles. AFM measurements have boosted our understanding of cell mechanics in normal and diseased states and provide future potential in the study of disease pathophysiology and in the establishment of novel diagnostic and treatment options. PMID:20463929

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Digital atomic force microscope moiré method.

    PubMed

    Liu, Chia-Ming; Chen, Lien-Wen

    2004-11-01

    In this study, a novel digital atomic force microscope (AFM) moiré method is established to measure the displacement and strain fields. The moiré pattern is generated by the interference between the specimen grating and the virtual reference grating formed by digital image processes. The overlapped image is filtered by the 2-D wavelet transformation to obtain clear interference moiré patterns. From moiré patterns, the displacement and strain fields can be analyzed. The experimental results show that the digital AFM moiré method is very sensitive and easy to realize in nanoscale measurements.

  10. Two-axis probing system for atomic force microscopy.

    PubMed

    Jayanth, G R; Jhiang, Sissy M; Menq, Chia-Hsiang

    2008-02-01

    A novel two-axis probing system is proposed for multiaxis atomic force microscopy (AFM). It employs a compliant manipulator that is optimally designed in terms of geometries and kinematics, and is actuated by multiple magnetic actuators to simultaneously control tip position and change tip orientation to achieve greater accessibility of the sample surface when imaging surfaces having large geometric variations. It leads to the creation of a multiaxis AFM system, which is a three-dimensional surface tool rather than a two-dimensional planar surface tool. The use of the system to scan the bottom corner of a grating step is reported.

  11. A Compact Vertical Scanner for Atomic Force Microscopes

    PubMed Central

    Park, Jae Hong; Shim, Jaesool; Lee, Dong-Yeon

    2010-01-01

    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. PMID:22163492

  12. A compact vertical scanner for atomic force microscopes.

    PubMed

    Park, Jae Hong; Shim, Jaesool; Lee, Dong-Yeon

    2010-01-01

    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.

  13. Interpreting motion and force for narrow-band intermodulation atomic force microscopy.

    PubMed

    Platz, Daniel; Forchheimer, Daniel; Tholén, Erik A; Haviland, David B

    2013-01-01

    Intermodulation atomic force microscopy (ImAFM) is a mode of dynamic atomic force microscopy that probes the nonlinear tip-surface force by measurement of the mixing of multiple modes in a frequency comb. A high-quality factor cantilever resonance and a suitable drive comb will result in tip motion described by a narrow-band frequency comb. We show, by a separation of time scales, that such motion is equivalent to rapid oscillations at the cantilever resonance with a slow amplitude and phase or frequency modulation. With this time-domain perspective, we analyze single oscillation cycles in ImAFM to extract the Fourier components of the tip-surface force that are in-phase with the tip motion (F(I)) and quadrature to the motion (F(Q)). Traditionally, these force components have been considered as a function of the static-probe height only. Here we show that F(I) and F(Q) actually depend on both static-probe height and oscillation amplitude. We demonstrate on simulated data how to reconstruct the amplitude dependence of F(I) and F(Q) from a single ImAFM measurement. Furthermore, we introduce ImAFM approach measurements with which we reconstruct the full amplitude and probe-height dependence of the force components F(I) and F(Q), providing deeper insight into the tip-surface interaction. We demonstrate the capabilities of ImAFM approach measurements on a polystyrene polymer surface.

  14. Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

    1986-01-01

    The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  15. Atomic force microscopy: From red blood cells to immunohaematology.

    PubMed

    Yeow, Natasha; Tabor, Rico F; Garnier, Gil

    2017-05-11

    Atomic force microscopy (AFM) offers complementary imaging modes that can provide morphological and structural details of red blood cells (RBCs), and characterize interactions between specific biomolecules and RBC surface antigen. This review describes the applications of AFM in determining RBC health by the observation of cell morphology, elasticity and surface roughness. Measurement of interaction forces between plasma proteins and antibodies against RBC surface antigen using the AFM also brought new information to the immunohaematology field. With constant improvisation of the AFM in resolution and imaging time, the reaction of RBC to changes in the physico-chemistry of its environment and the presence of RBC surface antigen specific-biomolecules is achievable. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Atomic force microscopic observation of surface-supported human erythrocytes

    NASA Astrophysics Data System (ADS)

    Ho, Mon-Shu; Kuo, Feng-Jia; Lee, Yu-Siang; Cheng, Chao-Min

    2007-07-01

    The nanomechanical characteristics of the membrane cytoskeleton of human erythrocytes were studied using atomic force microscopy (AFM). The self-assembly, fine structure, cell diameter, thickness, and reticulate cytoskeleton of erythrocytes on the mica surface were investigated. The adhesive forces that correspond to the membrane elasticity of various parts of the erythrocyte membrane surface were measured directly by AFM to be 0.64±0.14nN for cell indentation, 4.2±0.7nN for cell hump, and 11.5nN for side waist, respectively. The deformation of erythrocytes was discussed. Standing waves on the membrane that were set up by increased AFM amplitude were observed. The propagating velocity on the erythrocyte membrane was estimated to be ˜2.02×10-2m/s. Liquid physiological conditions were considered throughout.

  17. Mechanical properties of biological specimens explored by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kasas, S.; Longo, G.; Dietler, G.

    2013-04-01

    The atomic force microscope is a widely used surface scanning apparatus capable of reconstructing at a nanometric scale resolution the 3D morphology of biological samples. Due to its unique sensitivity, it is now increasingly used as a force sensor, to characterize the mechanical properties of specimens with a similar lateral resolution. This unique capability has produced, in the last years, a vast increase in the number of groups that have exploited the versatility and sensitivity of the instrument to explore the nanomechanics of various samples in the fields of biology, microbiology and medicine. In this review we outline the state of the art in this field, reporting the most interesting recent works involving the exploration of the nanomechanical properties of various biological samples.

  18. Introduction to atomic force microscopy (AFM) in biology.

    PubMed

    Goldsbury, Claire S; Scheuring, Simon; Kreplak, Laurent

    2009-11-01

    The atomic force microscope (AFM) has the unique capability of imaging biological samples with molecular resolution in buffer solution. 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 nanoscale to the microscale. 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.

  19. Cautions to predicate multiferroic by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Liu, Chen; Ma, Jing; Ma, Ji; Zhang, Yujun; Chen, Jiahui; Nan, Ce-Wen

    2017-05-01

    With the ever-increasing research activities in multiferroic driven by its profound physics and enormous potential for application, magnetic force microscopy (MFM), as a variety of atomic force microscope (AFM), has been brought to investigate the magnetic properties and the voltage controlled magnetism, especially in thin films and heterostructures. Here by taking a representative multiferroic system BiFeO3/La0.67Sr0.33MnO3 heterostructure and a ferroelectric PMN-PT single crystal for examples, we demonstrated that the MFM image is prone to be seriously interfered by the electrostatic interaction between the tip and sample surface, and misleads the predication of multiferroic. Assisted by the scanning Kelvin probe microscopy (SKPM), the origin and mechanism were discussed and an effective solution was proposed.

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

    PubMed

    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.

  1. Combined low-temperature scanning tunneling/atomic force microscope for atomic resolution imaging and site-specific force spectroscopy

    SciTech Connect

    Schwarz, Udo; Albers, Boris J.; Liebmann, Marcus; Schwendemann, Todd C.; Baykara, Mehmet Z.; Heyde, Markus; Salmeron, Miquel; Altman, Eric I.; Schwarz, Udo D.

    2008-02-27

    The authors present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope's performance.

  2. Combined low-temperature scanning tunneling/atomic force microscope for atomic resolution imaging and site-specific force spectroscopy.

    PubMed

    Albers, Boris J; Liebmann, Marcus; Schwendemann, Todd C; Baykara, Mehmet Z; Heyde, Markus; Salmeron, Miquel; Altman, Eric I; Schwarz, Udo D

    2008-03-01

    We present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope's performance.

  3. Force measurements with the atomic force microscope: Technique, interpretation and applications

    NASA Astrophysics Data System (ADS)

    Butt, Hans-Jürgen; Cappella, Brunero; Kappl, Michael

    2005-10-01

    The atomic force microscope (AFM) is not only a tool to image the topography of solid surfaces at high resolution. It can also be used to measure force-versus-distance curves. Such curves, briefly called force curves, provide valuable information on local material properties such as elasticity, hardness, Hamaker constant, adhesion and surface charge densities. For this reason the measurement of force curves has become essential in different fields of research such as surface science, materials engineering, and biology. Another application is the analysis of surface forces per se. Some of the most fundamental questions in colloid and surface science can be addressed directly with the AFM: What are the interactions between particles in a liquid? How can a dispersion be stabilized? How do surfaces in general and particles in particular adhere to each other? Particles and surfaces interactions have major implications for friction and lubrication. Force measurements on single molecules involving the rupture of single chemical bonds and the stretching of polymer chains have almost become routine. The structure and properties of confined liquids can be addressed since force measurements provide information on the energy of a confined liquid film. After the review of Cappella [B. Cappella, G. Dietler, Surf. Sci. Rep. 34 (1999) 1-104] 6 years of intense development have occurred. In 1999, the AFM was used only by experts to do force measurements. Now, force curves are used by many AFM researchers to characterize materials and single molecules. The technique and our understanding of surface forces has reached a new level of maturity. In this review we describe the technique of AFM force measurements. Important experimental issues such as the determination of the spring constant and of the tip radius are discussed. Current state of the art in analyzing force curves obtained under different conditions is presented. Possibilities, perspectives but also open questions and

  4. Atomic force microscopy for university students: applications in biomaterials

    NASA Astrophysics Data System (ADS)

    Kontomaris, S. V.; Stylianou, A.

    2017-05-01

    Atomic force microscopy (AFM) is a powerful tool used in the investigation of the structural and mechanical properties of a wide range of materials including biomaterials. It provides the ability to acquire high resolution images of biomaterials at the nanoscale. It also provides information about the response of specific areas under controlled applied force, which leads to the mechanical characterization of the sample at the nanoscale. The wide range of information provided by AFM has established it as a powerful research tool. In this paper, we present a general overview of the basic operation and functions of AFM applications in biomaterials. The basic operation of AFM is explained in detail with a focus on the real interactions that take place at the nanoscale level during imaging. AFM’s ability to provide the mechanical characterization (force curves) of specific areas at the nanoscale is also explained. The basic models of applied mechanics that are used for processing the data obtained by the force curves are presented. The aim of this paper is to provide university students and young scientists in the fields of biophysics and nanotechnology with a better understanding of AFM.

  5. Stretching of Single Polymer Chains Using the Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Ortiz, C.; van der Vegte, E. W.; van Swieten, E.; Robillard, G. T.; Hadziioannou, G.

    1998-03-01

    A variety of macroscopic phenomenon involve "nanoscale" polymer deformation including rubber elasticity, shear yielding, strain hardening, stress relaxation, fracture, and flow. With the advent of new and improved experimental techniques, such as the atomic force microscope (AFM), the probing of physical properties of polymers has reached finer and finer scales. The development of mixed self-assembling monolayer techniques and the chemical functionalization of AFM probe tips has allowed for mechanical experiments on single polymer chains of molecular dimensions. In our experiments, mixed monolayers are prepared in which end-functionalized, flexible polymer chains of thiol-terminated poly(methacrylic acid) are covalently bonded, isolated, and randomly distributed on gold substrates. The coils are then imaged, tethered to a gold-coated AFM tip, and stretched between the tip and the substrate in a conventional force / distance experiment. An increase in the attractive force due to entropic, elastic resistance to stretching, as well as fracture of the polymer chain is observed. The effect of chain stiffness, topological constraints, strain rate, mechanical hysteresis, and stress relaxation were investigated. Force modulation techniques were also employed in order to image the viscoelastic character of the polymer chains. Parallel work includes similar studies of biological systems such as wheat gluten proteins and polypeptides.

  6. Three-dimensional atomic force microscopy: interaction force vector by direct observation of tip trajectory.

    PubMed

    Sigdel, Krishna P; Grayer, Justin S; King, Gavin M

    2013-11-13

    The prospect of a robust three-dimensional atomic force microscope (AFM) holds significant promise in nanoscience. Yet, in conventional AFM, the tip-sample interaction force vector is not directly accessible. We scatter a focused laser directly off an AFM tip apex to rapidly and precisely measure the tapping tip trajectory in three-dimensional space. This data also yields three-dimensional cantilever spring constants, effective masses, and hence, the tip-sample interaction force components via Newton's second law. Significant lateral forces representing 49 and 13% of the normal force (Fz = 152 ± 17 pN) were observed in common tapping mode conditions as a silicon tip intermittently contacted a glass substrate in aqueous solution; as a consequence, the direction of the force vector tilted considerably more than expected. When addressing the surface of a lipid bilayer, the behavior of the force components differed significantly from that observed on glass. This is attributed to the lateral mobility of the lipid membrane coupled with its elastic properties. Direct access to interaction components Fx, Fy, and Fz provides a more complete view of tip dynamics that underlie force microscope operation and can form the foundation of a three-dimensional AFM in a plurality of conditions.

  7. Atomic force microscopy force-distance curves with small amplitude ultrasonic modulation.

    PubMed

    Ma, Chengfu; Chen, Yuhang; Wang, Tian; Chu, Jiaru

    2015-01-01

    Force-distance curves were acquired on a highly oriented pyrolytic graphite (HOPG) specimen and a gold film specimen under ultrasonic modulation in atomic force microscopy (AFM). Measurements demonstrated that small amplitude ultrasonic oscillation of either the cantilever or the sample has significant impacts on the characteristics of force-distance curves. With the increase of excitation amplitude, the apparent pull-off force decreased gradually and the hysteresis between the approach and retraction curves reduced significantly. Furthermore, the decrease of the pull-off force was determined to be also relevant to the excitation frequency. With the assistance of contact resonance spectra, the pull-off force was verified to have a near-linear relationship with the cantilever contact oscillation amplitude. Theoretical analysis and subsequent numerical simulations well interpreted the experimental results. The emergence of large oscillating contact forces under ultrasonic modulation altered the force-distance curves, and such a mechanism was ascertained by further ultrasonic AFM imaging. © Wiley Periodicals, Inc.

  8. β-connectin studies by small-angle x-ray scattering and single-molecule force spectroscopy by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Marchetti, S.; Sbrana, F.; Toscano, A.; Fratini, E.; Carlà, M.; Vassalli, M.; Tiribilli, B.; Pacini, A.; Gambi, C. M. C.

    2011-05-01

    The three-dimensional structure and the mechanical properties of a β-connectin fragment from human cardiac muscle, belonging to the I band, from I27 to I34, were investigated by small-angle x-ray scattering (SAXS) and single-molecule force spectroscopy (SMFS). This molecule presents an entropic elasticity behavior, associated to globular domain unfolding, that has been widely studied in the last 10 years. In addition, atomic force microscopy based SMFS experiments suggest that this molecule has an additional elastic regime, for low forces, probably associated to tertiary structure remodeling. From a structural point of view, this behavior is a mark of the fact that the eight domains in the I27-I34 fragment are not independent and they organize in solution, assuming a well-defined three-dimensional structure. This hypothesis has been confirmed by SAXS scattering, both on a diluted and a concentrated sample. Two different models were used to fit the SAXS curves: one assuming a globular shape and one corresponding to an elongated conformation, both coupled with a Coulomb repulsion potential to take into account the protein-protein interaction. Due to the predominance of the structure factor, the effective shape of the protein in solution could not be clearly disclosed. By performing SMFS by atomic force microscopy, mechanical unfolding properties were investigated. Typical sawtooth profiles were obtained and the rupture force of each unfolding domain was estimated. By fitting a wormlike chain model to each peak of the sawtooth profile, the entropic elasticity of octamer was described.

  9. {beta}-connectin studies by small-angle x-ray scattering and single-molecule force spectroscopy by atomic force microscopy

    SciTech Connect

    Marchetti, S.; Carla, M.; Gambi, C. M. C.; Sbrana, F.; Vassalli, M.; Toscano, A.; Pacini, A.; Fratini, E.; Tiribilli, B.

    2011-05-15

    The three-dimensional structure and the mechanical properties of a {beta}-connectin fragment from human cardiac muscle, belonging to the I band, from I{sub 27} to I{sub 34}, were investigated by small-angle x-ray scattering (SAXS) and single-molecule force spectroscopy (SMFS). This molecule presents an entropic elasticity behavior, associated to globular domain unfolding, that has been widely studied in the last 10 years. In addition, atomic force microscopy based SMFS experiments suggest that this molecule has an additional elastic regime, for low forces, probably associated to tertiary structure remodeling. From a structural point of view, this behavior is a mark of the fact that the eight domains in the I{sub 27}-I{sub 34} fragment are not independent and they organize in solution, assuming a well-defined three-dimensional structure. This hypothesis has been confirmed by SAXS scattering, both on a diluted and a concentrated sample. Two different models were used to fit the SAXS curves: one assuming a globular shape and one corresponding to an elongated conformation, both coupled with a Coulomb repulsion potential to take into account the protein-protein interaction. Due to the predominance of the structure factor, the effective shape of the protein in solution could not be clearly disclosed. By performing SMFS by atomic force microscopy, mechanical unfolding properties were investigated. Typical sawtooth profiles were obtained and the rupture force of each unfolding domain was estimated. By fitting a wormlike chain model to each peak of the sawtooth profile, the entropic elasticity of octamer was described.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Lower, Steven K

    2011-01-01

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

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

    PubMed

    Ortega-Esteban, A; Horcas, I; Hernando-Pérez, M; Ares, P; Pérez-Berná, A J; San Martín, C; Carrascosa, J L; de Pablo, P J; Gómez-Herrero, J

    2012-03-01

    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 (-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. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Easy and direct method for calibrating atomic force microscopy lateral force measurements

    PubMed Central

    Liu, Wenhua; Bonin, Keith; Guthold, Martin

    2010-01-01

    We have designed and tested a new, inexpensive, easy-to-make and easy-to-use calibration standard for atomic force microscopy (AFM) lateral force measurements. This new standard simply consists of a small glass fiber of known dimensions and Young’s modulus, which is fixed at one end to a substrate and which can be bent laterally with the AFM tip at the other end. This standard has equal or less error than the commonly used method of using beam mechanics to determine a cantilever’s lateral force constant. It is transferable, thus providing a universal tool for comparing the calibrations of different instruments. It does not require knowledge of the cantilever dimensions and composition or its tip height. This standard also allows direct conversion of the photodiode signal to force and, thus, circumvents the requirement for a sensor response (sensitivity) measurement. PMID:17614616

  14. Lateral force microscope calibration using a modified atomic force microscope cantilever

    SciTech Connect

    Reitsma, M. G.

    2007-10-15

    A proof-of-concept study is presented for a prototype atomic force microscope (AFM) cantilever and associated calibration procedure that provide a path for quantitative friction measurement using a lateral force microscope (LFM). The calibration procedure is based on the method proposed by Feiler et al. [Rev. Sci. Instrum. 71, 2746 (2000)] but allows for calibration and friction measurements to be carried out in situ and with greater precision. The modified AFM cantilever is equipped with lateral lever arms that facilitate the application of normal and lateral forces, comparable to those acting in a typical LFM friction experiment. The technique allows the user to select acceptable precision via a potentially unlimited number of calibration measurements across the full working range of the LFM photodetector. A microfabricated version of the cantilever would be compatible with typical commercial AFM instrumentation and allow for common AFM techniques such as topography imaging and other surface force measurements to be performed.

  15. Atomic-force-controlled capillary electrophoretic nanoprinting of proteins.

    PubMed

    Lovsky, Yulia; Lewis, Aaron; Sukenik, Chaim; Grushka, Eli

    2010-01-01

    The general nanoprinting and nanoinjection of proteins on non-conducting or conducting substrates with a high degree of control both in terms of positional and timing accuracy is an important goal that could impact diverse fields from biotechnology (protein chips) to molecular electronics and from fundamental studies in cell biology to nanophotonics. In this paper, we combine capillary electrophoresis (CE), a separation method with considerable control of protein movement, with the unparalleled positional accuracy of an atomic force microscope (AFM). This combination provides the ability to electrophoretically or electroosmotically correlate the timing of protein migration with AFM control of the protein deposition at a high concentration in defined locations and highly confined volumes estimated to be 2 al. Electrical control of bovine serum albumin printing on standard protein-spotting glass substrates is demonstrated. For this advance, fountain pen nanolithography (FPN) that uses cantilevered glass-tapered capillaries is amended with the placement of electrodes on the nanopipette itself. This results in imposed voltages that are three orders of magnitude less than what is normally used in capillary electrophoresis. The development of atomic-force-controlled capillary electrophoretic printing (ACCEP) has the potential for electrophoretic separation, with high resolution, both in time and in space. The large voltage drop at the tip of the tapered nanopipettes allows for significant increases in concentration of protein in the small printed volumes. All of these attributes combine to suggest that this methodology should have a significant impact in science and technology.

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

    PubMed

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

    2017-04-01

    Forensic science is a wide field comprising of several subspecialties and uses methods derived from natural sciences for finding criminals and other evidence valid in a legal court. A relatively new area; Nano-forensics brings a new era of investigation in forensic science in which instantaneous results can be produced that determine various agents such as explosive gasses, biological agents and residues in different crime scenes and terrorist activity investigations. This can be achieved by applying Nanotechnology and its associated characterization techniques in forensic sciences. Several characterization techniques exist in Nanotechnology and nano-analysis is one such technique that is used in forensic science which includes Electron microscopes (EM) like Transmission (TEM) and Scanning (SEM), Raman microscopy (Micro -Raman) and Scanning Probe Microscopes (SPMs) like Atomic Force Microscope (AFM). Atomic force microscopy enables surface characterization of different materials by examining their morphology and mechanical properties. Materials that are immeasurable such as hair, body fluids, textile fibers, documents, polymers, pressure sensitive adhesives (PSAs), etc. are often encountered during forensic investigations. This review article will mainly focus on the use of AFM in the examination of different evidence such as blood stains, forged documents, human hair samples, ammunitions, explosives, and other such applications in the field of Forensic Science. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    PubMed Central

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

    2016-01-01

    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 clinical surfactants currently used throughout the world, i.e., Survanta, Curosurf, Infasurf and BLES. These modified-natural surfactants are further compared to dipalmitoyl phosphatidylcholine (DPPC), a synthetic model surfactant of DPPC:palmitoyl-oleoyl phosphatidylglycerol (POPG) (7:3), and endogenous bovine natural surfactant. Atomic force microscopy reveals significant differences in the lateral structure and molecular organization of these surfactant preparations. These differences are discussed in terms of DPPC and cholesterol contents. We conclude that all animal-derived clinical surfactants assume a similar structure of multilayers of fluid phospholipids closely attached to an interfacial monolayer enriched in DPPC, at physiologically relevant surface pressures. This study provides the first comprehensive survey of the lateral structure of clinical surfactants at various surface pressures. It may have clinical implications on future application and development of surfactant preparations. PMID:21439262

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

    PubMed

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

    2011-07-01

    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 clinical surfactants currently used throughout the world, i.e., Survanta, Curosurf, Infasurf and BLES. These modified-natural surfactants are further compared to dipalmitoyl phosphatidylcholine (DPPC), a synthetic model surfactant of DPPC:palmitoyl-oleoyl phosphatidylglycerol (POPG) (7:3), and endogenous bovine natural surfactant. Atomic force microscopy reveals significant differences in the lateral structure and molecular organization of these surfactant preparations. These differences are discussed in terms of DPPC and cholesterol contents. We conclude that all animal-derived clinical surfactants assume a similar structure of multilayers of fluid phospholipids closely attached to an interfacial monolayer enriched in DPPC, at physiologically relevant surface pressures. This study provides the first comprehensive survey of the lateral structure of clinical surfactants at various surface pressures. It may have clinical implications on future application and development of surfactant preparations. Copyright © 2011 Elsevier B.V. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    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. High resolution atomic force microscopy of double-stranded RNA

    NASA Astrophysics Data System (ADS)

    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

  1. Mechanical characterization of porous nano-thin films by use of atomic force acoustic microscopy.

    PubMed

    Kopycinska-Müller, M; Clausner, A; Yeap, K-B; Köhler, B; Kuzeyeva, N; Mahajan, S; Savage, T; Zschech, E; Wolter, K-J

    2016-03-01

    The indentation modulus of thin films of porous organosilicate glass with a nominal porosity content of 30% and thicknesses of 350nm, 200nm, and 46nm is determined with help of atomic force acoustic microscopy (AFAM). This scanning probe microscopy based technique provides the highest possible depth resolution. The values of the indentation modulus obtained for the 350nm and 200nm thin films were respectively 6.3GPa±0.2GPa and 7.2GPa±0.2GPa and free of the substrate influence. The sample with the thickness of 46nm was tested in four independent measurement sets. Cantilevers with two different tip radii of about 150nm and less than 50nm were applied in different force ranges to obtain a result for the indentation modulus that was free of the substrate influence. A detailed data analysis yielded value of 8.3GPa±0.4GPa for the thinnest film. The values of the indentation modulus obtained for the thin films of porous organosilicate glasses increased with the decreasing film thickness. The stiffening observed for the porous films could be explained by evolution of the pore topology as a function of the film thickness. To ensure that our results were free of the substrate influence, we analyzed the ratio of the sample deformation as well as the tip radius to the film thickness. The results obtained for the substrate parameter were compared for all the measurement series and showed, which ones could be declared as free of the substrate influence.

