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Sample records for afm nanoindentation experiments

  1. AFM nanoindentations of diatom biosilica surfaces.

    PubMed

    Losic, Dusan; Short, Ken; Mitchell, James G; Lal, Ratnesh; Voelcker, Nicolas H

    2007-04-24

    Diatoms have intricately and uniquely nanopatterned silica exoskeletons (frustules) and are a common target of biomimetic investigations. A better understanding of the diatom frustule structure and function at the nanoscale could provide new insights for the biomimetic fabrication of nanostructured ceramic materials and lightweight, yet strong, scaffold architectures. Here, we have mapped the nanoscale mechanical properties of Coscinodiscus sp. diatoms using atomic force microscopy (AFM)-based nanoindentation. Mechanical properties were correlated with the frustule structures obtained from high-resolution AFM and scanning electron microscopy (SEM). Significant differences in the micromechanical properties for the different frustule layers were observed. A comparative study of other related inorganic material including porous silicon films and free-standing membranes as well as porous alumina was also undertaken.

  2. Development of a novel nanoindentation technique by utilizing a dual-probe AFM system

    PubMed Central

    Sahin, Ferat; Yablon, Dalia

    2015-01-01

    Summary A novel instrumentation approach to nanoindentation is described that exhibits improved resolution and depth sensing. The approach is based on a multi-probe scanning probe microscopy (SPM) tool that utilizes tuning-fork based probes for both indentation and depth sensing. Unlike nanoindentation experiments performed with conventional AFM systems using beam-bounce technology, this technique incorporates a second probe system with an ultra-high resolution for depth sensing. The additional second probe measures only the vertical movement of the straight indenter attached to a tuning-fork probe with a high spring constant and it can also be used for AFM scanning to obtain an accurate profiling. Nanoindentation results are demonstrated on silicon, fused silica, and Corning Eagle Glass. The results show that this new approach is viable in terms of accurately characterizing mechanical properties of materials through nanoindentation with high accuracy, and it opens doors to many other exciting applications in the field of nanomechanical characterization. PMID:26665072

  3. Mechanical Characterization of Photo-crosslinked, Thermoresponsive Hydrogel Thin Films via AFM Nanoindentation

    NASA Astrophysics Data System (ADS)

    Le, Thao; Aidala, Katherine; Hayward, Ryan

    2014-03-01

    Thin hydrogel films with patterned swelling are known to buckle into programmed three-dimensional shapes, offering approaches to fabricate reversibly self-folding micro-devices for actuators and drug delivery devices. To precisely control the shapes adopted, it is important to quantitatively understand the relationship between swelling and mechanical properties. Furthermore, to understand the buckling pathways and the mechanical responses of the swelled materials, it is also important to identify how the gels undergo stress relaxation. However, the low moduli, high water contents, and micrometer-scale thicknesses of these materials have so far made mechanical characterization difficult. In this study, we use an AFM nanoindentation technique to characterize the mechanical properties of photo-crosslinked, thermoresponsive poly(N-isopropylacrylamide) hydrogel thin films. Simultaneously, we conduct stress relaxation experiments at microscopic indentation lengths to differentiate between the effects of viscoelastic and poroelastic response mechanisms. This research was funded by the Army Research Office through W911NF-11-1-0080 and the NSF Materials Research Science and Engineering Center at the University of Massachusetts through DMR-0820506.

  4. Mechanical properties of in situ demineralised human enamel measured by AFM nanoindentation

    NASA Astrophysics Data System (ADS)

    Finke, Manuela; Hughes, Julie A.; Parker, David M.; Jandt, Klaus D.

    2001-10-01

    Diet-induced demineralisation is one of the key factors in surface changes of tooth enamel, with soft drinks being a significant etiological agent. The first step in this dissolution process is characterised by a change in the mechanical properties of the enamel and a roughening of the surface. The objective of this pilot study was to measure early stages of in situ induced hardness changes of polished human enamel surfaces with high accuracy using a nanoindenter attached to an atomic force microscope (AFM). Human unerupted third molars were cleaned, sterilised with sodium hypochlorite, sectioned and embedded in epoxy resin. The outer enamel surface was polished and the samples partly covered with a tape, allowing a 2-mm-wide zone to be exposed to the oral environment. Samples were fitted in an intra-oral appliance, which was worn from 9 a.m. to 5 p.m. for one day. During this time the volunteer sipped 250 ml of a drink over 10 min periods at 9.00, 11.00, 13.00 and 15.00 h. Three different drinks, mineral water, orange juice and the prototype of a blackcurrant drink with low demineralisation potential were used in this study. At the end of the experiment the samples were detached from the appliance, the tape removed and the surfaces chemically cleaned. The surface hardness and reduced Young's modulus of the exposed and unexposed areas of each sample were determined. In addition, high resolution topographical AFM images were obtained. This study shows that by determining the hardness and reduced Young's modulus, the difference in demineralisation caused by the drinks can be detected and quantified before statistically significant changes in surface topography could be observed with the AFM. The maximum decrease in surface hardness and Young's modulus occurred in the samples exposed to orange juice, followed by those exposed to the blackcurrant drink, while exposure to water led to the same values as unexposed areas. A one-way ANOVA showed a statistically significant

  5. Nanomechanical characterization of nanostructured bainitic steel: Peak Force Microscopy and Nanoindentation with AFM.

    PubMed

    Morales-Rivas, Lucia; González-Orive, Alejandro; Garcia-Mateo, Carlos; Hernández-Creus, Alberto; Caballero, Francisca G; Vázquez, Luis

    2015-01-01

    The full understanding of the deformation mechanisms in nanostructured bainite requires the local characterization of its mechanical properties, which are expected to change from one phase, bainitic ferrite, to another, austenite. This study becomes a challenging process due to the bainitic nanostructured nature and high Young's modulus. In this work, we have carried out such study by means of the combination of AFM-based techniques, such as nanoindentation and Peak Force Quantitative Nanomechanical Mapping (PF-QNM) measurements. We have addressed critically the limits and advantages of these techniques and been able to measure some elastoplastic parameters of both phases. Specifically, we have analyzed by PF-QNM two nanostructured bainitic steels, with a finer and a coarser structure, and found that both phases have a similar Young's modulus. PMID:26602631

  6. Nanomechanical characterization of nanostructured bainitic steel: Peak Force Microscopy and Nanoindentation with AFM

    PubMed Central

    Morales-Rivas, Lucia; González-Orive, Alejandro; Garcia-Mateo, Carlos; Hernández-Creus, Alberto; Caballero, Francisca G.; Vázquez, Luis

    2015-01-01

    The full understanding of the deformation mechanisms in nanostructured bainite requires the local characterization of its mechanical properties, which are expected to change from one phase, bainitic ferrite, to another, austenite. This study becomes a challenging process due to the bainitic nanostructured nature and high Young’s modulus. In this work, we have carried out such study by means of the combination of AFM-based techniques, such as nanoindentation and Peak Force Quantitative Nanomechanical Mapping (PF-QNM) measurements. We have addressed critically the limits and advantages of these techniques and been able to measure some elastoplastic parameters of both phases. Specifically, we have analyzed by PF-QNM two nanostructured bainitic steels, with a finer and a coarser structure, and found that both phases have a similar Young’s modulus. PMID:26602631

  7. Matrix of rectangular pores obtained by AFM nanoindentation and electrolytic oxidation of Al

    NASA Astrophysics Data System (ADS)

    Belca, I. D.; Petkovic, M.; Stojadinovic, S.; Kasalica, B.; Belca, J. S.; Zekovic, Lj. D.

    2011-07-01

    AFM nanoindentation is used for pretexturing of Al sample intended for anodic oxidation in porous film-forming electrolytes. The rectangular quadratic and non-quadratic matrices of nanoindents were made by means of an AFM with diamond tip. The period of the 2D array of nanoindented concaves ranged from ˜50 to ˜370 nm. The pitch of the holes ranged from 13 to 170 nm. After anodization in water solutions of three different acids (0.3 M sulfuric, 0.3 M oxalic and 0.3 M phosphoric) at voltages chosen according to matrix period (20, 30 and 160 V), the well-arranged matrices of rectangular pores were obtained. The rectangular symmetry of the pretextured Al surface almost ideally transferred on porous alumina matrix, maintaining the highly ordered arrangement of the pores and rectangular cross section trough the whole film thickness with high pore depth to aperture size aspect ratio. During prolonged anodization in phosphoric acid, standard cells on the boundary of nanoindented area disturbed the arrangement and shape of quadratic cells.

  8. Dislocation dynamical approach to force fluctuations in nanoindentation experiments

    NASA Astrophysics Data System (ADS)

    Ananthakrishna, G.; Katti, Rohit; K, Srikanth

    2014-09-01

    We develop an approach that combines the power of nonlinear dynamics with the evolution equations for the mobile and immobile dislocation densities and force to explain force fluctuations in nanoindentation experiments. The model includes nucleation, multiplication, and propagation thresholds for mobile dislocations, and other well known dislocation transformation mechanisms. The model predicts all the generic features of nanoindentation such as the Hertzian elastic branch followed by several force drops of decreasing magnitudes, and residual plasticity after unloading. The stress corresponding to the elastic force maximum is close to the yield stress of an ideal solid. The predicted values for all the quantities are close to those reported by experiments. Our model allows us to address the indentation-size effect including the ambiguity in defining the hardness in the force drop dominated regime. At large indentation depths, the hardness remains nearly constant with a marginal decreasing trend.

  9. Piezoelectric Nanoindentation

    SciTech Connect

    Rar, Andrei; Pharr, George Mathews; Oliver, Warren C.; Karapetian, Edgar; Kalinin, Sergei V

    2006-01-01

    Piezoelectric nanoindentation (PNI) has been developed to quantitatively address electromechanical coupling and pressure-induced dynamic phenomena in ferroelectric materials on the nanoscale. In PNI, an oscillating voltage is applied between the back side of the sample and the indenter tip, and the first harmonic of bias-induced surface displacement at the area of indenter contact is detected. PNI is implemented using a standard nanoindentation system equipped with a continuous stiffness measurement system. The piezoresponse of polycrystalline lead zirconate titanate (PZT) and BaTiO{sub 3} piezoceramics was studied during a standard nanoindentation experiment. For PZT, the response was found to be load independent, in agreement with theoretical predictions. In polycrystalline barium titanate, a load dependence of the piezoresponse was observed. The potential of piezoelectric nanoindentation for studies of phase transitions and local structure-property relations in piezoelectric materials is discussed.

  10. Examination of dentin surface using AFM (our experience).

    PubMed

    Zapletalová, Zdenka; Kubínek, Roman; Vůjtek, Milan; Novotný, Radko

    2004-01-01

    Atomic force microscopy (AFM) as one the technique of Scanning Probe Microscopy is useful for imaging of surface structure. This method can yield three-dimensional high-resolution topographic images of sample surfaces by using a scanning technique for conductors and insulators on atomic scale. It is based upon mapping of atomic-forces on a surface of an investigated sample. The method is useful not only in physics and chemistry; it can be also applied in biological fields. Special construction of AFM scanner enables to follow biological samples in liquid environments. Artifacts caused by dehydration of samples are removed this way. Dentin of human teeth is a vital hydrated tissue. It is strongly sensitive to dehydration and drying that are commonly used in preparation of samples in examinations by Scanning Electron Microscopy (SEM). We describe our experience in examination of dentin surfaces of extracted human third molars using contact method of AFM under moist conditions.

  11. Nanoindentation of soft films on hard substrates: Experiments and finite element simulations

    SciTech Connect

    Pharr, G.M.; Tsui, T.Y.; Bolshakov, A.; Hay, J.C.

    1997-12-31

    Experiments and finite element simulations have been performed to examine error measurement of hardness and elastic modulus caused by pile-up when soft films deposited on hard substrates are tested by nanoindentation methods. Pile-up is exacerbated in soft-film/hard-substrate systems by the constraint imposed on plastic deformation in the film by the relatively non-deformable substrate. To experimentally examine pile-up effects, soft aluminum films with thicknesses of 240, 650, and 1700 nm were deposited on hard soda-lime glass substrates and tested by nanoindentation techniques. This system is attractive because the elastic modulus of the film and the substrate are approximately the same, but the substrate is harder than the film by a factor of about ten. Consequently, substrate influences on the indentation load-displacement behavior are manifested primarily by differences in the plastic flow characteristics alone. The elastic modulus of the film/substrate system, as measured by nanoindentation techniques, exhibits an increase with indenter penetration depth which peaks at a value approximately 30% greater than the true film modulus at a penetration depth close to the film thickness. Finite element simulation shows that this unusual behavior is caused by substrate-induced enhancement of pile-up. Finite element simulation also shows that the amount of pile-up increases with increasing penetration depth, and that the pile-up geometry depends on the work-hardening characteristics of the film. Because of these effects, nanoindentation techniques overestimate the true film hardness and elastic modulus by as much as 68% and 35%, respectively, depending on the work-hardening behavior of the film and the indenter penetration depth. The largest errors occur in non-work-hardening materials at penetration depths close to the film thickness, for which substrate-induced enhancement of pile-up is greatest.

  12. Viscoelastic properties of polycarbonate, poly(methyl methacrylate) and their nanocomposites via nanoindentation experiments

    NASA Astrophysics Data System (ADS)

    Noll, Kenneth; Wong, Maranda; Evke, Erin; Rende, Deniz; Ozisik, Rahmi

    2014-03-01

    Polycarbonate, PC, and poly(methyl methacrylate), PMMA, are economic alternatives to glass mainly die to their mecahnical and optical properties. The uses of PC and PMMA can be expanded if their impact response and scratch resistance are improved. Carbon nanotubes are known to increase the toughness of PMMA and improve its resistance impact forces. In the current study, the viscoelastic properties of PC, PMMA and their nanocomposites were investigated via nanoindentation experiments. Stress relaxation experiments were performed under various loading rates._ The material is partially based upon work supported by NSF under Grant Nos. 1200270 and 1003574.

  13. Liquid contact resonance AFM: analytical models, experiments, and limitations

    NASA Astrophysics Data System (ADS)

    Parlak, Zehra; Tu, Qing; Zauscher, Stefan

    2014-11-01

    Contact resonance AFM (CR-AFM) is a scanning probe microscopy technique that utilizes the contact resonances of the AFM cantilever for concurrent imaging of topography and surface stiffness. The technique has not been used in liquid until recently due to analytical and experimental difficulties, associated with viscous damping of cantilever vibrations and fluid loading effects. To address these difficulties, (i) an analytical approach for contact resonances in liquid is developed, and (ii) direct excitation of the contact resonances is demonstrated by actuating the cantilever directly in a magnetic field. By implementing the analytical approach and the direct actuation through magnetic particles, quantitative stiffness imaging on surfaces with a wide range of stiffness can be achieved in liquid with soft cantilevers and low contact forces.

  14. Age-related deterioration in trabecular bone mechanical properties at material level: nanoindentation study of the femoral neck in women by using AFM.

    PubMed

    Milovanovic, Petar; Potocnik, Jelena; Djonic, Danijela; Nikolic, Slobodan; Zivkovic, Vladimir; Djuric, Marija; Rakocevic, Zlatko

    2012-02-01

    Despite general belief that the mechanical properties of bone material contribute to whole bone strength, it is still obscure what the age effects are on mechanical behavior of the bone material, particularly in the case of the femoral neck trabeculae. In this study, atomic force microscopy was used for imaging and measuring the size of mineral grains, as well as nano-scale mechanical characterization (nanoindentation) of the bone mineralized matrix of trabeculae, with the aim to explore the age effects on bone elasticity and give new insight into age-related bone fragility. The bone samples in this study comprised trabecular bone specimens of the femoral neck region, collected from eight skeletal healthy women (five young adults: 27-38yrs., three elderly: 83-94yrs.) at autopsy. Bone trabeculae in the elderly displayed a higher modulus and nanohardness, signifying a decreased amount of energy that can be accommodated by the bone tissue during loading. Regression analysis revealed that nearly 65% of variability in the bone matrix elastic modulus can be statistically explained by the changes in size of the matrix mineral grains. This study revealed that the bone trabeculae of elderly women express less elastic behavior at the material level, which makes them more vulnerable to unusual impact loads originating from a fall. The observed age-related structural and mechanical alteration at the bone material level adds new evidence for understanding why hip fractures are more frequent in elderly women.

  15. Nanoindentation experiments for single-layer rectangular graphene films: a molecular dynamics study

    PubMed Central

    2014-01-01

    A molecular dynamics study on nanoindentation experiments is carried out for some single-layer rectangular graphene films with four edges clamped. Typical load–displacement curves are obtained, and the effects of various factors including indenter radii, loading speeds, and aspect ratios of the graphene film on the simulation results are discussed. A formula describing the relationship between the load and indentation depth is obtained according to the molecular dynamics simulation results. Young’s modulus and the strength of the single-layer graphene film are measured as about 1.0 TPa and 200 GPa, respectively. It is found that the graphene film ruptured in the central point at a critical indentation depth. The deformation mechanisms and dislocation activities are discussed in detail during the loading-unloading-reloading process. It is observed from the simulation results that once the loading speed is larger than the critical loading speed, the maximum force exerted on the graphene film increases and the critical indentation depth decreases with the increase of the loading speed. PMID:24447765

  16. Simulation of nanoindentation experiment on RF magnetron sputtered nanocolumnar V2O5 film using finite element method

    NASA Astrophysics Data System (ADS)

    Porwal, Deeksha; Gupta, A. K.; Pillai, Anju M.; Sharma, Anand Kumar; Mukhopadhyay, Anoop Kumar; Khan, Kallol; Dey, Arjun

    2016-07-01

    The present work reports the nanomechanical behavior of a pulsed radio frequency (RF) magnetron sputtered vanadium pentoxide (V2O5) film deposited on silicon (Si) substrate using a combination of nanoindentation experiments and a finite element model (FEM). Deposited V2O5 film is characterized by x-ray diffraction (XRD), nanoprofilometry, field emission scanning electron microscopy (FESEM), nanoindentation and FEM. The phase pure 6.16 μm V2O5 film shows a nanocolumnar structure. The film exhibits nanohardness (H) of 0.16 ± 0.013 GPa and Young’s modulus (E) of about 12.05 ± 1.41 GPa. The FEM reproduces experimentally obtained load versus depth (P-h) plot and subsequently give yield stress and strain hardening component data of V2O5 film on Si substrate. Stress-strain behavior and von-Mises stress distribution of the V2O5 film with Si substrate system are also simulated. The FE model confirms the local maximum equivalent stress active underneath the nanoindenters to be nearly twice as high as the yield stress and thereby explains the plastic deformation observed in the V2O5 film.

  17. A study of the micro- and nanoscale deformation behavior of individual austenitic dendrites in a FeCrMoVC cast alloy using micro- and nanoindentation experiments

    NASA Astrophysics Data System (ADS)

    Zeisig, J.; Hufenbach, J.; Wendrock, H.; Gemming, T.; Eckert, J.; Kühn, U.

    2016-04-01

    Micro- and nanoindentation experiments were conducted to investigate the deformation mechanisms in a Fe79.4Cr13Mo5V1C1.6 (wt. %) cast alloy. This alloy consists of an as cast microstructure mainly composed of austenite, martensite, and a complex carbide network. During microhardness testing, metastable austenite transforms partially into martensite confirmed by electron backscatter diffraction. For nanoindentation tests, two different indenter geometries were applied (Berkovich and cube corner type). Load-displacement curves of nanoindentation in austenitic dendrites depicted pop-ins after transition into plastic deformation for both nanoindenters. Characterizations of the region beneath a nanoindent by transmission electron microscopy revealed a martensitic transformation as an activated deformation mechanism and suggest a correlation with the pop-in phenomena of the load-displacement curves. Furthermore, due to an inhomogeneous chemical composition within the austenitic dendrites, more stabilized regions deform by mechanical twinning. This additional deformation mechanism was only observed for the cube corner indenter with the sharper geometry since higher shear stresses are induced beneath the contact area.

  18. Understanding pop-ins in spherical nanoindentation

    SciTech Connect

    Pathak, Siddhartha E-mail: siddharthapathak@gmail.com; Riesterer, Jessica L.; Michler, Johann; Kalidindi, Surya R.

    2014-10-20

    Pop-ins, or sudden displacement-bursts at constant load in a nanoindentation test, are typically attributed to the difficulty of setting up potent dislocation sources in the very small indentation zones in these experiments. Such displacement (and strain) bursts would intuitively indicate a sharp drop in stress during the pop-in event itself. However, spherical indentation stress-strain curves routinely exhibit a high and stable indentation stress value during the pop-in, and the indentation stresses decrease only after a further finite amount of additional indentation displacement has been applied. In order to understand this discrepancy, we utilize a combination of interrupted spherical indentation tests along with depth profiling of the residual indentation surfaces using in-situ atomic force microscopy (AFM) to study pop-ins. The AFM surface profile maps show that there is an asymmetric profile change over a limited region around the indentation contact area for a single pop-in; the asymmetry disappears upon further loading beyond the pop-in. A plausible sequence of physical processes (related to metal plasticity) occurring underneath the indenter during and immediately after the occurrence of the pop-in is proposed to explain these observations.

  19. Understanding pop-ins in spherical nanoindentation

    SciTech Connect

    Pathak, Siddhartha; Riesterer, Jessica L.; Kalidindi, Surya R.; Michler, Johann

    2014-10-24

    In this study, pop-ins, or sudden displacement-bursts at constant load in a nanoindentation test, are typically attributed to the difficulty of setting up potent dislocation sources in the very small indentation zones in these experiments. Such displacement (and strain) bursts would intuitively indicate a sharp drop in stress during the pop-in event itself. However, spherical indentation stress-strain curves routinely exhibit a high and stable indentation stress value during the pop-in, and the indentation stresses decrease only after a further finite amount of additional indentation displacement has been applied. In order to understand this discrepancy, we utilize a combination of interrupted spherical indentation tests along with depth profiling of the residual indentation surfaces using in-situ atomic force microscopy (AFM) to study pop-ins. The AFM surface profile maps show that there is an asymmetric profile change over a limited region around the indentation contact area for a single pop-in; the asymmetry disappears upon further loading beyond the pop-in. A plausible sequence of physical processes (related to metal plasticity) occurring underneath the indenter during and immediately after the occurrence of the pop-in is proposed to explain these observations.

  20. Understanding pop-ins in spherical nanoindentation

    DOE PAGES

    Pathak, Siddhartha; Riesterer, Jessica L.; Kalidindi, Surya R.; Michler, Johann

    2014-10-24

    In this study, pop-ins, or sudden displacement-bursts at constant load in a nanoindentation test, are typically attributed to the difficulty of setting up potent dislocation sources in the very small indentation zones in these experiments. Such displacement (and strain) bursts would intuitively indicate a sharp drop in stress during the pop-in event itself. However, spherical indentation stress-strain curves routinely exhibit a high and stable indentation stress value during the pop-in, and the indentation stresses decrease only after a further finite amount of additional indentation displacement has been applied. In order to understand this discrepancy, we utilize a combination of interruptedmore » spherical indentation tests along with depth profiling of the residual indentation surfaces using in-situ atomic force microscopy (AFM) to study pop-ins. The AFM surface profile maps show that there is an asymmetric profile change over a limited region around the indentation contact area for a single pop-in; the asymmetry disappears upon further loading beyond the pop-in. A plausible sequence of physical processes (related to metal plasticity) occurring underneath the indenter during and immediately after the occurrence of the pop-in is proposed to explain these observations.« less

  1. An innovative method and experiment for fabricating bulgy shape nanochannel using AFM

    NASA Astrophysics Data System (ADS)

    Lin, Zone-Ching; Jheng, Hao-Yuan; Ding, Hao-Yang

    2015-08-01

    The paper proposes using atomic force microscopy (AFM) and the concept of specific down force energy (SDFE) to establish an innovative offset cycle cutting method for fabricating a bulgy shape nanochannel on a single-crystal silicon substrate. In the offset cycle cutting method, cutting is performed at a constant down force in all cutting passes. After the first cutting pass, the AFM probe is offset rightward for the second pass and subsequently offset leftward to the middle (i.e., between the positions of the first two cutting passes) for the third cutting pass. Applying a step-by-step method to modify the offset distance and approach the defined SDFE value, this study determined the depth of the middle cutting pass and smaller values of upward bulginess and downward indentation at the bottom of the nanochannel. The nanochannel width can be increased by increasing the number of offset cycle cutting passes. In addition, by applying the proposed method, this study involved a simulation and experiment concerning the cutting path plan of bulgy shape nanochannels. Furthermore, using a small down force along the burr path is proposed for reducing burr height. The results of the simulation and experiment were compared to verify the feasibility of the method.

  2. Nanopuller-open data acquisition platform for AFM force spectroscopy experiments.

    PubMed

    Pawlak, Konrad; Strzelecki, Janusz

    2016-05-01

    Atomic Force Microscope (AFM) is a widely used tool in force spectroscopy studies. Presently, this instrument is accessible from numerous vendors, albeit commercial solutions are expensive and almost always hardware and software closed. Approaches for open setups were published, as with modern low cost and readily available piezoelectric actuators, data acquisition interfaces and optoelectronic components building such force spectroscopy AFM is relatively easy. However, suitable software to control such laboratory made instrument was not released. Developing it in the lab requires significant time and effort. Our Nanopuller software described in this paper is intended to eliminate this obstacle. With only minimum adjustments this program can be used to control and acquire data with any suitable National Instruments universal digital/analog interface and piezoelectric actuator analog controller, giving significant freedom and flexibility in designing force spectroscopy experiment. Since the full code, written in a graphical LabVIEW environment is available, our Nanopuller can be easily customized. In this paper we describe the program and test its performance in controlling different setups. Successful and accurate force curve acquisition for standard samples (single molecules of I27O reference titin polyprotein and DNA as well as red blood cells) is shown.

  3. The use of nanoindentation for determining internal lengths and the constitutive response of monument materials: models and experiments

    NASA Astrophysics Data System (ADS)

    Konstantinidis, Avraam A.; Frantziskonis, George; Askes, Harm; Aifantis, Elias C.

    2016-04-01

    An alternative interpretation of nanoindentation experimental data and the associated phenomenon of indentation size effect (ISE) is proposed on the basis of a simple gradient elasticity equation, used to account for the development of elastic gradients generated by the geometry characterizing the indenter-specimen system. An application is considered for marble, i.e. a construction/restoration material.

  4. Nonlinear finite-element analysis of nanoindentation of viral capsids

    NASA Astrophysics Data System (ADS)

    Gibbons, Melissa M.; Klug, William S.

    2007-03-01

    Recent atomic force microscope (AFM) nanoindentation experiments measuring mechanical response of the protein shells of viruses have provided a quantitative description of their strength and elasticity. To better understand and interpret these measurements, and to elucidate the underlying mechanisms, this paper adopts a course-grained modeling approach within the framework of three-dimensional nonlinear continuum elasticity. Homogeneous, isotropic, elastic, thick-shell models are proposed for two capsids: the spherical cowpea chlorotic mottle virus (CCMV), and the ellipsocylindrical bacteriophage ϕ29 . As analyzed by the finite-element method, these models enable parametric characterization of the effects of AFM tip geometry, capsid dimensions, and capsid constitutive descriptions. The generally nonlinear force response of capsids to indentation is shown to be insensitive to constitutive particulars, and greatly influenced by geometric and kinematic details. Nonlinear stiffening and softening of the force response is dependent on the AFM tip dimensions and shell thickness. Fits of the models capture the roughly linear behavior observed in experimental measurements and result in estimates of Young’s moduli of ≈280-360MPa for CCMV and ≈4.5GPa for ϕ29 .

  5. Assembly of live micro-organisms on microstructured PDMS stamps by convective/capillary deposition for AFM bio-experiments.

    PubMed

    Dague, E; Jauvert, E; Laplatine, L; Viallet, B; Thibault, C; Ressier, L

    2011-09-30

    Immobilization of live micro-organisms on solid substrates is an important prerequisite for atomic force microscopy (AFM) bio-experiments. The method employed must immobilize the cells firmly enough to enable them to withstand the lateral friction forces exerted by the tip during scanning but without denaturing the cell interface. In this work, a generic method for the assembly of living cells on specific areas of substrates is proposed. It consists in assembling the living cells within the patterns of microstructured, functionalized poly-dimethylsiloxane (PDMS) stamps using convective/capillary deposition. This versatile approach is validated by applying it to two systems of foremost importance in biotechnology and medicine: Saccharomyces cerevisiae yeasts and Aspergillus fumigatus fungal spores. We show that this method allows multiplexing AFM nanomechanical measurements by force spectroscopy on S. cerevisiae yeasts and high-resolution AFM imaging of germinated Aspergillus conidia in buffer medium. These two examples clearly demonstrate the immense potential of micro-organism assembly on functionalized, microstructured PDMS stamps by convective/capillary deposition for performing rigorous AFM bio-experiments on living cells.

  6. Assembly of live micro-organisms on microstructured PDMS stamps by convective/capillary deposition for AFM bio-experiments

    NASA Astrophysics Data System (ADS)

    Dague, E.; Jauvert, E.; Laplatine, L.; Viallet, B.; Thibault, C.; Ressier, L.

    2011-09-01

    Immobilization of live micro-organisms on solid substrates is an important prerequisite for atomic force microscopy (AFM) bio-experiments. The method employed must immobilize the cells firmly enough to enable them to withstand the lateral friction forces exerted by the tip during scanning but without denaturing the cell interface. In this work, a generic method for the assembly of living cells on specific areas of substrates is proposed. It consists in assembling the living cells within the patterns of microstructured, functionalized poly-dimethylsiloxane (PDMS) stamps using convective/capillary deposition. This versatile approach is validated by applying it to two systems of foremost importance in biotechnology and medicine: Saccharomyces cerevisiae yeasts and Aspergillus fumigatus fungal spores. We show that this method allows multiplexing AFM nanomechanical measurements by force spectroscopy on S. cerevisiae yeasts and high-resolution AFM imaging of germinated Aspergillus conidia in buffer medium. These two examples clearly demonstrate the immense potential of micro-organism assembly on functionalized, microstructured PDMS stamps by convective/capillary deposition for performing rigorous AFM bio-experiments on living cells.

  7. Dynamic force microscopy simulator (dForce): A tool for planning and understanding tapping and bimodal AFM experiments

    PubMed Central

    Guzman, Horacio V; Garcia, Pablo D

    2015-01-01

    Summary We present a simulation environment, dForce, which can be used for a better understanding of dynamic force microscopy experiments. The simulator presents the cantilever–tip dynamics for two dynamic AFM methods, tapping mode AFM and bimodal AFM. It can be applied for a wide variety of experimental situations in air or liquid. The code provides all the variables and parameters relevant in those modes, for example, the instantaneous deflection and tip–surface force, velocity, virial, dissipated energy, sample deformation and peak force as a function of time or distance. The simulator includes a variety of interactions and contact mechanics models to describe AFM experiments including: van der Waals, Hertz, DMT, JKR, bottom effect cone correction, linear viscoelastic forces or the standard linear solid viscoelastic model. We have compared two numerical integration methods to select the one that offers optimal accuracy and speed. The graphical user interface has been designed to facilitate the navigation of non-experts in simulations. Finally, the accuracy of dForce has been tested against numerical simulations performed during the last 18 years. PMID:25821676

  8. Effect of AFM probe geometry on visco-hyperelastic characterization of soft materials

    NASA Astrophysics Data System (ADS)

    Boccaccio, Antonio; Lamberti, Luciano; Papi, Massimiliano; De Spirito, Marco; Pappalettere, Carmine

    2015-08-01

    Atomic force microscopy (AFM) nanoindentation is very suited for nano- and microscale mechanical characterization of soft materials. Although the structural response of polymeric networks that form soft matter depends on viscous effects caused by the relative slippage of polymeric chains, the usual assumption made in the AFM-based characterization is that the specimen behaves as a purely elastic material and viscous forces are negligible. However, for each geometric configuration of the AFM tip, there will be a limit indentation rate above which viscous effects must be taken into account to correctly determine mechanical properties. A parametric finite element study conducted on 12 geometric configurations of a blunt cone AFM tip (overall, the study included about 200 finite element analyses) allowed us to determine the limit indentation rate for each configuration. The selected tip dimensions cover commercially available products and account for changes in tip geometry caused by serial measurements. Nanoindentation rates cover typical experimental conditions set in AFM bio-measurements on soft matter. Viscous effects appear to be more significant in the case of sharper tips. This implies that, if quantitative data on sample viscosity are not available, using a rounded indenter and carrying out experiments below the limit indentation rate will allow errors in the determination of mechanical properties to be minimized.

  9. If mechanics of cells can be described by elastic modulus in AFM indentation experiments?

    NASA Astrophysics Data System (ADS)

    Sokolov, Igor; Dokukin, Maxim; Guz, Nataliia; Kalaparthi, Vivekanand

    2014-03-01

    We study the question if cells, being highly heterogeneous objects, can be described with an elastic modulus (the Young's modulus) in a self-consistent way. We analyze the elastic modulus using indentation done with AFM of human cervical epithelial cells. Both sharp (cone) and dull AFM probes were used. The indentation data collected were processed through different elastic models. The cell was considered as a homogeneous elastic medium which had either smooth spherical boundary (Hertz/Sneddon models) or the boundary covered with a layer of glycocalyx and membrane protrusions (``brush'' models). Validity of these approximations was investigated. Specifically, we tested the independence of the elastic modulus of the indentation depth, which is assumed in these models. We demonstrate that only one model shows consistency with treating cells as homogeneous elastic medium, the bush model when processing the indentation data collected with the dull probe. The elastic modulus demonstrates strong depth dependence in all other three models. We conclude that it is possible to describe the elastic properties of the cell body by means of an effective elastic modulus in a self-consistent way when using the brush model to analyze data collected with a dull AFM probe.

  10. Nanoindentation of Carbon Nanostructures.

    PubMed

    Kumar, Dinesh; Singh, Karamjit; Verma, Veena; Bhatti, H S

    2016-06-01

    In the present research paper carbon nanostructures viz. single walled carbon nanotubes, multi-walled carbon nanotubes, single walled carbon nanohorns and graphene nanoplatelets have been synthesized by CVD technique, hydrothermal method, DC arc discharge method in liquid nitrogen and microwave technique respectively. After synthesis 5 mm thick pallets of given nanomaterial are prepared by making a paste in isopropyl alcohol and using polyvinylidene difluoride as a binder and then these pallets were used for nanoindentation measurements. Hardness, reduced modulus, stiffness, contact height and contact area have been measured using nanoindenter. PMID:27427726

  11. Structural investigations on native collagen type I fibrils using AFM

    SciTech Connect

    Strasser, Stefan; Zink, Albert; Janko, Marek; Heckl, Wolfgang M.; Thalhammer, Stefan . E-mail: stefan.thalhammer@gsf.de

    2007-03-02

    This study was carried out to determine the elastic properties of single collagen type I fibrils with the use of atomic force microscopy (AFM). Native collagen fibrils were formed by self-assembly in vitro characterized with the AFM. To confirm the inner assembly of the collagen fibrils, the AFM was used as a microdissection tool. Native collagen type I fibrils were dissected and the inner core uncovered. To determine the elastic properties of collagen fibrils the tip of the AFM was used as a nanoindentor by recording force-displacement curves. Measurements were done on the outer shell and in the core of the fibril. The structural investigations revealed the banding of the shell also in the core of native collagen fibrils. Nanoindentation experiments showed the same Young's modulus on the shell as well as in the core of the investigated native collagen fibrils. In addition, the measurements indicate a higher adhesion in the core of the collagen fibrils compared to the shell.

  12. Note: A method for minimizing oxide formation during elevated temperature nanoindentation

    SciTech Connect

    Cheng, I. C.; Hodge, A. M.; Garcia-Sanchez, E.

    2014-09-15

    A standardized method to protect metallic samples and minimize oxide formation during elevated-temperature nanoindentation was adapted to a commercial instrument. Nanoindentation was performed on Al (100), Cu (100), and W (100) single crystals submerged in vacuum oil at 200 °C, while the surface morphology and oxidation was carefully monitored using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results were compared to room temperature and 200 °C nanoindentation tests performed without oil, in order to evaluate the feasibility of using the oil as a protective medium. Extensive surface characterization demonstrated that this methodology is effective for nanoscale testing.

  13. Nanoindentation of dental composites.

    PubMed

    Drummond, James L

    2006-07-01

    The intent of this project was to evaluate the elastic modulus and hardness of four composites with different fillers, a microfill, a hybrid, a dental resin cement, and a fiber filler, using nanoindentation. An indentation load of 0.001 N was used and 100 indents per specimen were taken. The elastic modulus measured for the Choice composite was 30.2-30.3 GPa, 15.9-16.0 GPa for Micronew, 24.6-27.1 GPa for Renew, and 36.4-47.1 GPa for Restolux. The statistical analysis indicated a significant difference in the elastic modulus for all four composites. Micronew had the lowest hardness (1.2-1.3 GPa) followed by Renew (1.6-1.8 GPa), Choice (2.6-2.8 GPa), and Restolux (2.7-4.0 GPa). The statistical analysis indicated a significant difference between Choice and Restolux from Micronew and Renew, with Renew and Micronew not being significantly different from each other. Nanoindentation of dental composites, using a 10 x 10 matrix of indentations, resulted in a wide range of measured values for the elastic modulus and hardness because of the size of the filler particle, the location of the indenter within the filler particle, the composition of the filler particles, and the location of the indenter within the filler/resin matrix.

  14. Nanoindentation of heterogeneous carbonaceous films containing Ni nano-crystals.

    PubMed

    Richter, A; Czerwosz, E; Dłuzewski, P; Kozłowski, M; Nowicki, M

    2009-01-01

    Composite films of nano-size nickel grains embedded in a carbonaceous matrix are synthesized by a PVD process of C(60) fullerenes and Ni acetate. The morphology of the nano-composite films is characterized by TEM, selected area electron diffraction, chemical analysis and AFM. Correlations with deposition parameters and typical structure changes are found. The mechanical properties are analyzed by nanoindentation. The load-displacement charts show typical pop-ins correlated with the heterogeneous nano-structure. The depth dependent hardness and indentation modulus vary according to the nano-composite structure and reflect the changes of the mechanical properties in the film.

  15. 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.

  16. Nanoindentation response of piezoelectric nano-islands

    NASA Astrophysics Data System (ADS)

    Cheng, Guang; Sriram, Sharath; Bhaskaran, Madhu; Venkatesh, T. A.

    2014-09-01

    Through three-dimensional finite element modeling, it is demonstrated that the nanoindentation response of piezoelectric nano-islands is strongly dependent on the shape of the nano-island and the depth of indentation. For indentations that are relatively deep (i.e., greater than 5% of the height of the islands), the substrate's elastic and plastic properties have a strong influence on the indentation response of piezoelectric nano-islands with substrate plasticity resulting in a significant reduction in the mechanical and electrical indentation stiffness. The predictions of the finite element models compare well with experiments on nano-islands of strontium-doped lead zirconate titanate.

  17. Nanoindentation and nanoscratching of hard coating materials for magnetic disks

    SciTech Connect

    Tsui, T.Y.; Pharr, G.M.; Oliver, W.C.; Chung, Y.W.; Cutiongco, E.C.; Bhatia, C.S.; White, R.L.; Rhodes, R.L.; Gorbatkin, S.M.

    1994-12-31

    Nanoindentation and nanoscratching experiments have been performed to assess the mechanical and tribological behavior of three thin film materials with potential application as wear resistant coatings for magnetic disk storage: (1) hydrogenated-carbon (CHx); (2) nitrogenated-carbon (CNx); and (3) boron suboxide (BOx). The hardness and elastic modulus were measured using nanoindentation. Ultra-low load nanoscratching tests were performed to assess the relative scratch resistance of the films and measure their friction coefficients. The mechanical and tribological performance of the three materials are discussed and compared.

  18. Influence of the degree of order of InGaP on its hardness determined using nanoindentation

    NASA Astrophysics Data System (ADS)

    Zakaria, A.; Fetzer, C. M.; Goorsky, M. S.

    2010-10-01

    Spontaneous atomic ordering takes place during metal-organic vapor phase epitaxy when certain semiconductors alloys start forming long-range arrangements different from their standard lattice unit cells. In the case of InGaP, a zincblende semiconductor, the ordered CuPt(B) structure consists of alternating Ga and In rich (1¯11) and (11¯1) planes. In this investigation, InGaP was deposited on (001) Ge wafers with a 6° miscut toward the [111] direction in two consecutive experiments. A surfactant was used in experiment A while depositing InGaP to induce a lower degree of order. high resolution x-ray diffraction was used to calculate composition and strain of the InGaP epilayers. The symmetric (004) as well as the asymmetric (224) glancing exit reflections were used. The results enabled the extraction of a theoretical band gap energy Eg corrected for strain effects. Photoluminescence was used to measure the actual Eg. By comparing the two, the degree of order η was determined to be 0.12-0.15 for wafers from experiment A and 0.43-0.44 for wafers from experiment B. Atomic force microscopy AFM demonstrated that all experimental wafers had a surface rms roughness of 6.1-7.4 Å. Extensive nanoindentation measurements were performed on samples from both experiments. It was determined that the degree of order has no effect on the nanoindentation hardness of InGaP. Using 1/2 (115) superlattice reflection scans, the InGaP ordered domains size was estimated to be 28.5 nm for sample B1. No superlattice peak was detected in sample A1. The large ordered domain size in B1 explains why no order-hardening behavior was observed in InGaP.

  19. Nanoindentation and thermal characterization of poly (vinylidenefluoride)/MWCNT nanocomposites

    SciTech Connect

    Eggedi, Obulapathi; Valiyaneerilakkal, Uvais; Varghese, Soney; Darla, M. R.

    2014-04-15

    We report the preparation, thermal and micro/nanomechanical behavior of poly (vinylidine diflouride) (PVDF)/multiwalled carbon nanotube (MWCNT) nanocomposites. It has been found that the addition of MWCNT considerably enhances the β-phase formation, thermal and mechanical properties of PVDF. Atomic force microscope (AFM) studies have been performed on the composites under stress conditions to measure the mechanical properties. The nanoscale mechanical properties of the composites like Young's modulus and hardness of the nanocomposites were investigated by nanoindentation technique. Morphological studies of the nanocomposites were also studied, observations show a uniform distribution of MWCNT in the matrix and interfacial adhesion between PVDF and MWCNT was achieved, which was responsible for enhancement in the hardness and Young's modulus. Differential scanning calorimetry (DSC) studies indicate that the melting temperature of the composites have been slightly increased while the heat of fusion markedly decreased with increasing MWCNT content.

  20. Force spectroscopy 101: how to design, perform, and analyze an AFM-based single molecule force spectroscopy experiment.

    PubMed

    Noy, Aleksandr

    2011-10-01

    Single molecule force spectroscopy presents a deceptively simple approach to probing interaction between molecules and molecular assemblies on the nanoscale by measuring forces that it takes to pull the molecules apart. Yet, a more detailed analysis reveals a wealth of different behaviors and interesting physics. This article aims to explore basic physical concepts behind these experiments from a strictly practical point of using these data to extract meaningful information about the interactions. It also focuses on different loading regimes in these experiments, different kinetics that they cause, and different data interpretation that is required for measurements in those regimes. PMID:21862386

  1. Qplus AFM driven nanostencil.

    PubMed

    Grévin, B; Fakir, M; Hayton, J; Brun, M; Demadrille, R; Faure-Vincent, J

    2011-06-01

    We describe the development of a novel setup, in which large stencils with suspended silicon nitride membranes are combined with atomic force microscopy (AFM) regulation by using tuning forks. This system offers the possibility to perform separate AFM and nanostencil operations, as well as combined modes when using stencil chips with integrated tips. The flexibility and performances are demonstrated through a series of examples, including wide AFM scans in closed loop mode, probe positioning repeatability of a few tens of nanometer, simultaneous evaporation of large (several hundred of micron square) and nanoscopic metals and fullerene patterns in static, multistep, and dynamic modes. This approach paves the way for further developments, as it fully combines the advantages of conventional stenciling with the ones of an AFM driven shadow mask. PMID:21721701

  2. Measurement of Young's relaxation modulus using nanoindentation

    NASA Astrophysics Data System (ADS)

    Huang, Gang; Lu, Hongbing

    2006-09-01

    In a previous paper (Lu et al., Mechanics of Time-Dependent Materials, 7, 2003, 189 207), we described methods to measure the creep compliance of polymers using Berkovich and spherical indenters by nanoindentation. However, the relaxation modulus is often needed in stress and deformation analysis. It has been well known that the interconversion between creep compliance and relaxation function presents an ill-posed problem, so that converting the creep compliance function to the relaxation function cannot always give accurate results, especially considering that the creep data at short times in nanoindentation are often not reliable, and the overall nanoindentation time is short, typically a few hundred seconds. In this paper, we present methods to measure Young’s relaxation functions directly using nanoindentation. A constant-rate displacement loading history is usually used in nanoindentations. Using viscoelastic contact mechanics, Young’s relaxation modulus is extracted using nanoindentation load-displacement data. Three bulk polymers, Polymethyl Methacrylate (PMMA), Polycarbonate (PC) and Polyurethane (PU), are used in this study. The Young’s relaxation functions measured from the nanoindentation are compared with data measured from conventional tensile and shear tests to evaluate the precision of the methods. A reasonably good agreement has been reached for all these materials for indentation depth higher than a certain value, providing reassurance for these methods for measuring relaxation functions.

  3. AFM cantilever vibration detection with a transmitted electron beam

    NASA Astrophysics Data System (ADS)

    Woehl, Taylor; Wagner, Ryan; Keller, Robert; Killgore, Jason

    Cantilever oscillations for dynamic atomic force microscopy (AFM) are conventionally measured with an optical lever system. The speed of AFM cantilevers can be increased by decreasing the size of the cantilever; however, the fastest AFM cantilevers are currently nearing the smallest size that can be detected with the current optical lever approach. Here we demonstrate an electron detection scheme in an SEM for detecting AFM cantilever oscillations. An oscillating AFM tip is positioned perpendicular to the propagation direction of a stationary ~ 1 nm diameter electron probe, and the oscillatory change in electron scattering resulting from the changing thickness of the electron irradiated area of the AFM tip is detected with a transmitted electron detector positioned below the AFM tip. We perform frequency sweep and ring-down experiments to determine the first resonant frequency and Q factor of an AFM cantilever.

  4. Spherical nanoindentation stress–strain curves

    DOE PAGES

    Pathak, Siddhartha; Kalidindi, Surya R.

    2015-03-24

    Although indentation experiments have long been used to measure the hardness and Young's modulus, the utility of this technique in analyzing the complete elastic–plastic response of materials under contact loading has only been realized in the past few years – mostly due to recent advances in testing equipment and analysis protocols. This paper provides a timely review of the recent progress made in this respect in extracting meaningful indentation stress–strain curves from the raw datasets measured in instrumented spherical nanoindentation experiments. These indentation stress–strain curves have produced highly reliable estimates of the indentation modulus and the indentation yield strength inmore » the sample, as well as certain aspects of their post-yield behavior, and have been critically validated through numerical simulations using finite element models as well as direct in situ scanning electron microscopy (SEM) measurements on micro-pillars. Much of this recent progress was made possible through the introduction of a new measure of indentation strain and the development of new protocols to locate the effective zero-point of initial contact between the indenter and the sample in the measured datasets. As a result, this has led to an important key advance in this field where it is now possible to reliably identify and analyze the initial loading segment in the indentation experiments.« less

  5. Spherical nanoindentation stress–strain curves

    SciTech Connect

    Pathak, Siddhartha; Kalidindi, Surya R.

    2015-03-24

    Although indentation experiments have long been used to measure the hardness and Young's modulus, the utility of this technique in analyzing the complete elastic–plastic response of materials under contact loading has only been realized in the past few years – mostly due to recent advances in testing equipment and analysis protocols. This paper provides a timely review of the recent progress made in this respect in extracting meaningful indentation stress–strain curves from the raw datasets measured in instrumented spherical nanoindentation experiments. These indentation stress–strain curves have produced highly reliable estimates of the indentation modulus and the indentation yield strength in the sample, as well as certain aspects of their post-yield behavior, and have been critically validated through numerical simulations using finite element models as well as direct in situ scanning electron microscopy (SEM) measurements on micro-pillars. Much of this recent progress was made possible through the introduction of a new measure of indentation strain and the development of new protocols to locate the effective zero-point of initial contact between the indenter and the sample in the measured datasets. As a result, this has led to an important key advance in this field where it is now possible to reliably identify and analyze the initial loading segment in the indentation experiments.

  6. TEM-nanoindentation studies of semiconducting structures.

    PubMed

    Le Bourhis, E; Patriarche, G

    2007-01-01

    This paper reviews the application of nanoindentation coupled with transmission electron microscopy (TEM) to investigations of the plastic behaviour of semiconducting structures and its implication for device design. Instrumented nanoindentation has been developed to extract the mechanical behaviour of small volumes scaled to those encountered in semiconductor heterostructures. We illustrate that TEM is a powerful complementary tool for the study of local plasticity induced by nanoindentation. TEM-nanoindentation allows for detailed understanding of the plastic deformation in semiconducting structures and opens practical routes for improvement of devices. Performances of heterostructures are deteriously affected by dislocations that relax the lattice mismatched layers. Different ways to obtain compliant substructures are being developed in order to concentrate the plastic relaxation underneath the heterostructure. Such approaches allow for mechanical design of micro- and opto-electronic devices to be considered throughout the fabrication process. PMID:16901706

  7. Local Mechanical Properties by Atomic Force Microscopy Nanoindentations

    NASA Astrophysics Data System (ADS)

    Tranchida, Davide; Piccarolo, Stefano

    The analysis of mechanical properties on a nanometer scale is a useful tool for combining information concerning texture organization obtained by microscopy with the properties of individual components. Moreover, this technique promotes the understanding of the hierarchical arrangement in complex natural materials as well in the case of simpler morphologies arising from industrial processes. Atomic Force Microscopy (AFM) can bridge morphological information, obtained with outstanding resolution, to local mechanical properties. When performing an AFM nanoindentation, the rough force curve, i.e., the plot of the voltage output from the photodiode vs. the voltage applied to the piezo-scanner, can be translated into a curve of the applied load vs. the penetration depth after a series of preliminary determinations and calibrations. However, the analysis of the unloading portion of the force curves collected for polymers does not lead to a correct evaluation of Young's modulus. The high slope of the unloading curves is not linked to an elastic behavior, as would be expected, but rather to a viscoelastic effect. This can be argued on the basis that the unloading curves are superimposed on the loading curves in the case of an ideal elastic behavior, as for rubbers, or generally in the case of materials with very short relaxation times. In contrast, when the relaxation time of the sample is close to or even much larger than the indentation time scale, very high slopes are recorded.

  8. Nanoindentation of Zr by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Lu (芦子哲), Zizhe; Chernatynskiy, Aleksandr; Noordhoek, Mark J.; Sinnott, Susan B.; Phillpot, Simon R.

    2015-12-01

    Molecular dynamics simulations of nanoindentation are used to study the deformation behaviors of single crystal Zr for four different surface orientations. The comparison of results for two different potentials, an embedded atom method potential and a charged optimized many body potential, reveals the influence of stable and unstable stacking fault energy on dislocation behaviors under nanoindentation. The load-displacement curve, hardness and deformation behaviors of the various surface orientations Zr are compared and the elastic and plastic deformation behaviors are analyzed.

  9. A fiber reinforced poroelastic model of nanoindentation of porcine costal cartilage: a combined experimental and finite element approach.

    PubMed

    Gupta, Shikha; Lin, Jeremy; Ashby, Paul; Pruitt, Lisa

    2009-08-01

    Nanoindentation has shown promise as a mechanical characterization tool for orthopaedic biomaterials since it can probe the properties of small, heterogeneous, irregularly shaped tissue volumes in physiological environments. However, the majority of nanoindentation analyses have been limited to the determination of linear elastic and viscoelastic properties. Since biomaterials possess complex nonlinear, hydrated, time-dependent constitutive behavior, the objective of the present study is to explore the ability of nanoindentation to determine physiologically relevant material properties using a fibril reinforced poroelastic (FRPE) model. A further goal is to ascertain the sensitivity of nanoindentation load-displacement curves to different FRPE parameters, including the elastic properties of the nonfibrillar matrix, the composition and distribution of fibers, and nonlinearity in the fluid permeability. Porcine costal cartilage specimens are experimentally tested with nanoindentation load relaxation experiments at two different loading depths and loading rates. The FRPE material properties are extracted from comparisons to finite element simulations. The study demonstrates the behavior of the model in nanoindentation is distinct from bulk indentation; the static response of the nanoindentation is determined almost exclusively by the elastic properties of the nonfibrillar matrix and the volume fraction of fibers, while the transient response is dominated by the fluid permeability of the tissue. The FRPE model can accurately describe the time-dependent mechanical behavior of costal cartilage in nanoindentation, with good agreement between experimental and numerical curve fits (R(2)=0.98+/-0.01) at multiple indentation depths and indentation rates.

  10. Nanoindentation study of interphases in epoxy/amine thermosetting systems modified with thermoplastics.

    PubMed

    Ramos, Jose Angel; Blanco, Miren; Zalakain, Iñaki; Mondragon, Iñaki

    2009-08-15

    The characterization of a mixture of epoxy/amine with different stoichiometric ratios was carried out by means of nanoindentation. The epoxy system was composed by diglycidyl ether of bisphenol-A and 4,4'-methylene bis-(3-chloro 2,6-diethylaniline). Diffusion through interface formed by epoxy/amine system in stoichiometric ratio and several thermoplastic polymers was also analyzed by means of stiffness analysis, as studied by atomic force microscopy (AFM) and coupled nanoindentation tests. Used thermoplastics were an amorphous, atactic polystyrene, and two semicrystalline, syndiotactic polystyrene and poly(phenylene sulfide). Larger range diffusion was obtained in epoxy/amine systems modified with atactic polystyrene while the study of the influence of stoichiometric ratio suggests that the excess of epoxy generated stiffer material. In addition, larger indentation loads resulted in higher apparent stiffness because of the more number of polymer chains that had to re-accommodate owing to the increase in contact area.

  11. In situ nanoindentation in a transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Minor, Andrew Murphy

    This dissertation presents the development of the novel mechanical testing technique of in situ nanoindentation in a transmission electron microscope (TEM). This technique makes it possible to simultaneously observe and quantify the mechanical behavior of nano-scale volumes of solids. Chapter 2 details the unique specimen preparation techniques employed to meet the geometrical constraints of the in situ experiments. These techniques include bulk silicon micromachining and the use of a focused ion beam. In section 2.4 a method of voltage-controlled mechanical testing is derived theoretically and proven experimentally. This method enables the quantification of the mechanical behavior during in situ nanoindentation experiments. Three classes of material systems were studied with this new technique: (1) bulk single crystal, (2) a soft thin film on a harder substrate and (3) a hard thin film on a softer substrate. Section 3.2 provides the first direct evidence of dislocation nucleation in single crystal silicon at room temperature. In contrast to the observation of phase transformations during conventional indentation experiments, the unique geometry employed for the in situ experiments resulted in dislocation plasticity. In section 3.3 results from in situ nanoindentation of Al films on Si substrates are presented. These results include the correlation of the microstructural deformation behavior with load vs. displacement data. It is shown that a sharp change in the force-displacement response at the elastic-to-plastic transition signifies the nucleation of dislocations. Additionally, the softening of sub-micron grains with size is observed. Section 3.4 discussed the influence of the substrate on the indentation response of two thin film/substrate systems where the films were harder than the substrate. Amorphous diamond on Si and epitaxial TiN on MgO (001) systems were studied. It was found that the deformation in the harder films was controlled by the deformation in

  12. Study on the AFM Force Spectroscopy method for elastic modulus measurement of living cells

    NASA Astrophysics Data System (ADS)

    Demichelis, A.; Pavarelli, S.; Mortati, L.; Sassi, G.; Sassi, M.

    2013-09-01

    The cell elasticity gives information about its pathological state and metastatic potential. The aim of this paper is to study the AFM Force Spectroscopy technique with the future goal of realizing a reference method for accurate elastic modulus measurement in the elasticity range of living cells. This biological range has not been yet explored with a metrological approach. Practical hints are given for the realization of a Sylgard elasticity scale. Systematic effects given by the sample curing thickness and nanoindenter geometry have been found with regards of the measured elastic modulus. AFM measurement reproducibility better than 20% is obtained in the entire investigated elastic modulus scale of 101 - 104 kPa.

  13. Dislocation luminescence in GaN single crystals under nanoindentation.

    PubMed

    Huang, Jun; Xu, Ke; Fan, Ying Min; Wang, Jian Feng; Zhang, Ji Cai; Ren, Guo Qiang

    2014-01-01

    This work presents an experimental study on the dislocation luminescence in GaN by nanoindentation, cathodoluminescence, and Raman. The dislocation luminescence peaking at 3.12 eV exhibits a series of special properties in the cathodoluminescence measurements, and it completely disappears after annealing at 500°C. Raman spectroscopy shows evidence for existence of vacancies in the indented region. A comprehensive investigation encompassing cathodoluminescence, Raman, and annealing experiments allow the assignment of dislocation luminescence to conduction-band-acceptor transition involving Ga vacancies. The nanoscale plasticity of GaN can be better understood by considering the dislocation luminescence mechanism.

  14. Low Temperature Plasticity of Olivine Determined by Nano-indentation

    NASA Astrophysics Data System (ADS)

    Skemer, P. A.; Kranjc, K.; Rouse, Z.; Flores, K.

    2015-12-01

    Earth's upper mantle is thought to deform mainly by dislocation creep, during which strain-rate and stress are related by a simple power law equation. However at much higher stresses there is a break-down in the power law relationship and strain-rate depends exponentially on stress. This phenomenon, known as low temperature plasticity, may be important in the shallow ductile or semi-brittle regions of the lithosphere, at the tips of cracks, or during high-stress laboratory experiments. Several studies have attempted to constrain the low-temperature rheology of olivine using micro-indentation or high pressure experiments. In this study we provide the first measurements of olivine rheology at low temperature using instrumented nano-indention. Although nano-indentation has been widely used in the materials sciences, its application in the Earth sciences has been very limited. Nano-indentation methods provide rheological measurements that are significantly more precise than other mechanical tests at high pressure and temperature. Moreover, experiments are rapid and largely non-destructive, so many tests can be conducted in a short amount of time. In this study, olivine single crystal and polycrystalline samples were tested using a Hysitron TI950 TriboIndenter. Temperature was varied using a cooling/heating stage from 0-175°C. Experiments were conducted under quasi-static and constant strain-rate conditions. Indentation hardness measurements were converted to uniaxial rheological properties to facilitate direct comparison with previous studies. Yield strengths for olivine range from 4.19 GPa at 175°C to 4.60 GPa at 0°C. Using various models for obstacles to dislocation motion, data are extrapolated to 0 Kelvin to extract a Peierls stress for olivine (5.32-6.45 GPa), which is at the lower end of the range of values determined in previous studies. This study demonstrates the efficacy of the nano-indentation method for the study of mineral rheology, and opens a

  15. Dynamic nanoindentation by instrumented nanoindentation and force microscopy: a comparative review

    PubMed Central

    Kalfon-Cohen, Estelle

    2013-01-01

    Summary Viscoelasticity is a complex yet important phenomenon that drives material response at different scales of time and space. Burgeoning interest in nanoscale dynamic material mechanics has driven, and been driven by two key techniques: instrumented nanoindentation and atomic force microscopy. This review provides an overview of fundamental principles in nanoindentation, and compares and contrasts these two techniques as they are used for characterization of viscoelastic processes at the nanoscale. PMID:24367751

  16. Structure-property-glass transition relationships in non-isocyanate polyurethanes investigated by dynamic nanoindentation

    NASA Astrophysics Data System (ADS)

    Weyand, Stephan; Blattmann, Hannes; Schimpf, Vitalij; Mülhaupt, Rolf; Schwaiger, Ruth

    2016-07-01

    Newly developed green-chemistry approaches towards the synthesis of non-isocyanate polyurethane (NIPU) systems represent a promising alternative to polyurethanes (PU) eliminating the need for harmful ingredients. A series of NIPU systems were studied using different nanoindentation techniques in order to understand the influence of molecular parameters on the mechanical behavior. Nanoindentation revealed a unique characteristic feature of those materials, i.e. stiffening with increasing deformation. It is argued that the origin of this observed stiffening is a consequence of the thermodynamic state of the polymer network, the molecular characteristics of the chemical building blocks and resulting anisotropic elastic response of the network structure. Flat-punch nanoindentation was applied in order to characterize the constitutive viscoelastic nature of the materials. The complex modulus shows distinct changes as a function of the NIPU network topology illustrating the influence of the chemical building blocks. The reproducibility of the data indicates that the materials are homogeneous over the volumes sampled by nanoindentation. Our study demonstrates that nanoindentation is very well-suited to investigate the molecular characteristics of NIPU materials that cannot be quantified in conventional experiments. Moreover, the technique provides insight into the functional significance of complex molecular architectures thereby supporting the development of NIPU materials with tailored properties.

  17. Structural insight into iodide uptake by AFm phases.

    PubMed

    Aimoz, Laure; Wieland, Erich; Taviot-Guého, Christine; Dähn, Rainer; Vespa, Marika; Churakov, Sergey V

    2012-04-01

    The ability of cement phases carrying positively charged surfaces to retard the mobility of (129)I, present as iodide (I(-)) in groundwater, was investigated in the context of safe disposal of radioactive waste. (125)I sorption experiments on ettringite, hydrotalcite, chloride-, carbonate- and sulfate-containing AFm phases indicated that calcium-monosulfate (AFm-SO(4)) is the only phase that takes up trace levels of iodide. The structures of AFm phases prepared by coprecipitating iodide with other anions were investigated in order to understand this preferential uptake mechanism. X-ray diffraction (XRD) investigations showed a segregation of monoiodide (AFm-I(2)) and Friedel's salt (AFm-Cl(2)) for I-Cl mixtures, whereas interstratifications of AFm-I(2) and hemicarboaluminate (AFm-OH-(CO(3))(0.5)) were observed for the I-CO(3) systems. In contrast, XRD measurements indicated the formation of a solid solution between AFm-I(2) and AFm-SO(4) for the I-SO(4) mixtures. Extended X-ray absorption fine structure spectroscopy showed a modification of the coordination environment of iodine in I-CO(3) and in I-SO(4) samples compared to pure AFm-I(2). This is assumed to be due to the introduction of stacking faults in I-CO(3) samples on one hand and due to the presence of sulfate and associated space-filling water molecules as close neighbors in I-SO(4) samples on the other hand. The formation of a solid solution between AFm-I(2) and AFm-SO(4), with a short-range mixing of iodide and sulfate, implies that AFm-SO(4) bears the potential to retard (129)I. PMID:22376086

  18. Probing the mechanical properties of dental porcelain through nanoindentation

    NASA Astrophysics Data System (ADS)

    Manda, Marianthi; Moschakis, Nikolaos; Konstantinidis, Avraam; Christophilos, Demetrios; Papadopoulou, Lambrini; Koidis, Petros; Aifantis, Elias

    2012-11-01

    The purpose of this short communication is to report on some micro/nanoscale aspects of the mechanical behavior of dental porcelain. Specimens were characterized by micro-Raman spectroscopy and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Massive nanoindentation experiments on the surface of the specimens were performed, and typical load-displacement or load-depth (P-h) curves were obtained, which in turn were used to determine the Young modulus (E) and nanoindentation hardness (n-H), based on the Oliver-Pharr method [1]. Statistical analyses were carried out to determine the Spearman’s rank correlation coefficient (Spearman’s ρ), along with non-parametric linear regression analysis by employing Kolmogorov-Smirnov and Two-Step Cluster tests. Densification due to grain boundary diffusion and open-pore elimination was revealed by SEM. EDS analysis indicated a leucite-dispersed silicate glass matrix, as well as its contamination by traces of other minerals. Raman spectroscopy supported the EDS assignments. The P-h curves suggested that inelastic deformation and material flow increases at larger depths. Spearman’s ρ value showed strong dependence of E and n-H on h, indicating the occurrence of a size effect. The logarithmic data of E and n-H as functions of h were fitted by using linear regression analysis. The data did not obey a normal distribution (as the Kolmogorov-Smirnov test showed) due to the chemical heterogeneity involved. The Two-Step Cluster analysis indicated clustering in four groups associated with the chemical heterogeneity of the surface. Similar works using nanoindentation to determine the mechanical properties of dental materials can be found, for example, in [2, 3]. Corresponding methods for extracting the values of E and n-H from P-h experimental curves can be found, for example, in [4-6].

  19. Nanomechanical measurements of hair as an example of micro-fibre analysis using atomic force microscopy nanoindentation.

    PubMed

    Clifford, Charles A; Sano, Naoko; Doyle, Peter; Seah, Martin P

    2012-03-01

    The characterisation of nanoscale surface properties of textile and hair fibres is key to developing new effective laundry and hair care products. Here, we develop nanomechanical methods to characterise fibres using an atomic force microscope (AFM) to give their nanoscale modulus. Good mounting methods for the fibre that are chemically inert, clean and give strong mechanical coupling to a substrate are important and here we detail two methods to do this. We show, for elastic nanoindentation measurements, the situation when the tip radius significantly affects the result via a function of the ratio of the radii of the tip and fibre and indicate the importance of using an AFM for such work. A valid method to measure the nanoscale modulus of fibres using AFM is thus detailed and exampled on hair to show that bleaching changes the nanoscale reduced modulus at the outer surface.

  20. Nanoindentation of Si Nanostructures: Buckling and Friction at Nanoscales

    NASA Astrophysics Data System (ADS)

    Huang, Huai; Li, Bin; Zhao, Qiu; Luo, Zhiquan; Im, Jay; Kang, Min K.; Allen, Richard A.; Cresswell, Michael W.; Huang, Rui; Ho, Paul S.

    2009-06-01

    A nanoindentation system was employed to characterize mechanical properties of silicon nanolines (SiNLs), which were fabricated by an anisotropic wet etching (AWE) process. The SiNLs had the linewidth ranging from 24 nm to 90 nm, having smooth and vertical sidewalls and the aspect ratio (height/linewidth) from 7 to 18. During indentation, a buckling instability was observed at a critical load, followed by a displacement burst without a load increase, men a full recovery of displacement upon unloading. This phenomenon was explained by two bucking modes. It was also found that the difference in friction at the contact between the indenter and SiNLs directly affected buckling response of these nanolines. The friction coefficient was estimated to be in a range of 0.02 to 0.05. For experiments with large indentation displacements, irrecoverable indentation displacements were observed due to fracture of Si nanolines, with the strain to failure estimated to be from 3.8% to 9.7%. These observations indicated that the buckling behavior of SiNLs depended on the combined effects of load, line geometry, and the friction at contact. This study demonstrated a valuable approach to fabrication of well-defined Si nanoline structures and the application of the nanoindentation method for investigation of their mechanical properties at the nanoscale.

  1. Deformation Mechanisms of Gum Metals Under Nanoindentation

    NASA Astrophysics Data System (ADS)

    Sankaran, Rohini Priya

    defect structures to applied loading, we perform ex-situ nanoindentation. Nanoindentation is a convenient method as the plastic deformation is localized and probes a nominally defect free volume of the material. We subsequently characterize the defect structures in these alloys with both conventional TEM and advanced techniques such as HAADF HRSTEM and nanoprobe diffraction. These advanced techniques allow for a more thorough understanding of the observed deformation features. The main findings from this investigation are as follows. As expected we observe that a non-equilibrium phase, o, is present in the leaner beta-stabilized alloy, ST Ref-1. We do not find any direct evidence of secondary phases in STGM, and we find the beta phase in CWGM, along with lath microstructure with subgrain structure consisting of dislocation cell networks. Upon nanoindentation, we find twinning accompanied by beta nucleation on the twin boundary in ST Ref-1 samples. This result is consistent with previous findings and is reasonable considering the alloy is unstable with respect to beta transformation. We find deformation nanotwinning in cold worked gum metals under nanoindentation, which is initially surprising. We argue that when viewed as a nanocrystalline material, such a deformation mechanism is consistent with previous work, and furthermore, a deformation nanotwinned structure does not preclude an ideal shear mechanism from operating in the alloy. Lastly, we observe continuous lattice rotations in STGM under nanoindentation via nanoprobe diffraction. With this technique, for the first time we can demonstrate that the lattice rotations are truly continuous at the nanoscale. We can quantify this lattice rotation, and find that even though the rotation is large, it may be mediated by a reasonable geometrically necessary dislocation density, and note that similar rotations are typically observed in other materials under nanoindentation. HRSTEM and conventional TEM data confirm the

  2. Initial Stages of Yield in Nanoindentation

    SciTech Connect

    Houston, J.E.; Jarausch, K.F.; Kiely, J.D.; Russell, P.E.

    1998-11-24

    We have used the Interracial Force Microscope" to perform nanoindentations on Au single- crystal surfaces. We have observed two distinct regimes of plastic deformation which are distinguished by the magnitude of discontinuities in load relaxation. At lower stresses, relaxation occurs in small deviations from elastic behavior, while at the higher stresses they take the form of large load drops often resulting in complete relaxation of the applied load. These major events create a relatively wide plastic zone that subsequently deepens more rapidly than it widens. We discuss these findings in terms of contrasting models of dislocation processes in the two regimes.

  3. Deformation Mechanisms of Gum Metals Under Nanoindentation

    NASA Astrophysics Data System (ADS)

    Sankaran, Rohini Priya

    defect structures to applied loading, we perform ex-situ nanoindentation. Nanoindentation is a convenient method as the plastic deformation is localized and probes a nominally defect free volume of the material. We subsequently characterize the defect structures in these alloys with both conventional TEM and advanced techniques such as HAADF HRSTEM and nanoprobe diffraction. These advanced techniques allow for a more thorough understanding of the observed deformation features. The main findings from this investigation are as follows. As expected we observe that a non-equilibrium phase, o, is present in the leaner beta-stabilized alloy, ST Ref-1. We do not find any direct evidence of secondary phases in STGM, and we find the beta phase in CWGM, along with lath microstructure with subgrain structure consisting of dislocation cell networks. Upon nanoindentation, we find twinning accompanied by beta nucleation on the twin boundary in ST Ref-1 samples. This result is consistent with previous findings and is reasonable considering the alloy is unstable with respect to beta transformation. We find deformation nanotwinning in cold worked gum metals under nanoindentation, which is initially surprising. We argue that when viewed as a nanocrystalline material, such a deformation mechanism is consistent with previous work, and furthermore, a deformation nanotwinned structure does not preclude an ideal shear mechanism from operating in the alloy. Lastly, we observe continuous lattice rotations in STGM under nanoindentation via nanoprobe diffraction. With this technique, for the first time we can demonstrate that the lattice rotations are truly continuous at the nanoscale. We can quantify this lattice rotation, and find that even though the rotation is large, it may be mediated by a reasonable geometrically necessary dislocation density, and note that similar rotations are typically observed in other materials under nanoindentation. HRSTEM and conventional TEM data confirm the

  4. Nanoindentation techniques for the cell walls of wood

    NASA Astrophysics Data System (ADS)

    Jakes, Joseph Eugene

    There is a recognized need in forest products research to better understand how the mechanical properties of wood derive from the basic polymer components that make up the wood. For development of new engineered wood products there is the need to understand how chemical additives and adhesives interact with wood polymers and influence properties at the cellular level. To meet these needs I have developed nanoindentation techniques for probing the mechanical properties of the cell walls in wood. There are two, key results of this research. The first is a newly invented structural compliance method for isolating the properties of local regions within materials and excluding artifacts brought about by neighboring edges including free edges and interfaces between dissimilar cell wall layers. The second consists of methods to obtain viscoplastic and viscoelastic data over as wide a range of deformation rate as possible. The broadband nanoindentation creep (BNC) technique assesses the viscoplastic properties over 5 orders of magnitude in deformation rate (-10-4 to 10 s-1). Viscoelastic measurements can be made with unloading times ranging from 0.01 to 100 s, resulting in viscoelastic data that span four orders of magnitude in frequency or inverse time (˜10-3 to 10 s-1). To demonstrate the efficacy of these techniques, experiments are performed on a range of materials including fused silica, silicon, molybdenum, siliconon-insulator layered specimen, poly (methylmetacrylate), polycarbonate, polystyrene, wood cells in loblolly pine (Pinus taeda ), and a polypropylene-wood composite. Finally, the structural compliance method and BNC are combined to explore polymeric methylene diphenyl diisocyanate (pMDI)-wood interactions. The data suggest that pMDI polymerizes in situ to create an interpenetrating polymer network.

  5. Finite-element modeling of nanoindentation

    SciTech Connect

    Knapp, J.A.; Follstaedt, D.M.; Myers, S.M.; Barbour, J.C.; Friedmann, T.A.

    1999-02-01

    Procedures have been developed based on finite-element modeling of nanoindentation data to obtain the mechanical properties of thin films and ion-beam-modified layers independently of the properties of the underlying substrates. These procedures accurately deduce the yield strength, Young{close_quote}s elastic modulus, and layer hardness from indentations as deep as 50{percent} of the layer thickness or more. We have used these procedures to evaluate materials ranging from ion implanted metals to deposited, diamond-like carbon layers. The technique increases the applicability of indentation testing to very thin layers, composite layers, and modulated compositions. This article presents an overview of the procedures involved and illustrates them with selected examples. {copyright} {ital 1999 American Institute of Physics.}

  6. Characterization of Viscoelastic Properties of Polymeric Materials Through Nanoindentation

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Bandorawalla, T.; Herring, H. M.; Gates, T. S.

    2003-01-01

    Nanoindentation is used to determine the dynamic viscoelastic properties of six polymer materials. It is shown that varying the harmonic frequency of the nanoindentation does not have any significant effect on the measured storage and loss moduli of the polymers. Agreement is found between these results and data from DMA testing of the same materials. Varying the harmonic amplitude of the nanoindentation does not have a significant effect on the measured properties of the high performance resins, however, the storage modulus of the polyethylene decreases as the harmonic amplitude increases. Measured storage and loss moduli are also shown to depend on the density of the polyethylene.

  7. Cryogenic nanoindentation size effect in [0 0 1]-oriented face-centered cubic and body-centered cubic single crystals

    NASA Astrophysics Data System (ADS)

    Lee, Seok-Woo; Meza, Lucas; Greer, Julia R.

    2013-09-01

    Cryogenic nanoindentation experiments performed on [0 0 1]-oriented single crystalline Nb, W, Al, and Au in an in situ nanomechanical instrument with customized cryogenic testing capability revealed temperature dependence on nanoindentation size effect. The Nix-Gao model, commonly used to capture indentation size effect at room temperature, does not take into account thermal effects and hence is not able to explain these experimental results where both hardness at infinite indentation depth and characteristic material length scale were found to be strong functions of temperature. Physical attributes are critically examined in the framework of intrinsic lattice resistance and dislocation cross-slip probability.

  8. Evaluation and analysis of polished fused silica subsurface quality by the nanoindenter technique

    SciTech Connect

    Ma Bin; Shen Zhengxiang; He Pengfei; Sha Fei; Wang Chunliang; Wang Bin; Ji Yiqin; Liu Huasong; Li Weihao; Wang Zhanshan

    2011-03-20

    We evaluate the subsurface quality of polished fused silica samples using the nanoindenter technique. Two kinds of samples, consisting of hundreds of nanometers and micrometers of subsurface damage layers, are fabricated by controlling the grinding and polishing processes, and the subsurface quality has been verified by the chemical etching method. Then several nanoindentation experiments are performed using the Berkovich tip to investigate the subsurface quality. Some differences are found by relative measurements in terms of the relationship between the total penetration and the peak load on the surfaces, the modulus calculated over the defined depths and from unload, and the indented morphology at a constant load near the surface collapse threshold. Finally, the capabilities of such a mechanical method for detecting subsurface flaws are discussed and analyzed.

  9. Development of a precision nanoindentation platform

    NASA Astrophysics Data System (ADS)

    Nowakowski, B. K.; Smith, D. T.; Smith, S. T.; Correa, L. F.; Cook, R. F.

    2013-07-01

    The design, construction, and performance of a surface-referenced nanoindentation instrument, termed a precision nanoindentation platform (PNP), are presented. The PNP is a symmetrically designed instrument with a centrally located indenter tip attached to a force cell for measuring the forces between the tip and a specimen. Penetration of the indenter tip into the specimen surface is measured using two proximity sensors placed symmetrically about the indenter. Each proximity sensor is attached to a piezoelectric actuator that is servo controlled to maintain the sensor and the reference frame to which it is attached at a constant height relative to the specimen surface. As the indenter tip penetrates the specimen surface, the movement of the tip relative to the two surface reference frames is measured using capacitance gauges and the average of these displacements is used as a measure of penetration depth. The current indenter is capable of applying indentation forces of up to 150 mN with a noise floor below 2 μN rms for a sampling rate of 1 kHz, and measuring displacement with 0.4 nm rms noise for the same sampling rate. The proximity sensors are capable of maintaining surface height variations of less than 1.0 nm with penetration depths of up to 10 μm. Long-term stability tests indicate a total uncertainty in indentation depth less than 10 nm for periods as long as 12 h. To demonstrate instrument accuracy, repeated indention cycles were performed on a fused silica specimen using incrementally increasing indention force. From this test, an average value of 72 GPa ± 1.5 GPa for the Young's modulus was obtained from the elastic unloading curves for 10 measurements ranging in maximum force from 5 mN to 50 mN. To demonstrate longer-term instrument stability, a poly(methyl methacrylate) specimen was subjected to a fixed 5 mN indentation force for 4 h; two distinct creep-like mechanisms were observed.

  10. Nanomechanical probing of soft matter through hydrophobic AFM tips fabricated by two-photon polymerization

    NASA Astrophysics Data System (ADS)

    Suriano, Raffaella; Zandrini, Tommaso; De Marco, Carmela; Osellame, Roberto; Turri, Stefano; Bragheri, Francesca

    2016-04-01

    Atomic force microscopy (AFM) nanoindentation of soft materials is a powerful tool for probing mechanical properties of biomaterials. Though many results have been reported in this field over the last decade, adhesion forces between the tip and the sample hinder the elastic modulus measurement when hydrophilic soft samples are investigated. Here, two-photon polymerization (2PP) technology was used to fabricate hydrophobic perfluoropolyether-based AFM tips. The hydrophobic 2PP tips allowed us to overcome the limitations of commercial and functionalized tips as well as to successfully measure the elastic modulus of medically relevant soft materials in air. Our results obtained in the characterization of poly(dimethyl siloxane) and polyethylene glycol hydrogels showed lower adhesion forces over a larger measurement range when compared to measurements performed with commercial tips. The elastic moduli measured by means of hydrophobic 2PP AFM tips were also found to be comparable to those obtained using conventional techniques for macroscopic samples. We successfully showed that the hydrophobic AFM tips developed by this highly versatile technology enable the study of mechanical properties of soft matter, benefiting from reduced sample-tip interactions, and a custom-made shape and dimension of the tips.

  11. Poroelastic response of articular cartilage by nanoindentation creep tests at different characteristic lengths.

    PubMed

    Taffetani, M; Gottardi, R; Gastaldi, D; Raiteri, R; Vena, P

    2014-07-01

    Nanoindentation is an experimental technique which is attracting increasing interests for the mechanical characterization of articular cartilage. In particular, time dependent mechanical responses due to fluid flow through the porous matrix can be quantitatively investigated by nanoindentation experiments at different penetration depths and/or by using different probe sizes. The aim of this paper is to provide a framework for the quantitative interpretation of the poroelastic response of articular cartilage subjected to creep nanoindentation tests. To this purpose, multiload creep tests using spherical indenters have been carried out on saturated samples of mature bovine articular cartilage achieving two main quantitative results. First, the dependence of indentation modulus in the drained state (at equilibrium) on the tip radius: a value of 500 kPa has been found using the large tip (400 μm radius) and of 1.7 MPa using the smaller one (25 μm). Secon, the permeability at microscopic scale was estimated at values ranging from 4.5×10(-16) m(4)/N s to 0.1×10(-16) m(4)/N s, from low to high equivalent deformation. Consistently with a poroelastic behavior, the size-dependent response of the indenter displacement disappears when characteristic size and permeability are accounted for. For comparison purposes, the same protocol was applied to intrinsically viscoelastic homogeneous samples of polydimethylsiloxane (PDMS): both indentation modulus and time response have been found size-independent. PMID:24814573

  12. Nanoindentation cannot accurately predict the tensile strength of graphene or other 2D materials.

    PubMed

    Han, Jihoon; Pugno, Nicola M; Ryu, Seunghwa

    2015-10-14

    Due to the difficulty of performing uniaxial tensile testing, the strengths of graphene and its grain boundaries have been measured in experiments by nanoindentation testing. From a series of molecular dynamics simulations, we find that the strength measured in uniaxial simulation and the strength estimated from the nanoindentation fracture force can differ significantly. Fracture in tensile loading occurs simultaneously with the onset of crack nucleation near 5-7 defects, while the graphene sheets often sustain the indentation loads after the crack initiation because the sharply concentrated stress near the tip does not give rise to enough driving force for further crack propagation. Due to the concentrated stress, strength estimation is sensitive to the indenter tip position along the grain boundaries. Also, it approaches the strength of pristine graphene if the tip is located slightly away from the grain boundary line. Our findings reveal the limitations of nanoindentation testing in quantifying the strength of graphene, and show that the loading-mode-specific failure mechanism must be taken into account in designing reliable devices from graphene and other technologically important 2D materials.

  13. Spatially resolved frequency-dependent elasticity measured with pulsed force microscopy and nanoindentation.

    PubMed

    Sweers, Kim K M; van der Werf, Kees O; Bennink, Martin L; Subramaniam, Vinod

    2012-03-21

    Recently several atomic force microscopy (AFM)-based surface property mapping techniques like pulsed force microscopy (PFM), harmonic force microscopy or Peakforce QNM® have been introduced to measure the nano- and micro-mechanical properties of materials. These modes all work at different operating frequencies. However, complex materials are known to display viscoelastic behavior, a combination of solid and fluid-like responses, depending on the frequency at which the sample is probed. In this report, we show that the frequency-dependent mechanical behavior of complex materials, such as polymer blends that are frequently used as calibration samples, is clearly measurable with AFM. Although this frequency-dependent mechanical behavior is an established observation, we demonstrate that the new high frequency mapping techniques enable AFM-based rheology with nanoscale spatial resolution over a much broader frequency range compared to previous AFM-based studies. We further highlight that it is essential to account for the frequency-dependent variation in mechanical properties when using these thin polymer samples as calibration materials for elasticity measurements by high-frequency surface property mapping techniques. These results have significant implications for the accurate interpretation of the nanomechanical properties of polymers or complex biological samples. The calibration sample is composed of a blend of soft and hard polymers, consisting of low-density polyethylene (LDPE) islands in a polystyrene (PS) surrounding, with a stiffness of 0.2 GPa and 2 GPa respectively. The spring constant of the AFM cantilever was selected to match the stiffness of LDPE. From 260 Hz to 1100 Hz the sample was imaged with the PFM method. At low frequencies (0.5-35 Hz), single-point nanoindentation was performed. In addition to the material's stiffness, the relative heights of the LDPE islands (with respect to the PS) were determined as a function of the frequency. At the lower

  14. Nanoindentation of virus capsids in a molecular model

    NASA Astrophysics Data System (ADS)

    Cieplak, Marek; Robbins, Mark O.

    2010-01-01

    A molecular-level model is used to study the mechanical response of empty cowpea chlorotic mottle virus (CCMV) and cowpea mosaic virus (CPMV) capsids. The model is based on the native structure of the proteins that constitute the capsids and is described in terms of the Cα atoms. Nanoindentation by a large tip is modeled as compression between parallel plates. Plots of the compressive force versus plate separation for CCMV are qualitatively consistent with continuum models and experiments, showing an elastic region followed by an irreversible drop in force. The mechanical response of CPMV has not been studied, but the molecular model predicts an order of magnitude higher stiffness and a much shorter elastic region than for CCMV. These large changes result from small structural changes that increase the number of bonds by only 30% and would be difficult to capture in continuum models. Direct comparison of local deformations in continuum and molecular models of CCMV shows that the molecular model undergoes a gradual symmetry breaking rotation and accommodates more strain near the walls than the continuum model. The irreversible drop in force at small separations is associated with rupturing nearly all of the bonds between capsid proteins in the molecular model, while a buckling transition is observed in continuum models.

  15. Investigation of nanoindentation for the directed self-assembly of nanostructures

    NASA Astrophysics Data System (ADS)

    Taylor, Curtis Raymund

    Quantum dots possess unique optical and electronic properties that are changing the performance paradigm of electronic and optoelectronic devices. However, the realization of some of these devices, such as, high density memory elements, crafted photonic lattices, quantum cellular automata and high efficiency arrays of light emitters and detectors hinges upon the ability to precisely control the size and location of self-assembled quantum dots and their integration across dimensional scales. Such precise control has proven to be extremely difficult because of the stochastic nature of the self-assembly process. This dissertation investigated the use of nanoindentation as a patterning technique to direct the self-assembly of nanostructures. The technique focused on perturbing surface strain energy by nanoindentation in order to mechanically bias quantum dot nucleation. Much of the novelty in the work lay in the characterization of indents created by ultra-low load (<0.2 mN) nanoindentation. Site-specific cross-sectional thinning of nanoindents (down to 100 nm in size) was achieved using the in-situ 'lift-out' technique. This allowed for observation of the deformation mechanisms of GaAs at depths and dimensions approaching the threshold of plasticity. Transmission electron microscopy (TEM) revealed that the crystal deforms solely by dislocation activity with no evidence of stacking faults, twinning, fracture, or phase transformation. It was shown that the single phase deformation of GaAs could be well characterized and controlled, thereby allowing for subsequent single crystal growth on the indent. Growth of InAs quantum dots on indent patterns was performed using molecular beam epitaxy (VIBE). The effect of indent spacing and size on the patterned growth was investigated. The structural analysis of the quantum dots including spatial ordering, size, and shape were characterized by ex-situ atomic force microscopy (AFM). Results revealed that the indent patterns clearly

  16. AFM investigation of Martian soil simulants on micromachined Si substrates.

    PubMed

    Vijendran, S; Sykulska, H; Pike, W T

    2007-09-01

    The micro and nanostructures of Martian soil simulants with particles in the micrometre-size range have been studied using a combination of optical and atomic force microscopy (AFM) in preparation for the 2007 NASA Phoenix Mars Lander mission. The operation of an atomic force microscope on samples of micrometre-sized soil particles is a poorly investigated area where the unwanted interaction between the scanning tip and loose particles results in poor image quality and tip contamination by the sample. In order to mitigate these effects, etched silicon substrates with a variety of features have been used to facilitate the sorting and gripping of particles. From these experiments, a number of patterns were identified that were particularly good at isolating and immobilizing particles for AFM imaging. This data was used to guide the design of micromachined substrates for the Phoenix AFM. Both individual particles as well as aggregates were successfully imaged, and information on sizes, shapes and surface morphologies were obtained. This study highlights both the strengths and weaknesses of AFM for the potential in situ investigation of Martian soil and dust. Also presented are more general findings of the limiting operational constraints that exist when attempting the AFM of high aspect ratio particles with current technology. The performance of the final designs of the substrates incorporated on Phoenix will be described in a later paper. PMID:17760618

  17. Thermo-magnetic behaviour of AFM-MFM cantilevers

    NASA Astrophysics Data System (ADS)

    Kumar, M.; Arinero, R.; Bergez, W.; Tordjeman, Ph

    2015-08-01

    Atomic force microscopy (AFM) experiments were performed to study the behaviour of AFM cantilevers under an external magnetic field B and temperature field produced by a coil with an iron core. Four cantilever types were studied. Forces were measured for different B values and at various coil-to-cantilever separation distances. The results were analysed on the basis of a phenomenological model. This model contains the contribution of two terms, one monopole-monopole interaction at short distance, and one apparent paramagnetic interaction in \

  18. New topics on nanoindentation of polymers and composite materials

    NASA Astrophysics Data System (ADS)

    Martinez Hernandez, Ricardo

    In this study, nanoindentation was used to determine Young's modulus of homogeneous plastic materials as well as inhomogeneous epoxy woven fabric composites using various indenters. In the first part, homogeneous PMMA and polycarbonate were characterized using conical and spherical indenters. The conventional approach of the inverse analysis was modified in order to account for effects obtained during spherical nanoindentation. The experimental results were verified using FEA analysis in ABAQUS. It was found that viscous effects were present in conical nanoindentations which led to an overestimation of contact stiffness. The second part, the response of carbon and glass fiber woven fabric epoxy composites was investigated using Berkovich and spherical indenters. Localized nanoindentation was performed using the Berkovich probe in both materials which led to determination of glass fibers and matrix stiffnesses. The anisotropic nature of the response was treated modifying the classical approach to calculate transverse modulus of a unidirectional composite. Finally, fiber volume ratios were calculated according to type of composite and indenter used.

  19. In situ nanoindentation in a transmission electron microscope

    SciTech Connect

    Minor, Andrew M.

    2002-12-02

    This dissertation presents the development of the novel mechanical testing technique of in situ nanoindentation in a transmission electron microscope (TEM). This technique makes it possible to simultaneously observe and quantify the mechanical behavior of nano-scale volumes of solids.

  20. Novel Polymer Linkers for Single Molecule AFM Force Spectroscopy

    PubMed Central

    Tong, Zenghan; Mikheikin, Andrey; Krasnoslobodtsev, Alexey; Lv, Zhengjian; Lyubchenko, Yuri L.

    2013-01-01

    Flexible polymer linkers play an important role in various imaging and probing techniques that require surface immobilization, including atomic force microscopy (AFM). In AFM force spectroscopy, polymer linkers are necessary for the covalent attachment of molecules of interest to the AFM tip and the surface. The polymer linkers tether the molecules and provide their proper orientation in probing experiments. Additionally, the linkers separate specific interactions from nonspecific short-range adhesion and serve as a reference point for the quantitative analysis of single molecule probing events. In this report, we present our results on the synthesis and testing of a novel polymer linker and the identification of a number of potential applications for its use in AFM force spectroscopy experiments. The synthesis of the linker is based on the well-developed phosphoramidate (PA) chemistry that allows the routine synthesis of linkers with predetermined lengths and PA composition. These linkers are homogeneous in length and can be terminated with various functional groups. PA linkers with different functional groups were synthesized and tested in experimental systems utilizing different immobilization chemistries. We probed interactions between complementary DNA oligonucleotides; DNA and protein complexes formed by the site-specific binding protein SfiI; and interactions between amyloid peptide (Aβ42). The results of the AFM force spectroscopy experiments validated the feasibility of the proposed approach for the linker design and synthesis. Furthermore, the properties of the tether (length, functional groups) can be adjusted to meet the specific requirements for different force spectroscopy experiments and system characteristics, suggesting that it could be used for a large number of various applications. PMID:23624104

  1. CD-AFM reference metrology at NIST and SEMATECH

    NASA Astrophysics Data System (ADS)

    Dixson, Ronald; Fu, Joseph; Orji, Ndubuisi; Guthrie, William; Allen, Richard; Cresswell, Michael

    2005-05-01

    The National Institute of Standards and Technology (NIST) and SEMATECH have been working together to improve the traceability of critical dimension atomic force microscope (CD-AFM) dimensional metrology in semiconductor manufacturing. A major component of this collaboration has been the implementation of a Reference Measurement System (RMS) at SEMATECH using a current generation CD-AFM. An earlier tool, originally used at SEMATECH, has now been installed at NIST. Uncertainty budgets were developed for pitch, height, and CD measurements using both tools. At present, the standard uncertainties are approximately 0.2 % for pitch measurements and 0.4% for step height measurements. Prior to the current work, CD AFM linewidth measurements were limited to a standard uncertainty of about 5 nm. However, this limit can now be significantly reduced. This reduction results from the completion of the NIST/SEMATECH collaboration on the development of single crystal critical dimension reference materials (SCDDRM). A new generation of these reference materials was released to SEMATECH Member Companies during late 2004. The SEMATECH RMS was used to measure the linewidths of selected features on the distributed specimens. To reduce the uncertainty in tip width calibration, a separate transfer experiment was performed in which samples were measured by CD-AFM and then sent for high resolution transmission electron microscopy (HRTEM). In this manner, CD-AFM could be used to transfer the HRTEM width information to the distributed samples. Consequently, we are now able to reduce the limit on the standard uncertainty (k = 1) of CD-AFM width measurements to 1 nm.

  2. Structural, Nanomechanical and Nanotribological Characterization of Human Hair Using Atomic Force Microscopy and Nanoindentation

    NASA Astrophysics Data System (ADS)

    Bhushan, Bharat; Latorre, Carmen; Wei, Guohua

    Human hair is a nanocomposite biological fiber. Healthy, soft hair with good feel, shine, color and overall aesthetics is generally highly desirable. It is important to study hair care products such as shampoos and conditioners as well as damaging processes such as chemical dyeing and permanent wave treatments because they affect the maintenance and grooming process and therefore alter many hair properties. Nanoscale characterization of the cellular structure, the mechanical properties, as well as the morphological, frictional and adhesive properties (tribological properties) of hair is essential if we wish to evaluate and develop better cosmetic products, and crucial to advancing the understanding of biological and cosmetic science. The atomic/friction force microscope (AFM/FFM) and nanoindenter have recently become important tools for studying the micro/nanoscale properties of human hair. In this chapter, we present a comprehensive review of structural, mechanical, and tribological properties of various hair and skin as a function of ethnicity, damage, conditioning treatment, and various environments. Various cellular structures of human hair and fine sublamellar structures of the cuticle are identified and studied. Nanomechanical properties such as hardness, elastic modulus, creep and scratch resistance are discussed. Nanotribological properties such as roughness, friction, and adhesion are presented, as well as investigations of conditioner distribution, thickness and binding interactions.

  3. Investigation of Oxidation Profile in PMR-15 Polyimide using Atomic Microscope (AFM)

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Johnson, Lili L.; Eby, R. K.

    2002-01-01

    Nanoindentation measurements are made on thermosetting materials using cantiever deflection vs. piezoelectric scanner position behavior determined by AFM. The spring model is used to determine mechanical properties of materials. The generalized Sneddon's equation is utilized to calculate Young's moduli for thermosetting materials at ambient conditions. Our investigations show that the force-penetration depth curves during unloading in these materials can be described accurately by a power law relationship. The results show that the accuracy of the measurements can be controlled within 7%. The above method is used to study oxidation profiles in Pl\\1R-15 polyimide. The thermo-mechanical profiles ofPNIR-15 indicate that the elastic modulus at the surface portion of the specimen is different from that at the interior of the material. It is also shown that there are two zones within the oxidized portion of the samples. Results confirm that the surface layer and the core material have substantially different properties.

  4. Young's modulus of peritubular and intertubular human dentin by nano-indentation tests.

    PubMed

    Ziskind, Daniel; Hasday, Moran; Cohen, Sidney R; Wagner, H Daniel

    2011-04-01

    The local Young modulus of dry dentin viewed as a hierarchical composite was measured by nano-indentation using two types of experiments, both in a continuous stiffness measurement mode. First, tests were performed radially along straight lines running across highly mineralized peritubular dentin sections and through less mineralized intertubular dentin areas. These tests revealed a gradual decrease in Young's modulus from the bulk of the peritubular dentin region where modulus values of up to ∼40-42GPa were observed, down to approximately constant values of ∼17GPa in the intertubular dentin region. A second set of nano-indentation experiments was performed on the facets of an irregular polyhedron specimen cut from the intertubular dentin region, so as to probe the modulus of intertubular dentin specimens at different orientations relative to the tubular direction. The results demonstrated that the intertubular dentin region may be considered to be quasi-isotropic, with a slightly higher modulus value (∼22GPa) when the indenting tip axis is parallel to the tubular direction, compared to the values (∼18GPa) obtained when the indenting tip axis is perpendicular to the tubule direction.

  5. Hydrodynamic effects in fast AFM single-molecule force measurements.

    PubMed

    Janovjak, Harald; Struckmeier, Jens; Müller, Daniel J

    2005-02-01

    Atomic force microscopy (AFM) allows the critical forces that unfold single proteins and rupture individual receptor-ligand bonds to be measured. To derive the shape of the energy landscape, the dynamic strength of the system is probed at different force loading rates. This is usually achieved by varying the pulling speed between a few nm/s and a few microm/s, although for a more complete investigation of the kinetic properties higher speeds are desirable. Above 10 microm/s, the hydrodynamic drag force acting on the AFM cantilever reaches the same order of magnitude as the molecular forces. This has limited the maximum pulling speed in AFM single-molecule force spectroscopy experiments. Here, we present an approach for considering these hydrodynamic effects, thereby allowing a correct evaluation of AFM force measurements recorded over an extended range of pulling speeds (and thus loading rates). To support and illustrate our theoretical considerations, we experimentally evaluated the mechanical unfolding of a multi-domain protein recorded at 30 microm/s pulling speed. PMID:15257425

  6. Plastic deformation in zirconium nitride observed by nanoindentation and TEM

    NASA Astrophysics Data System (ADS)

    Egeland, G. W.; Wheeler, K.; Peralta, P.; McClellan, K. J.; Maloy, S. A.; Bond, G. M.

    2011-09-01

    A study on zirconium nitride using TEM and nanoindentation was performed to assess the significant surface plasticity found to be introduced by sample polishing. Cross-sectional TEM results show strong evidence of plasticity via dislocations produced directly from surface grinding and polishing. These dislocations were found to glide on the {0 1 1}<0 1¯ 1> slip system. Using nanoindentation to observe the effects of surface dislocation density, a critical shear stress was found that relates to dislocations nucleation and multiplication. Continued chemo-mechanical polishing increased the critical shear stress to approximately 1600 mN by reducing surface dislocations. It is postulated that vacancy clusters and oxide microcrystallites produced during surface processing provide dislocation nucleation and/or multiplication sites. Gentle chemo-mechanical polishing for several hours greatly reduced or eliminated preexisting dislocations such that the critical shear stress for nucleation approaches the theoretical limit (˜ G/5).

  7. Invited Article: Indenter materials for high temperature nanoindentation.

    PubMed

    Wheeler, J M; Michler, J

    2013-10-01

    As nanoindentation at high temperatures becomes increasingly popular, a review of indenter materials for usage at high temperatures is instructive for identifying appropriate indenter-sample materials combinations to prevent indenter loss or failure due to chemical reactions or wear during indentation. This is an important consideration for nanoindentation as extremely small volumes of reacted indenter material will have a significant effect on measurements. The high temperature hardness, elastic modulus, thermal properties, and chemical reactivities of diamond, boron carbide, silicon carbide, tungsten carbide, cubic boron nitride, and sapphire are discussed. Diamond and boron carbide show the best elevated temperature hardness, while tungsten carbide demonstrates the lowest chemical reactivity with the widest array of elements.

  8. Dislocation nucleation in bcc Ta single crystals studied by nanoindentation

    SciTech Connect

    Biener, M M; Biener, J; Hodge, A M; Hamza, A V

    2007-08-08

    The study of dislocation nucleation in closed-packed metals by nanoindentation has recently attracted much interest. Here, we address the peculiarities of the incipient plasticity in body centered cubic (bcc) metals using low index Ta single-crystals as a model system. The combination of nanoindentation with high-resolution atomic force microscopy provides us with experimental atomic-scale information on the process of dislocation nucleation and multiplication. Our results reveal a unique deformation behavior of bcc Ta at the onset of plasticity which is distinctly different from that of closed-packed metals. Most noticeable, we observe only one rather than a sequence of discontinuities in the load-displacement curves. This and other differences are discussed in context of the characteristic plastic deformation behavior of bcc metals.

  9. ezAFM: A low cost Atomic Force Microscope(AFM)

    NASA Astrophysics Data System (ADS)

    Celik, Umit; Celik, Kubra; Aslan, Husnu; Kehribar, Ihsan; Dede, Munir; Ozgur Ozer, H.; Oral, Ahmet

    2012-02-01

    A low cost AFM, ezAFM is developed for educational purposes as well as research. Optical beam deflection method is used to measure the deflection of cantilever. ezAFM scanner is built using voice coil motors (VCM) with ˜50x50x6 μm scan area. The microscope uses alignment free cantilevers, which minimizes setup times. FPGA based AFM feedback Control electronics is developed. FPGA technology allows us to drive all peripherals in parallel. ezAFM Controller is connected to PC by USB 2.0 interface as well as Wi-Fi. We have achieved <5nm lateral and ˜0.01nm vertical resolution. ezAFM can image single atomic steps in HOPG and mica. An optical microscope with <3 μm resolution is also integrated into the system. ezAFM supports different AFM operation modes such as dynamic mode, contact mode, lateral force microscopy. Advanced modes like magnetic force microscopy and electric force microscopy will be implemented later on. The new ezAFM system provides, short learning times for student labs, quick setup and easy to transport for portable applications with the best price/performance ratio. The cost of the system starts from 15,000, with system performance comparable with the traditional AFM systems.

  10. Thin film adhesion by nanoindentation-induced superlayers. Final report

    SciTech Connect

    Gerberich, William W.; Volinsky, A.A.

    2001-06-01

    This work has analyzed the key variables of indentation tip radius, contact radius, delamination radius, residual stress and superlayer/film/interlayer properties on nanoindentation measurements of adhesion. The goal to connect practical works of adhesion for very thin films to true works of adhesion has been achieved. A review of this work titled ''Interfacial toughness measurements of thin metal films,'' which has been submitted to Acta Materialia, is included.

  11. Nano-indentation study on the (001) face of KDP crystal based on SPH method

    NASA Astrophysics Data System (ADS)

    Xiaoguang, Guo; Ziyuan, Liu; Hang, Gao; Dongming, Guo

    2015-08-01

    In order to avoid the defects of mesh distortion when dealing with large deformation problems through using the finite element method, a mess-free simulation method—smooth particle hydrodynamics (SPH) has been introduced. The material constitutive model of KDP crystal has been established based on the elastic-plastic theory. Then the nano-indentation on the (001) face of KDP crystal has been carried out using SPH method. Simulation results show that the maximum equivalent stress and the maximum plastic strain concentrate on the area that located near the tip of the indenter during the loading process. The distribution shape of Von Mises stress is similar to concentric circles. During the unloading process, no obvious variation of plastic strain distribution exists. The maximum Von Mises stress is mainly located at the indentation and its edge at the end of the unloading process. The approximate direct proportion relationship between the maximum indentation depth and the depth of the maximum Von Mises stress distribution has been discovered when the maximum load is lower than 8 mN. In addition, the nano-indentation experiments on KDP crystal's (001) face have been carried out. Both the material parameters and the adjusted stress-strain curve have been verified. The hindering role of the affected layer has been found and analyzed. Project supported by the National Basic Research Program of China (No. 51135002), and the Science Fund for Creative Research Groups (No. 51321004).

  12. Nano Mechanical Machining Using AFM Probe

    NASA Astrophysics Data System (ADS)

    Mostofa, Md. Golam

    Complex miniaturized components with high form accuracy will play key roles in the future development of many products, as they provide portability, disposability, lower material consumption in production, low power consumption during operation, lower sample requirements for testing, and higher heat transfer due to their very high surface-to-volume ratio. Given the high market demand for such micro and nano featured components, different manufacturing methods have been developed for their fabrication. Some of the common technologies in micro/nano fabrication are photolithography, electron beam lithography, X-ray lithography and other semiconductor processing techniques. Although these methods are capable of fabricating micro/nano structures with a resolution of less than a few nanometers, some of the shortcomings associated with these methods, such as high production costs for customized products, limited material choices, necessitate the development of other fabricating techniques. Micro/nano mechanical machining, such an atomic force microscope (AFM) probe based nano fabrication, has, therefore, been used to overcome some the major restrictions of the traditional processes. This technique removes material from the workpiece by engaging micro/nano size cutting tool (i.e. AFM probe) and is applicable on a wider range of materials compared to the photolithographic process. In spite of the unique benefits of nano mechanical machining, there are also some challenges with this technique, since the scale is reduced, such as size effects, burr formations, chip adhesions, fragility of tools and tool wear. Moreover, AFM based machining does not have any rotational movement, which makes fabrication of 3D features more difficult. Thus, vibration-assisted machining is introduced into AFM probe based nano mechanical machining to overcome the limitations associated with the conventional AFM probe based scratching method. Vibration-assisted machining reduced the cutting forces

  13. Simultaneous AFM nano-patterning and imaging for photomask repair

    NASA Astrophysics Data System (ADS)

    Keyvani, Aliasghar; Tamer, Mehmet S.; van Es, Maarten H.; Sadeghian, Hamed

    2016-03-01

    In this paper we present a new AFM based nano-patterning technique that can be used for fast defect repairing of high resolution photomasks and possibly other high-speed nano-patterning applications. The proposed method works based on hammering the sample with tapping mode AFM followed by wet cleaning of the residuals. On the area where a specific pattern should be written, the tip-sample interaction force is tuned in a controlled manner by changing the excitation frequency of the cantilever without interrupting the imaging process. Using this method several patterns where transferred to different samples with imaging speed. While the pattern was transferred to the sample in each tracing scan line, the patterned sample was imaged in retracing scan line, thus the outcome was immediately visible during the experiment.

  14. AFM Investigation of mechanical properties of dentin

    SciTech Connect

    Cohen, Sidney R; Apter, Nathan; Jesse, Stephen; Kalinin, Sergei V; Barlam, David; Peretz, Adi Idit; Ziskind, Daniel; Wagner, H. Daniel

    2008-01-01

    Mechanical properties of peritubular dentin were investigated using scanning probe microscopy techniques, namely Nanoindentation and Band Excitation. Particular attention was directed to the possible existence of a gradient in these properties moving outward from the tubular lumen to the junction with the intertubular dentin. Finite element analysis showed that the influence of the boundaries is small relative to the effects observed. Thus, these results strongly support the concept of a lowering of modulus and hardness from the tubular exterior to its periphery, which appear to correlate with graded changes in the mineral content.

  15. Extracting nanobelt mechanical properties from nanoindentation

    NASA Astrophysics Data System (ADS)

    Zhang, Yin

    2010-06-01

    A three-spring-in-series model is proposed for the nanobelt (NB) indentation test. Compared with the previous two-spring-in-series model, which considers the bending stiffness of atomic force microscope cantilever and the indenter/NB contact stiffness, this model adds a third spring of the NB/substrate contact stiffness. NB is highly flexural due to its large aspect ratio of length to thickness. The bending and lift-off of NB form a localized contact with substrate, which makes the Oliver-Pharr method [W. C. Oliver and G. M. Pharr, J. Mater. Res. 7, 1564 (1992)] and Sneddon method [I. N. Sneddon, Int. J. Eng. Sci. 3, 47 (1965)] inappropriate for NB indentation test. Because the NB/substrate deformation may have significant impact on the force-indentation depth data obtained in experiment, the two-spring-in-series model can lead to erroneous predictions on the NB mechanical properties. NB in indentation test can be susceptible to the adhesion influence because of its large surface area to volume ratio. NB/substrate contact and adhesion can have direct and significant impact on the interpretation of experimental data. Through the three-spring-in-series model, the influence of NB/substrate contact and adhesion is analyzed and methods of reducing such influence are also suggested.

  16. Nanoindentation. Simulation of defect nucleation in a crystal.

    PubMed

    Gouldstone, A; Van Vliet, K J; Suresh, S

    2001-06-01

    Nanoindentation is the penetration of a surface to nanometre depths using an indenting device. It can be simulated using the Bragg bubble-raft model, in which a close-packed array of soap bubbles corresponds to the equilibrium positions of atoms in a crystalline solid. Here we show that homogeneous defect nucleation occurs within a crystal when its surface roughness is comparable to the radius of the indenter tip, and that the depth of the nucleation site below the surface is proportional to the half-width of the contact. Our results may explain the unusually high local stress required for defect nucleation in nano-indented face-centred cubic crystals.

  17. Nanoindentation studies of nickel zinc ferrite embedded mesoporous silica template

    NASA Astrophysics Data System (ADS)

    Banerjee, S.; Hajra, P.; Mada, M. R.; Bandopadhyay, S.; Chakravorty, D.

    2013-02-01

    Nickel zinc ferrite (NZF) embedded mesoporous silica KIT-6 nanocomposite (NZFMS) was synthesized via impregnation method. The microstructure of the samples was characterized by transmission electron microscopy (TEM). Nanoindentation (NI) studies were carried out on both mesoporous silica (MS) and the nanocomposite NZFMS. It was found that the young's modulus (E) and hardness (H) of the NZFMS were higher than that of the MS. From creep measurement it was observed that the creep-strain rate was greater for NZFMS compared to MS. This arose due to diffusion of Fe3+ ions from nickel zinc ferrite to the silica glass. The results indicate that the NZFMS material shows superplastic behaviour at room temperature.

  18. Peculiarities of plastic deformation nucleation in copper under nanoindentation

    SciTech Connect

    Kryzhevich, Dmitrij S. Korchuganov, Aleksandr V.; Zolnikov, Konstantin P.; Psakhie, Sergey G.

    2015-10-27

    The computer simulation results on the atomic structure of the copper crystallite and its behavior in nanoindentation demonstrate the key role of local structural transformations in nucleation of plasticity. The generation of local structural transformations can be considered as an elementary event during the formation of higher scale defects, including partial dislocations and stacking faults. The cause for local structural transformations, both direct fcc-hcp and reverse hcp-fcc, is an abrupt local increase in atomic volume. A characteristic feature is that the values of local volume jumps in direct and reverse structural transformations are comparable with that in melting and lie in the range 5–7%.

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

    PubMed

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

    2014-11-01

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

  20. Hydration states of AFm cement phases

    SciTech Connect

    Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Wadsö, Lars

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  1. Extraction of elastic modulus of porous ultra-thin low-k films by two-dimensional finite-element simulations of nanoindentation

    NASA Astrophysics Data System (ADS)

    Okudur, O. O.; Vanstreels, K.; De Wolf, I.; Hangen, U.

    2016-01-01

    Continuous scaling of integrated circuits has led to the introduction of highly porous low dielectric constant (low-k) materials, whose inferior mechanical properties raise concerns regarding the reliability of integrated circuits. Nanoindentation is proven to be a straightforward method to study mechanical properties of films. However, in the case of low-k, the measurement and analysis are complex due to the porous nature of the films and reduced film thicknesses which give rise to substrate effects. A methodology that combines nanoindentation experiments with finite-element simulations is proposed and validated in this study to extract the substrate-free elastic modulus of porous ultra-thin low-k films. Furthermore, it is shown that imperfections of the nanoindentation probe significantly affect the finite-element results. An effective analytical method that captures the actual nanoindenter behavior upon indentation is proposed by taking both tip radius and conical imperfections into account. Using this method combined with finite element modeling, the elastic modulus of sub-100 nm thick low-k films is successfully extracted. Standard indentation tests clearly overestimated the actual modulus for such thin films, which emphasizes the importance of the proposed methodology.

  2. LET Spectrum Measurements In CR-39 PNTD With AFM

    SciTech Connect

    Johnson, C. E.; DeWitt, J. M.; Benton, E. R.; Yasuda, N.; Benton, E. V.

    2011-06-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range ({approx}<10 {mu}m) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching ({approx}<1 {mu}m) following by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features inherently present in the post-etch detector surface. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/{mu}m. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to 1 GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  3. LET Spectrum Measurements In CR-39 PNTD With AFM

    NASA Astrophysics Data System (ADS)

    Johnson, C. E.; DeWitt, J. M.; Benton, E. R.; Yasuda, N.; Benton, E. V.

    2011-06-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range (˜<10 μm) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching (˜<1 μm) following by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features inherently present in the post-etch detector surface. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/μm. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to 1 GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  4. Quantitative nano-mechanics of biological cells with AFM

    NASA Astrophysics Data System (ADS)

    Sokolov, Igor

    2013-03-01

    The importance of study of living cells is hard to overestimate. Cell mechanics is a relatively young, yet not a well-developed area. Besides just a fundamental interest, large practical need has emerged to measure cell mechanics quantitatively. Recent studies revealed a significant correlation between stiffness of biological cells and various human diseases, such as cancer, malaria, arthritis, and even aging. However, really quantitative studies of mechanics of biological cells are virtually absent. It is not even clear if the cell, being a complex and heterogeneous object, can be described by the elastic modulus at all. Atomic force microscopy (AFM) is a natural instrument to study properties of cells in their native environments. Here we will demonstrate that quantitative measurements of elastic modulus of cells with AFM are possible. Specifically, we will show that the ``cell body'' (cell without ``brush'' surface layer, a non-elastic layer surrounding cells) typically demonstrates the response of a homogeneous elastic medium up to the deformation of 10-20%, but if and only if a) the cellular brush layer is taken into account, b) rather dull AFM probes are used. This will be justified with the help of the strong condition of elastic behavior of material: the elastic modulus is shown to be independent on the indentation depth. We will also demonstrate that an attempt either to ignore the brush layer or to use sharp AFM probes will result in the violation of the strong condition, which implies impossibility to use the concept of the elastic modulus to describe cell mechanics in such experiments. Examples of quantitative measurements of the Young's modulus of the cell body and the cell brush parameters will be given for various cells. Address when submitting: Clarkson University, Potsdam, NY 13699

  5. LET spectrum measurements in Cr-39 PNTD with AFM

    SciTech Connect

    Johnson, Carl Edward; De Witt, Joel M; Benton, Eric R; Yasuda, Nakahiro; Benton, Eugene V

    2010-01-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range ({approx}< 10 {mu}m) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching ({approx}< 1 {mu}m) followed by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/{mu}m. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to I GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  6. Material properties of brachiopod shell ultrastructure by nanoindentation.

    PubMed

    Pérez-Huerta, Alberto; Cusack, Maggie; Zhu, Wenzhong; England, Jennifer; Hughes, John

    2007-02-22

    Mineral-producing organisms exert exquisite control on all aspects of biomineral production. Among shell-bearing organisms, a wide range of mineral fabrics are developed reflecting diverse modes of life that require different material properties. Our knowledge of how biomineral structures relate to material properties is still limited because it requires the determination of these properties on a detailed scale. Nanoindentation, mostly applied in engineering and materials science, is used here to assess, at the microstructural level, material properties of two calcite brachiopods living in the same environment but with different modes of life and shell ultrastructure. Values of hardness (H) and the Young modulus of elasticity (E) are determined by nanoindentation. In brachiopod shells, calcite semi-nacre provides a harder and stiffer structure (H approximately 3-6 GPa; E=60-110/120 GPa) than calcite fibres (H=0-3 GPa; E=20-60/80 GPa). Thus, brachiopods with calcite semi-nacre can cement to a substrate and remain immobile during their adult life cycle. This correlation between mode of life and material properties, as a consequence of ultrastructure, begins to explain why organisms produce a wide range of structures using the same chemical components, such as calcium carbonate.

  7. Effect of Crystal Orientation on Nanoindentation Behavior in Magnesium

    NASA Astrophysics Data System (ADS)

    Somekawa, Hidetoshi; Schuh, Christopher A.

    2016-06-01

    The effect of crystal orientation on nanoindentation behavior at both quasi-static and high strain rates was investigated using single-crystalline magnesium oriented in basal and prismatic configurations. Both the basal and prismatic planes had similar activation volumes, 55 and 73 b 3 for deformation at room temperature, as well as a small temperature dependence up to 423 K (150 °C). Microstructural observations beneath the indentations revealed that { 10bar{1}2 } type deformation twins were formed in both orientations irrespective of testing temperature. With twins forming beneath the indenter and multiple orientations of loading, it is believed that cross-slip and/or multiple slip are likely rate-controlling for global deformation, which also aligns with observations on nanoindentation of polycrystalline coarse-grained magnesium. The locations of the twins were consistent with expectations based on indentation mechanics as assessed by finite element simulations. The finite element simulations also predicted that an indenter tip with a shaper tip radius would tend to promote { 10bar{1}2 } twins.

  8. Nanoindentation and the micromechanics of Van Gogh oil paints

    NASA Astrophysics Data System (ADS)

    Salvant, Johanna; Barthel, Etienne; Menu, Michel

    2011-08-01

    Understanding the mechanical properties of ancient paintings is a major issue for conservation and restoration. One strategy is to measure the mechanical properties of reconstructed paints: however, the aging process is poorly known, so it is also desirable to measure mechanical properties directly on ancient paint samples. Using nanoindentation, we have characterized submillimetric samples recovered from restoration of two Van Gogh paintings and compared the results with reconstructed paint samples. We demonstrate that the reduced modulus and hardness of historical paints can be measured at a very local scale, even differentiating between each paint layer. Our reconstructed paint samples exhibit elastic moduli comparable to values of the literature, but the values measured on the two 19th century paint samples are found to be significantly larger. Similarly, the compositional dependence of the elastic modulus is consistent with literature results for our reconstructed samples while our preliminary results for ancient samples do not readily fall into the same pattern. These results all point out to a significant impact of long term aging, in a manner which is difficult to predict in our present state of understanding. They demonstrate that nanoindentation is a very adequate tool to improve our knowledge of art paint mechanics and aging.

  9. Contact nanomechanical measurements with the AFM

    NASA Astrophysics Data System (ADS)

    Geisse, Nicholas

    2013-03-01

    The atomic force microscope (AFM) has found broad use in the biological sciences largely due to its ability to make measurements on unfixed and unstained samples under liquid. In addition to imaging at multiple spatial scales ranging from micro- to nanometer, AFMs are commonly used as nanomechanical probes. This is pertinent for cell biology, as it has been demonstrated that the geometrical and mechanical properties of the extracellular microenvironment are important in such processes as cancer, cardiovascular disease, muscular dystrophy, and even the control of cell life and death. Indeed, the ability to control and quantify these external geometrical and mechanical parameters arises as a key issue in the field. Because AFM can quantitatively measure the mechanical properties of various biological samples, novel insights to cell function and to cell-substrate interactions are now possible. As the application of AFM to these types of problems is widened, it is important to understand the performance envelope of the technique and its associated data analyses. This talk will discuss the important issues that must be considered when mechanical models are applied to real-world data. Examples of the effect of different model assumptions on our understanding of the measured material properties will be shown. Furthermore, specific examples of the importance of mechanical stimuli and the micromechanical environment to the structure and function of biological materials will be presented.

  10. A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette

    PubMed Central

    Roder, Phillip; Hille, Carsten

    2015-01-01

    Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force- and pressure-controlled microscale liquid dispenser. This frontloading procedure seems especially attractive when using target substances featuring high costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few μL using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy. PMID:26636981

  11. A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette.

    PubMed

    Roder, Phillip; Hille, Carsten

    2015-01-01

    Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force- and pressure-controlled microscale liquid dispenser. This frontloading procedure seems especially attractive when using target substances featuring high costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few μL using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy. PMID:26636981

  12. A Nanoindentation Study on Grain-Boundary Contributions to Strengthening and Aging Degradation Mechanisms in Advanced 12Cr Ferritic Steel

    SciTech Connect

    Jang, Jae-il; Shim, Sang Hoon; Komazaki, Shin-ichi; Honda, Tetsuya

    2007-01-01

    Nanoindentation experiments and microstructural analysis were performed on advanced 12% Cr ferritic steel having extremely fine and complex martensitic microstructures, to answer unsolved questions on the contributions of grain boundaries to strengthening and aging degradation mechanisms in both as-tempered and thermally aged steels. Interesting features of the experimental results led us to suggest that among several high angle boundaries, block boundary is most effective in enhancing the macroscopic strength in as-tempered virgin sample, and that a decrease in matrix strength rather than reduction in grain-boundary strengthening effect is primarily responsible for the macroscopic softening behavior observed during thermal exposure.

  13. Fracture toughness of bleached enamel: Effect of applying three different nanobiomaterials by nanoindentation test

    PubMed Central

    Khoroushi, Maryam; Mazaheri, Hamid; Saneie, Tahere; Samimi, Pouran

    2016-01-01

    Background: Despite the absence of dispute about the efficacy of bleaching agents, a prime concern is about their compromising effect on the enamel structure. This in vitro study investigated whether the addition of three different biomaterials, including nano-bioactive glass (n-BG)/nano-hydroxy apetite (n-HA)/nano-amorphous calcium phosphate (n-ACP), to bleaching agents can affect the fracture toughness (FT) and vickers hardness number (VHN) of bovine enamel. Materials and Methods: The crowns of the newly extracted permanent bovine incisors teeth were separated from the root and sectioned along their central line; one half serving as the control specimen and the other half as the test specimen. After mounting and polishing procedure, all the control specimens (C) were subjected to nano-indentation test to obtain the baseline values of FT. Then, the control specimens were exposed to a 38% hydrogen peroxide for four times, each time for 10 min. The test specimens were divided into three groups and treated as follows, with the same protocol used for the control specimens: Group 1; ACP + hydrogen peroxide (HP) mixed gel; Group 2 BG + HP mixed gel; and Group 3 HA + HP mixed gel. FT measurements with nano-indentation were carried out subsequent to bleaching experiments. Data were analyzed using SPSS and Kruskal–Wallis test (α = 0.05). Results: A significant difference in young's modulus (YM), VHN, and FT at baseline and subsequent to bleaching in control group was observed. However, no significant differences were found in YM, VHN, and FT between the test groups, compared to the respective baseline values. Conclusion: Under the limitations of the current study, it can be concluded that the n-HA, n-ACP, and n-BG could be potential biomaterials used to reduce the adverse effects of tooth bleaching. PMID:27307669

  14. Strain shielding from mechanically activated covalent bond formation during nanoindentation of graphene delays the onset of failure.

    PubMed

    Kumar, Sandeep; Parks, David M

    2015-03-11

    Mechanical failure of an ideal crystal is dictated either by an elastic instability or a soft-mode instability. Previous interpretations of nanoindentation experiments on suspended graphene sheets,1,2 however, indicate an anomaly: the inferred strain in the graphene sheet directly beneath the diamond indenter at the measured failure load is anomalously large compared to the fracture strains predicted by both soft-mode and acoustic analyses. Through multiscale modeling combining the results of continuum, atomistic, and quantum calculations, and analysis of experiments, we identify a strain-shielding effect initiated by mechanochemical interactions at the graphene-indenter interface as the operative mechanism responsible for this anomaly. Transmission electron micrographs and a molecular model of the diamond indenter's tip suggest that the tip surface contains facets comprising crystallographic {111} and {100} planes. Ab initio and molecular dynamics (MD) simulations confirm that a covalent bond (weld) formation between graphene and the crystallographic {111} and {100} facets on the indenter's surface can be induced by compressive contact stresses of the order achieved in nanoindentation tests. Finite element analysis (FEA) and MD simulations of nanoindentation reveal that the shear stiction provided by the induced covalent bonding restricts relative slip of the graphene sheet at its contact with the indenter, thus initiating a local strain-shielding effect. As a result, subsequent to stress-induced bonding at the graphene-indenter interface, the spatial variation of continuing incremental strain is substantially redistributed, locally shielding the region directly beneath the indenter by limiting the buildup of strain while imparting deformation to the surrounding regions. The extent of strain shielding is governed by the strength of the shear stiction, which depends upon the level of hydrogen saturation at the indenter's surface. We show that at intermediate levels

  15. AFM and electroanalytical studies of synthetic oligonucleotide hybridization.

    PubMed

    Chiorcea Paquim, A-M; Diculescu, V C; Oretskaya, T S; Oliveira Brett, A M

    2004-11-15

    The first and most important step in the development and manufacture of a sensitive DNA-biosensor for hybridization detection is the immobilization procedure of the nucleic acid probe on the transducer surface, maintaining its mobility and conformational flexibility. MAC Mode AFM images were used to demonstrate that oligonucleotide (ODN) molecules adsorb spontaneously at the electrode surface. After adsorption, the ODN layers were formed by molecules with restricted mobility, as well as by superposed molecules, which can lead to reduced hybridization efficiency. The images also showed the existence of pores in the adsorbed ODN film that revealed large parts of the electrode surface, and enabled non-specific adsorption of other ODNs on the uncovered areas. Electrostatic immobilization onto a clean glassy carbon electrode surface was followed by hybridization with complementary sequences and by control experiments with non-complementary sequences, studied using differential pulse voltammetry. The data obtained showed that non-specific adsorption strongly influenced the results, which depended on the sequence of the ODNs. In order to reduce the contribution of non-specific adsorbed ODNs during hybridization experiments, the carbon electrode surface was modified. After modification, the AFM images showed an electrode completely covered by the ODN probe film, which prevented the undesirable binding of target ODN molecules to the electrode surface. The changes of interfacial capacitance that took place after hybridization or control experiments showed the formation of a mixed multilayer that strongly depended on the local environment of the immobilized ODN.

  16. A hybrid approach to determining cornea mechanical properties in vivo using a combination of nano-indentation and inverse finite element analysis.

    PubMed

    Abyaneh, M H; Wildman, R D; Ashcroft, I A; Ruiz, P D

    2013-11-01

    An analysis of the material properties of porcine corneas has been performed. A simple stress relaxation test was performed to determine the viscoelastic properties and a rheological model was built based on the Generalized Maxwell (GM) approach. A validation experiment using nano-indentation showed that an isotropic GM model was insufficient for describing the corneal material behaviour when exposed to a complex stress state. A new technique was proposed for determining the properties, using a combination of nano-indentation experiment, an isotropic and orthotropic GM model and inverse finite element method. The good agreement using this method suggests that this is a promising technique for measuring material properties in vivo and further work should focus on the reliability of the approach in practice. PMID:23816808

  17. Mechanical properties of porcine femoral cortical bone measured by nanoindentation.

    PubMed

    Feng, Liang; Chittenden, Michael; Schirer, Jeffrey; Dickinson, Michelle; Jasiuk, Iwona

    2012-06-26

    This study uses a nanoindentation technique to examine variations in the local mechanical properties of porcine femoral cortical bone under hydrated conditions. Bone specimens from three age groups (6, 12 and 42 months), representing developing bone, ranging from young to mature animals, were tested on the longitudinal and transverse cross-sectional surfaces. Elastic modulus and hardness of individual lamellae within bone's microstructure: laminar bone, interstitial bone, and osteons, were measured. Both the elastic modulus and hardness increased with age. However, the magnitudes of these increases were different for each microstructural component. The longitudinal moduli were higher than the transverse moduli. Dehydrated samples were also tested to allow a comparison with hydrated samples and these resulted in higher moduli and hardness than the hydrated samples. Again, the degree of variation was different for each microstructural component. These results indicate that the developmental changes in bone have different rates of mechanical change within each microstructural component.

  18. Nanoindentation. Simulation of defect nucleation in a crystal.

    PubMed

    Gouldstone, A; Van Vliet, K J; Suresh, S

    2001-06-01

    Nanoindentation is the penetration of a surface to nanometre depths using an indenting device. It can be simulated using the Bragg bubble-raft model, in which a close-packed array of soap bubbles corresponds to the equilibrium positions of atoms in a crystalline solid. Here we show that homogeneous defect nucleation occurs within a crystal when its surface roughness is comparable to the radius of the indenter tip, and that the depth of the nucleation site below the surface is proportional to the half-width of the contact. Our results may explain the unusually high local stress required for defect nucleation in nano-indented face-centred cubic crystals. PMID:11395759

  19. Detection of Pathogens Using AFM and SPR

    NASA Astrophysics Data System (ADS)

    Vaseashta, Ashok

    2005-03-01

    A priori detection of pathogens in food and water has become a subject of paramount importance. Several recent incidents have resulted in the government passing stringent regulations for tolerable amounts of contamination of food products. Identification and/or monitoring of bacterial contamination in food are critical. The conventional methods of pathogen detection require time-consuming steps to arrive disembark at meaningful measurement in a timely manner as the detection time exceeds the time in which perishable food recycles through the food chain distribution. The aim of this presentation is to outline surface plasmon resonance (SPR) and atomic force microscopy (AFM) as two methods for fast detect6ion of pathogens. Theoretical basis of SPR and experimental results of SPR and AFM on E. coli O157:H7 and prion are presented.

  20. Strength by atomic force microscopy (AFM): Molecular dynamics of water layer squeezing on magnesium oxide

    NASA Astrophysics Data System (ADS)

    Kendall, K.; Dhir, Aman; Yong, Chin W.