  2. Significant improvements in stability and reproducibility of atomic-scale atomic force microscopy in liquid

    NASA Astrophysics Data System (ADS)

    Akrami, S. M. R.; Nakayachi, H.; Watanabe-Nakayama, T.; Asakawa, H.; Fukuma, T.

    2014-11-01

    Recent advancement of dynamic-mode atomic force microscopy (AFM) for liquid-environment applications enabled atomic-scale studies on various interfacial phenomena. However, instabilities and poor reproducibility of the measurements often prevent systematic studies. To solve this problem, we have investigated the effect of various tip treatment methods for atomic-scale imaging and force measurements in liquid. The tested methods include Si coating, Ar plasma, Ar sputtering and UV/O3 cleaning. We found that all the methods provide significant improvements in both the imaging and force measurements in spite of the tip transfer through the air. Among the methods, we found that the Si coating provides the best stability and reproducibility in the measurements. To understand the origin of the fouling resistance of the cleaned tip surface and the difference between the cleaning methods, we have investigated the tip surface properties by x-ray photoelectron spectroscopy and contact angle measurements. The results show that the contaminations adsorbed on the tip during the tip transfer through the air should desorb from the surface when it is immersed in aqueous solution due to the enhanced hydrophilicity by the tip treatments. The tip surface prepared by the Si coating is oxidized when it is immersed in aqueous solution. This creates local spots where stable hydration structures are formed. For the other methods, there is no active mechanism to create such local hydration sites. Thus, the hydration structure formed under the tip apex is not necessarily stable. These results reveal the desirable tip properties for atomic-scale AFM measurements in liquid, which should serve as a guideline for further improvements of the tip treatment methods.

  3. Hydrodynamic damping of tip oscillation in pulsed-force atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Chen, X.; Davies, M. C.; Roberts, C. J.; Tendler, S. J. B.; Williams, P. M.

    2000-11-01

    Although proven a powerful technique for mapping adhesion and surface mechanical properties at high lateral resolution, pulsed-force (PF) atomic force microscopy (AFM) is problematic in liquid, due to heavy hydrodynamic damping of cantilever vibration. We present computer simulations using the simple harmonic oscillation model to explore the changes of deflection signal profile that occur from air to liquid environment. In agreement with experimental results, we find that oscillation phase lag plays a key role in the signal profile. When imaging in liquid, the deflection caused by liquid oscillation may exceed that caused by tip-sample contact repulsion and adhesion, which brings particular consideration for PF-AFM imaging in liquid.

  4. Note: Electrical resolution during conductive atomic force microscopy measurements under different environmental conditions and contact forces

    SciTech Connect

    Lanza, M.; Porti, M.; Nafria, M.; Aymerich, X.; Whittaker, E.; Hamilton, B.

    2010-10-15

    Conductive atomic force microscopy experiments on gate dielectrics in air, nitrogen, and UHV have been compared to evaluate the impact of the environment on topography and electrical measurements. In current images, an increase of the lateral resolution and a reduction of the conductivity were observed in N{sub 2} and, especially, in UHV (where current depends also on the contact force). Both effects were related to the reduction/elimination of the water layer between the tip and the sample in N{sub 2}/UHV. Therefore, since current measurements are very sensitive to environmental conditions, these factors must be taken into consideration when comparisons between several experiments are performed.

  5. Robust high-resolution imaging and quantitative force measurement with tuned-oscillator atomic force microscopy.

    PubMed

    Dagdeviren, Omur E; Götzen, Jan; Hölscher, Hendrik; Altman, Eric I; Schwarz, Udo D

    2016-02-12

    Atomic force microscopy (AFM) and spectroscopy are based on locally detecting the interactions between a surface and a sharp probe tip. For highest resolution imaging, noncontact modes that avoid tip-sample contact are used; control of the tip's vertical position is accomplished by oscillating the tip and detecting perturbations induced by its interaction with the surface potential. Due to this potential's nonlinear nature, however, achieving reliable control of the tip-sample distance is challenging, so much so that despite its power vacuum-based noncontact AFM has remained a niche technique. Here we introduce a new pathway to distance control that prevents instabilities by externally tuning the oscillator's response characteristics. A major advantage of this operational scheme is that it delivers robust position control in both the attractive and repulsive regimes with only one feedback loop, thereby providing an easy-to-implement route to atomic resolution imaging and quantitative tip-sample interaction force measurement.

  6. Isoelectric point of fluorite by direct force measurements using atomic force microscopy.

    PubMed

    Assemi, Shoeleh; Nalaskowski, Jakub; Miller, Jan D; Johnson, William P

    2006-02-14

    Interaction forces between a fluorite (CaF2) surface and colloidal silica were measured by atomic force microscopy (AFM) in 1 x 10(-3) M NaNO3 at different pH values. Forces between the silica colloid and fluorite flat were measured at a range of pH values above the isoelectric point (IEP) of silica so that the forces were mainly controlled by the fluorite surface charge. In this way, the IEP of the fluorite surface was deduced from AFM force curves at pH approximately 9.2. Experimental force versus separation distance curves were in good agreement with theoretical predictions based on long-range electrostatic interactions, allowing the potential of the fluorite surface to be estimated from the experimental force curves. AFM-deduced surface potentials were generally lower than the published zeta potentials obtained from electrokinetic methods for powdered samples. Differences in methodology, orientation of the fluorite, surface carbonation, and equilibration time all could have contributed to this difference.

  7. Nanoscale Characterization and Determination of Adhesion Forces of Pseudomonas aeruginosa Pili by Using Atomic Force Microscopy

    PubMed Central

    Touhami, Ahmed; Jericho, Manfred H.; Boyd, Jessica M.; Beveridge, Terry J.

    2006-01-01

    Type IV pili play an important role in bacterial adhesion, motility, and biofilm formation. Here we present high-resolution atomic force microscopy (AFM) images of type IV pili from Pseudomonas aeruginosa bacteria. An individual pilus ranges in length from 0.5 to 7 μm and has a diameter from 4 to 6 nm, although often, pili bundles in which the individual filaments differed in both length and diameter were seen. By attaching bacteria to AFM tips, it was possible to fasten the bacteria to mica surfaces by pili tethers. Force spectra of tethered pili gave rupture forces of 95 pN. The slopes of force curves close to the rupture force were nearly linear but showed little variation with pilus length. Furthermore, force curves could not be fitted with wormlike-chain polymer stretch models when using realistic persistence lengths for pili. The observation that the slopes near rupture did not depend on the pili length suggests that they do not represent elastic properties of the pili. It is possible that this region of the force curves is determined by an elastic element that is part of the bacterial wall, although further experiments are needed to confirm this. PMID:16385026

  8. Probing physical properties at the nanoscale using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Ditzler, Lindsay Rachel

    Techniques that measure physical properties at the nanoscale with high sensitivity are significantly limited considering the number of new nanomaterials being developed. The development of atomic force microscopy (AFM) has lead to significant advancements in the ability to characterize physical properties of materials in all areas of science: chemistry, physics, engineering, and biology have made great scientific strides do to the versatility of the AFM. AFM is used for quantification of many physical properties such as morphology, electrical, mechanical, magnetic, electrochemical, binding interactions, and protein folding. This work examines the electrical and mechanical properties of materials applicable to the field of nano-electronics. As electronic devices are miniaturized the demand for materials with unique electrical properties, which can be developed and exploited, has increased. For example, discussed in this work, a derivative of tetrathiafulvalene, which exhibits a unique loss of conductivity upon compression of the self-assembled monolayer could be developed into a molecular switch. This work also compares tunable organic (tetraphenylethylene tetracarboxylic acid and bis(pyridine)s assemblies) and metal-organic (Silver-stilbizole coordination compounds) crystals which show high electrical conductivity. The electrical properties of these materials vary depending on their composition allowing for the development of compositionally tunable functional materials. Additional work was done to investigate the effects of molecular environment on redox active 11-ferroceneyl-1 undecanethiol (Fc) molecules. The redox process of mixed monolayers of Fc and decanethiol was measured using conductive probe atomic force microscopy and force spectroscopy. As the concentration of Fc increased large, variations in the force were observed. Using these variations the number of oxidized molecules in the monolayer was determined. AFM is additionally capable of investigating

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

    NASA Astrophysics Data System (ADS)

    Ooe, Hiroaki; Sakuishi, Tatsuya; Nogami, Makoto; Tomitori, Masahiko; Arai, Toyoko

    2014-07-01

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

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

    SciTech Connect

    Ooe, Hiroaki; Sakuishi, Tatsuya; Arai, Toyoko; Nogami, Makoto; Tomitori, Masahiko

    2014-07-28

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

  11. Quantitative Membrane Electrostatics with the Atomic Force Microscope

    PubMed Central

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

    2007-01-01

    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 of supported zwitterionic dioleoylphosphatidylcholine membranes with a variable fraction of anionic dioleoylphosphatidylserine. The resulting surface charge density and surface potential values are in quantitative agreement with those predicted by the Gouy-Chapman-Stern model of membrane charge regulation, but only when the numerical analysis is employed. In addition, we demonstrate that the AFM can detect double layer forces at a separation of several screening lengths, and that the probe only perturbs the membrane surface potential by <2%. Finally, we demonstrate 50-nm resolution electrostatic mapping on heterogeneous model membranes with the AFM. This novel combination of capabilities demonstrates that the AFM is a unique and powerful probe of membrane electrostatics. PMID:17158563

  12. Atomic force microscopy of asymmetric membranes from turtle erythrocytes.

    PubMed

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

    2014-08-01

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

  13. Multifunctional hydrogel nano-probes for atomic force microscopy

    PubMed Central

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

    2016-01-01

    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. PMID:27199165

  14. Investigating single molecule adhesion by atomic force spectroscopy.

    PubMed

    Stetter, Frank W S; Kienle, Sandra; Krysiak, Stefanie; Hugel, Thorsten

    2015-02-27

    Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

  15. Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

    PubMed Central

    Stetter, Frank W. S.; Kienle, Sandra; Krysiak, Stefanie; Hugel, Thorsten

    2015-01-01

    Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment. PMID:25867282

  16. Multifunctional hydrogel nano-probes for atomic force microscopy

    NASA Astrophysics Data System (ADS)

    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.

  17. Probing Single Membrane Proteins by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Scheuring, S.; Sapra, K. Tanuj; Müller, Daniel J.

    In this book chapter, we describe the working principle of the atomic force microscope (AFM), followed by the applications of AFM in high-resolution imaging and single-molecule force spectroscopy of membrane proteins. In the imaging mode, AFM allows observing the assembly of membrane proteins directly in native membranes approaching a resolution of ~0.5 nm with an outstanding signal-to-noise ratio. Conformational deviations of individual membrane proteins can be observed and their functional states directly imaged. Time-lapse AFM can image membrane proteins at work. In conjunction with high- resolution imaging, the use of the AFM as a single-molecule force spectroscope (SMFS) has gained tremendous importance in recent years. This combination allows to locate the inter- and intramolecular interactions of single membrane proteins. SMFS allows characterization of interactions that guide the folding of proteins and describe the parameters that lead to their destabilization, malfunction and misfolding. Moreover, it enables to measure the interactions established by ligand- and inhibitor-binding and in membrane protein assemblies. Because of its practical use in characterizing various parameters of membrane proteins in their native environment, AFM can be aptly described as a `lab on a tip' device.

  18. Atomic force microscopy as an advanced tool in neuroscience

    PubMed Central

    Jembrek, Maja Jazvinšćak; Šimić, Goran; Hof, Patrick R.; Šegota, Suzana

    2015-01-01

    This review highlights relevant issues about applications and improvements of atomic force microscopy (AFM) toward a better understanding of neurodegenerative changes at the molecular level with the hope of contributing to the development of effective therapeutic strategies for neurodegenerative illnesses. The basic principles of AFM are briefly discussed in terms of evaluation of experimental data, including the newest PeakForce Quantitative Nanomechanical Mapping (QNM) and the evaluation of Young’s modulus as the crucial elasticity parameter. AFM topography, revealed in imaging mode, can be used to monitor changes in live neurons over time, representing a valuable tool for high-resolution detection and monitoring of neuronal morphology. The mechanical properties of living cells can be quantified by force spectroscopy as well as by new AFM. A variety of applications are described, and their relevance for specific research areas discussed. In addition, imaging as well as non-imaging modes can provide specific information, not only about the structural and mechanical properties of neuronal membranes, but also on the cytoplasm, cell nucleus, and particularly cytoskeletal components. Moreover, new AFM is able to provide detailed insight into physical structure and biochemical interactions in both physiological and pathophysiological conditions. PMID:28123795

  19. Subharmonic Oscillations and Chaos in Dynamic Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Cantrell, Sean A.

    2015-01-01

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

  20. A new ion sensing deep atomic force microscope

    SciTech Connect

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

    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.

  1. The influence of chemical bonding configuration on atomic identification by force spectroscopy.

    PubMed

    Welker, Joachim; Weymouth, Alfred John; Giessibl, Franz J

    2013-08-27

    The force between two atoms depends not only on their chemical species and distance, but also on the configuration of their chemical bonds to other atoms. This strongly affects atomic force spectroscopy, in which the force between the tip of an atomic force microscope and a sample is measured as a function of distance. We show that the short-range forces between tip and sample atoms depend strongly on the configuration of the tip, to the point of preventing atom identification with a poorly defined tip. Our solution is to control the tip apex before using it for spectroscopy. We demonstrate a method by which a CO molecule on Cu can be used to characterize the tip. In combination with gentle pokes, this can be used to engineer a specific tip apex. This CO Front atom Identification (COFI) method allows us to use a well-defined tip to conduct force spectroscopy.

  2. Atomic force microscope manipulation of Ag atom on the Si(111) surface

    NASA Astrophysics Data System (ADS)

    Enkhtaivan, Batnyam; Oshiyama, Atsushi

    2017-01-01

    We present first-principles total-energy electronic-structure calculations that provide the microscopic mechanism of Ag atom diffusion between the half unit cells (HUCs) on the Si(111)-(7 ×7 ) surface with and without the tip of the atomic force microscope (AFM). We find that, without the presence of the AFM tip, there are three pathways of inter-HUC diffusion. The pathway, in which the diffusing atom passes over the nanohole of the surface, has the lowest energy barrier. The diffusion along this pathway between the two HUCs is almost symmetric with the energy barrier of about 0.8 eV in both directions. In the other two pathways, the adatom diffuses along the edge of the nanohole. The diffusion along these two pathways have an energy barrier of about 1 eV. With the presence of the tip, we find that the reaction pathways are essentially the same, but the diffusion along the edge of the nanohole has a lower energy barrier than the diffusion over the nanohole. Thus the diffusion channel is changed by the presence of the tip. In the diffusion along the edge of the nanohole, the energy barrier in one direction is substantially reduced to be 0.2-0.4 eV by the tip, while that of the diffusion in the reverse direction remains larger than 1 eV. The Si tip reduces the energy barrier more than the Pt tip due to the flexibility of the tip apex structure. In addition to the reduction of the barrier, the tip traps the diffusing adatom preventing diffusion in the reverse direction. Also we find that the shape of the tip apex structure is important for the adatom's trapping ability. The bond formation between the AFM tip atom and the surface adatom is essential for atom manipulation using the AFM tip. Our results show that atom manipulation is possible with both the metallic and semiconducting AFM tips.

  3. A combined experimental atomic force microscopy-based nanoindentation and computational modeling approach to unravel the key contributors to the time-dependent mechanical behavior of single cells.

    PubMed

    Florea, Cristina; Tanska, Petri; Mononen, Mika E; Qu, Chengjuan; Lammi, Mikko J; Laasanen, Mikko S; Korhonen, Rami K

    2017-02-01

    Cellular responses to mechanical stimuli are influenced by the mechanical properties of cells and the surrounding tissue matrix. Cells exhibit viscoelastic behavior in response to an applied stress. This has been attributed to fluid flow-dependent and flow-independent mechanisms. However, the particular mechanism that controls the local time-dependent behavior of cells is unknown. Here, a combined approach of experimental AFM nanoindentation with computational modeling is proposed, taking into account complex material behavior. Three constitutive models (porohyperelastic, viscohyperelastic, poroviscohyperelastic) in tandem with optimization algorithms were employed to capture the experimental stress relaxation data of chondrocytes at 5 % strain. The poroviscohyperelastic models with and without fluid flow allowed through the cell membrane provided excellent description of the experimental time-dependent cell responses (normalized mean squared error (NMSE) of 0.003 between the model and experiments). The viscohyperelastic model without fluid could not follow the entire experimental data that well (NMSE = 0.005), while the porohyperelastic model could not capture it at all (NMSE = 0.383). We also show by parametric analysis that the fluid flow has a small, but essential effect on the loading phase and short-term cell relaxation response, while the solid viscoelasticity controls the longer-term responses. We suggest that the local time-dependent cell mechanical response is determined by the combined effects of intrinsic viscoelasticity of the cytoskeleton and fluid flow redistribution in the cells, although the contribution of fluid flow is smaller when using a nanosized probe and moderate indentation rate. The present approach provides new insights into viscoelastic responses of chondrocytes, important for further understanding cell mechanobiological mechanisms in health and disease.

  4. Direct observation of dynamic force propagation between focal adhesions of cells on microposts by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Okada, Akinori; Mizutani, Yusuke; Subagyo, Agus; Hosoi, Hirotaka; Nakamura, Motonori; Sueoka, Kazuhisa; Kawahara, Koichi; Okajima, Takaharu

    2011-12-01

    We investigated dynamic force propagation between focal adhesions of fibroblast cells cultured on polydimethylsiloxane micropost substrates, by atomic force microscopy. Live cells were mechanically modulated by the atomic force microscopy probe bound to cell apical surfaces at 0.01-0.5 Hz, while microposts served as a force sensor at basal surfaces. We observed that cells exhibited rheological behavior at the apical surface but had no apparent out-of-phase response at the basal surface, indicating that the dynamic force propagating through cytoskeletal filaments behaves in an elastic manner. Moreover, the direction of the propagated force was observed to be intimately associated with the prestress.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  6. In situ generation and atomic scale imaging of slip traces with atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Oele, W. F.; Kerssemakers, J. W. J.; De Hosson, J. Th. M.

    1997-12-01

    We have designed, constructed, and tested a three-point bending system for in situ studies of slip in ionic crystals with an atomic force microscope (AFM). The work is aimed at developing a novel instrumental attachment for an in situ study of plastic deformation. The bending system is installed inside the optical head of the AFM on top of the piezoelectric scanner. Since the bending should not obstruct scanning, a piezocrystal is used for bending as well as an external stepper motor, which is connected with a screw in the bending system via a flexible shaft. The bending system performs over a relatively wide, continuous deflection range. The operation of the three-point bending system is illustrated by experiments on an ionic material in which the effect of macroscopic bending is demonstrated at an atomic scale.

  7. Analysis of intraocular lens surface adhesiveness by atomic force microscopy.

    PubMed

    Lombardo, Marco; Carbone, Giovanni; Lombardo, Giuseppe; De Santo, Maria P; Barberi, Riccardo

    2009-07-01

    To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microscopy (AFM). LiCryL Laboratory, University of Calabria, Rende, Italy. The surface adhesive properties of poly(methyl methacrylate) (PMMA), silicone, hydrophilic acrylic, and hydrophobic acrylic IOLs were evaluated by AFM. Analysis was performed at room temperature (21 degrees C) in a liquid environment using the force-versus-distance mode of a commercial instrument (NanoScope III). Measurements were acquired with rectangular silicon cantilevers of a nominal elastic constant of 10 Newton/m. The nominal value of the tip's radius of curvature was 1 mum, and the scanning speed during the acquisitions ranged from 10 to 400 nm/s. The adhesion force measurements showed different characteristics for the various types of IOLs (P<.001, analysis of variance). The hydrophobic acrylic IOL had the largest mean adhesive force (283.75 nanoNewton [nN] +/- 0.14 [SD]) followed by the hydrophilic acrylic (84.76 +/- 0.94 nN), PMMA (45.77 +/- 0.47 nN), and silicone (2.10 +/- 0.01 nN) IOLs. The surface properties of the biomaterials used to manufacture IOLs are important because they can influence the incidence and severity of posterior capsule opacification (PCO). Although further studies are necessary to elucidate the mechanism of PCO development and the interface interactions between the IOL and capsule, the results in this study may bolster the theory of manufacturing more-adhesive materials to prevent PCO.