    2010-11-01

    Localised strength testing of materials is often carried out in an atomic force microscope (AFM), as foreseen by Kelly in his book Strong Solids (Clarendon Press, Oxford, 1966). During AFM indentation experiments, contamination can strongly influence the observed strength and theoretical interpretation of the results is a major problem. Here, we use molecular dynamics computer modelling to describe the contact of NaCl and MgO crystal probes onto surfaces, comparable to an AFM experiment. Clean NaCl gave elastic, brittle behaviour in contact simulations at 300 K, whereas MgO was more plastic, leading to increased toughness. This paper also considers the strength of an oxide substrate contaminated by water molecules and tested by indentation with a pyramidal probe of oxide crystal. Recent theory on the effect of liquid contaminant layers on surface strength has been mainly focussed on Lennard Jones (LJ) molecules with some studies on alcohols and water, described by molecular dynamics, which allows the molecules to be squeezed out as the crystal lattice is deformed. In this work, we have focused on water by studying the forces between a magnesium oxide (MgO) atomic force microscope (AFM) probe and an MgO slab. Force versus separation has been plotted as the AFM probe was moved towards and away from the substrate. Simulation results showed that the water layers could be removed in steps, giving up to four force peaks. The last monolayer of water could not be squeezed out, even at pressures where MgO deformed plastically. Interestingly, with water present, strength was reduced, but more in tensile than compressive measurements. In conclusion, water contaminating the oxide surface in AFM strength testing is structured. Water layer squeezing removal can be predicted by molecular modelling, which may be verified by AFM experiments to show that water can influence the strength of perfect crystals at the nanometre scale.

  1. Nanotribological and nanomechanical properties of skin with and without cream treatment using atomic force microscopy and nanoindentation.

    PubMed

    Bhushan, Bharat

    2012-02-01

    Various beauty care products involve surface interaction between the product and the skin surface they are applied to. Friction, adhesion and wear during sliding between the treated surface and the rubbing surfaces need to be optimized. Skin cream is used to improve skin health and create a smooth, soft, and flexible surface with moist perception by altering the surface roughness, friction, adhesion, elastic modulus, and surface charge of the skin surface. Rheology of skin cream as a function of cream thickness and strain rate and the binding interaction between skin cream and skin surface and operating environment are some of the important factors affecting the smooth feel and repair of the skin surface. Atomic force microscopy (AFM) and nanoindentation have recently become important tools for studying the micro/nanoscale properties of human hair, hair conditioner, skin, and skin cream. In this paper, we present an overview of the nanotribological and nanomechanical properties of skin with and without cream treatment as a function of operating environment. Relevant mechanisms are discussed. Next, the result of a triboelectrification study of skin with and without cream treatment is presented. Finally, an overview of attempts to develop a synthetic skin for research purposes is presented. PMID:22104280

  2. Spherical nanoindentation stress-strain curves of commercially pure titanium and Ti-6Al-4V

    DOE Data Explorer

    Weaver, Jordan S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Priddy, Matthew W. [Georgia Inst. of Technology, Atlanta, GA (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); Kalidindi, Surya R. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2016-07-27

    Spherical nanoindentation combined with electron back-scattered diffraction was employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti for commercially pure (CP-Ti) and alloyed (Ti-64) titanium. In addition, alpha-beta Ti (single colony) grains were characterized. The data set includes the nanoindentation force, displacement, and contact stiffness, the nanoindentation stress-strain analysis, and the alpha-Ti crystal orientations. Details of the samples and experimental protocols can be found in Weaver et al. (2016) Acta Materialia doi:10.1016/j.actamat.2016.06.053.

  3. The effect of friction on indenter force and pile-up in numerical simulations of bone nanoindentation.

    PubMed

    Adam, C J; Swain, M V

    2011-10-01

    Nanoindentation is a useful technique for probing the mechanical properties of bone, and finite element (FE) modeling of the indentation allows inverse determination of elastoplastic constitutive properties. However, all but one FE study to date have assumed frictionless contact between indenter and bone. The aim of this study was to explore the effect of friction in simulations of bone nanoindentation. Two-dimensional axisymmetric FE simulations were performed using a spheroconical indenter of tip radius 0.6 μm and angle 90°. The coefficient of friction between indenter and bone was varied between 0.0 (frictionless) and 0.3. Isotropic linear elasticity was used in all simulations, with bone elastic modulus E = 13.56 GPa and Poisson's ratio of 0.3. Plasticity was incorporated using both Drucker-Prager and von Mises yield surfaces. Friction had a modest effect on the predicted force-indentation curve for both von Mises and Drucker-Prager plasticity, reducing maximum indenter displacement by 10% and 20% respectively as friction coefficient was increased from zero to 0.3 (at a maximum indenter force of 5 mN). However, friction has a much greater effect on predicted pile-up after indentation, reducing predicted pile-up from 0.27 to 0.11 μm with a von Mises model, and from 0.09 to 0.02 μm with Drucker-Prager plasticity. We conclude that it is potentially important to include friction in nanoindentation simulations of bone if pile-up is used to compare simulation results with experiment.

  4. A software tool for STED-AFM correlative super-resolution microscopy

    NASA Astrophysics Data System (ADS)

    Koho, Sami; Deguchi, Takahiro; Löhmus, Madis; Näreoja, Tuomas; Hänninen, Pekka E.

    2015-03-01

    Multi-modal correlative microscopy allows combining the strengths of several imaging techniques to provide unique contrast. However it is not always straightforward to setup instruments for such customized experiments, as most microscope manufacturers use their own proprietary software, with limited or no capability to interface with other instruments - this makes correlation of the multi-modal data extremely challenging. We introduce a new software tool for simultaneous use of a STimulated Emission Depletion (STED) microscope with an Atomic Force Microscope (AFM). In our experiments, a Leica TCS STED commercial super-resolution microscope, together with an Agilent 5500ilm AFM microscope was used. With our software, it is possible to synchronize the data acquisition between the STED and AFM instruments, as well as to perform automatic registration of the AFM images with the super-resolution STED images. The software was realized in LabVIEW; the registration part was also implemented as an ImageJ script. The synchronization was realized by controlling simple trigger signals, also available in the commercial STED microscope, with a low-cost National Instruments USB-6501 digital I/O card. The registration was based on detecting the positions of the AFM tip inside the STED fieldof-view, which were then used as registration landmarks. The registration should work on any STED and tip-scanning AFM microscope combination, at nanometer-scale precision. Our STED-AFM correlation method has been tested with a variety of nanoparticle and fixed cell samples. The software will be released under BSD open-source license.

  5. Custom AFM for X-ray beamlines: in situ biological investigations under physiological conditions.

    PubMed

    Gumí-Audenis, B; Carlà, F; Vitorino, M V; Panzarella, A; Porcar, L; Boilot, M; Guerber, S; Bernard, P; Rodrigues, M S; Sanz, F; Giannotti, M I; Costa, L

    2015-11-01

    A fast atomic force microscope (AFM) has been developed that can be installed as a sample holder for grazing-incidence X-ray experiments at solid/gas or solid/liquid interfaces. It allows a wide range of possible investigations, including soft and biological samples under physiological conditions (hydrated specimens). The structural information obtained using the X-rays is combined with the data gathered with the AFM (morphology and mechanical properties), providing a unique characterization of the specimen and its dynamics in situ during an experiment. In this work, lipid monolayers and bilayers in air or liquid environment have been investigated by means of AFM, both with imaging and force spectroscopy, and X-ray reflectivity. In addition, this combination allows the radiation damage induced by the beam on the sample to be studied, as has been observed on DOPC and DPPC supported lipid bilayers under physiological conditions. PMID:26524300

  6. Custom AFM for X-ray beamlines: in situ biological investigations under physiological conditions

    PubMed Central

    Gumí-Audenis, B.; Carlà, F.; Vitorino, M. V.; Panzarella, A.; Porcar, L.; Boilot, M.; Guerber, S.; Bernard, P.; Rodrigues, M. S.; Sanz, F.; Giannotti, M. I.; Costa, L.

    2015-01-01

    A fast atomic force microscope (AFM) has been developed that can be installed as a sample holder for grazing-incidence X-ray experiments at solid/gas or solid/liquid interfaces. It allows a wide range of possible investigations, including soft and biological samples under physiological conditions (hydrated specimens). The structural information obtained using the X-rays is combined with the data gathered with the AFM (morphology and mechanical properties), providing a unique characterization of the specimen and its dynamics in situ during an experiment. In this work, lipid monolayers and bilayers in air or liquid environment have been investigated by means of AFM, both with imaging and force spectroscopy, and X-ray reflectivity. In addition, this combination allows the radiation damage induced by the beam on the sample to be studied, as has been observed on DOPC and DPPC supported lipid bilayers under physiological conditions. PMID:26524300

  7. Temperature dependence of dislocation dynamics during nano-indentation in metals

    NASA Astrophysics Data System (ADS)

    Rathinam, Murugavel

    Temperature dictates mechanical properties of materials. In present day applications, materials are rarely utilized at room temperature alone. Meanwhile, temperatures may have drastic effects on the mechanical responses of materials, such as the deformation and fracture properties at different temperatures. Nanoscale testing of materials at non-ambient temperatures is now possible. The ability to perform nanotest measurements at elevated temperatures opens up significant new possibilities in nanotechnology. Sub-zero and high temperature analysis using nanoindentation technology is the first of its kind. Materials behave differently in real-life environments due to thermal loading. The objective of this thesis is to investigate the response of metals to nanoindentation at temperatures above and below the normal room temperature, using a combination of experiments and computer simulations. The metals studied include both face-center-cubic (FCC) and body-center-cubic (BCC) elements, and dislocation dynamics is the focus of this mechanics study. The experiments are performed with tailor-made Berkovitch tip of radius 100 nm at temperatures of 265 K, 388 K, 348 K, 473 K and 623 K. Single-crystals of tungsten, gold, Aluminum and polycrystalline copper are considered for the investigation. The indentation is done for BCC tungsten on the (111) and (110) crystallographic surfaces, FCC gold on the (111) and (110) crystallographic surfaces, single crystal aluminum with (100) crystallographic orientation and polycrystalline copper at different temperatures. Both the behaviour of material during loading and unloading are analyzed, and the processes are examined both experimentally and by computer simulations. Emphases are placed on the defects generation mechanisms during the elastic plastic contact of crystals. Special attention has been devoted to the elastic response before the onset of plastic yield. The temperature dependency experiments and computer simulations yield very

  8. Mapping strain fields induced in Zr-based bulk metallic glasses during in-situ nanoindentation by X-ray nanodiffraction

    NASA Astrophysics Data System (ADS)

    Gamcová, J.; Mohanty, G.; Michalik, Š.; Wehrs, J.; Bednarčík, J.; Krywka, C.; Breguet, J. M.; Michler, J.; Franz, H.

    2016-01-01

    A pioneer in-situ synchrotron X-ray nanodiffraction approach for characterization and visualization of strain fields induced by nanoindentation in amorphous materials is introduced. In-situ nanoindentation experiments were performed in transmission mode using a monochromatic and highly focused sub-micron X-ray beam on 40 μm thick Zr-based bulk metallic glass under two loading conditions. Spatially resolved X-ray diffraction scans in the deformed volume of Zr-based bulk metallic glass covering an area of 40 × 40 μm2 beneath the pyramidal indenter revealed two-dimensional map of elastic strains. The largest value of compressive elastic strain calculated from diffraction data at 1 N load was -0.65%. The region of high elastic compressive strains (<-0.3%) is located beneath the indenter tip and has radius of 7 μm.

  9. SU-8 hollow cantilevers for AFM cell adhesion studies

    NASA Astrophysics Data System (ADS)

    Martinez, Vincent; Behr, Pascal; Drechsler, Ute; Polesel-Maris, Jérôme; Potthoff, Eva; Vörös, Janos; Zambelli, Tomaso

    2016-05-01

    A novel fabrication method was established to produce flexible, transparent, and robust tipless hollow atomic force microscopy (AFM) cantilevers made entirely from SU-8. Channels of 3 μm thickness and several millimeters length were integrated into 12 μm thick and 40 μm wide cantilevers. Connected to a pressure controller, the devices showed high sealing performance with no leakage up to 6 bars. Changing the cantilever lengths from 100 μm to 500 μm among the same wafer allowed the targeting of various spring constants ranging from 0.5 to 80 N m-1 within a single fabrication run. These hollow polymeric AFM cantilevers were operated in the optical beam deflection configuration. To demonstrate the performance of the device, single-cell force spectroscopy experiments were performed with a single probe detaching in a serial protocol more than 100 Saccharomyces cerevisiae yeast cells from plain glass and glass coated with polydopamine while measuring adhesion forces in the sub-nanoNewton range. SU-8 now offers a new alternative to conventional silicon-based hollow cantilevers with more flexibility in terms of complex geometric design and surface chemistry modification.

  10. SU-8 hollow cantilevers for AFM cell adhesion studies

    NASA Astrophysics Data System (ADS)

    Martinez, Vincent; Behr, Pascal; Drechsler, Ute; Polesel-Maris, Jérôme; Potthoff, Eva; Vörös, Janos; Zambelli, Tomaso

    2016-05-01

    A novel fabrication method was established to produce flexible, transparent, and robust tipless hollow atomic force microscopy (AFM) cantilevers made entirely from SU-8. Channels of 3 μm thickness and several millimeters length were integrated into 12 μm thick and 40 μm wide cantilevers. Connected to a pressure controller, the devices showed high sealing performance with no leakage up to 6 bars. Changing the cantilever lengths from 100 μm to 500 μm among the same wafer allowed the targeting of various spring constants ranging from 0.5 to 80 N m‑1 within a single fabrication run. These hollow polymeric AFM cantilevers were operated in the optical beam deflection configuration. To demonstrate the performance of the device, single-cell force spectroscopy experiments were performed with a single probe detaching in a serial protocol more than 100 Saccharomyces cerevisiae yeast cells from plain glass and glass coated with polydopamine while measuring adhesion forces in the sub-nanoNewton range. SU-8 now offers a new alternative to conventional silicon-based hollow cantilevers with more flexibility in terms of complex geometric design and surface chemistry modification.

  11. BOREAS AFM-6 Surface Meteorological Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Adminsitration/Environment Technology Laboratory (NOAA/ETL) collected surface meteorological data from 21 May to 20 Sep 1994 near the Southern Study Area-Old Jack Pine (SSA-OJP) tower site. The data are in tabular ASCII files. The surface meteorological data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  12. A rapid and automated relocation method of an AFM probe for high-resolution imaging

    NASA Astrophysics Data System (ADS)

    Zhou, Peilin; Yu, Haibo; Shi, Jialin; Jiao, Niandong; Wang, Zhidong; Wang, Yuechao; Liu, Lianqing

    2016-09-01

    The atomic force microscope (AFM) is one of the most powerful tools for high-resolution imaging and high-precision positioning for nanomanipulation. The selection of the scanning area of the AFM depends on the use of the optical microscope. However, the resolution of an optical microscope is generally no larger than 200 nm owing to wavelength limitations of visible light. Taking into consideration the two determinants of relocation—relative angular rotation and positional offset between the AFM probe and nano target—it is therefore extremely challenging to precisely relocate the AFM probe to the initial scan/manipulation area for the same nano target after the AFM probe has been replaced, or after the sample has been moved. In this paper, we investigate a rapid automated relocation method for the nano target of an AFM using a coordinate transformation. The relocation process is both simple and rapid; moreover, multiple nano targets can be relocated by only identifying a pair of reference points. It possesses a centimeter-scale location range and nano-scale precision. The main advantages of this method are that it overcomes the limitations associated with the resolution of optical microscopes, and that it is label-free on the target areas, which means that it does not require the use of special artificial markers on the target sample areas. Relocation experiments using nanospheres, DNA, SWCNTs, and nano patterns amply demonstrate the practicality and efficiency of the proposed method, which provides technical support for mass nanomanipulation and detection based on AFM for multiple nano targets that are widely distributed in a large area.

  13. A rapid and automated relocation method of an AFM probe for high-resolution imaging.

    PubMed

    Zhou, Peilin; Yu, Haibo; Shi, Jialin; Jiao, Niandong; Wang, Zhidong; Wang, Yuechao; Liu, Lianqing

    2016-09-30

    The atomic force microscope (AFM) is one of the most powerful tools for high-resolution imaging and high-precision positioning for nanomanipulation. The selection of the scanning area of the AFM depends on the use of the optical microscope. However, the resolution of an optical microscope is generally no larger than 200 nm owing to wavelength limitations of visible light. Taking into consideration the two determinants of relocation-relative angular rotation and positional offset between the AFM probe and nano target-it is therefore extremely challenging to precisely relocate the AFM probe to the initial scan/manipulation area for the same nano target after the AFM probe has been replaced, or after the sample has been moved. In this paper, we investigate a rapid automated relocation method for the nano target of an AFM using a coordinate transformation. The relocation process is both simple and rapid; moreover, multiple nano targets can be relocated by only identifying a pair of reference points. It possesses a centimeter-scale location range and nano-scale precision. The main advantages of this method are that it overcomes the limitations associated with the resolution of optical microscopes, and that it is label-free on the target areas, which means that it does not require the use of special artificial markers on the target sample areas. Relocation experiments using nanospheres, DNA, SWCNTs, and nano patterns amply demonstrate the practicality and efficiency of the proposed method, which provides technical support for mass nanomanipulation and detection based on AFM for multiple nano targets that are widely distributed in a large area. PMID:27559679

  14. In situ characterization of formation and growth of high-pressure phases in single-crystal silicon during nanoindentation

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Yan, Jiwang

    2016-04-01

    Pressure-induced intermediate phases of silicon exhibit unique characteristics in mechanics, chemistry, optics, and electrics. Clarifying the formation and growth processes of these new phases is essential for the preparation and application of them. For in situ characterization of the formation and growth of high-pressure phases in single-crystal silicon, a quantitative parameter, namely displacement change of indenter (Δ h) during the unloading holding process in nanoindentation, was proposed. Nanoindentation experiments under various unloading holding loads and loading/unloading rates were performed to investigate their effects on Δ h. Results indicate that Δ h varies significantly before and after the occurrence of pop-out; for the same maximum indentation load, it tends to increase with the decrease in the holding load and to increase with the increase in the loading/unloading rate. Thus, the value of Δ h can be regarded as an indicator that reflects the formation and growth processes of the high-pressure phases. Using Δ h, the initial position for the nucleation of the high-pressure phases, their growth, and their correlation to the loading/unloading rate were predictable.

  15. AFM as an alternative for Young’s modulus determination in ceramic materials in elastic deformation regime

    NASA Astrophysics Data System (ADS)

    Roa, J. J.; Oncins, G.; Dias, F. T.; Vieira, V. N.; Schaf, J.; Segarra, M.

    2011-09-01

    A novel alternative to the conventional nanoindentation technique for hard materials is presented. An atomic force microscopy probe is used as an indenter, applying loads in the nN range and producing elastic deformations of a few nanometres. This new technique allows a reduction of the different inherent nanoindenter problems. This result in an increase in the quality of the overall results, and thus provide better understanding of the contact mechanism between the indenter and the sample, yielding Young’s modulus values consistent with the literature. This is confirmed by a series of experiments performed on different YBa 2Cu 3O 7-x textured and single crystal samples textured using different techniques.

  16. Reducing the nucleation barrier in magnetocaloric Heusler alloys by nanoindentation

    NASA Astrophysics Data System (ADS)

    Niemann, R.; Hahn, S.; Diestel, A.; Backen, A.; Schultz, L.; Nielsch, K.; Wagner, M. F.-X.; Fähler, S.

    2016-06-01

    Magnetocaloric materials are promising as solid state refrigerants for more efficient and environmentally friendly cooling devices. The highest effects have been observed in materials that exhibit a first-order phase transition. These transformations proceed by nucleation and growth which lead to a hysteresis. Such irreversible processes are undesired since they heat up the material and reduce the efficiency of any cooling application. In this article, we demonstrate an approach to decrease the hysteresis by locally changing the nucleation barrier. We created artificial nucleation sites and analyzed the nucleation and growth processes in their proximity. We use Ni-Mn-Ga, a shape memory alloy that exhibits a martensitic transformation. Epitaxial films serve as a model system, but their high surface-to-volume ratio also allows for a fast heat transfer which is beneficial for a magnetocaloric regenerator geometry. Nanoindentation is used to create a well-defined defect. We quantify the austenite phase fraction in its proximity as a function of temperature which allows us to determine the influence of the defect on the transformation.

  17. Mechanical properties of hyaline and repair cartilage studied by nanoindentation.

    PubMed

    Franke, O; Durst, K; Maier, V; Göken, M; Birkholz, T; Schneider, H; Hennig, F; Gelse, K

    2007-11-01

    Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies. PMID:17586107

  18. Cells mechanics with AFM: problems and solutions

    NASA Astrophysics Data System (ADS)

    Sokolov, Igor; Dokukin, Maxim; Guz, Nataliia

    2012-02-01

    Atomic force microscopy (AFM) is used to study mechanics of cells. Cell is far from being a homogeneous medium. This creates a number of problems which will be discussed as well as the ways to solve them. We will focus on the following problems: 1. Cellular surface brush (microvilli, glycocalyx..) surrounds cells. A simple model to separate the brush and cell deformation will be overviewed. 2. Problem of nonlinearity of stress-strain relation. Although unsolved, this may indirectly tested: the rigidity modulus should be reasonably independent of penetration. We will show that it can be achieved when using relatively dull AFM probes (the radii of microns) only. 3. Heterogeneity of cell surface. Cells are not homogeneous over the surface. We will discuss the question how many points is enough to characterize the cell. We will exemplify the above with human cervical epithelial cells. We will demonstrate that without proper consideration of the above problems, the error in defining the modulus of rigidity can easily reach an order of magnitude.

  19. AFM Bio-Mechanical Investigation of the Taxol Treatment of Breast Cancer Cells

    NASA Astrophysics Data System (ADS)

    Smith, Dylan; Patel, Dipika; Monjaraz, Fernando; Park, Soyeun

    2009-10-01

    Cancerous cells are known to be softer and easier to deform than normal cells. Changes in mechanical properties originate from the alteration of the actin cytoskeleton. The mechanism of cancer treatment using Taxol is related to the stabilization of microtubules. It has been shown that Taxol binds to polymerized tublin, stabilizes it against disassembly, and consequently inhibits cell division. An accurate quantitative study still lacks to relate the microtubule stabilizing effect with the cellular mechanical properties. We utilized our AFM to study changes in elastic properties of treated breast cancer cells. The AFM has several advantages for precise force measurements on a localized region with nanometer lateral dimension. In previous AFM studies, measurable contributions from the underlying hard substrate have been an obstacle to accurately determine the properties on thin samples. We modified our AFM tip to obtain the exact deformation profile as well as reducing the high stresses produced. We have probed depth profiles of mechanical properties of the taxol-treated and untreated cells by varying the indentation depth of the AFM-nanoindenting experiments.

  20. [AFM fishing of proteins under impulse electric field].

    PubMed

    Ivanov, Yu D; Pleshakova, T O; Malsagova, K A; Kaysheva, A L; Kopylov, A T; Izotov, A A; Tatur, V Yu; Vesnin, S G; Ivanova, N D; Ziborov, V S; Archakov, A I

    2016-05-01

    A combination of (atomic force microscopy)-based fishing (AFM-fishing) and mass spectrometry allows to capture protein molecules from solutions, concentrate and visualize them on an atomically flat surface of the AFM chip and identify by subsequent mass spectrometric analysis. In order to increase the AFM-fishing efficiency we have applied pulsed voltage with the rise time of the front of about 1 ns to the AFM chip. The AFM-chip was made using a conductive material, highly oriented pyrolytic graphite (HOPG). The increased efficiency of AFM-fishing has been demonstrated using detection of cytochrome b5 protein. Selection of the stimulating pulse with a rise time of 1 ns, corresponding to the GHz frequency range, by the effect of intrinsic emission from water observed in this frequency range during water injection into the cell. PMID:27562998

  1. [AFM fishing of proteins under impulse electric field].

    PubMed

    Ivanov, Yu D; Pleshakova, T O; Malsagova, K A; Kaysheva, A L; Kopylov, A T; Izotov, A A; Tatur, V Yu; Vesnin, S G; Ivanova, N D; Ziborov, V S; Archakov, A I

    2016-05-01

    A combination of (atomic force microscopy)-based fishing (AFM-fishing) and mass spectrometry allows to capture protein molecules from solutions, concentrate and visualize them on an atomically flat surface of the AFM chip and identify by subsequent mass spectrometric analysis. In order to increase the AFM-fishing efficiency we have applied pulsed voltage with the rise time of the front of about 1 ns to the AFM chip. The AFM-chip was made using a conductive material, highly oriented pyrolytic graphite (HOPG). The increased efficiency of AFM-fishing has been demonstrated using detection of cytochrome b5 protein. Selection of the stimulating pulse with a rise time of 1 ns, corresponding to the GHz frequency range, by the effect of intrinsic emission from water observed in this frequency range during water injection into the cell.

  2. Mechanical properties study of SW480 cells based on AFM.

    PubMed

    Liu, Xiaogang; Song, Zhengxun; Qu, Yingmin; Wang, Guoliang; Wang, Zuobin

    2015-08-01

    Since the invention of the atomic force microscope (AFM), it has been widely applied in biomedicine. One of the most important applications is used as an indenter tool to do the indentation experiment in order to get the mechanical properties of cells. In this paper, SW480 cells were used as the test subjects. Through the analysis of the contact and indentation, Young's modulus (E), which is an important parameter of cancer cells, has been estimated. Experimental results show that different mechanical models should be chosen to calculate the E in different indentation depths. Here, the E of SW480 cells was (2.5 ± 0.8) KPa at the indentation depth of 99 nm.

  3. Mechanical Characterization of Photo-crosslinkable Hydrogels with AFM

    NASA Astrophysics Data System (ADS)

    McKenna, Alyssa; Byun, Myunghwan; Hayward, Ryan; Aidala, Katherine

    2012-02-01

    Stimuli-responsive hydrogel films formed from photo-crosslinkable polymers are versatile materials for controlled drug delivery devices, three-dimensional micro-assemblies, and components in microfluidic systems. For such applications, it is important to understand both the mechanical properties and the dynamics responses of these materials. We describe the use of atomic force microscope (AFM) based indentation experiments to characterize the properties of poly(N-isopropylacrylamide) copolymer films, crosslinked by activation of pendent benzophenone units using ultraviolet light. In particular, we study how the elastic modulus of the material, determined using the Johnson, Kendall, and Roberts model, depends on UV dose, and simultaneously investigate stress relaxation in these materials in the context of viscoelastic and poroelastic relaxation models.

  4. Delamination analysis of metal-ceramic multilayer coatings subject to nanoindentation

    DOE PAGES

    Jamison, Ryan Dale; Shen, Yu -Lin

    2016-01-22

    Internal damage has been experimentally observed in aluminum (Al)/silicon carbide (SiC) multilayer coatings subject to nanoindentation loading. Post-indentation characterization has identified that delamination at the coating/substrate interface is the most prominent form of damage. In this study the finite element method is employed to study the effect of delamination on indentation-derived hardness and Young's modulus. The model features alternating Al/SiC nanolayers above a silicon (Si) substrate, in consistence with the actual material system used in earlier experiments. Cohesive elements with a traction–separation relationship are used to facilitate delamination along the coating/substrate interface. Delamination is observed numerically to be sensitive tomore » the critical normal and shear stresses that define the cohesive traction–separation behavior. Axial tensile stress below the edge of indentation contact is found to be the largest contributor to damage initiation and evolution. Delamination results in a decrease in both indentation-derived hardness and Young's modulus. As a result, a unique finding is that delamination can occur during the unloading process of indentation, depending on the loading condition and critical tractions.« less

  5. Single versus successive pop-in modes in nanoindentation tests of single crystals

    DOE PAGES

    Xia, Yuzhi; Gao, Yanfei; Pharr, George M.; Bei, Hongbin

    2016-05-24

    From recent nanoindentation experiments, two types of pop-in modes have been identified: a single pop-in with a large displacement excursion, or a number of pop-ins with comparable and small displacement excursions. Theoretical analyses are developed here to study the roles played by indenter tip radius, pre-existing defect density, heterogeneous nucleation source type, and lattice resistance on the pop-in modes. The evolution of dislocation structures in earlier pop-ins provides input to modeling a stochastic, heterogeneous mechanism that may be responsible for the subsequent pop-ins. It is found that when the first pop-in occurs near theoretical shear stress, the pop-in mode ismore » determined by the lattice resistance and tip radius. When the first pop-in occurs at low shear stress, whether the successive pop-in mode occurs depends on how the heterogeneous dislocation nucleation source density increases as compared to the increase of the total dislocation density. Lastly, the above transitions are found to correlate well with the ratio of indenter tip radius to the mean spacing of dislocation nucleation sources.« less

  6. BOREAS AFM-6 Boundary Layer Height Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from National Oceanic and Atmospheric Adminsitration/Environment Technology Laboratory (NOAA/ETL) operated a 915-MHz wind/Radio Acoustic Sounding System (RASS) profiler system in the Southern Study Area (SSA) near the Old Jack Pine (OJP) site. This data set provides boundary layer height information over the site. The data were collected from 21 May 1994 to 20 Sep 1994 and are stored in tabular ASCII files. The boundary layer height data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  7. BOREAS AFM-06 Mean Wind Profile Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Administration/Environment Technology Laboratory (NOAA/ETL) operated a 915-MHz wind/Radio Acoustic Sounding System (RASS) profiler system in the Southern Study Area (SSA) near the Old Jack Pine (OJP) tower from 21 May 1994 to 20 Sep 1994. The data set provides wind profiles at 38 heights, containing the variables of wind speed; wind direction; and the u-, v-, and w-components of the total wind. The data are stored in tabular ASCII files. The mean wind profile data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  8. BOREAS AFM-06 Mean Temperature Profile Data

    NASA Technical Reports Server (NTRS)

    Wilczak, James; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Adminsitration/Environment Technology Laboratory (NOAA/ETL) operated a 915-MHz wind/Radio Acoustic Sounding System (RASS) profiler system in the Southern Study Area (SSA) near the Old Jack Pine (OJP) tower from 21 May 1994 to 20 Sep 1994. The data set provides temperature profiles at 15 heights, containing the variables of virtual temperature, vertical velocity, the speed of sound, and w-bar. The data are stored in tabular ASCII files. The mean temperature profile data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  9. Afm Measrurements of Martian Soil Particles Using Mems Technology - Results from the PHOENIX Mission

    NASA Astrophysics Data System (ADS)

    Gautsch, S.; Parrat, D.; de Rooij, N. F.; Staufer, U.; Morookian, J. M.; Hecht, M. H.; Vijendran, S.; Sykulska, H.; Pike, W. T.

    2011-12-01

    Light scattering experiments conducted on Mars indicated that soil particles have dimensions around 1 μm. Particles in that range play an important role in the gas exchange between sub-surface water ice and the atmosphere. Their shape can help tracing the geological history and may indicate past presence of liquid water. NASA's Phoenix mission therefore decided to analyze soil and dust particles in the sub-micrometer to a few micrometer range using an atomic force microscope (AFM) for the first time on another planet. The co-axially mounted AFM was capable of resolving particles with 10nm lateral resolution. A MEMS approach combined with mechatronic concepts for the scanner was selected for implementing the AFM. For redundancy, the sensor chip featured eight silicon cantilevers each with a 7 to 8 μm high tip. The cantilevers could be cleaved off if contaminated. During NASA's Phoenix Mission, which operated on the red planet from May to October 2008, we could demonstrate successful AFM operations. The instrument has executed 85 experiments of which 26 were needed for calibration. Of the remaining experiments about half (28) returned images where signatures of particles could be discerned.

  10. Comparison of mechanical testing methods for biomaterials: Pipette aspiration, nanoindentation, and macroscale testing.

    PubMed

    Buffinton, Christine Miller; Tong, Kelly J; Blaho, Roberta A; Buffinton, Elise M; Ebenstein, Donna M

    2015-11-01

    Characterization of the mechanical properties of biological materials is often complicated by small volume, irregular geometry, fragility, and environmental sensitivity. Pipette aspiration and nanoindentation testing deal well with these limitations and have seen increasing use in biomaterial characterization, but little research has been done to systematically validate these techniques for soft materials. This study compared the results of pipette aspiration, nanoindentation, and bulk uniaxial tension and compression in determining the small-strain elastic moduli of a range of biomedically-relevant materials, a series of silicone elastomers and polyacrylamide hydrogels. A custom apparatus was developed for pipette aspiration testing, a commercial Hysitron instrument with custom spherical tip was used for nanoindentation, and standard commercial machines were used for tension and compression testing. The measured small-strain elastic moduli ranged from 27 to 368 kPa for the silicones and 11 to 44 kPa for the polyacrylamide gels. All methods detected expected trends in material stiffness, except for the results from one inconsistent silicone. Pipette aspiration and nanoindentation measured similar elastic moduli for silicone materials, but pipette aspiration measured consistently larger stiffness in the hydrogels, which may be explained by the gels' resistance to tension. Despite the difference in size scale among the testing methods, size does not appear to influence the results. These results suggest that both pipette aspiration and nanoindentation are suitable for measuring mechanical properties of soft biomaterials and appear to have no more limitations than bulk techniques. PMID:26295450

  11. Comparison of mechanical testing methods for biomaterials: Pipette aspiration, nanoindentation, and macroscale testing.

    PubMed

    Buffinton, Christine Miller; Tong, Kelly J; Blaho, Roberta A; Buffinton, Elise M; Ebenstein, Donna M

    2015-11-01

    Characterization of the mechanical properties of biological materials is often complicated by small volume, irregular geometry, fragility, and environmental sensitivity. Pipette aspiration and nanoindentation testing deal well with these limitations and have seen increasing use in biomaterial characterization, but little research has been done to systematically validate these techniques for soft materials. This study compared the results of pipette aspiration, nanoindentation, and bulk uniaxial tension and compression in determining the small-strain elastic moduli of a range of biomedically-relevant materials, a series of silicone elastomers and polyacrylamide hydrogels. A custom apparatus was developed for pipette aspiration testing, a commercial Hysitron instrument with custom spherical tip was used for nanoindentation, and standard commercial machines were used for tension and compression testing. The measured small-strain elastic moduli ranged from 27 to 368 kPa for the silicones and 11 to 44 kPa for the polyacrylamide gels. All methods detected expected trends in material stiffness, except for the results from one inconsistent silicone. Pipette aspiration and nanoindentation measured similar elastic moduli for silicone materials, but pipette aspiration measured consistently larger stiffness in the hydrogels, which may be explained by the gels' resistance to tension. Despite the difference in size scale among the testing methods, size does not appear to influence the results. These results suggest that both pipette aspiration and nanoindentation are suitable for measuring mechanical properties of soft biomaterials and appear to have no more limitations than bulk techniques.

  12. Strength and Mechanical Response of NaCl Using In-Situ Transmission Electron Microscopy Compression and Nanoindentation.

    PubMed

    Lin, Kai-Peng; Fang, Te-Hua; Kang, Sho-Hui

    2016-03-01

    Strength and mechanical properties of single crystal sodium chloride (NaCl) are characterized. Critical deformation variations of NaCl pillared structures and films are estimated using in-situ transmission electron microscope (TEM) compression tests and nanoindentation experiments. Young's modulus and contact stiffness of NaCl pillars with diameters of 300 to 500 nm were 10.4-23.9 GPa, and 159-230 N/m, respectively. The nanohardness and Vickers hardness of the NaCl (001) film were 282-596 and 196-260 MPa, respectively. The results could provide useful information for understanding the mechanical properties, contact and local deformation of NaCl pillars and films. PMID:27455676

  13. Nanoindentation-induced phase transformation and structural deformation of monocrystalline germanium: a molecular dynamics simulation investigation

    PubMed Central

    2013-01-01

    Molecular dynamics simulations were conducted to study the nanoindentation of monocrystalline germanium. The path of phase transformation and distribution of transformed region on different crystallographic orientations were investigated. The results indicate the anisotropic behavior of monocrystalline germanium. The nanoindentation-induced phase transformation from diamond cubic structure to β-tin-Ge was found in the subsurface region beneath the tool when indented on the (010) plane, while direct amorphization was observed in the region right under the indenter when the germanium was loaded along the [101] and [111] directions. The transformed phases extend along the < 110 > slip direction of germanium. The depth and shape of the deformed layers after unloading are quite different according to the crystal orientation of the indentation plane. The study results suggest that phase transformation is the dominant mechanism of deformation of monocrystalline germanium film in nanoindentation. PMID:23947487

  14. Characterization of ion beam irradiated 304 stainless steel utilizing nanoindentation and Laue microdiffraction

    NASA Astrophysics Data System (ADS)

    Lupinacci, A.; Chen, K.; Li, Y.; Kunz, M.; Jiao, Z.; Was, G. S.; Abad, M. D.; Minor, A. M.; Hosemann, P.

    2015-03-01

    Characterizing irradiation damage in materials utilized in light water reactors is critical for both material development and application reliability. Here we use both nanoindentation and Laue microdiffraction to characterize both the mechanical response and microstructure evolution due to irradiation. Two different irradiation conditions were considered in 304 stainless steel: 1 dpa and 10 dpa. In addition, an annealed condition of the 10 dpa specimen for 1 h at 500 °C was evaluated. Nanoindentation revealed an increase in hardness due to irradiation and also revealed that hardness saturated in the 10 dpa case. Broadening using Laue microdiffraction peaks indicates a significant plastic deformation in the irradiated area that is in good agreement with both the SRIM calculations and the nanoindentation results.

  15. Structural and Mechanical Mechanisms of Ocular Tissues Probed by AFM

    NASA Astrophysics Data System (ADS)

    Ziebarth, Noël M.; Rico, Felix; Moy, Vincent T.

    In recent years, the atomic force microscope (AFM) has become an important tool in ophthalmic research. It has gained popularity largely because AFM is not restricted by the diffraction limits of light microscopy and can be applied to resolve images with molecular resolution. AFM is a minimally invasive technique and can be used to visualize molecular structures under near-physiological conditions. In addition, the AFM can be employed as a force apparatus to characterize the viscoelastic properties of biomaterials on the micron level and at the level of individual proteins. In this article, we summarize recent AFM studies of ocular tissues, while highlighting the great potential of AFM technology in ophthalmic research. Previous research demonstrates the versatility of the AFM as high resolution imaging technique and as a sensitive force apparatus for probing the mechanical properties of ocular tissues. The structural and mechanical properties of ocular tissues are of major importance to the understanding of the optomechanical functions of the human eye. In addition, AFM has played an important role in the development and characterization of ocular biomaterials, such as contact lenses and intraocular lenses. Studying ocular tissues using Atomic Force Microscopy has enabled several advances in ophthalmic research.

  16. Microrheology using a custom-made AFM

    NASA Astrophysics Data System (ADS)

    Kosgodagan Acharige, Sebastien; Benzaquen, Michael; Steinberger, Audrey

    In the past few years, a new method was developed to measure local properties of liquids (X. Xiong et al., Phys. Rev. E 80, 2009). This method consists of gluing a micron-sized glass fiber at the tip of an AFM cantilever and probing the liquid with it. In ENS Lyon, this method was perfected (C. Devailly et al., EPL, 106 5, 2014) with the help of an interferometer developped in the same laboratory (L. Bellon et al., Opt. Commun. 207 49, 2002 and P. Paolino et al., Rev. Sci. Instrum. 84, 2013), which background noise can reach 10-14 m /√{ Hz } . This method allows us to measure a wide range of viscosities (1 mPa . s to 500 mPa . s) of transparent and opaque fluids using a small sample volume ( 5 mL). In this presentation, I will briefly describe the interferometer developped in ENS Lyon, then explain precisely the microrheology measurements and then compare the experimental results to a model developped by M. Benzaquen. This work is supported financially by the ANR project NANOFLUIDYN (Grant Number ANR-13-BS10-0009).

  17. BOREAS AFM-07 SRC Surface Meteorological Data

    NASA Technical Reports Server (NTRS)

    Osborne, Heather; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Young, Kim; Wittrock, Virginia; Shewchuck, Stan; Smith, David E. (Technical Monitor)

    2000-01-01

    The Saskatchewan Research Council (SRC) collected surface meteorological and radiation data from December 1993 until December 1996. The data set comprises Suite A (meteorological and energy balance measurements) and Suite B (diffuse solar and longwave measurements) components. Suite A measurements were taken at each of ten sites, and Suite B measurements were made at five of the Suite A sites. The data cover an approximate area of 500 km (North-South) by 1000 km (East-West) (a large portion of northern Manitoba and northern Saskatchewan). The measurement network was designed to provide researchers with a sufficient record of near-surface meteorological and radiation measurements. The data are provided in tabular ASCII files, and were collected by Aircraft Flux and Meteorology (AFM)-7. The surface meteorological and radiation data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  18. Atomic-scale microstructure underneath nanoindentation in Al-Cr-N ceramic films

    SciTech Connect

    Zhuang, Chunqiang Li, Zhipeng; Lin, Songsheng

    2015-12-15

    In this work, Al-Cr-N ceramic films deformed by nanoindentation were peeled off from silicon substrates and their atomic-scale microstructures underneath the indenter were investigated by high resolution transmission electron microscope (HR-TEM). Dislocations were formed underneath the indenter and they accumulated along nano-grain boundaries. The accumulative dislocations triggered the crack initiation along grain boundaries, and further resulted in the crack propagation. Dislocations were also observed in nano-grains on the lateral contact area. A model was proposed to describe the variation of microstructures under nanoindentation.

  19. Cleaning of diamond nanoindentation probes with oxygen plasma and carbon dioxide snow

    SciTech Connect

    Morris, Dylan J.

    2009-12-15

    Diamond nanoindentation probes may perform thousands of indentations over years of service life. There is a broad agreement that the probes need frequent cleaning, but techniques for doing so are mostly anecdotes shared between experimentalists. In preparation for the measurement of the shape of a nanoindentation probe by a scanning probe microscope, cleaning by carbon dioxide snow jets and oxygen plasma was investigated. Repeated indentation on a thumbprint-contaminated surface formed a compound that was very resistant to removal by solvents, CO{sub 2} snow, and plasma. CO{sub 2} snow cleaning is found to be a generally effective cleaning procedure.

  20. Measuring Polydimethylsiloxane (PDMS) Mechanical Properties Using Flat Punch Nanoindentation Focusing on Obtaining Full Contact

    NASA Astrophysics Data System (ADS)

    De Paoli, Federico

    In this research, the materials used were the Polydimethylsiloxane (PDMS) polymers. PDMS mechanicals properties were measured using a customized version of the nanoindentation test using a flat punch tip. The method is proposed in Chapter 3 and it is used to calculate the elastic modulus of different PDMS samples. The samples tested were both produced specifically for this research and available in the laboratory's storage. They all present different levels of cross-linking degree. It is quite common to not have full contact between the cylindrical flat punch and the sample because of the unavoidable tilt. The new method guarantees establishing full contact between the sample and the tip. The tip used for this purpose is a flat punch tip. The Young's moduli of the following samples were calculated: 10:1, 30:1 and 50:1. The Young's moduli found were: 2.85+/-0.001 MPa for the 10:1 sample, 0.34+/-0.001 MPa for the 30:1 sample and 0.15+/-0.002 MPa for the 50:1 sample. All the experiments were repeated at least three times to assure the validity and the repeatability of the method. The results were then compared with values available in the literature. The same method was applied to analyze the viscosity of the samples. Even if a mathematical result was not obtained, data and analysis through graphical representations are available in this thesis. The sample tested was a PDMS sample with a cross-linking degree of 30:1. The experiment has been repeated three times.

  1. Difference in cellular mechanics of cancer and normal cervical cells as seen with the AFM

    NASA Astrophysics Data System (ADS)

    Sokolov, Igor; Iyer, Swaminathan; Subba-Rao, Venkatesh; Woodworth, Craig

    2006-03-01

    Oncogenically transformed cells differ from their normal counter parts in many aspects, including organization and the amount of cytoskeleton. Consequently it is natural to expect to see the difference in cellular mechanics. Here we will present the study of such differences by using atomic force microscopy (AFM) in-vitro. So far the present research is the first study of mechanics of cervical cells, and the third comparative study of differences between mechanics of cancer and normal cells down with the help of AFM. Using a micron size silica ball as the AFM probe, we presumably do not overstress the cell surface as it can be in the case of the sharp AFM tip, and consequently, we may use the classical Hertz model. In contrast to the reported previously studies (bladder and fibroblast cells), we found that oncogenically transformed cervical cells are more rigid than the normal cells. The reason for such difference will be discussed. To demonstrate the complexity of the problem, we study cell mechanics in detail. The Young's modulus of rigidity clearly shows two separate regions of rigidity depending on the depth of the probe penetration. There may be two alternative explanations of the difference in rigidity of this top layer: it is either the cell membrane layer or detected long-range (presumably steric) forces due to the molecular ``brush'' of glycocalyx molecules. Experiments and modal calculations will be presented to choose between these two possibilities.

  2. Raman and AFM study of gamma irradiated plastic bottle sheets

    NASA Astrophysics Data System (ADS)

    Ali, Yasir; Kumar, Vijay; Sonkawade, R. G.; Dhaliwal, A. S.

    2013-02-01

    In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV 60Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

  3. Raman and AFM study of gamma irradiated plastic bottle sheets

    SciTech Connect

    Ali, Yasir; Kumar, Vijay; Dhaliwal, A. S.; Sonkawade, R. G.

    2013-02-05

    In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV {sup 60}Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

  4. Microhardness evaluations of resin-dentin bonding areas by nano-indentation.

    PubMed

    Nakazawa, Y; Seino, E; Ushiki, T; Ogata, T; Hirai, Y; Kawada, E; Oda, Y

    1999-02-01

    The purpose of this experiment was to determine the hardness values of the hybrid layer and its surroundings through the continuous use of a microhardness measuring device. Black's Class V cavities were prepared in nine dog teeth. The cavities were divided into four groups according to the dentin adhesive system applied. The adhesive systems were: "Bond One System", "Liner Bond II sigma System", "One Step System", and "Single Bond System". The treated teeth were observed at seven days post-application. Specimens were cross-sectioned perpendicularly or horizontally to the resin-dentin interface and embedded in epoxy resin. Their surfaces were polished. The microhardness of the resin-dentin bonding area was measured with a nano-indentation tester. The hardness values at a point of 10 microns distant from the interface in the direction of the dentin differed between systems. It appeared that this was influenced by the presence of the decalcified dentin not impregnated by resin, differences in the chemistry forming the hybrid layer, and the composition of the bonding resin. The hardness of the dentin-bonding interface and its surroundings was determined, and these areas were observed using SEM. Three layers were confirmed the healthy dentin layer, the composite resin layer, and the hybrid layer, (in which decalcified dentin impregnated by resin and that not impregnated by resin are considered to be mix). In the hybrid layer, no impression was found by SEM although the hardness in the bonding interface was significantly different. These layers appear to be more elastic and softer than the healthy dentin. PMID:10522177

  5. Structural and nanoindentation studies of stem cell-based tissue-engineered bone.

    PubMed

    Pelled, Gadi; Tai, Kuangshin; Sheyn, Dima; Zilberman, Yoram; Kumbar, Sangamesh; Nair, Lakshmi S; Laurencin, Cato T; Gazit, Dan; Ortiz, Christine

    2007-01-01

    Stem cell-based gene therapy and tissue engineering have been shown to be an efficient method for the regeneration of critical-sized bone defects. Despite being an area of active research over the last decade, no knowledge of the intrinsic ultrastructural and nanomechanical properties of such bone tissue exists. In this study, we report the nanomechanical properties of engineered bone tissue derived from genetically modified mesenchymal stem cells (MSCs) overexpressing the rhBMP2 gene, grown in vivo in the thigh muscle of immunocompetent mice for 4 weeks, compared to femoral bone adjacent to the transplantation site. The two types of bone had similar mineral contents (61 and 65 wt% for engineered and femoral bone, respectively), overall microstructures showing lacunae and canaliculi (both measured by back-scattered electron microscopy), chemical compositions (measured by energy dispersive X-ray analysis), and nanoscale topographical morphologies (measured by tapping-mode atomic force microscopy imaging or TMAFM). Nanoindentation experiments revealed that the small length scale mechanical properties were statistically different with the femoral bone (indented parallel to the bone long axis) being stiffer and harder (apparent elastic modulus, E approximately 27.3+/-10.5 GPa and hardness, H approximately 1.0+/-0.7G Pa) than the genetically engineered bone (E approximately 19.8+/-5.6 GPa, H approximately 0.9+/-0.4G Pa). TMAFM imaging showed clear residual indents characteristic of viscoelastic plastic deformation for both types of bone. However, fine differences in the residual indent area (smaller for the engineered bone), pile up (smaller for the engineered bone), and fracture mechanisms (microcracks for the engineered bone) were observed with the genetically engineered bone behaving more brittle than the femoral control.

  6. Implications of the contact radius to line step (CRLS) ratio in AFM for nanotribology measurements.

    PubMed

    Helt, James M; Batteas, James D

    2006-07-01

    Investigating the mechanisms of defect generation and growth at surfaces on the nanometer scale typically requires high-resolution tools such as the atomic force microscope (AFM). To accurately assess the kinetics and activation parameters of defect production over a wide range of loads (F(z)), the AFM data should be properly conditioned. Generally, AFM wear trials are performed over an area defined by the length of the slow (L(sscan)) and fast scan axes. The ratio of L(sscan) to image resolution (res, lines per image) becomes an important experimental parameter in AFM wear trials because it defines the magnitude of the line step (LS = L(sscan)/res), the distance the AFM tip steps along the slow scan axis. Comparing the contact radius (a) to the line step (LS) indicates that the overlap of successive scans will result unless the contact radius-line step ratio (CRLS) is < or =(1)/(2). If this relationship is not considered, then the scan history (e.g., contact frequency) associated with a single scan is not equivalent at different loads owing to the scaling of contact radius with load (a proportional variant F(z)(1/3)). Here, we present a model in conjunction with empirical wear tests on muscovite mica to evaluate the effects of scan overlap on surface wear. Using the Hertz contact mechanics definition of a, the CRLS model shows that scan overlap pervades AFM wear trials even under low loads. Such findings indicate that simply counting the number of scans (N(scans)) in an experiment underestimates the full history conveyed to the surface by the tip and translates into an error in the actual extent to which a region on the surface is contacted. Utilizing the CRLS method described here provides an approach to account for image scan history accurately and to predict the extent of surface wear. This general model also has implications for any AFM measurement where one wishes to correlate scan-dependent history to image properties as well as feature resolution in scanned

  7. Implications of the contact radius to line step (CRLS) ratio in AFM for nanotribology measurements.

    PubMed

    Helt, James M; Batteas, James D

    2006-07-01

    Investigating the mechanisms of defect generation and growth at surfaces on the nanometer scale typically requires high-resolution tools such as the atomic force microscope (AFM). To accurately assess the kinetics and activation parameters of defect production over a wide range of loads (F(z)), the AFM data should be properly conditioned. Generally, AFM wear trials are performed over an area defined by the length of the slow (L(sscan)) and fast scan axes. The ratio of L(sscan) to image resolution (res, lines per image) becomes an important experimental parameter in AFM wear trials because it defines the magnitude of the line step (LS = L(sscan)/res), the distance the AFM tip steps along the slow scan axis. Comparing the contact radius (a) to the line step (LS) indicates that the overlap of successive scans will result unless the contact radius-line step ratio (CRLS) is < or =(1)/(2). If this relationship is not considered, then the scan history (e.g., contact frequency) associated with a single scan is not equivalent at different loads owing to the scaling of contact radius with load (a proportional variant F(z)(1/3)). Here, we present a model in conjunction with empirical wear tests on muscovite mica to evaluate the effects of scan overlap on surface wear. Using the Hertz contact mechanics definition of a, the CRLS model shows that scan overlap pervades AFM wear trials even under low loads. Such findings indicate that simply counting the number of scans (N(scans)) in an experiment underestimates the full history conveyed to the surface by the tip and translates into an error in the actual extent to which a region on the surface is contacted. Utilizing the CRLS method described here provides an approach to account for image scan history accurately and to predict the extent of surface wear. This general model also has implications for any AFM measurement where one wishes to correlate scan-dependent history to image properties as well as feature resolution in scanned

  8. AFM Studies of Lunar Soils and Application to the Mars 2001 Mission

    NASA Technical Reports Server (NTRS)

    Weitz, C. M.; Anderson, M. S.; Marshall, J.

    1999-01-01

    NMCA experiment will be able to define grain transport and weathering processes. For example, it should be possible to determine if Martian grains have been subjected to aeolian or water transport, volcanic activity, impact melting processes, in-situ weathering, and a host of other processes. Additionally, textural maturity could be assessed (via freshness and form of fracture patterns and grain shapes). Thus, the AFM has the potential to shed new light on Martian surface processes by adding the submicroscopic dimension to planetary investigations.

  9. Structural impact of cations on lipid bilayer models: nanomechanical properties by AFM-force spectroscopy.

    PubMed

    Redondo-Morata, Lorena; Giannotti, Marina I; Sanz, Fausto

    2014-02-01

    Atomic Force Microscopy (AFM) has become an invaluable tool for studying the micro- and nanoworlds. As a stand-alone, high-resolution imaging technique and force transducer, it defies most other surface instrumentation in ease of use, sensitivity and versatility. The main strength of AFM relies on the possibility to operate in an aqueous environment on a wide variety of biological samples, from single molecules - DNA or proteins - to macromolecular assemblies like biological membranes. Understanding the effect of mechanical stress on membranes is of primary importance in biophysics, since cells are known to perform their function under a complex combination of forces. In the later years, AFM-based Force-Spectroscopy (AFM-FS) has provided a new vista on membrane mechanics in a confined area within the nanometer realm, where most of the specific molecular interactions take place. Lipid membranes are electrostatically charged entities that physiologically coexist with electrolyte solutions. Thus, specific interactions with ions are a matter of considerable interest. The distribution of ions in the solution and their interaction with the membranes are factors that substantially modify the structure and dynamics of the cell membranes. Furthermore, signaling processes are modified by the membrane capability of retaining ions. Supported Lipid Bilayers (SLBs) are a versatile tool to investigate phospholipid membranes mimicking biological surfaces. In the present contribution, we review selected experiments on the mechanical stability of SLBs as models of lipid membranes by means of AFM-FS, with special focus on the effect of cations and ionic strength in the overall nanomechanical stability. PMID:24341385

  10. Nanoscale structural features determined by AFM for single virus particles.

    PubMed

    Chen, Shu-wen W; Odorico, Michael; Meillan, Matthieu; Vellutini, Luc; Teulon, Jean-Marie; Parot, Pierre; Bennetau, Bernard; Pellequer, Jean-Luc

    2013-11-21

    In this work, we propose "single-image analysis", as opposed to multi-image averaging, for extracting valuable information from AFM images of single bio-particles. This approach allows us to study molecular systems imaged by AFM under general circumstances without restrictions on their structural forms. As feature exhibition is a resolution correlation, we have performed AFM imaging on surfaces of tobacco mosaic virus (TMV) to demonstrate variations of structural patterns with probing resolution. Two AFM images were acquired with the same tip at different probing resolutions in terms of pixel width, i.e., 1.95 and 0.49 nm per pixel. For assessment, we have constructed an in silico topograph based on the three-dimensional crystal structure of TMV as a reference. The prominent artifacts observed in the AFM-determined shape of TMV were attributed to tip convolutions. The width of TMV rod was systematically overestimated by ~10 nm at both probing resolutions of AFM. Nevertheless, the effects of tip convolution were less severe in vertical orientation so that the estimated height of TMV by AFM imaging was in close agreement with the in silico X-ray topograph. Using dedicated image processing algorithms, we found that at low resolution (i.e., 1.95 nm per pixel), the extracted surface features of TMV can be interpreted as a partial or full helical repeat (three complete turns with ~7.0 nm in length), while individual protein subunits (~2.5 nm) were perceivable only at high resolution. The present study shows that the scales of revealed structural features in AFM images are subject to both probing resolution and processing algorithms for image analysis. PMID:24056758

  11. Dissolution of uranophane: An AFM, XPS, SEM and ICP study

    NASA Astrophysics Data System (ADS)

    Schindler, Michael; Freund, Michael; Hawthorne, Frank C.; Burns, Peter C.; Maurice, Patricia A.

    2009-05-01

    Dissolution experiments on single crystals of uranophane and uranophane-β, Ca(H 2O) 5[(UO 2)(SiO 3(OH)] 2, from the Shinkolobwe mine of the Democratic Republic of Congo, were done in an aqueous HCl solution of pH 3.5 for 3 h, in HCl solutions of pH 2 for 5, 10 and 30 min, and in Pb 2+-, Ba-, Sr-, Ca- and Mg-HCl solutions of pH 2 for 30 min. The basal surfaces of the treated uranophane crystals were examined using atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Solutions after dissolution experiments on single crystals and synthetic powders were analysed with inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectroscopy (ICP-MS). The morphology of the observed etch pits (measured by AFM) were compared to the morphology, predicted on the basis of the bond-valence deficiency of polyhedron chains along the edges of the basal surface. Etch pits form in HCl solutions of pH 2. Their decrease in depth with the duration of the dissolution experiment is explained with the stepwave dissolution model, which describes the lowering of the surrounding area of an etch pit with continuous waves of steps emanated from the etch pit into the rest of the crystal surface. Hillocks form in an HCl solution of pH 3.5, and the chemical composition of the surface (as indicated by XPS) shows that these hillocks are the result of the precipitation of a uranyl-hydroxy-hydrate phase. Well-orientated hillocks form on the surface of uranophane in a SrCl 2-HCl solution of pH 2. They are part of an aged silica coating of composition Si 2O 2(OH) 4(H 2O) n. An amorphous layer forms on the surface of uranophane in a MgCl 2-HCl solution of pH 2, which has a composition and structure similar to silicic acid. Small crystallites of uranyl-hydroxy-hydrate phases form on the surface of uranophane after treatment in Pb(NO 3) 2-HCl and BaCl 2-HCl solutions of pH 2. Dissolution experiments on synthetic uranophane powders

  12. Study of relaxation and transport processes by means of AFM based dielectric spectroscopy

    SciTech Connect

    Miccio, Luis A.

    2014-05-15

    Since its birth a few years ago, dielectric spectroscopy studies based on atomic force microscopy (AFM) have gained a growing interest. Not only the frequency and temperature ranges have become broader since then but also the kind of processes that can be studied by means of this approach. In this work we analyze the most adequate experimental setup for the study of several dielectric processes with a spatial resolution of a few nanometers by using force mode AFM based dielectric spectroscopy. Proof of concept experiments were performed on PS/PVAc blends and PMMA homopolymer films, for temperatures ranging from 300 to 400 K. Charge transport processes were also studied by this approach. The obtained results were analyzed in terms of cantilever stray contribution, film thickness and relaxation strength. We found that the method sensitivity is strongly coupled with the film thickness and the relaxation strength, and that it is possible to control it by using an adequate experimental setup.

  13. AFM investigation and optical band gap study of chemically deposited PbS thin films

    NASA Astrophysics Data System (ADS)

    Zaman, S.; Mansoor, M.; Abubakar; Asim, M. M.

    2016-08-01

    The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

  14. Determination of work of adhesion of biological cell under AFM bead indentation.

    PubMed

    Zhu, Xinyao; Siamantouras, E; Liu, K K; Liu, X

    2016-03-01

    Hertz contact theory has been widely used for the determination of cell elasticity based on AFM indentation experiments. In light of the adhesive contact between AFM tip and cell, this study applied Johnson-Kendall-Roberts (JKR) model to fit the indentation force-displacement (F-D) curves reported previously. A MIN6 cell has been modeled as first a sphere and then a flattened cell with different thicknesses. The results have shown that both basic JKR model and "generalized" JKR model can best describe the unloading force-displacement behaviors of the indentation curves. The Young׳s modulus of the cell and the work of adhesion of the cell-indenter interface are obtained. In comparison to the Hertzian contact model, the JKR model provides obviously better fitting to the experimental results, indicating that the adhesion is significant in the cell interaction. PMID:26688423

  15. The deformation of gum metal under nanoindentation and sub-micron pillar compression

    NASA Astrophysics Data System (ADS)

    Withey, Elizabeth Ann

    Reaching ideal strength has proven to be difficult in most materials. Dislocation slip, phase transformations, twinning, and fracture all tend to occur at stresses well below the ideal strength of a material. Only on very small scales has it been possible to approach ideal strength. Thus, it was of great interest when a set of beta-Ti alloys, Gum Metal, were found to have a bulk yield strength close to half of its ideal strength. However, some recent studies have questioned the reliability of this claim. Several studies have suggested Gum Metal deforms by dislocation slip. Others have suggested the possibility of transformation-induced plasticity. The present study was undertaken in order to help clarify if and how Gum Metal can reach ideal strength. Two different experiments, ex situ nanoindentation and quantitative in situ nanopillar compression in a transmission electron microscope to correlate real-time deformation behavior, were performed on a single composition of Gum Metal, Ti-23Nb-0.7Ta-2Zr-1.20 at. %, obtained from Toyota Central R&D Laboratories. Nanoindented specimens were thinned from the bottom surface until the pits of multiple indentations became electron-transparent allowing for qualitative analysis of the deformation microstructure in both fully cold-worked and solution-treated specimens. Real-time load-displacement behavior from the nanopillar compression tests was correlated with real-time video recorded during each compression to determine both the compressive strength of each pillar and the timing and strengths of different deformation behaviors observed. Combining the results from both experiments provided several important conclusions. First, Gum Metal approaches and can attain ideal strength in nanopillars regardless of processing condition. While dislocations exist in Gum Metal, they can be tightly pinned by obstacles with spacing less than ˜20 nm, which should inhibit their motion at strengths below the ideal shear strength. The plastic

  16. Mechanical Characterization of Nanoporous Thin Films by Nanoindentation and Laser-induced Surface Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Chow, Gabriel

    Thin films represent a critical sector of modern engineering that strives to produce functional coatings at the smallest possible length scales. They appear most commonly in semiconductors where they form the foundation of all electronic circuits, but exist in many other areas to provide mechanical, electrical, chemical, and optical properties. The mechanical characterization of thin films has been a continued challenge due foremost to the length scales involved. However, emerging thin films focusing on materials with significant porosity, complex morphologies, and nanostructured surfaces produce additional difficulties towards mechanical analysis. Nanoindentation has been the dominant thin film mechanical characterization technique for the last decade because of the quick results, wide range of sample applicability, and ease of sample preparation. However, the traditional nanoindentation technique encounters difficulties for thin porous films. For such materials, alternative means of analysis are desirable and the lesser known laser-induced surface acoustic wave technique (LiSAW) shows great potential in this area. This dissertation focuses on studying thin, porous, and nanostructured films by nanoindentation and LiSAW techniques in an effort to directly correlate the two methodologies and to test the limits and applicabilities of each technique on challenging media. The LiSAW technique is particularly useful for thin porous films because unlike indentation, the substrate is properly accounted for in the wave motion analysis and no plastic deformation is necessary. Additionally, the use of lasers for surface acoustic wave generation and detection allows the technique to be fully non-contact. This is desirable in the measurement of thin, delicate, and porous films where physical sample probing may not be feasible. The LiSAW technique is also valuable in overcoming nanoscale roughness, particularly for films that cannot be mechanically polished, since typical SAW

  17. Cellular mechanoadaptation to substrate mechanical properties: contributions of substrate stiffness and thickness to cell stiffness measurements using AFM.

    PubMed

    Vichare, Shirish; Sen, Shamik; Inamdar, Mandar M

    2014-02-28

    Mechanosensing by adherent cells is usually studied by quantifying cell responses on hydrogels that are covalently linked to a rigid substrate. Atomic force microscopy (AFM) represents a convenient way of characterizing the mechanoadaptation response of adherent cells on hydrogels of varying stiffness and thickness. Since AFM measurements reflect the effective cell stiffness, therefore, in addition to measuring real cytoskeletal alterations across different conditions, these measurements might also be influenced by the geometry and physical properties of the substrate itself. To better understand how the physical attributes of the gel influence AFM stiffness measurements of cells, we have used finite element analysis to simulate the indentation of cells of various spreads resting on hydrogels of varying stiffness and thickness. Consistent with experimental results, our simulation results indicate that for well spread cells, stiffness values are significantly over-estimated when experiments are performed on cells cultured on soft and thin gels. Using parametric studies, we have developed scaling relationships between the effective stiffness probed by AFM and the bulk cell stiffness, taking cell and tip geometry, hydrogel properties, nuclear stiffness and cell contractility into account. Finally, using simulated mechanoadaptation responses, we have demonstrated that a cell stiffening response may arise purely due to the substrate properties. Collectively, our results demonstrate the need to take hydrogel properties into account while estimating cell stiffness using AFM indentation. PMID:24651595

  18. Simulation and experimental analysis of nanoindentation and mechanical properties of amorphous NiAl alloys.

    PubMed

    Wang, Chih-Hao; Fang, Te-Hua; Cheng, Po-Chien; Chiang, Chia-Chin; Chao, Kuan-Chi

    2015-06-01

    This paper used numerical and experimental methods to investigate the mechanical properties of amorphous NiAl alloys during the nanoindentation process. A simulation was performed using the many-body tight-binding potential method. Temperature, plastic deformation, elastic recovery, and hardness were evaluated. The experimental method was based on nanoindentation measurements, allowing a precise prediction of Young's modulus and hardness values for comparison with the simulation results. The indentation simulation results showed a significant increase of NiAl hardness and elastic recovery with increasing Ni content. Furthermore, the results showed that hardness and Young's modulus increase with increasing Ni content. The simulation results are in good agreement with the experimental results. Adhesion test of amorphous NiAl alloys at room temperature is also described in this study. PMID:26037150

  19. Modelling the nanomechanical response of a micro particle–matrix system for nanoindentation tests

    NASA Astrophysics Data System (ADS)

    Cao, Yunyi; Duan, Pengfei; Chen, Jinju

    2016-05-01

    A lot of experimental, numerical simulation and analytical modelling work has been done on how the substrate affects the measured hardness and elastic modulus of the coating/substrate system for nanoindentation tests. Little work has been done on the elastic–plastic behaviour of micro particle–matrix systems. Clifford et al have proposed an empirical model to describe the spatially dependent composite modulus during nanoindentation tests for linear elastic particles embedded in a linear elastic matrix. However, no such models have been developed for elastic–plastic composites. In this study, finite element simulations were used to determine the elastic modulus and hardness of hard particles embedded in a soft matrix and vice versa. An extended Clifford model has been developed to determine the elastic modulus and hardness for elastic–plastic composites with various particle shapes and volume fractions.

  20. Water-dependent micromechanical and rheological properties of silica colloidal crystals studied by nanoindentation.

    PubMed

    Gallego-Gómez, Francisco; Morales-Flórez, Víctor; Blanco, Alvaro; de la Rosa-Fox, Nicolás; López, Cefe

    2012-09-12

    Here we show the suitability of nanoindentation to study in detail the micromechanical response of silica colloidal crystals (CCs). The sensitivity to displacements smaller than the submicrometer spheres size, even resolving discrete events and superficial features, revealed particulate features with analogies to atomic crystals. Significant robustness, long-range structural deformation, and large energy dissipation were found. Easily implemented temperature/rate-dependent nanoindentation quantified the paramount role of adsorbed water endowing silica CCs with properties of wet granular materials like viscoplasticity. A novel "nongranular" CC was fabricated by substituting capillary bridges with silica necks to directly test water-independent mechanical response. Silica CCs, as specific (nanometric, ordered) wet granular assemblies with well-defined configuration, may be useful model systems for granular science and capillary cohesion at the nanoscale.

  1. Indenter geometry effects on the measurements of mechanical properties by nanoindentation with sharp indenters

    SciTech Connect

    Tsui, T.Y.; Pharr, G.M.; Oliver, W.C.

    1996-05-01

    The measurement of mechanical properties by nanoindentation methods is most often conducted using indenters with the Berkovich geometry (a triangular pyramid) or with a sphere. These indenters provide a wealth of information, but there are certain circumstances in which it would be useful to make measurements with indenters of other geometries. We have recently explored how the measurement of hardness and elastic modulus can be achieved using sharp indenters other than the Berkovich. Systematic studies in several materials were conducted with a Vickers indenter, a conical indenter with a half-included tip angle of 70.3{degrees}, and the standard Berkovich indenter. All three indenters are geometrically similar and have nominally the same area-to-depth relationship, but there are distinct differences in the behavior of each. Here, we report on the application of these indenters in the measurement of hardness and elastic modulus by nanoindentation methods and some of the difficulties that occur.

  2. The nano-mechanical signature of Ultra High Performance Concrete by statistical nanoindentation techniques

    SciTech Connect

    Sorelli, Luca Constantinides, Georgios; Ulm, Franz-Josef; Toutlemonde, Francois

    2008-12-15

    Advances in engineering the microstructure of cementitious composites have led to the development of fiber reinforced Ultra High Performance Concretes (UHPC). The scope of this paper is twofold, first to characterize the nano-mechanical properties of the phases governing the UHPC microstructure by means of a novel statistical nanoindentation technique; then to upscale those nanoscale properties, by means of continuum micromechanics, to the macroscopic scale of engineering applications. In particular, a combined investigation of nanoindentation, scanning electron microscope (SEM) and X-ray Diffraction (XRD) indicates that the fiber-matrix transition zone is relatively defect free. On this basis, a four-level multiscale model with defect free interfaces allows to accurately determine the composite stiffness from the measured nano-mechanical properties. Besides evidencing the dominant role of high density calcium silicate hydrates and the stiffening effect of residual clinker, the suggested model may become a useful tool for further optimizing cement-based engineered composites.

  3. Surface hardening induced by high flux plasma in tungsten revealed by nano-indentation

    NASA Astrophysics Data System (ADS)

    Terentyev, D.; Bakaeva, A.; Pardoen, T.; Favache, A.; Zhurkin, E. E.

    2016-08-01

    Surface hardness of tungsten after high flux deuterium plasma exposure has been characterized by nanoindentation. The effect of plasma exposure was rationalized on the basis of available theoretical models. Resistance to plastic penetration is enhanced within the 100 nm sub-surface region, attributed to the pinning of geometrically necessary dislocations on nanometric deuterium cavities - signature of plasma-induced defects and deuterium retention. Sub-surface extension of thereby registered plasma-induced damage is in excellent agreement with the results of alternative measurements. The study demonstrates suitability of nano-indentation to probe the impact of deposition of plasma-induced defects in tungsten on near surface plasticity under ITER-relevant plasma exposure conditions.

  4. Direct observation of hydration of TiO 2 on Ti using electrochemical AFM: freely corroding versus potentiostatically held

    NASA Astrophysics Data System (ADS)

    Bearinger, Jane P.; Orme, Christine A.; Gilbert, Jeremy L.

    2001-10-01

    Hydration of titanium/titanium oxide surfaces under freely corroding and potentiostatically held conditions has been characterized using electrochemical atomic force microscopy (EC AFM). In contrast to conventional high vacuum techniques, AFM enables measurement of morphological surface structure in the in situ hydrated state. Electrochemical probes in the imaging environment further enable acquisition of electrical characteristics during AFM imaging. Experiments were performed on etched, electropolished commercially pure titanium. As noted by direct observation and corroborated by power spectral density (Fourier analysis) measurements, oxide domes cover the titanium surface and grow laterally during hydration. Applied potential altered the growth rate. Under open circuit potential conditions, growth proceeded approximately six times faster than under a -1 V applied voltage ( 1098±52 nm2/ min ± versus 184.84±19 nm2/min). Film growth increased electrical resistance and lowered interfacial capacitance based on step polarization impedance spectroscopy tests.

  5. Nanoindentation Studies Of Hard Nanocomposite Ti-B-N Thin Films

    SciTech Connect

    Rupa, P. Karuna Purnapu; Chakraborty, P. C.; Mishra, Suman Kumari

    2011-12-12

    Titanium boron nitride (Ti-B-N) films were deposited by reactive magnetron sputtering using single Titanium diboride (TiB{sub 2}) target in different Ar-N{sub 2} gas mixtures. The influence of N{sub 2}:Ar ratio on the microstructure and mechanical properties of the deposited films have been investigated. Atomic force microscopy analysis indicated the grain size decreases with incorporation of nitrogen in the films. Nanoindentation studies have shown the hardness decreases with nitrogen incorporation.

  6. Characterization of carbon fiber reinforced resin composites by the nanoindentation technique

    NASA Astrophysics Data System (ADS)

    Sun, Yuli; Zuo, Dunwen; Cao, Lianjing; Lu, Wenzhuang; Zhu, Yongwei; Li, Jun

    2013-08-01

    The mechanical properties of carbon fiber reinforced resin composites (CFRP) including the epoxy matrix, the carbon fiber and the interface of the carbon fiber/epoxy composites were investigated by means of nanoindentation technique. The hardness, Young's modulus of the components in CFRP were obtained. The results show that the hardness and Young's modulus have a gradient variation from the epoxy matrix to carbon fiber.

  7. Characterization of surface/subsurface damage for ceramics with nanoindentation method

    NASA Astrophysics Data System (ADS)

    Bao, Yumei; Chai, Guozhong; Gu, Shengting

    2010-08-01

    Ceramics are increasingly used in the fields of aerospace, communication, mechanical and modern biomedical engineering. With high hardness, strength and abrasive resistance, the machined ceramic components are most likely to contain surface/subsurface damages, influencing strongly the performance and reliability of ceramic components. Nanoindentation test is an advanced technology in measuring the elastic modulus and hardness of the materials in micro-nano scale based on Oliver-Phar's equation. Nanoindentation has been employed extensively to characterize the mechanical properties of a wide range of materials including ceramics. To characterize the surface/subsurface damage in ceramics, a degraded elastic modulus based damage variable is defined to describe the damage induced property degradation of the materials based on the traditional Kachanov continuum damage mechanics (CDM) framework. A simple characterization method for surface/subsurface damage is realized based on nanoindentation test. The alumina bulk samples are chosen to study the surface/subsurface indentation induced damage by nanoindentaiton. The elastic modulus under various indenting loads is measured with Conical and Berkovich tip. The variation of the elastic modulus and indentation induced damage with load and displacement are analyzed in detail. Experimental results show that the proposed method is feasible and satisfactory.

  8. Depth Dependence of the Mechanical Properties of Human Enamel by Nanoindentation

    SciTech Connect

    Zhou, J; Hsiung, L L

    2006-02-17

    Nanoindentation has recently emerged to be the primary method to study the mechanical behavior and reliability of human enamel. Its hardness and elastic modulus were generally reported as average values with standard deviations that were calculated from the results of multiple nanoindentation tests. In such an approach, it is assumed that the mechanical properties of human enamel are constant, independent of testing parameters, like indent depth and loading rate. However, little is known if they affect the measurements. In this study, we investigated the dependence of the hardness and elastic modulus of human enamel on the indent depth. We found that in a depth range from 100 nm to 2000 nm the elastic moduli continuously decreased from {approx} 104 GPa to {approx} 70 GPa, and the hardnesses decreased from {approx} 5.7 GPa to {approx} 3.6 GPa. We then considered human enamel as a fiber-reinforced composite, and used the celebrated rule of mixture theory to quantify the upper and lower bounds of the elastic moduli, which were shown to cover the values measured in the current study and previous studies. Accordingly, we attributed the depth dependence of the hardness and modulus to the continuous microstructure evolution induced by nanoindenter.

  9. Microstructure Characterization by Means of X-ray Micro-CT and Nanoindentation Measurements

    NASA Astrophysics Data System (ADS)

    Rajczakowska, Magdalena; Stefaniuk, Damian; Łydżba, Dariusz

    2015-03-01

    The aim of this paper is to present an example of the material microstructure characterization with the use of X-ray micro-CT and nanoindentation measurements. Firstly, the current scope of application of the aforementioned techniques is provided within different fields of science. Then, background of each of the methods is presented. The methodology of X-ray micro-CT is described with the emphasis on the Beer's law formulation. In addition, the basics of the nanoindentation technique are outlined and major formulas for the hardness and Young's modulus calculation are given. Finally, example results for a concrete sample are presented. The microstructure of the selected material is firstly characterized in terms of geometry using the results from the microtomograhy measurements, e.g., porosity and attenuation profiles, pore and aggregate size distribution, shape factor of pores, etc. Next, the results of the nanoindentation tests are provided, namely the hardness and Young's modulus versus the height of the sample. The influence of the number of tests and statistical analysis on the final results is underlined.

  10. Measuring residual stress in ceramic zirconia-porcelain dental crowns by nanoindentation.

    PubMed

    Zhang, Y; Allahkarami, M; Hanan, J C

    2012-02-01

    Residual stress plays a critical role in failure of ceramic dental crowns. The magnitude and distribution of residual stress in the crown system are largely unknown. Determining the residual stress quantitatively is challenging since the crown has such complex contours and shapes. This work explored the feasibility and validity of measuring residual stress of zirconia and porcelain in ceramic crowns by nanoindentation. Nanoindentation tests were performed on the cross-section of a crown for both porcelain and zirconia along four critical locations: the thickest, thinnest and medium porcelain thicknesses. Zirconia and porcelain pieces, chipped off from the crown and annealed at 400 °C, were used as reference samples. The residual stress was determined by comparing the measured hardness of the stressed sample with that of the reference sample. Nanoindentation impression images were acquired through a scanning probe microscope (SPM) equipped with a Hysitron Triboindenter. Zirconia showed large pile-up. Residual stress is determined along the thickness of crowns at the chosen locations for both porcelain and zirconia. The measured results were compared with the results from X-ray diffraction (XRD) and finite element modeling (FEM). Results show there are large amounts of residual stresses in the dental crown and their magnitude differs between locations due to the complex shape of the crown. The average residual stress readings were as high as -637 MPa and 323 MPa for zirconia and porcelain respectively.

  11. A novel sample preparation method to avoid influence of embedding medium during nano-indentation

    NASA Astrophysics Data System (ADS)

    Meng, Yujie; Wang, Siqun; Cai, Zhiyong; Young, Timothy M.; Du, Guanben; Li, Yanjun

    2013-02-01

    The effect of the embedding medium on the nano-indentation measurements of lignocellulosic materials was investigated experimentally using nano-indentation. Both the reduced elastic modulus and the hardness of non-embedded cell walls were found to be lower than those of the embedded samples, proving that the embedding medium used for specimen preparation on cellulosic material during nano-indentation can modify cell-wall properties. This leads to structural and chemical changes in the cell-wall constituents, changes that may significantly alter the material properties. Further investigation was carried out to detect the influence of different vacuum times on the cell-wall mechanical properties during the embedding procedure. Interpretation of the statistical analysis revealed no linear relationships between vacuum time and the mechanical properties of cell walls. The quantitative measurements confirm that low-viscosity resin has a rapid penetration rate early in the curing process. Finally, a novel sample preparation method aimed at preventing resin diffusion into lignocellulosic cell walls was developed using a plastic film to wrap the sample before embedding. This method proved to be accessible and straightforward for many kinds of lignocellulosic material, but is especially suitable for small, soft samples.

  12. Evaluation of the degradation of plasma sprayed thermal barrier coatings using nano-indentation.

    PubMed

    Kim, Dae-Jin; Cho, Sung-Keun; Choi, Jung-Hun; Koo, Jae-Mean; Seok, Chang-Sung; Kim, Moon-Young

    2009-12-01

    In this study, the disk type of a thermal barrier coating (TBC) system for a gas turbine blade was isothermally aged at 1100 degrees C for various times up to 400 hours. For each aging condition, the thickness of the thermally grown oxide (TGO) was measured by optical microscope and mechanical properties such as the elastic modulus and hardness were measured by micro-indentation and nano-indentation on the cross-section of a coating specimen. In the case of micro-indentation, the mechanical properties of a Ni-base superalloy substrate and MCrAlY bond coat material did not significantly change with an increase in exposure time. In the case of nano-indentation, the gamma-Ni phase and beta-NiAl phase in the bond coat and top coat material show no significant change in their properties. However, the elastic modulus and the hardness of TGO show a remarkable decrease from 100 h to 200 h then remain nearly constant after 200 h due to the internal delamination of TBC. It has been confirmed that the nano-indentation technique is a very effective way to evaluate the degradation of a thermal barrier coating system. PMID:19908771

  13. Hierarchical structure observation and nanoindentation size effect characterization for a limnetic shell

    NASA Astrophysics Data System (ADS)

    Song, Jingru; Fan, Cuncai; Ma, Hansong; Wei, Yueguang

    2015-06-01

    In the present research, hierarchical structure observation and mechanical property characterization for a type of biomaterial are carried out. The investigated biomaterial is Hyriopsis cumingii, a typical limnetic shell, which consists of two different structural layers, a prismatic "pillar" structure and a nacreous "brick and mortar" structure. The prismatic layer looks like a "pillar forest" with variation-section pillars sized on the order of several tens of microns. The nacreous material looks like a "brick wall" with bricks sized on the order of several microns. Both pillars and bricks are composed of nanoparticles. The mechanical properties of the hierarchical biomaterial are measured by using the nanoindentation test. Hardness and modulus are measured for both the nacre layer and the prismatic layer, respectively. The nanoindentation size effects for the hierarchical structural materials are investigated experimentally. The results show that the prismatic nanostructured material has a higher stiffness and hardness than the nacre nanostructured material. In addition, the nanoindentation size effects for the hierarchical structural materials are described theoretically, by using the trans-scale mechanics theory considering both strain gradient effect and the surface/interface effect. The modeling results are consistent with experimental ones.

  14. Durability of crystalline phase in concrete microstructure modified by the mineral powders: evaluation by nanoindentation tests

    NASA Astrophysics Data System (ADS)

    Rajczakowska, Magdalena; Łydżba, Dariusz

    2016-03-01

    This paper presents the nanoindentation investigation of the evolution of concrete microstructure modified by the Internal Crystallization Technology mineral powders. The samples under study were retrieved from a fragment of a circular concrete lining of the vertical mine shaft at a depth of approximately 1,000 m. Due to the aggressive environment and exposure to contaminated water, the internal surface of the structure was deteriorated, decreasing its strength significantly. The mineral powders were applied directly on the surface lining. The specimens were investigated one month, three months and one year after the application of the aforementioned substance in order to verify the time dependence of the strengthening processes and durability of the crystalline phase. The microstructural changes of concrete were assessed with the use of nanoindentation technique. The testing procedure involved including the previously cut specimens in the epoxy resin and grinding and polishing in order to reduce the surface roughness. As a result of the nanoindentation tests the hardness as well as Young's modulus of the material were evaluated. The results were then compared and statistically analyzed. As a consequence, the disintegration time of the crystalline network in the pores of concrete was identified.

  15. Fracture toughness of esthetic dental coating systems by nanoindentation and FIB sectional analysis.

    PubMed

    Pecnik, Christina Martina; Courty, Diana; Muff, Daniel; Spolenak, Ralph

    2015-07-01

    Improving the esthetics of Ti-based dental implants is the last challenge remaining in the optimization process. The optical issues were recently solved by the application of highly and selectively reflective coatings on Ti implants. This work focuses on the mechanical durability of these esthetic ceramic based coating systems (with and without adhesion layers). The coating systems (Ti-ZrO2, Ti-Al-ZrO2, Ti-Ti-Al-ZrO2, Ti-Ag-ZrO2, Ti-Ti-Ag-ZrO2, Ti-Bragg and Ti-TiO2-Bragg) were subjected to nanoindentation experiments and examined using scanning electron microscopy and focused ion beam cross sectional analysis. Three coating systems contained adhesion layers (10nm of Ti or 60nm of TiO2 layers). The fracture toughness of selected samples was assessed applying two different models from literature, a classical for bulk materials and an energy-based model, which was further developed and adjusted. The ZrO2 based coating systems (total film thickness<200nm) followed a circumferential cracking behavior in contrast to Bragg coated samples (total film thickness around 1.5μm), which showed radial cracking emanating from the indent corners. For Ti-ZrO2 samples, a fracture toughness between 2.70 and 3.70MPam(1/2) was calculated using an energy-based model. The classical model was applied to Bragg coated samples and their fracture toughness ranged between 0.70 and 0.80MPam(1/2). Furthermore, coating systems containing an additional layer (Ti-Ti-Al-ZrO2, Ti-Ti-Ag-ZrO2 and Ti-TiO2-Bragg) showed an improved adhesion between the substrate and the coating. The addition of a Ti or TiO2 layer improved the adhesion between substrate and coating. The validity of the models for the assessment of the fracture toughness depended on the layer structure and fracture profile of the samples investigated here (classical model for thick coatings and energy-based model for thin coatings). PMID:25837339

  16. Fracture toughness of esthetic dental coating systems by nanoindentation and FIB sectional analysis.

    PubMed

    Pecnik, Christina Martina; Courty, Diana; Muff, Daniel; Spolenak, Ralph

    2015-07-01

    Improving the esthetics of Ti-based dental implants is the last challenge remaining in the optimization process. The optical issues were recently solved by the application of highly and selectively reflective coatings on Ti implants. This work focuses on the mechanical durability of these esthetic ceramic based coating systems (with and without adhesion layers). The coating systems (Ti-ZrO2, Ti-Al-ZrO2, Ti-Ti-Al-ZrO2, Ti-Ag-ZrO2, Ti-Ti-Ag-ZrO2, Ti-Bragg and Ti-TiO2-Bragg) were subjected to nanoindentation experiments and examined using scanning electron microscopy and focused ion beam cross sectional analysis. Three coating systems contained adhesion layers (10nm of Ti or 60nm of TiO2 layers). The fracture toughness of selected samples was assessed applying two different models from literature, a classical for bulk materials and an energy-based model, which was further developed and adjusted. The ZrO2 based coating systems (total film thickness<200nm) followed a circumferential cracking behavior in contrast to Bragg coated samples (total film thickness around 1.5μm), which showed radial cracking emanating from the indent corners. For Ti-ZrO2 samples, a fracture toughness between 2.70 and 3.70MPam(1/2) was calculated using an energy-based model. The classical model was applied to Bragg coated samples and their fracture toughness ranged between 0.70 and 0.80MPam(1/2). Furthermore, coating systems containing an additional layer (Ti-Ti-Al-ZrO2, Ti-Ti-Ag-ZrO2 and Ti-TiO2-Bragg) showed an improved adhesion between the substrate and the coating. The addition of a Ti or TiO2 layer improved the adhesion between substrate and coating. The validity of the models for the assessment of the fracture toughness depended on the layer structure and fracture profile of the samples investigated here (classical model for thick coatings and energy-based model for thin coatings).

  17. Determination of elastoplastic mechanical properties of the weld and heat affected zone metals in tailor-welded blanks by nanoindentation test

    NASA Astrophysics Data System (ADS)

    Ma, Xiangdong; Guan, Yingping; Yang, Liu

    2015-09-01

    The elastoplastic mechanical properties of the weld and heat affected zone metals have comparatively major impact on the forming process of tailor-welded blanks. A few scholars investigated the elastoplastic mechanical properties of the weld and heat affected zone, but they only simply assumed that it was a uniform distribution elastoplastic material different from the base materials. Four types of tailor-welded blanks which consist of ST12 and 304 stainless steel plates are selected as the research objects, the elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals are obtained based on the nanoindentation tests, and the Erichsen cupping tests are conducted by combining numerical simulation with physical experiment. The nanoindentation tests results demonstrate that the elastoplastic mechanical properties of the weld and heat affected zone metals are not only different from the base materials, but also varying between the weld metals and the heat affected zone metals. Comparing the Erichsen cupping test resulted from numerical with that from experimental method, it is found that the numerical value of Erichsen cupping test which consider the elastoplastic mechanical properties of the weld and heat affected zone metals have a good agreement with the experimental result, and the relative error is only 4.8%. The proposed research provides good solutions for the inhomogeneous elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals, and improves the control performance of tailor-welded blanks forming accuracy.

  18. Optimization of phase contrast in bimodal amplitude modulation AFM.

    PubMed

    Damircheli, Mehrnoosh; Payam, Amir F; Garcia, Ricardo

    2015-01-01

    Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes.

  19. AFM of biological complexes: what can we learn?

    PubMed Central

    Gaczynska, Maria; Osmulski, Pawel A.

    2009-01-01

    The term “biological complexes” broadly encompasses particles as diverse as multisubunit enzymes, viral capsids, transport cages, molecular nets, ribosomes, nucleosomes, biological membrane components and amyloids. The complexes represent a broad range of stability and composition. Atomic force microscopy offers a wealth of structural and functional data about such assemblies. For this review, we choose to comment on the significance of AFM to study various aspects of biology of selected nonmembrane protein assemblies. Such particles are large enough to reveal many structural details under the AFM probe. Importantly, the specific advantages of the method allow for gathering dynamic information about their formation, stability or allosteric structural changes critical for their function. Some of them have already found their way to nanomedical or nanotechnological applications. Here we present examples of studies where the AFM provided pioneering information about the biology of complexes, and examples of studies where the simplicity of the method is used toward the development of potential diagnostic applications. PMID:19802337

  20. Optimization of phase contrast in bimodal amplitude modulation AFM

    PubMed Central

    Damircheli, Mehrnoosh; Payam, Amir F

    2015-01-01

    Summary Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes. PMID:26114079

  1. Mounting of Escherichia coli spheroplasts for AFM imaging.

    SciTech Connect

    Sullivan, Claretta J; Morrell-Falvey, Jennifer L; Allison, David P; Doktycz, Mitchel John

    2005-11-01

    The cytoplasmic membrane of Escherichia coli (E. coli) is the location of numerous, chemically specific transporters and recognition elements. Investigation of this membrane in vivo by atomic force microscopy (AFM) requires removal of the cell wall and stable immobilization of the spheroplast. AFM images demonstrate that spheroplasts can be secured with warm gelatin applied to the mica substrate just before the addition of a spheroplast suspension. The resulting preparation can be repeatedly imaged by AFM over the course of several hours. Confocal fluorescence imaging confirms the association of the spheroplasts with the gelatin layer. Gelatin molecules are known to reorder into a network after heating. Entrapment within this gelatin network is believed to be responsible for the immobilization of spheroplasts on mica.

  2. Brain Tumor Classification Using AFM in Combination with Data Mining Techniques

    PubMed Central

    Huml, Marlene; Silye, René; Zauner, Gerald

    2013-01-01

    Although classification of astrocytic tumors is standardized by the WHO grading system, which is mainly based on microscopy-derived, histomorphological features, there is great interobserver variability. The main causes are thought to be the complexity of morphological details varying from tumor to tumor and from patient to patient, variations in the technical histopathological procedures like staining protocols, and finally the individual experience of the diagnosing pathologist. Thus, to raise astrocytoma grading to a more objective standard, this paper proposes a methodology based on atomic force microscopy (AFM) derived images made from histopathological samples in combination with data mining techniques. By comparing AFM images with corresponding light microscopy images of the same area, the progressive formation of cavities due to cell necrosis was identified as a typical morphological marker for a computer-assisted analysis. Using genetic programming as a tool for feature analysis, a best model was created that achieved 94.74% classification accuracy in distinguishing grade II tumors from grade IV ones. While utilizing modern image analysis techniques, AFM may become an important tool in astrocytic tumor diagnosis. By this way patients suffering from grade II tumors are identified unambiguously, having a less risk for malignant transformation. They would benefit from early adjuvant therapies. PMID:24062997

  3. Fabrication of nanochannels with ladder nanostructure at the bottom using AFM nanoscratching method

    PubMed Central

    2014-01-01

    This letter presents a novel atomic force microscopy (AFM)-based nanomanufacturing method combining the tip scanning with the high-precision stage movement to fabricate nanochannels with ladder nanostructure at the bottom by continuous scanning with a fixed scan size. Different structures can be obtained according to the matching relation of the tip feeding velocity and the precision stage moving velocity. This relationship was first studied in detail to achieve nanochannels with different ladder nanostructures at the bottom. Machining experiments were then performed to fabricate nanochannels on an aluminum alloy surface to demonstrate the capability of this AFM-based fabrication method presented in this study. Results show that the feed value and the tip orientation in the removing action play important roles in this method which has a significant effect on the machined surfaces. Finally, the capacity of this method to fabricate a large-scale nanochannel was also demonstrated. This method has the potential to advance the existing AFM tip-based nanomanufacturing technique of the formation these complex structures by increasing the removal speed, simplifying the processing procedure and achieving the large-scale nanofabrication. PMID:24940171

  4. Bacterial adhesion to protein-coated surfaces: An AFM and QCM-D study

    NASA Astrophysics Data System (ADS)

    Strauss, Joshua; Liu, Yatao; Camesano, Terri A.

    2009-09-01

    Bacterial adhesion to biomaterials, mineral surfaces, or other industrial surfaces is strongly controlled by the way bacteria interact with protein layers or organic matter and other biomolecules that coat the materials. Despite this knowledge, many studies of bacterial adhesion are performed under clean conditions, instead of in the presence of proteins or organic molecules. We chose fetal bovine serum (FBS) as a model protein, and prepared FBS films on quartz crystals. The thickness of the FBS layer was characterized using atomic force microscopy (AFM) imaging under liquid and quartz crystal microbalance with dissipation (QCM-D). Next, we characterized how the model biomaterial surface would interact with the nocosomial pathogen Staphylococcus epidermidis. An AFM probe was coated with S. epidermidis cells and used to probe a gold slide that had been coated with FBS or another protein, fibronectin (FN). These experiments show that AFM and QCM-D can be used in complementary ways to study the complex interactions between bacteria, proteins, and surfaces.

  5. A low-cost AFM setup with an interferometer for undergraduates and secondary-school students

    NASA Astrophysics Data System (ADS)

    Bergmann, Antje; Feigl, Daniela; Kuhn, David; Schaupp, Manuel; Quast, Günter; Busch, Kurt; Eichner, Ludwig; Schumacher, Jens

    2013-07-01

    Atomic force microscopy (AFM) is an important tool in nanotechnology. This method makes it possible to observe nanoscopic surfaces beyond the resolution of light microscopy. In order to provide undergraduate and secondary-school students with insights into this world, we have developed a very robust low-cost AFM setup with a Fabry-Perot interferometer as a detecting device. This setup is designed to be operated almost completely manually and its simplicity gives access to a profound understanding of the working principle. Our AFM is operated in a constant height mode, i.e. the topography of the sample surface is represented directly by the deflection of the cantilever. Thus, the measuring procedure can be understood even by secondary-school students; furthermore, it is the method with the lowest cost, totalling not more than 10-15 k Euros. Nevertheless, we are able to examine a large variety of sample topographies such as CD and DVD surfaces, IC structures, blood cells, butterfly wings or moth eyes. Furthermore, force-distance curves can be recorded and the tensile moduli of some materials can be evaluated. We present our setup in detail and describe its working principles. In addition, we show various experiments which have already been performed by students.

  6. Mapping individual cosmid DNAs by direct AFM imaging.

    PubMed

    Allison, D P; Kerper, P S; Doktycz, M J; Thundat, T; Modrich, P; Larimer, F W; Johnson, D K; Hoyt, P R; Mucenski, M L; Warmack, R J

    1997-05-01

    Individual cosmid clones have been restriction mapped by directly imaging, with the atomic force microscope (AFM), a mutant EcoRI endonuclease site-specifically bound to DNA. Images and data are presented that locate six restriction sites, predicted from gel electrophoresis, on a 35-kb cosmid isolated from mouse chromosome 7. Measured distances between endonuclease molecules bound to lambda DNA, when compared to known values, demonstrate the accuracy of AFM mapping to better than 1%. These results may be extended to identify other important site-specific protein-DNA interactions, such as transcription factor and mismatch repair enzyme binding, difficult to resolve by current techniques.

  7. GPIM AF-M315E Propulsion System

    NASA Technical Reports Server (NTRS)

    Spores, Ronald A.; Masse, Robert; Kimbrel, Scott; McLean, Chris

    2014-01-01

    The NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) Technology Demonstration Mission (TDM) will demonstrate an operational AF-M315E green propellant propulsion system. Aerojet-Rocketdyne is responsible for the development of the propulsion system payload. This paper statuses the propulsion system module development, including thruster design and system design; Initial test results for the 1N engineering model thruster are presented. The culmination of this program will be high-performance, green AF-M315E propulsion system technology at TRL 7+, with components demonstrated to TRL 9, ready for direct infusion to a wide range of applications for the space user community.

  8. BOREAS AFM-04 Twin Otter Aircraft Flux Data

    NASA Technical Reports Server (NTRS)

    MacPherson, J. Ian; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Desjardins, Raymond L.; Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-5 team collected and processed data from the numerous radiosonde flights during the project. The goals of the AFM-05 team were to provide large-scale definition of the atmosphere by supplementing the existing AES aerological network, both temporally and spatially. This data set includes basic upper-air parameters collected from the network of upper-air stations during the 1993, 1994, and 1996 field campaigns over the entire study region. The data are contained in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  9. Study of mechanical behavior of AFM silicon tips under mechanical load

    NASA Astrophysics Data System (ADS)

    Kopycinska-Mueller, M.; Gluch, J.; Köhler, B.

    2016-11-01

    In this paper we address critical issues concerning calibration of AFM based methods used for nanoscale mechanical characterization of materials. It has been shown that calibration approaches based on macroscopic models for contact mechanics may yield excellent results in terms of the indentation modulus of the sample, but fail to provide a comprehensive and actual information concerning the tip–sample contact radius or the mechanical properties of the tip. Explanations for the severely reduced indentation modulus of the tip included the inadequacies of the models used for calculations of the tip–sample contact stiffness, discrepancies in the actual and ideal shape of the tip, presence of the amorphous silicon phase within the silicon tip, as well as negligence of the actual size of the stress field created in the tip during elastic interactions. To clarify these issues, we investigated the influence of the mechanical load applied to four AFM silicon tips on their crystalline state by exposing them to systematically increasing loads, evaluating the character of the tip–sample interactions via the load-unload stiffness curves, and assessing the state of the tips from HR-TEM images. The results presented in this paper were obtained in a series of relatively simple and basic atomic force acoustic microscopy (AFAM) experiments. The novel combination of TEM imaging of the AFM tips with the analysis of the load-unload stiffness curves gave us a detailed insight into their mechanical behavior under load conditions. We were able to identify the limits for the elastic interactions, as well as the hallmarks for phase transformation and dislocation formation and movement. The comparison of the physical dimensions of the AFM tips, geometry parameters determined from the values of the contact stiffness, and the information on the crystalline state of the tips allowed us a better understanding of the nanoscale contact.

  10. Functionalized AFM probes for force spectroscopy: eigenmode shapes and stiffness calibration through thermal noise measurements.

    PubMed

    Laurent, Justine; Steinberger, Audrey; Bellon, Ludovic

    2013-06-01

    The functionalization of an atomic force microscope (AFM) cantilever with a colloidal bead is a widely used technique when the geometry between the probe and the sample must be controlled, particularly in force spectroscopy. But some questions remain: how does a bead glued at the end of a cantilever influence its mechanical response? And more importantly for quantitative measurements, can we still determine the stiffness of the AFM probe with traditional techniques?In this paper, the influence of the colloidal mass loading on the eigenmode shape and resonant frequency is investigated by measuring the thermal noise on rectangular AFM microcantilevers with and without beads attached at their extremities. The experiments are performed with a home-made ultra-sensitive AFM, based on differential interferometry. The focused beam from the interferometer probes the cantilever at different positions and the spatial shapes of the modes are determined up to the fifth resonance, without external excitation. The results clearly demonstrate that the first eigenmode is almost unchanged by mass loading. However the oscillation behavior of higher resonances presents a marked difference: with a particle glued at its extremity, the nodes of the modes are displaced towards the free end of the cantilever. These results are compared to an analytical model taking into account the mass and inertial moment of the load in an Euler-Bernoulli framework, where the normalization of the eigenmodes is explicitly worked out in order to allow a quantitative prediction of the thermal noise amplitude of each mode. A good agreement between the experimental results and the analytical model is demonstrated, allowing a clean calibration of the probe stiffness.

  11. New developments at PTB in 3D-AFM with tapping and torsion AFM mode and vector approach probing strategy

    NASA Astrophysics Data System (ADS)

    Dai, G.; Hässler-Grohne, W.; Hüser, D.; Wolff, H.; Fluegge, J.; Bosse, H.

    2011-06-01

    A new 3D-AFM for true 3D measurements of nano structures has been developed at Physikalisch Technische-Bundesanstalt, the national metrology institute of Germany. In its configuration, two piezo actuators are applied to drive the AFM cantilever near its vertical and torsional resonant frequencies. In such a way, the AFM tip can probe the surface with a vertical and/or a lateral oscillation, offering high 3D probing sensitivity. For enhancing measurement flexibility as well as reducing tip wear, a so called "vector approach probing" (VAP) method has been applied. The sample is measured point by point using this method. At each probing point, the tip is approached towards the surface in its normal direction until the desired tip-sample interaction is detected and then immediately withdrawn from the surface. Preliminary experimental results show promising performance of the developed system. The measurement of a line structure of 800 nm height employing a super sharp AFM tip is performed, showing a repeatability of its 3D profiles of better than 1 nm (p-v). A single crystal critical dimension reference material (SCCDRM) having features with almost vertical sidewall is measured using a flared AFM tip. Results show that the feature has averaged left and right sidewall angles of 88.64° and 88.67deg;, respectively. However, the feature width non-uniformity may reach 10 nm within the measurement range of 1 μm. The standard deviation of the averaged middle CD values of 7 repeated measurements reaches 0.35 nm. In addition, an investigation of long term measurement stability is performed on a PTB photomask. The results shows that the 3D-AFM has a drift rate of about 0.00033 nm per line, which confirms the high measurement stability and the very low tip wear.

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

    PubMed

    Kreplak, Laurent

    2016-01-01

    The atomic force microscope (AFM) has the unique capability of imaging biological samples with molecular resolution in buffer solution over a wide range of time scales from milliseconds to hours. In addition to providing topographical images of surfaces with nanometer- to angstrom-scale resolution, forces between single molecules and mechanical properties of biological samples can be investigated from the nano-scale to the micro-scale. Importantly, the measurements are made in buffer solutions, allowing biological samples to "stay alive" within a physiological-like environment while temporal changes in structure are measured-e.g., before and after addition of chemical reagents. These qualities distinguish AFM from conventional imaging techniques of comparable resolution, e.g., electron microscopy (EM). This unit provides an introduction to AFM on biological systems and describes specific examples of AFM on proteins, cells, and tissues. The physical principles of the technique and methodological aspects of its practical use and applications are also described. © 2016 by John Wiley & Sons, Inc. PMID:27479503

  13. AFM Structural Characterization of Drinking Water Biofilm under Physiological Conditions

    EPA Science Inventory

    Due to the complexity of mixed culture drinking water biofilm, direct visual observation under in situ conditions has been challenging. In this study, atomic force microscopy (AFM) revealed the three dimensional morphology and arrangement of drinking water relevant biofilm in air...

  14. 3D Color Digital Elevation Map of AFM Sample

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This color image is a three dimensional (3D) view of a digital elevation map of a sample collected by NASA's Phoenix Mars Lander's Atomic Force Microscope (AFM).

    The image shows four round pits, only 5 microns in depth, that were micromachined into the silicon substrate, which is the background plane shown in red. This image has been processed to reflect the levelness of the 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 particle was part of a sample informally called 'Sorceress' delivered to the AFM on the 38th Martian day, or sol, of the mission (July 2, 2008). The AFM is part of Phoenix's microscopic station called MECA, or the Microscopy, Electrochemistry, and Conductivity Analyzer.

    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.

  15. Nanoindentation studies of full and empty viral capsids and the effects of capsid protein mutations on elasticity and strength

    NASA Astrophysics Data System (ADS)

    Michel, J. P.; Ivanovska, I. L.; Gibbons, M. M.; Klug, W. S.; Knobler, C. M.; Wuite, G. J. L.; Schmidt, C. F.

    2006-04-01

    The elastic properties of capsids of the cowpea chlorotic mottle virus have been examined at pH 4.8 by nanoindentation measurements with an atomic force microscope. Studies have been carried out on WT capsids, both empty and containing the RNA genome, and on full capsids of a salt-stable mutant and empty capsids of the subE mutant. Full capsids resisted indentation more than empty capsids, but all of the capsids were highly elastic. There was an initial reversible linear regime that persisted up to indentations varying between 20% and 30% of the diameter and applied forces of 0.6-1.0 nN; it was followed by a steep drop in force that is associated with irreversible deformation. A single point mutation in the capsid protein increased the capsid stiffness. The experiments are compared with calculations by finite element analysis of the deformation of a homogeneous elastic thick shell. These calculations capture the features of the reversible indentation region and allow Young's moduli and relative strengths to be estimated for the empty capsids. atomic force microscopy | cowpea chlorotic mottle virus | finite element analysis | biomechanics

  16. Scanning hall probe microscopy (SHPM) using quartz crystal AFM feedback.

    PubMed

    Dede, M; Urkmen, K; Girişen, O; Atabak, M; Oral, A; Farrer, I; Ritchie, D

    2008-02-01

    Scanning Hall Probe Microscopy (SHPM) is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of approximately 50 nm and 7 mG/Hz(1/2) at room temperature. In the SHPM technique, scanning tunneling microscope (STM) or atomic force microscope (AFM) feedback is used to keep the Hall sensor in close proximity of the sample surface. However, STM tracking SHPM requires conductive samples; therefore the insulating substrates have to be coated with a thin layer of gold. This constraint can be eliminated with the AFM feedback using sophisticated Hall probes that are integrated with AFM cantilevers. However it is very difficult to micro fabricate these sensors. In this work, we have eliminated the difficulty in the cantilever-Hall probe integration process, just by gluing a Hall Probe chip to a quartz crystal tuning fork force sensor. The Hall sensor chip is simply glued at the end of a 32.768 kHz or 100 kHz Quartz crystal, which is used as force sensor. An LT-SHPM system is used to scan the samples. The sensor assembly is dithered at the resonance frequency using a digital Phase Locked Loop circuit and frequency shifts are used for AFM tracking. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. Magnetic domains and topography of an Iron Garnet thin film crystal, NdFeB demagnetised magnet and hard disk samples are presented at room temperature. The performance is found to be comparable with the SHPM using STM feedback.

  17. High-speed AFM for Studying Dynamic Biomolecular Processes

    NASA Astrophysics Data System (ADS)

    Ando, Toshio

    2008-03-01

    Biological molecules show their vital activities only in aqueous solutions. It had been one of dreams in biological sciences to directly observe biological macromolecules (protein, DNA) at work under a physiological condition because such observation is straightforward to understanding their dynamic behaviors and functional mechanisms. Optical microscopy has no sufficient spatial resolution and electron microscopy is not applicable to in-liquid samples. Atomic force microscopy (AFM) can visualize molecules in liquids at high resolution but its imaging rate was too low to capture dynamic biological processes. This slow imaging rate is because AFM employs mechanical probes (cantilevers) and mechanical scanners to detect the sample height at each pixel. It is quite difficult to quickly move a mechanical device of macroscopic size with sub-nanometer accuracy without producing unwanted vibrations. It is also difficult to maintain the delicate contact between a probe tip and fragile samples. Two key techniques are required to realize high-speed AFM for biological research; fast feedback control to maintain a weak tip-sample interaction force and a technique to suppress mechanical vibrations of the scanner. Various efforts have been carried out in the past decade to materialize high-speed AFM. The current high-speed AFM can capture images on video at 30-60 frames/s for a scan range of 250nm and 100 scan lines, without significantly disturbing week biomolecular interaction. Our recent studies demonstrated that this new microscope can reveal biomolecular processes such as myosin V walking along actin tracks and association/dissociation dynamics of chaperonin GroEL-GroES that occurs in a negatively cooperative manner. The capacity of nanometer-scale visualization of dynamic processes in liquids will innovate on biological research. In addition, it will open a new way to study dynamic chemical/physical processes of various phenomena that occur at the liquid-solid interfaces.

  18. In situ Stiffness Adjustment of AFM Probes by Two Orders of Magnitude

    PubMed Central

    de Laat, Marcel Lambertus Cornelis; Pérez Garza, Héctor Hugo; Ghatkesar, Murali Krishna

    2016-01-01

    The choice on which type of cantilever to use for Atomic Force Microscopy (AFM) depends on the type of the experiment being done. Typically, the cantilever has to be exchanged when a different stiffness is required and the entire alignment has to be repeated. In the present work, a method to adjust the stiffness in situ of a commercial AFM cantilever is developed. The adjustment is achieved by changing the effective length of the cantilever by electrostatic pull-in. By applying a voltage between the cantilever and an electrode (with an insulating layer at the point of contact), the cantilever snaps to the electrode, reducing the cantilever’s effective length. An analytical model was developed to find the pull-in voltage of the system. Subsequently, a finite element model was developed to study the pull-in behavior. The working principle of this concept is demonstrated with a proof-of-concept experiment. The electrode was positioned close to the cantilever by using a robotic nanomanipulator. To confirm the change in stiffness, the fundamental resonance frequency of the cantilever was measured for varying electrode positions. The results match with the theoretical expectations. The stiffness was adjusted in situ in the range of 0.2 N/m to 27 N/m, covering two orders of magnitude in one single cantilever. This proof-of-concept is the first step towards a micro fabricated prototype, that integrates the electrode positioning system and cantilever that can be used for actual AFM experiments. PMID:27077863

  19. Oxide nanocrystal based nanocomposites for fabricating photoplastic AFM probes

    NASA Astrophysics Data System (ADS)

    Ingrosso, Chiara; Martin-Olmos, Cristina; Llobera, Andreu; Innocenti, Claudia; Sangregorio, Claudio; Striccoli, Marinella; Agostiano, Angela; Voigt, Anja; Gruetzner, Gabi; Brugger, Jürgen; Perez-Murano, Francesc; Curri, Maria Lucia

    2011-11-01

    We report on the synthesis, characterization and application of a novel nanocomposite made of a negative tone epoxy based photoresist modified with organic-capped Fe2O3 nanocrystals (NCs). The mechanical properties of the nanocomposite drastically improve upon incorporation of a suitable concentration of NCs in the polymer, without deteriorating its photolithography performance. High aspect ratio 3D microstructures made of the nanocomposite have been fabricated with a uniform surface morphology and with a resolution down to few micrometres. The embedded organic-capped Fe2O3 NCs drastically increase the stiffness and hardness of the epoxy based photoresist matrix, making the final material extremely interesting for manufacturing miniaturized polymer based mechanical devices and systems. In particular, the nanocomposite has been used as structural material for fabricating photoplastic Atomic Force Microscopy (AFM) probes with integrated tips showing outstanding mechanical response and high resolution imaging performance. The fabricated probes consist of straight cantilevers with low stress-gradient and high quality factors, incorporating sharp polymeric tips. They present considerably improved performance compared to pure epoxy based photoresist AFM probes, and to commercial silicon AFM probes.We report on the synthesis, characterization and application of a novel nanocomposite made of a negative tone epoxy based photoresist modified with organic-capped Fe2O3 nanocrystals (NCs). The mechanical properties of the nanocomposite drastically improve upon incorporation of a suitable concentration of NCs in the polymer, without deteriorating its photolithography performance. High aspect ratio 3D microstructures made of the nanocomposite have been fabricated with a uniform surface morphology and with a resolution down to few micrometres. The embedded organic-capped Fe2O3 NCs drastically increase the stiffness and hardness of the epoxy based photoresist matrix, making the

  20. A Nano-indentation Identification Technique for Viscoelastic Constitutive Characteristics of Periodontal Ligaments

    PubMed Central

    Ashrafi, H.; Shariyat, M.

    2016-01-01

    Introduction Nano-indentation has recently been employed as a powerful tool for determining the mechanical properties of biological tissues on nano and micro scales. A majority of soft biological tissues such as ligaments and tendons exhibit viscoelastic or time-dependent behaviors. The constitutive characterization of soft tissues is among very important subjects in clinical medicine and especially, biomechanics fields. Periodontal ligament plays an important role in initiating tooth movement when loads are applied to teeth with orthodontic appliances. It is also the most accessible ligament in human body as it can be directly manipulated without any surgical intervention. From a mechanical point of view, this ligament can be considered as a thin interface made by a solid phase, consisting mainly of collagen fibers, which is immersed into a so-called ground substance. However, the viscoelastic constitutive effects of biological tissues are seldom considered rigorous during Nano-indentation tests. Methods In the present paper, a mathematical contact approach is developed to enable determining creep compliance and relaxation modulus of distinct periodontal ligaments, using constant–rate indentation and loading time histories, respectively. An adequate curve-fitting method is presented to determine these characteristics based on the Nano-indentation of rigid Berkovich tips. Generalized Voigt-Kelvin and Wiechert models are used to model constitutive equations of periodontal ligaments, in which the relaxation and creep functions are represented by series of decaying exponential functions of time. Results Time-dependent creep compliance and relaxation function have been obtained for tissue specimens of periodontal ligaments. Conclusion To improve accuracy, relaxation and creep moduli are measured from two tests separately. Stress relaxation effects appear more rapidly than creep in the periodontal ligaments.

  1. Plastic deformation behaviors of Ni- and Zr-based bulk metallic glasses subjected to nanoindentation

    SciTech Connect

    Weizhong, Liang; Zhiliang, Ning; Zhenqian, Dang; Linzhi, Wu

    2013-12-15

    Plastic deformation behaviors of Ni{sub 42}Ti{sub 20}Zr{sub 21.5}Al{sub 8}Cu{sub 5}Si{sub 3.5} and Zr{sub 51}Ti{sub 5}Ni{sub 10}Cu{sub 25}Al{sub 9} bulk metallic glasses at room temperature were studied by nanoindentation testing and atomic force microscopy under equivalent indentation experimental conditions. The different chemical composition of these two bulk metallic glasses produced variant tendencies for displacement serrated flow to occur during the loading process. The nanoindentation strain rate was calculated as a function of indentation displacement in order to verify the occurrence of displacement serrated flow at different loading rates. Atomic force microscopy revealed decreasing numbers of discrete shear bands around the indentation sites as loading rates increased from 0.025 to 2.5 mNs{sup −1}. Variations in plastic deformation behaviors between Ni and Zr-based glasses materials can be explained by the different metastable microstructures and thermal stabilities of the two materials. The mechanism governing plastic deformation of these metallic glasses was analyzed in terms of an established model of the shear transformation zone. - Highlights: • Plastic deformation of Ni- and Zr-based BMG is studied under identical conditions • Zr-based BMG undergoes a greater extent of plastic deformation than Ni-based BMG • Nanoindentation strain rate is studied to clarify variation in plastic deformation • Metastable microstructure, thermal stability affect BMG plastic deformation.

  2. A Nano-indentation Identification Technique for Viscoelastic Constitutive Characteristics of Periodontal Ligaments

    PubMed Central

    Ashrafi, H.; Shariyat, M.

    2016-01-01

    Introduction Nano-indentation has recently been employed as a powerful tool for determining the mechanical properties of biological tissues on nano and micro scales. A majority of soft biological tissues such as ligaments and tendons exhibit viscoelastic or time-dependent behaviors. The constitutive characterization of soft tissues is among very important subjects in clinical medicine and especially, biomechanics fields. Periodontal ligament plays an important role in initiating tooth movement when loads are applied to teeth with orthodontic appliances. It is also the most accessible ligament in human body as it can be directly manipulated without any surgical intervention. From a mechanical point of view, this ligament can be considered as a thin interface made by a solid phase, consisting mainly of collagen fibers, which is immersed into a so-called ground substance. However, the viscoelastic constitutive effects of biological tissues are seldom considered rigorous during Nano-indentation tests. Methods In the present paper, a mathematical contact approach is developed to enable determining creep compliance and relaxation modulus of distinct periodontal ligaments, using constant–rate indentation and loading time histories, respectively. An adequate curve-fitting method is presented to determine these characteristics based on the Nano-indentation of rigid Berkovich tips. Generalized Voigt-Kelvin and Wiechert models are used to model constitutive equations of periodontal ligaments, in which the relaxation and creep functions are represented by series of decaying exponential functions of time. Results Time-dependent creep compliance and relaxation function have been obtained for tissue specimens of periodontal ligaments. Conclusion To improve accuracy, relaxation and creep moduli are measured from two tests separately. Stress relaxation effects appear more rapidly than creep in the periodontal ligaments. PMID:27672630

  3. Surface Effects on Young's Modulud and Hardness of Fused Silica by Nanoindentation Study

    SciTech Connect

    Zheng, L.; Schmid, A.W.; Lambropoulos, J.C.

    2007-01-24

    The surface Young's modulus (E) and hardness (H) of fused silica samples have been studied by nanoindentation. Two factors strongly affect the results of E and H. One factor is the polishing quality of the fused silica surface. Poor polishing quality produces much smaller E and H than the literature values for bulk fused silica. The second factor is surface flatness. Even for a well-polished silica surface, an "arch bridge effect" may hinder the measurements of the true values of E and H. A correction procedure is proposed to eliminate this effect, and the corrected results show substantial improvements.

  4. Photoinduced stiffening and photoplastic effect of ZnS individual nanobelt in nanoindentation

    SciTech Connect

    Zheng, X. J.; Yu, G. C.; Chen, Y. Q.; Mao, S. X.; Zhang, T.

    2010-11-15

    The photoinduced stiffening (PIS) and photoplastic effect (PPE) of ZnS individual nanobelt (NB) were observed by using a nanoindenter in conjunction with an incident ultraviolet (UV) light source system. The results show that the elastic modulus and hardness of ZnS individual NB under UV illumination are at least 32% and 20% larger than those in darkness. The mechanisms of PIS and PPE are interpreted by the increase in electronic strain and Peierls barrier due to the photogeneration of free carriers in ZnS individual NB. The research may offer useful guidelines to the application of optoelectronic devices based on individual nanostructures.

  5. EBSD and Nanoindentation-Correlated Study of Delamination Fracture in Al-Li Alloy 2090

    NASA Technical Reports Server (NTRS)

    Tayon, Wesley A.; Crooks, Roy E.; Domack, Marcia S.; Wagner, John A.; Elmustafa, A. A.

    2008-01-01

    Al-Li alloys offer attractive combinations of high strength and low density. However, a tendency for delamination fracture has limited their use. A better understanding of the delamination mechanisms may identify methods to control delaminations through processing modifications. A combination of new techniques has been used to evaluate delamination fracture in Al-Li alloys. Both high quality electron backscattered diffraction (EBSD) information and valid nanoindentation measurements were obtained from fractured test specimens. Correlations were drawn between nano-scale hardness variations and local texture along delaminating boundaries. Intriguing findings were observed for delamination fracture through the combined analysis of grain orientation, Taylor factor, and kernel average misorientation.

  6. 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.

  7. Elastic constants determined by nanoindentation for p-type thermoelectric half-Heusler

    SciTech Connect

    Gahlawat, S.; Wheeler, L.; White, K. W. E-mail: kwwhite@uh.edu; He, R.; Chen, S.; Ren, Z. F. E-mail: kwwhite@uh.edu

    2014-08-28

    This paper presents a study of the elastic properties of the p-type thermoelectric half-Heusler material, Hf{sub 0.44}Zr{sub 0.44}Ti{sub 0.12}CoSb{sub 0.8}Sn{sub 0.2}, using nanoindentation. Large grain-sized polycrystalline specimens were fabricated for these measurements, providing sufficient indentation targets within single grains. Electron Backscatter Diffraction methods indexed the target grains for the correlation needed for our elastic analysis of individual single crystals for this cubic thermoelectric material. Elastic properties, including the Zener ratio and the Poisson ratio, obtained from the elasticity tensor are also reported.

  8. 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.

  9. Discrete drops in the electrical contact resistance during nanoindentation of a bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Singh, Gaurav; Narayan, R. L.; Asiri, A. M.; Ramamurty, U.

    2016-05-01

    Simultaneous measurement of the electrical contact resistance (ECR) during nanoindentation of a Pd-based bulk metallic glass (BMG) shows discontinuities in the current during the loading segment. Through an analysis of the effective change in the contact area that occurs due to the plastic flow via shear banding, we show that the current surges, which are synchronous with the displacement bursts, are associated with shear band nucleation and/or propagation. The potential of nano-ECR measurements for monitoring plastic events in BMGs is discussed.

  10. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    NASA Astrophysics Data System (ADS)

    Zhao, Junhua; Jiang, Jin-Wu; Rabczuk, Timon

    2013-12-01

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS2) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS2. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  11. Effect of tip radius on the incipient plasticity of chromium studied by nanoindentation

    DOE PAGES

    Wu, Dong; Morris, James R.; Nieh, T. G.

    2014-10-01

    The onset of plasticity in Cr was investigated by nanoindentation using indenters with tip radii ranging from 60 to 759 nm. The stress for incipient plasticity was found to increase with decreasing tip radius. We find that the cumulative pop-in probability on load could be described successfully by a combined model over the full range of tip radius, indicating that the incipient plasticity might be triggered either by the homogeneous nucleation of dislocation or by the activation of existing dislocations underneath the indenter.

  12. Cell visco-elasticity measured with AFM and optical trapping at sub-micrometer deformations.

    PubMed

    Nawaz, Schanila; Sánchez, Paula; Bodensiek, Kai; Li, Sai; Simons, Mikael; Schaap, Iwan A T

    2012-01-01

    The measurement of the elastic properties of cells is widely used as an indicator for cellular changes during differentiation, upon drug treatment, or resulting from the interaction with the supporting matrix. Elasticity is routinely quantified by indenting the cell with a probe of an AFM while applying nano-Newton forces. Because the resulting deformations are in the micrometer range, the measurements will be affected by the finite thickness of the cell, viscous effects and even cell damage induced by the experiment itself. Here, we have analyzed the response of single 3T3 fibroblasts that were indented with a micrometer-sized bead attached to an AFM cantilever at forces from 30-600 pN, resulting in indentations ranging from 0.2 to 1.2 micrometer. To investigate the cellular response at lower forces up to 10 pN, we developed an optical trap to indent the cell in vertical direction, normal to the plane of the coverslip. Deformations of up to two hundred nanometers achieved at forces of up to 30 pN showed a reversible, thus truly elastic response that was independent on the rate of deformation. We found that at such small deformations, the elastic modulus of 100 Pa is largely determined by the presence of the actin cortex. At higher indentations, viscous effects led to an increase of the apparent elastic modulus. This viscous contribution that followed a weak power law, increased at larger cell indentations. Both AFM and optical trapping indentation experiments give consistent results for the cell elasticity. Optical trapping has the benefit of a lower force noise, which allows a more accurate determination of the absolute indentation. The combination of both techniques allows the investigation of single cells at small and large indentations and enables the separation of their viscous and elastic components. PMID:23028915

  13. The use of nanoindentation for characterizing the properties of mineralized hard tissues: state-of-the art review.

    PubMed

    Lewis, Gladius; Nyman, Jeffry S

    2008-10-01

    The use of nanoindentation to determine nanomechanical properties of mineralized tissues has been investigated extensively. A detailed, critical, and comprehensive review of this literature is the subject of the present work. After stating the motivation for the review, a succinct presentation of the challenges, advantages, and disadvantages of the various quasi-static nanoindentation test methods (to obtain elastic modulus, E, and hardness, H) and dynamic test methods (to obtain storage and loss moduli and/or loss/damping factor) is given in the form of a primer. Explicative summaries of literature reports on various intrinsic and extrinsic factors that significantly influence E and H, followed by 15 suggested topics for future research, are included additionally. This review is designed to present a compact guide to the principles of the nanoindentation technique and to emphasize considerations when determining material properties of mineralized tissues. PMID:18395829

  14. BOREAS AFM-5 Level-1 Upper Air Network Data

    NASA Technical Reports Server (NTRS)

    Barr, Alan; Hrynkiw, Charmaine; Newcomer, Jeffrey A. (Editor); Hall, Forrest G. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-5 team collected and processed data from the numerous radiosonde flights during the project. The goals of the AFM-05 team were to provide large-scale definition of the atmosphere by supplementing the existing Atmospheric Environment Service (AES) aerological network, both temporally and spatially. This data set includes basic upper-air parameters collected from the network of upper-air stations during the 1993, 1994, and 1996 field campaigns over the entire study region. The data are contained in tabular ASCII files. The level-1 upper-air network data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files also are available on a CD-ROM (see document number 20010000884).

  15. Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR.

    PubMed

    Morsch, Suzanne; Liu, Yanwen; Lyon, Stuart B; Gibbon, Simon R

    2016-01-13

    The first direct observation of a chemically heterogeneous nanostructure within an epoxy resin is reported. Epoxy resins comprise the matrix component of many high performance composites, coatings and adhesives, yet the molecular network structure that underpins the performance of these industrially essential materials is not well understood. Internal nodular morphologies have repeatedly been reported for epoxy resins analyzed using SEM or AFM, yet the origin of these features remains a contentious subject, and epoxies are still commonly assumed to be chemically homogeneous. Uniquely, in this contribution we use the recently developed AFM-IR technique to eliminate previous differences in interpretation, and establish that nodule features correspond to heterogeneous network connectivity within an epoxy phenolic formulation.

  16. MDI: integrity index of cytoskeletal fibers observed by AFM

    NASA Astrophysics Data System (ADS)

    Manghi, Massimo; Bruni, Luca; Croci, Simonetta

    2016-06-01

    The Modified Directional Index (MDI) is a form factor of the angular spectrum computed from the 2D Fourier transform of an image marking the prevalence of rectilinear features throughout the picture. We study some properties of the index and we apply it to AFM images of cell cytoskeleton regions featuring patterns of rectilinear nearly parallel actin filaments as in the case of microfilaments grouped in bundles. The analysis of AFM images through MDI calculation quantifies the fiber directionality changes which could be related to fiber damages. This parameter is applied to the images of Hs 578Bst cell line, non-tumoral and not immortalized human epithelial cell line, irradiated with X-rays at doses equivalent to typical radiotherapy treatment fractions. In the reported samples, we could conclude that the damages are mainly born to the membrane and not to the cytoskeleton. It could be interesting to test the parameter also using other kinds of chemical or physical agents.

  17. On CD-AFM bias related to probe bending

    NASA Astrophysics Data System (ADS)

    Ukraintsev, V. A.; Orji, N. G.; Vorburger, T. V.; Dixson, R. G.; Fu, J.; Silver, R. M.

    2012-03-01

    Critical Dimension AFM (CD-AFM) is a widely used reference metrology. To characterize modern semiconductor devices, very small and flexible probes, often 15 nm to 20 nm in diameter, are now frequently used. Several recent publications have reported on uncontrolled and significant probe-to-probe bias variation during linewidth and sidewall angle measurements [1,2]. Results obtained in this work suggest that probe bending can be on the order of several nanometers and thus potentially can explain much of the observed CD-AFM probe-to-probe bias variation. We have developed and experimentally tested one-dimensional (1D) and two-dimensional (2D) models to describe the bending of cylindrical probes. An earlier 1D bending model reported by Watanabe et al. [3] was refined. Contributions from several new phenomena were considered, including: probe misalignment, diameter variation near the carbon nanotube tip (CNT) apex, probe bending before snapping, distributed van der Waals-London force, etc. The methodology for extraction of the Hamaker probe-surface interaction energy from experimental probe bending data was developed. To overcome limitations of the 1D model, a new 2D distributed force (DF) model was developed. Comparison of the new model with the 1D single point force (SPF) model revealed about 27 % difference in probe bending bias between the two. A simple linear relation between biases predicted by the 1D SPF and 2D DF models was found. This finding simplifies use of the advanced 2D DF model of probe bending in various CD-AFM applications. New 2D and three-dimensional (3D) CDAFM data analysis software is needed to take full advantage of the new bias correction modeling capabilities.

  18. Nanoscale fabrication of a peptide layer using an AFM probe

    NASA Astrophysics Data System (ADS)

    Nakamura, Chikashi; Miyamoto, Chie; Obataya, Ikuo; Nakamura, Noriyuki; Miyake, Jun

    2004-12-01

    Scanning probe microscopy has been applied in many studies to manipulate atoms or molecules. In particular, force spectroscopy using an atomic force microscope (AFM) is a powerful tool to elucidate intermolecular or intramolecular interactions and provide mechanical information. If enzymes could retain their activity when immobilized on probes, not only could enzyme-substrate interactions be investigated but also the probes could be used for precise biomolecular manipulation at the nano-scale. In our study, a method based on "Enzymatic Nanolithography" was successfully performed in a buffered solution using Staphylococcal serine V8 protease and AFM. To estimate the fabricating activity of the protease immobilized on the AFM tip to peptides immobilized on a substrate, we designed and synthesized peptides that showed enzymatic action specific to the protease. When the protease digested the reporter peptide a quencher residue was released from the main flame of the peptide and resulted in fluorescence. In the designed 9 mer peptides, TAMRA functioned as a good quencher for FAM. After contact of the protease-immobilized tip to the reporter peptide layer, a fluorescent area was observed by microscopic imaging.

  19. Confocal Raman-AFM, A New Tool for Materials Research

    NASA Astrophysics Data System (ADS)

    Schmidt, Ute

    2005-03-01

    Characterization of heterogeneous systems, e.g. polymers, on the nanometer scale continues to grow in importance and to impact key applications in the field of materials science, nanotechnology and catalysis. The development of advanced polymeric materials for such applications requires detailed information about the physical and chemical properties of these materials on the nanometer scale. However, some details about the phase-separation process in polymers are difficult to study with conventional characterization techniques due to the inability of these methods to chemically differentiate materials with good spatial resolution, without damage, staining or preferential solvent washing. The CR-AFM is a breakthrough in microscopy. It combines three measuring techniques in one instrument: a high resolution confocal optical microscope, an extremely sensitive Raman spectroscopy system, and an Atomic Force Microscope. Using this instrument, the high spatial and topographical resolution obtained with an AFM can be directly linked to the chemical information gained by Confocal Raman spectroscopy. To demonstrate the capabilities of this unique combination of measuring techniques, polymer blend films, spin coated on glass substrates, have been characterized. AFM measurements reveal the structural and mechanical properties of the films, whereas Raman spectral images show the chemical composition of the blends.