  8. Primate lens capsule elasticity assessed using Atomic Force Microscopy

    PubMed Central

    Ziebarth, Noël M.; Arrieta, Esdras; Feuer, William J.; Moy, Vincent T.; Manns, Fabrice; Parel, Jean-Marie

    2011-01-01

    The purpose of this project is to measure the elasticity of the human and non-human primate lens capsule at the microscopic scale using Atomic Force Microscopy (AFM). Elasticity measurements were performed using AFM on the excised anterior lens capsule from 9 cynomolgus monkey (5.9–8.0 years), 8 hamadryas baboon (2.8–10.1 years), and 18 human lenses (33–79 years). Anterior capsule specimens were obtained by performing a 5mm continuous curvilinear capsulorhexis and collecting the resulting disk of capsular tissue. To remove the lens epithelial cells the specimen was soaked in 0.1% trypsin and 0.02% EDTA for five minutes, washed, and placed on a Petri dish and immersed in DMEM. Elasticity measurements of the capsule were performed with a laboratory-built AFM system custom designed for force measurements of ophthalmic tissues. The capsular specimens were probed with an AFM cantilever tip to produce force-indentation curves for each specimen. Young’s modulus was calculated from the force-indentation curves using the model of Sneddon for a conical indenter. Young’s modulus of elasticity was 20.1–131kPa for the human lens capsule, 9.19–117kPa for the cynomolgus lens capsule, and 13.1–62.4kPa for the baboon lens capsule. Young’s modulus increased significantly with age in humans (p=0.03). The age range of the monkey and baboon samples was not sufficient to justify an analysis of age dependence. The capsule elasticity of young humans (<45 years) was not statistically different from that of the monkey and baboon. In humans, there is an increase in lens capsule stiffness at the microscale that could be responsible for an increase in lens capsule bulk stiffness. PMID:21420953

  9. Lateral force calibration of an atomic force microscope with a diamagnetic levitation spring system

    SciTech Connect

    Li, Q.; Kim, K.-S.; Rydberg, A.

    2006-06-15

    A novel diamagnetic lateral force calibrator (D-LFC) has been developed to directly calibrate atomic force microscope (AFM) cantilever-tip or -bead assemblies. This enables an AFM to accurately measure the lateral forces encountered in friction or biomechanical-testing experiments at a small length scale. In the process of development, deformation characteristics of the AFM cantilever assemblies under frictional loading have been analyzed and four essential response variables, i.e., force constants, of the assembly have been identified. Calibration of the lateral force constant and the 'crosstalk' lateral force constant, among the four, provides the capability of measuring absolute AFM lateral forces. The D-LFC is composed of four NdFeB magnets and a diamagnetic pyrolytic graphite sheet, which can calibrate the two constants with an accuracy on the order of 0.1%. Preparation of the D-LFC and the data processing required to get the force constants is significantly simpler than any other calibration methods. The most up-to-date calibration technique, known as the 'wedge method', calibrates mainly one of the two constants and, if the crosstalk effect is properly analyzed, is primarily applicable to a sharp tip. In contrast, the D-LFC can calibrate both constants simultaneously for AFM tips or beads with any radius of curvature. These capabilities can extend the applicability of AFM lateral force measurement to studies of anisotropic multiscale friction processes and biomechanical behavior of cells and molecules under combined loading. Details of the D-LFC method as well as a comparison with the wedge method are provided in this article.

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Liu, Chih-Hao; Horng, Jim-Tong; Chang, Jeng-Shian; Hsieh, Chung-Fan; Tseng, You-Chen; Lin, Shiming

    2012-01-06

    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. Copyright © 2011 Elsevier Inc. All rights reserved.

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

    PubMed

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

    2013-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  16. The long range voice coil atomic force microscope

    PubMed Central

    Barnard, H.; Randall, C.; Bridges, D.; Hansma, P. K.

    2012-01-01

    Most current atomic force microscopes (AFMs) use piezoelectric ceramics for scan actuation. Piezoelectric ceramics provide precision motion with fast response to applied voltage potential. A drawback to piezoelectric ceramics is their inherently limited ranges. For many samples this is a nonissue, as imaging the nanoscale details is the goal. However, a key advantage of AFM over other microscopy techniques is its ability to image biological samples in aqueous buffer. Many biological specimens have topography for which the range of piezoactuated stages is limiting, a notable example of which is bone. In this article, we present the use of voice coils in scan actuation for an actuation range in the Z-axis an order of magnitude larger than any AFM commercially available today. The increased scan size will allow for imaging an important new variety of samples, including bone fractures. PMID:22380097

  17. Atomic-force microscopy of submicron films of electroactive polymer

    NASA Astrophysics Data System (ADS)

    Karamov, D. D.; Kornilov, V. M.; Lachinov, A. N.; Kraikin, V. A.; Ionova, I. A.

    2016-07-01

    Atomic-force microscopy is used to study the supramolecular structure of submicron films of electroactive thermally stable polymer (polydiphenylenephthalide (PDP)). It has been demonstrated that PDP films produced using centrifuging are solid homogeneous films with thicknesses down to several nanometers, which correspond to two or three monomolecular layers. The film volume is structurized at thicknesses greater than 100 nm. The study of the rheological properties of solutions used for film production yields a crossover point that separates the domains of strongly diluted and semidiluted solutions. A transition from the globular structure to the associate structure is observed in films that are produced using solutions with a boundary concentration. A model of the formation of polymer film that involves the presence of associates in the original solution is discussed.

  18. Imaging of nucleic acids with atomic force microscopy

    PubMed Central

    Lyubchenko, Yuri L.; Shlyakhtenko, Luda S.; Ando, Toshio

    2011-01-01

    Atomic force microscopy (AFM) is a key tool of nanotechnology with great importance in applications to DNA nanotechnology and to the recently emerging field of RNA nanotechnology. Advances in the methodology of AFM now enable reliable and reproducible imaging of DNA of various structures, topologies, and DNA and RNA nanostructures. These advances are reviewed here with emphasis on methods utilizing modification of mica to prepare the surfaces enabling reliable and reproducible imaging of DNA and RNA nanostructures. Since the AFM technology for DNA is more mature, AFM imaging of DNA is introduced in this review to provide experience and background for the improvement of AFM imaging of RNA. Examples of imaging different structures of RNA and DNA are discussed and illustrated. Special attention is given to the potential use of AFM to image the dynamics of nucleic acids at the nanometer scale. As such, we review recent advances with the use of time-lapse AFM. PMID:21310240

  19. GaN nanowire tips for nanoscale atomic force microscopy.

    PubMed

    Behzadirad, Mahmoud; Nami, Mohsen; Rishinaramagalam, Ashwin; Feezell, Daniel; Busani, Tito

    2017-04-07

    Imaging of high-aspect-ratio nanostructures with sharp edges and straight walls in nanoscale metrology by Atomic Force Microscopy (AFM) has been challenging due to the mechanical properties and conical geometry of the majority of available commercial tips. Here we report on the fabrication of GaN probes for nanoscale metrology of high-aspect-ratio structures to enhance the resolution of AFM imaging and improve the durability of AFM tips. GaN nanowires (NWs) were fabricated using bottom-up and top-down techniques and bonded to Si cantilevers to scan vertical trenches on Si substrates. Over several scans, the GaN probes demonstrated excellent durability while scanning uneven structures and showed resolution enhancements in topography images, independent of scan direction, compared to commercial Si tips.

  20. Silicon Carbide Epitaxial Films Studied by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    1996-01-01

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

  1. Atomic force microscopy spring constant determination in viscous liquids.

    PubMed

    Pirzer, Tobias; Hugel, Thorsten

    2009-03-01

    The spring constant of cantilever in atomic force microscopy (AFM) is often calibrated from thermal noise spectra. Essential for accurate implementation of this "thermal noise method" is an appropriate fitting function and procedure. Here, we survey the commonly used fitting functions and examine their applicability in a range of environments. We find that viscous liquid environments are extremely problematic due to the frequency dependent nature of the damping coefficient. The deviations from the true spring constant were sometimes more than 100% when utilizing the fit routines built into the three investigated commercial AFM instruments; similar problems can arise with homebuilt AFMs. We discuss the reasons for this problem, especially the limits of the fitting process. Finally, we present a thermal noise based procedure and an improved fit function to determine the spring constant with AFMs in fluids of various viscosities.

  2. Atomic force microscopy spring constant determination in viscous liquids

    NASA Astrophysics Data System (ADS)

    Pirzer, Tobias; Hugel, Thorsten

    2009-03-01

    The spring constant of cantilever in atomic force microscopy (AFM) is often calibrated from thermal noise spectra. Essential for accurate implementation of this "thermal noise method" is an appropriate fitting function and procedure. Here, we survey the commonly used fitting functions and examine their applicability in a range of environments. We find that viscous liquid environments are extremely problematic due to the frequency dependent nature of the damping coefficient. The deviations from the true spring constant were sometimes more than 100% when utilizing the fit routines built into the three investigated commercial AFM instruments; similar problems can arise with homebuilt AFMs. We discuss the reasons for this problem, especially the limits of the fitting process. Finally, we present a thermal noise based procedure and an improved fit function to determine the spring constant with AFMs in fluids of various viscosities.

  3. The long range voice coil atomic force microscope

    SciTech Connect

    Barnard, H.; Randall, C.; Bridges, D.; Hansma, P. K.

    2012-02-15

    Most current atomic force microscopes (AFMs) use piezoelectric ceramics for scan actuation. Piezoelectric ceramics provide precision motion with fast response to applied voltage potential. A drawback to piezoelectric ceramics is their inherently limited ranges. For many samples this is a nonissue, as imaging the nanoscale details is the goal. However, a key advantage of AFM over other microscopy techniques is its ability to image biological samples in aqueous buffer. Many biological specimens have topography for which the range of piezoactuated stages is limiting, a notable example of which is bone. In this article, we present the use of voice coils in scan actuation for an actuation range in the Z-axis an order of magnitude larger than any AFM commercially available today. The increased scan size will allow for imaging an important new variety of samples, including bone fractures.

  4. Imaging the membrane protein bacteriorhodopsin with the atomic force microscope

    SciTech Connect

    Butt, H.J.; Downing, K.H.; Hansma, P.K. )

    1990-12-01

    The membrane protein bacteriorhodopsin was imaged in buffer solution at room temperature with the atomic force microscope. Three different substrates were used: mica, silanized glass and lipid bilayers. Single bacteriorhodopsin molecules could be imaged in purple membranes adsorbed to mica. A depression was observed between the bacteriorhodopsin molecules. The two dimensional Fourier transform showed the hexagonal lattice with a lattice constant of 6.21 +/- 0.20 nm which is in agreement with results of electron diffraction experiments. Spots at a resolution of approximately 1.1 nm could be resolved. A protein, cationic ferritin, could be imaged bound to the purple membranes on glass which was silanized with aminopropyltriethoxysilane. This opens the possibility of studying receptor/ligand binding under native conditions. In addition, purple membranes bound to a lipid bilayer were imaged. These images may help in interpreting results of functional studies done with purple membranes adsorbed to black lipid membranes.

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

    PubMed

    Verbiest, G J; van der Zalm, D J; Oosterkamp, T H; Rost, M J

    2015-03-01

    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.

  6. Atomic force microscopy spring constant determination in viscous liquids

    SciTech Connect

    Pirzer, Tobias; Hugel, Thorsten

    2009-03-15

    The spring constant of cantilever in atomic force microscopy (AFM) is often calibrated from thermal noise spectra. Essential for accurate implementation of this 'thermal noise method' is an appropriate fitting function and procedure. Here, we survey the commonly used fitting functions and examine their applicability in a range of environments. We find that viscous liquid environments are extremely problematic due to the frequency dependent nature of the damping coefficient. The deviations from the true spring constant were sometimes more than 100% when utilizing the fit routines built into the three investigated commercial AFM instruments; similar problems can arise with homebuilt AFMs. We discuss the reasons for this problem, especially the limits of the fitting process. Finally, we present a thermal noise based procedure and an improved fit function to determine the spring constant with AFMs in fluids of various viscosities.

  7. Progress in the Correlative Atomic Force Microscopy and Optical Microscopy.

    PubMed

    Zhou, Lulu; Cai, Mingjun; Tong, Ti; Wang, Hongda

    2017-04-24

    Atomic force microscopy (AFM) has evolved from the originally morphological imaging technique to a powerful and multifunctional technique for manipulating and detecting the interactions between molecules at nanometer resolution. However, AFM cannot provide the precise information of synchronized molecular groups and has many shortcomings in the aspects of determining the mechanism of the interactions and the elaborate structure due to the limitations of the technology, itself, such as non-specificity and low imaging speed. To overcome the technical limitations, it is necessary to combine AFM with other complementary techniques, such as fluorescence microscopy. The combination of several complementary techniques in one instrument has increasingly become a vital approach to investigate the details of the interactions among molecules and molecular dynamics. In this review, we reported the principles of AFM and optical microscopy, such as confocal microscopy and single-molecule localization microscopy, and focused on the development and use of correlative AFM and optical microscopy.

  8. Atomic Force Microscopy Imaging Techniques for Piezoelectric Materials

    NASA Astrophysics Data System (ADS)

    Kunz, Jeremy; Inglefield, Colin

    2009-10-01

    Using an Atomic Force Microscope (AFM) and a Lock-in Detector we investigated the effectiveness of two different methods of local piezoelectricity within a standard commercial piezoelectric material, Pb(Ti, Zr)O3 (PIC 151). In the first method, sometimes known as piezo-mode AFM, we applied an AC voltage to the sample locally through the tip of the AFM; we were able to image the local piezoelectric response while taking a topographical image. For the second set of measurements, we used a sample of the PIC 151 material with a uniform silver electrode over the entire surface. The voltage was applied to the entire sample through the electrodes and the AFM cantilever measured local response. Images based on the two techniques will be compared along with the methods themselves.

  9. Measuring viscoelasticity of soft samples using atomic force microscopy.

    PubMed

    Tripathy, S; Berger, E J

    2009-09-01

    Relaxation indentation experiments using atomic force microscopy (AFM) are used to obtain viscoelastic material properties of soft samples. The quasilinear viscoelastic (QLV) model formulated by Fung (1972, "Stress Strain History Relations of Soft Tissues in Simple Elongation," in Biomechanics, Its Foundation and Objectives, Prentice-Hall, Englewood Cliffs, NJ, pp. 181-207) for uniaxial compression data was modified for the indentation test data in this study. Hertz contact mechanics was used for the instantaneous deformation, and a reduced relaxation function based on continuous spectrum is used for the time-dependent part in the model. The modified QLV indentation model presents a novel method to obtain viscoelastic properties from indentation data independent of relaxation times of the test. The major objective of the present study is to develop the QLV indentation model and implement the model on AFM indentation data for 1% agarose gel and a viscoelastic polymer using spherical indenter.

  10. Atomic force microscope based on vertical silicon probes

    NASA Astrophysics Data System (ADS)

    Walter, Benjamin; Mairiaux, Estelle; Faucher, Marc

    2017-06-01

    A family of silicon micro-sensors for Atomic Force Microscope (AFM) is presented that allows to operate with integrated transducers from medium to high frequencies together with moderate stiffness constants. The sensors are based on Micro-Electro-Mechanical-Systems technology. The vertical design specifically enables a long tip to oscillate perpendicularly to the surface to be imaged. The tip is part of a resonator including quasi-flexural composite beams, and symmetrical transducers that can be used as piezoresistive detector and/or electro-thermal actuator. Two vertical probes (Vprobes) were operated up to 4.3 MHz with stiffness constants 150 N/m to 500 N/m and the capability to oscillate from 10 pm to 90 nm. AFM images of several samples both in amplitude modulation (tapping-mode) and in frequency modulation were obtained.

  11. Gating mechanosensitive channels in bacteria with an atomic force microscope

    NASA Astrophysics Data System (ADS)

    Garces, Renata; Miller, Samantha; Schmidt, Christoph F.; Third Institute of Physics Team; School of Medical Sciences Collaboration

    The regulation of growth and integrity of bacteria is critically linked to mechanical stress. Bacteria typically maintain a high difference of osmotic pressure (turgor pressure) with respect to the environment. This pressure difference (on the order of 1 atm) is supported by the cell envelope, a composite of lipid membranes and a rigid cell wall. Turgor pressure is controlled by the ratio of osmolytes inside and outside bacteria and thus, can abruptly increase upon osmotic downshock. For structural integrity bacteria rely on the mechanical stability of the cell wall and on the action of mechanosensitive (MS) channels: membrane proteins that release solutes in response to stress in the cell envelope. We here present experimental data on MS channels gating. We activate channels by indenting living bacteria with the cantilever of an atomic force microscope (AFM). We compare responses of wild-type and mutant bacteria in which some or all MS channels have been eliminated.

  12. High bandwidth deflection readout for atomic force microscopes.

    PubMed

    Steininger, Juergen; Bibl, Matthias; Yoo, Han Woong; Schitter, Georg

    2015-10-01

    This contribution presents the systematic design of a high bandwidth deflection readout mechanism for atomic force microscopes. The widely used optical beam deflection method is revised by adding a focusing lens between the cantilever and the quadrant photodetector (QPD). This allows the utilization of QPDs with a small active area resulting in an increased detection bandwidth due to the reduced junction capacitance. Furthermore the additional lens can compensate a cross talk between a compensating z-movement of the cantilever and the deflection readout. Scaling effects are analyzed to get the optimal spot size for the given geometry of the QPD. The laser power is tuned to maximize the signal to noise ratio without limiting the bandwidth by local saturation effects. The systematic approach results in a measured -3 dB detection bandwidth of 64.5 MHz at a deflection noise density of 62fm/√Hz.

  13. Measurement of solution viscosity by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Ahmed, Nabil; Nino, Diego F.; Moy, Vincent T.

    2001-06-01

    We report on studies aimed at employing the atomic force microscope (AFM) to measure the viscosity of aqueous solutions. At ambient temperature, the AFM cantilever undergoes thermal fluctuations that are highly sensitive to the local environment. Here, we present measurements of the cantilever's resonant frequency in aqueous solutions of glycerol, sucrose, ethanol, sodium chloride, polyethylene glycol, and bovine plasma albumin. The measurements revealed that variations in the resonant frequency of the cantilever in the different solutions are largely dependent on the viscosity of the medium. An application of this technique is to monitor the progression of a chemical reaction where a change in viscosity is expected to occur. An example is demonstrated through monitoring of the hydrolysis of double stranded deoxyribonucleic acid by DNase I.

  14. Nuclear pore function viewed with atomic force microscopy.

    PubMed

    Danker, T; Oberleithner, H

    2000-04-01

    In this review we focus on studies using atomic force microscopy (AFM) to describe the function of nuclear pore complexes (NPC). After a short introduction of AFM we follow the route of cargo molecules from the cytosol into the nucleus. AFM visualizes cargo before translocation into the nucleoplasm, cargo docking at the cytoplasmic NPC surface, cargo passing through the NPC and changes in NPC conformation in response to ATP, Calcium and pH. We discuss AFM experiments on nuclear envelopes on the basis of previous data obtained with more conventional techniques such as electron microscopy, confocal microscopy and other imaging techniques. Finally we draw attention to the recently developed nuclear hourglass technique that serves as a new electrophysiological approach to studying the structure-function relationship of NPC in combination with AFM at a molecular level.

  15. Mapping thermal conductivity using bimetallic atomic force microscopy probes

    NASA Astrophysics Data System (ADS)

    Grover, Ranjan; McCarthy, Brendan; Sarid, Dror; Guven, Ibrahim

    2006-06-01

    We demonstrate a technique to measure local thermal conductivity of materials using an atomic force microscope equipped with a commercial silicon cantilever coated by a thin metal film. This bimaterial cantilever acts as a bimetallic strip that bends when heated by a focused laser beam. The bending is apparent as a topographic distortion, which varies with the amount of heat flowing from the cantilever's tip into the sample. By comparing the surface topographies of the sample, as measured with heated and unheated cantilevers, the local thermal conductivity of the tip-sample contact area can be determined. Experimental results with this system are presented and found to be in good agreement with a finite element model.

  16. Pore size of agarose gels by atomic force microscopy.

    PubMed

    Pernodet, N; Maaloum, M; Tinland, B

    1997-01-01

    The pore size of agarose gel in water at different concentrations was directly measured using atomic force microscopy (AFM). The experiment was specially designed to work under aqueous conditions and allows direct observation of the "unperturbed" gel without invasive treatment. The pore size a as a function of gel concentration C shows a power law dependence a approximately C-gamma, where gamma lies between the prediction of the Ogston model for a random array of straight chains, 0.5, and the value predicted by De Gennes for a network of flexible chains, 0.75. We confirm that gels present a wide pore size distribution and show that it narrows as the concentration increases.

  17. Atomic force microscopy of single- and double-stranded DNA.

    PubMed Central

    Hansma, H G; Sinsheimer, R L; Li, M Q; Hansma, P K

    1992-01-01

    A method has been developed for imaging single-stranded DNA with the atomic force microscope (AFM). phi X174 single-stranded DNA in formaldehyde on mica can be imaged in the AFM under propanol or butanol or in air. Measured lengths of most molecules are on the order of 1 mu, although occasionally more extended molecules with lengths of 1.7 to 1.9 mu are seen. Single-stranded DNA in the AFM generally appears lumpier than double-stranded DNA, even when extended. Images of double-stranded lambda DNA in the AFM show more sharp kinks and bends than are typically observed in the electron microscope. Dense, aggregated fields of double-stranded plasmids can be converted by gentle rinsing with hot water to well spread fields. Images PMID:1386422

  18. The applications of atomic force microscopy to vision science.

    PubMed

    Last, Julie A; Russell, Paul; Nealey, Paul F; Murphy, Christopher J

    2010-12-01

    The atomic force microscope (AFM) is widely used in materials science and has found many applications in biological sciences but has been limited in use in vision science. The AFM can be used to image the topography of soft biological materials in their native environments. It can also be used to probe the mechanical properties of cells and extracellular matrices, including their intrinsic elastic modulus and receptor-ligand interactions. In this review, the operation of the AFM is described along with a review of how it has been thus far used in vision science. It is hoped that this review will serve to stimulate vision scientists to consider incorporating AFM as part of their research toolkit.

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

    PubMed

    Okajima, Takaharu

    2012-11-01

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

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

    PubMed

    Müller, Daniel J; Engel, Andreas

    2007-01-01

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

  1. Progress in the Correlative Atomic Force Microscopy and Optical Microscopy

    PubMed Central

    Zhou, Lulu; Cai, Mingjun; Tong, Ti; Wang, Hongda

    2017-01-01

    Atomic force microscopy (AFM) has evolved from the originally morphological imaging technique to a powerful and multifunctional technique for manipulating and detecting the interactions between molecules at nanometer resolution. However, AFM cannot provide the precise information of synchronized molecular groups and has many shortcomings in the aspects of determining the mechanism of the interactions and the elaborate structure due to the limitations of the technology, itself, such as non-specificity and low imaging speed. To overcome the technical limitations, it is necessary to combine AFM with other complementary techniques, such as fluorescence microscopy. The combination of several complementary techniques in one instrument has increasingly become a vital approach to investigate the details of the interactions among molecules and molecular dynamics. In this review, we reported the principles of AFM and optical microscopy, such as confocal microscopy and single-molecule localization microscopy, and focused on the development and use of correlative AFM and optical microscopy. PMID:28441775

  2. Nanometrology of delignified Populus using mode synthesizing atomic force microscopy

    SciTech Connect

    Tetard, Laurene; Passian, Ali; Farahi, R H; Davison, Brian H; Jung, S; Ragauskas, A J; Lereu, Aude; Thundat, Thomas George

    2011-01-01

    The study of the spatially resolved physical and compositional properties of materials at the nanoscale is increasingly challenging due to the level of complexity of biological specimens such as those of interest in bioenergy production. Mode synthesizing atomic force microscopy (MSAFM) has emerged as a promising metrology tool for such studies. It is shown that, by tuning the mechanical excitation of the probe-sample system, MSAFM can be used to dynamically investigate the multifaceted complexity of plant cells. The results are argued to be of importance both for the characteristics of the invoked synthesized modes and for accessing new features of the samples. As a specific system to investigate, we present images of Populus, before and after a holopulping treatment, a crucial step in the biomass delignification process.