  20. In situ hydrodynamic lateral force calibration of AFM colloidal probes.

    PubMed

    Ryu, Sangjin; Franck, Christian

    2011-11-01

    Lateral force microscopy (LFM) is an application of atomic force microscopy (AFM) to sense lateral forces applied to the AFM probe tip. Recent advances in tissue engineering and functional biomaterials have shown a need for the surface characterization of their material and biochemical properties under the application of lateral forces. LFM equipped with colloidal probes of well-defined tip geometries has been a natural fit to address these needs but has remained limited to provide primarily qualitative results. For quantitative measurements, LFM requires the successful determination of the lateral force or torque conversion factor of the probe. Usually, force calibration results obtained in air are used for force measurements in liquids, but refractive index differences between air and liquids induce changes in the conversion factor. Furthermore, in the case of biochemically functionalized tips, damage can occur during calibration because tip-surface contact is inevitable in most calibration methods. Therefore, a nondestructive in situ lateral force calibration is desirable for LFM applications in liquids. Here we present an in situ hydrodynamic lateral force calibration method for AFM colloidal probes. In this method, the laterally scanned substrate surface generated a creeping Couette flow, which deformed the probe under torsion. The spherical geometry of the tip enabled the calculation of tip drag forces, and the lateral torque conversion factor was calibrated from the lateral voltage change and estimated torque. Comparisons with lateral force calibrations performed in air show that the hydrodynamic lateral force calibration method enables quantitative lateral force measurements in liquid using colloidal probes.

  1. Near-Field Spectroscopy with Nanoparticles Deposited by AFM

    NASA Technical Reports Server (NTRS)

    Anderson, Mark S.

    2008-01-01

    An alternative approach to apertureless near-field optical spectroscopy involving an atomic-force microscope (AFM) entails less complexity of equipment than does a prior approach. The alternative approach has been demonstrated to be applicable to apertureless near-field optical spectroscopy of the type using an AFM and surface enhanced Raman scattering (SERS), and is expected to be equally applicable in cases in which infrared or fluorescence spectroscopy is used. Apertureless near-field optical spectroscopy is a means of performing spatially resolved analyses of chemical compositions of surface regions of nanostructured materials. In apertureless near-field spectroscopy, it is common practice to utilize nanostructured probe tips or nanoparticles (usually of gold) having shapes and dimensions chosen to exploit plasmon resonances so as to increase spectroscopic-signal strengths. To implement the particular prior approach to which the present approach is an alternative, it is necessary to integrate a Raman spectrometer with an AFM and to utilize a special SERS-active probe tip. The resulting instrumentation system is complex, and the tasks of designing and constructing the system and using the system to acquire spectro-chemical information from nanometer-scale regions on a surface are correspondingly demanding.

  2. Nanoscale rippling on polymer surfaces induced by AFM manipulation

    PubMed Central

    2015-01-01

    Summary Nanoscale rippling induced by an atomic force microscope (AFM) tip can be observed after performing one or many scans over the same area on a range of materials, namely ionic salts, metals, and semiconductors. However, it is for the case of polymer films that this phenomenon has been widely explored and studied. Due to the possibility of varying and controlling various parameters, this phenomenon has recently gained a great interest for some technological applications. The advent of AFM cantilevers with integrated heaters has promoted further advances in the field. An alternative method to heating up the tip is based on solvent-assisted viscoplastic deformations, where the ripples develop upon the application of a relatively low force to a solvent-rich film. An ensemble of AFM-based procedures can thus produce nanoripples on polymeric surfaces quickly, efficiently, and with an unprecedented order and control. However, even if nanorippling has been observed in various distinct modes and many theoretical models have been since proposed, a full understanding of this phenomenon is still far from being achieved. This review aims at summarizing the current state of the art in the perspective of achieving control over the rippling process on polymers at a nanoscale level. PMID:26733086

  3. Nanoindentation testing and finite element simulations of cortical bone allowing for anisotropic elastic and inelastic mechanical response.

    PubMed

    Carnelli, Davide; Lucchini, Riccardo; Ponzoni, Matteo; Contro, Roberto; Vena, Pasquale

    2011-07-01

    Anisotropy is one of the most peculiar aspects of cortical bone mechanical behaviour, and the numerical approach can be successfully used to investigate aspects of bone tissue mechanics that analytical methods solve in approximate way or do not cover. In this work, nanoindentation experimental tests and finite element simulations were employed to investigate the elastic-inelastic anisotropic mechanical properties of cortical bone. The model allows for anisotropic elastic and post-yield behaviour of the tissue. A tension-compression mismatch and direction-dependent yield stresses are allowed for. Indentation experiments along the axial and transverse directions were simulated with the purpose to predict the indentation moduli and hardnesses along multiple orientations. Results showed that the experimental transverse-to-axial ratio of indentation moduli, equal to 0.74, is predicted with a ∼3% discrepancy regardless the post-yield material behaviour; whereas, the transverse-to-axial hardness ratio, equal to 0.86, can be correctly simulated (discrepancy ∼6% w.r.t. the experimental results) only employing an anisotropic post-elastic constitutive model. Further, direct comparison between the experimental and simulated indentation tests evidenced a good agreement in the loading branch of the indentation curves and in the peak loads for a transverse-to-axial yield stress ratio comparable to the experimentally obtained transverse-to-axial hardness ratio. In perspective, the present work results strongly support the coupling between indentation experiments and FEM simulations to get a deeper knowledge of bone tissue mechanical behaviour at the microstructural level. The present model could be used to assess the effect of variations of constitutive parameters due to age, injury, and/or disease on bone mechanical performance in the context of indentation testing. PMID:21570077

  4. Nano-indentation on amorphous calcium phosphate splats: effect of droplet size on mechanical properties.

    PubMed

    Saber-Samandari, Saeed; Gross, Karlis A

    2012-12-01

    Droplet processing technologies and many biological processes use disk-like or hemispherical shapes for construction or the design of surfaces. The ability to tune the characteristics and properties of a surface is important at the micro- and nano-scale. The influence of size on the mechanical properties is presently unknown. This work set out to produce splats from different droplet sizes (20-40 μm, 40-60 μm and 60-80 μm), and then determine the deposit characteristics and mechanical properties. All splats produced by melting particles in a flame and depositing onto a polished titanium surface were amorphous, as determined by Raman micro-spectrometry. The topography shown in an optical and scanning electron microscope and topographically mapped using the scanning mode of the nano-indenter revealed a flattened hemispherical deposit. The critical nano-indentation load for determining the true hardness decreased with increasing splat size; for 20-40 μm, 40-60 μm and 60-80 μm splats the critical load was 19, 16, 11 mN respectively compared to 30 mN for sintered hydroxyapatite. Higher loads are required to cause cracking and delamination in smaller splats. A load between 40 and 60 mN was required for delamination of the splat. Delamination of the splats could offer a new means to determine the adhesion of splats on low roughness surfaces. PMID:23137620

  5. The mechanical anisotropy on a longitudinal section of human enamel studied by nanoindentation.

    PubMed

    Cheng, Zhen-jiang; Wang, Xiu-mei; Ge, Jun; Yan, Jian-xin; Ji, Ning; Tian, Li-li; Cui, Fu-zhai

    2010-06-01

    Nanoindentation has been widely used for probing the mechanical properties of tooth, especially for characterizing its complex hierarchical structures. Previous studies have confirmed the anisotropic mechanical behaviors caused by the alternated orientations of enamel rods and the alignment of fibril-like hydroxyapatite crystals, but the longitudinal section of enamel, which was composed of parallel-arranged rods, was regarded as a homogeneous continuum as always. In this study, nanoindentation combined with SEM was carried out with the indenter rotating on the longitudinal section of enamel to evaluate the relativity between the nano-mechanical properties and the orientation of indentation impressions. It has been shown that the enamel presented different elastic modulus and hardness with different angles of indenter on its longitudinal section, and its anisotropy was also confirmed by the remarkable asymmetric morphologies of impressions. We observed that the parallel arrangement of crystal fibrils and enamel rods might trigger the expansion of the micro-cracks in preferred orientation, and result in scalene triangle indentation impressions, altering contact areas as well as inconsistent mechanical behaviors. Consequently, it is considered that the longitudinal sections of enamel should be modeled as anisotropic.

  6. Recent advances in small-scale mechanical property measurement by nanoindentation

    DOE PAGES

    Pharr, George Mathews

    2015-08-25

    Since its initial development in the early 1980’s [1], nanoindentation has matured into one of the premier testing techniques for measuring mechanical properties at the micrometer and sub-micrometer scales and has emerged as a critical tool that has helped to shape the nanotechnology revolution. At the heart of the technique are testing systems with simple but precise force actuators and displacement measuring devices that record the force–displacement record as a diamond indenter, usually the form of a pyramid or a sphere, is pressed into and withdrawn from a small region in the surface of a material of interest. The nano-scalemore » force–displacement data, which can be obtained with a spatial resolution as small as a few nanometers, contains a wealth of information about the local mechanical properties [2], [3] and [4]. This enables the mechanical characterization of very thin films, like those used in the semiconductor, magnetic storage, and hard coatings industries, as well as very small precipitates, particles and second phases, many of which may not exist in bulk form and cannot be characterized by traditional mechanical testing methods. Here, computer automation of nanoindentation testing systems now routinely provides for complete two-dimensional mapping of properties over regions stretching from sub-micron to millimeters in scale.« less

  7. Mechanical response of dental cements as determined by nanoindentation and scanning electron microscopy.

    PubMed

    Saghiri, Mohammad Ali; Nazari, Amir; Garcia-Godoy, Franklin; Asatourian, Armen; Malekzadeh, Mansour; Elyasi, Maryam

    2013-12-01

    This study evaluated the effects of nanoindentation on the surface of white mineral trioxide aggregate (WMTA), Bioaggregate and Nano WMTA cements. Cements were mixed according to the manufacturer directions, condensed inside glass tubes, and randomly divided into three groups (n = 8). Specimens were soaked in synthetic tissue fluid (pH = 7.4) and incubated for 3 days. Cement pellets were subjected to nanoindentation tests and observed by scanning electron microscopy. Then, the images were processed and the number of cracks and total surface area of defects on the surface were calculated and analyzed using ImageJ. Data were submitted to one-way analysis of variance and a post hoc Tukey's test. The lowest number of cracks and total surface of defects were detected in Nano WMTA samples; however, it was not significantly different from WMTA samples (p = 0.588), while the highest values were noticed in Bioaggregate specimens that were significantly different from Nano WMTA and WMTA (p = 0.0001). The surface of WMTA and Nano WMTA showed more resistance after exposure to nano-compressive forces which indicated a better surface tolerance against these forces and crack formation. This suggests these substances are more tolerant cement materials which can predictably withstand loaded situations in a clinical scenario.

  8. The evolution of machining-induced surface of single-crystal FCC copper via nanoindentation

    PubMed Central

    2013-01-01

    The physical properties of the machining-induced new surface depend on the performance of the initial defect surface and deformed layer in the subsurface of the bulk material. In this paper, three-dimensional molecular dynamics simulations of nanoindentation are preformed on the single-point diamond turning surface of single-crystal copper comparing with that of pristine single-crystal face-centered cubic copper. The simulation results indicate that the nucleation of dislocations in the nanoindentation test on the machining-induced surface and pristine single-crystal copper is different. The dislocation embryos are gradually developed from the sites of homogeneous random nucleation around the indenter in the pristine single-crystal specimen, while the dislocation embryos derived from the vacancy-related defects are distributed in the damage layer of the subsurface beneath the machining-induced surface. The results show that the hardness of the machining-induced surface is softer than that of pristine single-crystal copper. Then, the nanocutting simulations are performed along different crystal orientations on the same crystal surface. It is shown that the crystal orientation directly influences the dislocation formation and distribution of the machining-induced surface. The crystal orientation of nanocutting is further verified to affect both residual defect generations and their propagation directions which are important in assessing the change of mechanical properties, such as hardness and Young's modulus, after nanocutting process. PMID:23641932

  9. Recent advances in small-scale mechanical property measurement by nanoindentation

    SciTech Connect

    Pharr, George Mathews

    2015-08-25

    Since its initial development in the early 1980’s [1], nanoindentation has matured into one of the premier testing techniques for measuring mechanical properties at the micrometer and sub-micrometer scales and has emerged as a critical tool that has helped to shape the nanotechnology revolution. At the heart of the technique are testing systems with simple but precise force actuators and displacement measuring devices that record the force–displacement record as a diamond indenter, usually the form of a pyramid or a sphere, is pressed into and withdrawn from a small region in the surface of a material of interest. The nano-scale force–displacement data, which can be obtained with a spatial resolution as small as a few nanometers, contains a wealth of information about the local mechanical properties [2], [3] and [4]. This enables the mechanical characterization of very thin films, like those used in the semiconductor, magnetic storage, and hard coatings industries, as well as very small precipitates, particles and second phases, many of which may not exist in bulk form and cannot be characterized by traditional mechanical testing methods. Here, computer automation of nanoindentation testing systems now routinely provides for complete two-dimensional mapping of properties over regions stretching from sub-micron to millimeters in scale.

  10. Measurement of residual stress in quenched 1045 steel by the nanoindentation method

    SciTech Connect

    Zhu Lina; Xu Binshi; Wang Haidou; Wang Chengbiao

    2010-12-15

    In this paper, the residual stress in quenched AISI 1045 steel was measured by a recently developed nanoindentation technique. Depth control mode was adopted to measure the residual stress. It was found that residual compressive stress was generated in the quenched steel. The material around nanoindents exhibits significant pile-up deformation. A new method was proposed to determine the real contact area for pile-up material on the basis of invariant pile-up morphology of the loaded or unloaded states. The results obtained by the new method were in good agreement with the residual stresses measured by the classical X-ray diffraction (XRD) method. - Research Highlights: {yields} A new method was proposed to measure the real contact area for pile-up materials. {yields} The real contact depth is defined as the sum of h{sub max} and the pile-up height h{sub p}. {yields} The value of residual stress measured by the nanoindentation method was in good agreement with that by the XRD method.

  11. Assessment of lamellar level properties in mouse bone utilizing a novel spherical nanoindentation data analysis method

    PubMed Central

    Pathak, Siddhartha; Vachhani, Shraddha J.; Jepsen, Karl J.; Goldman, Haviva M.; Kalidindi, Surya R.

    2016-01-01

    In this work, we demonstrate the viability of using our recently developed data analysis procedures for spherical nanoindentation in conjunction with Raman spectroscopy for studying lamellar-level correlations between the local composition and local mechanical properties in mouse bone. Our methodologies allow us to convert the raw load-displacement datasets to much more meaningful indentation stress–strain curves that accurately capture the loading and unloading elastic moduli, the indentation yield points, as well as the post-yield characteristics in the tested samples. Using samples of two different inbred mouse strains, A/J and C57BL/6J (B6), we successfully demonstrate the correlations between the mechanical information obtained from spherical nanoindentation measurements to the local composition measured using Raman spectroscopy. In particular, we observe that a higher mineral-to-matrix ratio correlated well with a higher local modulus and yield strength in all samples. Thus, new bone regions exhibited lower moduli and yield strengths compared to more mature bone. The B6 mice were also found to exhibit lower modulus and yield strength values compared to the more mineralized A/J strain. PMID:22842281

  12. Depth-sensing nano-indentation on a myelinated axon at various stages

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Chin; Liao, Jiunn-Der; Lin, Chou-Ching K.; Ju, Ming-Shaung

    2011-07-01

    A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.

  13. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    SciTech Connect

    Liu, Y.; Wang, H.; Zhang, X.

    2015-11-30

    Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentation studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.

  14. The evolution of machining-induced surface of single-crystal FCC copper via nanoindentation.

    PubMed

    Zhang, Lin; Huang, Hu; Zhao, Hongwei; Ma, Zhichao; Yang, Yihan; Hu, Xiaoli

    2013-05-04

    The physical properties of the machining-induced new surface depend on the performance of the initial defect surface and deformed layer in the subsurface of the bulk material. In this paper, three-dimensional molecular dynamics simulations of nanoindentation are preformed on the single-point diamond turning surface of single-crystal copper comparing with that of pristine single-crystal face-centered cubic copper. The simulation results indicate that the nucleation of dislocations in the nanoindentation test on the machining-induced surface and pristine single-crystal copper is different. The dislocation embryos are gradually developed from the sites of homogeneous random nucleation around the indenter in the pristine single-crystal specimen, while the dislocation embryos derived from the vacancy-related defects are distributed in the damage layer of the subsurface beneath the machining-induced surface. The results show that the hardness of the machining-induced surface is softer than that of pristine single-crystal copper. Then, the nanocutting simulations are performed along different crystal orientations on the same crystal surface. It is shown that the crystal orientation directly influences the dislocation formation and distribution of the machining-induced surface. The crystal orientation of nanocutting is further verified to affect both residual defect generations and their propagation directions which are important in assessing the change of mechanical properties, such as hardness and Young's modulus, after nanocutting process.

  15. Deformation mechanisms during nanoindentation of sodium borosilicate glasses of nuclear interest

    SciTech Connect

    Kilymis, D. A.; Delaye, J.-M.

    2014-07-07

    In this paper we analyze results of Molecular Dynamics simulations of Vickers nanoindentation, performed for sodium borosilicate glasses of interest in the nuclear industry. Three glasses have been studied in their pristine form, as well as a disordered one that is analogous to the real irradiated glass. We focused in the behavior of the glass during the nanoindentation in order to reveal the mechanisms of deformation and how they are affected by microstructural characteristics. Results have shown a strong dependence on the SiO{sub 2} content of the glass, which promotes densification due to the open structure of SiO{sub 4} tetrahedra and also due to the strength of Si-O bonds. Densification for the glasses is primarily expressed by the relative decrease of the Si-O-Si and Si-O-B angles, indicating rotation of the structural units and decrease of free volume. The increase of alkali content on the other hand results to higher plasticity of the matrix and increased shear flow. The most important effect on the deformation mechanism of the disordered glasses is that of the highly depolymerized network that will also induce shear flow and, in combination with the increased free volume, will result in the decreased hardness of these glasses, as has been previously observed.

  16. Defect Dependent Elasticity: Nanoindentation as a Probe of Stress-State

    SciTech Connect

    JARAUSCH,K.F.; KIELY,J.D.; HOUSTON,JACK E.; RUSSELL,P.E.

    2000-01-18

    Nanoindentation studies reveal that the measured elastic properties of materials can be strongly dependent upon their stress-state and defect structure. Using an interfacial force microscope (IFM), the measured elastic response of 100 nm thick Au films was found to be strongly correlated with the films' stress state and thermal history. Indentation elasticity was also found to vary in close proximity to grain boundaries in thin films and near surface steps on single crystal surfaces. Molecular dynamics simulations suggest that these results cannot be explained by elasticity due only to bond stretching. Instead, the measured elastic properties appear to be a combination of bond and defect compliance representing a composite modulus. We propose that stress concentration arising from the structure of grains, voids and grain boundaries is the source of an additional compliance which is sensitive to the stress state and thermal history of a material. The elastic properties of thin metallic films appear to reflect the collective elastic response of the grains, voids and grain boundaries. These results demonstrate that nanoindentation can be useful as a highly localized probe of stress-state and defect structures.

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

    PubMed

    Liu, Shaoyang; Wang, Yifen

    2011-01-01

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

  18. Lateral Tip Control Effects in CD-AFM Metrology: The Large Tip Limit

    PubMed Central

    Dixson, Ronald G.; Orji, Ndubuisi G.; Goldband, Ryan S.

    2016-01-01

    Sidewall sensing in critical dimension atomic force microscopes (CD-AFMs) usually involves continuous lateral dithering of the tip or the use of a control algorithm and fast response piezo actuator to position the tip in a manner that resembles touch-triggering of coordinate measuring machine (CMM) probes. All methods of tip position control, however, induce an effective tip width that may deviate from the actual geometrical tip width. Understanding the influence and dependence of the effective tip width on the dither settings and lateral stiffness of the tip can improve the measurement accuracy and uncertainty estimation for CD-AFM measurements. Since CD-AFM typically uses tips that range from 15 nm to 850 nm in geometrical width, the behavior of effective tip width throughout this range should be understood. The National Institute of Standards and Technology (NIST) has been investigating the dependence of effective tip width on the dither settings and lateral stiffness of the tip, as well as the possibility of material effects due to sample composition. For tip widths of 130 nm and lower, which also have lower lateral stiffness, the response of the effective tip width to lateral dither is greater than for larger tips. However, we have concluded that these effects will not generally result in a residual bias, provided that the tip calibration and sample measurement are performed under the same conditions. To validate that our prior conclusions about the dependence of effective tip width on lateral stiffness are valid for large CD-tips, we recently performed experiments using a very large non-CD tip with an etched plateau of approximately 2 μm width. The effective lateral stiffness of these tips is at least 20 times greater than typical CD-AFM tips, and these results supported our prior conclusions about the expected behavior for larger tips. The bottom-line importance of these latest observations is that we can now reasonably conclude that a dither slope of 3 nm

  19. Measurement of ultra thin film fracture toughness by nano-indentation: A numerical study

    NASA Astrophysics Data System (ADS)

    Burke, Benjamin

    As the individual layers of interconnect structures decrease in size, it becomes increasingly difficult to determine the fracture toughness, and hence the reliability, of these layers. After a layer is thinner than ˜500nm, it becomes difficult to determine the fracture toughness directly with traditional methods. Using nano-indentation, it is possible to extract the cohesive and adhesive fracture energies of these films without elaborate experimental setups. There are, however, several issues with this approach. Nano-indentation creates cracks both within the film (the cohesive cracks) and between the film and the substrate (the adhesive cracks) as well as significant plastic deformation of the film and substrate. Using SIMULA Abaqus Standard, a commercial finite element analysis tool, 2D and 3D models were created to examine the deformation characteristics associated with the nano-indentation process. The models either have pre-existing stationary cracks, or simulated by cohesive zone surfaces to account for crack nucleation and growth. The 2D model is axi-symmetric and only accounts for the adhesive crack. It is used primarily as a test the cohesive zone model and to begin to determine experimental testing limits. The 3D model is a one sixth slice of the area indented. Both cohesive and adhesive cracks are modeled and the interaction between the two cracks is investigated. While there are many parameters controlling the crack initiation and propagation process, several trends were identified. The domain of practical testing should be between one and three film thickness, so as to avoid the confluence of the indenter plastic process zone on the propagating crack front. When excursion on the load-indentation depth happens, the fracture energy is about 20% of the associated work done by the indenter (or the area under the excursion segment). The FEM simulation showed the general role of film thickness, toughness and modulus on the initiation and propagation of both

  20. Strain rate sensitivity of nanoindentation creep in an AlCoCrFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Qiao, J. W.

    2016-09-01

    Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced strain gradient induced by higher strain rate leads to decreased strain rate sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure.

  1. AFM review study on pox viruses and living cells.

    PubMed

    Ohnesorge, F M; Hörber, J K; Häberle, W; Czerny, C P; Smith, D P; Binnig, G

    1997-10-01

    Single living cells were studied in growth medium by atomic force microscopy at a high--down to one image frame per second--imaging rate over time periods of many hours, stably producing hundreds of consecutive scans with a lateral resolution of approximately 30-40 nm. The cell was held by a micropipette mounted onto the scanner-piezo as shown in Häberle, W., J. K. H. Hörber, and G. Binnig. 1991. Force microscopy on living cells. J. Vac. Sci. Technol. B9:1210-0000. To initiate specific processes on the cell surface the cells had been infected with pox viruses as reported earlier and, most likely, the liberation of a progeny virion by the still-living cell was observed, hence confirming and supporting earlier results (Häberle, W., J. K. H. Hörber, F. Ohnesorge, D. P. E. Smith, and G. Binnig. 1992. In situ investigations of single living cells infected by viruses. Ultramicroscopy. 42-44:1161-0000; Hörber, J. K. H., W. Häberle, F. Ohnesorge, G. Binnig, H. G. Liebich, C. P. Czerny, H. Mahnel, and A. Mayr. 1992. Investigation of living cells in the nanometer regime with the atomic force microscope. Scanning Microscopy. 6:919-930). Furthermore, the pox viruses used were characterized separately by AFM in an aqueous environment down to the molecular level. Quasi-ordered structural details were resolved on a scale of a few nm where, however, image distortions and artifacts due to multiple tip effects are probably involved--just as in very high resolution (<15-20 nm) images on the cells. Although in a very preliminary manner, initial studies on the mechanical resonance properties of a single living (noninfected) cell, held by the micropipette, have been performed. In particular, frequency response spectra were recorded that indicate elastic properties and enough stiffness of these cells to make the demonstrated rapid scanning of the imaging tip plausible. Measurements of this kind, especially if they can be proven to be cell-type specific, may perhaps have a large

  2. Plant protein interactions studied using AFM force spectroscopy: nanomechanical and adhesion properties.

    PubMed

    Fahs, Ahmad; Louarn, Guy

    2013-07-21

    The present work was focused on the nanomechanical and adhesion properties of the napin (2S albumin) and cruciferin (12S globulin) rapeseed (Brassica napus L.) proteins, respectively, a low and high molecular weight seed protein. Using chemically modified AFM tips, force spectroscopy experiments demonstrated notable differences in the tip-protein interaction strength with regard to the nature of the protein and pH of the aqueous environment. The results clearly underline the role of residence time and electrostatic interactions in the protein-protein adhesion force. Although the nanomechanical experiments concerned more than a single molecule, unfolding length and force characteristics of the rapeseed proteins have been statistically found to be sensitive to the structural properties of the protein. This study provides insight into the characterization of rapeseed proteins and then a better knowledge of their interaction and assembling at the nanoscale range.

  3. Plant protein interactions studied using AFM force spectroscopy: nanomechanical and adhesion properties.

    PubMed

    Fahs, Ahmad; Louarn, Guy

    2013-07-21

    The present work was focused on the nanomechanical and adhesion properties of the napin (2S albumin) and cruciferin (12S globulin) rapeseed (Brassica napus L.) proteins, respectively, a low and high molecular weight seed protein. Using chemically modified AFM tips, force spectroscopy experiments demonstrated notable differences in the tip-protein interaction strength with regard to the nature of the protein and pH of the aqueous environment. The results clearly underline the role of residence time and electrostatic interactions in the protein-protein adhesion force. Although the nanomechanical experiments concerned more than a single molecule, unfolding length and force characteristics of the rapeseed proteins have been statistically found to be sensitive to the structural properties of the protein. This study provides insight into the characterization of rapeseed proteins and then a better knowledge of their interaction and assembling at the nanoscale range. PMID:23732983

  4. Solvent-mediated repair and patterning of surfaces by AFM

    SciTech Connect

    Elhadj, S; Chernov, A; De Yoreo, J

    2007-10-30

    A tip-based approach to shaping surfaces of soluble materials with nanometer-scale control is reported. The proposed method can be used, for example, to eliminate defects and inhomogeneities in surface shape, repair mechanical or laser-induced damage to surfaces, or perform 3D lithography on the length scale of an AFM tip. The phenomenon that enables smoothing and repair of surfaces is based on the transport of material from regions of high- to low-curvature within the solution meniscus formed in a solvent-containing atmosphere between the surface in question and an AFM tip scanned over the surface. Using in situ AFM measurements of the kinetics of surface remodeling on KDP (KH{sub 2}PO{sub 4}) crystals in humid air, we show that redistribution of solute material during relaxation of grooves and mounds is driven by a reduction in surface free energy as described by the Gibbs-Thomson law. We find that the perturbation from a flat interface evolves according to the diffusion equation where the effective diffusivity is determined by the product of the surface stiffness and the step kinetic coefficient. We also show that, surprisingly, if the tip is instead scanned over or kept stationary above an atomically flat area of the surface, a convex structure is formed with a diameter that is controlled by the dimensions of the meniscus, indicating that the presence of the tip and meniscus reduces the substrate chemical potential beneath that of the free surface. This allows one to create nanometer-scale 3D structures of arbitrary shape without the removal of substrate material or the use of extrinsic masks or chemical compounds. Potential applications of these tip-based phenomena are discussed.

  5. Image Analysis and Length Estimation of Biomolecules Using AFM

    PubMed Central

    Sundstrom, Andrew; Cirrone, Silvio; Paxia, Salvatore; Hsueh, Carlin; Kjolby, Rachel; Gimzewski, James K.; Reed, Jason; Mishra, Bud

    2014-01-01

    There are many examples of problems in pattern analysis for which it is often possible to obtain systematic characterizations, if in addition a small number of useful features or parameters of the image are known a priori or can be estimated reasonably well. Often, the relevant features of a particular pattern analysis problem are easy to enumerate, as when statistical structures of the patterns are well understood from the knowledge of the domain. We study a problem from molecular image analysis, where such a domain-dependent understanding may be lacking to some degree and the features must be inferred via machine-learning techniques. In this paper, we propose a rigorous, fully automated technique for this problem. We are motivated by an application of atomic force microscopy (AFM) image processing needed to solve a central problem in molecular biology, aimed at obtaining the complete transcription profile of a single cell, a snapshot that shows which genes are being expressed and to what degree. Reed et al. (“Single molecule transcription profiling with AFM,” Nanotechnology, vol. 18, no. 4, 2007) showed that the transcription profiling problem reduces to making high-precision measurements of biomolecule backbone lengths, correct to within 20–25 bp (6–7.5 nm). Here, we present an image processing and length estimation pipeline using AFM that comes close to achieving these measurement tolerances. In particular, we develop a biased length estimator on trained coefficients of a simple linear regression model, biweighted by a Beaton–Tukey function, whose feature universe is constrained by James–Stein shrinkage to avoid overfitting. In terms of extensibility and addressing the model selection problem, this formulation subsumes the models we studied. PMID:22759526

  6. Adsorption Studies with AFM of Human Plasma Fibrinogen on Silicon Surfaces

    NASA Astrophysics Data System (ADS)

    Gause, Sheena; Kong, Wendy; Rowe

    2007-11-01

    Fibrinogen (FGN) plays an important role in the clotting of blood. Human plasma fibrinogen (HPF) is a protein that readily adsorbs on biomaterial surfaces. The purpose of this experiment was to use the Atomic Force Microscope to study the adsorption of HPF molecules or FGN onto several silicon surfaces with different orientations and resistivities. The size of the FGN molecules found to be somewhat different of Si(111), (100) and (110) were compared to the size of the FGN molecules in solution (45 nm in length, the end dynodes measures to be 6.5 nm in diameter, and the middle dynode measures to be 5 nm in diameter. For this study, the CPR (Thermo-microscope) Atomic Force Microscope (AFM) was used to observe the amount of fibrinogen molecules adsorbed by Si (111) with a resistance of .0281-.0261 φ cm, Si (111) with a resistance of 1 φ cm, Si (100), and Si (110) surfaces. In finding any single fibrinogen molecules, the appropriate image scans and measurements were taken. After collection and analysis of the data, it was found from AFM that the fibrinogen molecules found on Si (110) mostly resembled fibrinogen molecules found in solution. The other images showed that the fibrinogen molecules adsorbed on Silicon substrates is significantly greater (˜10-20 %) than those in solution.

  7. Cantilever energy effects on bimodal AFM: phase and amplitude contrast of multicomponent samples

    NASA Astrophysics Data System (ADS)

    Chakraborty, Ishita; Yablon, Dalia G.

    2013-11-01

    Bimodal atomic force microscopy (AFM) is a recently developed technique of dynamic AFM where a higher eigenmode of the cantilever is simultaneously excited along with the fundamental eigenmode. The effects of different operating parameters while imaging an impact copolymer blend of polypropylene (PP) and ethylene-propylene (E-P) rubber in bimodal mode are explored through experiments and numerical simulations. The higher mode amplitude and phase contrasts between the two components of the sample reverse at different points as the free amplitude of the higher eigenmode is increased. Three different regimes are identified experimentally depending on the relative contrast between the PP and the E-P rubber. It is observed that the kinetic energy and free air drive input energy of the two cantilever eigenmodes play a role in determining the regimes of operation. Numerical simulations conducted with appropriate tip-sample interaction forces support the experimental results. An understanding of these regimes and the associated cantilever dynamics will guide a rational approach towards selecting appropriate operating parameters.

  8. Direct measurement of optical force induced by near-field plasmonic cavity using dynamic mode AFM

    DOE PAGES

    Guan, Dongshi; Hang, Zhi Hong; Marset, Zsolt; Liu, Hui; Kravchenko, Ivan I.; Chan, Ho Bun; Chan, C. T.; Tong, Penger

    2015-11-20

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength goldmore » disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. Lastly, the experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures.« less

  9. Direct measurement of optical force induced by near-field plasmonic cavity using dynamic mode AFM

    SciTech Connect

    Guan, Dongshi; Hang, Zhi Hong; Marset, Zsolt; Liu, Hui; Kravchenko, Ivan I.; Chan, Ho Bun; Chan, C. T.; Tong, Penger

    2015-11-20

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. Lastly, the experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures.

  10. Direct Measurement of Optical Force Induced by Near-Field Plasmonic Cavity Using Dynamic Mode AFM

    PubMed Central

    Guan, Dongshi; Hang, Zhi Hong; Marcet, Zsolt; Liu, Hui; Kravchenko, I. I.; Chan, C. T.; Chan, H. B.; Tong, Penger

    2015-01-01

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. The experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures. PMID:26586455

  11. Theoretical modelling of AFM for bimetallic tip-substrate interactions

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1991-01-01

    Recently, a new technique for calculating the defect energetics of alloys based on Equivalent Crystal Theory was developed. This new technique successfully predicts the bulk properties for binary alloys as well as segregation energies in the dilute limit. The authors apply this limit for the calculation of energy and force as a function of separation of an atomic force microscope (AFM) tip and substrate. The study was done for different combinations of tip and sample materials. The validity of the universality discovered for the same metal interfaces is examined for the case of different metal interactions.

  12. An approach towards 3D sensitive AFM cantilevers

    NASA Astrophysics Data System (ADS)

    Koops, Richard; Fokkema, Vincent

    2014-04-01

    The atomic force microscope (AFM) tapping mode is a highly sensitive local probing technique that is very useful to study and measure surface properties down to the atomic scale. The tapping mode is mostly implemented using the resonance of the first bending mode of the cantilever and therefore provides sensitivity mainly along the direction of this oscillation. Driven by the semiconductor industry, there is an increasing need for accurate measurements of nanoscale structures for side wall characterization by AFM that requires additional sensitivity in the lateral direction. The conventional tapping mode has been augmented by various authors, for example by tilting the cantilever system (Cho et al 2011 Rev. Sci. Instrum. 82 023707) to access the sidewall or using a torsion mode (Dai et al 2011 Meas. Sci. Technol. 22 094009) of the cantilever to provide additional lateral sensitivity. These approaches however trade lateral sensitivity for vertical sensitivity or still lack sensitivity in the remaining lateral direction. We present an approach towards true 3D sensitivity for AFM cantilevers based on simultaneous excitation and optical detection of multiple cantilever resonance modes along three axes. Tuning the excitation of the cantilever to specific frequencies provides a mechanism to select only those cantilever modes that have the desired characteristics. Additionally, cantilever engineering has been used to design and create a substructure within the cantilever that has been optimized for specific resonance behavior around 4 MHz. In contrast to the conventional approach of using a piezo to actuate the cantilever modulation, we present results on photo-thermal excitation using an intensity modulated low-power laser source. By tightly focusing the excitation spot on the cantilever we were able to attain a deflection efficiency of 0.7 nm µW-1 for the first bending mode. The presented approach results in an efficient all optical excitation and deflection detection

  13. The Advancing State of AF-M315E Technology

    NASA Technical Reports Server (NTRS)

    Masse, Robert; Spores, Ronald A.; McLean, Chris

    2014-01-01

    The culmination of twenty years of applied research in hydroxyl ammonium nitrate (HAN)-based monopropellants, the NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) will achieve the first on-orbit demonstration of an operational AF-M315E green propellant propulsion system by the end of 2015. Following an contextual overview of the completed flight design of the GPIM propellant storage and feed system, results of first operation of a flight-representative heavyweight 20-N engineering model thruster (to be conducted in mid-2014) are presented with performance comparisons to prior lab model (heavyweight) test articles.

  14. Nanoindentation Fracture Behaviors of Diamond-Like Carbon Film on Aluminum Alloy with Different Interface Toughnesses

    NASA Astrophysics Data System (ADS)

    Nose, Kenji; Sasaki, Yuto; Kamiko, Masao; Mitsuda, Yoshitaka

    2012-09-01

    Fracture behaviors of a diamond-like carbon (DLC) film on an aluminum alloy (AA2017) were analyzed by a nanoindentation test under conditions of deep and full penetrations of an indenter tip through the DLC film. The interface structure between the DLC and AA2017 was modified by using the substrate sputtering and redeposition (SSRD) method. The films deposited with a shorter (30 min) SSRD duration showed weak adhesion to the substrate and often resulted in wide delamination from the impressions. At the same time, films deposited with a longer (120 min) SSRD duration showed no such delamination. Obvious brittle fractures were detected in the load-displacement curves mainly in the film with the short SSRD duration. These results suggest that a long SSRD inhibited the delamination of the DLC film from AA2017 under local and strong stress conditions because of the improved interface toughness.

  15. Effects of sequential tungsten and helium ion implantation on nano-indentation hardness of tungsten

    SciTech Connect

    Armstrong, D. E. J.; Edmondson, P. D.; Roberts, S. G.

    2013-06-24

    To simulate neutron and helium damage in a fusion reactor first wall sequential self-ion implantation up to 13 dpa followed by helium-ion implantation up to 3000 appm was performed to produce damaged layers of {approx}2 {mu}m depth in pure tungsten. The hardness of these layers was measured using nanoindentation and was studied using transmission electron microscopy. Substantial hardness increases were seen in helium implanted regions, with smaller hardness increases in regions which had already been self-ion implanted, thus, containing pre-existing dislocation loops. This suggests that, for the same helium content, helium trapped in distributed vacancies gives stronger hardening than helium trapped in vacancies condensed into dislocation loops.

  16. Mechano-rheological properties of the murine thrombus determined via nanoindentation and finite element modeling.

    PubMed

    Slaboch, Constance L; Alber, Mark S; Rosen, Elliot D; Ovaert, Timothy C

    2012-06-01

    Deep vein thrombosis, pulmonary embolism, and abdominal aortic aneurysms are blood-related diseases that represent a major public health problem. These diseases are characterized by the formation of a thrombus (i.e., blood clot) that either blocks a major artery or causes an aortic rupture. Identifying the mechanical properties of thrombi can help determine when these incidents will occur. In this investigation, a murine thrombus, formed from platelet-rich plasma, calcium, and thrombin, was nanoindented and the elastic modulus was estimated via elastic contact theory. This information was used as input to an inverse finite element simulation, which determined optimal values for the elastic modulus and viscosity of the thrombus using a viscoelastic material model. A sensitivity analysis was also performed to determine which material parameters have the greatest affect on the simulation. Results from this investigation demonstrate the feasibility of the mechanical characterization of a murine thrombus using nanoindentation. PMID:22520420

  17. Magnetic field tunable small-scale mechanical properties of nickel single crystals measured by nanoindentation technique.

    PubMed

    Zhou, Hao; Pei, Yongmao; Fang, Daining

    2014-01-01

    Nano- and micromagnetic materials have been extensively employed in micro-functional devices. However, measuring small-scale mechanical and magnetomechanical properties is challenging, which restricts the design of new products and the performance of smart devices. A new magnetomechanical nanoindentation technique is developed and tested on a nickel single crystal in the absence and presence of a saturated magnetic field. Small-scale parameters such as Young's modulus, indentation hardness, and plastic index are dependent on the applied magnetic field, which differ greatly from their macroscale counterparts. Possible mechanisms that induced 31% increase in modulus and 7% reduction in hardness (i.e., the flexomagnetic effect and the interaction between dislocations and magnetic field, respectively) are analyzed and discussed. Results could be useful in the microminiaturization of applications, such as tunable mechanical resonators and magnetic field sensors.

  18. In Situ Nanoindentation Studies on Detwinning and Work Hardening in Nanotwinned Monolithic Metals

    DOE PAGES

    Liu, Y.; Li, N.; Bufford, D.; Lee, J. H.; Wang, J.; Wang, H.; Zhang, X.

    2015-07-14

    Certain nanotwinned (nt) metals have rare combinations of high mechanical strength and ductility. Here, we review recent in situ nanoindentation studies (using transmission electron microscopes) on the deformation mechanisms of nt face-centered cubic metals including Cu, Ni, and Al with a wide range of stacking fault energy (SFE). Moreover, in nt Cu with low-to-intermediate SFE, detwinning (accompanied by rapid twin boundary migration) occurs at ultralow stress. In Ni with relatively high SFE, coherent {111} twin boundaries lead to substantial work hardening. Twinned Al has abundant {112} incoherent twin boundaries, which induce significant work-hardening capability and plasticity in Al. Finally, twinmore » boundaries in Al also migrate but at very high stresses. Furthermore, molecular dynamics simulations reveal the influence of SFE on deformation mechanisms in twinned metals.« less

  19. In Situ Nanoindentation Studies on Detwinning and Work Hardening in Nanotwinned Monolithic Metals

    SciTech Connect

    Liu, Y.; Li, N.; Bufford, D.; Lee, J. H.; Wang, J.; Wang, H.; Zhang, X.

    2015-07-14

    Certain nanotwinned (nt) metals have rare combinations of high mechanical strength and ductility. Here, we review recent in situ nanoindentation studies (using transmission electron microscopes) on the deformation mechanisms of nt face-centered cubic metals including Cu, Ni, and Al with a wide range of stacking fault energy (SFE). Moreover, in nt Cu with low-to-intermediate SFE, detwinning (accompanied by rapid twin boundary migration) occurs at ultralow stress. In Ni with relatively high SFE, coherent {111} twin boundaries lead to substantial work hardening. Twinned Al has abundant {112} incoherent twin boundaries, which induce significant work-hardening capability and plasticity in Al. Finally, twin boundaries in Al also migrate but at very high stresses. Furthermore, molecular dynamics simulations reveal the influence of SFE on deformation mechanisms in twinned metals.

  20. Molecular dynamics simulation of nano-indentation of (111) cubic boron nitride with optimized Tersoff potential

    NASA Astrophysics Data System (ADS)

    Zhao, Yinbo; Peng, Xianghe; Fu, Tao; Huang, Cheng; Feng, Chao; Yin, Deqiang; Wang, Zhongchang

    2016-09-01

    We conduct molecular dynamics simulation of nanoindentation on (111) surface of cubic boron nitride and find that shuffle-set dislocations slip along <112> direction on {111} plane at the initial stage of the indentation. The shuffle-set dislocations are then found to meet together, forming surfaces of a tetrahedron. We also find that the surfaces are stacking-fault zones, which intersect with each other, forming edges of stair-rod dislocations along <110> direction. Moreover, we also calculate the generalized stacking fault (GSF) energies along various gliding directions on several planes and find that the GSF energies of the <112>{111} and <110>{111} systems are relatively smaller, indicating that dislocations slip more easily along <110> and <112> directions on the {111} plane.

  1. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    SciTech Connect

    Zhao, Junhua; Jiang, Jin-Wu; Rabczuk, Timon

    2013-12-02

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS{sub 2}) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS{sub 2}. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  2. Influence of crystallographic orientation on the response of copper crystallites to nanoindentation

    SciTech Connect

    Korchuganov, Aleksandr V.; Kryzhevich, Dmitrij S. E-mail: kost@ispms.tsc.ru; Zolnikov, Konstantin P. E-mail: kost@ispms.tsc.ru; Psakhie, Sergey G.

    2014-11-14

    Molecular dynamics simulation was performed to study the features of nucleation and development of plastic deformation in copper crystallites in nanoindentation with different crystallographic orientations of their loaded surface: (011), (001), and (111). Atomic interaction was described by a potential constructed in terms of the embedded atom method. It is shown that behavior of the crystallite reaction force correlates well with a change in the fraction of atoms involved in local structural rearrangements. The generation of local structural changes decreases the slope of the crystallite reaction force curve or results in an extremum due to internal stress relaxation. Analysis of structural changes in the material being indented demonstrates that the orientation of its loaded surface greatly affects the features of nucleation and development of plastic deformation.

  3. In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries.

    PubMed

    Bufford, D; Liu, Y; Wang, J; Wang, H; Zhang, X

    2014-01-01

    Nanotwinned metals have been the focus of intense research recently, as twin boundaries may greatly enhance mechanical strength, while maintaining good ductility, electrical conductivity and thermal stability. Most prior studies have focused on low stacking-fault energy nanotwinned metals with coherent twin boundaries. In contrast, the plasticity of twinned high stacking-fault energy metals, such as aluminium with incoherent twin boundaries, has not been investigated. Here we report high work hardening capacity and plasticity in highly twinned aluminium containing abundant Σ3{112} incoherent twin boundaries based on in situ nanoindentation studies in a transmission electron microscope and corresponding molecular dynamics simulations. The simulations also reveal drastic differences in deformation mechanisms between nanotwinned copper and twinned aluminium ascribed to stacking-fault energy controlled dislocation-incoherent twin boundary interactions. This study provides new insight into incoherent twin boundary-dominated plasticity in high stacking-fault energy twinned metals. PMID:25204688

  4. Thin-Film Fracture During Nanoindentation of a Titanium Oxide Film–Titanium System

    SciTech Connect

    Pang, Mengzhi; Bahr, David F.

    2001-09-09

    Nanoindentation testing of the titanium oxide/titanium system with electrochemically grown oxide films exhibits permanent deformation prior to a yield excusion, indicating that the occurrence of this suddent discontinuity is predominantly controlled by oxide film cracking rather than dislocaton nucleation and multiplication. Observations of circumferential cracking also lend support to this explanation. A model has been developed to predict the mechanical response prior to oxide fracture for the case of a hard coating on a soft substrate. During loading contact, the hard coating undergoes elastic deflection which may include both bending and membrane stretching effects, while the substrate is elastoplastically deformed. The model works well for surface films thicker than 20 nm. Additionally, the maximum radial tensile stress in anodically grown titanium oxide, which is responsible for film cracking at the critical load, is approximately 15 GPa.

  5. Nanoindentation study of irradiation and temperature effects in yttria-stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Kurpaska, L.; Jagielski, J.; Nowakowska-Langier, K.

    2016-07-01

    In the present study, the detailed evaluation of nanomechanical properties in terms of hardness and Young's modulus of irradiated polycrystalline YSZ pellets were studied using the nanoindentation technique. The samples were irradiated at room temperature with 150 keV Ar-ions to a fluences of 1 × 1014 and 1 × 1015 ions/cm2 (i.e. before bubble formation), which correspond to a peak damage of 0.12 and 1.2 dpa respectively. Substantial improvement of mechanical properties related to the creation of both radiation defects and residual stress in the implanted surface layer were observed. Additionally, in-situ high temperature nanomechanical investigation of pristine YSZ pellet was conducted. A significant decrease of nanomechanical properties was observed with increasing temperature.

  6. TEM, XRD and nanoindentation characterization of Xenon ion irradiation damage in austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Huang, H. F.; Li, J. J.; Li, D. H.; Liu, R. D.; Lei, G. H.; Huang, Q.; Yan, L.

    2014-11-01

    Cross-sectional and bulk specimens of a 20% cold-worked 316 austenitic stainless steel (CW 316 SS) has been characterized by TEM, XRD and nanoindentation to determine the microstructural evolution and mechanical property changes of 316 SS after irradiation with 7 MeV Xe26+ ions. TEM results reveal the presence of dislocation loops with a number density of approximately 3 × 1022 m-3 and sizes between 3 to 10 nm due to the collapse of vacancy rich cores inside displacement cascades. Peak broadening observed in XRD diffraction patters reveal systematic changes to lattice parameters due to irradiation. The calculated indentation values in irradiated 316 SS were found to be much higher in comparison to the unirradiated specimen, indicating the dose dependent effect of irradiation on hardness. The relationship between irradiation induced microstructural evolution and the changes to the mechanical properties of CW 316 SS are discussed in the context of fluence and irradiation temperature.

  7. Nanoindentation of hcp metals: a comparative simulation study of the evolution of dislocation networks

    NASA Astrophysics Data System (ADS)

    Alabd Alhafez, Iyad; Ruestes, Carlos J.; Gao, Yu; Urbassek, Herbert M.

    2016-01-01

    Using molecular dynamics simulation, we study the nanoindentation of three hcp metals: Mg, Ti, and Zr. Both the basal and two prismatic surface planes are considered. We focus on the characterization of the plasticity generated in the crystal. The similarities to, and the differences from, the behavior of the more commonly investigated fcc and bcc metals are highlighted. We find that hcp metals show a larger variety than the fcc and bcc metals studied up until now. The prolific emission of prismatic loops can lead to extended plastic zones. The size of the plastic zone is quantified by the ratio f of the plastic zone radius to the radius of the contact area. We find values of between 1.6 (an almost collapsed zone) and >5 in the latter case, complex dislocation networks build up which are extended in the direction of easy glide.

  8. Magnetic Field Tunable Small-scale Mechanical Properties of Nickel Single Crystals Measured by Nanoindentation Technique

    PubMed Central

    Zhou, Hao; Pei, Yongmao; Fang, Daining

    2014-01-01

    Nano- and micromagnetic materials have been extensively employed in micro-functional devices. However, measuring small-scale mechanical and magnetomechanical properties is challenging, which restricts the design of new products and the performance of smart devices. A new magnetomechanical nanoindentation technique is developed and tested on a nickel single crystal in the absence and presence of a saturated magnetic field. Small-scale parameters such as Young's modulus, indentation hardness, and plastic index are dependent on the applied magnetic field, which differ greatly from their macroscale counterparts. Possible mechanisms that induced 31% increase in modulus and 7% reduction in hardness (i.e., the flexomagnetic effect and the interaction between dislocations and magnetic field, respectively) are analyzed and discussed. Results could be useful in the microminiaturization of applications, such as tunable mechanical resonators and magnetic field sensors. PMID:24695002

  9. Temperature Dependent Mechanical Property of PZT Film: An Investigation by Nanoindentation

    PubMed Central

    Li, Yingwei; Feng, Shangming; Wu, Wenping; Li, Faxin

    2015-01-01

    Load-depth curves of an unpoled Lead Zirconate Titanate (PZT) film composite as a function of temperature were measured by nanoindentation technique. Its reduce modulus and hardness were calculated by the typical Oliver-Pharr method. Then the true modulus and hardness of the PZT film were assessed by decoupling the influence of substrate using methods proposed by Zhou et al. and Korsunsky et al., respectively. Results show that the indentation depth and modulus increase, but the hardness decreases at elevated temperature. The increasing of indentation depth and the decreasing of hardness are thought to be caused by the decreasing of the critical stress needed to excite dislocation initiation at high temperature. The increasing of true modulus is attributed to the reducing of recoverable indentation depth induced by back-switched domains. The influence of residual stress on the indentation behavior of PZT film composite was also investigated by measuring its load-depth curves with pre-load strains. PMID:25768957

  10. Microtexture and Nanoindentation Study of Delamination Cracking in Al-Cu-Li-X Alloys

    NASA Technical Reports Server (NTRS)

    Crooks, R.; Domack, M. S.; Wagner, J. A.

    2005-01-01

    Commercial Al-Li alloys have strength and weight advantages over non-Li aluminum alloys. The fracture behavior of these alloys is unusual and has limited their use. The fracture mode, described as delamination, is intergranular, along the broad grain boundaries parallel to the rolling plane of the plate. Microtexture analyses have shown that delaminations occur along boundaries with greater than 30 misorientation. However, it was observed that relatively few of the high angle boundaries exhibited this behavior. Some grains of the retained deformation texture show high internal misorientation, which is a measure of stored strain energy. Delamination tends to occur between these grains and adjacent, recrystallized grains. Nanoindentation studies indicate a higher hardness for the high internal misorientation grains. These results suggest that the delamination could be reduced by processing the alloys to minimize grain-to-grain property disparities.

  11. Molecular dynamics simulation of nanoindentation on Cu/Ni nanotwinned multilayer films using a spherical indenter

    PubMed Central

    Fu, Tao; Peng, Xianghe; Chen, Xiang; Weng, Shayuan; Hu, Ning; Li, Qibin; Wang, Zhongchang

    2016-01-01

    We performed molecular dynamics simulation of nanoindentation on Cu/Ni nanotwinned multilayer films using a spherical indenter, aimed to investigate the effects of hetero-twin interface and twin thickness on hardness. We found that both twinning partial slip (TPS) and partial slip parallel with twin boundary (PSPTB) can reduce hardness and therefore should not be ignored when evaluating mechanical properties at nanoscale. There is a critical range of twin thickness λ (~25 Å < λ < ~31 Å), in which hardness of the multilayer films is maximized. At a smaller λ, TPSs appear due to the reaction between partial dislocations and twin boundary accounts for the softening-dominated mechanism. We also found that the combination of the lowered strengthening due to confined layer slips and the softening due to TPSs and PSPTBs results in lower hardness at a larger λ. PMID:27767046

  12. He and H irradiation effects on the nanoindentation hardness of CLAM steel

    NASA Astrophysics Data System (ADS)

    Jiang, Siben; Peng, Lei; Ge, Hongen; Huang, Qunying; Xin, Jingping; Zhao, Ziqiang

    2014-12-01

    In this study, He and H ion irradiation induced hardening behavior of China Low Activation Martensitic (CLAM) steel was investigated, and the influence of Si on irradiation hardening was also examined. CLAM steel with different Si contents, Heat 0912 and Heat 0408D, were irradiated with single He (He concentration range from 0 to 2150 appm) ion beam and He/H dual ion beams. Then nanoindentation tests were applied to evaluate the ion irradiation induced hardening effect. The result of Heat 0912 showed hardening effect would be more serious with higher He concentration, and the trend saturated when He concentration reach 1000 appm. Comparing the result of Heat 0912 and Heat 0408D, higher Si content might improve the resistance to hardening.

  13. Deformation and fracture of LLM-105 molecular crystals studied by nanoindentation

    NASA Astrophysics Data System (ADS)

    Kucheyev, S. O.; Gash, A. E.; Lorenz, T.

    2014-04-01

    Mechanical deformation of crystalline high explosives plays an important role in both the fabrication of polymer-bonded explosives and controlling their sensitivity to mechanically-induced decomposition. Here, we study the deformation behavior of (010)-oriented LLM-105 and β-HMX molecular crystals by nanoindentation with pyramidal (Berkovich) and spherical (19 μm-diameter) indenters. Results reveal indentation elastic moduli of 21 and 18 GPa and Berkovich hardness of 0.73 and 0.65 GPa for LLM-105 and HMX, respectively. For LLM-105 (but not for HMX), indentation stress remains essentially unchanged for spherical indentation strains of ˜10-25%, suggesting that inelastic deformation above a certain strain proceeds via flow at constant stress. Both materials exhibit highly anisotropic surface fracture patterns after Berkovich and spherical indentation, consistent with fracture along (011) cleavage planes. No deformation-induced material decomposition is observed in either material for the indentation conditions used.

  14. Tubulin Bond Energies and Microtubule Biomechanics Determined from Nanoindentation in Silico

    PubMed Central

    2015-01-01

    Microtubules, the primary components of the chromosome segregation machinery, are stabilized by longitudinal and lateral noncovalent bonds between the tubulin subunits. However, the thermodynamics of these bonds and the microtubule physicochemical properties are poorly understood. Here, we explore the biomechanics of microtubule polymers using multiscale computational modeling and nanoindentations in silico of a contiguous microtubule fragment. A close match between the simulated and experimental force–deformation spectra enabled us to correlate the microtubule biomechanics with dynamic structural transitions at the nanoscale. Our mechanical testing revealed that the compressed MT behaves as a system of rigid elements interconnected through a network of lateral and longitudinal elastic bonds. The initial regime of continuous elastic deformation of the microtubule is followed by the transition regime, during which the microtubule lattice undergoes discrete structural changes, which include first the reversible dissociation of lateral bonds followed by irreversible dissociation of the longitudinal bonds. We have determined the free energies of dissociation of the lateral (6.9 ± 0.4 kcal/mol) and longitudinal (14.9 ± 1.5 kcal/mol) tubulin–tubulin bonds. These values in conjunction with the large flexural rigidity of tubulin protofilaments obtained (18,000–26,000 pN·nm2) support the idea that the disassembling microtubule is capable of generating a large mechanical force to move chromosomes during cell division. Our computational modeling offers a comprehensive quantitative platform to link molecular tubulin characteristics with the physiological behavior of microtubules. The developed in silico nanoindentation method provides a powerful tool for the exploration of biomechanical properties of other cytoskeletal and multiprotein assemblies. PMID:25389565

  15. Tubulin bond energies and microtubule biomechanics determined from nanoindentation in silico.

    PubMed

    Kononova, Olga; Kholodov, Yaroslav; Theisen, Kelly E; Marx, Kenneth A; Dima, Ruxandra I; Ataullakhanov, Fazly I; Grishchuk, Ekaterina L; Barsegov, Valeri

    2014-12-10

    Microtubules, the primary components of the chromosome segregation machinery, are stabilized by longitudinal and lateral noncovalent bonds between the tubulin subunits. However, the thermodynamics of these bonds and the microtubule physicochemical properties are poorly understood. Here, we explore the biomechanics of microtubule polymers using multiscale computational modeling and nanoindentations in silico of a contiguous microtubule fragment. A close match between the simulated and experimental force-deformation spectra enabled us to correlate the microtubule biomechanics with dynamic structural transitions at the nanoscale. Our mechanical testing revealed that the compressed MT behaves as a system of rigid elements interconnected through a network of lateral and longitudinal elastic bonds. The initial regime of continuous elastic deformation of the microtubule is followed by the transition regime, during which the microtubule lattice undergoes discrete structural changes, which include first the reversible dissociation of lateral bonds followed by irreversible dissociation of the longitudinal bonds. We have determined the free energies of dissociation of the lateral (6.9 ± 0.4 kcal/mol) and longitudinal (14.9 ± 1.5 kcal/mol) tubulin-tubulin bonds. These values in conjunction with the large flexural rigidity of tubulin protofilaments obtained (18,000-26,000 pN·nm(2)) support the idea that the disassembling microtubule is capable of generating a large mechanical force to move chromosomes during cell division. Our computational modeling offers a comprehensive quantitative platform to link molecular tubulin characteristics with the physiological behavior of microtubules. The developed in silico nanoindentation method provides a powerful tool for the exploration of biomechanical properties of other cytoskeletal and multiprotein assemblies.

  16. Nanoindentation and finite element modelling of chitosan-alginate multilayer coated hydrogels.

    PubMed

    Sherstova, Tatyana; Stokke, Bjørn Torger; Skallerud, Bjørn; Maurstad, Gjertrud; Prot, Victorien Emile

    2016-09-21

    Composite soft materials are used as compounds for determining the effects of mechanical cues on cell behavior and cell encapsulation and for controlling drug release. The appropriate composite soft materials are conventionally prepared by selective deposition of polymers at the surface of an ionic hydrogel. In the present study we address the impact of a mechanically stratified two-layer structure of these materials on their overall mechanical characterization by applying a combination of nanoindentation, confocal microscopy and finite element modelling. We prepare covalent cross-linked hydrogels based on acrylamide (AAM) and including an anionic group, and impregnate them using a multilayer deposition strategy of alternating exposure to cationic chitosan and anionic alginate. The thickness of the chitosan-alginate layer on the hydrogels was determined to be 0.4 ± 0.05 μm for 4 bilayers, and 0.7 ± 0.1 μm for the 8 bilayer deposition procedure employing a fluorescently labelled chitosan and confocal microscopy. The force-indentation data for the AAM gels were highly reproducible, whereas 77% and 50% of the force-indentation data were reproducible following the 4 and 8 bilayer deposition. The main trends in the reproducible force-distance data were found to yield an apparent increased Young's modulus after the deposition. Finite element modelling showed that adaption of a homogeneous Young's modulus for the specimens with deposited layers yields approximately three times too low stiffness compared to the estimate of the mechanical properties of the outer part in the two-layered mechanical model. The thickness of the multilayer region determined by confocal microscopy was used in the model. This study shows that the mechanical layered property needs to be included in the interpretation of the nanoindentation data when there is a significant mechanical contrast.

  17. NANOINDENTATION OF THE INSERTIONAL ZONES OF HUMAN MENISCAL ATTACHMENTS INTO UNDERLYING BONE

    PubMed Central

    Hauch, K.N.; Oyen, M.L.; Odegard, G.M.; Haut Donahue, T. L.

    2009-01-01

    The fibrocartilagenous knee menisci are situated between the femoral condyles and tibia plateau and are primarily anchored to the tibia by means of four attachments at the anterior and posterior horns. Strong fixation of meniscal attachments to the tibial plateau provide resistance to extruding forces of the meniscal body, allowing the menisci to assist in load transmission from the femur to the tibia. Clinically, tears and ruptures of the meniscal attachments and insertion to bone are rare. While it has been suggested that the success of a meniscal replacement is dependent on several factors, one of which is the secure fixation and firm attachment of the replacement to the tibial plateau, little is known about the material properties of meniscal attachments and the transition in material properties from the meniscus to subchondral bone. The objective of this study was to use nanoindentation to investigate the transition from meniscal attachment into underlying subchondral bone through uncalcified and calcified fibrocartilage. Nanoindentation tests were performed on both the anterior and posterior meniscal insertions to measure the instantaneous elastic modulus and elastic modulus at infinite time. The elastic moduli were found to increase in a bi-linear fashion from the external ligamentous attachment to the subchondral bone. The elastic moduli for the anterior attachments were consistently larger than those for the matching posterior attachments at similar indentation locations. These results show that there is a gradient of stiffness from the superficial zones of the insertion close to the ligamentous attachment into the deeper zones of the bone. This information will be useful in the continued development of successful meniscal replacements and understanding of fixation of the replacements to the tibial plateau. PMID:19627840

  18. AFM analysis of bleaching effects on dental enamel microtopography

    NASA Astrophysics Data System (ADS)

    Pedreira de Freitas, Ana Carolina; Espejo, Luciana Cardoso; Botta, Sergio Brossi; Teixeira, Fernanda de Sa; Luz, Maria Aparecida A. Cerqueira; Garone-Netto, Narciso; Matos, Adriana Bona; Salvadori, Maria Cecilia Barbosa da Silveira

    2010-02-01

    The purpose of this in vitro study was to test a new methodology to evaluate the effects of 35% hydrogen peroxide agent on the microtopography of sound enamel using an atomic force microscope (AFM). The buccal sound surfaces of three extracted human lower incisors were used, without polishing the surfaces to maintain them with natural morphology. These unpolished surfaces were subjected to bleaching procedure with 35% hydrogen peroxide that consisted of 4 applications of the bleaching agent on enamel surfaces for 10 min each application. Surface images were obtained in a 15 μm × 15 μm area using an AFM. The roughness (Ra and RMS) and the power spectral density (PSD) were obtained before and after the bleaching treatment. As results we could inquire that the PSD analyses were very suitable to identifying the morphological changes on the surfaces, while the Ra and RMS parameters were insufficient to represent the morphological alterations promoted by bleaching procedure on enamel. The morphological wavelength in the range of visible light spectrum (380-750 nm) was analyzed, showing a considerable increase of the PSD with the bleaching treatment.