  3. Characterization of Gorleben groundwater colloids by atomic force microscopy.

    PubMed

    Plaschke, M; Römer, J; Kim, J I

    2002-11-01

    Groundwater colloids from the Gorleben site (Lower Saxony, Germany) are characterized in the presence of Eu(III) by tapping-mode atomic force microscopy (AFM) with phase contrast imaging. Using a liquid cell the method allows investigations of samples being in contact with aqueous solution. This ensures that complex structures are kept in their native hydrated state. Different types of colloids and aggregates are found by AFM, e.g., spherical particles, fibrous structures, and structures which appear to be hollow. A partial coating of the edges of clay particles with humic colloids can be assumed from phase contrast images. Therefore, aquatic colloids and their aggregates found in Gorleben groundwater can be characterized as a complex mixture of components, which may influence the migration of groundwater contaminants in different processes.

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

    SciTech Connect

    Verbiest, G. J.; Zalm, D. J. van der; Oosterkamp, T. H.; Rost, M. J.

    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.

  5. Monoclonal antibody aggregation intermediates visualized by atomic force microscopy.

    PubMed

    Lee, Hanjoo; Kirchmeier, Marc; Mach, Henryk

    2011-02-01

    Ubiquitous but highly variable processes of therapeutic protein aggregation remain poorly characterized, especially in the context of common infusion reactions and clinical immunogenicity. Among the numerous challenges is the characterization of intermediate steps that lead to the appearance of precipitates. Although the biophysical methods for elucidation of secondary and tertiary structures as well as overall size distribution are typically well established in the development laboratories, the use of molecular scale imaging techniques is still relatively rare due to low throughput and technical complexity. In this work, we present the use of atomic force microscopy to examine morphology of monoclonal antibody aggregates. Despite varying in primary structure as a result of different complementarity defining regions, most antibodies studied exhibited a similar aggregation intermediate consisting of several monomers. However, the manner of subsequent condensation of these oligomers appeared to differ between the antibodies, suggesting stability-dependent mechanisms.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Ultrastructural organization of amyloid fibrils by atomic force microscopy.

    PubMed Central

    Chamberlain, A K; MacPhee, C E; Zurdo, J; Morozova-Roche, L A; Hill, H A; Dobson, C M; Davis, J J

    2000-01-01

    Atomic force microscopy has been employed to investigate the structural organization of amyloid fibrils produced in vitro from three very different polypeptide sequences. The systems investigated are a 10-residue peptide derived from the sequence of transthyretin, the 90-residue SH3 domain of bovine phosphatidylinositol-3'-kinase, and human wild-type lysozyme, a 130-residue protein containing four disulfide bridges. The results demonstrate distinct similarities between the structures formed by the different classes of fibrils despite the contrasting nature of the polypeptide species involved. SH3 and lysozyme fibrils consist typically of four protofilaments, exhibiting a left-handed twist along the fibril axis. The substructure of TTR(10-19) fibrils is not resolved by atomic force microscopy and their uniform appearance is suggestive of a regular self-association of very thin filaments. We propose that the exact number and orientation of protofilaments within amyloid fibrils is dictated by packing of the regions of the polypeptide chains that are not directly involved in formation of the cross-beta core of the fibrils. The results obtained for these proteins, none of which is directly associated with any human disease, are closely similar to those of disease-related amyloid fibrils, supporting the concept that amyloid is a generic structure of polypeptide chains. The detailed architecture of an individual fibril, however, depends on the manner in which the protofilaments assemble into the fibrillar structure, which in turn is dependent on the sequence of the polypeptide and the conditions under which the fibril is formed. PMID:11106631

  8. Ultrastructural organization of amyloid fibrils by atomic force microscopy.

    PubMed

    Chamberlain, A K; MacPhee, C E; Zurdo, J; Morozova-Roche, L A; Hill, H A; Dobson, C M; Davis, J J

    2000-12-01

    Atomic force microscopy has been employed to investigate the structural organization of amyloid fibrils produced in vitro from three very different polypeptide sequences. The systems investigated are a 10-residue peptide derived from the sequence of transthyretin, the 90-residue SH3 domain of bovine phosphatidylinositol-3'-kinase, and human wild-type lysozyme, a 130-residue protein containing four disulfide bridges. The results demonstrate distinct similarities between the structures formed by the different classes of fibrils despite the contrasting nature of the polypeptide species involved. SH3 and lysozyme fibrils consist typically of four protofilaments, exhibiting a left-handed twist along the fibril axis. The substructure of TTR(10-19) fibrils is not resolved by atomic force microscopy and their uniform appearance is suggestive of a regular self-association of very thin filaments. We propose that the exact number and orientation of protofilaments within amyloid fibrils is dictated by packing of the regions of the polypeptide chains that are not directly involved in formation of the cross-beta core of the fibrils. The results obtained for these proteins, none of which is directly associated with any human disease, are closely similar to those of disease-related amyloid fibrils, supporting the concept that amyloid is a generic structure of polypeptide chains. The detailed architecture of an individual fibril, however, depends on the manner in which the protofilaments assemble into the fibrillar structure, which in turn is dependent on the sequence of the polypeptide and the conditions under which the fibril is formed.

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

    PubMed

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

    2012-01-01

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

  10. Quality of corneal lamellar cuts quantified using atomic force microscopy

    PubMed Central

    Ziebarth, Noël M.; Dias, Janice; Hürmeriç, Volkan; Shousha, Mohamed Abou; Yau, Chiyat Ben; Moy, Vincent T.; Culbertson, William; Yoo, Sonia H.

    2012-01-01

    PURPOSE To quantify the cut quality of lamellar dissections made with the femtosecond laser using atomic force microscopy (AFM). SETTING Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA. DESIGN Experimental study. METHODS Experiments were performed on 3 pairs of human cadaver eyes. The cornea was thinned to physiologic levels by placing the globe, cornea side down, in 25% dextran for 24 hours. The eyes were reinflated to normal pressures by injecting a balanced salt solution into the vitreous cavity. The eyes were placed in a holder, the epithelium was removed, and the eyes were cut with a Visumax femtosecond laser. The energy level was 180 nJ for the right eye and 340 nJ for the left eye of each pair. The cut depths were 200 μm, 300 μm, and 400 μm, with the cut depth maintained for both eyes of each pair. A 12.0 mm trephination was then performed. The anterior portion of the lamellar surface was placed in a balanced salt solution and imaged with AFM. As a control, the posterior surface was placed in 2% formalin and imaged with environmental scanning electron microscopy (SEM). Four quantitative parameters (root-mean-square deviation, average deviation, skewness, kurtosis) were calculated from the AFM images. RESULTS From AFM, the 300 μm low-energy cuts were the smoothest. Similar results were seen qualitatively in the environmental SEM images. CONCLUSION Atomic force microscopy provided quantitative information on the quality of lamellar dissections made using a femtosecond laser, which is useful in optimizing patient outcomes in refractive and lamellar keratoplasty surgeries. PMID:23141078

  11. Photothermal excitation setup for a modified commercial atomic force microscope

    SciTech Connect

    Adam, Holger; Rode, Sebastian; Schreiber, Martin; Kühnle, Angelika; Kobayashi, Kei; Yamada, Hirofumi

    2014-02-15

    High-resolution imaging in liquids using frequency modulation atomic force microscopy is known to suffer from additional peaks in the resonance spectrum that are unrelated to the cantilever resonance. These unwanted peaks are caused by acoustic modes of the liquid and the setup arising from the indirect oscillation excitation by a piezoelectric transducer. Photothermal excitation has been identified as a suitable method for exciting the cantilever in a direct manner. Here, we present a simple design for implementing photothermal excitation in a modified Multimode scan head from Bruker. Our approach is based on adding a few components only to keep the modifications as simple as possible and to maintain the low noise level of the original setup with a typical deflection noise density of about 15 fm/√(Hz) measured in aqueous solution. The success of the modification is illustrated by a comparison of the resonance spectra obtained with piezoelectric and photothermal excitation. The performance of the systems is demonstrated by presenting high-resolution images on bare calcite in liquid as well as organic adsorbates (Alizarin Red S) on calcite with simultaneous atomic resolution of the underlying calcite substrate.

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

    SciTech Connect

    Liu, Chih-Hao; Horng, Jim-Tong; Chang, Jeng-Shian; Hsieh, Chung-Fan; Tseng, You-Chen; Lin, Shiming

    2012-01-06

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

  13. Probing surface adhesion forces of Enterococcus faecalis to medical-grade polymers using atomic force microscopy.

    PubMed

    Sénéchal, Annie; Carrigan, Shawn D; Tabrizian, Maryam

    2004-05-11

    The aim of this study was to compare the initial adhesion forces of the uropathogen Enterococcus faecalis with the medical-grade polymers polyurethane (PU), polyamide (PA), and poly(tetrafluoroethylene) (PTFE). To quantify the cell-substrate adhesion forces, a method was developed using atomic force microscopy (AFM) in liquid that allows for the detachment of individual live cells from a polymeric surface through the application of increasing force using unmodified cantilever tips. Results show that the lateral force required to detach E. faecalis cells from a substrate differed depending on the nature of the polymeric surface: a force of 19 +/- 4 nN was required to detach cells from PU, 6 +/- 4 nN from PA, and 0.7 +/- 0.3 nN from PTFE. Among the unfluorinated polymers (PU and PA), surface wettability was inversely proportional to the strength of adhesion. AFM images also demonstrated qualitative differences in bacterial adhesion; PU was covered by clusters of cells with few cell singlets present, whereas PA was predominantly covered by individual cells. Moreover, extracellular material could be observed on some clusters of PU-adhered cells as well as in the adjacent region surrounding cells adhered on PA. E. faecalis adhesion to the fluorinated polymer (PTFE) showed different characteristics; only a few individual cells were found, and bacteria were easily damaged, and thus detached, by the tip. This work demonstrates the utility of AFM for measurement of cell-substrate lateral adhesion forces and the contribution these forces make toward understanding the initial stages of bacterial adhesion. Further, it suggests that initial adhesion can be controlled, through appropriate biomaterial design, to prevent subsequent formation of aggregates and biofilms.

  14. Fluctuations of the Casimir-Polder force between an atom and a conducting wall

    SciTech Connect

    Messina, R.; Passante, R.

    2007-09-15

    We consider quantum fluctuations of the Casimir-Polder force between a neutral atom and a perfectly conducting wall in the ground state of the system. In order to obtain the atom-wall force fluctuation we first define an operator directly associated with the force experienced by the atom considered as a polarizable body in an electromagnetic field and we use a time-averaged force operator in order to avoid ultraviolet divergences appearing in the fluctuation of the force. This time-averaged force operator takes into account that any measurement involves a finite time. We also calculate the Casimir-Polder force fluctuation for an atom between two conducting walls. Experimental observability of these Casimir-Polder force fluctuations is also discussed, as well as the dependence of the relative force fluctuation on the duration of the measurement.

  15. Uncertainty quantification in nanomechanical measurements using the atomic force microscope.

    PubMed

    Wagner, Ryan; Moon, Robert; Pratt, Jon; Shaw, Gordon; Raman, Arvind

    2011-11-11

    Quantifying uncertainty in measured properties of nanomaterials is a prerequisite for the manufacture of reliable nanoengineered materials and products. Yet, rigorous uncertainty quantification (UQ) is rarely applied for material property measurements with the atomic force microscope (AFM), a widely used instrument that can measure properties at nanometer scale resolution of both inorganic and biological surfaces and nanomaterials. We present a framework to ascribe uncertainty to local nanomechanical properties of any nanoparticle or surface measured with the AFM by taking into account the main uncertainty sources inherent in such measurements. We demonstrate the framework by quantifying uncertainty in AFM-based measurements of the transverse elastic modulus of cellulose nanocrystals (CNCs), an abundant, plant-derived nanomaterial whose mechanical properties are comparable to Kevlar fibers. For a single, isolated CNC the transverse elastic modulus was found to have a mean of 8.1 GPa and a 95% confidence interval of 2.7-20 GPa. A key result is that multiple replicates of force-distance curves do not sample the important sources of uncertainty, which are systematic in nature. The dominant source of uncertainty is the nondimensional photodiode sensitivity calibration rather than the cantilever stiffness or Z-piezo calibrations. The results underscore the great need for, and open a path towards, quantifying and minimizing uncertainty in AFM-based material property measurements of nanoparticles, nanostructured surfaces, thin films, polymers and biomaterials.

  16. Probing the Lipid Membrane Dipole Potential by Atomic Force Microscopy

    PubMed Central

    Yang, Yi; Mayer, Kathryn M.; Wickremasinghe, Nissanka S.; Hafner, Jason H.

    2008-01-01

    The electrostatic properties of biological membranes can be described by three parameters: the transmembrane potential, the membrane surface potential, and the membrane dipole potential. The first two are well characterized in terms of their magnitudes and biological effects. The dipole potential, however, is not well characterized. Various methods to measure the membrane dipole potential indirectly yield different values, and there is not even agreement on the source of the membrane dipole moment. This ambiguity impedes investigations into the biological effects of the membrane dipole moment, which should be substantial considering the large interfacial fields with which it is associated. Electrostatic analysis of phosphatidylcholine lipid membranes with the atomic force microscope reveals a repulsive force between the negatively charged probe tips and the zwitterionic lipids. This unexpected interaction has been analyzed quantitatively to reveal that the repulsion is due to a weak external field created by the internal membrane dipole potential. The analysis yields a dipole moment of 1.5 Debye per lipid with a dipole potential of +275 mV for supported phosphatidylcholine membranes. This new ability to quantitatively measure the membrane dipole moment in a noninvasive manner with nanometer scale spatial resolution will be useful in identifying the biological effects of the dipole potential. PMID:18805919

  17. Quantitative surface parameter maps using Intermodulation Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Forchheimer, Daniel; Platz, Daniel; Tholén, Erik; Hutter, Carsten; Haviland, David

    2011-03-01

    It is well known that the phase image in amplitude modulation atomic force microscopy (AM-AFM) is sensitive to material properties of the surface. However that information is not enough to fully quantify the tip-surface interaction. We have developed Intermodulation AFM, based on a spectral analysis of the cantilever's nonlinear dynamics, which increases the amount of information obtained without increasing scan time. We show how it is possible to extract quantitative material properties of the surface from this additional information. The method works under the assumption of a tip-surface force model, such as the DMT model, fitting the model parameters to the measured spectral data. The parameters are obtained at each pixel of the AFM image and form surface property maps which can be displayed together with topography. We demonstrate this on different surfaces such as polymer blends, extracting stiffness and adhesive properties. D. Platz, E. A. Tholen, D. Pesen, and D. B. Haviland, Appl. Phys. Lett., 92, 153106 (2008)

  18. Mechanics of proteins with a focus on atomic force microscopy.

    PubMed

    Rico, Felix; Rigato, Annafrancesca; Picas, Laura; Scheuring, Simon

    2013-01-01

    The capacity of proteins to function relies on a balance between molecular stability to maintain their folded state and structural flexibility allowing conformational changes related to biological function. Among many others, four different examples can be chosen. The giant protein titin is stretched and can unfold during muscle contraction providing passive elasticity to muscle tissue; myoglobin adsorbs and releases oxygen molecules thank to conformational changes in its structure; the outer membrane protein G (OmpG) is a bacterial porin with a long and flexible loop that modulates gating; and the proton pump bacteriorhodopsin adapts its cytosolic half to allow proton pumping. All these conformational changes triggered either by chemical or by physical cues, require mechanical flexibility or elasticity of certain protein domains. While the methods to determine protein structure, X-ray crystallography above all, have been dramatically improved over the last decades, the number of tools that directly measure the mechanical flexibility of proteins and protein domains is still limited. In this tutorial, after a brief introduction to protein structure, we present some of the available techniques to estimate protein flexibility, then focusing on atomic force microscopy (AFM). We describe the principles of the technique and its various imaging and force spectroscopy modes of operation that allow probing the elasticity of proteins, protein domains and their surrounding environment.

  19. Atomic Force Microscopy and pharmacology: from microbiology to cancerology.

    PubMed

    Pillet, Flavien; Chopinet, Louise; Formosa, Cécile; Dague, Etienne

    2014-03-01

    Atomic Force Microscopy (AFM) has been extensively used to study biological samples. Researchers take advantage of its ability to image living samples to increase our fundamental knowledge (biophysical properties/biochemical behavior) on living cell surface properties, at the nano-scale. AFM, in the imaging modes, can probe cells morphological modifications induced by drugs. In the force spectroscopy mode, it is possible to follow the nanomechanical properties of a cell and to probe the mechanical modifications induced by drugs. AFM can be used to map single molecule distribution at the cell surface. We will focus on a collection of results aiming at evaluating the nano-scale effects of drugs, by AFM. Studies on yeast, bacteria and mammal cells will illustrate our discussion. Especially, we will show how AFM can help in getting a better understanding of drug mechanism of action. This review demonstrates that AFM is a versatile tool, useful in pharmacology. In microbiology, it has been used to study the drugs fighting Candida albicans or Pseudomonas aeruginosa. The major conclusions are a better understanding of the microbes' cell wall and of the drugs mechanism of action. In cancerology, AFM has been used to explore the effects of cytotoxic drugs or as an innovative diagnostic technology. AFM has provided original results on cultured cells, cells extracted from patient and directly on patient biopsies. This review enhances the interest of AFM technologies for pharmacology. The applications reviewed range from microbiology to cancerology. Copyright © 2013 Elsevier B.V. All rights reserved.

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

    PubMed

    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.

  1. Generation of living cell arrays for atomic force microscopy studies.

    PubMed

    Formosa, Cécile; Pillet, Flavien; Schiavone, Marion; Duval, Raphaël E; Ressier, Laurence; Dague, Etienne

    2015-01-01

    Atomic force microscopy (AFM) is a useful tool for studying the morphology or the nanomechanical and adhesive properties of live microorganisms under physiological conditions. However, to perform AFM imaging, living cells must be immobilized firmly enough to withstand the lateral forces exerted by the scanning tip, but without denaturing them. This protocol describes how to immobilize living cells, ranging from spores of bacteria to yeast cells, into polydimethylsiloxane (PDMS) stamps, with no chemical or physical denaturation. This protocol generates arrays of living cells, allowing statistically relevant measurements to be obtained from AFM measurements, which can increase the relevance of results. The first step of the protocol is to generate a microstructured silicon master, from which many microstructured PDMS stamps can be replicated. Living cells are finally assembled into the microstructures of these PDMS stamps using a convective and capillary assembly. The complete procedure can be performed in 1 week, although the first step is done only once, and thus repeats can be completed within 1 d.

  2. Atomic force microscopy study of living diatoms in ambient conditions.

    PubMed

    Gebeshuber, I C; Kindt, J H; Thompson, J B; Del Amo, Y; Stachelberger, H; Brzezinski, M A; Stucky, G D; Morse, D E; Hansma, P K

    2003-12-01

    We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species -Eunotia sudetica, Navicula seminulum and a yet unidentified species - are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and we determined the thickness of the organic case enveloping the siliceous skeleton of the cell (10 nm). Imaging proved to be stable for several hours, thereby offering the possibility to study long-term dynamic changes, such as biomineralization or cell movement, as they occur. We also focused on the natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum. Most man-made adhesives fail in wet conditions, owing to chemical modification of the adhesive or its substrate. Diatoms produce adhesives that are extremely strong and robust both in fresh- and in seawater environments. Our phase-imaging and force-pulling experiments reveal the characteristics of these natural adhesives that might be of use in designing man-made analogues that function in wet environments. Engineering stable underwater adhesives currently poses a major technical challenge.

  3. Triaxial Atomic Force Microscope Contact-Free Tweezers for Nanoassembly

    PubMed Central

    Brown, Keith A; Westervelt, Robert M

    2010-01-01

    We propose a Traixial Atomic Force Microscope (AFM) Contact-free Tweezer (TACT) for the controlled assembly of nanoparticles suspended in a liquid. The TACT overcomes four major challenges faced in nanoassembly: (1) The TACT can hold and position a single nanoparticle with spatial accuracy smaller than the nanoparticle size (~ 5 nm). (2) The nanoparticle is held away from the surface of the TACT by negative dielectrophoresis (nDEP) to prevent van der Waals forces from sticking it to the TACT. (3) The TACT holds nanoparticles in a trap that is size-matched to the particle and surrounded by a repulsive region so that it will only trap a single particle at a time. (4) The trap can hold a semiconductor nanoparticle in water with a trapping energy greater than thermal energy. For example, a 5 nm radius silicon nanoparticle is held with 10 kBT at room temperature. We propose methods for using the TACT as a nanoscale pick-and-place tool to assemble semiconductor quantum dots, biological molecules, semiconductor nanowires, and carbon nanotubes. PMID:19713582

  4. Mechanics of proteins with a focus on atomic force microscopy

    PubMed Central

    2013-01-01

    The capacity of proteins to function relies on a balance between molecular stability to maintain their folded state and structural flexibility allowing conformational changes related to biological function. Among many others, four different examples can be chosen. The giant protein titin is stretched and can unfold during muscle contraction providing passive elasticity to muscle tissue; myoglobin adsorbs and releases oxygen molecules thank to conformational changes in its structure; the outer membrane protein G (OmpG) is a bacterial porin with a long and flexible loop that modulates gating; and the proton pump bacteriorhodopsin adapts its cytosolic half to allow proton pumping. All these conformational changes triggered either by chemical or by physical cues, require mechanical flexibility or elasticity of certain protein domains. While the methods to determine protein structure, X-ray crystallography above all, have been dramatically improved over the last decades, the number of tools that directly measure the mechanical flexibility of proteins and protein domains is still limited. In this tutorial, after a brief introduction to protein structure, we present some of the available techniques to estimate protein flexibility, then focusing on atomic force microscopy (AFM). We describe the principles of the technique and its various imaging and force spectroscopy modes of operation that allow probing the elasticity of proteins, protein domains and their surrounding environment. PMID:24565326

  5. Elastic interactions between hydrogen atoms in metals. I. Lattice forces and displacements

    SciTech Connect

    Shirley, A.I.; Hall, C.K.

    1986-06-15

    This is the first of a series of papers in which a second-order perturbation theory is derived for the Hamiltonian of a metal hydride. The theory, which is called the fully harmonic lattice approximation, or FHLA, goes beyond the customary harmonic treatment of Horner and Wagner to include second-order terms for the hydrogen-hydrogen and metal-hydrogen potentials. These terms account for the hydrogen-concentration dependences of a metal hydride's volume and elastic constants; their inclusion should result in a better representation of the free-energy and phase-change behavior at high hydrogen concentration. In this paper, the forces between hydrogen atoms and metal atoms are evaluated using the FHLA. Two types of forces result: direct forces, between an isolated hydrogen atom and a metal atom, and indirect forces, which are effective forces between a hydrogen atom and a metal atom caused by the presence of a neighboring hydrogen atom. Both the direct and indirect forces each have two components: a permanent part, which is equivalent to the force exerted by a hydrogen atom on a metal atom in the pure (hydrogen-free) metal lattice, and an induced part, which corrects the permanent part for the effects of the hydrogen atom on the metal-metal couplings. These four forces are evaluated for the hydrogen-niobium system. The indirect forces have one-tenth the magnitude and are of opposite sign to the direct forces. The induced component of the force is approximately one-third the size of the permanent component, and opposite to it in sign. The displacements of the metal atoms surrounding an isolated hydrogen atom or a pair of hydrogen atoms are also evaluated. These are compared with the results of previous harmonic-approximation calculations and of experiments on the hydrogen-niobium system.

  6. Atomic scale contact formation: A combined Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) study

    NASA Astrophysics Data System (ADS)

    Hagedorn, Till; El Ouali, Mehdi; Miyahara, Yoichi; Grütter, Peter

    2008-03-01

    We are investigating contact formation at the atomic scale, in particular the interplay of forces and conductivity [1]. As it has been shown (e.g. in the case of C60 in between a STM tip and an Au(111) sample [2]), the conductivity in molecular junctions depends strongly on the contact geometry. In order to fully characterize the junction, we use a homebuilt ultra high vacuum (UHV) (p < 10-10 mbar) microscope which runs in simultaneous scanning tunneling microscope (STM) and atomic force microscope (AFM) modes. Additionally we image the STM tip structure with field ion microscopy (FIM) prior to using it in our experiments [3]. In order to realize a controlled contact we use the STM tip as one electrode and the sample as counter electrode. We are investigating bare Au(111) samples and W STM tips as an example of a nano metal-metal contact and one C60 molecule sandwiched between the W-tip and the Au(111) sample as a model for a controlled metal-molecule-metal contact. We will present new measurements of I(z), F(z) and dI/dV (z) curves of the above mentioned systems, where z is the tip-sample separation as well as images of the sample and tip structure. [1] Sun et. al. PRB 71 193407, 2005 [2] De Menech et. al. PRB 73, 155407, 2006 [3] Lucier et. al. PRB 72, 235420, 2005

  7. Study of LDEF particulate contamination using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Anderson, Mark S.; Maag, Carl R.

    1992-02-01

    On the STS-32 Space Shuttle mission, a flight experiment provided an understanding of the effects of the environment on the long duration exposure facility (LDEF) from rendezvous with the shuttle until removal from the payload bay at the Orbiter Processing Facility (OPF) at NASA/KSC. The interim operational contamination monitor (IOCM) is an attached shuttle payload that has been used on two earlier flights (STS 51C and STS 28) to quantify the contamination deposited during the course of the missions. The IOCM can characterize by direct measurement the deposition of molecular and particulate contamination during any phase of flight, i.e., prelaunch, ascent, on-orbit operations, descent, and ferry flight of the shuttle. Measurements are made continually during these periods. Two types of particulate collection sensors are employed in order to avoid efficiency of collection uncertainties. In addition to these principal measurements, the IOCM actively measures the optical property changes of thermal control surfaces by calorimetry, the flux of the ambient atomic oxygen environment, the incident solar flux, and the absolute ambient pressure in the payload bay. The IOCM also provides a structure and sample holders for the exposure of passive material samples to the space environment, e.g., thermal cycling, atomic oxygen, and micrometeoroids and/or orbital debris, etc. One of the more salient results from the STS-32 flight suggests that the LDEF emitted a large source of contamination (mainly particulates) after berthing into the shuttle. The source emission rate of LDEF averaged 2.5 X 10-12 gr/cm2-sec for a period of eighty hours following berthing, falling off to a rate of 4.1 X 10-13 gr/cm2-sec just prior to re-entry. Post flight obscuration ratios on IOCM surfaces were measured at 2.4 percent. An atomic force microscope (AFM) was used to perform post-flight characterization of the IOCM sensors. The AFM is a new instrument capable of ultra high (atomic) resolution

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  9. Atomic force microscopy detects changes in the interaction forces between GroEL and substrate proteins.

    PubMed

    Vinckier, A; Gervasoni, P; Zaugg, F; Ziegler, U; Lindner, P; Groscurth, P; Plückthun, A; Semenza, G

    1998-06-01

    The structure of the Escherichia coli chaperonin GroEL has been investigated by tapping-mode atomic force microscopy (AFM) under liquid. High-resolution images can be obtained, which show the up-right position of GroEL adsorbed on mica with the substrate-binding site on top. Because of this orientation, the interaction between GroEL and two substrate proteins, citrate synthase from Saccharomyces cerevisiae with a destabilizing Gly-->Ala mutation and RTEM beta-lactamase from Escherichia coli with two Cys-->Ala mutations, could be studied by force spectroscopy under different conditions. The results show that the interaction force decreases in the presence of ATP (but not of ATPgammaS) and that the force is smaller for native-like proteins than for the fully denatured ones. It also demonstrates that the interaction energy with GroEL increases with increasing molecular weight. By measuring the interaction force changes between the chaperonin and the two different substrate proteins, we could specifically detect GroEL conformational changes upon nucleotide binding.

  10. Accurate force spectroscopy in tapping mode atomic force microscopy in liquids

    NASA Astrophysics Data System (ADS)

    Xu, Xin; Melcher, John; Raman, Arvind

    2010-01-01

    Existing force spectroscopy methods in tapping mode atomic force microscopy (AFM) such as higher harmonic inversion [M. Stark, R. W. Stark, W. M. Heckl, and R. Guckenberger, Proc. Natl. Acad. Sci. U.S.A. 99, 8473 (2002)] or scanning probe acceleration microscopy [J. Legleiter, M. Park, B. Cusick, and T. Kowalewski, Proc. Natl. Acad. Sci. U.S.A. 103, 4813 (2006)] or integral relations [M. Lee and W. Jhe, Phys. Rev. Lett. 97, 036104 (2006); S. Hu and A. Raman, Nanotechnology 19, 375704 (2008); H. Hölscher, Appl. Phys. Lett. 89, 123109 (2006); A. J. Katan, Nanotechnology 20, 165703 (2009)] require and assume as an observable the tip dynamics in a single eigenmode of the oscillating microcantilever. We demonstrate that this assumption can distort significantly the extracted tip-sample interaction forces when applied to tapping mode AFM with soft cantilevers in liquid environments. This exception is due to the fact that under these conditions the second eigenmode is momentarily excited and the observed tip dynamics clearly contains contributions from the fundamental and second eigenmodes. To alleviate this problem, a simple experimental method is proposed to screen the second eigenmode contributions in the observed tip deflection signal to allow accurate tip-sample force reconstruction in liquids. The method is implemented experimentally to reconstruct interaction forces on polymer, bacteriorhodopsin membrane, and mica samples in buffer solutions.

  11. Quantification of In-Contact Probe-Sample Electrostatic Forces with Dynamic Atomic Force Microscopy.

    PubMed

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

    2016-12-13

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

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

    PubMed

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

    2017-01-04

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

  13. Adhesion force mapping on wood by atomic force microscopy: influence of surface roughness and tip geometry

    PubMed Central

    Kasal, B.

    2016-01-01

    This study attempts to address the interpretation of atomic force microscopy (AFM) adhesion force measurements conducted on the heterogeneous rough surface of wood and natural fibre materials. The influences of wood surface roughness, tip geometry and wear on the adhesion force distribution are examined by cyclic measurements conducted on wood surface under dry inert conditions. It was found that both the variation of tip and surface roughness of wood can widen the distribution of adhesion forces, which are essential for data interpretation. When a common Si AFM tip with nanometre size is used, the influence of tip wear can be significant. Therefore, control experiments should take the sequence of measurements into consideration, e.g. repeated experiments with used tip. In comparison, colloidal tips provide highly reproducible results. Similar average values but different distributions are shown for the adhesion measured on two major components of wood surface (cell wall and lumen). Evidence supports the hypothesis that the difference of the adhesion force distribution on these two locations was mainly induced by their surface roughness. PMID:27853541

  14. Adhesion force mapping on wood by atomic force microscopy: influence of surface roughness and tip geometry.

    PubMed

    Jin, X; Kasal, B

    2016-10-01

    This study attempts to address the interpretation of atomic force microscopy (AFM) adhesion force measurements conducted on the heterogeneous rough surface of wood and natural fibre materials. The influences of wood surface roughness, tip geometry and wear on the adhesion force distribution are examined by cyclic measurements conducted on wood surface under dry inert conditions. It was found that both the variation of tip and surface roughness of wood can widen the distribution of adhesion forces, which are essential for data interpretation. When a common Si AFM tip with nanometre size is used, the influence of tip wear can be significant. Therefore, control experiments should take the sequence of measurements into consideration, e.g. repeated experiments with used tip. In comparison, colloidal tips provide highly reproducible results. Similar average values but different distributions are shown for the adhesion measured on two major components of wood surface (cell wall and lumen). Evidence supports the hypothesis that the difference of the adhesion force distribution on these two locations was mainly induced by their surface roughness.

  15. Adhesion force mapping on wood by atomic force microscopy: influence of surface roughness and tip geometry

    NASA Astrophysics Data System (ADS)

    Jin, X.; Kasal, B.

    2016-10-01

    This study attempts to address the interpretation of atomic force microscopy (AFM) adhesion force measurements conducted on the heterogeneous rough surface of wood and natural fibre materials. The influences of wood surface roughness, tip geometry and wear on the adhesion force distribution are examined by cyclic measurements conducted on wood surface under dry inert conditions. It was found that both the variation of tip and surface roughness of wood can widen the distribution of adhesion forces, which are essential for data interpretation. When a common Si AFM tip with nanometre size is used, the influence of tip wear can be significant. Therefore, control experiments should take the sequence of measurements into consideration, e.g. repeated experiments with used tip. In comparison, colloidal tips provide highly reproducible results. Similar average values but different distributions are shown for the adhesion measured on two major components of wood surface (cell wall and lumen). Evidence supports the hypothesis that the difference of the adhesion force distribution on these two locations was mainly induced by their surface roughness.

  16. Capillary force on a tilted cylinder: Atomic Force Microscope (AFM) measurements.

    PubMed

    Kosgodagan Acharige, Sébastien; Laurent, Justine; Steinberger, Audrey

    2017-11-01

    The capillary force in situations where the liquid meniscus is asymmetric, such as the one around a tilted object, has been hitherto barely investigated even though these situations are very common in practice. In particular, the capillary force exerted on a tilted object may depend on the dipping angle i. We investigate experimentally the capillary force that applies on a tilted cylinder as a function of its dipping angle i, using a home-built tilting Atomic Force Microscope (AFM) with custom made probes. A micrometric-size rod is glued at the end of an AFM cantilever of known stiffness, whose deflection is measured when the cylindrical probe is dipped in and retracted from reference liquids. We show that a torque correction is necessary to understand the measured deflection. We give the explicit expression of this correction as a function of the probes' geometrical parameters, so that its magnitude can be readily evaluated. The results are compatible with a vertical capillary force varying as 1/cosi, in agreement with a recent theoretical prediction. Finally, we discuss the accuracy of the method for measuring the surface tension times the cosine of the contact angle of the liquid on the probe. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Atomic force microscopy detects changes in the interaction forces between GroEL and substrate proteins.

    PubMed Central

    Vinckier, A; Gervasoni, P; Zaugg, F; Ziegler, U; Lindner, P; Groscurth, P; Plückthun, A; Semenza, G

    1998-01-01

    The structure of the Escherichia coli chaperonin GroEL has been investigated by tapping-mode atomic force microscopy (AFM) under liquid. High-resolution images can be obtained, which show the up-right position of GroEL adsorbed on mica with the substrate-binding site on top. Because of this orientation, the interaction between GroEL and two substrate proteins, citrate synthase from Saccharomyces cerevisiae with a destabilizing Gly-->Ala mutation and RTEM beta-lactamase from Escherichia coli with two Cys-->Ala mutations, could be studied by force spectroscopy under different conditions. The results show that the interaction force decreases in the presence of ATP (but not of ATPgammaS) and that the force is smaller for native-like proteins than for the fully denatured ones. It also demonstrates that the interaction energy with GroEL increases with increasing molecular weight. By measuring the interaction force changes between the chaperonin and the two different substrate proteins, we could specifically detect GroEL conformational changes upon nucleotide binding. PMID:9635779

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

    PubMed

    Weber, Stefan A L; Kilpatrick, Jason I; Brosnan, Timothy M; Jarvis, Suzanne P; Rodriguez, Brian J

    2014-05-02

    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.

  19. An open source/real-time atomic force microscope architecture to perform customizable force spectroscopy experiments.

    PubMed

    Materassi, Donatello; Baschieri, Paolo; Tiribilli, Bruno; Zuccheri, Giampaolo; Samorì, Bruno

    2009-08-01

    We describe the realization of an atomic force microscope architecture designed to perform customizable experiments in a flexible and automatic way. Novel technological contributions are given by the software implementation platform (RTAI-LINUX), which is free and open source, and from a functional point of view, by the implementation of hard real-time control algorithms. Some other technical solutions such as a new way to estimate the optical lever constant are described as well. The adoption of this architecture provides many degrees of freedom in the device behavior and, furthermore, allows one to obtain a flexible experimental instrument at a relatively low cost. In particular, we show how such a system has been employed to obtain measures in sophisticated single-molecule force spectroscopy experiments [Fernandez and Li, Science 303, 1674 (2004)]. Experimental results on proteins already studied using the same methodologies are provided in order to show the reliability of the measure system.

  20. Microrheology of growing Escherichia coli biofilms investigated by using magnetic force modulation atomic force microscopy.

    PubMed

    Gan, Tiansheng; Gong, Xiangjun; Schönherr, Holger; Zhang, Guangzhao

    2016-12-01

    Microrheology of growing biofilms provides insightful information about its structural evolution and properties. In this study, the authors have investigated the microrheology of Escherichia coli (strain HCB1) biofilms at different indentation depth (δ) by using magnetic force modulation atomic force microscopy as a function of disturbing frequency (f). As δ increases, the dynamic stiffness (ks) for the biofilms in the early stage significantly increases. However, it levels off when the biofilms are matured. The facts indicate that the biofilms change from inhomogeneous to homogeneous in structure. Moreover, ks is scaled to f, which coincides with the rheology of soft glasses. The exponent increases with the incubation time, indicating the fluidization of biofilms. In contrast, the upper layer of the matured biofilms is solidlike in that the storage modulus is always larger than the loss modulus, and its viscoelasticity is slightly influenced by the shear stress.

  1. Development of Tuning Fork Based Probes for Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Jalilian, Romaneh; Yazdanpanah, Mehdi M.; Torrez, Neil; Alizadeh, Amirali; Askari, Davood

    2014-03-01

    This article reports on the development of tuning fork-based AFM/STM probes in NaugaNeedles LLC for use in atomic force microscopy. These probes can be mounted on different carriers per customers' request. (e.g., RHK carrier, Omicron carrier, and tuning fork on a Sapphire disk). We are able to design and engineer tuning forks on any type of carrier used in the market. We can attach three types of tips on the edge of a tuning fork prong (i.e., growing Ag2Ga nanoneedles at any arbitrary angle, cantilever of AFM tip, and tungsten wire) with lengths from 100-500 μm. The nanoneedle is located vertical to the fork. Using a suitable insulation and metallic coating, we can make QPlus sensors that can detect tunneling current during the AFM scan. To make Qplus sensors, the entire quartz fork will be coated with an insulating material, before attaching the nanoneedle. Then, the top edge of one prong is coated with a thin layer of conductive metal and the nanoneedle is attached to the fork end of the metal coated prong. The metal coating provides electrical connection to the tip for tunneling current readout and to the electrodes and used to read the QPlus current. Since the amount of mass added to the fork is minimal, the resonance frequency spectrum does not change and still remains around 32.6 KHz and the Q factor is around 1,200 in ambient condition. These probes can enhance the performance of tuning fork based atomic microscopy.

  2. Minimizing tip-sample forces and enhancing sensitivity in atomic force microscopy with dynamically compliant cantilevers

    NASA Astrophysics Data System (ADS)

    Keyvani, Aliasghar; Sadeghian, Hamed; Tamer, Mehmet Selman; Goosen, Johannes Frans Loodewijk; van Keulen, Fred

    2017-06-01

    Due to the harmonic motion of the cantilever in Tapping Mode Atomic Force Microscopy, it is seemingly impossible to estimate the tip-sample interactions from the motion of the cantilever. Not directly observing the interaction force, it is possible to damage the surface or the tip by applying an excessive mechanical load. The tip-sample interactions scale with the effective stiffness of the probe. Thus, the reduction of the mechanical load is usually limited by the manufacturability of low stiffness probes. However, the one-to-one relationship between spring constant and applied force only holds when higher modes of the cantilever are not excited. In this paper, it is shown that, by passively tuning higher modes of the cantilever, it is possible to reduce the peak repulsive force. These tuned probes can be dynamically more compliant than conventional probes with the same static spring constant. Both theoretical and experimental results show that a proper tuning of dynamic modes of cantilevers reduces the contact load and increases the sensitivity considerably. Moreover, due to the contribution of higher modes, the tuned cantilevers provide more information on the tip-sample interaction. This extra information from the higher harmonics can be used for mapping and possibly identification of material properties of samples.

  3. Conductive transparent fiber probes for shear-force atomic force microscopes.

    PubMed

    Murashita, Tooru

    2006-01-01

    New conductive transparent (CT) probes that can inject currents into nanometer-sized regions and collect light from them have been developed for shear-force atomic force microscopy (SF-AFM) of partially isolative regions. The CT probe consists of a straight elastic silica fiber with one end tapered to a point. The taper is coated with an indium-tin-oxide film as a transparent electrode, and the probe apex has a nanometer-scale radius. The essential feature of the CT probes is coaxial nickel plating on the shaft of the isolative silica fiber, which is adjusted to obtain suitable elasticity for smooth shear-force feedback as well as for supplying currents to the transparent electrode. Experimental results clarified that nickel thickness between 0.5 and 15 microm on 20 mm-long fibers makes resistance low enough for supplying current to the probe apex and also makes the Q curves smooth enough for shear-force feedback. Clear SF-AFM and current images were successfully obtained for a sample containing both conductive and isolative regions. The CT probes for SF-AFM can expand applications of probe-current-induced luminescence measurements to samples that contain highly resistive and isolative regions, for which scanning tunneling microscopy cannot be applied.

  4. Segmented nanofibers of spider dragline silk: Atomic force microscopy and single-molecule force spectroscopy

    PubMed Central

    Oroudjev, E.; Soares, J.; Arcidiacono, S.; Thompson, J. B.; Fossey, S. A.; Hansma, H. G.

    2002-01-01

    Despite its remarkable materials properties, the structure of spider dragline silk has remained unsolved. Results from two probe microscopy techniques provide new insights into the structure of spider dragline silk. A soluble synthetic protein from dragline silk spontaneously forms nanofibers, as observed by atomic force microscopy. These nanofibers have a segmented substructure. The segment length and amino acid sequence are consistent with a slab-like shape for individual silk protein molecules. The height and width of nanofiber segments suggest a stacking pattern of slab-like molecules in each nanofiber segment. This stacking pattern produces nano-crystals in an amorphous matrix, as observed previously by NMR and x-ray diffraction of spider dragline silk. The possible importance of nanofiber formation to native silk production is discussed. Force spectra for single molecules of the silk protein demonstrate that this protein unfolds through a number of rupture events, indicating a modular substructure within single silk protein molecules. A minimal unfolding module size is estimated to be around 14 nm, which corresponds to the extended length of a single repeated module, 38 amino acids long. The structure of this spider silk protein is distinctly different from the structures of other proteins that have been analyzed by single-molecule force spectroscopy, and the force spectra show correspondingly novel features. PMID:11959907

  5. Characterization of English ivy ( Hedera helix) adhesion force and imaging using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Xia, Lijin; Lenaghan, Scott C.; Zhang, Mingjun; Wu, Yu; Zhao, Xiaopeng; Burris, Jason N.; Neal Stewart, C.

    2011-03-01

    English ivy ( Hedera helix) is well known for its ability to climb onto and strongly adhere to a variety of solid substrates. It has been discovered that the ivy aerial rootlet secretes an adhesive composed of polysaccharide and spherical nanoparticles. This study aims to characterize the mechanical properties of the nanocomposite adhesive using atomic force microscopy (AFM). The adhesive was first imaged by AFM to visualize the nanocomposite. Mechanical properties were then determined at various time points, from secretion to hardening. The experimental results indicate that the ivy adhesive exhibited strong adhesion strength and high elasticity. There was a decrease in adhesive force over time, from 298 to 202 nN during the 24-h study. Accompanying with it were the limited changes in extension length and Young's modulus. The limited curing process of the ivy adhesive helps fill gaps in the attaching surface, leading to more intimate contact and increased van der Waals interactions with the surface. However, study based on a mechanical model indicated that van der Waals force alone is not significant enough to account for all of the measured force. Other chemical interactions and cross linking likely contribute to the strong adhesion strength of ivy.

  6. Noncontact estimation of intercellular breaking force using a femtosecond laser impulse quantified by atomic force microscopy.

    PubMed

    Hosokawa, Yoichiroh; Hagiyama, Man; Iino, Takanori; Murakami, Yoshinori; Ito, Akihiko

    2011-02-01

    When a femtosecond laser pulse (fsLP) is focused through an objective lens into a culture medium, an impulsive force (fsLP-IF) is generated that propagates from the laser focal point (O(f)) in a micron-sized space. This force can detach individual adherent cells without causing considerable cell damage. In this study, an fsLP-IF was reflected in the vibratory movement of an atomic force microscopy (AFM) cantilever. Based on the magnitude of the vibration and the geometrical relationship between O(f) and the cantilever, the fsLP-IF generated at O(f) was calculated as a unit of impulse [N-s]. This impulsive force broke adhesion molecule-mediated intercellular interactions in a manner that depended on the adhesion strength that was estimated by the cell aggregation assay. The force also broke the interactions between streptavidin-coated microspheres and a biotin-coated substrate with a measurement error of approximately 7%. These results suggest that fsLP-IF can be used to break intermolecular and intercellular interactions and estimate the adhesion strength. The fsLP-IF was used to break intercellular contacts in two biologically relevant cultures: a coculture of leukocytes seeded over on an endothelial cell monolayer, and a polarized monolayer culture of epithelial cells. The impulses needed to break leukocyte-endothelial and interepithelial interactions, which were calculated based on the geometrical relationship between O(f) and the adhesive interface, were on the order of 10(-13) and 10(-12) N-s, respectively. When the total impulse at O(f) is well-defined, fsLP-IF can be used to estimate the force required to break intercellular adhesions in a noncontact manner under biologically relevant conditions.