  19. Viscoelasticity of gelatin surfaces probed by AFM noise analysis.

    PubMed

    Benmouna, Farida; Johannsmann, Diethelm

    2004-01-01

    The viscoelastic properties of surfaces of swollen gelatin were investigated by analyzing the Brownian motion of an atomic force microscopy (AFM) cantilever in contact with the gel surface. A micron-sized glass sphere attached to the AFM cantilever is used as the dynamic probe. When the sphere approaches the gelatin surface, there is a static repulsive force without a jump into contact. The cantilever's Brownian movement is monitored in parallel, providing access to the dynamic sphere-surface interaction as quantified by the dynamic spring constant, kappa, and the drag coefficient, xi. Gelatin is used as a model substance for a variety of other soft surfaces, where the stiffness of the gel can be varied via the solvent quality, the bloom number, and the pH. The modulus derived from the static force-distance curve is in the kPa range, consistent with the literature. However, the dynamic spring constant as derived from the Brownian motion is much larger than the static differential spring constant dF/dz. On retraction, one observes a rather strong adhesion hysteresis. The strength of the bridge (as given by the dynamic spring constant and the drag coefficient) is very small. PMID:15745019

  20. Analysis of AFM cantilever dynamics close to sample surface

    NASA Astrophysics Data System (ADS)

    Habibnejad Korayem, A.; Habibnejad Korayem, Moharam; Ghaderi, Reza

    2013-07-01

    For imaging and manipulation of biological specimens application of atomic force microscopy (AFM) in liquid is necessary. In this paper, tapping-mode AFM cantilever dynamics in liquid close to sample surface is modeled and simulated by well defining the contact forces. The effect of cantilever tilting angle has been accounted carefully. Contact forces have some differences in liquid in comparison to air or vacuum in magnitude or formulation. Hydrodynamic forces are also applied on the cantilever due to the motion in liquid. A continuous beam model is used with its first mode and forward-time simulation method for simulation of its hybrid dynamics and the frequency response and amplitude versus separation diagrams are extracted. The simulation results show a good agreement with experimental results. The resonance frequency in liquid is so small in comparison to air due to additional mass and also additional damping due to the viscosity of the liquid around. The results show that the effect of separation on free vibration amplitude is great. Its effect on resonance frequency is considerable too.

  1. Pathogen identification using peptide nanotube biosensors and impedance AFM

    NASA Astrophysics Data System (ADS)

    Maccuspie, Robert I.

    Pathogen identification at highly sensitive levels is crucial to meet urgent needs in fighting the spread of disease or detecting bioterrorism events. Toward that end, a new method for biosensing utilizing fluorescent antibody nanotubes is proposed. Fundamental studies on the self-assembly of these peptide nanotubes are performed, as are applications of aligning these nanotubes on surfaces. As biosensors, these nanotubes incorporate recognition units with antibodies at their ends and fluorescent signaling units at their sidewalls. When viral pathogens were mixed with these antibody nanotubes in solution, the nanotubes rapidly aggregated around the viruses. The size of the aggregates increased as the concentration of viruses increased, as detected by flow cytometry on the order of attomolar concentrations by changes in fluorescence and light scattering intensities. This enabled determination of the concentrations of viruses at trace levels (102 to 106 pfu/mL) within 30 minutes from the receipt of samples to the final quantitative data analysis, as demonstrated on Adenovirus, Herpes Simplex Virus, Influenza, and Vaccinia virus. As another separate approach, impedance AFM is used to study the electrical properties of individual viruses and nanoparticles used as model systems. The design, development, and implementation of the impedance AFM for an Asylum Research platform is described, as well as its application towards studying the impedance of individual nanoparticles as a model system for understanding the fundamental science of how the life cycle of a virus affects its electrical properties. In combination, these approaches fill a pressing need to quantify viruses both rapidly and sensitively.

  2. Aging increases stiffness of cardiac myocytes measured by atomic force microscopy nanoindentation.

    PubMed

    Lieber, Samuel C; Aubry, Nadine; Pain, Jayashree; Diaz, Gissela; Kim, Song-Jung; Vatner, Stephen F

    2004-08-01

    It is well established that the aging heart exhibits left ventricular (LV) diastolic dysfunction and changes in mechanical properties, which are thought to be due to alterations in the extracellular matrix. We tested the hypothesis that the mechanical properties of cardiac myocytes significantly change with aging, which could contribute to the global changes in LV diastolic dysfunction. We used atomic force microscopy (AFM), which determines cellular mechanical property changes at nanoscale resolution in myocytes, from young (4 mo) and old (30 mo) male Fischer 344 x Brown Norway F1 hybrid rats. A measure of stiffness, i.e., apparent elastic modulus, was determined by analyzing the relationship between AFM indentation force and depth with the classical infinitesimal strain theory and by modeling the AFM probe as a blunted conical indenter. This is the first study to demonstrate a significant increase (P < 0.01) in the apparent elastic modulus of single, aging cardiac myocytes (from 35.1 +/- 0.7, n = 53, to 42.5 +/- 1.0 kPa, n = 58), supporting the novel concept that the mechanism mediating LV diastolic dysfunction in aging hearts resides, in part, at the level of the myocyte.

  3. The importance of correcting for variable probe-sample interactions in AFM-IR spectroscopy: AFM-IR of dried bacteria on a polyurethane film.

    PubMed

    Barlow, Daniel E; Biffinger, Justin C; Cockrell-Zugell, Allison L; Lo, Michael; Kjoller, Kevin; Cook, Debra; Lee, Woo Kyung; Pehrsson, Pehr E; Crookes-Goodson, Wendy J; Hung, Chia-Suei; Nadeau, Lloyd J; Russell, John N

    2016-08-01

    AFM-IR is a combined atomic force microscopy-infrared spectroscopy method that shows promise for nanoscale chemical characterization of biological-materials interactions. In an effort to apply this method to quantitatively probe mechanisms of microbiologically induced polyurethane degradation, we have investigated monolayer clusters of ∼200 nm thick Pseudomonas protegens Pf-5 bacteria (Pf) on a 300 nm thick polyether-polyurethane (PU) film. Here, the impact of the different biological and polymer mechanical properties on the thermomechanical AFM-IR detection mechanism was first assessed without the additional complication of polymer degradation. AFM-IR spectra of Pf and PU were compared with FTIR and showed good agreement. Local AFM-IR spectra of Pf on PU (Pf-PU) exhibited bands from both constituents, showing that AFM-IR is sensitive to chemical composition both at and below the surface. One distinct difference in local AFM-IR spectra on Pf-PU was an anomalous ∼4× increase in IR peak intensities for the probe in contact with Pf versus PU. This was attributed to differences in probe-sample interactions. In particular, significantly higher cantilever damping was observed for probe contact with PU, with a ∼10× smaller Q factor. AFM-IR chemical mapping at single wavelengths was also affected. We demonstrate ratioing of mapping data for chemical analysis as a simple method to cancel the extreme effects of the variable probe-sample interactions. PMID:27403761

  4. AFM studies of semicrystalline polymer/inorganic nanocomposites

    NASA Astrophysics Data System (ADS)

    Strawhecker, Kenneth E.

    2002-01-01

    The aims of this work are to elucidate the effects of interaction strength on the crystallization of a polymer near an inorganic surface; connect filler induced polymer crystallinity with resulting property changes, especially for strongly interacting (i.e. hydrogen bonding) systems; and to devise atomic force microscopy (AFM) methods for probing the crystallinity and properties of polymer/layered silicate systems at the nanometer level. Three inorganically filled systems were studied: (1) poly(vinyl alcohol) (PVA), (2) poly(ethylene oxide) (PEO), and (3) polypropylene (PP). Since it has the strongest, interactions, the PVA system is investigated first. AFM is used in conjunction with x-ray diffraction and differential scanning calorimetry (DSC) to show that strong polymer/filler interactions can promote a different crystalline structure and a different morphology than those seen in the bulk. The study then proceeds to the weakly interacting PEO/inorganic system where it is found that the inorganic layers disrupt crystalline morphology, but do not change the crystal structure. Furthermore, crystallization always occurs in volumes away from the inorganic filler. The third system (neutral interactions), PP/inorganic is then discussed. The three systems are compared with each other, and is found that the crystalline morphology and structure is highly dependent upon the strength of interaction between the polymer and filler. Due to its far-reaching morphology changes, the strongly interacting system was chosen for property studies. The composite structure study revealed a coexistence of exfoliated and intercalated MMT layers, especially for low and moderate silicate loadings. The inorganic layers promote a new crystalline phase different than the one of the respective neat PVA, characterized by higher melting temperature and a different crystal structure. This new crystal phase reflects on the composite materials properties, which have mechanical, thermal, and water

  5. AFM CHARACTERIZATION OF RAMAN LASER INDUCED DAMAGE ON CDZNTECRYSTAL SURFACES

    SciTech Connect

    Teague, L.; Duff, M.

    2008-10-07

    High quality CdZnTe (or CZT) crystals have the potential for use in room temperature gamma-ray and X-ray spectrometers. Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. The presence of structural heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SPs) can have an impact on the detector performance. There is considerable need for reliable and reproducible characterization methods for the measurement of crystal quality. With improvements in material characterization and synthesis, these crystals may become suitable for widespread use in gamma radiation detection. Characterization techniques currently utilized to test for quality and/or to predict performance of the crystal as a gamma-ray detector include infrared (IR) transmission imaging, synchrotron X-ray topography, photoluminescence spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. In some cases, damage caused by characterization methods can have deleterious effects on the crystal performance. The availability of non-destructive analysis techniques is essential to validate a crystal's quality and its ability to be used for either qualitative or quantitative gamma-ray or X-ray detection. The work presented herein discusses the damage that occurs during characterization of the CZT surface by a laser during Raman spectroscopy, even at minimal laser powers. Previous Raman studies have shown that the localized annealing from tightly focused, low powered lasers results in areas of higher Te concentration on the CZT surface. This type of laser damage on the surface resulted in decreased detector performance which was most likely due to increased leakage current caused by areas of higher Te concentration. In this study

  6. Intrinsically high-Q dynamic AFM imaging in liquid with a significantly extended needle tip

    NASA Astrophysics Data System (ADS)

    Minary-Jolandan, Majid; Tajik, Arash; Wang, Ning; Yu, Min-Feng

    2012-06-01

    Atomic force microscope (AFM) probe with a long and rigid needle tip was fabricated and studied for high Q factor dynamic (tapping mode) AFM imaging of samples submersed in liquid. The extended needle tip over a regular commercially available tapping-mode AFM cantilever was sufficiently long to keep the AFM cantilever from submersed in liquid, which significantly minimized the hydrodynamic damping involved in dynamic AFM imaging of samples in liquid. Dynamic AFM imaging of samples in liquid at an intrinsic Q factor of over 100 and an operational frequency of over 200 kHz was demonstrated. The method has the potential to be extended to acquire viscoelastic material properties and provide truly gentle imaging of soft biological samples in physiological environments.

  7. Effect of tip mass on frequency response and sensitivity of AFM cantilever in liquid.

    PubMed

    Farokh Payam, Amir; Fathipour, Morteza

    2015-03-01

    The effect of tip mass on the frequency response and sensitivity of atomic force microscope (AFM) cantilever in the liquid environment is investigated. For this purpose, using Euler-Bernoulli beam theory and considering tip mass and hydrodynamic functions in a liquid environment, an expression for the resonance frequencies of AFM cantilever in liquid is derived. Then, based on this expression, the effect of the surface contact stiffness on the flexural mode of a rectangular AFM cantilever in fluid is investigated and compared with the case where the AFM cantilever operates in the air. The results show that in contrast with an air environment, the tip mass has no significant impact on the resonance frequency and sensitivity of the AFM cantilever in the liquid. Hence, analysis of AFM behaviour in liquid environment by neglecting the tip mass is logical. PMID:25562584

  8. UV laser ablation of intraocular lenses: SEM and AFM microscopy examination of the biomaterial surface

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Asproudis, I.; Tsoutsi, D.; Bacharis, C.; Moutsouris, K.; Makropoulou, M.; Serafetinides, A. A.

    2010-02-01

    Several new materials and patterns are studied for the formation and etching of intraocular lenses (IOLs), in order to improve their optical properties, to reduce the diffractive aberrations and to decrease the incidence of posterior capsular opacification. The aim of this study is to investigate the use of UV ( λ = 266 nm) laser pulses to ablate the intraocular lenses materials, and thus to provide an alternative to conventional surface shaping techniques for IOLs fabrication. Ablation experiments were conducted using various polymer substrates of hydrophobic acrylic IOLs and PMMA IOLs. We investigated the ablation efficiency and the morphology of the ablated area by imaging the surface modification with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The morphological appearance of IOL samples reveals the effect of a photochemical and photothermal ablation mechanism.

  9. Conductive-probe AFM characterization of graphene sheets bonded to gold surfaces

    NASA Astrophysics Data System (ADS)

    Hauquier, Fanny; Alamarguy, David; Viel, Pascal; Noël, Sophie; Filoramo, Arianna; Huc, Vincent; Houzé, Frédéric; Palacin, Serge

    2012-01-01

    Conducting probe atomic force microscopy (CP-AFM) has been used to perform mechanical and electrical experiments on graphene layers bonded to polyaminophenylene (PAP) films grafted on gold substrates. This technique is a new approach for the characterization of graphene sheets and represents a complementary tool to Raman spectroscopy. The combination of friction and electrical imaging reveals that different stacked graphene sheets have been successfully distinguished from each other and from the underlying PAP films. Lateral force microscopy has shown that the friction is greatly reduced on graphene sheets in comparison with the organic coating. The electrical resistance images show very different local conduction properties which can be linked to the number of underlying graphene sheets. The resistance decreases very slowly when the normal load increases. Current-voltage curves display characteristics of metal-molecule-metal junctions.

  10. Characterization of mineral-associated organic matter: a combined approach of AFM and NanoSIMS

    NASA Astrophysics Data System (ADS)

    Pohl, Lydia; Schurig, Christian; Eusterhues, Karin; Mueller, Carsten W.; Höschen, Carmen; Totsche, Kai-Uwe; Kögel-Knabner, Ingrid

    2016-04-01

    The heterogeneous spatial distribution and amount of organic matter (OM) in soils, especially at the micro- or submicron-scale, has major consequences for the soil microstructure and for the accessibility of OM to decomposing microbial communities. Processes occurring at the microscale control soil properties and processes at larger scales, such as macro-aggregation and carbon turnover. Since OM acts as substrate and most important driver for biogeochemical processes, particular attention should be paid to its spatial interaction with soil minerals. In contrast to bulk analysis, Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS) offers the possibility to examine the composition and spatial distribution of OM within the intact organo-mineral matrix. Nevertheless, the yield of secondary electrons is influenced by the individual topography of the analysed particles, which aggravated the quantitative interpretation of the data. A combination of NanoSIMS and Atomic Force Microscopy (AFM), enabled us to visualize and quantify the topographical features of individual particles and correct the NanoSIMS data for this effect. We performed adsorption experiments with water-soluble soil OM in 6 concentration steps, which was extracted from forest floor layer of a Podzol, and adsorbed to illite. Upon the end of the sorption experiments the liquid phase and the solid phase were separated and the carbon content was analysed with TOC- and C/N-measurement, respectively. For the spatially resolved analyses, the samples were applied as thin layers onto silicon wafers and individual particles were chosen by means of the AFM. Subsequently, the identical particles were analysed with NanoSIMS to investigate the distribution of C, N, O, Si, P and Al. The recorded data were analysed for differences in elemental distribution between the different concentration steps. Additionally, we performed a correlation of the detectable counts with the topography of the particle within one

  11. BOREAS AFM-04 Twin Otter Aircraft Sounding Data

    NASA Technical Reports Server (NTRS)

    MacPherson, J. Ian; Desjardins, Raymond L.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-4 team used the National Research Council, Canada (NRC) Twin Otter aircraft to make sounding measurements through the boundary layer. These measurements included concentrations of carbon dioxide and ozone, atmospheric pressure, dry bulb temperature, potential temperature, dewpoint temperature, calculated mixing ratio, and wind speed and direction. Aircraft position, heading, and altitude were also recorded. Data were collected at both the Northern Study Area (NSA) and the Southern Study Area (SSA) in 1994 and 1996. These data are stored in tabular ASCII files. The Twin Otter aircraft sounding data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files also are available on a CD-ROM (see document number 20010000884).

  12. Visualization of internal structure of banana starch granule through AFM.

    PubMed

    Peroni-Okita, Fernanda H G; Gunning, A Patrick; Kirby, Andrew; Simão, Renata A; Soares, Claudinéia A; Cordenunsi, Beatriz R

    2015-09-01

    Atomic force microscopy (AFM) is a high resolution technique for studying the external and internal structures of starch granules. For this purpose granules were isolated from bananas and embedded in a non-penetrating resin. To achieve image contrast of the ultrastructure, the face of the cut blocks were wetted in steam and force modulation mode imaging was used. Images of starch from green bananas showed large variation of height across the granule due to a locational specific absorption of water and swelling of amorphous regions; the data reveal that the center of the granules are structurally different and have different viscoelastic properties. Images of starches from ripe bananas showed an even greater different level of organization: absence of growth rings around the hilum; the central region of the granule is richer in amylose; very porous surface with round shaped dark structures; the size of blocklets are larger than the green fruits. PMID:26005137

  13. AFM of self-assembled lambda DNA-histone networks.

    PubMed

    Liu, YuYing; Guthold, Martin; Snyder, Matthew J; Lu, HongFeng

    2015-10-01

    Atomic force microscopy (AFM) was used to investigate the self-assembly behavior of λ-DNA and histones at varying histone:DNA ratios. Without histones and at the lowest histone:DNA ratio (less than one histone per 1000 base pairs of DNA), the DNA appeared as individual (uncomplexed), double-stranded DNA molecules. At increasing histone concentrations (one histone per 500, 250 and 167 base pairs of DNA), the DNA molecules started to form extensive polygonal networks of mostly pentagons and hexagons. The observed networks might be one of the naturally occurring, stable DNA-histone structures. The condensing effects of the divalent cations Mg(2+) and Ca(2+) on the DNA-histone complexes were also investigated. The networks persisted at high Mg(2+) concentration (20mM) and the highest histone concentration. At high Ca(2+) concentration and the highest histone concentration, the polygonal network disappeared and, instead, individual, tightly condensed aggregates were formed. PMID:26141439

  14. Modeling AFM Induced Mechanical Deformation of Living Cells

    SciTech Connect

    Rudd, R E; McElfresh, M; Balhorn, R; Allen, M J; Belak, J

    2002-11-15

    Finite element modeling has been applied to study deformation of living cells in Atomic Force Microscopy (AFM) and particularly Recognition Force Microscopy (RFM). The abstract mechanical problem of interest is the response to RFM point loads of an incompressible medium enclosed in a fluid membrane. Cells are soft systems, susceptible to large deformations in the course of an RFM measurement. Often the local properties such as receptor anchoring forces, the reason for the measurement, are obscured by the response of the cell as a whole. Modeling can deconvolute these effects. This facilitates experimental efforts to have reproducible measurements of mechanical and chemical properties at specific kinds of receptor sites on the membrane of a living cell. In this article we briefly review the RFM technique for cells and the problems it poses, and then report on recent progress in modeling the deformation of cells by a point load.

  15. AFM tip effect on a thin liquid film.

    PubMed

    Ledesma-Alonso, R; Legendre, D; Tordjeman, Ph

    2013-06-25

    We study the interaction between an AFM probe and a liquid film deposited over a flat substrate. We investigate the effects of the physical and geometrical parameters, with a special focus on the film thickness E, the probe radius R, and the distance D between the probe and the free surface. Deformation profiles have been calculated from the numerical simulations of the Young-Laplace equation by taking into account the probe/liquid and the liquid/substrate interactions, characterized by the Hamaker constants, Hpl and Hls. We demonstrate that the deformation of a shallow film is determined by a particular characteristic length λF = (2πγE(4)/Hls)(1/2), resulting from the balance between the capillary force (γ is the surface tension) and the van der Waals liquid/substrate attraction. For the case of a bulk liquid, the extent of the interface deformation is simply controlled by the capillary length λC = (γ/Δρg)(1/2). These trends point out two asymptotic regimes, which in turn are bounded by two characteristic film thicknesses Eg = (Hls/2πΔρg)(1/4) and Eγ = (R(2)Hls/2πγ)(1/4). For E > Eg, the bulk behavior is recovered, and for E < Eγ, we show the existence of a particular shallow film regime in which a localized tip effect is observed. This tip effect is characterized by the small magnitude of the deformation and an important restriction of its radial extent λF localized below the probe. In addition, we have found that the film thickness has a significant effect on the threshold separation distance Dmin below which the irreversible jump-to-contact process occurs: Dmin is probe radius-dependent for the bulk whereas it is film-thickness-dependent for shallow films. These results have an important impact on the optimal AFM scanning conditions. PMID:23721486

  16. Effect of Strain Rate on Deformation Behavior of AlCoCrFeNi High-Entropy Alloy by Nanoindentation

    NASA Astrophysics Data System (ADS)

    Tian, L.; Jiao, Z. M.; Yuan, G. Z.; Ma, S. G.; Wang, Z. H.; Yang, H. J.; Zhang, Y.; Qiao, J. W.

    2016-06-01

    In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the Al x CoCrFeNi ( x = 0.3,0.5) at the strain rate of 0.2 s-1 due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively.

  17. Effects of brushing timing after erosive challenge on enamel loss in situ: White light interferometer and nanoindentation study.

    PubMed

    Tsuda, Yuka; Kitasako, Yuichi; Sadr, Alireza; Nakashima, Syozi; Tagami, Junji

    2016-01-01

    This in situ study aimed to evaluate effects of waiting periods after erosive challenge before toothbrushing on enamel abrasion and nanoindentation hardness. Ten subjects wore intraoral appliances each with a set of 4 bovine enamel blocks. The enamel blocks were subjected to 2 cycles a day for 3 days as follows; intraoral exposure to form acquired pellicle and extraoral erosion followed by either 0, 3, 30 or 60 min intraoral exposure and then brushing, which was performed using an automatic brushing machine. Abrasive loss was assessed by white light interferometry. Nanoindentation was performed to calculate relative hardness. Abrasion and relative hardness were statistically analyzed by ANOVA. Abrasive loss was significantly less in groups exposed to saliva compared with 0 min (p<0.05); there was no significant difference between 30 and 60 min (p>0.05). Relative hardness was statistically higher after intraoral exposure, but no differences existed among any intraoral exposure periods (p>0.05). PMID:27477227

  18. Heavy-ion irradiation defect accumulation in ZrN characterized by TEM, GIXRD, nanoindentation, and helium desorption

    NASA Astrophysics Data System (ADS)

    Egeland, G. W.; Valdez, J. A.; Maloy, S. A.; McClellan, K. J.; Sickafus, K. E.; Bond, G. M.

    2013-04-01

    A study on zirconium nitride was performed to assess the effect of radiation damage by heavy ions at cryogenic and elevated temperatures. Cross-sectional transmission electron microscopy, grazing incidence X-ray diffraction, nanoindentation, and helium desorption studies were used to assess the damage and its effects. Xenon and krypton were used as heavy ions at 300 keV to displacement damage as high as 200 dpa. Implants were cryogenic, 350 °C, 580 °C, and 800 °C. Amorphization was not observed at low temperatures nor was bubble formation observed at elevated temperatures, however, defect migration was observed at elevated temperatures. Nanoindenter results showed the onset of defect saturation. Helium release studies were performed to show the effect of increasing damage by Xe to 40 dpa.

  19. Effects of brushing timing after erosive challenge on enamel loss in situ: White light interferometer and nanoindentation study.

    PubMed

    Tsuda, Yuka; Kitasako, Yuichi; Sadr, Alireza; Nakashima, Syozi; Tagami, Junji

    2016-01-01

    This in situ study aimed to evaluate effects of waiting periods after erosive challenge before toothbrushing on enamel abrasion and nanoindentation hardness. Ten subjects wore intraoral appliances each with a set of 4 bovine enamel blocks. The enamel blocks were subjected to 2 cycles a day for 3 days as follows; intraoral exposure to form acquired pellicle and extraoral erosion followed by either 0, 3, 30 or 60 min intraoral exposure and then brushing, which was performed using an automatic brushing machine. Abrasive loss was assessed by white light interferometry. Nanoindentation was performed to calculate relative hardness. Abrasion and relative hardness were statistically analyzed by ANOVA. Abrasive loss was significantly less in groups exposed to saliva compared with 0 min (p<0.05); there was no significant difference between 30 and 60 min (p>0.05). Relative hardness was statistically higher after intraoral exposure, but no differences existed among any intraoral exposure periods (p>0.05).

  20. An in vitro study of the microstructure, composition and nanoindentation mechanical properties of remineralizing human dental enamel

    NASA Astrophysics Data System (ADS)

    Arsecularatne, J. A.; Hoffman, M.

    2014-08-01

    This paper describes the results of an in vitro investigation on the interrelations among microstructure, composition and mechanical properties of remineralizing human dental enamel. Polished enamel samples have been demineralized for 10 min in an acetic acid solution (at pH 3) followed by remineralization in human saliva for 30 and 120 min. Microstructure variations of sound, demineralized and remineralized enamel samples have been analysed using focused ion beam, scanning electron microscopy and transmission electron microscopy, while their compositions have been analysed using energy dispersive x-ray. Variations in the mechanical properties of enamel samples have been assessed using nanoindentation. The results reveal that, under the selected conditions, only partial remineralization of the softened enamel surface layer occurs where some pores remain unrepaired. As a result, while the nanoindentation elastic modulus shows an improvement following remineralization, hardness does not.

  1. Characterization Of Multi-layered Fish Scales (Atractosteus spatula) Using Nanoindentation, X-ray CT, FTIR, and SEM

    PubMed Central

    Allison, Paul G.; Rodriguez, Rogie I.; Moser, Robert D.; Williams, Brett A.; Poda, Aimee R.; Seiter, Jennifer M.; Lafferty, Brandon J.; Kennedy, Alan J.; Chandler, Mei Q.

    2014-01-01

    The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram’s horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6. However, a well-defined standard procedure for specimen preparation of mineralized biomaterials is not currently available. In this study, the methods for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of A. spatula using nanoindentation, FTIR, SEM, with energy-dispersive X-ray (EDX) microanalysis, and X-ray CT are presented. PMID:25046233

  2. Characterization of multi-layered fish scales (Atractosteus spatula) using nanoindentation, X-ray CT, FTIR, and SEM.

    PubMed

    Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Williams, Brett A; Poda, Aimee R; Seiter, Jennifer M; Lafferty, Brandon J; Kennedy, Alan J; Chandler, Mei Q

    2014-07-10

    The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram's horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6. However, a well-defined standard procedure for specimen preparation of mineralized biomaterials is not currently available. In this study, the methods for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of A. spatula using nanoindentation, FTIR, SEM, with energy-dispersive X-ray (EDX) microanalysis, and X-ray CT are presented.

  3. Deformation behaviour and 6H-LPSO structure formation at nanoindentation in lamellar high Nb containing TiAl alloy

    NASA Astrophysics Data System (ADS)

    Song, L.; Xu, X. J.; Peng, C.; Wang, Y. L.; Liang, Y. F.; Shang, S. L.; Liu, Z. K.; Lin, J. P.

    2015-02-01

    Microstructure and deformation mechanisms at a nanoindentation in the lamellar colony of high Nb containing TiAl alloy have been studied using the focused ion beam and the transmission electron microscopy. Considerable deformation twins are observed around the nanoindentation, and a strain gradient is generated. A continuous change in the bending angle of the lamellar structure can be derived, and a strain-induced grain refinement process is observed as various active deformations split the γ grains into subgrains. In addition to all possible deformation mechanisms (ordinary dislocation, super-dislocation and deformation twining) activated due to the heavy plastic deformation, a 6-layer hexagonal (6H) long-period stacking ordered structure is identified for the first time near the contact zone and is thought to be closely related to the glide of partial dislocations.

  4. Characterization of multi-layered fish scales (Atractosteus spatula) using nanoindentation, X-ray CT, FTIR, and SEM.

    PubMed

    Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Williams, Brett A; Poda, Aimee R; Seiter, Jennifer M; Lafferty, Brandon J; Kennedy, Alan J; Chandler, Mei Q

    2014-01-01

    The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram's horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6. However, a well-defined standard procedure for specimen preparation of mineralized biomaterials is not currently available. In this study, the methods for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of A. spatula using nanoindentation, FTIR, SEM, with energy-dispersive X-ray (EDX) microanalysis, and X-ray CT are presented. PMID:25046233

  5. Plasticity and ultra-low stress induced twin boundary migration in nanotwinned Cu by in situ nanoindentation studies

    SciTech Connect

    Liu, Y.; Chen, Y.; Jian, J.; Wang, H.; Zhang, X.

    2014-06-09

    Nanotwinned metals have rare combinations of mechanical strength and ductility. Previous studies have shown that detwinning occurs in plastically deformed nanotwinned metals. Although molecular dynamics simulations have predicted that fine nanotwins can migrate at low stress, there is little in situ evidence to validate such predictions. Also it is unclear if detwinning occurs prior to or succeeding plastic yielding. Here, by using in situ nanoindentation in a transmission electron microscope, we show that a non-elastic detwinning process in nanotwinned Cu occurred at ultra-low indentation stress (0.1 GPa), well before the stress necessary for plastic yielding. Furthermore, the in situ nanoindentation technique allows us to differentiate dislocation-nucleation dominated microscopic yielding preceding macroscopic yielding manifested by dislocation-transmission through twin boundaries. This study thus provides further insights for understanding plasticity in nanotwinned metals at microscopic levels.

  6. Nano-indentation of single-layer optical oxide thin films grown by electron-beam deposition

    SciTech Connect

    Mehrotra, K.; Oliver, J. B.; Lambropoulos, J. C.

    2015-01-01

    Mechanical characterization of optical oxide thin films is performed using nano-indentation, and the results are explained based on the deposition conditions used. These oxide films are generally deposited to have a porous microstructure that optimizes laser induced damage thresholds, but changes in deposition conditions lead to varying degrees of porosity, density, and possibly the microstructure of the thin film. This can directly explain the differences in the mechanical properties of the film studied here and those reported in literature. Of the four single-layer thin films tested, alumina was observed to demonstrate the highest values of nano-indentation hardness and elastic modulus. This is likely a result of the dense microstructure of the thin film arising from the particular deposition conditions used.

  7. Grain Growth Orientation and Anisotropy in Cu6Sn5 Intermetallic: Nanoindentation and Electron Backscatter Diffraction Analysis

    NASA Astrophysics Data System (ADS)

    Choudhury, Soud Farhan; Ladani, Leila

    2014-04-01

    As the size of joints in micro/nano-electronics diminishes, the role of intermetallic (IMC) layers becomes more significant. It was shown that solder joint strength is controlled largely by IMC strength at higher strain rates. Additionally, there is a possibility that very small joints are completely composed of IMCs. Further miniaturization of joints may result in statistical grain size effects. Therefore, it is essential to characterize IMC materials and understand their anisotropic mechanical properties. One of the most common types of IMCs in microelectronic joints is Cu6Sn5, which is formed in a variety of bonding materials with different compositions of Sn, Cu, and Ag. This work studies through nanoindentation elastic-plastic properties of a single grain of Cu6Sn5 IMC in a Sn-3.5Ag/Cu system with reflow soldering. Elastic properties such as elastic modulus and hardness were determined from the nanoindentation load-depth curve. The reverse analysis model described by Dao et al. was used to extract plastic properties such as yield strength and strain hardening exponent from nanoindentation data. Care was taken to achieve indentation of single grains with sufficient accuracy and repeatability. Electron backscatter diffraction (EBSD) mapping was used to determine orientation of Cu6Sn5 grains and to relate the orientation with the load-depth curve results of nanoindentation and the corresponding elastic and plastic properties. The EBSD results indicated that the Cu6Sn5 crystal structure is hexagonal. Columnar growth of the Cu6Sn5 grains was observed as the grains mostly grew along the c-axis of the crystal. Indentation of different grains parallel to the basal plane showed no significant difference in mechanical properties.

  8. Hierarchical super-structure identified by polarized light microscopy, electron microscopy and nanoindentation: Implications for the limits of biological control over the growth mode of abalone sea shells

    PubMed Central

    2012-01-01

    Background Mollusc shells are commonly investigated using high-resolution imaging techniques based on cryo-fixation. Less detailed information is available regarding the light-optical properties. Sea shells of Haliotis pulcherina were embedded for polishing in defined orientations in order to investigate the interface between prismatic calcite and nacreous aragonite by standard materialographic methods. A polished thin section of the interface was prepared with a defined thickness of 60 μm for quantitative birefringence analysis using polarized light and LC-PolScope microscopy. Scanning electron microscopy images were obtained for comparison. In order to study structural-mechanical relationships, nanoindentation experiments were performed. Results Incident light microscopy revealed a super-structure in semi-transparent regions of the polished cross-section under a defined angle. This super-structure is not visible in transmitted birefringence analysis due to the blurred polarization of small nacre platelets and numerous organic interfaces. The relative orientation and homogeneity of calcite prisms was directly identified, some of them with their optical axes exactly normal to the imaging plane. Co-oriented "prism colonies" were identified by polarized light analyses. The nacreous super-structure was also visualized by secondary electron imaging under defined angles. The domains of the super-structure were interpreted to consist of crystallographically aligned platelet stacks. Nanoindentation experiments showed that mechanical properties changed with the same periodicity as the domain size. Conclusions In this study, we have demonstrated that insights into the growth mechanisms of nacre can be obtained by conventional light-optical methods. For example, we observed super-structures formed by co-oriented nacre platelets as previously identified using X-ray Photo-electron Emission Microscopy (X-PEEM) [Gilbert et al., Journal of the American Chemical Society 2008, 130

  9. Cyclic nanoindentation studies on CrN thin films prepared by RF sputtering on Zr-based metallic glass

    SciTech Connect

    Jellad, A.; Benameur, T.; Labdi, S.

    2011-01-17

    Cyclic nanoindentation tests were carried out to study the influence of the chromium nitride thin films on the mechanical properties of Zr-based metallic glass. Chromium nitride thin coatings have been deposited on Zr{sub 50}Cu{sub 40}Al{sub 10} metallic glass substrate by RF sputtering. The deposition process was done at room temperature under nitrogen reactive gas using a metallic chromium target. The CrN films have a thickness of 300 nm. Several cyclic nanoindentation measurements were conducted on CrN films and Zr{sub 50}Cu{sub 40}Al{sub 10} metallic glass substrate samples at various loading rate values. We have found that the coated metallic glass sample shows high mechanical properties such as hardness and reduced elastic modulus. Cyclic nanoindentation results show a hardening behaviour for these CrN coatings. Moreover, the CrN coated on Zr-based metallic glass was found to have a high value of resistance to crack propagation, as being analysed through the SEM pictures of the residual Vickers indentation impressions.

  10. Effects of water molecules on tribological behavior and property measurements in nano-indentation processes - a numerical analysis

    PubMed Central

    2013-01-01

    Nano/micro-manufacturing under wet condition is an important consideration for various tool-based processes such as indentation, scratching, and machining. The existence of liquids adds complexity to the system, changes the tool/work interfacial condition, and affects material behaviors. For indentation, it may also affect material property measurements. However, little effort has been made to study this challenging issue at nano- or atomistic scale. In this study, we tackle this challenge by investigating nano-indentation processes submerged in water using the molecular dynamics (MD) simulation approach. Compared with dry indentation in which no water molecules are present, the existence of water molecules causes the increase of indentation force in initial penetration, but the decrease of indentation force in full penetration. It also reduces the sticking phenomenon between the work and tool atoms during indenter retraction, such that the indentation geometry can be better retained. Meanwhile, nano-indentation under wet condition exhibits the indentation size effect, while dry nano-indentation exhibits the reverse indentation size effect. The existence of water leads to higher computed hardness values at low indentation loads and a smaller value of Young's modulus. In addition, the friction along the tool/work interface is significantly reduced under wet indentation. PMID:24044504

  11. Oscillatory structural forces due to nonionic surfactant micelles: data by colloidal-probe AFM vs theory.

    PubMed

    Christov, Nikolay C; Danov, Krassimir D; Zeng, Yan; Kralchevsky, Peter A; von Klitzing, Regine

    2010-01-19

    Micellar solutions of nonionic surfactants Brij 35 and Tween 20 are confined between two surfaces in a colloidal-probe atomic-force microscope (CP-AFM). The experimentally detected oscillatory forces due to the layer-by-layer expulsion of the micelles agree very well with the theoretical predictions for hard-sphere fluids. While the experiment gives parts of the stable branches of the force curve, the theoretical model allows reconstruction of the full oscillatory curve. Therewith, the strength and range of the ordering could be determined. The resulting aggregation number from the fits of the force curves for Brij 35 is close to 70 and exhibits a slight tendency to increase with the surfactant concentration. The last layer of micelles cannot be pressed out. The measured force-vs-distance curve has nonequilibrium portions, which represent "jumps" from one to another branch of the respective equilibrium oscillatory curve. In the case of Brij 35, at concentrations <150 mM spherical micelles are present and the oscillation period is close to the micelle diameter, slightly decreasing with the rise of concentration. For elongated micelles (at concentration 200 mM), no harmonic oscillations are observed anymore; instead, the period increases with the decrease of film thickness. In the case of Tween 20, the force oscillations are almost suppressed, which implies that the micelles of this surfactant are labile and are demolished by the hydrodynamic shear stresses due to the colloidal-probe motion. The comparison of the results for the two surfactants demonstrates that in some cases the micelles can be destroyed by the CP-AFM, but in other cases they can be stable and behave as rigid particles. This behavior correlates with the characteristic times of the slow micellar relaxation process for these surfactants.

  12. Nanoindentation of lemur enamel: an ecological investigation of mechanical property variations within and between sympatric species.

    PubMed

    Campbell, Sara E; Cuozzo, Frank P; Sauther, Michelle L; Sponheimer, Matt; Ferguson, Virginia L

    2012-06-01

    The common morphological metrics of size, shape, and enamel thickness of teeth are believed to reflect the functional requirements of a primate's diet. However, the mechanical and material properties of enamel also contribute to tooth function, yet are rarely studied. Substantial wear and tooth loss previously documented in Lemur catta at the Beza Mahafaly Special Reserve suggests that their dental morphology, structure, and possibly their enamel are not adapted for their current fallback food (the mechanically challenging tamarind fruit). In this study, we investigate the nanomechanical properties, mineralization, and microstructure of the enamel of three sympatric lemur species to provide insight into their dietary functional adaptations. Mechanical properties measured by nanoindentation were compared to measurements of mineral content, prism orientation, prism size, and enamel thickness using electron microscopy. Mechanical properties of all species were similar near the enamel dentin junction and variations correlated with changes in microstructure (e.g., prism size) and mineral content. Severe wear and microcracking within L. catta's enamel were associated with up to a 43% reduction in nanomechanical properties in regions of cracking versus intact enamel. The mechanical and material properties of L. catta's enamel are similar to those of sympatric folivores and suggest that they are not uniquely mechanically adapted to consume the physically challenging tamarind fruit. An understanding of the material and mechanical properties of enamel is required to fully elucidate the functional and ecological adaptations of primate teeth.

  13. Activation energy of the low-load NaCl transition from nanoindentation loading curves.

    PubMed

    Kaupp, Gerd

    2014-01-01

    Access to activation energies E(a) of phase transitions is opened by unprecedented analyses of temperature dependent nanoindentation loading curves. It is based on kinks in linearized loading curves, with additional support by coincidence of kink and electrical conductivity of silicon loading curves. Physical properties of B1, B2, NaCl and further phases are discussed. The normalized low-load transition energy of NaCl (Wtrans/µN) increases with temperature and slightly decreases with load. Its semi-logarithmic plot versus T obtains activation energy E(a)/µN for calculation of the transition work for all interesting temperatures and pressures. Arrhenius-type activation energy (kJ/mol) is unavailable for indentation phase transitions. The E(a) per load normalization proves insensitive to creep-on-load, which excludes normalization to depth or volume for large temperature ranges. Such phase transition E(a)/µN is unprecedented material's property and will be of practical importance for the compatibility of composite materials under impact and further shearing interactions at elevated temperatures.

  14. Universal scaling laws for homogeneous dislocation nucleation during nano-indentation

    NASA Astrophysics Data System (ADS)

    Garg, Akanksha; Maloney, Craig E.

    2016-10-01

    We perform atomistic simulations to study the mechanism of homogeneous dislocation nucleation in two dimensional (2D) hexagonal crystals during nanoindentation with a circular indenter of radius R. We study both a realistic embedded atom method (EAM) potential for Al in addition to simple pair-wise potentials: Lennard-Jones, Morse, and Hookean springs. The nucleation process is governed by the vanishing of the energy associated with a single energy eigenmode. The critical eigenmode, or dislocation embryo, is found to be localized along a line (or plane in 3D) of atoms with a lateral extent, ξ, at some depth, Y*, below the surface. For all interatomic potentials, the scaled critical load, Fc / R, and scaled critical contact length, Cc / R, decrease to R-independent values in the limit of large R. However, ξ / R and Y* / R display non-trivial scaling with R despite the R independence of Fc / R and Cc / R. We show that although both the interaction potential and the orientation of the lattice affect the prefactors in the scaling relations, all the scaling laws are robust. Furthermore, we show that a stability criterion proposed by Van Vliet et al. based on the minimum eigenvalue, Λ, of the local acoustic tensor predicts the location, orientation, and polarization of the dislocation embryo with a high degree of accuracy for all potentials and crystallographic orientations. However, we also show that, for all crystallographic orientations and interaction potentials, Λ erroneously indicates instability before the true instability occurs.

  15. In situ atomic force microscopy nanoindentation of lithiated silicon nanopillars for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    McAllister, Quinn P.; Strawhecker, Kenneth E.; Becker, Collin R.; Lundgren, Cynthia A.

    2014-07-01

    In this study, atomic force microscopy based nanoindentation techniques are used to measure the in situ mechanical properties of thin film, nanometer sized amorphous-silicon nanopillars (pillar diameters of 1000 nm, 500 nm, and 200 nm) at various stages of lithiation. The pillar indentation modulus and hardness are measured ex situ as-fabricated, in situ during lithiation at two different potentials (or stages of lithiation, 50 mV and 10 mV), and in situ after delithiation at 2 V. The measured modulus of the pristine amorphous silicon nanopillars was 74.7 ± 12.1 GPa. The hardness of the pristine pillars depended on depth and the contact conditions. In general, the mechanical properties of the nanopillars decreased with increased degrees of lithiation and only partially recovered upon delithiation. The inability of the silicon to recover the as fabricated mechanical properties indicates overall degradation of the pillar during only one lithiation-delithiation cycle, which could only be directly measured in situ using the employed atomic force microscopy based technique.

  16. Nanoindentation study of the mechanical behavior of TiO{sub 2} nanotube arrays

    SciTech Connect

    Xu, Y. N.; Wang, M. C.; Oloyede, A.; Bell, J. M.; Yan, C.; Liu, M. N.

    2015-10-14

    Titanium dioxide (TiO{sub 2}) nanotube arrays are attracting increasing attention for use in solar cells, lithium-ion batteries, and biomedical implants. To take full advantage of their unique physical properties, such arrays need to maintain adequate mechanical integrity in applications. However, the mechanical performance of TiO{sub 2} nanotube arrays is not well understood. In this work, we investigate the deformation and failure of TiO{sub 2} nanotube arrays using the nanoindentation technique. We found that the load–displacement response of the arrays strongly depends on the indentation depth and indenter shape. Substrate-independent elastic modulus and hardness can be obtained when the indentation depth is less than 2.5% of the array height. The deformation mechanisms of TiO{sub 2} nanotube arrays by Berkovich and conical indenters are closely associated with the densification of TiO{sub 2} nanotubes under compression. A theoretical model for deformation of the arrays under a large-radius conical indenter is also proposed.

  17. Nanoindentation study of the mechanical behavior of TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Xu, Y. N.; Liu, M. N.; Wang, M. C.; Oloyede, A.; Bell, J. M.; Yan, C.

    2015-10-01

    Titanium dioxide (TiO2) nanotube arrays are attracting increasing attention for use in solar cells, lithium-ion batteries, and biomedical implants. To take full advantage of their unique physical properties, such arrays need to maintain adequate mechanical integrity in applications. However, the mechanical performance of TiO2 nanotube arrays is not well understood. In this work, we investigate the deformation and failure of TiO2 nanotube arrays using the nanoindentation technique. We found that the load-displacement response of the arrays strongly depends on the indentation depth and indenter shape. Substrate-independent elastic modulus and hardness can be obtained when the indentation depth is less than 2.5% of the array height. The deformation mechanisms of TiO2 nanotube arrays by Berkovich and conical indenters are closely associated with the densification of TiO2 nanotubes under compression. A theoretical model for deformation of the arrays under a large-radius conical indenter is also proposed.

  18. Evaluating fundamental position-dependent differences in wood cell wall adhesion using nanoindentation

    PubMed Central

    Obersriebnig, Michael; Konnerth, Johannes; Gindl-Altmutter, Wolfgang

    2013-01-01

    Spruce wood specimens were bonded with one-component polyurethane (PUR) and urea-formaldehyde (UF) adhesive, respectively. The adhesion of the adhesives to the wood cell wall was evaluated at two different locations by means of a new micromechanical assay based on nanoindentation. One location tested corresponded to the interface between the adhesive and the natural inner cell wall surface of the secondary cell wall layer 3 (S3), whereas the second location corresponded to the interface between the adhesive and the freshly cut secondary cell wall layer 2 (S2). Overall, a trend towards reduced cell wall adhesion was found for PUR compared to UF. Position-resolved examination revealed excellent adhesion of UF to freshly cut cell walls (S2) but significantly diminished adhesion to the inner cell wall surface (S3). In contrast, PUR showed better adhesion to the inner cell wall surface and less adhesion to freshly cut cell walls. Atomic force microscopy revealed a less polar character for the inner cell wall surface (S3) compared to freshly cut cell walls (S2). It is proposed that differences in the polarity of the used adhesives and the surface chemistry of the two cell wall surfaces examined account for the observed trends. PMID:27570321

  19. Nanoindentation hardness and elastic modulus of nano-grained titanium produced by asymmetric and symmetric rolling.

    PubMed

    Li, Zhiming; Fu, Liming; Fu, Bin; Yang, Xiaoping; Shan, Aidang

    2014-10-01

    To understand the nanomechanical properties of nano-grained (NG) Ti produced by combination of asymmetric and symmetric rolling, nanoindentation hardness (H(n)) and elastic modulus (E(n)) of different planes within the NG Ti specimens were measured using continuous stiffness measurement mode at room temperature. For comparison, the nanomechanical properties of the as-received hot-rolled coarse-grained (CG) Ti and ultrafine-grained (UFG) Ti with only asymmetric rolling process were also investigated. It was found that H(n) of the Ti samples increased significantly with the decrease of grain sizes, while E(n) exhibited a slight decrease as the grain sizes decreased from CG to NG regime. The increase of H(n) was expected to be caused by higher density of dislocations and finer grains attained by severer plastic deformation, while the slight decrease of E(n) was considered as a result of the increased density of lattice defects and volume fraction of the grain boundary atoms. Furthermore, the nanomechanical properties of different planes of the Ti specimen exhibited a little difference which can be expressed as H(n(RD-TD)) > H(n(N-RD)) > H(n(TD-ND)) and E(n(RD-TD)) > E(n(ND-RD)) > E(n(TD-ND)). These differences were ascribed to crystallographic textures formed by rolling deformation.

  20. Microstructure and magnetic disorder induced by nanoindentation in single-crystalline Fe

    NASA Astrophysics Data System (ADS)

    Wang, Binjun; Gao, Yu; Urbassek, Herbert M.

    2014-03-01

    Using molecular dynamics simulation, we study nanoindentation into an Fe (100) surface. We use the so-called magnetic interaction potentials provided by Dudarev and Derlet [J. Phys.: Condens. Matter 17, 7097 (2005), 10.1088/0953-8984/17/44/003] and Chiesa et al. [J. Phys.: Condens. Matter 23, 206001 (2011), 10.1088/0953-8984/23/20/206001] in three different parametrizations; these allow us to extract information about the local magnetic moments from the molecular-dynamics simulation. Our simulations are performed at low temperature; the simulation cell is assumed to consist of a single ferromagnetic domain. Material hardness as well as the density of dislocations generated coincide satisfactorily with previous studies using conventional potentials. We observe the generation of both b =1/2<111> and b =<100> dislocations, which contribute to the plastic deformation. Besides dislocations, the induced microstructure features twins and vacancies. The local magnetic moments change considerably due to the strain field induced by the developing microstructure and assume values between 83 and 112% of the equilibrium bulk value in Fe. These changes are, however, quite localized and quickly decay away from the highly strained regions of dislocation cores.

  1. Nanoindentation of lemur enamel: an ecological investigation of mechanical property variations within and between sympatric species.

    PubMed

    Campbell, Sara E; Cuozzo, Frank P; Sauther, Michelle L; Sponheimer, Matt; Ferguson, Virginia L

    2012-06-01

    The common morphological metrics of size, shape, and enamel thickness of teeth are believed to reflect the functional requirements of a primate's diet. However, the mechanical and material properties of enamel also contribute to tooth function, yet are rarely studied. Substantial wear and tooth loss previously documented in Lemur catta at the Beza Mahafaly Special Reserve suggests that their dental morphology, structure, and possibly their enamel are not adapted for their current fallback food (the mechanically challenging tamarind fruit). In this study, we investigate the nanomechanical properties, mineralization, and microstructure of the enamel of three sympatric lemur species to provide insight into their dietary functional adaptations. Mechanical properties measured by nanoindentation were compared to measurements of mineral content, prism orientation, prism size, and enamel thickness using electron microscopy. Mechanical properties of all species were similar near the enamel dentin junction and variations correlated with changes in microstructure (e.g., prism size) and mineral content. Severe wear and microcracking within L. catta's enamel were associated with up to a 43% reduction in nanomechanical properties in regions of cracking versus intact enamel. The mechanical and material properties of L. catta's enamel are similar to those of sympatric folivores and suggest that they are not uniquely mechanically adapted to consume the physically challenging tamarind fruit. An understanding of the material and mechanical properties of enamel is required to fully elucidate the functional and ecological adaptations of primate teeth. PMID:22610894

  2. The application of nanoindentation for determination of cellulose nanofibrils (CNF) nanomechanical properties

    NASA Astrophysics Data System (ADS)

    Yildirim, N.; Shaler, S.

    2016-10-01

    Nanocellulose is a polymer which can be isolated from nature (woods, plants, bacteria, and from sea animals) through chemical or mechanical treatments, as cellulose nanofibrils (CNF), cellulose nanocrystals or bacterial celluloses. Focused global research activities have resulted in decreasing costs. A nascent industry of producers has created a huge market interest in CNF. However, there is still lack of knowledge on the nanomechanical properties of CNF, which create barriers for the scientist and producers to optimize and predict behavior of the final product. In this research, the behavior of CNF under nano compression loads were investigated through three different approaches, Oliver–Pharr (OP), fused silica (FS), and tip imaging (TI) via nanoindentation in an atomic force microscope. The CNF modulus estimates for the three approaches were 16.6 GPa, for OP, 15.8 GPa for FS, and 10.9 GPa for TI. The CNF reduced moduli estimates were consistently higher and followed the same estimate rankings by analysis technique (18.2, 17.4, and 11.9 GPa). This unique study minimizes the uncertainties related to the nanomechanical properties of CNFs and provides increased knowledge on understanding the role of CNFs as a reinforcing material in composites and also improvement in making accurate theoretical calculations and predictions.

  3. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    DOE PAGES

    Liu, Y.; Wang, H.; Zhang, X.

    2015-11-30

    Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentationmore » studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.« less

  4. Nanoindentations on conch shells of Gastropoda and Bivalvia molluscs reveal anisotropic evolution against external attacks.

    PubMed

    Bignardi, Cristina; Petraroli, Michele; Pugno, Nicola M

    2010-10-01

    Nanoindentation method has been used to explore, at the nanoscale, the mechanical properties of four different representative types of conch shells belonging to the two biggest classes of molluscs, Gastropoda and Bivalvia, in order to compare nanohardness and Young's modulus with respect to the microstructural anisotropic architectures. For the experimental tests a Nano Indenter XP (MTS Nano Instruments, Oak Ridge TN) has been used. The mechanical tests have been carried out on the inner and outer surfaces of the shells, as well as on their cross-section, near to the inner/outer surfaces and in the middle layer. The results confirm the three layered anisotropic architecture of the investigated conchs. On each of these 5 surfaces, 2 x 5 indentations have been performed at different maximum depth: from 250 nm to 4 microm, with a step of 250 nm, for a total of 3200 tests. The numerous observations have been analysed applying an ad hoc modification of the Weibull Statistics, suggesting a natural evolution of the shells against external attacks.

  5. Serrated flow behaviors of a Zr-based bulk metallic glass by nanoindentation

    SciTech Connect

    Cheng, L.; Jiao, Z. M.; Ma, S. G.; Wang, Z. H. E-mail: wangzhihua@tyut.edu.cn; Qiao, J. W. E-mail: wangzhihua@tyut.edu.cn

    2014-02-28

    Instrumented nanoindentation tests were used to investigate the mechanical properties of Zr{sub 52.5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10}Ti{sub 5} bulk metallic glass. The corresponding loading strain rates were ranged from 0.002 s{sup −1}, 0.02 s{sup −1} to 0.2 s{sup −1}. Plastic flow of this material exhibited remarkable serrations at low strain rates and increasingly became weakening until disappearance with increasing indentation strain rate, implying strong rate sensitivity. A significant pile-up around the indents was observed through atomic force microscopy, which suggested a highly localized plastic deformation. Mechanism governing the deformation was tentatively discussed in terms of the increasing process of free volume with a negligible temperature rise under low strain rate, which well explained the declining trend of elastic modulus and hardness with an increase of indentation depth.

  6. In vivo extraction of Arabidopsis cell turgor pressure using nanoindentation in conjunction with finite element modeling.

    PubMed

    Forouzesh, Elham; Goel, Ashwani; Mackenzie, Sally A; Turner, Joseph A

    2013-02-01

    Turgor pressure in plant cells is involved in many important processes. Stable and normal turgor pressure is required for healthy growth of a plant, and changes in turgor pressure are indicative of changes taking place within the plant tissue. The ability to quantify the turgor pressure of plant cells in vivo would provide opportunities to understand better the process of pressure regulation within plants, especially when plant stress is considered, and to understand the role of turgor pressure in cellular signaling. Current experimental methods do not separate the influence of the turgor pressure from the effects associated with deformation of the cell wall when estimates of turgor pressure are made. In this paper, nanoindentation measurements are combined with finite element simulations to determine the turgor pressure of cells in vivo while explicitly separating the cell-wall properties from the turgor pressure effects. Quasi-static cyclic tests with variable depth form the basis of the measurements, while relaxation tests at low depth are used to determine the viscoelastic material properties of the cell wall. Turgor pressure is quantified using measurements on Arabidopsis thaliana under three pressure states (control, turgid and plasmolyzed) and at various stages of plant development. These measurements are performed on cells in vivo without causing damage to the cells, such that pressure changes may be studied for a variety of conditions to provide new insights into the biological response to plant stress conditions.

  7. Nanoindentations on conch shells of Gastropoda and Bivalvia molluscs reveal anisotropic evolution against external attacks.

    PubMed

    Bignardi, Cristina; Petraroli, Michele; Pugno, Nicola M

    2010-10-01

    Nanoindentation method has been used to explore, at the nanoscale, the mechanical properties of four different representative types of conch shells belonging to the two biggest classes of molluscs, Gastropoda and Bivalvia, in order to compare nanohardness and Young's modulus with respect to the microstructural anisotropic architectures. For the experimental tests a Nano Indenter XP (MTS Nano Instruments, Oak Ridge TN) has been used. The mechanical tests have been carried out on the inner and outer surfaces of the shells, as well as on their cross-section, near to the inner/outer surfaces and in the middle layer. The results confirm the three layered anisotropic architecture of the investigated conchs. On each of these 5 surfaces, 2 x 5 indentations have been performed at different maximum depth: from 250 nm to 4 microm, with a step of 250 nm, for a total of 3200 tests. The numerous observations have been analysed applying an ad hoc modification of the Weibull Statistics, suggesting a natural evolution of the shells against external attacks. PMID:21137746

  8. BOREAS AFM-12 1-km AVHRR Seasonal Land Cover Classification

    NASA Technical Reports Server (NTRS)

    Steyaert, Lou; Hall, Forrest G.; Newcomer, Jeffrey A. (Editor); Knapp, David E. (Editor); Loveland, Thomas R.; Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-12 team's efforts focused on regional scale Surface Vegetation and Atmosphere (SVAT) modeling to improve parameterization of the heterogeneous BOREAS landscape for use in larger scale Global Circulation Models (GCMs). This regional land cover data set was developed as part of a multitemporal one-kilometer Advanced Very High Resolution Radiometer (AVHRR) land cover analysis approach that was used as the basis for regional land cover mapping, fire disturbance-regeneration, and multiresolution land cover scaling studies in the boreal forest ecosystem of central Canada. This land cover classification was derived by using regional field observations from ground and low-level aircraft transits to analyze spectral-temporal clusters that were derived from an unsupervised cluster analysis of monthly Normalized Difference Vegetation Index (NDVI) image composites (April-September 1992). This regional data set was developed for use by BOREAS investigators, especially those involved in simulation modeling, remote sensing algorithm development, and aircraft flux studies. Based on regional field data verification, this multitemporal one-kilometer AVHRR land cover mapping approach was effective in characterizing the biome-level land cover structure, embedded spatially heterogeneous landscape patterns, and other types of key land cover information of interest to BOREAS modelers.The land cover mosaics in this classification include: (1) wet conifer mosaic (low, medium, and high tree stand density), (2) mixed coniferous-deciduous forest (80% coniferous, codominant, and 80% deciduous), (3) recent visible bum, vegetation regeneration, or rock outcrops-bare ground-sparsely vegetated slow regeneration bum (four classes), (4) open water and grassland marshes, and (5) general agricultural land use/ grasslands (three classes). This land cover mapping approach did not detect small subpixel-scale landscape

  9. Beyond topography - enhanced imaging of cometary dust with the MIDAS AFM

    NASA Astrophysics Data System (ADS)

    Bentley, M. S.; Torkar, K.; Jeszenszky, H.; Romstedt, J.

    2013-09-01

    The MIDAS atomic force microscope (AFM) onboard the Rosetta spacecraft is primarily designed to return the 3D shape and structure of cometary dust particles collected at comet 67P/Churyumov-Gerasimenko [1]. Commercial AFMs have, however, been further developed to measure many other sample properties. The possibilities to make such measurements with MIDAS are explored here.

  10. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction

    NASA Astrophysics Data System (ADS)

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-07-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation.

  11. Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction

    PubMed Central

    Wang, Yuliang; Wang, Huimin; Bi, Shusheng; Guo, Bin

    2016-01-01

    The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation. PMID:27452115

  12. AFM imaging of functionalized double-walled carbon nanotubes.

    PubMed

    Lamprecht, C; Danzberger, J; Lukanov, P; Tîlmaciu, C-M; Galibert, A-M; Soula, B; Flahaut, E; Gruber, H J; Hinterdorfer, P; Ebner, A; Kienberger, F

    2009-07-01

    We present a comparative study of several non-covalent approaches to disperse, debundle and non-covalently functionalize double-walled carbon nanotubes (DWNTs). We investigated the ability of bovine serum albumin (BSA), phospholipids grafted onto amine-terminated polyethylene glycol (PL-PEG(2000)-NH(2)), as well as a combination thereof, to coat purified DWNTs. Topographical imaging with the atomic force microscope (AFM) was used to assess the coating of individual DWNTs and the degree of debundling and dispersion. Topographical images showed that functionalized DWNTs are better separated and less aggregated than pristine DWNTs and that the different coating methods differ in their abilities to successfully debundle and disperse DWNTs. Height profiles indicated an increase in the diameter of DWNTs depending on the functionalization method and revealed adsorption of single molecules onto the nanotubes. Biofunctionalization of the DWNT surface was achieved by coating DWNTs with biotinylated BSA, providing for biospecific binding of streptavidin in a simple incubation step. Finally, biotin-BSA-functionalized DWNTs were immobilized on an avidin layer via the specific avidin-biotin interaction. PMID:19375857

  13. Conductive probe AFM measurements of conjugated molecular wires.

    PubMed

    Ishida, Takao; Mizutani, Wataru; Liang, Tien-Tzu; Azehara, Hiroaki; Miyake, Koji; Sasaki, Shinya; Tokumoto, Hiroshi

    2003-12-01

    The electrical conduction of self-assembled monolayers (SAMs) made from conjugated molecules was measured using conductive probe atomic force microscopy (CP-AFM), with a focus on the molecular structural effect on conduction. First, the electrical conduction of SAMs made from phenylene oligomer SAMs was measured. The resistances through the monolayers increased exponentially with an increase in molecular length and the decay constants of transconductance beta were about 0.45 to 0.61 A(-1) measured at lower bias region. We further investigated the influence of applied load on the resistances. The resistances through terphenyl SAMs increased with an increase in the applied load up to 14 nN. Second, using an insertion technique into insulating alkanethiol SAMs, the electrical conduction of single conjugated terphenyl methanethiol and oligo(para-phenylenevinylene) (OPV) molecules embedded into insulating alkanethiol SAMs were measured. Electrical currents through these single molecules of OPVs were estimated to be larger than those through single terphenyl molecules, suggesting that the OPV structure can increase the electrical conduction of single molecules. Third, apparent negative differential resistance (NDR) was observed at higher bias measurements of SAMs. The appearance of NDR might be related to roughness of SAM surface, because apparent NDR was often observed on rough surfaces. In any case, the tip-molecule contact condition strongly affected carrier transport through metal tip/SAM/metal junction.

  14. AFM Investigation of Liquid-Filled Polymer Microcapsules Elasticity.

    PubMed

    Sarrazin, Baptiste; Tsapis, Nicolas; Mousnier, Ludivine; Taulier, Nicolas; Urbach, Wladimir; Guenoun, Patrick

    2016-05-10

    Elasticity of polymer microcapsules (MCs) filled with a liquid fluorinated core is studied by atomic force microscopy (AFM). Accurately characterized spherical tips are employed to obtain the Young's moduli of MCs having four different shell thicknesses. We show that those moduli are effective ones because the samples are composites. The strong decrease of the effective MC elasticity (from 3.0 to 0.1 GPa) as the shell thickness decreases (from 200 to 10 nm) is analyzed using a novel numerical approach. This model describes the evolution of the elasticity of a coated half-space according to the contact radius, the thickness of the film, and the elastic moduli of bulk materials. This numerical model is consistent with the experimental data and allows simulating the elastic behavior of MCs at high frequencies (5 MHz). While the quasi-static elasticity of the MCs is found to be very dependent on the shell thickness, the high frequency (5 MHz) elastic behavior of the core leads to a stable behavior of the MCs (from 2.5 to 3 GPa according to the shell thickness). Finally, the effect of thermal annealing on the MCs elasticity is investigated. The Young's modulus is found to decrease because of the reduction of the shell thickness due to the loss of the polymer. PMID:27058449

  15. BOREAS AFM-03-NCAR Electra 1994 Aircraft Sounding Data

    NASA Technical Reports Server (NTRS)

    Lenschow, Donald H.; Oncley, Steven P.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-3 team used the National Center for Atmospheric Research's (NCAR) Electra aircraft to make sounding measurements to study the planetary boundary layer using in situ and remote-sensing measurements. Measurements were made of wind speed and direction, air pressure and temperature, potential temperature, dewpoint, mixing ratio of H, O, CO, concentration, and ozone concentration. Twenty-five research missions were flown over the Northern Study Area (NSA), Southern Study Area (SSA), and the transect during BOREAS Intensive Field Campaigns (IFCs) 1, 2, and 3 during 1994. All missions had from four to ten soundings through the top of the planetary boundary layer. This sounding data set contains all of the in situ vertical profiles through the boundary layer top that were made (with the exception of 'porpoise' maneuvers). Data were recorded in one-second time intervals. These data are stored in tabular ASCII files. The NCAR Electra 1994 aircraft sounding data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  16. BOREAS AFM-2 Wyoming King Air 1994 Aircraft Sounding Data

    NASA Technical Reports Server (NTRS)

    Kelly, Robert D.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-2 team used the University of Wyoming King Air aircraft during IFCs 1, 2, and 3 in 1994 to collected pass-by-pass fluxes (and many other statistics) for the large number of level (constant altitude), straight-line passes used in a variety of flight patterns over the SSA and NSA and areas along the transect between these study areas. The data described here form a second set, namely soundings that were incorporated into nearly every research flight by the King Air in 1994. These soundings generally went from near the surface to above the inversion layer. Most were flown immediately after takeoff or immediately after finishing the last flux pattern of that particular day's flights. The parameters that were measured include wind direction, wind speed, west wind component (u), south wind component (v), static pressure, air dry bulb temperature, potential temperature, dewpoint, temperature, water vapor mixing ratio, and CO2 concentration. Data on the aircraft's location, attitude, and altitude during data collection are also provided. These data are stored in tabular ASCH files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  17. AFM-based force microsensor for a microrobot

    NASA Astrophysics Data System (ADS)

    Fatikow, Sergej; Fahlbusch, Stephan

    2001-10-01

    Microrobots are the result of increasing research activities at the border between microsystem technology and robotics. Today already, robots with dimensions of a few cubic- centimeters can be developed. Like conventional robots, microrobots represent a complex system that usually contains several different types of actuators and sensors. The measurement of gripping forces is the most important sensor application in micromanipulation besides visual servoing to protect the parts from too high surface pressures and thereby damage during the assembly process. Very small forces in the range of 200 (mu) N down to 0.1 (mu) N or even less have to be sensed. Thus, the aim of our current research activities is the development of a high-resolution integrated force microsensor for measuring gripping forces in a microhandling robot. On the one hand, the sensor should be a device for teleoperated manipulation tasks in a flexible microhandling station. On the other hand, typical microhandling operations should to a large extend be automated with the aid of computer-based signal processing of sensor information. The user should be provided with an interface for teleoperated manipulation and an interface for partially automated manipulation of microobjects. In this paper, a concept for the measurement of gripping forces in microrobotics using piezoresistive AFM (atomic force microscope) cantilevers is introduced. Further on, the concept of a microrobot-based SEM station and its applications are presented.