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

    PubMed

    Tran Khac, Bien Cuong; Chung, Koo-Hyun

    2016-02-01

    Atomic Force Microscopy (AFM) has been widely used for measuring friction force at the nano-scale. However, one of the key challenges faced by AFM researchers is to calibrate an AFM system to interpret a lateral force signal as a quantifiable force. In this study, five rectangular cantilevers were used to quantitatively compare three different lateral force calibration methods to demonstrate the legitimacy and to establish confidence in the quantitative integrity of the proposed methods. The Flat-Wedge method is based on a variation of the lateral output on a surface with flat and changing slopes, the Multi-Load Pivot method is based on taking pivot measurements at several locations along the cantilever length, and the Lateral AFM Thermal-Sader method is based on determining the optical lever sensitivity from the thermal noise spectrum of the first torsional mode with a known torsional spring constant from the Sader method. The results of the calibration using the Flat-Wedge and Multi-Load Pivot methods were found to be consistent within experimental uncertainties, and the experimental uncertainties of the two methods were found to be less than 15%. However, the lateral force sensitivity determined by the Lateral AFM Thermal-Sader method was found to be 8-29% smaller than those obtained from the other two methods. This discrepancy decreased to 3-19% when the torsional mode correction factor for an ideal cantilever was used, which suggests that the torsional mode correction should be taken into account to establish confidence in Lateral AFM Thermal-Sader method. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    PubMed Central

    Burggraf, Larry W.; Xing, Yun

    2016-01-01

    ABSTRACT The study of structures and properties of bacterial spores is important to understanding spore formation and biological responses to environmental stresses. While significant progress has been made over the years in elucidating the multilayer architecture of spores, the mechanical properties of the spore interior are not known. Here, we present a thermal atomic force microscopy (AFM) study of the nanomechanical properties of internal structures of Bacillus anthracis spores. We developed a nanosurgical sectioning method in which a stiff diamond AFM tip was used to cut an individual spore, exposing its internal structure, and a soft AFM tip was used to image and characterize the spore interior on the nanometer scale. We observed that the elastic modulus and adhesion force, including their thermal responses at elevated temperatures, varied significantly in different regions of the spore section. Our AFM images indicated that the peptidoglycan (PG) cortex of Bacillus anthracis spores consisted of rod-like nanometer-sized structures that are oriented in the direction perpendicular to the spore surface. Our findings may shed light on the spore architecture and properties. IMPORTANCE A nanosurgical AFM method was developed that can be used to probe the structure and properties of the spore interior. The previously unknown ultrastructure of the PG cortex of Bacillus anthracis spores was observed to consist of nanometer-sized rod-like structures that are oriented in the direction perpendicular to the spore surface. The variations in the nanomechanical properties of the spore section were largely correlated with its chemical composition. Different components of the spore materials showed different thermal responses at elevated temperatures. PMID:26969703

  9. Uncertainty quantification in nanomechanical measurements using the atomic force microscope

    NASA Astrophysics Data System (ADS)

    Wagner, Ryan; Moon, Robert; Pratt, Jon; Shaw, Gordon; Raman, Arvind

    2011-11-01

    Quantifying uncertainty in measured properties of nanomaterials is a prerequisite for the manufacture of reliable nanoengineered materials and products. Yet, rigorous uncertainty quantification (UQ) is rarely applied for material property measurements with the atomic force microscope (AFM), a widely used instrument that can measure properties at nanometer scale resolution of both inorganic and biological surfaces and nanomaterials. We present a framework to ascribe uncertainty to local nanomechanical properties of any nanoparticle or surface measured with the AFM by taking into account the main uncertainty sources inherent in such measurements. We demonstrate the framework by quantifying uncertainty in AFM-based measurements of the transverse elastic modulus of cellulose nanocrystals (CNCs), an abundant, plant-derived nanomaterial whose mechanical properties are comparable to Kevlar fibers. For a single, isolated CNC the transverse elastic modulus was found to have a mean of 8.1 GPa and a 95% confidence interval of 2.7-20 GPa. A key result is that multiple replicates of force-distance curves do not sample the important sources of uncertainty, which are systematic in nature. The dominant source of uncertainty is the nondimensional photodiode sensitivity calibration rather than the cantilever stiffness or Z-piezo calibrations. The results underscore the great need for, and open a path towards, quantifying and minimizing uncertainty in AFM-based material property measurements of nanoparticles, nanostructured surfaces, thin films, polymers and biomaterials. This work is a partial contribution of the USDA Forest Service and NIST, agencies of the US government, and is not subject to copyright.

  10. Forced translocation of DNA hairpins through a tight molecular nanopore studied by atomic force microscopy in force-spectroscopy mode

    NASA Astrophysics Data System (ADS)

    Ashcroft, Brian Alan

    The transit of Deoxyribonucleic acid (DNA) through a molecular nanopore has been studied by pulling a beta-cyclodextrin ring over single stranded DNA using an atomic force microscope. After an exhaustive search, it was determined that n-propyl silane surface provides the most reliable background surface for performing force spectroscopy of DNA. A versatile rotaxane complex was formed between a hydrophobic molecule and cyclodextrin. DNA was then added to this complex to form a DNA rotaxane. The cyclodextrin is covalently linked by a molecular tether to the force probe, which both pulls on the cyclodextrin and reads off the forces required for passage of the DNA. The bases do not provide an obstacle to the passage of the cyclodextrin, but hairpins represent large barriers to transit, and analysis of the pulling kinetics show the opening rates of the hairpins. The utility of the system was determined by investigating the kinetics of the analogous biological system with two unusual hairpins: Unusually stable hairpins (consisting of the bases CTTG in the loop) and sequences with CTG repeats motifs. CTTG hairpins prove to be completely impassable both to reverse transcriptase and the cyclodextrin, while CTG repeats pass with an ease appropriate to their bulk measurements, but still enough force to stall a polymerase enzyme proving that the kinetic analysis is alone responsible for the stalling.

  11. Harnessing bifurcations in tapping-mode atomic force microscopy to calibrate time-varying tip-sample force measurements.

    PubMed

    Sahin, Ozgur

    2007-10-01

    Torsional harmonic cantilevers allow measurement of time-varying tip-sample forces in tapping-mode atomic force microscopy. Accuracy of these force measurements is important for quantitative nanomechanical measurements. Here we demonstrate a method to convert the torsional deflection signals into a calibrated force wave form with the use of nonlinear dynamical response of the tapping cantilever. Specifically the transitions between steady oscillation regimes are used to calibrate the torsional deflection signals.

  12. Ab initio simulation of atomic-scale imaging in noncontact atomic force microscopy.

    PubMed

    Caciuc, V; Hölscher, H

    2009-07-01

    In this paper, we summarize some results of our ab initio simulations aimed at investigating the mechanism of the NC-AFM image contrast on semiconductor and metallic surfaces. We start with an introduction into the basic ideas behind the ab initio simulation process of the NC-AFM experimental results. Our simulations reveal that the interaction of a clean silicon tip with a semiconductor surface like InAs(110) might lead to bond-formation and bond-breaking processes during the approach and retraction of the tip. This imaging mechanism is very similar to that observed on a metallic surface like Ag(110). Interestingly, a clean silicon tip can become contaminated with Ag surface atoms. On both types of surface we observe a significant energy dissipation which is caused by a hysteresis in the tip-sample force curves calculated on the approach and retraction path.

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

    PubMed Central

    2011-01-01

    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. PMID:21711623

  14. High-throughput atomic force microscopes operating in parallel

    NASA Astrophysics Data System (ADS)

    Sadeghian, Hamed; Herfst, Rodolf; Dekker, Bert; Winters, Jasper; Bijnagte, Tom; Rijnbeek, Ramon

    2017-03-01

    Atomic force microscopy (AFM) is an essential nanoinstrument technique for several applications such as cell biology and nanoelectronics metrology and inspection. The need for statistically significant sample sizes means that data collection can be an extremely lengthy process in AFM. The use of a single AFM instrument is known for its very low speed and not being suitable for scanning large areas, resulting in a very-low-throughput measurement. We address this challenge by parallelizing AFM instruments. The parallelization is achieved by miniaturizing the AFM instrument and operating many of them simultaneously. This instrument has the advantages that each miniaturized AFM can be operated independently and that the advances in the field of AFM, both in terms of speed and imaging modalities, can be implemented more easily. Moreover, a parallel AFM instrument also allows one to measure several physical parameters simultaneously; while one instrument measures nano-scale topography, another instrument can measure mechanical, electrical, or thermal properties, making it a lab-on-an-instrument. In this paper, a proof of principle of such a parallel AFM instrument has been demonstrated by analyzing the topography of large samples such as semiconductor wafers. This nanoinstrument provides new research opportunities in the nanometrology of wafers and nanolithography masks by enabling real die-to-die and wafer-level measurements and in cell biology by measuring the nano-scale properties of a large number of cells.

  15. Atomic force microscopy as a novel pharmacological tool.

    PubMed

    Pereira, R S

    2001-10-15

    With the advent of the atomic force microscope (AFM), the study of biological samples has become more realistic because, in most cases, samples are not covered or fixed, which makes it possible to observe them while the cells are alive. This advantage of the AFM allowed the advent of a new invention: nanobiosensors using the cantilever (probe) of the AFM and, in this case, it is possible to observe the entering or exiting of specific molecules (including medications) from living cells. This is the smallest biosensor in the world, measuring about 100 microm long (about the width of a hair). Beyond sensing the area of interest with this biosensor, it is also possible to see the area and exactly what is occurring on it, in real time. This new tool will be very useful for several areas: molecular pharmacology, enzymology, physiology, molecular biology, biotechnology, biophysics, physical chemistry, analytical chemistry, and organic chemistry. This article discusses, mainly, the applications of this new technique to the field of pharmacology.

  16. Atomic Force Microscopy of Arrays of Asymmetrical DNA Motifs

    SciTech Connect

    Sherman, W.B.; Mudalige, T.K.

    2012-03-21

    DNA can easily be assembled into wide and relatively flat nanostructures that lend themselves to study via Atomic Force Microscopy (AFM). It is often important to know which side of an assembly the AFM is imaging. This is particularly crucial for characterizing nanomachines, where the movement must be measured relative to fiducial features visible to the AFM. We have developed a cheap and simple technique for building DNA arrays with distinguishable sides, a technique requiring 10 or fewer strands - dozens or hundreds of strands fewer than used for these purposes previously. Our approach involves constructing arrays out of DNA tiles that have low apparent symmetry when imaged via AFM. We have surveyed the effects of varying degrees of motif asymmetry in AFM micrographs. Even at resolutions where the individual tiles cannot be resolved (either because of sub-optimal tip quality, or very gentle tapping by the AFM tip) the larger scale features of the arrays have predictable structures that allow the determination of which side of the array is facing up. We have used this information to verify that DNA hairpins attached to either the up- or down-facing side of an array on mica can be detected in AFM height scans. We have also characterized differences in appearance between hairpins attached to different sides of the arrays.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  18. Visualization of Cytoskeletal Elements by the Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Berdyyeva, Tamara; Woodworth, Craig; Sokolov, Igor

    2004-03-01

    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 liquids 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 3 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 electron microscopy.

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

    SciTech Connect

    Torello, D.; Degertekin, F. Levent

    2013-11-15

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

  20. Quantification of red blood cells using atomic force microscopy.

    PubMed

    O'Reilly, M; McDonnell, L; O'Mullane, J

    2001-01-01

    For humans the sizes and shapes of their red blood cells are important indicators of well being. In this study, the feasibility of using the atomic force microscope (AFM) to provide the sizes and shapes of red blood cells has been investigated. An immobilisation procedure has been developed that enabled red blood cells to be reliably imaged by contact AFM in air. The shapes of the red blood cells were readily apparent in the AFM images. Various cell quantification parameters were investigated, including thickness, width, surface area and volume. Excellent correlation was found between the AFM-derived immobilised mean cell volume (IMCV) parameter and the mean cell volume (MCV) parameter used in current haematological practice. The correlation between MCV and IMCV values has validated the immobilisation procedure by demonstrating that the significant cell shrinkage that occurs during immobilisation and drying does not introduce quantification artifacts. Reliable IMCV values were obtained by quantifying 100 red blood cells and this typically required 3-5 AFM images of 100 microm x 100 microm area. This work has demonstrated that the AFM can provide in a single test the red blood cell size and shape data needed in the assessment of human health.

  1. Lipid domains in supported lipid bilayer for atomic force microscopy.

    PubMed

    Lin, Wan-Chen; Blanchette, Craig D; Ratto, Timothy V; Longo, Marjorie L

    2007-01-01

    Phase-separated supported lipid bilayers have been widely used to study the phase behavior of multicomponent lipid mixtures. One of the primary advantages of using supported lipid bilayers is that the two-dimensional platform of this model membrane system readily allows lipid-phase separation to be characterized by high-resolution imaging techniques such as atomic force microscopy (AFM). In addition, when supported lipid bilayers have been functionalized with a specific ligand, protein-membrane interactions can also be imaged and characterized through AFM. It has been recently demonstrated that when the technique of vesicle fusion is used to prepare supported lipid bilayers, the thermal history of the vesicles before deposition and the supported lipid bilayers after formation will have significant effects on the final phase-separated domain structures. In this chapter, three methods of vesicle preparations as well as three deposition conditions will be presented. Also, the techniques and strategies of using AFM to image multicomponent phase-separated supported lipid bilayers and protein binding will be discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  3. Nanochannel system fabricated by MEMS microfabrication and atomic force microscopy.

    PubMed

    Wang, Z; Wang, D; Jiao, N; Tung, S; Dong, Z

    2011-12-01

    A silicon nanochannel system with integrated transverse electrodes was designed and fabricated by combining micro-electro-mechanical systems (MEMS) micromachining and atomic force microscopy (AFM)-based nanolithography. The fabrication process began with the patterning of microscale reservoirs and electrodes on an oxidised silicon chip using conventional MEMS techniques. A nanochannel, approximately 30 [micro sign]m long with a small semi-circular cross-sectional area of 20 nm × 200 nm, was then mechanically machined on the oxide surface between the micro reservoirs by applying AFM nanolithography with an all-diamond probe. Anodic bonding was used to seal off the nanochannel with a matching Pyrex cover. Continuous flow in the nanochannel was verified by pressurising a solution of fluorescein isothiocyanate in ethanol through the nanochannel in a vacuum chamber. It was further demonstrated by translocating negatively charged nanobeads (diameter approximately 20 nm) through the nanochannel by using an external DC electric field. The passage of the nanobeads caused a sharp increase in the transverse electrical conductivity of the nanochannel.

  4. Research on three dimensional machining effects using atomic force microscope

    NASA Astrophysics Data System (ADS)

    Mao, Yao-Ting; Kuo, Kai-Chen; Tseng, Ching-En; Huang, Jian-Yin; Lai, Yi-Chih; Yen, Jia-Yush; Lee, Chih-Kung; Chuang, Wei-Li

    2009-06-01

    This research studies the use of scanning probe microscope as the tool to manufacture three dimensional nanoscale objects. We modified a commercial atomic force microscope (AFM) and replaced the original probe control system with a personal computer (PC) based controller. The modified system used the scanning probe in the AFM for the cutting tool and used the PC controller to control work piece. With the new controller, one could implement multiaxes motion control to perform trajectory planning and to test various cutting strategies. The experiments discovered that the debris can coalesce with the sample material and cause tremendous problem in the nanomachining process. This research thus proposed to make use of this material and developed a piling algorithm to not only cut but also pile up the debris in a favorable way for steric shaping. The experimental results showed that the proposed cutting and shaping algorithm can produce nano-objects as high as a few hundred nanometers. The probe tip typically wears down to around 500 μm diameter after the machining process, putting a limit on the machining resolution. The vertical resolution can achieve less than 10 nm without controlled environment.

  5. Characterization of healthy and fluorotic enamel by atomic force microscopy.

    PubMed

    Zavala-Alonso, Verónica; Martínez-Castanon, Gabriel A; Patiño-Marín, Nuria; Terrones, Humberto; Anusavice, Kenneth; Loyola-Rodríguez, Juan P

    2010-10-01

    The aim was to characterize the external structure, roughness, and absolute depth profile (ADP) of fluorotic enamel compared with healthy enamel. Eighty extracted human molars were classified into four groups [TFI: 0, control (C); 1-3, mild (MI); 4-5, moderate (MO); 6-9, severe fluorosis (S)] according to the Thylstrup-Fejerskov Index (TFI). All samples were analyzed by atomic force microscopy.The mean values of enamel surface roughness (ESR) in nm were: Group C, 92.6; Group MI, 188.8; Group MO, 246.9; and Group S, 532.2. The mean values of absolute depth profile in nm were: C, 1,065.7; MI, 2,360.7; MO, 2,536.7; and S, 6,146.2. The differences between mean ESR and mean ADP among groups were statistically significant (p < 0.05). This structural study confirms at the nanometer level that there is a positive association between fluorosis severity, ESR, and ADP, and there is an association with the clinical findings of fluorosis measured by TFI as well.

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

    NASA Astrophysics Data System (ADS)

    Torello, D.; Degertekin, F. Levent

    2013-11-01

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

  7. Tooth structure studied using the atomic force microscope

    NASA Astrophysics Data System (ADS)

    Kasas, Sandor; Berdal, Ariane; Celio, Marco R.

    1993-06-01

    We used the atomic force microscope (AFM) to observe structure of the tooth, both rat and human. The rigidity and the surface flatness of thin sections of this mineralized tissue, allow us to attain good resolution with the AFM. As enamel contains uniquely large crystals of hydroxyapatite it can be investigated at high resolution. Tooth enamel and thin slices of undecalcified developing tooth germs from 2 - 12 day old rats were observed, embedded in acrylic resin (Lowicryl K4M). In addition, as orthophosphoric acid is widely used clinically to etch tooth enamel before restoring with composites, we studied its action at pH2 on the tooth surface during 1 hour of exposition. Hydroxyapatite crystals and collagen fibers were seen in the tooth slices observed in air, and the classical structure of the enamel was visible. The etched enamel surface under liquid, showed dramatic differences to that imaged in air. Modifications to the surface were also seen during exposure to the acid.

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

    PubMed

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

    2014-01-01

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

  9. Atomic force microscopy investigation of the giant mimivirus

    SciTech Connect

    Kuznetsov, Yuri G.; Xiao Chuan; Sun Siyang; Raoult, Didier; Rossmann, Michael; McPherson, Alexander

    2010-08-15

    Mimivirus was investigated by atomic force microscopy in its native state following serial degradation by lysozyme and bromelain. The 750-nm diameter virus is coated with a forest of glycosylated protein fibers of lengths about 140 nm with diameters 1.4 nm. Fibers are capped with distinctive ellipsoidal protein heads of estimated Mr = 25 kDa. The surface fibers are attached to the particle through a layer of protein covering the capsid, which is in turn composed of the major capsid protein (MCP). The latter is organized as an open network of hexagonal rings with central depressions separated by 14 nm. The virion exhibits an elaborate apparatus at a unique vertex, visible as a star shaped depression on native particles, but on defibered virions as five arms of 50 nm width and 250 nm length rising above the capsid by 20 nm. The apparatus is integrated into the capsid and not applied atop the icosahedral lattice. Prior to DNA release, the arms of the star disengage from the virion and it opens by folding back five adjacent triangular faces. A membrane sac containing the DNA emerges from the capsid in preparation for fusion with a membrane of the host cell. Also observed from disrupted virions were masses of distinctive fibers of diameter about 1 nm, and having a 7-nm periodicity. These are probably contained within the capsid along with the DNA bearing sac. The fibers were occasionally observed associated with toroidal protein clusters interpreted as processive enzymes modifying the fibers.

  10. Nanoscale observation of organic thin film by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Mochizuki, Shota; Uruma, Takeshi; Satoh, Nobuo; Saravanan, Shanmugam; Soga, Tetsuo

    2017-08-01

    Organic photovoltaics (OPVs) fabricated using organic semiconductors and hybrid solar cells (HSCs) based on organic semiconductors/quantum dots (QDs) have been attracting significant attention owing to their potential use in low-cost solar energy-harvesting applications and flexible, light-weight, colorful, large-area devices. In this study, we observed and evaluated the surface of a photoelectric conversion layer (active layer) of the OPVs and HSCs based on phenyl-C61-butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT), and zinc oxide (ZnO) nanoparticles. The experiment was performed using atomic force microscopy (AFM) combined with a frequency modulation detector (FM detector) and a contact potential difference (CPD) detection circuit. We experimentally confirmed the changes in film thickness and surface potential, as affected by the ZnO nanoparticle concentration. From the experimental results, we confirmed that ZnO nanoparticles possibly affect the structures of PCBM and P3HT. Also, we prepared an energy band diagram on the basis of the observation results, and analyzed the energy distribution inside the active layer.

  11. Cellular effects of magnetic nanoparticles explored by atomic force microscopy.

    PubMed

    Mao, Hongli; Li, Jingchao; Dulińska-Molak, Ida; Kawazoe, Naoki; Takeda, Yoshihiko; Mamiya, Hiroaki; Chen, Guoping

    2015-09-01

    The investigation of subtle change of cells exposed to nanomaterials is extremely essential but also challenging for nanomaterial-based biological applications. In this study, atomic force microscopy (AFM) was employed to investigate the effects of iron-iron oxide core-shell magnetic nanoparticles on the mechanical properties of bovine articular chondrocytes (BACs). After being exposed to the nanoparticles even at a high nanoparticle-concentration (50 μg mL(-1)), no obvious difference was observed by using conventional methods, including the WST-1 assay and live/dead staining. However a significant difference of Young's modulus of the cells was detected by AFM even when the concentration of nanoparticles applied in the cell culture medium was low (10 μg mL(-1)). The difference of cellular Young's modulus increased with the increase of nanoparticle concentration. AFM was demonstrated to be a useful tool to identify the subtle change of cells when they were exposed to nanomaterials even at a low concentration.

  12. Atomic force microscopy of differential weathering in real time

    SciTech Connect

    Heaton, J.S.; Engstrom, R.C. . Dept. of Chemistry)

    1994-04-01

    Differential weathering of a rock sample was observed in-situ using atomic force microscopy (AFM). The sample contained fayalite intergrown with veins of magnetite and serpentine. Analyses consisted of polishing the sample with alumina and recording AFM scans periodically during subsequent exposure to nitric acid. Immediately after polishing, serpentine areas were recessed compared to fayalite and magnetite, which were similar in height. As weathering proceeded, both serpentine and magnetite areas protruded from the fayalite surface, and no significant change in the relative heights of magnetite and serpentine features was observed. This suggests that serpentine is less resistant to mechanical weathering than fayalite or magnetite but that serpentine and magnetite are both more resistant to chemical weathering than fayalite. Differential weathering rates between fayalite and magnetite, on the order of a few unit cells per minute, were determined in various nitric acid concentrations by measuring the difference in height between the two minerals as a function of time. A dissolution rate law for fayalite was determined by comparing the rates for different concentrations of nitric acid and assuming the dissolution of magnetite was negligible compared to that of fayalite. The rate law from this study is Rate = 7.7* [HNO[sub 3

  13. Atomic force microscope cantilever calibration using a focused ion beam.

    PubMed

    Slattery, Ashley D; Quinton, Jamie S; Gibson, Christopher T

    2012-07-20

    A calibration method is presented for determining the spring constant of atomic force microscope (AFM) cantilevers, which is a modification of the established Cleveland added mass technique. A focused ion beam (FIB) is used to remove a well-defined volume from a cantilever with known density, substantially reducing the uncertainty usually present in the added mass method. The technique can be applied to any type of AFM cantilever; but for the lowest uncertainty it is best applied to silicon cantilevers with spring constants above 0.7 N m(-1), where uncertainty is demonstrated to be typically between 7 and 10%. Despite the removal of mass from the cantilever, the calibration method presented does not impair the probes' ability to acquire data. The technique has been extensively tested in order to verify the underlying assumptions in the method. This method was compared to a number of other calibration methods and practical improvements to some of these techniques were developed, as well as important insights into the behavior of FIB modified cantilevers. These results will prove useful to research groups concerned with the application of microcantilevers to nanoscience, in particular for cases where maintaining pristine AFM tip condition is critical.

  14. Recent Progress in Molecular Recognition Imaging Using Atomic Force Microscopy.

    PubMed

    Senapati, Subhadip; Lindsay, Stuart

    2016-03-15

    Atomic force microscopy (AFM) is an extremely powerful tool in the field of bionanotechnology because of its ability to image single molecules and make measurements of molecular interaction forces with piconewton sensitivity. It works in aqueous media, enabling studies of molecular phenomenon taking place under physiological conditions. Samples can be imaged in their near-native state without any further modifications such as staining or tagging. The combination of AFM imaging with the force measurement added a new feature to the AFM technique, that is, molecular recognition imaging. Molecular recognition imaging enables mapping of specific interactions between two molecules (one attached to the AFM tip and the other to the imaging substrate) by generating simultaneous topography and recognition images (TREC). Since its discovery, the recognition imaging technique has been successfully applied to different systems such as antibody-protein, aptamer-protein, peptide-protein, chromatin, antigen-antibody, cells, and so forth. Because the technique is based on specific binding between the ligand and receptor, it has the ability to detect a particular protein in a mixture of proteins or monitor a biological phenomenon in the native physiological state. One key step for recognition imaging technique is the functionalization of the AFM tips (generally, silicon, silicon nitrides, gold, etc.). Several different functionalization methods have been reported in the literature depending on the molecules of interest and the material of the tip. Polyethylene glycol is routinely used to provide flexibility needed for proper binding as a part of the linker that carries the affinity molecule. Recently, a heterofunctional triarm linker has been synthesized and successfully attached with two different affinity molecules. This novel linker, when attached to AFM tip, helped to detect two different proteins simultaneously from a mixture of proteins using a so-called "two

  15. Carbon Nanotube Devices Engineered by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Prisbrey, Landon

    This dissertation explores the engineering of carbon nanotube electronic devices using atomic force microscopy (AFM) based techniques. A possible application for such devices is an electronic interface with individual biological molecules. This single molecule biosensing application is explored both experimentally and with computational modeling. Scanning probe microscopy techniques, such as AFM, are ideal to study nanoscale electronics. These techniques employ a probe which is raster scanned above a sample while measuring probe-surface interactions as a function of position. In addition to topographical and electrostatic/magnetic surface characterization, the probe may also be used as a tool to manipulate and engineer at the nanoscale. Nanoelectronic devices built from carbon nanotubes exhibit many exciting properties including one-dimensional electron transport. A natural consequence of onedimensional transport is that a single perturbation along the conduction channel can have extremely large effects on the device's transport characteristics. This property may be exploited to produce electronic sensors with single-molecule resolution. Here we use AFM-based engineering to fabricate atomic-sized transistors from carbon nanotube network devices. This is done through the incorporation of point defects into the carbon nanotube sidewall using voltage pulses from an AFM probe. We find that the incorporation of an oxidative defect leads to a variety of possible electrical signatures including sudden switching events, resonant scattering, and breaking of the symmetry between electron and hole transport. We discuss the relationship between these different electronic signatures and the chemical structure/charge state of the defect. Tunneling through a defect-induced Coulomb barrier is modeled with numerical Verlet integration of Schrodinger's equation and compared with experimental results. Atomic-sized transistors are ideal for single-molecule applications due to their

  16. Graphene-coated atomic force microscope tips for reliable nanoscale electrical characterization.

    PubMed

    Lanza, M; Bayerl, A; Gao, T; Porti, M; Nafria, M; Jing, G Y; Zhang, Y F; Liu, Z F; Duan, H L

    2013-03-13

    Graphene single-layer films are grown by chemical vapor deposition and transferred onto commercially available conductive tips for atomic force microscopy. Graphene-coated tips are much more resistant to both high currents and frictions than commercially available, metal-varnished, conductive atomic force microscopy tips, leading to much larger lifetimes and more reliable imaging due to a lower tip-sample interaction.

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

    PubMed Central

    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 current study, atomic force expressions for geometry-dependent multipoles are presented for use in simulations of flexible molecules. The atomic forces are derived by first proposing a new general expression for Wigner function derivatives ∂Dlm′m/∂Ω. The force equations can be applied to electrostatic models based on atomic point multipoles or Gaussian multipole charge density. Hydrogen bonded dimers are used to test the inter-molecular electrostatic energies and atomic forces calculated by geometry-dependent multipoles fit to the ab initio electrostatic potential (ESP). The electrostatic energies and forces are compared to their reference ab initio values. It is shown that both static and geometry-dependent multipole models are able to reproduce total molecular forces and torques with respect to ab initio, while geometry-dependent multipoles are needed to reproduce ab initio atomic forces. The expressions for atomic force can be used in simulations of flexible molecules with atomic multipoles. In addition, the results presented in this work should lead to further development of next generation force fields composed of geometry-dependent multipole models. PMID:20839297

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  19. Surface charge mapping of solid surfaces in water by pulsed-force-mode atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Miyatani, T.; Okamoto, S.; Rosa, A.; Marti, O.; Fujihira, M.

    We have studied the lateral distribution of charges on various surfaces in water by measuring the electrical double layer forces between a Si3N4 atomic force microscope (AFM) tip and the surfaces. By increasing the pH of the solution around the isoelectric point (IEP) of Si3N4 of approximately 6, the charge on the Si3N4 AFM tip was changed from positive to negative. The surface charges of the samples were also controlled by the pH of the solution in which the sample oxides were dipped. When the samples were electronically conductive, the surface charge was controlled by the electrode potentials. When the sample surface was heterogeneous in terms of the isoelectric point or point of zero charge (pzc), the surface charge was changed from one place to the other. As a heterogeneous oxide sample, a quartz plate patterned with alumina was used. The lateral charge distributions on such surfaces were mapped by pulsed-force-mode AFM. The lateral resolution of the present method was found to be approximately 20 nm.

  20. Indirect modulation of nonmagnetic probes for force modulation atomic force microscopy.

    PubMed

    Li, Jie-Ren; Garno, Jayne C

    2009-02-15

    Frequency-dependent changes for phase and amplitude images are demonstrated with test platforms of organosilane ring patterns, using force modulation atomic force microscopy (FM-AFM) with an alternate instrument configuration. The imaging setup using indirect magnetic modulation (IMM) is based on indirect oscillation of soft, nonmagnetic cantilevers, with spring constants <1 N m(-1). The tip is driven to vibrate by the motion of a tip holder assembly which contains ferromagnetic materials. The entire tip assembly is induced to vibrate with the flux of an external ac electromagnetic field, supplied by a wire coil solenoid placed underneath the sample plate. With the use of IMM, dynamic parameters of the driving frequencies and amplitude of the tip motion can be optimized to sensitively map the elastic response of samples. An advantage of this instrument setup is that a magnetic coating is not required to drive the periodic oscillation of the tip. The instrument configuration for IMM may not be practical for intermittent imaging modes, which often work best with stiff cantilevers. However, indirect actuation provides an effective approach for imaging with low force setpoints and is well-suited for dynamic AFM modes using continuous contact imaging.

  1. Bichromatic force on metastable argon for atom-trap trace analysis

    NASA Astrophysics Data System (ADS)

    Feng, Z.; Ebser, S.; Ringena, L.; Ritterbusch, F.; Oberthaler, M. K.

    2017-07-01

    For an efficient performance of atom-trap trace analysis, it is important to collimate the particles emitted from an effusive source. Their high velocity limits the interaction time with the cooling laser. Therefore, forces beyond the limits of the scattering force are desirable. The bichromatic force is a promising candidate for this purpose which is demonstrated here on metastable argon-40. The precollimated atoms are deflected in one dimension and the acquired Doppler shift is detected by absorption spectroscopy. With the experimentally accessible parameters, it was possible to measure a force three times stronger than the scattering force. Systematic studies on its dependence on Rabi frequency, phase difference, and detuning to atomic resonance are compared to the solution of the optical Bloch equations. We anticipate predictions for a possible application in atom-trap trace analysis of argon-39 and other noble gas experiments, where a high flux of metastable atoms is needed.

  2. Casimir Forces and Quantum Friction from Ginzburg Radiation in Atomic Bose-Einstein Condensates.

    PubMed

    Marino, Jamir; Recati, Alessio; Carusotto, Iacopo

    2017-01-27

    We theoretically propose an experimentally viable scheme to use an impurity atom in an atomic Bose-Einstein condensate, in order to realize condensed-matter analogs of quantum vacuum effects. In a suitable atomic level configuration, the collisional interaction between the impurity atom and the density fluctuations in the condensate can be tailored to closely reproduce the electric-dipole coupling of quantum electrodynamics. By virtue of this analogy, we recover and extend the paradigm of electromagnetic vacuum forces to the domain of cold atoms, showing in particular the emergence, at supersonic atomic speeds, of a novel power-law scaling of the Casimir force felt by the atomic impurity, as well as the occurrence of a quantum frictional force, accompanied by the Ginzburg emission of Bogoliubov quanta. Observable consequences of these quantum vacuum effects in realistic spectroscopic experiments are discussed.

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

    PubMed

    Gross, Leo; Mohn, Fabian; Moll, Nikolaj; Liljeroth, Peter; Meyer, Gerhard

    2009-08-28

    Resolving individual atoms has always been the ultimate goal of surface microscopy. The scanning tunneling microscope images atomic-scale features on surfaces, but resolving single atoms within an adsorbed molecule remains a great challenge because the tunneling current is primarily sensitive to the local electron density of states close to the Fermi level. We demonstrate imaging of molecules with unprecedented atomic resolution by probing the short-range chemical forces with use of noncontact atomic force microscopy. The key step is functionalizing the microscope's tip apex with suitable, atomically well-defined terminations, such as CO molecules. Our experimental findings are corroborated by ab initio density functional theory calculations. Comparison with theory shows that Pauli repulsion is the source of the atomic resolution, whereas van der Waals and electrostatic forces only add a diffuse attractive background.

  4. Casimir Forces and Quantum Friction from Ginzburg Radiation in Atomic Bose-Einstein Condensates

    NASA Astrophysics Data System (ADS)

    Marino, Jamir; Recati, Alessio; Carusotto, Iacopo

    2017-01-01

    We theoretically propose an experimentally viable scheme to use an impurity atom in an atomic Bose-Einstein condensate, in order to realize condensed-matter analogs of quantum vacuum effects. In a suitable atomic level configuration, the collisional interaction between the impurity atom and the density fluctuations in the condensate can be tailored to closely reproduce the electric-dipole coupling of quantum electrodynamics. By virtue of this analogy, we recover and extend the paradigm of electromagnetic vacuum forces to the domain of cold atoms, showing in particular the emergence, at supersonic atomic speeds, of a novel power-law scaling of the Casimir force felt by the atomic impurity, as well as the occurrence of a quantum frictional force, accompanied by the Ginzburg emission of Bogoliubov quanta. Observable consequences of these quantum vacuum effects in realistic spectroscopic experiments are discussed.

  5. Sublattice identification in noncontact atomic force microscopy of the NaCl(001) surface

    SciTech Connect

    Hoffmann, R.; Weiner, D.; Schirmeisen, A.; Foster, A. S.

    2009-09-15

    We compare the three-dimensional force field obtained from frequency-distance measurements above the NaCl(001) surface to atomistic calculations using various tip models. In the experiments, long-range forces cause a total attractive force even on the similarly charged site. Taking force differences between two sites minimizes the influence of such long-range forces. The magnitude of the measured force differences are by a factor of 6.5-10 smaller than the calculated forces. This is an indication that for the particular tip used in this experiment several atoms of the tip interact with the surface atoms at close tip-sample distances. The interaction of these additional atoms with the surface is small at the imaging distance, because symmetric images are obtained. The force distance characteristics resemble those of a negative tip apex ion which could be explained, e.g., by a neutral Si tip.

  6. AtomicJ: an open source software for analysis of force curves.

    PubMed

    Hermanowicz, Paweł; Sarna, Michał; Burda, Kvetoslava; Gabryś, Halina

    2014-06-01

    We present an open source Java application for analysis of force curves and images recorded with the Atomic Force Microscope. AtomicJ supports a wide range of contact mechanics models and implements procedures that reduce the influence of deviations from the contact model. It generates maps of mechanical properties, including maps of Young's modulus, adhesion force, and sample height. It can also calculate stacks, which reveal how sample's response to deformation changes with indentation depth. AtomicJ analyzes force curves concurrently on multiple threads, which allows for high speed of analysis. It runs on all popular operating systems, including Windows, Linux, and Macintosh.

  7. AtomicJ: An open source software for analysis of force curves

    SciTech Connect

    Hermanowicz, Paweł Gabryś, Halina; Sarna, Michał; Burda, Kvetoslava

    2014-06-15

    We present an open source Java application for analysis of force curves and images recorded with the Atomic Force Microscope. AtomicJ supports a wide range of contact mechanics models and implements procedures that reduce the influence of deviations from the contact model. It generates maps of mechanical properties, including maps of Young's modulus, adhesion force, and sample height. It can also calculate stacks, which reveal how sample's response to deformation changes with indentation depth. AtomicJ analyzes force curves concurrently on multiple threads, which allows for high speed of analysis. It runs on all popular operating systems, including Windows, Linux, and Macintosh.

  8. AtomicJ: An open source software for analysis of force curves

    NASA Astrophysics Data System (ADS)

    Hermanowicz, Paweł; Sarna, Michał; Burda, Kvetoslava; Gabryś, Halina

    2014-06-01

    We present an open source Java application for analysis of force curves and images recorded with the Atomic Force Microscope. AtomicJ supports a wide range of contact mechanics models and implements procedures that reduce the influence of deviations from the contact model. It generates maps of mechanical properties, including maps of Young's modulus, adhesion force, and sample height. It can also calculate stacks, which reveal how sample's response to deformation changes with indentation depth. AtomicJ analyzes force curves concurrently on multiple threads, which allows for high speed of analysis. It runs on all popular operating systems, including Windows, Linux, and Macintosh.

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

    NASA Astrophysics Data System (ADS)

    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

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

    SciTech Connect

    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

  11. First-Principles Calculation of Femtosecond Symmetry-Breaking Atomic Forces in Photoexcited Bismuth

    NASA Astrophysics Data System (ADS)

    Murray, Éamonn D.; Fahy, Stephen

    2015-02-01

    We present a first-principles method for the calculation of the polarization-dependent atomic forces resulting from optical excitation in a solid. We calculate the induced force driving the Eg phonon mode in bismuth immediately after absorption of polarized light. When radiation with polarization perpendicular to the c axis is absorbed, the photoexcited charge density breaks the threefold rotational symmetry, leading to an atomic force component perpendicular to the axis. We calculate the initial excited electronic distribution as a function of photon energy and polarization and find the resulting atomic force components parallel and perpendicular to the axis. The magnitude of the calculated force is in excellent agreement with that derived from recent measurements of the amplitude of Eg atomic motion and the decay time of several femtoseconds for the driving force.

  12. Optical Forces from Periodic Adiabatic Rapid Passage Sequences on Metastable Helium Atoms

    NASA Astrophysics Data System (ADS)

    Stack, Daniel Thomas

    Over the past 30 years, optical manipulation of neutral atoms has been primarily performed with a monochromatic laser beam. The simplest tool for the control of atomic motion is the radiative force exerted by a monochromatic laser on a two-level atom. The radiative force arises from absorption followed by spontaneous emission, and its magnitude is limited by the atom's excited state lifetime. The coherent momentum exchanges between light fields and atoms can be exploited to produce long-range optical forces much greater than the radiative force through the use of absorption-stimulated emission processes. Adiabatic Rapid Passage (ARP) is a long-existing method to invert the population of a two-level nuclear spin system. Its extension to the optical domain necessitates a frequency chirped light pulse to interact with a two-level atom via the dipole interaction. I will first present a numerical study of the properties of optical forces on moving atoms derived from purely stimulated processes produced by multiple ARP sequences. This will be followed by experimental observations of long-range ARP forces much larger than the radiative force in metastable helium. Sequences of properly timed laser pulses may be used for rapid deceleration of neutral atomic (or molecular) beams.

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

    SciTech Connect

    Rezaei, E.; Turner, J. A.

    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.

  14. Lens capsule structure assessed with atomic force microscopy

    PubMed Central

    Sueiras, Vivian M.; Moy, Vincent T.

    2015-01-01

    Purpose To image the ultrastructure of the anterior lens capsule at the nanoscale level using atomic force microscopy (AFM). Methods Experiments were performed on anterior lens capsules maintained in their in situ location surrounding the lens from six human cadavers (donor age range: 44–88 years), four cynomolgus monkeys (Macaca fascicularis age range: 4.83–8.92 years), and seven pigs (<6 months). Hydration of all samples was maintained using Dulbecco’s Modified Eagle Medium (DMEM). Whole lenses were removed from the eye and placed anterior side up in agarose gel before gel hardening where only the posterior half of the lens was contained within the gel. After the gel hardened, the Petri dish was filled with DMEM until the point where the intact lens was fully submerged. AFM was used to image the anterior lens surface in contact mode. An integrated analysis program was used to calculate the interfibrillar spacing, fiber diameter, and surface roughness of the samples. Results The AFM images depict a highly ordered fibrous structure at the surface of the lens capsule in all three species. The interfibrillar spacing for the porcine, cynomolgus monkey, and human lens capsules was 0.68±0.25, 1.80±0.39, and 1.08±0.25 μm, respectively. In the primate, interfibrillar spacing significantly decreased linearly as a function of age. The fiber diameters ranged from 50 to 950 nm. Comparison of the root mean square (RMS) and average deviation demonstrate that the surface of the porcine lens capsule is the smoothest, and that the human and cynomolgus monkey capsules are significantly rougher. Conclusions AFM was successful in providing high-resolution images of the nanostructure of the lens capsule samples. Species-dependent differences were observed in the overall structure and surface roughness. PMID:25814829

  15. Autopilot for frequency-modulation atomic force microscopy.

    PubMed

    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.

  16. Autopilot for frequency-modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Kent, Ronald D; Vikesland, Peter J

    2012-07-03

    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.

  18. Dimensional characterization of extracellular vesicles using atomic force microscopy

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  19. Autopilot for frequency-modulation atomic force microscopy

    SciTech Connect

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri

    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.

  20. High-speed atomic force microscopy and peak force tapping control

    NASA Astrophysics Data System (ADS)

    Hu, Shuiqing; Mininni, Lars; Hu, Yan; Erina, Natalia; Kindt, Johannes; Su, Chanmin

    2012-03-01

    ITRS Roadmap requires defect size measurement below 10 nanometers and challenging classifications for both blank and patterned wafers and masks. Atomic force microscope (AFM) is capable of providing metrology measurement in 3D at sub-nanometer accuracy but has long suffered from drawbacks in throughput and limitation of slow topography imaging without chemical information. This presentation focus on two disruptive technology developments, namely high speed AFM and quantitative nanomechanical mapping, which enables high throughput measurement with capability of identifying components through concurrent physical property imaging. The high speed AFM technology has allowed the imaging speed increase by 10-100 times without loss of the data quality. Such improvement enables the speed of defect review on a wafer to increase from a few defects per hour to nearly 100 defects an hour, approaching the requirements of ITRS Roadmap. Another technology development, Peak Force Tapping, substantially simplified the close loop system response, leading to self-optimization of most challenging samples groups to generate expert quality data. More importantly, AFM also simultaneously provides a series of mechanical property maps with a nanometer spatial resolution during defect review. These nanomechanical maps (including elastic modulus, hardness, and surface adhesion) provide complementary information for elemental analysis, differentiate defect materials by their physical properties, and assist defect classification beyond topographic measurements. This paper will explain the key enabling technologies, namely high speed tip-scanning AFM using innovative flexure design and control algorithm. Another critical element is AFM control using Peak Force Tapping, in which the instantaneous tip-sample interaction force is measured and used to derive a full suite of physical properties at each imaging pixel. We will provide examples of defect review data on different wafers and media disks

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

  3. Investigation of Acoustic Fields Generated by Eddy Currents Using an Atomic Force Microscope (Postprint)

    DTIC Science & Technology

    2012-08-01

    AFRL-RX-WP-JA-2014-0230 INVESTIGATION OF ACOUSTIC FIELDS GENERATED BY EDDY CURRENTS USING AN ATOMIC FORCE MICROSCOPE (POSTPRINT) V...Institute of Physics AIR FORCE RESEARCH LABORATORY MATERIALS AND MANUFACTURING DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7750 AIR... FORCE MATERIEL COMMAND UNITED STATES AIR FORCE NOTICE AND SIGNATURE PAGE Using Government drawings, specifications, or other data included in

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

    PubMed

    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.

  5. Application of evanescent wave optics to the determination of absolute distance in surface force measurements using the atomic force microscope.

    PubMed

    Huntington, S T; Hartley, P G; Katsifolis, J

    2003-04-01

    A combined scanning near field optical/atomic force microscope (AFM) is used to obtain surface force measurements between a near field sensing tip and a tapered optical fibre surface, whilst simultaneously detecting the intensity of the evanescent field emanating from the fibre. The tapered optical fibre acts as a compliant sample to demonstrate the possible use of the near field intensity measurement system in determining 'real' surface separations from normal AFM surface force measurements at sub-nanometer resolution between deformable surfaces.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Atomic force microscope measurements of long-range forces near lipid-coated surfaces in electrolytes.

    PubMed Central

    Xu, W; Blackford, B L; Cordes, J G; Jericho, M H; Pink, D A; Levadny, V G; Beveridge, T

    1997-01-01

    The interaction of DMPC (L-alpha-dimyristoyl-1,2-diterradecanoyl-sn-glycero-3-phosphoch oli ne, C36H72NO8P) lipid-coated Si3N4 surfaces immersed in an electrolyte was investigated with an atomic force microscope. A long-range interaction was observed, even when the Si3N4 surfaces were covered with nominally neutral lipid layers. The interaction was attributed to Coulomb interactions of charges located at the lipid surface. The experimental force curves were compared with solutions for the linearized as well as with exact solutions of the Poisson-Boltzmann equation. The comparison suggested that in 0.5 mM KCl electrolyte the DMPC lipids carried about one unit of charge per 100 lipid molecules. The presence of this surface charge made it impossible to observe an effective charge density recently predicted for dipole layers near a dielectric when immersed in an electrolyte. A discrepancy between the theoretical results and the data at short separations was interpreted in terms of a decrease in the surface charge with separation distance. Images FIGURE 2 PMID:9138586

  8. Anharmonicity, solvation forces, and resolution in atomic force microscopy at the solid-liquid interface

    NASA Astrophysics Data System (ADS)

    Voïtchovsky, Kislon

    2013-08-01

    Solid-liquid interfaces are central to nanoscale science and technology and control processes as diverse as self-assembly, heterogeneous catalysis, wetting, electrochemistry, or protein function. Experimentally, measuring the structure and dynamics of solid-liquid interfaces with molecular resolution remains a challenge. This task can, in principle, be achieved with atomic force microscopy (AFM), which functions locally, and with nanometer precision. When operated dynamically and at small amplitudes, AFM can provide molecular-level images of the liquid solvation layers at the interfaces. At larger amplitudes, results in the field of multifrequency AFM have shown that anharmonicities in the tip motion can provide quantitative information about the solid's mechanical properties. The two approaches probe opposite aspects of the interface and are generally seen as distinct. Here it is shown that, for amplitudes Aforces. For A>d, the tip trajectory becomes rapidly anharmonic due to the tip tapping the solid, and the resolution decreases. A nonlinear transition between the two regimes occurs for A˜d and can be quantified with the second harmonic of the tip oscillation. These results, confirmed by computer simulations, remain valid in most experimental conditions. Significantly, they provide an objective criterion to enhance resolution and to decide whether the results are dominated by the properties of the solid or of the liquid.