  18. PREFACE: NC-AFM 2005: Proceedings of the 8th International Conference on Non-Contact Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Reichling, M.; Mikosch, W.

    2006-04-01

    The 8th International Conference on Non-Contact Atomic Force Microscopy, held in Bad Essen, Germany, from 15 18th August 2005, attracted a record breaking number of participants presenting excellent contributions from a variety of scientific fields. This clearly demonstrated the high level of activity and innovation present in the community of NC-AFM researchers and the continuous growth of the field. The strongest ever participation of companies for a NC-AFM meeting is a sign for the emergence of new markets for the growing NC-AFM community; and the high standard of the products presented at the exhibition, many of them brand-new developments, reflected the unbroken progress in technology. The development of novel technologies and the sophistication of known techniques in research laboratories and their subsequent commercialization is still a major driving force for progress in this area of nanoscience. The conference was a perfect demonstration of how progress in the development of enabling technologies can readily be transcribed into basic research yielding fundamental insight with an impact across disciplines. The NC-AFM 2005 scientific programme was based on five cornerstones, each representing an area of vivid research and scientific progress. Atomic resolution imaging on oxide surfaces, which has long been a vision for the catalysis community, appears to be routine in several laboratories and after a period of demonstrative experiments NC-AFM now makes unique contributions to the understanding of processes in surface chemistry. These capabilities also open up new routes for the analysis of clusters and molecules deposited on dielectric surfaces where resolution limits are pushed towards the single atom level. Atomic precision manipulation with the dynamic AFM left the cradle of its infancy and flourishes in the family of bottom-up fabrication nanotechnologies. The systematic development of established and the introduction of new concepts of contrast

  19. In situ AFM crystal growth and dissolution study of calcite in the presence of aqueous fluoride

    NASA Astrophysics Data System (ADS)

    Vavouraki, A.; Putnis, C. V.; Putnis, A.; Koutsoukos, P. G.

    2009-04-01

    Fluoride is naturally abundant, encountered in rocks, soil and fresh and ocean water. Calcite crystals, during crystal growth may incorporate fluoride ions into their lattice (Okumura et al., 1983). In situ atomic force microscopy (AFM) has been used to study the growth and dissolution of calcite {104} surfaces in aqueous solutions in the presence of fluoride, using a fluid cell in which the supersaturated and the understaturated solutions respectively, flow over a freshly cleaved calcite crystal. For growth experiments, supersaturation index (S.I.) with respect to calcite was equal to 0.89 and the initial solution pH 10.2. The crystal growth rates were measured from the closure of the rhombohedral etch pits along the [010] direction induced by an initial dissolution step using pure water. The spreading rate of 2-dimensional nuclei was also measured along the same direction. In the presence of low fluoride concentrations (≤0.33 mM), the crystal growth rate of calcite was unaffected. At higher concentrations (up to 5 mM) growth rate decreased substantially to 50% of the rate in the absence of fluoride. Potential fluoride sorption over the calcite surface may ascribe the decrease of growth rates. Dissolution experiments were conducted at pH= 7.2 and dissolution rates of calcite were measured from the spreading of rhombohedral etch pits along both [010] and [42] directions. The presence of low concentrations of fluoride (≤1.1 mM) in the undersaturated solutions enhanced the dissolution rate along the [42] direction by 50% in comparison with pure water. The morphology of rhombohedral etch pits changed to hexagonal in the presence of fluoride in the undersaturated solutions. The AFM dissolution experiments suggested that the fluoride ions adsorbed onto the calcite surface. Further increase of fluoride concentrations (up to 1.6 mM) resulted in the decrease of the calcite dissolution rate by 60% in both [010] and [42] directions. Reference: Okumura, M, Kitano, Y

  20. An investigation using atomic force microscopy nanoindentation of dental enamel demineralization as a function of undissociated acid concentration and differential buffer capacity

    NASA Astrophysics Data System (ADS)

    Barbour, Michele E.; Shellis, R. Peter

    2007-02-01

    Acidic drinks and foodstuffs can demineralize dental hard tissues, leading to a pathological condition known as dental erosion, which is of increasing clinical concern. The first step in enamel dissolution is a demineralization of the outer few micrometres of tissue, which results in a softening of the structure. The primary determinant of dissolution rate is pH, but the concentration of undissociated acid, which is related to buffer capacity, also appears to be important. In this study, atomic force microscopy nanoindentation was used to measure the first initial demineralization (softening) induced within 1 min by exposure to solutions with a range of undissociated acid concentration and natural pH of 3.3 or with an undissociated acid concentration of 10 mmol l-1 and pH adjusted to 3.3. The results indicate that differential buffering capacity is a better determinant of softening than undissociated acid concentration. Under the conditions of these experiments, a buffer capacity of >3 mmol l-1 pH-1 does not have any further effect on dissolution rate. These results imply that differential buffering capacity should be used for preference over undissociated acid concentration or titratable acidity, which are more commonly employed in the literature.

  1. Microstructure and nanoindentation of the CLAM steel with nanocrystalline grains under Xe irradiation

    NASA Astrophysics Data System (ADS)

    Chang, Yongqin; Zhang, Jing; Li, Xiaolin; Guo, Qiang; Wan, Farong; Long, Yi

    2014-12-01

    This work presents an early look at irradiation effects on China low activation martensitic (CLAM) steel with nanocrystalline grains (NC-CLAM steels) under 500 keV Xe-ion bombardment at room temperature to doses up to 5.3 displacements per atom (dpa). The microstructure in the topmost region of the steel is composed of nanocrystalline grains with an average diameter of 13 nm. As the samples were implanted at low dose, the nanocrystalline grains had martensite lath structure, and many dislocations and high density bubbles were introduced into the NC-CLAM steels. As the irradiation dose up to 5.3 dpa, a tangled dislocation network exists in the lath region, and the size of the bubbles increases. X-ray diffraction results show that the crystal quality decreases after irradiation, although the nanocrystals obviously coarsen. Grain growth under irradiation may be ascribed to the direct impact of the thermal spike on grain boundaries in the NC-CLAM steels. In irradiated samples, a compressive stress exists in the surface layer because of grain growth and irradiation-introduced defects, while the irradiation introduced grain-size coarsening and defects gradients from the surface to matrix result in a tensile stress in the irradiated NC-CLAM steels. Nanoindentation was used to estimate changes in mechanical properties during irradiation, and the results show that the hardness of the NC-CLAM steels increases with increasing irradiation dose, which was ascribed to the competition between the grain boundaries and the irradiation-introduced defects.

  2. Measurement of fracture toughness by nanoindentation methods: Recent advances and future challenges

    SciTech Connect

    Sebastiani, Marco; Johanns, K. E.; Herbert, Erik G.; Pharr, George M.

    2015-04-30

    In this study, we describe recent advances and developments for the measurement of fracture toughness at small scales by the use of nanoindentation-based methods including techniques based on micro-cantilever beam bending and micro-pillar splitting. A critical comparison of the techniques is made by testing a selected group of bulk and thin film materials. For pillar splitting, cohesive zone finite element simulations are used to validate a simple relationship between the critical load at failure, the pillar radius, and the fracture toughness for a range of material properties and coating/substrate combinations. The minimum pillar diameter required for nucleation and growth of a crack during indentation is also estimated. An analysis of pillar splitting for a film on a dissimilar substrate material shows that the critical load for splitting is relatively insensitive to the substrate compliance for a large range of material properties. Experimental results from a selected group of materials show good agreement between single cantilever and pillar splitting methods, while a discrepancy of ~25% is found between the pillar splitting technique and double-cantilever testing. It is concluded that both the micro-cantilever and pillar splitting techniques are valuable methods for micro-scale assessment of fracture toughness of brittle ceramics, provided the underlying assumptions can be validated. Although the pillar splitting method has some advantages because of the simplicity of sample preparation and testing, it is not applicable to most metals because their higher toughness prevents splitting, and in this case, micro-cantilever bend testing is preferred.

  3. Viscoelastic properties of cell walls of single living plant cells determined by dynamic nanoindentation.

    PubMed

    Hayot, Céline M; Forouzesh, Elham; Goel, Ashwani; Avramova, Zoya; Turner, Joseph A

    2012-04-01

    Plant development results from controlled cell divisions, structural modifications, and reorganizations of the cell wall. Thereby, regulation of cell wall behaviour takes place at multiple length scales involving compositional and architectural aspects in addition to various developmental and/or environmental factors. The physical properties of the primary wall are largely determined by the nature of the complex polymer network, which exhibits time-dependent behaviour representative of viscoelastic materials. Here, a dynamic nanoindentation technique is used to measure the time-dependent response and the viscoelastic behaviour of the cell wall in single living cells at a micron or sub-micron scale. With this approach, significant changes in storage (stiffness) and loss (loss of energy) moduli are captured among the tested cells. The results reveal hitherto unknown differences in the viscoelastic parameters of the walls of same-age similarly positioned cells of the Arabidopsis ecotypes (Col 0 and Ws 2). The technique is also shown to be sensitive enough to detect changes in cell wall properties in cells deficient in the activity of the chromatin modifier ATX1. Extensive computational modelling of the experimental measurements (i.e. modelling the cell as a viscoelastic pressure vessel) is used to analyse the influence of the wall thickness, as well as the turgor pressure, at the positions of our measurements. By combining the nanoDMA technique with finite element simulations quantifiable measurements of the viscoelastic properties of plant cell walls are achieved. Such techniques are expected to find broader applications in quantifying the influence of genetic, biological, and environmental factors on the nanoscale mechanical properties of the cell wall.

  4. Mechanobiological Assessment of TMJ Disc Surfaces: Nanoindentation and Transmission Electron Microscopy

    PubMed Central

    Juran, Cassandra M.; Dolwick, M. Franklin

    2015-01-01

    ABSTRACT Objectives Temporomandibular disc is a mechanically robust fibrocartilage tissue exhibiting highly elastic compressive, shear, and tensile moduli with structurally dense extracellular matrix that supports functional loading of the joint. The aim of this study was to illustrate structural complexities of the superior and inferior disc surfaces, to demonstrate the robust mechanical ability of the disc as a whole may be due to depth-dependent regional/layered variation, and also to provide characterization data imperative for future tissue engineering efforts focused on restoring function to the joint. Material and Methods Nanoindentation was used to assess tissue zones in conjunction with detailed Transmission Electron Microscopy to define structural attributes that influence the temporomandibular disc function. Results The disc architecture adjacent to the superior surface was shown to have three distinct regional segments within the interface layer: 1-a surface peripheral layer; 2-subsurface region; and 3-a layer of helical matrix bundles. The inferior surface displayed an interface layer (20 µm) that showed limited cell populations with little depth-dependent structural variation, a stiffer elastic modulus and reduced energy dissipation compared to the superior surface. These data indicate that the primary function of the inferior surface is resistance to compression rather than load distribution during joint motion. Conclusions These are the first works that demonstrate that the superior central surface of the he temporomandibular disc is structured in depth-dependent isometric layers, each of which provides different mechanical function supporting the bulk tissue’s properties. From a clinical perspective these data have potential to define regions susceptible to fatigue that may translate to diagnostic criteria to better define the stages of dysfunction. PMID:26904180

  5. Nanoindentation study of niobium nitride thin films on niobium fabricated by reactive pulsed laser deposition

    SciTech Connect

    Mamun, Md Abdullah Al; Farha, Ashraf Hassan; Ufuktepe, Yüksel; Elsayed-Ali, Hani E.; Elmustafa, Abdelmageed A.

    2015-03-01

    Nanomechanical and structural properties of NbNx films deposited on single crystal Nb using pulsed laser deposition for different substrate temperature were previously investigated as a function of film/substrate crystal structure (Mamun et al. (2012) [30]). In this study we focus on the effect of laser fluences and background nitrogen pressure on the nanomechanical and structural properties of NbNx films. The crystal structure and surface morphology of the thin films were tested by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Using nanoindentation, the investigation of the nanomechanical properties revealed that the hardness of the NbNx films was directly influenced by the laser fluence for low background nitrogen pressure, whereas the nanomechanical hardness showed no apparent correlation with laser fluence at high background nitrogen pressure. The NbNx film hardness measured at 30% film thickness increased from 14.0 ± 1.3 to 18.9 ± 2.4 GPa when the laser fluence was increased from 15 to 25 J/cm2 at 10.7 Pa N2 pressure. X-ray diffraction showed NbNx films with peaks that correspond to δ-NbN cubic and β-Nb2N hexagonal phases in addition to the δ'-NbN hexagonal phase. Finally, increasing the laser fluence resulted in NbNx films with larger grain sizes.

  6. Novel Way to Characterize Metal-Insulator-Metal Devices via Nanoindentation: Preprint

    SciTech Connect

    Periasamy, P.; Packard, C. E.; O?Hayre, R. P.; Berry, J. J.; Parilla, P. A.; Ginley, D. S.

    2011-07-01

    Metal-Insulator-Metal (MIM) devices are crucial components for applications ranging from optical rectennas for harvesting sunlight to infrared detectors. To date, the relationship between materials properties and device performance in MIM devices is not fully understood, partly due to the difficulty in making and reproducing reliable devices. One configuration that is popular due to its simplicity and ease of fabrication is the point-contact diode where a metal tip serves as one of the metals in the MIM device. The intrinsic advantage of the point-contact configuration is that it is possible to achieve very small contact areas for the device thereby allowing very high-frequency operation. In this study, precise control over the contact area and penetration depth of an electrically conductive tip into a metal/insulator combination is achieved using a nanoindenter with in-situ electrical contact resistance measurement capabilities. A diamond probe tip, doped (degeneratively) with boron for conductivity, serves as the point contact and second 'metal' (b-Diamond) of the MIM diode. The base layer consists of Nb/Nb2O5 thin films on Si substrates and serves as the first metal /insulator combination of the MIM structure. The current-voltage response of the diodes is measured under a range of conditions to assess the validity and repeatability of the technique. Additionally, we compare the results of this technique to those acquired using a bent-wire approach and find that Nb/Nb2O5/b-Diamond MIM devices show an excellent asymmetry (60-300) and nonlinearity values (~6-9). This technique shows great promise for screening metal-insulator combinations for performance without the uncertainty that stems from a typical bent-wire point-contact.

  7. Measurement of fracture toughness by nanoindentation methods: Recent advances and future challenges

    DOE PAGES

    Sebastiani, Marco; Johanns, K. E.; Herbert, Erik G.; Pharr, George M.

    2015-04-30

    In this study, we describe recent advances and developments for the measurement of fracture toughness at small scales by the use of nanoindentation-based methods including techniques based on micro-cantilever beam bending and micro-pillar splitting. A critical comparison of the techniques is made by testing a selected group of bulk and thin film materials. For pillar splitting, cohesive zone finite element simulations are used to validate a simple relationship between the critical load at failure, the pillar radius, and the fracture toughness for a range of material properties and coating/substrate combinations. The minimum pillar diameter required for nucleation and growth ofmore » a crack during indentation is also estimated. An analysis of pillar splitting for a film on a dissimilar substrate material shows that the critical load for splitting is relatively insensitive to the substrate compliance for a large range of material properties. Experimental results from a selected group of materials show good agreement between single cantilever and pillar splitting methods, while a discrepancy of ~25% is found between the pillar splitting technique and double-cantilever testing. It is concluded that both the micro-cantilever and pillar splitting techniques are valuable methods for micro-scale assessment of fracture toughness of brittle ceramics, provided the underlying assumptions can be validated. Although the pillar splitting method has some advantages because of the simplicity of sample preparation and testing, it is not applicable to most metals because their higher toughness prevents splitting, and in this case, micro-cantilever bend testing is preferred.« less

  8. AFM nanoscale indentation in air of polymeric and hybrid materials with highly different stiffness

    NASA Astrophysics Data System (ADS)

    Suriano, Raffaella; Credi, Caterina; Levi, Marinella; Turri, Stefano

    2014-08-01

    In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol-gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force-distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry. AFM indentation tests show that the choice of the cantilever spring constant and of tip shape is crucially influenced by elastic properties of samples. When adhesion-dominated interactions occur between the tip and the surface of samples, force-displacement curves reveal that a suitable functionalization of AFM probes allows the control of such interactions and the extraction of Young' modulus from AFM curves that would be otherwise unfeasible. By applying different mathematical models depending on AFM probes and materials under investigation, the values of Young's modulus were obtained and compared to those measured by rheological and dynamic mechanical analysis or to literature data. Our results show that a wide range of elastic moduli (10 kPa-10 GPa) can be determined by AFM in good agreement with those measured by conventional macroscopic measurements.

  9. Probing Ternary Solvent Effect in High V(oc) Polymer Solar Cells Using Advanced AFM Techniques.

    PubMed

    Li, Chao; Ding, Yi; Soliman, Mikhael; Lorenzo, Josie; Dhasmana, Nitesh; Chantharasupawong, Panit; Ievlev, Anton V; Gesquiere, Andre J; Tetard, Laurene; Thomas, Jayan

    2016-02-01

    This work describes a simple method to develop a high V(oc) low band gap PSCs. In addition, two new atomic force microscopy (AFM)-based nanoscale characterization techniques to study the surface morphology and physical properties of the structured active layer are introduced. With the help of ternary solvent processing of the active layer and C60 buffer layer, a bulk heterojunction PSC with V(oc) more than 0.9 V and conversion efficiency 7.5% is developed. In order to understand the fundamental properties of the materials ruling the performance of the PSCs tested, AFM-based nanoscale characterization techniques including Pulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFM (MSAFM) are introduced. Interestingly, MSAFM exhibits high sensitivity for direct visualization of the donor-acceptor phases in the active layer of the PSCs. Finally, conductive-AFM (cAFM) studies reveal local variations in conductivity in the donor and acceptor phases as well as a significant increase in photocurrent in the PTB7:ICBA sample obtained with the ternary solvent processing. PMID:26807919

  10. XPS and AFM Study of GaAs Surface Treatment

    SciTech Connect

    Contreras-Guerrero, R.; Wallace, R. M.; Aguirre-Francisco, S.; Herrera-Gomez, A.; Lopez-Lopez, M.

    2008-11-13

    Obtaining smooth and atomically clean surfaces is an important step in the preparation of a surface for device manufacturing. In this work different processes are evaluated for cleaning a GaAs surface. A good surface cleaning treatment is that which provides a high level of uniformity and controllability of the surface. Different techniques are useful as cleaning treatments depending on the growth process to be used. The goal is to remove the oxygen and carbon contaminants and then form a thin oxide film to protect the surface, which is easy to remove later with thermal desorption mechanism like molecular beam epitaxy (MBE) with minimal impact to the surface. In this study, atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to characterize the structure of the surface, the composition, as well as detect oxygen and carbon contaminant on the GaAs surface. This study consists in two parts. The first part the surface was subjected to different chemical treatments. The chemical solutions were: (a)H{sub 2}SO{sub 4}:H{sub 2}O{sub 2}:H{sub 2}O(4:1:100), (b) HCl: H{sub 2}O(1:3), (c)NH{sub 4}OH 29%. The treatments (a) and (b) reduced the oxygen on the surface. Treatment (c) reduces carbon contamination. In the second part we made MOS devices on the surfaces treated. They were characterized by CV and IV electrical measurements. They show frequency dispersion.

  11. AFM-based measurement of the mechanical properties of thin polymer films and determination of the optical path length of nearly index-matched cavities

    NASA Astrophysics Data System (ADS)

    Wieland, Christopher F.

    2008-10-01

    Two technologies, immersion and imprint lithography, represent important stepping stones for the development of the next generation of lithography tools. However, although the two approaches offer important advantages, both pose many significant technological challenges that must be overcome before they can be successfully implemented. For imprint lithography, special care must be taken when choosing an etch barrier because studies have indicated that some physical material properties may be size dependent. Additionally, regarding immersion lithography, proper image focus requires that the optical path length between the lens and substrate be maintained during the entire writing process. The work described in this document was undertaken to address the two challenges described above. A new mathematical model was developed and used in conjunction with AFM nano-indentation techniques to measure the elastic modulus of adhesive, thin polymer films as a function of the film thickness. It was found that the elastic modulus of the polymer tested did not change appreciably from the value determined using bulk measurement techniques in the thickness range probed. Additionally, a method for monitoring and controlling the optical path length within the gap of a nearly index-matching cavity based on coherent broadband interference was developed. In this method, the spectrum reflected for a cavity illuminated with a modelocked Ti:Sapphire laser was collected and analyzed using Fourier techniques. It was found that this method could determine the optical path length of the cavity, quickly and accurately enough to control a servo-based feedback system to correct deviations in the optical path length in real time when coupled with special computation techniques that minimized unnecessary operations.

  12. The formation of liquid bridge in different operating modes of AFM

    NASA Astrophysics Data System (ADS)

    Wei, Zheng; Sun, Yan; Ding, WenXuan; Wang, ZaiRan

    2016-09-01

    The liquid bridge is one of the principal factors that cause artifacts in ambient-pressure atomic force microscope (AFM) images. Additionally, it is the main component of the adhesion force in ambient conditions. To understand the AFM imaging mechanism and the sample characteristics, it is essential to study the liquid bridge. This study interprets the physical mechanism involved in liquid bridge formation, which is composed of three different physical processes: the squeezing process, capillary condensation, and liquid film flow. We discuss the contributions of these three mechanisms to the volume and the capillary force of the liquid bridge in different AFM operation modes.

  13. MetaRep, an extended CMAS 3D program to visualize mafic (CMAS, ACF-S, ACF-N) and pelitic (AFM-K, AFM-S, AKF-S) projections

    NASA Astrophysics Data System (ADS)

    France, Lydéric; Nicollet, Christian

    2010-06-01

    MetaRep is a program based on our earlier program CMAS 3D. It is developed in MATLAB ® script. MetaRep objectives are to visualize and project major element compositions of mafic and pelitic rocks and their minerals in the pseudo-quaternary projections of the ACF-S, ACF-N, CMAS, AFM-K, AFM-S and AKF-S systems. These six systems are commonly used to describe metamorphic mineral assemblages and magmatic evolutions. Each system, made of four apices, can be represented in a tetrahedron that can be visualized in three dimensions with MetaRep; the four tetrahedron apices represent oxides or combination of oxides that define the composition of the projected rock or mineral. The three-dimensional representation allows one to obtain a better understanding of the topology of the relationships between the rocks and minerals and relations. From these systems, MetaRep can also project data in ternary plots (for example, the ACF, AFM and AKF ternary projections can be generated). A functional interface makes it easy to use and does not require any knowledge of MATLAB ® programming. To facilitate the use, MetaRep loads, from the main interface, data compiled in a Microsoft Excel ™ spreadsheet. Although useful for scientific research, the program is also a powerful tool for teaching. We propose an application example that, by using two combined systems (ACF-S and ACF-N), provides strong confirmation in the petrological interpretation.

  14. Molecular shape and binding force of Mycoplasma mobile's leg protein Gli349 revealed by an AFM study

    SciTech Connect

    Lesoil, Charles; Nonaka, Takahiro; Sekiguchi, Hiroshi; Osada, Toshiya; Miyata, Makoto; Afrin, Rehana; Ikai, Atsushi

    2010-01-15

    Recent studies of the gliding bacteria Mycoplasma mobile have identified a family of proteins called the Gli family which was considered to be involved in this novel and yet fairly unknown motility system. The 349 kDa protein called Gli349 was successfully isolated and purified from the bacteria, and electron microscopy imaging and antibody experiments led to the hypothesis that it acts as the 'leg' of M. mobile, responsible for attachment to the substrate as well as for gliding motility. However, more precise evidence of the molecular shape and function of this protein was required to asses this theory any further. In this study, an atomic force microscope (AFM) was used both as an imaging and a force measurement device to provide new information about Gli349 and its role in gliding motility. AFM images of the protein were obtained revealing a complex structure with both rigid and flexible parts, consistent with previous electron micrographs of the protein. Single-molecular force spectroscopy experiments were also performed, revealing that Gli349 is able to specifically bind to sialyllactose molecules and withstand unbinding forces around 70 pN. These findings strongly support the idea that Gli349 is the 'leg' protein of M. mobile, responsible for binding and also most probably force generation during gliding motility.

  15. Accurately evaluating Young's modulus of polymers through nanoindentations: A phenomenological correction factor to the Oliver and Pharr procedure

    NASA Astrophysics Data System (ADS)

    Tranchida, Davide; Piccarolo, Stefano; Loos, Joachim; Alexeev, Alexander

    2006-10-01

    The Oliver and Pharr [J. Mater. Res. 7, 1564 (1992)] procedure is a widely used tool to analyze nanoindentation force curves obtained on metals or ceramics. Its application to polymers is, however, difficult, as Young's moduli are commonly overestimated mainly because of viscoelastic effects and pileup. However, polymers spanning a large range of morphologies have been used in this work to introduce a phenomenological correction factor. It depends on indenter geometry: sets of calibration indentations have to be performed on some polymers with known elastic moduli to characterize each indenter.

  16. Direct observation of deformation-induced grain growth during the nanoindentation of ultrafine-grained Al at room temperature

    SciTech Connect

    Jin, M.; Minor, A.M.; Stach, E.A.; Morris, J.W. . E-mail: jwmorris@berkeley.edu

    2004-10-18

    In situ nanoindentation within a transmission electron microscope is used to investigate the deformation mechanisms in ultrafine-grained Al films. Deformation-induced grain growth resulting from grain boundary migration, grain rotation and grain coalescence is commonly observed as the indentation proceeds. In situ studies of nanograined films suggest that the same mechanisms are operative, though the difficulty of imaging nanosized grains makes the evidence less clear. The results suggest that grain growth and coalescence are important modes of response in the deformation of ultrafine- and nanograined materials.

  17. Identifying individual chemical bonds in single-molecule chemical reaction products using nc-AFM

    NASA Astrophysics Data System (ADS)

    Wickenburg, Sebastian; de Oteyza, Dimas G.; Chen, Yen-Chia; Riss, Alexander; Tsai, Hsin-Zon; Pedramrazi, Zahra; Bradley, Aaron J.; Ugeda, Miguel M.; Gorman, Patrick; Etkin, Grisha; Mowbray, Duncan J.; Perez, Alejandro; Rubio, Angel; Crommie, Michael F.; Fischer, Felix R.

    2014-03-01

    Determining reaction pathways and products is an integral part of chemical synthesis. Ensemble measurements are commonly used, but identifying products of complex reactions at surfaces presents a significant challenge. Here we present a non-contact AFM (nc-AFM) study to directly address this issue. We followed the change of the chemical structures, from reactants to products of enediyne cyclization reactions on metal surfaces. Thermal annealing of enediynes induced a series of cyclization cascades leading to radical species and the formation of dimers. Atomically resolved nc-AFM images reveal the precise chemical structure and the formation of chemical bonds between single molecular units. With the support of DFT calculations, we identified the underlying chemical pathways and barriers, demonstrating the potential of this atomically resolved AFM technique to study unknown reaction products in surface chemistry at the single-molecule level.

  18. Probing Cytoskeletal Structures by Coupling Optical Superresolution and AFM Techniques for a Correlative Approach

    PubMed Central

    Chacko, Jenu Varghese; Zanacchi, Francesca Cella; Diaspro, Alberto

    2013-01-01

    In this article, we describe and show the application of some of the most advanced fluorescence superresolution techniques, STED AFM and STORM AFM microscopy towards imaging of cytoskeletal structures, such as microtubule filaments. Mechanical and structural properties can play a relevant role in the investigation of cytoskeletal structures of interest, such as microtubules, that provide support to the cell structure. In fact, the mechanical properties, such as the local stiffness and the elasticity, can be investigated by AFM force spectroscopy with tens of nanometers resolution. Force curves can be analyzed in order to obtain the local elasticity (and the Young's modulus calculation by fitting the force curves from every pixel of interest), and the combination with STED/STORM microscopy integrates the measurement with high specificity and yields superresolution structural information. This hybrid modality of superresolution-AFM working is a clear example of correlative multimodal microscopy. PMID:24027190

  19. Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM

    NASA Astrophysics Data System (ADS)

    Avdic, A.; Lugstein, A.; Wu, M.; Gollas, B.; Pobelov, I.; Wandlowski, T.; Leonhardt, K.; Denuault, G.; Bertagnolli, E.

    2011-04-01

    We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes.

  20. Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM.

    PubMed

    Avdic, A; Lugstein, A; Wu, M; Gollas, B; Pobelov, I; Wandlowski, T; Leonhardt, K; Denuault, G; Bertagnolli, E

    2011-04-01

    We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes.

  1. Fabrication of cone-shaped boron doped diamond and gold nanoelectrodes for AFM-SECM.

    PubMed

    Avdic, A; Lugstein, A; Wu, M; Gollas, B; Pobelov, I; Wandlowski, T; Leonhardt, K; Denuault, G; Bertagnolli, E

    2011-04-01

    We demonstrate a reliable microfabrication process for a combined atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) measurement tool. Integrated cone-shaped sensors with boron doped diamond (BDD) or gold (Au) electrodes were fabricated from commercially available AFM probes. The sensor formation process is based on mature semiconductor processing techniques, including focused ion beam (FIB) machining, and highly selective reactive ion etching (RIE). The fabrication approach preserves the geometry of the original AFM tips resulting in well reproducible nanoscaled sensors. The feasibility and functionality of the fully featured tips are demonstrated by cyclic voltammetry, showing good agreement between the measured and calculated currents of the cone-shaped AFM-SECM electrodes. PMID:21368355

  2. Using XAFS, EDAX and AFM in comparative study of various natural and synthetic emeralds

    NASA Astrophysics Data System (ADS)

    Parikh, P.; Saini, N. L.; Dalela, S.; Bhardwaj, D. M.; Fernandes, S.; Gupta, R. P.; Garg, K. B.

    2003-01-01

    We have performed XAFS, EDAX and AFM studies on some natural and synthetic emeralds. While the XAFS results yield information on changes in the valence of the Cr ion and the n-n distance the AFM is used to determine the areal atomic density on surface of the crystals. It is a pilot study to explore if the three techniques can offer a possible way of distinguishing between the natural and synthetic emeralds and the results are promising.

  3. Insight into mechanics of AFM tip-based nanomachining: bending of cantilevers and machined grooves

    NASA Astrophysics Data System (ADS)

    Al-Musawi, R. S. J.; Brousseau, E. B.; Geng, Y.; Borodich, F. M.

    2016-09-01

    Atomic force microscope (AFM) tip-based nanomachining is currently the object of intense research investigations. Values of the load applied to the tip at the free end of the AFM cantilever probe used for nanomachining are always large enough to induce plastic deformation on the specimen surface contrary to the small load values used for the conventional contact mode AFM imaging. This study describes an important phenomenon specific for AFM nanomachining in the forward direction: under certain processing conditions, the deformed shape of the cantilever probe may change from a convex to a concave orientation. The phenomenon can principally change the depth and width of grooves machined, e.g. the grooves machined on a single crystal copper specimen may increase by 50% on average following such a change in the deformed shape of the cantilever. It is argued that this phenomenon can take place even when the AFM-based tool is operated in the so-called force-controlled mode. The study involves the refined theoretical analysis of cantilever probe bending, the analysis of experimental signals monitored during the backward and forward AFM tip-based machining and the inspection of the topography of produced grooves.

  4. Insight into mechanics of AFM tip-based nanomachining: bending of cantilevers and machined grooves.

    PubMed

    Al-Musawi, R S J; Brousseau, E B; Geng, Y; Borodich, F M

    2016-09-23

    Atomic force microscope (AFM) tip-based nanomachining is currently the object of intense research investigations. Values of the load applied to the tip at the free end of the AFM cantilever probe used for nanomachining are always large enough to induce plastic deformation on the specimen surface contrary to the small load values used for the conventional contact mode AFM imaging. This study describes an important phenomenon specific for AFM nanomachining in the forward direction: under certain processing conditions, the deformed shape of the cantilever probe may change from a convex to a concave orientation. The phenomenon can principally change the depth and width of grooves machined, e.g. the grooves machined on a single crystal copper specimen may increase by 50% on average following such a change in the deformed shape of the cantilever. It is argued that this phenomenon can take place even when the AFM-based tool is operated in the so-called force-controlled mode. The study involves the refined theoretical analysis of cantilever probe bending, the analysis of experimental signals monitored during the backward and forward AFM tip-based machining and the inspection of the topography of produced grooves. PMID:27532247

  5. Fabrication of carbon nanotube AFM probes using the Langmuir-Blodgett technique.

    PubMed

    Lee, Jae-Hyeok; Kang, Won-Seok; Choi, Bung-Sam; Choi, Sung-Wook; Kim, Jae-Ho

    2008-09-01

    Carbon nanotube (CNT)-tipped atomic force microscopy (AFM) probes have shown a significant potential for obtaining high-resolution imaging of nanostructure and biological materials. In this paper, we report a simple method to fabricate single-walled carbon nanotube (SWNT) nanoprobes for AFM using the Langmuir-Blodgett (LB) technique. Thiophenyl-modified SWNTs (SWNT-SHs) through amidation of SWNTs in chloroform allowed to be spread and form a stable Langmuir monolayer at the water/air interface. A simple two-step transfer process was used: (1) dipping conventional AFM probes into the Langmuir monolayer and (2) lifting the probes from the water surface. This results in the attachment of SWNTs onto the tips of AFM nanoprobes. We found that the SWNTs assembled on the nanoprobes were well-oriented and robust enough to maintain their shape and direction even after successive scans. AFM measurements of a nano-porous alumina substrate and deoxyribonucleic acid using SWNT-modified nanoprobes revealed that the curvature diameter of the nanoprobes was less than 3 nm and a fine resolution was obtained than that from conventional AFM probes. We also demonstrate that the LB method is a scalable process capable of simultaneously fabricating a large number of SWNT-modified nanoprobes.

  6. Probing ternary solvent effect in high Voc polymer solar cells using advanced AFM techniques

    DOE PAGES

    Li, Chao; Soleman, Mikhael; Lorenzo, Josie; Dhasmana, Nitesh; Chantharasupawong, Panit; Ievlev, Anton; Gesquiere, Andre; Tetard, Laurene; Thomas, Jayan

    2016-01-25

    This work describes a simple method to develop a high Voc low band gap PSCs. In addition, two new atomic force microscopy (AFM)-based nanoscale characterization techniques to study the surface morphology and physical properties of the structured active layer are introduced. With the help of ternary solvent processing of the active layer and C60 buffer layer, a bulk heterojunction PSC with Voc more than 0.9 V and conversion efficiency 7.5% is developed. In order to understand the fundamental properties of the materials ruling the performance of the PSCs tested, AFM-based nanoscale characterization techniques including Pulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFMmore » (MSAFM) are introduced. Interestingly, MSAFM exhibits high sensitivity for direct visualization of the donor–acceptor phases in the active layer of the PSCs. Lastly, conductive-AFM (cAFM) studies reveal local variations in conductivity in the donor and acceptor phases as well as a significant increase in photocurrent in the PTB7:ICBA sample obtained with the ternary solvent processing.« less

  7. Combined quantitative ultrasonic and time-resolved interaction force AFM imaging

    SciTech Connect

    Parlak, Z.; Degertekin, F. L.

    2011-01-15

    The authors describe a method where quantitative ultrasonic atomic force microscopy (UAFM) is achieved during time-resolved interaction force (TRIF) imaging in intermittent contact mode. The method uses a calibration procedure for quantitative UAFM. It improves elasticity measurements of stiff regions of surfaces while retaining the capabilities of the TRIF mode for topography, adhesion, dissipation, and elasticity measurements on soft regions of sample surfaces. This combination is especially advantageous when measuring and imaging samples with broad stiffness range in a nondestructive manner. The experiments utilize an active AFM probe with high bandwidth and the UAFM calibration is performed by measuring the magnitude of the time-resolved UAFM signal at a judiciously chosen frequency for different contact stiffness values during individual taps. Improved sensitivity to stiff surface elasticity is demonstrated on a special sample. The results show that combining UAFM with TRIF provides 2.5 GPa (5%) standard deviation on the silicon surface reduced Young's modulus, representing 5x improvement over using only TRIF mode imaging.

  8. Analyses of Interface Adhesion between Cu and SiCN Etch Stop Layers by Nanoindentation and Nanoscratch Tests

    NASA Astrophysics Data System (ADS)

    Chang, Shou-Yi; Lee, Yu-Shuien

    2007-04-01

    The interface chemistry and adhesion strength between Cu and SiCN etch stop layers have been investigated to evaluate the reliability of interconnect structures. Analyses of the chemical compositions and bonding configurations reveal that the SiCN etch stop layer was mostly composed of Si to N and Si to C bonding, including Si-N, Si-CN2, and Si-C2N. At the Cu/SiCN interface, an oxide layer was observed, and SiCN-O and Cu-O bonding was detected. In nanoindentation and nanoscratch tests, Cu/SiCN interface delamination occurred around indents and along scratch tracks, and the adhesion energy between Cu and SiCN layers was accordingly measured and calculated. The adhesion energy of the Cu/SiCN interface was measured to be about 4.98 J/m2 in the nanoindentation test, while that measured using the nanoscratch test was lower, at about 0.98 J/m2. The “mode mixity” effect was responsible for the difference between the adhesion energies obtained using these two methods.

  9. The nano-epsilon dot method for strain rate viscoelastic characterisation of soft biomaterials by spherical nano-indentation.

    PubMed

    Mattei, G; Gruca, G; Rijnveld, N; Ahluwalia, A

    2015-10-01

    Nano-indentation is widely used for probing the micromechanical properties of materials. Based on the indentation of surfaces using probes with a well-defined geometry, the elastic and viscoelastic constants of materials can be determined by relating indenter geometry and measured load and displacement to parameters which represent stress and deformation. Here we describe a method to derive the viscoelastic properties of soft hydrated materials at the micro-scale using constant strain rates and stress-free initial conditions. Using a new self-consistent definition of indentation stress and strain and corresponding unique depth-independent expression for indentation strain rate, the epsilon dot method, which is suitable for bulk compression testing, is transformed to nano-indentation. We demonstrate how two materials can be tested with a displacement controlled commercial nano-indentor using the nano-espilon dot method (nano-ε̇M) to give values of instantaneous and equilibrium elastic moduli and time constants with high precision. As samples are tested in stress-free initial conditions, the nano-ε̇M could be useful for characterising the micro-mechanical behaviour of soft materials such as hydrogels and biological tissues at cell length scales. PMID:26143307

  10. Characterizing moisture-dependent mechanical properties of organic materials: humidity-controlled static and dynamic nanoindentation of wood cell walls

    NASA Astrophysics Data System (ADS)

    Bertinetti, Luca; Hangen, Ude D.; Eder, Michaela; Leibner, Petra; Fratzl, Peter; Zlotnikov, Igor

    2015-06-01

    Nanoindentation is an ideal technique to study local mechanical properties of a wide range of materials on the sub-micron scale. It has been widely used to investigate biological materials in the dry state; however, their properties are strongly affected by their moisture content, which until now has not been consistently controlled. In the present study, we developed an experimental set-up for measuring local mechanical properties of materials by nanoindentation in a controlled environment of relative humidity (RH) and temperature. The significance of this new approach in studying biological materials was demonstrated for the secondary cell wall layer (S2) in Spruce wood (Picea abies). The hardness of the cell wall layer decreased from an average of approximately 0.6 GPa at 6% RH down to approximately 0.2 GPa at 79% RH, corresponding to a reduction by a factor of 3. Under the same conditions, the indentation modulus also decreased by about 40%. The newly designed experimental set-up has a strong potential for a variety of applications involving the temperature- and humidity-dependent properties of biological and artificial organic nanocomposites.

  11. Error Estimation of Nanoindentation Mechanical Properties Near a Dissimilar Interface via Finite Element Analysis and Analytical Solution Methods.

    PubMed

    Zhao, Y; Ovaert, T C

    2010-12-01

    Nanoindentation methods are well suited for probing the mechanical properties of a heterogeneous surface, since the probe size and contact volumes are small and localized. However, the nanoindentation method may introduce errors in the computed mechanical properties when indenting near the interface between two materials having significantly different mechanical properties. Here we examine the case where a soft material is loaded in close proximity to an interface of higher modulus, such as the case when indenting bone near a metallic implant. Results are derived from both an approximate analytical quarter-space solution and a finite element model, and used to estimate the error in indentation-determined elastic modulus as a function of the distance from the apex of contact to the dissimilar interface, for both Berkovich and spherical indenter geometries. Sample data reveal the potential errors in mechanical property determination that can occur when indenting near an interface having higher stiffness, or when characterizing strongly heterogeneous materials. The results suggest that caution should be used when interpreting results in the near-interfacial region.

  12. Assessment of Microelastic Properties of Bone Using Scanning Acoustic Microscopy: A Face-to-Face Comparison with Nanoindentation

    NASA Astrophysics Data System (ADS)

    Rupin, Fabienne; Saïed, Amena; Dalmas, Davy; Peyrin, Françoise; Haupert, Sylvain; Raum, Kay; Barthel, Etienne; Boivin, Georges; Laugier, Pascal

    2009-07-01

    The current work aimed at comparing, on site-matched cortical bone tissue, the micron-level elastic modulus Ea derived from 200 MHz-scanning acoustic microscopy (SAM) acoustic impedance (Z) combined with bone mineral density (assessed by synchrotron radiation microcomputed tomography, SR-µCT) to nanoindentation modulus En. A good correlation was observed between En and Z (R2=0.67, p<0.0001, root mean square error RMSE=1.9 GPa). The acoustical elastic modulus Ea derived from Z showed higher values of E compared to nanoindentation moduli. We assumed that the discrepancy between Ea and En values may likely be due to the fixed assumed value of Poisson's ratio while values comprised between 0.15 and 0.45 have been reported in the literature. Despite these differences, a highly significant correlation between Ea and En was found (R2=0.66, p<0.001, RMSE=1.8 GPa) suggesting that SAM can reliably be used as a modality to quantitatively map the local variations of tissue-level bone elasticity.

  13. The nano-epsilon dot method for strain rate viscoelastic characterisation of soft biomaterials by spherical nano-indentation.

    PubMed

    Mattei, G; Gruca, G; Rijnveld, N; Ahluwalia, A

    2015-10-01

    Nano-indentation is widely used for probing the micromechanical properties of materials. Based on the indentation of surfaces using probes with a well-defined geometry, the elastic and viscoelastic constants of materials can be determined by relating indenter geometry and measured load and displacement to parameters which represent stress and deformation. Here we describe a method to derive the viscoelastic properties of soft hydrated materials at the micro-scale using constant strain rates and stress-free initial conditions. Using a new self-consistent definition of indentation stress and strain and corresponding unique depth-independent expression for indentation strain rate, the epsilon dot method, which is suitable for bulk compression testing, is transformed to nano-indentation. We demonstrate how two materials can be tested with a displacement controlled commercial nano-indentor using the nano-espilon dot method (nano-ε̇M) to give values of instantaneous and equilibrium elastic moduli and time constants with high precision. As samples are tested in stress-free initial conditions, the nano-ε̇M could be useful for characterising the micro-mechanical behaviour of soft materials such as hydrogels and biological tissues at cell length scales.

  14. Molecular dynamics investigations of mechanical behaviours in monocrystalline silicon due to nanoindentation at cryogenic temperatures and room temperature

    PubMed Central

    Du, Xiancheng; Zhao, Hongwei; Zhang, Lin; Yang, Yihan; Xu, Hailong; Fu, Haishuang; Li, Lijia

    2015-01-01

    Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K. Furthermore, the load-displacement curves were obtained and the phase transformation was investigated at different temperatures. The results show that the phase transformation occurs both at cryogenic temperatures and at room temperature. By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process. The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter. Moreover, through the degree of alignment of the metastable phases along specific crystal orientation at different temperatures, it was found that the temperature had effect on the anisotropy of the monocrystalline silicon, and the simulation results indicate that the anisotropy of monocrystalline silicon is strengthened at low temperatures. PMID:26537978

  15. Nanoindentation of the pristine and irradiated forms of a sodium borosilicate glass: Insights from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Kilymis, D. A.; Delaye, J.-M.; Ispas, S.

    2016-07-01

    We have carried out classical molecular dynamics simulations in order to get insight into the atomistic mechanisms of the deformation during nanoindentation of the pristine and irradiated forms of a sodium borosilicate glass. In terms of the glass hardness, we have found that the primary factor affecting the decrease of hardness after irradiation is depolymerization rather than free volume, and we argue that this is a general trend applicable to other borosilicate glasses with similar compositions. We have analyzed the changes of the short- and medium-range structures under deformation and found that the creation of oxygen triclusters is an important mechanism in order to describe the deformation of highly polymerized borosilicate glasses and is essential in the understanding of the folding of large rings under stress. We have equally found that the less polymerized glasses present a higher amount of relative densification, while the analysis of bond-breaking during the nanoindentation has showed that shear flow is more likely to appear around sodium atoms. The results provided in this study can be proven to be useful in the interpretation of experimental results.

  16. Assessment of bulk and surface properties of medical grade UHMWPE based nanocomposites using Nanoindentation and microtensile testing.

    PubMed

    Rama Sreekanth, P S; Kanagaraj, S

    2013-02-01

    A thrust on the enhancement of the mechanical properties of ultra high molecular weight polyethylene (UHMWPE) to enhance its longevity has taken a new direction with the advent of nanomaterials and carbon nanotubes. In the present work, UHMWPE was reinforced by chemically treated multi walled carbon nanotubes (MWCNTs) at different concentrations such as 0.5, 1.0, 1.5, 2.0, 2.5 and 5 wt%. The mechanical properties of nanocomposites were studied using a Nanoindentation technique and micro-tensile testing. It is observed that the toughness, ultimate stress, fracture strain, and yield stress of medical grade UHMWPE were enhanced by 176, 93, 70, and 44%, respectively at an optimum concentration of 2 wt% MWCNTs reinforcement. The mechanism for the enhancement of mechanical properties was confirmed by the micro-Raman and calorimetric technique. The reduction of the mechanical properties of nanocomposites beyond optimum concentration of MWCNTs was confirmed by the rheological studies. The generation of microvoids on the nanocomposites was verified by the scanning electron microscopy technique. Nanoindentation characteristics revealed that the surface hardness of UHMWPE was increased by 75% by the reinforcement of 2 wt% of MWCNTs. The Young's modulus obtained at the surface of nanocomposites was observed to be 9.8% higher than that of surface layer removed sample for 2 wt% nanocomposite. It is concluded that the presence of MWCNTs enhanced the mechanical properties and surface properties of medical grade UHMWPE.

  17. Characterizations of cationic γ-carbolines binding with double-stranded DNA by spectroscopic methods and AFM imaging.

    PubMed

    Jia, Tao; Wang, Jing; Guo, Peng; Yu, Junping

    2015-01-28

    Two cationic γ-carbolines, 2-methyl-5H-pyrido[4,3-b]indolium iodide (MPII) and 2,5-dimethyl-5H-pyrido[4,3-b]indolium iodide (DPII), were synthesized, and the DNA-binding properties of the cationic γ-carbolines were elucidated. Through a series of experiments, we proved that the two cationic γ-carbolines could strongly interact with DNA by intercalative binding. However, DPII, with a methyl group substituting H atom of 5-NH, has shown a stronger intercalative interaction with DNA compared to MPII. The dissociation of H from the 5-NH of MPII resulted in better water solubility and less binding affinity to DNA. Atomic force microscopy (AFM) images of pBR322 showed that both MPII and DPII strongly interacted with DNA and induced conformational changes in DNA. Moreover, the CT-DNA circular dichroism (CD) spectra changes and the statistics of the node numbers of pBR322 in AFM images indicated that MPII had more profound effects on DNA conformations compared to DPII. Furthermore, our studies have shown that the interactions between cationic γ-carbolines and DNA were sensitive to ionic strength. Increased ionic strength in the buffer caused the DNA helix to shrink, and the base stacking would be more compact, which resulted in minimal intercalation of cationic γ-carbolines into DNA.

  18. Bi-stability of amplitude modulation AFM in air: deterministic and stochastic outcomes for imaging biomolecular systems.

    PubMed

    Santos, Sergio; Barcons, Victor; Font, Josep; Thomson, Neil H

    2010-06-01

    The dynamics of the oscillating microcantilever for amplitude modulation atomic force microscopy (AM AFM) operating in air is well understood theoretically but the experimental outcomes are still emerging. We use double-stranded DNA on mica as a model biomolecular system for investigating the connection between theory and experiment. A demonstration that the switching between the two cantilever oscillation states is stochastic in nature is achieved, and it can be induced by means of topographical anomalies on the surface. Whether one or the other attractor basin is accessed depends on the tip-sample separation history used to achieve the imaging conditions, and we show that the behaviour is reproducible when the tip is stable and well characterized. Emergence of background noise occurs in certain regions of parameter space regardless of whether two cantilever oscillation states coexist. The low state has been explored in detail and we note that at low to intermediate values of the free amplitude, noise-free imaging is achieved. The outcomes shown here are general and demonstrate that a thorough and systematic experimental approach in conjunction with standard modelling gives insight into the mechanisms behind image contrast formation in AM AFM in air. PMID:20453275

  19. Bi-stability of amplitude modulation AFM in air: deterministic and stochastic outcomes for imaging biomolecular systems.

    PubMed

    Santos, Sergio; Barcons, Victor; Font, Josep; Thomson, Neil H

    2010-06-01

    The dynamics of the oscillating microcantilever for amplitude modulation atomic force microscopy (AM AFM) operating in air is well understood theoretically but the experimental outcomes are still emerging. We use double-stranded DNA on mica as a model biomolecular system for investigating the connection between theory and experiment. A demonstration that the switching between the two cantilever oscillation states is stochastic in nature is achieved, and it can be induced by means of topographical anomalies on the surface. Whether one or the other attractor basin is accessed depends on the tip-sample separation history used to achieve the imaging conditions, and we show that the behaviour is reproducible when the tip is stable and well characterized. Emergence of background noise occurs in certain regions of parameter space regardless of whether two cantilever oscillation states coexist. The low state has been explored in detail and we note that at low to intermediate values of the free amplitude, noise-free imaging is achieved. The outcomes shown here are general and demonstrate that a thorough and systematic experimental approach in conjunction with standard modelling gives insight into the mechanisms behind image contrast formation in AM AFM in air.

  20. Improving the Lateral Resolution of Quartz Tuning Fork-Based Sensors in Liquid by Integrating Commercial AFM Tips into the Fiber End

    PubMed Central

    Gonzalez, Laura; Martínez-Martín, David; Otero, Jorge; de Pablo, Pedro José; Puig-Vidal, Manel; Gómez-Herrero, Julio

    2015-01-01

    The use of quartz tuning fork sensors as probes for scanning probe microscopy is growing in popularity. Working in shear mode, some methods achieve a lateral resolution comparable with that obtained with standard cantilevered probes, but only in experiments conducted in air or vacuum. Here, we report a method to produce and use commercial AFM tips in electrically driven quartz tuning fork sensors operating in shear mode in a liquid environment. The process is based on attaching a standard AFM tip to the end of a fiber probe which has previously been sharpened. Only the end of the probe is immersed in the buffer solution during imaging. The lateral resolution achieved is about 6 times higher than that of the etched microfiber on its own. PMID:25594596

  1. Improving the lateral resolution of quartz tuning fork-based sensors in liquid by integrating commercial AFM tips into the fiber end.

    PubMed

    Gonzalez, Laura; Martínez-Martín, David; Otero, Jorge; de Pablo, Pedro José; Puig-Vidal, Manel; Gómez-Herrero, Julio

    2015-01-14

    The use of quartz tuning fork sensors as probes for scanning probe microscopy is growing in popularity. Working in shear mode, some methods achieve a lateral resolution comparable with that obtained with standard cantilevered probes, but only in experiments conducted in air or vacuum. Here, we report a method to produce and use commercial AFM tips in electrically driven quartz tuning fork sensors operating in shear mode in a liquid environment. The process is based on attaching a standard AFM tip to the end of a fiber probe which has previously been sharpened. Only the end of the probe is immersed in the buffer solution during imaging. The lateral resolution achieved is about 6 times higher than that of the etched microfiber on its own.

  2. Development of a 3D-AFM for true 3D measurements of nanostructures

    NASA Astrophysics Data System (ADS)

    Dai, Gaoliang; Häßler-Grohne, Wolfgang; Hüser, Dorothee; Wolff, Helmut; Danzebrink, Hans-Ulrich; Koenders, Ludger; Bosse, Harald

    2011-09-01

    The development of advanced lithography requires highly accurate 3D metrology methods for small line structures of both wafers and photomasks. Development of a new 3D atomic force microscopy (3D-AFM) with vertical and torsional oscillation modes is introduced in this paper. In its configuration, the AFM probe is oscillated using two piezo actuators driven at vertical and torsional resonance frequencies of the cantilever. In such a way, the AFM tip can probe the surface with a vertical and a lateral oscillation, offering high 3D probing sensitivity. In addition, a so-called vector approach probing (VAP) method has been applied. The sample is measured point-by-point using this method. At each probing point, the tip is approached towards the surface until the desired tip-sample interaction is detected and then immediately withdrawn from the surface. Compared to conventional AFMs, where the tip is kept continuously in interaction with the surface, the tip-sample interaction time using the VAP method is greatly reduced and consequently the tip wear is reduced. Preliminary experimental results show promising performance of the developed system. A measurement of a line structure of 800 nm height employing a super sharp AFM tip could be performed with a repeatability of its 3D profiles of better than 1 nm (p-v). A line structure of a Physikalisch-Technische Bundesanstalt photomask with a nominal width of 300 nm has been measured using a flared tip AFM probe. The repeatability of the middle CD values reaches 0.28 nm (1σ). A long-term stability investigation shows that the 3D-AFM has a high stability of better than 1 nm within 197 measurements taken over 30 h, which also confirms the very low tip wear.

  3. AFM probes fabricated with masked maskless combined anisotropic etching and p+ surface doping

    NASA Astrophysics Data System (ADS)

    Han, Jianqiang; Li, Xinxin; Bao, Haifei; Zuo, Guomin; Wang, Yuelin; Feng, Fei; Yu, Zhenyin; Ge, Xiaohong

    2006-02-01

    The paper presents a newly developed high-yield micro-fabrication technology for single-crystalline silicon atomic force microscope (AFM) probes. Both the tips and the cantilevers are simultaneously formed by a masked-maskless combined anisotropic etching process. Compared to a conventional tip-to-cantilever sequential fabrication scheme, this tip-and-cantilever simultaneous formation can effectively increase fabrication yield by avoiding the tips damaged during the following processed photolithographic steps for defining the cantilevers. By heavy boron doping at the surface, the conductive AFM probe provides an electrical path to the electric ground of the AFM that helps to eliminate the electrostatic accumulation of charges and, therefore, eliminate undesirable electrostatic forces between the probes and the samples. A fabrication yield as high as 90% has been obtained for the AFM probes for 4 inch wafers. The tips after oxidation-sharpening treatment generally have a radius of 10-30 nm. The cantilever spring constant can be well controlled in the range of 0.025-40 N m-1. High-quality sample scanning results with the formed AFM probes are obtained with a slightly better resolution than that from commercial probes without surface conductive treatment.

  4. AFM1 in Milk: Physical, Biological, and Prophylactic Methods to Mitigate Contamination

    PubMed Central

    Giovati, Laura; Magliani, Walter; Ciociola, Tecla; Santinoli, Claudia; Conti, Stefania; Polonelli, Luciano

    2015-01-01

    Aflatoxins (AFs) are toxic, carcinogenic, immunosuppressive secondary metabolites produced by some Aspergillus species which colonize crops, including many dietary staple foods and feed components. AFB1 is the prevalent and most toxic among AFs. In the liver, it is biotransformed into AFM1, which is then excreted into the milk of lactating mammals, including dairy animals. AFM1 has been shown to be cause of both acute and chronic toxicoses. The presence of AFM1 in milk and dairy products represents a worldwide concern since even small amounts of this metabolite may be of importance as long-term exposure is concerned. Contamination of milk may be mitigated either directly, decreasing the AFM1 content in contaminated milk, or indirectly, decreasing AFB1 contamination in the feed of dairy animals. Current strategies for AFM1 mitigation include good agricultural practices in pre-harvest and post-harvest management of feed crops (including storage) and physical or chemical decontamination of feed and milk. However, no single strategy offers a complete solution to the issue. PMID:26512694

  5. Fractal analysis of AFM images of the surface of Bowman's membrane of the human cornea.

    PubMed

    Ţălu, Ştefan; Stach, Sebastian; Sueiras, Vivian; Ziebarth, Noël Marysa

    2015-04-01

    The objective of this study is to further investigate the ultrastructural details of the surface of Bowman's membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman's membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution. Height and deflection images were acquired at multiple scan lengths using the MFP-3D AFM system software (Asylum Research, Santa Barbara, CA), based in IGOR Pro (WaveMetrics, Lake Oswego, OR). A novel approach, based on computational algorithms for fractal analysis of surfaces applied for AFM data, was utilized to analyze the surface structure. The surfaces revealed a fractal structure at the nanometer scale. The fractal dimension, D, provided quantitative values that characterize the scale properties of surface geometry. Detailed characterization of the surface topography was obtained using statistical parameters, in accordance with ISO 25178-2: 2012. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. The surface structure of Bowman's membrane of the human cornea is complex. The analyzed AFM images confirm a fractal nature of the surface, which is not taken into account by classical surface statistical parameters. Surface fractal dimension could be useful in ophthalmology to quantify corneal architectural changes associated with different disease states to further our understanding of disease evolution.

  6. Evaluation of hardening behaviors in ion-irradiated Fe-9Cr and Fe-20Cr alloys by nanoindentation technique

    NASA Astrophysics Data System (ADS)

    Li, Shilei; Wang, Yanli; Dai, Xianyuan; Liu, Fang; Li, Jinyu; Wang, Xitao

    2016-09-01

    The ion irradiation hardening behaviors of Fe-9 wt% Cr and Fe-20 wt% Cr model alloys were investigated by nanoindentation technique. The specimens were irradiated with 3 MeV Fe11+ ions at room temperature up to 1 and 5 dpa for Fe-9Cr alloy and 1 and 2.5 for Fe-20Cr alloy. The ratio of average hardness in the same depth of irradiated and unirradiated (Hirr. av/Hunirr. av) was used to determine the critical indentation depth hcrit to eliminate the softer substrate effect. The Nix-Gao model was used to explain the indentation size effect. Irradiation hardening is clearly observed in both Fe-9Cr alloy and Fe-20Cr alloy after ion irradiation. The differences of ISE and irradiation hardening behaviors between Fe-9Cr and Fe-20Cr alloys are considered to be due to their different microstructures and microstructural evolution under ion irradiation.

  7. Phase Transformation Evolution in NiTi Shape Memory Alloy under Cyclic Nanoindentation Loadings at Dissimilar Rates

    PubMed Central

    Amini, Abbas; Cheng, Chun; Kan, Qianhua; Naebe, Minoo; Song, Haisheng

    2013-01-01

    Hysteresis energy decreased significantly as nanocrystalline NiTi shape memory alloy was under triangular cyclic nanoindentation loadings at high rate. Jagged curves evidenced discrete stress relaxations. With a large recovery state of maximum deformation in each cycle, this behavior concluded in several nucleation sites of phase transformation in stressed bulk. Additionally, the higher initial propagation velocity of interface and thermal activation volume, and higher levels of phase transition stress in subsequent cycles explained the monotonic decreasing trend of dissipated energy. In contrast, the dissipated energy showed an opposite increasing trend during triangular cyclic loadings at a low rate and 60 sec holding time after each unloading stage. Due to the isothermal loading rate and the holding time, a major part of the released latent heat was transferred during the cyclic loading resulting in an unchanged phase transition stress. This fact with the reorientation phenomenon explained the monotonic increasing trend of hysteresis energy. PMID:24336228

  8. Effective properties of a fly ash geopolymer: Synergistic application of X-ray synchrotron tomography, nanoindentation, and homogenization models

    SciTech Connect

    Das, Sumanta; Yang, Pu; Singh, Sudhanshu S.; Mertens, James C. E.; Xiao, Xianghui; Chawla, Nikhilesh; Neithalath, Narayanan

    2015-09-02

    Microstructural and micromechanical investigation of a fly ash-based geopolymer using: (i) synchrotron x-ray tomography (XRT) to determine the volume fraction and tortuosity of pores that are influential in fluid transport, (ii) mercury intrusion porosimetry (MIP) to capture the volume fraction of smaller pores, (iii) scanning electron microscopy (SEM) combined with multi-label thresholding to identify and characterize the solid phases in the microstructure, and (iv) nanoindentation to determine the component phase elastic properties using statistical deconvolution, is reported in this paper. The phase volume fractions and elastic properties are used in multi-step mean field homogenization (Mori- Tanaka and double inclusion) models to determine the homogenized macroscale elastic modulus of the composite. The homogenized elastic moduli are in good agreement with the flexural elastic modulus determined on macroscale paste beams. As a result, the combined use of microstructural and micromechanical characterization tools at multiple scales provides valuable information towards the material design of fly ash geopolymers.

  9. Phase transformation evolution in NiTi shape memory alloy under cyclic nanoindentation loadings at dissimilar rates.

    PubMed

    Amini, Abbas; Cheng, Chun; Kan, Qianhua; Naebe, Minoo; Song, Haisheng

    2013-12-13

    Hysteresis energy decreased significantly as nanocrystalline NiTi shape memory alloy was under triangular cyclic nanoindentation loadings at high rate. Jagged curves evidenced discrete stress relaxations. With a large recovery state of maximum deformation in each cycle, this behavior concluded in several nucleation sites of phase transformation in stressed bulk. Additionally, the higher initial propagation velocity of interface and thermal activation volume, and higher levels of phase transition stress in subsequent cycles explained the monotonic decreasing trend of dissipated energy. In contrast, the dissipated energy showed an opposite increasing trend during triangular cyclic loadings at a low rate and 60 sec holding time after each unloading stage. Due to the isothermal loading rate and the holding time, a major part of the released latent heat was transferred during the cyclic loading resulting in an unchanged phase transition stress. This fact with the reorientation phenomenon explained the monotonic increasing trend of hysteresis energy.

  10. The physics of pulling polyproteins: a review of single molecule force spectroscopy using the AFM to study protein unfolding

    NASA Astrophysics Data System (ADS)

    Hughes, Megan L.; Dougan, Lorna

    2016-07-01

    One of the most exciting developments in the field of biological physics in recent years is the ability to manipulate single molecules and probe their properties and function. Since its emergence over two decades ago, single molecule force spectroscopy has become a powerful tool to explore the response of biological molecules, including proteins, DNA, RNA and their complexes, to the application of an applied force. The force versus extension response of molecules can provide valuable insight into its mechanical stability, as well as details of the underlying energy landscape. In this review we will introduce the technique of single molecule force spectroscopy using the atomic force microscope (AFM), with particular focus on its application to study proteins. We will review the models which have been developed and employed to extract information from single molecule force spectroscopy experiments. Finally, we will end with a discussion of future directions in this field.

  11. The physics of pulling polyproteins: a review of single molecule force spectroscopy using the AFM to study protein unfolding.