  9. Imaging and Force Recognition of Single Molecular Behaviors Using Atomic Force Microscopy

    PubMed Central

    Li, Mi; Dang, Dan; Liu, Lianqing; Xi, Ning; Wang, Yuechao

    2017-01-01

    The advent of atomic force microscopy (AFM) has provided a powerful tool for investigating the behaviors of single native biological molecules under physiological conditions. AFM can not only image the conformational changes of single biological molecules at work with sub-nanometer resolution, but also sense the specific interactions of individual molecular pair with piconewton force sensitivity. In the past decade, the performance of AFM has been greatly improved, which makes it widely used in biology to address diverse biomedical issues. Characterizing the behaviors of single molecules by AFM provides considerable novel insights into the underlying mechanisms guiding life activities, contributing much to cell and molecular biology. In this article, we review the recent developments of AFM studies in single-molecule assay. The related techniques involved in AFM single-molecule assay were firstly presented, and then the progress in several aspects (including molecular imaging, molecular mechanics, molecular recognition, and molecular activities on cell surface) was summarized. The challenges and future directions were also discussed. PMID:28117741

  10. Mapping the interaction sites of Mucin 1 and DNA aptamer by atomic force microscopy.

    PubMed

    Wang, Nan; Zhang, Miaomiao; Chen, Xuejuan; Ma, Xingxing; Li, Chen; Zhang, Zhe; Tang, Jilin

    2017-10-09

    Mucin 1 (MUC1) is an attractive tumor marker for cancer diagnosis. An advanced atomic force microscopy (AFM) mode, peak-force tapping AFM with an aptamer functionalized tip, was introduced to map the specific interaction sites of an aptamer and MUC1. Single molecular force spectroscopy (SMFS) was used to investigate dynamic parameters of the aptamer-MUC1.

  11. Relaxation of a simulated lipid bilayer vesicle compressed by an atomic force microscope

    NASA Astrophysics Data System (ADS)

    Barlow, Ben M.; Bertrand, Martine; Joós, Béla

    2016-11-01

    Using coarse-grained molecular dynamics simulations, we study the relaxation of bilayer vesicles, uniaxially compressed by an atomic force microscope cantilever. The relaxation time exhibits a strong force dependence. Force-compression curves are very similar to recent experiments wherein giant unilamellar vesicles were compressed in a nearly identical manner.

  12. The Atomic Force Microscopic (AFM) Characterization of Nanomaterials

    DTIC Science & Technology

    2009-06-01

    the first intramolecular field effect transistors (FETs). Additionally, the first intramolecular logic gate utilizing SWNT FETs has recently become...magnetic force microscope (MFM)), Casimir forces, solvation forces, etc. In addition to these forces, other quantities could also be simultaneously...crystals may be employed, with each responsible for scanning in the x, y and z directions. This eliminates some of the distortion effects seen with a

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

    SciTech Connect

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

    2002-01-01

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

  14. Nanoscale Characterization of Fault Roughness by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Thom, C.; Brodsky, E. E.; Goldsby, D. L.; Candela, T.; Carpick, R. W.

    2015-12-01

    Frictional properties of laboratory and natural fault surfaces are controlled by the collective behavior of microscopic asperity contacts. A fundamental parameter that determines the spatial distribution and average size of asperity contacts on a fault surface is the roughness at all length scales. Average contact sizes for laboratory friction experiments are inferred to be of order 1 to 10 μm, but contact sizes on natural faults are comparatively unknown. Previous studies have quantified surface roughness of exhumed faults over length scales of microns to tens of meters, but roughness at sub-micron length scales has rarely been determined. For length scales of tens of microns and larger, self-affine roughness is observed, exhibiting anisotropic scaling with a Hurst exponent of 0.6 in the slip-parallel direction and 0.8 in the slip-perpendicular direction (Candela et al., 2012). Using intermittent contact atomic force microscopy (AFM), we have probed natural fault surfaces over profile lengths as large as ~100 μm with nanometer resolution in the slip-parallel and slip-perpendicular directions and sub-nanometer resolution in the third dimension. Surface roughness at length scales of tens of microns and smaller also demonstrates a self-affine character, but characterized by a Hurst exponent of 0.7 in both the slip-parallel and slip-perpendicular directions, in contrast to the different slip-parallel and slip-perpendicular values cited above. Taken together, our data and existing roughness data for several other faults demonstrate self-affine geometry over ~13 orders of magnitude in lateral length scale, to scales as small as 10 nm. Roughness measurements in the sub-micron regime allow us to use contact theory to estimate the real area of contact, the mean pressure, and the distribution of contact stresses on a rough fault surface. Calculations using our measured roughness show that contact stresses for asperities microns and smaller in size are large enough to

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

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

    PubMed

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

    2015-04-01

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

  17. Thermal Casimir-Polder forces on a V-type three-level atom

    NASA Astrophysics Data System (ADS)

    Xu, Chen-Ran; Xu, Jing-Ping; Al-amri, M.; Zhu, Cheng-Jie; Xie, Shuang-Yuan; Yang, Ya-Ping

    2017-09-01

    We study the thermal Casimir-Polder (CP) forces on a V-type three-level atom. The competition between the thermal effect and the quantum interference of the two transition dipoles on the force is investigated. To shed light onto the role of the quantum interference, we analyze two kinds of initial states of the atom, i.e., the superradiant state and the subradiant state. Considering the atom being in the thermal reservoir, the resonant CP force arising from the real photon emission dominates in the evolution of the CP force. Under the zero-temperature condition, the quantum interference can effectively modify the amplitude and the evolution of the force, leading to a long-time force or even the cancellation of the force. Our results reveal that in the finite-temperature case, the thermal photons can enhance the amplitude of all force elements, but have no influence on the net resonant CP force in the steady state, which means that the second law of thermodynamics still works. For the ideal degenerate V-type atom with parallel dipoles under the initial subradiant state, the robust destructive quantum interference overrides the thermal fluctuations, leading to the trapping of the atom in the subradiant state and the disappearance of the CP force. However, in terms of a realistic Zeeman atom, the thermal photons play a significant role during the evolution of the CP force. The thermal fluctuations can enhance the amplitude of the initial CP force by increasing the temperature, and weaken the influence of the quantum interference on the evolution of the CP force from the initial superradiant (subradiant) state to the steady state.

  18. Atomic structure of InSb(001) and GaAs(001) surfaces imaged with noncontact atomic force microscopy.

    PubMed

    Kolodziej, J J; Such, B; Szymonski, M; Krok, F

    2003-06-06

    Noncontact atomic force microscopy (NC-AFM) has been used to study the c(8x2) InSb(001) and the c(8x2) GaAs(001) surfaces prepared by sputter cleaning and annealing. Atomically resolved tip-surface interaction maps display different characteristic patterns depending on the tip front atom type. It is shown that representative AFM maps can be interpreted consistently with the most recent structural model of A(III)B(V)(001) surface, as corresponding to the A(III) sublattice, to the B(V) sublattice, or to the combination of both sublattices.

  19. Surface roughtness and its influence on particle adhesion using atomic force microscope techniques

    SciTech Connect

    Gady, B.; Schaefer, D.; Reifenberger, R.; Rimai, D.; DeMejo, L.P.

    1996-12-31

    The surface force interactions between individual 8 {mu}m diameter spheres and atomically flat substrates have been systematically investigated using atomic force techniques. The lift-off force of glass, polystyrene and tin particles from atomically smooth mica and highly oriented pyrolytic graphite substrates was determined as a function of the applied loading force in an inert nitrogen environment. While the relative magnitudes of the measured lift-off force was found to scale as expected between the various systems studied, the absolute values were a factor of {approximately}50 smaller than expected from the Johnson, Kendall, and Roberts theory. The surface topography of representative spheres was characterized with atomic force microscopy, allowing a quantitative assessment of the role that surface roughness plays in the adhesion of micrometer-size particles to substrates. Taking into account the radius of curvature of the asperities measured from the atomic force scans, agreement between the measured and theoretical estimates for the lift-off forces was improved, with the corrected experimental forces about a factor of 3 smaller than theoretical expectations.

  20. Theoretical Study of the Effect of Probe Shape on Adhesion Force Between Probe and Substrate in Atomic Force Microscope Experiment

    NASA Astrophysics Data System (ADS)

    Yang, Li; Hu, Junhui; Kong, Lingjiang

    2013-12-01

    The quantitative description of adhesion force dependence on the probe shape is of importance in many scientific and industrial fields. We performed a theoretical study on the influences of the probe shape (the sphere and parabolic probe) on the adhesion force at different humidity in order to elucidate how the adhesion force varied with the probe shape in atomic force microscope manipulation experiment. We found that the combined action of the triple point and the Kelvin radius is the guiding trend of the adhesion force, and these two fundamental parameters are closely related to the probe shape. Meanwhile, the theoretical results demonstrated that the adhesion force are in a good agreement with the experiment data if the van der Waals force is take into account.

  1. Accurate formula for conversion of tunneling current in dynamic atomic force spectroscopy

    NASA Astrophysics Data System (ADS)

    Sader, John E.; Sugimoto, Yoshiaki

    2010-07-01

    Recent developments in frequency modulation atomic force microscopy enable simultaneous measurement of frequency shift and time-averaged tunneling current. Determination of the interaction force is facilitated using an analytical formula, valid for arbitrary oscillation amplitudes [Sader and Jarvis, Appl. Phys. Lett. 84, 1801 (2004)]. Here we present the complementary formula for evaluation of the instantaneous tunneling current from the time-averaged tunneling current. This simple and accurate formula is valid for any oscillation amplitude and current law. The resulting theoretical framework allows for simultaneous measurement of the instantaneous tunneling current and interaction force in dynamic atomic force microscopy.

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

    PubMed

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

    2014-09-16

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

  3. Obtaining of images of ordered and disordered nanocrystal structures by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Parfenov, P. S.; Litvin, A. P.; Ushakova, E. V.; Fedorov, A. V.; Baranov, A. V.

    2017-01-01

    The morphology of films, superlattices, and other structures of colloidal nanocrystals has been investigated by atomic force microscopy (AFM). The capabilities of ultrasharp and conventional probes for AFM are compared. The problems of detection of nanocrystal close packing are discussed.

  4. Combined X-ray Microfluorescence and Atomic Force Microscopy Studies of Mg Distribution in Whole Cells

    SciTech Connect

    Lagomarsino, S.; Farruggia, G.; Trapani, V.; Mastrototaro, L.; Wolf, F.; Cedola, A.; Fratini, M.; Notargiacomo, A.; Bukreeva, I.; McNulty, I.; Vogt, S.; Kim, S.; Legnini, D.; Maier, J. A. M.

    2011-09-09

    We present in this paper a novel methodology that combines scanning x-ray fluorescencee microscopy and atomic force microscopy. The combination of these two techniques allows the determination of a concentration map of Mg in whole (not sectioned) cells.

  5. The Effects of Orthophosphate in Drinking Water on the Initial Copper Corrosion Using Atomic Force Microscopy

    EPA Science Inventory

    Corroding of copper piping used in household drinking water plumbing may potentially impacts consumer’s health and economics. Copper corrosion studies conducted on newly corroding material with atomic force microscopy (AFM) may be particularly useful in understanding the impact ...

  6. The Effects of Orthophosphate in Drinking Water on the Initial Copper Corrosion Using Atomic Force Microscopy

    EPA Science Inventory

    Corroding of copper piping used in household drinking water plumbing may potentially impacts consumer’s health and economics. Copper corrosion studies conducted on newly corroding material with atomic force microscopy (AFM) may be particularly useful in understanding the impact ...

  7. Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing.

    PubMed

    Vanommeslaeghe, K; MacKerell, A D

    2012-12-21

    Molecular mechanics force fields are widely used in computer-aided drug design for the study of drug-like molecules alone or interacting with biological systems. In simulations involving biological macromolecules, the biological part is typically represented by a specialized biomolecular force field, while the drug is represented by a matching general (organic) force field. In order to apply these general force fields to an arbitrary drug-like molecule, functionality for assignment of atom types, parameters, and charges is required. In the present article, which is part I of a series of two, we present the algorithms for bond perception and atom typing for the CHARMM General Force Field (CGenFF). The CGenFF atom typer first associates attributes to the atoms and bonds in a molecule, such as valence, bond order, and ring membership among others. Of note are a number of features that are specifically required for CGenFF. This information is then used by the atom typing routine to assign CGenFF atom types based on a programmable decision tree. This allows for straightforward implementation of CGenFF's complicated atom typing rules and for equally straightforward updating of the atom typing scheme as the force field grows. The presented atom typer was validated by assigning correct atom types on 477 model compounds including in the training set as well as 126 test-set molecules that were constructed to specifically verify its different components. The program may be utilized via an online implementation at https://www.paramchem.org/ .

  8. Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing

    PubMed Central

    Vanommeslaeghe, K.; MacKerell, A. D.

    2012-01-01

    Molecular mechanics force fields are widely used in computer-aided drug design for the study of drug-like molecules alone or interacting with biological systems. In simulations involving biological macromolecules, the biological part is typically represented by a specialized biomolecular force field, while the drug is represented by a matching general (organic) force field. In order to apply these general force fields to an arbitrary drug-like molecule, functionality for assignment of atom types, parameters and charges is required. In the present article, which is part I of a series of two, we present the algorithms for bond perception and atom typing for the CHARMM General Force Field (CGenFF). The CGenFF atom typer first associates attributes to the atoms and bonds in a molecule, such as valence, bond order, and ring membership among others. Of note are a number of features that are specifically required for CGenFF. This information is then used by the atom typing routine to assign CGenFF atom types based on a programmable decision tree. This allows for straightforward implementation of CGenFF’s complicated atom typing rules and for equally straightforward updating of the atom typing scheme as the force field grows. The presented atom typer was validated by assigning correct atom types on 477 model compounds including in the training set as well as 126 test-set molecules that were constructed to specifically verify its different components. The program may be utilized via an online implementation at https://www.paramchem.org/. PMID:23146088

  9. Evaluation of interactive forces between alkaline earth metal fluoride particles and single crystal substrate using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Tsai, Yi-Yang; Nalladega, Vijay; Sathish, Shamachary; Stanford, Malcolm K.

    2004-07-01

    Interactive forces between particles play an important role in diverse fields of science and technology. With the advent of Atomic Force Microscopy, investigation of interactive forces has been extended to micro and nano-scale particles with new applications. These forces are known to vary with the dimension of the particles and with the different levels of humidity. In the present paper we have investigated the interactive forces between a spherical particle probes of eutectic BaF2-CaF2 and a single crystal surface of CaF2 using an Atomic Force Microscope. The effect of humidity on the interactive forces has been examined by analyzing the force-displacement curves at controlled levels of humidity. Force distance curves obtained with two different probes, 5 μm and 17 μm in diameter, and have been examined to investigate the effect of probe dimensions. The results are discussed in view of the application of eutectic BaF2-CaF2 particles in self-lubricating coatings for aerospace applications.

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

    PubMed

    Gross, Leo; Mohn, Fabian; Liljeroth, Peter; Repp, Jascha; Giessibl, Franz J; Meyer, Gerhard

    2009-06-12

    Charge states of atoms can be investigated with scanning tunneling microscopy, but this method requires a conducting substrate. We investigated the charge-switching of individual adsorbed gold and silver atoms (adatoms) on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force microscope (AFM) operated at 5 kelvin with oscillation amplitudes in the subangstrom regime. Charging of a gold atom by one electron charge increases the force on the AFM tip by a few piconewtons. Moreover, the local contact potential difference is shifted depending on the sign of the charge and allows the discrimination of positively charged, neutral, and negatively charged atoms. The combination of single-electron charge sensitivity and atomic lateral resolution should foster investigations of molecular electronics, photonics, catalysis, and solar photoconversion.

  11. Surface force measurements at kaolinite edge surfaces using atomic force microscopy.

    PubMed

    Liu, Jing; Sandaklie-Nikolova, Linda; Wang, Xuming; Miller, Jan D

    2014-04-15

    Fundamental results obtained from research on the properties of the edge surfaces of kaolinite particles (~500 nm) are reported. Of particular significance was the development of the experimental protocol. Well-ordered kaolinite edge surfaces were prepared as an epoxy resin sandwich structure having layered kaolinite particles in the center of the epoxy resin sandwich. Images of the sectioned kaolinite edge surfaces were examined by atomic force microscopy (AFM), and the average thickness of kaolinite particles in this study was determined to be 38.3 nm±11.7 nm. Furthermore, the surface charge of the kaolinite edge surfaces was evaluated with a super sharp Si tip. The point of zero charge (PZC) of the kaolinite edge surface was determined to be below pH 4, in contrast to the traditional view that the edge surfaces of kaolinite particles may carry a positive charge at pH 4. This lower PZC of the kaolinite edge surface was attributed to the lack of isomorphous substitution in the silica tetrahedral layer when compared to the PZC for the muscovite edge surface. Our results are consistent with the particle aggregation and flotation behavior of kaolinite, and should provide the basis for improved flotation strategies leading to the efficient recovery and utilization of mineral and energy resources. Copyright © 2013 Elsevier Inc. All rights reserved.

  12. Wafer scale tilt-compensated silicon nanowire atomic force microscopy probes for high aspect ratio geometries

    NASA Astrophysics Data System (ADS)

    Bryce, Brian A.; Ilic, B. Robert; Reuter, Mark C.; Tiwari, Sandip

    2014-09-01

    Using site controlled growth of single vapor-liquid-solid silicon nanowires, high aspect ratio tilt-compensated atomic force microscope probes are fabricated on a wafer scale. Methods are developed to sculpt the tips of these probes for desirable performance attributes. Probe performance is explored by imaging high aspect ratio structures using an atomic force microscope. Wafer scale tilt-compensated silicon nanowire probes are an excellent mass producible platform for non-destructive topographic imaging of high aspect ratio features.

  13. Versatile atomic force microscopy setup combined with micro-focused X-ray beam

    SciTech Connect

    Slobodskyy, T. Tholapi, R.; Liefeith, L.; Hansen, W.; Zozulya, A. V. Fester, M.; Sprung, M.

    2015-06-15

    Micro-focused X-ray beams produced by third generation synchrotron sources offer new perspective of studying strains and processes at nanoscale. Atomic force microscope setup combined with a micro-focused synchrotron beam allows precise positioning and nanomanipulation of nanostructures under illumination. In this paper, we report on integration of a portable commercial atomic force microscope setup into a hard X-ray synchrotron beamline. Details of design, sample alignment procedure, and performance of the setup are presented.

  14. Versatile atomic force microscopy setup combined with micro-focused X-ray beam

    NASA Astrophysics Data System (ADS)

    Slobodskyy, T.; Zozulya, A. V.; Tholapi, R.; Liefeith, L.; Fester, M.; Sprung, M.; Hansen, W.

    2015-06-01

    Micro-focused X-ray beams produced by third generation synchrotron sources offer new perspective of studying strains and processes at nanoscale. Atomic force microscope setup combined with a micro-focused synchrotron beam allows precise positioning and nanomanipulation of nanostructures under illumination. In this paper, we report on integration of a portable commercial atomic force microscope setup into a hard X-ray synchrotron beamline. Details of design, sample alignment procedure, and performance of the setup are presented.

  15. Joining patch-clamp and atomic force microscopy techniques for studying black lipid bilayers

    NASA Astrophysics Data System (ADS)

    Ovalle-García, Erasmo; Ortega-Blake, Iván

    2007-08-01

    An experimental protocol that enables the direct characterization of freestanding lipid bilayers through a combination of atomic force microscopy and single channel recording is presented. The method consists of producing a 15μm diameter pore in a 3μm thick Mylar film that delimits two vessels. The micropore was done by a glass microneedle. >L-α-phosphatidylcholine bilayers were routinely painted on the pore, observed by atomic force microscopy, and tested with gramicidin D ion channels.

  16. Atom wall dispersive forces from the master equation formalism

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

    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 analyse 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 cannot be considered as a direct result of the vacuum fluctuations only. Concerning the interaction between the atom and the wall at high temperatures, we show that a saturation of the potential for all distances occurs. This saturated potential coincides precisely with that obtained in the London-van der Waals limit.

  17. Atomic force microscopy imaging of viscoelastic properties in toughened polypropylene resins

    NASA Astrophysics Data System (ADS)

    Nysten, Bernard; Legras, Roger; Costa, Jean-Louis

    1995-11-01

    The bulk morphology of two toughened polypropylene/(ethylene propylene)copolymer resins (PP/EP) presenting different impact resistances has been studied by means of different atomic force microscopy techniques: contact atomic force microscopy, lateral force microscopy (LFM), and force modulation microscopy (FMM). The three techniques reveal two different morphologies as observed in transmission electronic microscopy. In LFM, a higher friction force is observed on the rubbery phase which has the lower Young's modulus confirming the relationship between friction force and elastic properties. In force modulation, the elastic moduli is found to be much lower on the EP nodules in both resins. FMM also reveals that the difference of viscous response between the PP matrix and the EP nodules is much lower in the resin which is less impact resistant.

  18. The Analog Atomic Force Microscope: Measuring, Modeling, and Graphing for Middle School

    ERIC Educational Resources Information Center

    Goss, Valerie; Brandt, Sharon; Lieberman, Marya

    2013-01-01

    using an analog atomic force microscope (A-AFM) made from a cardboard box and mailing tubes. Varying numbers of ping pong balls inside the tubes mimic atoms on a surface. Students use a dowel to make macroscale measurements similar to those of a nanoscale AFM tip as it…

  19. Nonequilibrium forces between atoms and dielectrics mediated by a quantum field

    SciTech Connect

    Behunin, Ryan O.; Hu, Bei-Lok

    2011-07-15

    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-graining to the physical variables--the medium, the quantum field, and the atom's internal degrees of freedom, in that order--to extract their averaged effects from the lowest tier progressively to the top tier. The first tier of coarse-graining provides the averaged effect of the medium upon the field, quantified by a complex permittivity (in the frequency domain) describing the response of the dielectric to the field in addition to its back action on the field through a stochastic forcing term. The last tier of coarse-graining over the atom's internal degrees of freedom results in an equation of motion for the atom's center of mass from which we can derive the force on the atom. Our nonequilibrium formulation provides a fully dynamical description of the atom's motion including back-action effects from all other relevant variables concerned. In the long-time limit we recover the known results for the atom-dielectric force when the combined system is in equilibrium or in a nonequilibrium stationary state.

  20. The Analog Atomic Force Microscope: Measuring, Modeling, and Graphing for Middle School

    ERIC Educational Resources Information Center

    Goss, Valerie; Brandt, Sharon; Lieberman, Marya

    2013-01-01

    using an analog atomic force microscope (A-AFM) made from a cardboard box and mailing tubes. Varying numbers of ping pong balls inside the tubes mimic atoms on a surface. Students use a dowel to make macroscale measurements similar to those of a nanoscale AFM tip as it…