    PubMed

    Hughes, Megan L; Dougan, Lorna

    2016-07-01

    One of the most exciting developments in the field of biological physics in recent years is the ability to manipulate single molecules and probe their properties and function. Since its emergence over two decades ago, single molecule force spectroscopy has become a powerful tool to explore the response of biological molecules, including proteins, DNA, RNA and their complexes, to the application of an applied force. The force versus extension response of molecules can provide valuable insight into its mechanical stability, as well as details of the underlying energy landscape. In this review we will introduce the technique of single molecule force spectroscopy using the atomic force microscope (AFM), with particular focus on its application to study proteins. We will review the models which have been developed and employed to extract information from single molecule force spectroscopy experiments. Finally, we will end with a discussion of future directions in this field.

  12. AFM characterization of nonwoven material functionalized by ZnO sputter coating

    SciTech Connect

    Deng Bingyao; Yan Xiong; Wei Qufu Gao Weidong

    2007-10-15

    Sputter coatings provide new approaches to the surface functionalization of textile materials. In this study, polyethylene terephthalate (PET) nonwoven material was used as a substrate for creating functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit functional zinc oxide (ZnO) nanostructures onto the nonwoven substrate. The evolution of the surface morphology of the fibers in the nonwoven web was examined using atomic force microscopy (AFM). The AFM observations revealed a significant difference in the morphology of the fibers before and after the sputter coating. The AFM images also indicated the effect of the sputtering conditions on the surface morphology of the fibers. The increase in the sputtering time led to the growth of the ZnO grains on the fiber surfaces. The higher pressure in the sputtering chamber could cause the formation of larger grains on the fiber surfaces. The higher power used also generated larger grains on the fiber surfaces.

  13. Quantitative atomic resolution force imaging on epitaxial graphene with reactive and nonreactive AFM probes.

    PubMed

    Boneschanscher, Mark P; van der Lit, Joost; Sun, Zhixiang; Swart, Ingmar; Liljeroth, Peter; Vanmaekelbergh, Daniël

    2012-11-27

    Atomic force microscopy (AFM) images of graphene and graphite show contrast with atomic periodicity. However, the contrast patterns vary depending on the atomic termination of the AFM tip apex and the tip-sample distance, hampering the identification of the atomic positions. Here, we report quantitative AFM imaging of epitaxial graphene using inert (carbon-monoxide-terminated) and reactive (iridium-terminated) tips. The atomic image contrast is markedly different with these tip terminations. With a reactive tip, we observe an inversion from attractive to repulsive atomic contrast with decreasing tip-sample distance, while a nonreactive tip only yields repulsive atomic contrast. We are able to identify the atoms with both tips at any tip-sample distance. This is a prerequisite for future structural and chemical analysis of adatoms, defects, and the edges of graphene nanostructures, crucial for understanding nanoscale graphene devices.

  14. Imaging and force measurement of LDL and HDL by AFM in air and liquid

    PubMed Central

    Gan, Chaoye; Ao, Meiying; Liu, Zhanghua; Chen, Yong

    2015-01-01

    The size and biomechanical properties of lipoproteins are tightly correlated with their structures/functions. While atomic force microscopy (AFM) has been used to image lipoproteins the force measurement of these nano-sized particles is missing. We detected that the sizes of LDL and HDL in liquid are close to the commonly known values. The Young’s modulus of LDL or HDL is ∼0.4 GPa which is similar to that of some viral capsids or nanovesicles but greatly larger than that of various liposomes. The adhesive force of LDL or HDL is small (∼200 pN). The comparison of AFM detection in air and liquid was also performed which is currently lacking. Our data may provide useful information for better understanding and AFM detection of lipoproteins. PMID:25893163

  15. Mapping site-specific endonuclease binding to DNA by direct imaging with AFM

    SciTech Connect

    Allison, D.P.; Thundat, T.; Doktycz, M.J.; Kerper, P.S.; Warmack, R.J.; Modrich, P.; Isfort, R.J.

    1995-12-31

    Physical mapping of DNA can be accomplished by direct AFM imaging of site specific proteins bound to DNA molecules. Using Gln-111, a mutant of EcoRI endonuclease with a specific affinity for EcoRI sites 1,000 times greater than wild type enzyme but with cleavage rate constants reduced by a factor of 10{sup 4}, the authors demonstrate site-specific mapping by direct AFM imaging. Images are presented showing specific-site binding of Gln-111 to plasmids having either one (pBS{sup +}) or two (pMP{sup 32}) EcoRI sites. Identification of the Gln-111/DNA complex is greatly enhanced by biotinylation of the complex followed by reaction with streptavidin gold prior to imaging. Image enhancement coupled with improvements in the preparation techniques for imaging large DNA molecules, such as lambda DNA (47 kb), has the potential to contribute to direct AFM restriction mapping of cosmid-sized genomic DNAs.

  16. Review and perspectives of AFM application on the study of deformable drop/bubble interactions.

    PubMed

    Wang, Wei; Li, Kai; Ma, Mengyu; Jin, Hang; Angeli, Panagiota; Gong, Jing

    2015-11-01

    The applications of Atomic Force Microscopy (AFM) on the study of dynamic interactions and film drainage between deformable bodies dispersed in aqueous solutions are reviewed in this article. Novel experimental designs and recent advances in experimental methodologies are presented, which show the advantage of using AFM as a tool for probing colloidal interactions. The effects of both DLVO and non-DLVO forces on the colloid stabilization mechanism are discussed. Good agreement is found between the force - drop/bubble deformation behaviour revealed by AFM measurements and the theoretical modeling of film drainage process, giving a convincing explanation of the occurrence of certain phenomenon. However, the behaviour and shape of deformable drops as they approach or retract is still not well resolved. In addition, when surfactants are present further research is needed on the absorption of surfactant molecules into the interfaces, their mobility and the effects on interfacial film properties.

  17. Mapping site-specific endonuclease binding to DNA by direct imaging with atomic force microscopy (AFM)

    NASA Astrophysics Data System (ADS)

    Allison, David P.; Thundat, Thomas G.; Modrich, P.; Isfort, R. J.; Doktycz, Mitchel J.; Kerper, P. S.; Warmack, R. J.

    1995-04-01

    Physical mapping of DNA can be accomplished by direct AFM imaging of site specific proteins bound to DNA molecules. Using Gln-111, a mutant of EcoRI endonuclease with a specific affinity for EcoRI sites 1000 times greater than wild type enzyme but with cleavage rate constants reduced by a factor of 104, we demonstrate site-specific mapping by direct AFM imaging. Images are presented showing specific-site binding of Gln-111 to plasmids having either one (pBS+) or two (pMP32) EcoRI sites. Identification of the Gln-111/DNA complex is greatly enhanced by biotinylation of the complex followed by reaction with streptavidin gold prior to imaging. Image enhancement coupled with improvements in our preparation techniques for imaging large DNA molecules, such as lambda DNA (47 kb), has the potential to contribute to direct AFM restriction mapping of cosmid-sized genomic DNAs.

  18. AFM-assisted fabrication of thiol SAM pattern with alternating quantified surface potential

    PubMed Central

    2011-01-01

    Thiol self-assembled monolayers (SAMs) are widely used in many nano- and bio-technology applications. We report a new approach to create and characterize a thiol SAMs micropattern with alternating charges on a flat gold-coated substrate using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We produced SAMs-patterns made of alternating positively charged, negatively charged, and hydrophobic-terminated thiols by an automated AFM-assisted manipulation, or nanografting. We show that these thiol patterns possess only small topographical differences as revealed by AFM, and distinguished differences in surface potential (20-50 mV), revealed by KPFM. The pattern can be helpful in the development of biosensor technologies, specifically for selective binding of biomolecules based on charge and hydrophobicity, and serve as a model for creating surfaces with quantified alternating surface potential distribution. PMID:21711703

  19. Mechanism of immonoglobulin G adsorption on mica-AFM and electrokinetic studies.

    PubMed

    Dąbkowska, Maria; Adamczyk, Zbigniew

    2014-06-01

    Adsorption of immunoglobulin G (IgG) from aqueous NaCl solutions of the concentration 10(-3)-0.15M on mica was studied. Initially, the kinetics was evaluated at pH 3.5 by direct AFM imaging. A monotonic increase in the maximum coverage of IgG with NaCl concentration was observed. These results were interpreted in terms of the theoretical model postulating an irreversible adsorption of the protein governed by the random sequential adsorption (RSA) model. Additionally, IgG adsorption and desorption was studied under in situ conditions, with streaming potential measurements. These measurements revealed that the maximum coverage of irreversibly adsorbed IgG varies from 0.37mgm(-2) for 10(-3)M, NaCl to 1.2mgm(-2) for 0.15M, NaCl. The significant role of ionic strength was attributed to the lateral electrostatic repulsion among adsorbed IgG molecules, positively charged at this pH value. These experimental results confirmed that monolayers of irreversibly bound IgG can be produced by adjusting ionic strength of the protein solution. In further experiments the stability and acid base properties of such monolayers were studied using the streaming potential method. It revealed that the monolayers were stable against pH cycling for the range from 3.5 to 9.5. The isoelectric point of mica supported IgG monolayers was 5.9, similar to derived from the micro-electrophoretic measurements in the bulk (5.8). Beside significance for basic sciences, the results indicate that thorough characteristics of IgG can be acquired via streaming potential measurements using microgram quantities of the protein.

  20. Protein Nanocontainers from Nonviral Origin: Testing the Mechanics of Artificial and Natural Protein Cages by AFM.

    PubMed

    Heinze, K; Sasaki, E; King, N P; Baker, D; Hilvert, D; Wuite, G J L; Roos, W H

    2016-07-01

    Self-assembling protein nanocontainers are promising candidates for an increasingly wide scope of purposes. Their applications range from drug delivery vehicles and imaging agents to nanocompartments for controlled enzymatic activity. In order to exploit their full potential in these different fields, characterization of their properties is vital. For example, their mechanical properties give insight into the stability of a particle as a function of their internal content. The mechanics can be probed by atomic force microscopy nanoindentation, and while this single particle method is increasingly used to probe material properties of viral nanocages, it has hardly been used to characterize nonviral nanocages. Here we report nanoindentation studies on two types of nonviral nanocontainers: (i) lumazine synthase from Aquifex aeolicus (AaLS), which naturally self-assembles into icosahedral cages, and (ii) the artificial protein cage O3-33 originating from a computational design approach. In addition, we tested particles that had been engineered toward improved cargo loading capacity and compared these nanocages in empty and loaded states. We found that the thermostable AaLS cages are stiffer and resist higher forces before breaking than the O3-33 particles, but that mutations affecting the size of AaLS particles have a dramatic effect on their structural stability. Furthermore, we show that cargo packaging can occur while maintaining the cage's mechanical properties. PMID:27187612

  1. FRAME (Force Review Automation Environment): MATLAB-based AFM data processor.

    PubMed

    Partola, Kostyantyn R; Lykotrafitis, George

    2016-05-01

    Data processing of force-displacement curves generated by atomic force microscopes (AFMs) for elastic moduli and unbinding event measurements is very time consuming and susceptible to user error or bias. There is an evident need for consistent, dependable, and easy-to-use AFM data processing software. We have developed an open-source software application, the force review automation environment (or FRAME), that provides users with an intuitive graphical user interface, automating data processing, and tools for expediting manual processing. We did not observe a significant difference between manually processed and automatically processed results from the same data sets.

  2. FRAME (Force Review Automation Environment): MATLAB-based AFM data processor.

    PubMed

    Partola, Kostyantyn R; Lykotrafitis, George

    2016-05-01

    Data processing of force-displacement curves generated by atomic force microscopes (AFMs) for elastic moduli and unbinding event measurements is very time consuming and susceptible to user error or bias. There is an evident need for consistent, dependable, and easy-to-use AFM data processing software. We have developed an open-source software application, the force review automation environment (or FRAME), that provides users with an intuitive graphical user interface, automating data processing, and tools for expediting manual processing. We did not observe a significant difference between manually processed and automatically processed results from the same data sets. PMID:26972765

  3. Direct visualization of the trimeric structure of the ASIC1a channel, using AFM imaging

    SciTech Connect

    Carnally, Stewart M.; Dev, Harveer S.; Stewart, Andrew P.; Barrera, Nelson P.; Van Bemmelen, Miguel X.; Schild, Laurent; Henderson, Robert M.; Edwardson, J.Michael

    2008-08-08

    There has been confusion about the subunit stoichiometry of the degenerin family of ion channels. Recently, a crystal structure of acid-sensing ion channel (ASIC) 1a revealed that it assembles as a trimer. Here, we used atomic force microscopy (AFM) to image unprocessed ASIC1a bound to mica. We detected a mixture of subunit monomers, dimers and trimers. In some cases, triple-subunit clusters were clearly visible, confirming the trimeric structure of the channel, and indicating that the trimer sometimes disaggregated after adhesion to the mica surface. This AFM-based technique will now enable us to determine the subunit arrangement within heteromeric ASICs.

  4. Coexistence of orbital and CE-AFM orders in colossal magnetoresistance manganites: A symmetry perspective

    NASA Astrophysics Data System (ADS)

    Ribeiro, J. L.

    2016-07-01

    The complex interplay between order parameters of different nature that dominates the physics of colossal magnetoresistance manganites is analysed from a symmetry based perspective. Phenomenological energies are given for the different competing phases. It is shown that the general trends observed in different systems, such as the mutual exclusion of orbital order and A-AFM order and the related stabilization of the CE-AFM order, stem to large extend from the symmetry of the parameters involved. The possible stabilization of complex phases where charge and orbital order coexist with magnetic and ferroelectric states is also anticipated.

  5. Probing the PEDOT:PSS/cell interface with conductive colloidal probe AFM-SECM

    NASA Astrophysics Data System (ADS)

    Knittel, P.; Zhang, H.; Kranz, C.; Wallace, G. G.; Higgins, M. J.

    2016-02-01

    Conductive colloidal probe Atomic Force-Scanning Electrochemical Microscopy (AFM-SECM) is a new approach, which employs electrically insulated AFM probes except for a gold-coated colloid located at the end of the cantilever. Hence, force measurements can be performed while biasing the conductive colloid under physiological conditions. Moreover, such colloids can be modified by electrochemical polymerization resulting, e.g. in conductive polymer-coated spheres, which in addition may be loaded with specific dopants. In contrast to other AFM-based single cell force spectroscopy measurements, these probes allow adhesion measurements at the cell-biomaterial interface on multiple cells in a rapid manner while the properties of the polymer can be changed by applying a bias. In addition, spatially resolved electrochemical information e.g., oxygen reduction can be obtained simultaneously. Conductive colloid AFM-SECM probes modified with poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) are used for single cell force measurements in mouse fibroblasts and single cell interactions are investigated as a function of the applied potential.Conductive colloidal probe Atomic Force-Scanning Electrochemical Microscopy (AFM-SECM) is a new approach, which employs electrically insulated AFM probes except for a gold-coated colloid located at the end of the cantilever. Hence, force measurements can be performed while biasing the conductive colloid under physiological conditions. Moreover, such colloids can be modified by electrochemical polymerization resulting, e.g. in conductive polymer-coated spheres, which in addition may be loaded with specific dopants. In contrast to other AFM-based single cell force spectroscopy measurements, these probes allow adhesion measurements at the cell-biomaterial interface on multiple cells in a rapid manner while the properties of the polymer can be changed by applying a bias. In addition, spatially resolved electrochemical

  6. Resonance Frequency Analysis for Surface-Coupled AFM Cantilever in Liquids

    SciTech Connect

    Mirman, B; Kalinin, Sergei V

    2008-01-01

    Shifts in the resonance frequencies of surface-coupled atomic force microscope (AFM) probes are used as the basis for the detection mechanisms in a number of scanning probe microscopy techniques including atomic force acoustic microscopy (AFAM), force modulation microscopy, and resonance enhanced piezoresponse force microscopy (PFM). Here, we analyze resonance characteristics for AFM cantilever coupled to surface in liquid environment, and derive approximate expressions for resonant frequencies as a function of vertical and lateral spring constant of the tip-surface junction. This analysis provides a simplified framework for the interpretation of AFAM and PFM data in ambient, liquid, and vacuum environments.

  7. Studying post-etching silicon crystal defects on 300mm wafer by automatic defect review AFM

    NASA Astrophysics Data System (ADS)

    Zandiatashbar, Ardavan; Taylor, Patrick A.; Kim, Byong; Yoo, Young-kook; Lee, Keibock; Jo, Ahjin; Lee, Ju Suk; Cho, Sang-Joon; Park, Sang-il

    2016-03-01

    Single crystal silicon wafers are the fundamental elements of semiconductor manufacturing industry. The wafers produced by Czochralski (CZ) process are very high quality single crystalline materials with known defects that are formed during the crystal growth or modified by further processing. While defects can be unfavorable for yield for some manufactured electrical devices, a group of defects like oxide precipitates can have both positive and negative impacts on the final device. The spatial distribution of these defects may be found by scattering techniques. However, due to limitations of scattering (i.e. light wavelength), many crystal defects are either poorly classified or not detected. Therefore a high throughput and accurate characterization of their shape and dimension is essential for reviewing the defects and proper classification. While scanning electron microscopy (SEM) can provide high resolution twodimensional images, atomic force microscopy (AFM) is essential for obtaining three-dimensional information of the defects of interest (DOI) as it is known to provide the highest vertical resolution among all techniques [1]. However AFM's low throughput, limited tip life, and laborious efforts for locating the DOI have been the limitations of this technique for defect review for 300 mm wafers. To address these limitations of AFM, automatic defect review AFM has been introduced recently [2], and is utilized in this work for studying DOI on 300 mm silicon wafer. In this work, we carefully etched a 300 mm silicon wafer with a gaseous acid in a reducing atmosphere at a temperature and for a sufficient duration to decorate and grow the crystal defects to a size capable of being detected as light scattering defects [3]. The etched defects form a shallow structure and their distribution and relative size are inspected by laser light scattering (LLS). However, several groups of defects couldn't be properly sized by the LLS due to the very shallow depth and low

  8. AFM and XPA data on structural features and properties of films and powders based on naphthalocyanines

    NASA Astrophysics Data System (ADS)

    Ramonova, A. G.; Nakusov, A. T.; Sozanov, V. G.; Bliev, A. P.; Magkoev, T. T.

    2015-06-01

    The template synthesis is used to produce powders and films based on naphthalocyanines and the corresponding metal complexes (Pc, CuPc, and NiPc). The atomic-force microscopy (AFM) and X-ray phase analysis (XPA) are employed in the study of structure and phase of fine powders and nanostructured films. The AFM data are used to determine the orientation and density of primary particles packed in the film. The XPA method is used to study the chemical composition and crystal structure of the synthesized samples. The regularities related to the structural features that affect the electrophysical properties of the films under study are revealed.

  9. An Evaluation of the Impacts of AF-M315E Propulsion Systems for Varied Mission Applications

    NASA Technical Reports Server (NTRS)

    Deans, Matthew C.; Oleson, Steven R.; Fittje, James; Colozza, Anthony; Packard, Tom; Gyekenyesi, John; McLean, Christopher H.; Spores, Ronald A.

    2015-01-01

    The purpose of the AF-M315E COMPASS study is to identify near-term (3-5 years) and long term (5 years +) opportunities for infusion, specifically the thruster and associated component technologies being developed as part of the GPIM project. Develop design reference missions which show the advantages of the AF-M315E green propulsion system. Utilize a combination of past COMPASS designs and selected new designs to demonstrate AF-M315E advantages. Use the COMPASS process to show the puts and takes of using AF-M315E at the integrated system level.

  10. Topographic mapping and compression elasticity analysis of skinned cardiac muscle fibers in vitro with atomic force microscopy and nanoindentation.

    PubMed

    Zhu, Jie; Sabharwal, Tanya; Kalyanasundaram, Aruna; Guo, Lianhong; Wang, Guodong

    2009-09-18

    Surface topography and compression elasticity of bovine cardiac muscle fibers in rigor and relaxing state have been studied with atomic force microscopy. Characteristic sarcomere patterns running along the longitudinal axis of the fibers were clearly observed, and Z-lines, M-lines, I-bands, and A-bands can be distinguished through comparing with TEM images and force curves. AFM height images of fibers had shown a sarcomere length of 1.22+/-0.02 microm (n=5) in rigor with a significant 9% increase in sarcomere length in relaxing state (1.33+/-0.03 microm, n=5), indicating that overlap moves with the changing physiological conditions. Compression elasticity curves along with sarcomere locations have been taken by AFM compression processing. Coefficient of Z-line, I-band, Overlap, and M-line are 25+/-2, 8+/-1, 10+/-1, and 17+/-1.5 pN/nm respectively in rigor state, and 18+/-2.5, 4+/-0.5, 6+/-1, and 11+/-0.5 pN/nm respectively in relaxing state. Young's Modulus in Z-line, I-band, Overlap, and M-line are 115+/-12, 48+/-9, 52+/-8, and 90+/-12 kPa respectively in rigor, and 98+/-10, 23+/-4, 42+/-4, and 65+/-7 kPa respectively in relaxing state. The elasticity curves have shown a similar appearance to the section analysis profile of AFM height images of sarcomere and the distance between adjacent largest coefficient and Young's Modulus is equal to the sarcomere length measured from the AFM height images using section analysis, indicating that mechanic properties of fibers have a similar periodicity to the topography of fibers.

  11. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    PubMed

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are

  12. AFM tip characterization by using FFT filtered images of step structures.

    PubMed

    Yan, Yongda; Xue, Bo; Hu, Zhenjiang; Zhao, Xuesen

    2016-01-01

    The measurement resolution of an atomic force microscope (AFM) is largely dependent on the radius of the tip. Meanwhile, when using AFM to study nanoscale surface properties, the value of the tip radius is needed in calculations. As such, estimation of the tip radius is important for analyzing results taken using an AFM. In this study, a geometrical model created by scanning a step structure with an AFM tip was developed. The tip was assumed to have a hemispherical cone shape. Profiles simulated by tips with different scanning radii were calculated by fast Fourier transform (FFT). By analyzing the influence of tip radius variation on the spectra of simulated profiles, it was found that low-frequency harmonics were more susceptible, and that the relationship between the tip radius and the low-frequency harmonic amplitude of the step structure varied monotonically. Based on this regularity, we developed a new method to characterize the radius of the hemispherical tip. The tip radii estimated with this approach were comparable to the results obtained using scanning electron microscope imaging and blind reconstruction methods. PMID:26517548

  13. Controlled AFM detachments and movement of nanoparticles: gold clusters on HOPG at different temperatures.

    PubMed

    Tripathi, Manoj; Paolicelli, Guido; D'Addato, Sergio; Valeri, Sergio

    2012-06-22

    The effect of temperature on the onset of movement of gold nanoclusters (diameter 27 nm) deposited on highly oriented pyrolytic graphite (HOPG) has been studied by atomic force microscopy (AFM) techniques. Using the AFM with amplitude modulation (tapping mode AFM) we have stimulated and controlled the movement of individual clusters. We show how, at room temperature, controlled detachments and smooth movements can be obtained for clusters having dimensions comparable to or smaller than the tip radius. Displacement is practically visible in real time and it can be started and stopped easily by adjusting only one parameter, the tip amplitude oscillation. Analysing the energy dissipation signal at the onset of nanocluster sliding we evaluated a detachment threshold energy as a function of temperature in the range 300-413 K. We also analysed single cluster thermal induced displacement and combining this delicate procedure with AFM forced movement behaviour we conclude that detachment threshold energy is directly related to the activation energy of nanocluster diffusion and it scales linearly with temperature as expected for a single-particle thermally activated process.

  14. Fracture Mechanics Testing of Titanium 6AL-4V in AF-M315E

    NASA Technical Reports Server (NTRS)

    Sampson, J. W.; Martinez, J.; McLean, C.

    2016-01-01

    The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant on orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent processing flaws will not cause failure during the design life of the tank. Material property inputs for this analysis require testing to determine the stress intensity factor for environment-assisted cracking (KEAC) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched, or SE(B), specimens representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to AF-M315E at 50 C for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor for environment-assisted cracking of the Ti 6Al-4V forged tank material was found to be at least 22 ksivin and at least 31 ksivin for the weld material when exposed to AF-M315E monopropellant.

  15. Tapping and contact mode imaging of native chromosomes and extraction of genomic DNA using AFM tips

    NASA Astrophysics Data System (ADS)

    Sun, Yingchun; Arakawa, Hideo; Osada, Toshiya; Ikai, Atsushi

    2002-03-01

    It is very important both in medicine and biology to clarify the chromosomal structure to understand its functions. In a standard cytogenetic procedure, chromosomes are often fixed in a mixture of acetic acid and methanol. This process most likely changes the mechanical property of chromosomes. We adopted a method to prepare native and unfixed chromosomes from mouse 3T3 cells and used tapping and contact mode atomic force microscopy (AFM) to image and manipulate them. Modified AFM tips were used to image chromosomes in contact mode in air, and then the chromosome samples were immobilized on a substrate and placed in a buffer solution to pull out DNA-histone complexes from them after they were optimally treated with trypsin. From the AFM images, we could see several bands and granular structures on chromosomes. We obtained force curves indicating long fiber extensions from native chromosomes both with low (in high concentration of NaCl) and high forces (physiological conditions). The result suggested that the degree of chromosome condensation decreased in high concentration of salt. It agrees with the known fact of histone H1 dissociation in a high concentration of salt. We intend to pull out DNA-histone complexes from chromosomes for later molecular operations on them using an AFM.

  16. The structure of high-methoxyl sugar acid gels of citrus pectin as determined by AFM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Images of native high methoxyl sugar acid gels (HMSAG) were obtained by atomic force microscopy (AFM) in the Tapping ModeTM. Electronic thinning of the pectin strands to one pixel wide allowed the pectin network to be viewed in the absence of variable strand widths related to preferentially solvate...

  17. Accurate calibration and uncertainty estimation of the normal spring constant of various AFM cantilevers.

    PubMed

    Song, Yunpeng; Wu, Sen; Xu, Linyan; Fu, Xing

    2015-03-10

    Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force sensor, and the spring constant of the cantilever is of great significance to the accuracy of the measurement results. This paper presents a normal spring constant calibration method with the combined use of an electromagnetic balance and a homemade AFM head. When the cantilever presses the balance, its deflection is detected through an optical lever integrated in the AFM head. Meanwhile, the corresponding bending force is recorded by the balance. Then the spring constant can be simply calculated using Hooke's law. During the calibration, a feedback loop is applied to control the deflection of the cantilever. Errors that may affect the stability of the cantilever could be compensated rapidly. Five types of commercial cantilevers with different shapes, stiffness, and operating modes were chosen to evaluate the performance of our system. Based on the uncertainty analysis, the expanded relative standard uncertainties of the normal spring constant of most measured cantilevers are believed to be better than 2%.

  18. High spatial resolution surface imaging and analysis of fungal cells using SEM and AFM.

    PubMed

    Kaminskyj, Susan G W; Dahms, Tanya E S

    2008-06-01

    We review the use of scanning electron microscopy (SEM), atomic force microscopy (AFM) and force spectroscopy (FS) for probing the ultrastructure, chemistry, physical characteristics and motion of fungal cells. When first developed, SEM was used to image fixed/dehydrated/gold coated specimens, but here we describe more recent SEM developments as they apply to fungal cells. CryoSEM offers high resolution for frozen fungal samples, whereas environmental SEM allows the analysis of robust samples (e.g. spores) under ambient conditions. Dual beam SEM, the most recently developed, adds manipulation capabilities along with element detection. AFM has similar lateral and better depth resolution compared to SEM, and can image live cells including growing fungal hyphae. FS can analyze cell wall chemistry, elasticity and dynamic cell characteristics. The integration of AFM with optical microscopy will allow examination of individual molecules or cellular structures in the context of fungal cell architecture. SEM and AFM are complementary techniques that are clarifying our understanding of fungal biology. PMID:18068995

  19. Study of Thin Oxide Films with NC-AFM: Atomically Resolved Imaging and Beyond

    NASA Astrophysics Data System (ADS)

    Heyde, M.; Simon, G. H.; König, T.

    Results presented in the following show structural analysis of metaloxide surfaces and the extraction of physical quantities from the force field above such a surface by noncontact atomic force microscopy (NC-AFM). The measurements have been performed with our dual mode NC-AFM/STM in ultrahigh vacuum at 5 K. The introduction will be followed by a description of the experimental setup, including the ultrahigh vacuum cryogenic environment and our tuning fork tunneling current and force sensor. The sensor parameters affecting the measurements are given together with an amplitude characterization method. In the next section, a structure determination of ultrathin Alumina/NiAl(110) is shown. Atomic resolution could be achieved throughout both reflection domain unit cells. NC-AFM reveals details of morphological features, interconnections to substrate-film interactions, and comparability to theory also with respect to topographic height. In the last section, we present measurements beyond imaging, namely spectroscopy data taken on thin MgO films grown on Ag(001). Force-distance measurements based on atomically resolved NC-AFM images of these films have been taken. Inequivalent sites could be resolved and their effect on nucleation and adsorption processes is debated. Furthermore, work function shift measurements on different MgO film thicknesses grown on Ag(001) are studied and the impact of this shift on the catalytic properties of adsorbed metal species is discussed.

  20. Single-Molecule Studies of Integrins by AFM-Based Force Spectroscopy on Living Cells

    NASA Astrophysics Data System (ADS)

    Eibl, Robert H.

    The characterization of cell adhesion between two living cells at the single-molecule level, i.e., between one adhesion receptor and its counter-receptor, appears to be an experimental challenge. Atomic force microscopy (AFM) can be used in its force spectroscopy mode to determine unbinding forces of a single pair of adhesion receptors, even with a living cell as a probe. This chapter provides an overview of AFM force measurements of the integrin family of cell adhesion receptors and their ligands. A focus is given to major integrins expressed on leukocytes, such as lymphocyte function-associated antigen 1 (LFA-1) and very late antigen 4 (VLA-4). These receptors are crucial for leukocyte trafficking in health and disease. LFA-1 and VLA-1 can be activated within the bloodstream from a low-affinity to a high-affinity receptor by chemokines in order to adhere strongly to the vessel wall before the receptor-bearing leukocytes extravasate. The experimental considerations needed to provide near-physiological conditions for a living cell and to be able to measure adequate forces at the single-molecule level are discussed in detail. AFM technology has been developed into a modern and extremely sensitive tool in biomedical research. It appears now that AFM force spectroscopy could enter, within a few years, medical applications in diagnosis and therapy of cancer and autoimmune diseases.

  1. Investigation of growth rate dispersion in lactose crystallisation by AFM

    NASA Astrophysics Data System (ADS)

    Dincer, T. D.; Ogden, M. I.; Parkinson, G. M.

    2014-09-01

    α-Lactose monohydrate crystals have been reported to exhibit growth rate dispersion (GRD). Variation in surface dislocations has been suggested as the cause of GRD, but this has not been further investigated to date. In this study, growth rate dispersion and the change in morphology were investigated in situ and via bottle roller experiments. The surfaces of the (0 1 0) faces of crystals were examined with Atomic Force Microscopy. Smaller, slow growing crystals tend to have smaller (0 1 0) faces with narrow bases and displayed a single double spiral in the centre of the crystal with 2 nm high steps. Additional double spirals in other crystals resulted in faster growth rates. Large, fast growing crystals were observed to have larger (0 1 0) faces with fast growth in both the a and b directions (giving a broader crystal base) with macro steps parallel to the (c direction). The number and location of spirals or existence of macro steps appears to influence the crystal morphology, growth rates and growth rate dispersion in lactose crystals.

  2. Influence of smectite suspension structure on sheet orientation in dry sediments: XRD and AFM applications.

    PubMed

    Zbik, Marek S; Frost, Ray L

    2010-06-15

    The structure-building phenomena within clay aggregates are governed by forces acting between clay particles. Measurements of such forces are important to understand in order to manipulate the aggregate structure for applications such as dewatering of mineral processing tailings. A parallel particle orientation is required when conducting XRD investigation on the oriented samples and conduct force measurements acting between basal planes of clay mineral platelets using atomic force microscopy (AFM). To investigate how smectite clay platelets were oriented on silicon wafer substrate when dried from suspension range of methods like SEM, XRD and AFM were employed. From these investigations, we conclude that high clay concentrations and larger particle diameters (up to 5 microm) in suspension result in random orientation of platelets in the substrate. The best possible laminar orientation in the clay dry film, represented in the XRD 001/020 intensity ratio of 47 was obtained by drying thin layers from 0.02 wt.% clay suspensions of the natural pH. Conducted AFM investigations show that smectite studied in water based electrolytes show very long-range repulsive forces lower in strength than electrostatic forces from double-layer repulsion. It was suggested that these forces may have structural nature. Smectite surface layers rehydrate in water environment forms surface gel with spongy and cellular texture which cushion approaching AFM probe. This structural effect can be measured in distances larger than 1000 nm from substrate surface and when probe penetrate this gel layer, structural linkages are forming between substrate and clay covered probe. These linkages prevent subsequently smooth detachments of AFM probe on way back when retrieval. This effect of tearing new formed structure apart involves larger adhesion-like forces measured in retrieval. It is also suggested that these effect may be enhanced by the nano-clay particles interaction.

  3. Versatile method for AFM-tip functionalization with biomolecules: fishing a ligand by means of an in situ click reaction.

    PubMed

    Kumar, Rakesh; Ramakrishna, Shivaprakash N; Naik, Vikrant V; Chu, Zonglin; Drew, Michael E; Spencer, Nicholas D; Yamakoshi, Yoko

    2015-04-21

    A facile and universal method for the functionalization of an AFM tip has been developed for chemical force spectroscopy (CFS) studies of intermolecular interactions of biomolecules. A click reaction between tripod-acetylene and an azide-linker-ligand molecule was successfully carried out on the AFM tip surface and used for the CFS study of ligand-receptor interactions.

  4. High throughput nanofabrication of silicon nanowire and carbon nanotube tips on AFM probes by stencil-deposited catalysts.

    PubMed

    Engstrom, Daniel S; Savu, Veronica; Zhu, Xueni; Bu, Ian Y Y; Milne, William I; Brugger, Juergen; Boggild, Peter

    2011-04-13

    A new and versatile technique for the wafer scale nanofabrication of silicon nanowire (SiNW) and multiwalled carbon nanotube (MWNT) tips on atomic force microscope (AFM) probes is presented. Catalyst material for the SiNW and MWNT growth was deposited on prefabricated AFM probes using aligned wafer scale nanostencil lithography. Individual vertical SiNWs were grown epitaxially by a catalytic vapor-liquid-solid (VLS) process and MWNTs were grown by a plasma-enhanced chemical vapor (PECVD) process on the AFM probes. The AFM probes were tested for imaging micrometers-deep trenches, where they demonstrated a significantly better performance than commercial high aspect ratio tips. Our method demonstrates a reliable and cost-efficient route toward wafer scale manufacturing of SiNW and MWNT AFM probes. PMID:21446752

  5. Characterization of single 1.8-nm Au nanoparticle attachments on AFM tips for single sub-4-nm object pickup

    NASA Astrophysics Data System (ADS)

    Cheng, Hui-Wen; Chang, Yuan-Chih; Tang, Song-Nien; Yuan, Chi-Tsu; Tang, Jau; Tseng, Fan-Gang

    2013-11-01

    This paper presents a novel method for the attachment of a 1.8-nm Au nanoparticle (Au-NP) to the tip of an atomic force microscopy (AFM) probe through the application of a current-limited bias voltage. The resulting probe is capable of picking up individual objects at the sub-4-nm scale. We also discuss the mechanisms involved in the attachment of the Au-NP to the very apex of an AFM probe tip. The Au-NP-modified AFM tips were used to pick up individual 4-nm quantum dots (QDs) using a chemically functionalized method. Single QD blinking was reduced considerably on the Au-NP-modified AFM tip. The resulting AFM tips present an excellent platform for the manipulation of single protein molecules in the study of single protein-protein interactions.

  6. New AFM Techniques for Investigating Molecular Growth Mechanisms of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Konnert, John H.; Pusey, Marc L.

    1998-01-01

    Atomic Force Microscopy (AFM) has emerged as a powerful technique for investigating protein crystal growth. Earlier AFM studies were among the first to demonstrate that these crystals grew by dislocation and 2D nucleation growth mechanisms [1]. These investigations were restricted to the micron range where only surface features, such as dislocation hillocks and 2D islands are visible. Most AFM instruments can scan at higher resolutions and have the potential to resolve individual protein molecules at nanometer ranges. Such scans are essential for determining the molecular packing arrangements on crystal faces and for probing the growth process at the molecular level. However, at this resolution the AFM tip influences the image produced, with the resulting image being a convolution of the tip shape and the surface morphology [2]. In most studies this problem is resolved by deconvoluting the image to obtain the true surface morphology. Although deconvolution routines work reasonably well for simple one- dimensional shapes, for complex surfaces this approach does not produce accurate results. In this study we devised a new approach which takes advantage of the precise molecular order of crystal surfaces, combined with the knowledge of individual molecular shapes from the crystallographic data of the protein and the AFM tip shape. This information is used to construct expected theoretical AFM images by convoluting the tip shape with the constructed crystal surface shape for a given surface packing arrangement. By comparing the images from actual AFM scans with the constructed ones for different possible surface packing arrangements, the correct packing arrangement can be conclusively determined. This approach was used in this study to determine the correct one from two possible packing arrangements on (I 10) faces of tetragonal lysozyme crystals. Another novel AFM technique was also devised to measure the dimension of individual growth units of the crystal faces

  7. Load displacement and high speed nanoindentation data set at different state of charge (SoC) for spinel Li x Mn2O4 cathodes.

    PubMed

    Mughal, Muhammad Zeeshan; Moscatelli, Riccardo; Sebastiani, Marco

    2016-09-01

    Novel high speed nanoindentation data is reported for 0% and 100% state of charge (SoC) for the spinal Li x Mn2O4 material. The article also includes the load/displacement data for different SoC highlighting the displacement bursts corresponding to the pillar splitting for fracture toughness evaluation. For more details, please see the article; Mughal et al. (2016) [1]. PMID:27331088

  8. Load displacement and high speed nanoindentation data set at different state of charge (SoC) for spinel Li x Mn2O4 cathodes.

    PubMed

    Mughal, Muhammad Zeeshan; Moscatelli, Riccardo; Sebastiani, Marco

    2016-09-01

    Novel high speed nanoindentation data is reported for 0% and 100% state of charge (SoC) for the spinal Li x Mn2O4 material. The article also includes the load/displacement data for different SoC highlighting the displacement bursts corresponding to the pillar splitting for fracture toughness evaluation. For more details, please see the article; Mughal et al. (2016) [1].

  9. On capturing the grain-scale elastic and plastic anisotropy of alpha-Ti with spherical nanoindentation and electron back-scattered diffraction

    DOE PAGES

    Weaver, Jordan S.; Priddy, Matthew W.; McDowell, David L.; Kalidindi, Surya R.

    2016-07-10

    Here, spherical nanoindentation combined with electron back-scattered diffraction has been employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti of two different compositions (in two different titanium alloys). Data analyses protocols needed to reliably extract the desired properties of interest are extended and demonstrated in this paper. Specifically, the grain-scale mechanical response is extracted in the form of indentation stress-strain curves for commercially pure (CP-Ti) alpha-Ti and alloyed (Ti-64) titanium from measurements on polycrystalline samples. The results are compared with responses of single crystals and nanoindentation tests (hardness and modulus) from the literature, and the measuredmore » indentation moduli are validated using crystal-elastic finite element simulations. The results obtained in this study show that (i) it is possible to characterize reliably the elastic and plastic anisotropy of alpha-Ti (hcp) of varying alloying contents with spherical nanoindentation stress-strain curves, (ii) the indentation modulus of alpha-Ti-64 is 5–10% less than CP-Ti, and (iii) the indentation yield strength of alpha-Ti-64 is 50–80% higher than CP-Ti.« less

  10. Effective properties of a fly ash geopolymer: Synergistic application of X-ray synchrotron tomography, nanoindentation, and homogenization models

    DOE PAGES

    Das, Sumanta; Yang, Pu; Singh, Sudhanshu S.; Mertens, James C. E.; Xiao, Xianghui; Chawla, Nikhilesh; Neithalath, Narayanan

    2015-09-02

    Microstructural and micromechanical investigation of a fly ash-based geopolymer using: (i) synchrotron x-ray tomography (XRT) to determine the volume fraction and tortuosity of pores that are influential in fluid transport, (ii) mercury intrusion porosimetry (MIP) to capture the volume fraction of smaller pores, (iii) scanning electron microscopy (SEM) combined with multi-label thresholding to identify and characterize the solid phases in the microstructure, and (iv) nanoindentation to determine the component phase elastic properties using statistical deconvolution, is reported in this paper. The phase volume fractions and elastic properties are used in multi-step mean field homogenization (Mori- Tanaka and double inclusion) modelsmore » to determine the homogenized macroscale elastic modulus of the composite. The homogenized elastic moduli are in good agreement with the flexural elastic modulus determined on macroscale paste beams. As a result, the combined use of microstructural and micromechanical characterization tools at multiple scales provides valuable information towards the material design of fly ash geopolymers.« less

  11. Manifestation of intermediate phase in mechanical properties: Nano-indentation studies on Ge-Te-Si bulk chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Das, Chandasree; Kiran, M. S. R. N.; Ramamurty, U.; Asokan, S.

    2012-12-01

    Nano-indentation studies have been undertaken on bulk Ge15Te85-xSix glasses (0≤x≤9), to estimate hardness, H and elastic modulus, E. It is found that E and H increase initially with the increase in the atomic percent of Si. Further, a plateau is seen in the composition dependence of E and H in the composition range 2≤x≤6. It is also seen that the addition of up to 2 at% Si increases the density ρ of the glass considerably; however, further additions of Si lead to a near linear reduction in ρ, in the range 2≤x≤6. Beyond x=6, ρ increases again with Si content. The variation of molar volume Vm brings out a more fascinating picture. A plateau is seen in the intermediate phase suggesting that the molecular structure of the glasses is adapting to keep the count of constraints fixed in this particular phase. The observed variations in mechanical properties are associated with the Boolchand's intermediate phase in the present glassy system, in the composition range 2≤x≤6, suggested earlier from calorimetric and electrical switching studies. The present results reveal rather directly the existence of the intermediate phase in elastic and plastic properties of chalcogenide glasses.

  12. Nanoindentation measurements of the mechanical properties of zirconium matrix and hydrides in unirradiated pre-hydrided nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Rico, A.; Martin-Rengel, M. A.; Ruiz-Hervias, J.; Rodriguez, J.; Gomez-Sanchez, F. J.

    2014-09-01

    It is well known that the mechanical properties of the nuclear fuel cladding may be affected by the presence of hydrides. The average mechanical properties of hydrided cladding have been extensively investigated from a macroscopic point of view. In addition, the mechanical and fracture properties of bulk hydride samples fabricated from zirconium plates have also been reported. In this paper, Young's modulus, hardness and yield stress are measured for each phase, namely zirconium hydrides and matrix, of pre-hydrided nuclear fuel cladding. To this end, nanoindentation tests were performed on ZIRLO samples in as-received state, on a hydride blister and in samples with 150 and 1200 ppm of hydrogen homogeneously distributed along the hoop direction of the cladding. The results show that the measured mechanical properties of the zirconium hydrides and ZIRLO matrix (Young's modulus, hardness and yield stress) are rather similar. From the experimental data, the hydride volume fraction in the cladding samples with 150 and 1200 ppm was estimated and the average mechanical properties were calculated by means of the rule of mixtures. These values were compared with those obtained from ring compression tests. Good agreement between the results obtained by both methods was found.

  13. Effect of heat treatment on deformation and mechanical properties of 8 mol% yttria-stabilized zirconia by Berkovich nanoindentation

    NASA Astrophysics Data System (ADS)

    Mao, W. G.; Luo, J. M.; Dai, C. Y.; Shen, Y. G.

    2015-05-01

    The effect of thermal treatment on the elasto-plastic transition and mechanical properties of air plasma-sprayed 8 mol% Y2O3-stabilized ZrO2 (8YSZ) thermal barrier coatings was studied by nanoindentation test at ultra-low loads with a Berkovich indenter. The area contact function of the indenter was calibrated repeatedly under nano-scales, and the indenter tip radius was estimated under different indentation depths, respectively. Owing to the heterogeneous and porous microstructure, the scatter of all collected experimental data was analyzed by Weibull statistic method. It is interesting to observe that the hardness exhibits an apparent reverse indentation size effect under very small depths. The Young's modulus of 8YSZ varies with ranging from 213 to 246 GPa due to the sintering effect. True hardness of 8YSZ increases from as-received 72.9 GPa to a top value 79.7 GPa under 100 thermal cycles, and then slightly decreases from this value to 75.5 GPa under 175 thermal cycles. The pure elastic and elasto-plastic indentation curves were obtained by adjusting the indentation load magnitude. The elasto-plastic transition and resolved shear stress fields were discussed carefully from the use of energetic models and Hertzian contact theory.

  14. AFM combines functional and morphological analysis of peripheral myelinated and demyelinated nerve fibers.

    PubMed

    Heredia, Alejandro; Bui, Chin Chu; Suter, Ueli; Young, Peter; Schäffer, Tilman E

    2007-10-01

    Demyelination of the myelinated peripheral or central axon is a common pathophysiological step in the clinical manifestation of several human diseases of the peripheral and the central nervous system such as the majority of Charcot-Marie-Tooth syndromes and multiple sclerosis, respectively. The structural degradation of the axon insulating myelin sheath has profound consequences for ionic conduction and nerve function in general, but also affects the micromechanical properties of the nerve fiber. We have for the first time investigated mechanical properties of rehydrated, isolated peripheral nerve fibers from mouse using atomic force microscopy (AFM). We have generated quantitative maps of elastic modulus along myelinated and demyelinated axons, together with quantitative maps of axon topography. This study shows that AFM can combine functional and morphological analysis of neurological tissue at the level of single nerve fibers.

  15. SEM and AFM images of pyrite surfaces after bioleaching by the indigenous Thiobacillus thiooxidans.

    PubMed

    Liu, H-L; Chen, B-Y; Lan, Y-W; Cheng, Y-C

    2003-09-01

    The bioleaching mechanism of pyrite by the indigenous Thiobacillus thiooxidans was examined with the aid of scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the pyrite surface. The presence of pyrite eliminated the lag phase during growth of this microorganism. This was due to the stimulatory effect on cell growth of the slight amount of Cu2+ that had leached from the pyrite. Zn2+ was found to be much more readily solubilized than Cu2+. The efficiency of bioleaching was four times higher than that of chemical leaching. SEM images provided evidence of direct cell attachment onto the pyrite surface, thereby enhancing the bioleaching rate. Furthermore, extracellular polymeric substances (EPSs) were found on the pyrite surface after 4 days of oxidation. AFM images showed that the pyrite surface area positively correlated with the oxidation rate. A combination of direct and indirect mechanism is probably responsible for the oxidation of pyrite by T. thiooxidans.

  16. Accurate and precise calibration of AFM cantilever spring constants using laser Doppler vibrometry.

    PubMed

    Gates, Richard S; Pratt, Jon R

    2012-09-21

    Accurate cantilever spring constants are important in atomic force microscopy both in control of sensitive imaging and to provide correct nanomechanical property measurements. Conventional atomic force microscope (AFM) spring constant calibration techniques are usually performed in an AFM. They rely on significant handling and often require touching the cantilever probe tip to a surface to calibrate the optical lever sensitivity of the configuration. This can damage the tip. The thermal calibration technique developed for laser Doppler vibrometry (LDV) can be used to calibrate cantilevers without handling or touching the tip to a surface. Both flexural and torsional spring constants can be measured. Using both Euler-Bernoulli modeling and an SI traceable electrostatic force balance technique as a comparison we demonstrate that the LDV thermal technique is capable of providing rapid calibrations with a combination of ease, accuracy and precision beyond anything previously available.

  17. Surface electrical properties of stainless steel fibres: An AFM-based study

    NASA Astrophysics Data System (ADS)

    Yin, Jun; D'Haese, Cécile; Nysten, Bernard

    2015-03-01

    Atomic force microscopy (AFM) electrical modes were used to study the surface electrical properties of stainless steel fibres. The surface electrical conductivity was studied by current sensing AFM and I-V spectroscopy. Kelvin probe force microscopy was used to measure the surface contact potential. The oxide film, known as passivation layer, covering the fibre surface gives rise to the observation of an apparently semiconducting behaviour. The passivation layer generally exhibits a p-type semiconducting behaviour, which is attributed to the predominant formation of chromium oxide on the surface of the stainless steel fibres. At the nanoscale, different behaviours are observed from points to points, which may be attributed to local variations of the chemical composition and/or thickness of the passivation layer. I-V curves are well fitted with an electron tunnelling model, indicating that electron tunnelling may be the predominant mechanism for electron transport.

  18. Cell mechanics as a marker for diseases: Biomedical applications of AFM

    NASA Astrophysics Data System (ADS)

    Rianna, Carmela; Radmacher, Manfred

    2016-08-01

    Many diseases are related to changes in cell mechanics. Atomic Force Microscopy (AFM) is one of the most suitable techniques allowing the investigation of both topography and mechanical properties of adherent cells with high spatial resolution under physiological conditions. Over the years the use of this technique in medical and clinical applications has largely increased, resulting in the notion of cell mechanics as a biomarker to discriminate between different physiological and pathological states of cells. Cell mechanics has proven to be a biophysical fingerprint able discerning between cell phenotypes, unraveling processes in aging or diseases, or even detecting and diagnosing cellular pathologies. We will review in this report some of the works on cell mechanics investigated by AFM with clinical and medical relevance in order to clarify the state of research in this field and to highlight the role of cell mechanics in the study of pathologies, focusing on cancer, blood and cardiovascular diseases.

  19. Pattern formation and control in polymeric systems: From Minkowski measures to in situ AFM imaging

    NASA Astrophysics Data System (ADS)

    Jacobs, Karin

    2014-03-01

    Thin liquid polymer films are not only of great technical importance, they also exhibit a variety of dynamical instabilities. Some of them may be desired, some rather not. To analyze and finally control pattern formation, modern thin film theories are as vital as techniques to characterize the morphologies and structures in and on the films. Examples for the latter are atomic force microscopy (AFM) as well as scattering techniques. The talk will introduce into the practical applications of Minkowski measures to characterize patterns and explain what thin film properties (e.g. capillary number, solid/liquid boundary condition, glass transition temperature, chain mobility) can further be extracted including new technical possibilities by AFM and scattering techniques.

  20. AFM imaging reveals the tetrameric structure of the TRPM8 channel

    SciTech Connect

    Stewart, Andrew P.; Egressy, Kinga; Lim, Annabel; Edwardson, J. Michael

    2010-04-02

    Several members of the transient receptor potential (TRP) channel superfamily have been shown to assemble as tetramers. Here we have determined the subunit stoichiometry of the transient receptor potential M8 (TRPM8) channel using atomic force microscopy (AFM). TRPM8 channels were isolated from transfected cells, and complexes were formed between the channels and antibodies against a V5 epitope tag present on each subunit. The complexes were then subjected to AFM imaging. A frequency distribution of the molecular volumes of antibody decorated channels had a peak at 1305 nm{sup 3}, close to the expected size of a TRPM8 tetramer. The frequency distribution of angles between pairs of bound antibodies had two peaks, at 93{sup o} and 172{sup o}, confirming that the channel assembles as a tetramer. We suggest that this assembly pattern is common to all members of the TRP channel superfamily.

  1. BOREAS AFM-5 Level-2 Upper Air Network Standard Pressure Level Data

    NASA Technical Reports Server (NTRS)

    Barr, Alan; Hrynkiw, Charmaine; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-5 team collected and processed data from the numerous radiosonde flights during the project. The goals of the AFM-05 team were to provide large-scale definition of the atmosphere by supplementing the existing AES aerological network, both temporally and spatially. This data set includes basic upper-air parameters interpolated at 0.5 kiloPascal increments of atmospheric pressure from data collected from the network of upper-air stations during the 1993, 1994, and 1996 field campaigns over the entire study region. The data are contained in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  2. Mode coupling in a hanging-fiber AFM used as a rheological probe

    NASA Astrophysics Data System (ADS)

    Devailly, C.; Laurent, J.; Steinberger, A.; Bellon, L.; Ciliberto, S.

    2014-06-01

    We analyze the advantages and drawbacks of a method which measures the viscosity of liquids at microscales, using a thin glass fiber fixed on the tip of a cantilever of an ultra-low-noise Atomic Force Microscope (AFM). When the fiber is dipped into a liquid, the dissipation of the cantilever-fiber system, which is linked to the liquid viscosity, can be computed from the power spectral density of the thermal fluctuations of the cantilever deflection. The high sensitivity of the AFM allows us to show the existence and to develop a model of the coupling between the dynamics of the fiber and that of the cantilever. This model, which accurately fits the experimental data, gives also more insights into the dynamics of coupled microdevices in a viscous environment.

  3. AFM characterization of nanobubble formation and slip condition in oxygenated and electrokinetically altered fluids.

    PubMed

    Bhushan, Bharat; Pan, Yunlu; Daniels, Stephanie

    2013-02-15

    Nanobubbles are gas-filled features that spontaneously form at the interface of hydrophobic surfaces and aqueous solutions. In this study, an atomic force microscope (AFM) was used to characterize the morphology of nanobubbles formed on hydrophobic polystyrene (PS) and octadecyltrichlorosilane (OTS) films immersed in DI water, saline, saline with oxygen and an electrokinetically altered saline solution produced with Taylor-Couette-Poiseuille flow under elevated oxygen pressure. AFM force spectroscopy was used to evaluate hydrodynamic and electrostatic forces and boundary slip condition in various fluids. The effect of solution, electric field and surface charge on shape, size and density of nanobubbles as well as slip length was quantified and the results and underlying mechanisms are presented in this paper.

  4. Characterization of the polycaprolactone melt crystallization: complementary optical microscopy, DSC, and AFM studies.

    PubMed

    Speranza, V; Sorrentino, A; De Santis, F; Pantani, R

    2014-01-01

    The first stages of the crystallization of polycaprolactone (PCL) were studied using several techniques. The crystallization exotherms measured by differential scanning calorimetry (DSC) were analyzed and compared with results obtained by polarized optical microscopy (POM), rheology, and atomic force microscope (AFM). The experimental results suggest a strong influence of the observation scale. In particular, the AFM, even if limited on time scale, appears to be the most sensitive technique to detect the first stages of crystallization. On the contrary, at least in the case analysed in this work, rheology appears to be the least sensitive technique. DSC and POM provide closer results. This suggests that the definition of induction time in the polymer crystallization is a vague concept that, in any case, requires the definition of the technique used for its characterization.

  5. Molecular Dynamic Simulations of Interaction of an AFM Probe with the Surface of an SCN Sample

    NASA Technical Reports Server (NTRS)

    Bune, Adris; Kaukler, William; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Molecular dynamic (MD) simulations is conducted in order to estimate forces of probe-substrate interaction in the Atomic Force Microscope (AFM). First a review of available molecular dynamic techniques is given. Implementation of MD simulation is based on an object-oriented code developed at the University of Delft. Modeling of the sample material - succinonitrile (SCN) - is based on the Lennard-Jones potentials. For the polystyrene probe an atomic interaction potential is used. Due to object-oriented structure of the code modification of an atomic interaction potential is straight forward. Calculation of melting temperature is used for validation of the code and of the interaction potentials. Various fitting parameters of the probe-substrate interaction potentials are considered, as potentials fitted to certain properties and temperature ranges may not be reliable for the others. This research provides theoretical foundation for an interpretation of actual measurements of an interaction forces using AFM.

  6. Force-controlled manipulation of single cells: from AFM to FluidFM.

    PubMed

    Guillaume-Gentil, Orane; Potthoff, Eva; Ossola, Dario; Franz, Clemens M; Zambelli, Tomaso; Vorholt, Julia A

    2014-07-01

    The ability to perturb individual cells and to obtain information at the single-cell level is of central importance for addressing numerous biological questions. Atomic force microscopy (AFM) offers great potential for this prospering field. Traditionally used as an imaging tool, more recent developments have extended the variety of cell-manipulation protocols. Fluidic force microscopy (FluidFM) combines AFM with microfluidics via microchanneled cantilevers with nano-sized apertures. The crucial element of the technology is the connection of the hollow cantilevers to a pressure controller, allowing their operation in liquid as force-controlled nanopipettes under optical control. Proof-of-concept studies demonstrated a broad spectrum of single-cell applications including isolation, deposition, adhesion and injection in a range of biological systems. PMID:24856959

  7. High precision attachment of silver nanoparticles on AFM tips by dielectrophoresis.

    PubMed

    Leiterer, Christian; Wünsche, Erik; Singh, Prabha; Albert, Jens; Köhler, Johann M; Deckert, Volker; Fritzsche, Wolfgang

    2016-05-01

    AFM tips are modified with silver nanoparticles using an AC electrical field. The used technique works with sub-micron precision and also does not require chemical modification of the tip. Based on the electrical parameters applied in the process, particle density and particle position on the apex of the tip can be adjusted. The feasibility of the method is proven by subsequent tip-enhanced Raman spectroscopy (TERS) measurements using the fabricated tips as a measurement probe. Since this modification process itself does not require any lithographic processing, the technique can be easily adapted to modify AFM tips with a variety of nanostructures with pre-defined properties, while being parallelizable for a potential commercial application.

  8. Carbon nanotube/carbon nanotube composite AFM probes prepared using ion flux molding

    NASA Astrophysics Data System (ADS)

    Chesmore, Grace; Roque, Carrollyn; Barber, Richard

    The performance of carbon nanotube-carbon nanotube composite (CNT/CNT composite) atomic force microscopy (AFM) probes is compared to that of conventional Si probes in AFM tapping mode. The ion flux molding (IFM) process, aiming an ion beam at the CNT probe, aligns the tip to a desired angle. The result is a relatively rigid tip that is oriented to offset the cantilever angle. Scans using these probes reveal an improvement in image accuracy over conventional tips, while allowing higher aspect ratio imaging of 3D surface features. Furthermore, the lifetimes of CNT-CNT composite tips are observed to be longer than both conventional tips and those claimed for other CNT technologies. Novel applications include the imaging of embiid silk. Supported by the Clare Boothe Luce Research Scholars Award and Carbon Design Innovations.

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

    PubMed

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

    2011-10-01

    A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (<100 nm) oscillations are readily measured with AFM. Resonance oscillation frequencies were measured for drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

  10. Characterization and Optimization of Quartz Tuning Fork-Based Force Sensors for Combined STM/AFM

    NASA Astrophysics Data System (ADS)

    Castellanos-Gomez, Andres; Agraït, Nicolás; Rubio-Bollinger, Gabino

    This chapter will be divided in two main parts. In the first one, we will show a detailed analysis of the dynamics of quartz tuning fork resonators which are being increasingly used in scanning probe microscopy as force sensors. We will also show that a coupled harmonic oscillators model, which includes a finite coupling between the prongs, is in remarkable agreement with the observed motion of the tuning forks. Relevant parameters for the tuning fork performance such as the effective spring constant can be obtained from our analysis. In the second one, we will present an implementation of a quartz tuning fork supplemented with optimized tips based on carbon fibers. The remarkable electrical and mechanical properties of carbon fiber make these tips more suitable for combined and/or simultaneous STM and AFM than conventional metallic tips. The fabrication and the characterization of these carbon fiber tips as well as their performance in STM/AFM will be detailed.

  11. In vitro study of AFB1 and AFM1 effects on human lymphoblastoid Jurkat T-cell model.

    PubMed

    Luongo, D; Russo, R; Balestrieri, A; Marzocco, S; Bergamo, P; Severino, L

    2014-10-01

    Aflatoxin B(1) (AFB(1)) is a mycotoxin produced by Aspergillus spp. that can occur as a natural contaminant in foods and feeds of vegetable origin. Post-ingestion, AFB(1) can be metabolized in the liver of mammals into hydroxylated aflatoxin M(1) (AFM(1)) that is excreted with milk. Although several studies have been carried out to evaluate effects of AFB(1) on the immune system, studies regarding AFM(1) are moreover lacking. The aim of the current study was to investigate effects of AFB(1) and AFM(1) on immune function using a lymphoblastoid Jurkat T-cell line as an experimental model. Both AFB(1) and AFM(1) produced significant decreases in Jurkat cell proliferation, whereas only minor effects were noted on interleukin (IL)-2 and interferon (IFN)-γ cytokines mRNA expression in stimulated cells that had been pre-incubated with AFB(1) and AFM(1). Particularly, AFB(1), but not AFM(1), at the highest concentration (50 µM) induced a marked increase in IL-8 mRNA expression. The results of the current study suggested the existence of a concentration threshold for AFB(1) and AFM(1) needed to exert biological activity on cell viability and innate immunity.

  12. Aflatoxin M1 Concentration in Various Dairy Products: Evidence for Biologically Reduced Amount of AFM1 in Yoghurt

    PubMed Central

    RAHIMIRAD, Amir; MAALEKINEJAD, Hassan; OSTADI, Araz; YEGANEH, Samal; FAHIMI, Samira

    2014-01-01

    Abstract Background Aflatoxin M1 (AFM1), a carcinogenic substance is found in milk and dairy products. The effect of season and type of dairy products on AFMi level in northern Iran was investigated in this study. Methods Three hundred samples (each season 75 samples) including raw and pasteurized milk, yoghurt, cheese, and cream samples were collected from three distinct milk producing farms. The samples were subjected to chemical and solid phase extractions and were analyzed by using HPLC technique. Recovery percentages, limit of detection and limit of quantification values were determined. Results Seventy percent and 98% were the minimum and maximum recoveries for cheese and raw milk, respectively and 0.021 and 0.063 ppb were the limit of detection and limit of quantification values for AFM1. We found that in autumn and winter the highest level (0.121 ppb) of AFM1 in cheese and cream samples and failed to detect any AFM1 in spring samples. Interestingly, our data showed that the yoghurt samples had the lowest level of AFM1 in all seasons. Conclusion There are significant differences between the AFM1 levels in dairy products in various seasons and also various types of products, suggesting spring and summer yoghurt samples as the safest products from AFM1 level point of view. PMID:25927044

  13. Liquid solution delivery through the pulled nanopipette combined with QTF-AFM system

    NASA Astrophysics Data System (ADS)

    An, Sangmin; Stambaugh, Corey; Kim, Gunn; Lee, Manhee; Kim, Yonghee; Lee, Kunyoung; Jhe, Wonho

    2012-02-01

    Nanopipette is a versatile fluidic tool for biochemical analysis, controlled liquid delivery in bio-nanotechnology. However, most of the researches have been performed in solution based system, thus it is challenge to study nanofluidic properties of the liquid solution delivery through the nanopipette in ambient conditions. In this work, we demonstrated the liquid ejection, dispersion, and subsequent deposition of the nanoparticles via a 30 nm aperture pipette based on the quartz tuning fork -- atomic force microscope (QTF-AFM) combined nanopipette system.

  14. Morphological analysis of stainless steel scale like surface morphology using STM and AFM

    SciTech Connect

    Vignal, V.; Olive, J.M.; Desjardins, D.; Roux, J.C.; Genton, V.

    1997-12-19

    A combined atomic force microscopy (AFM) and scanning tunneling microscopy (STM) investigation of stainless steel like surface morphology formed either in electropolishing bath or in HNO{sub 3} medium is reported. A new numerical technique using the Nanoscope III software is proposed. The dimension, slope and orientation of scales can be easily determined. Moreover, grain boundaries structure and probable oxides present in the upper part of the film can be deduced.

  15. The NTA-His6 bond is strong enough for AFM single-molecular recognition studies.

    PubMed

    Verbelen, Claire; Gruber, Hermann J; Dufrêne, Yves F

    2007-01-01

    There is a need in current atomic force microscopy (AFM) molecular recognition studies for generic methods for the stable, functional attachment of proteins on tips and solid supports. In the last few years, the site-directed nitrilotriacetic acid (NTA)-polyhistidine (Hisn) system has been increasingly used towards this goal. Yet, a crucial question in this context is whether the NTA-Hisn bond is sufficiently strong for ensuring stable protein immobilization during force spectroscopy measurements. Here, we measured the forces between AFM tips modified with NTA-terminated alkanethiols and solid supports functionalized with His6-Gly-Cys peptides in the presence of Ni2+. The force histogram obtained at a loading rate of 6600 pN s(-1) showed three maxima at rupture forces of 153 +/- 57 pN, 316 +/- 50 pN and 468 +/- 44 pN, that we attribute primarily to monovalent and multivalent interactions between a single His6 moiety and one, two and three NTA groups, respectively. The measured forces are well above the 50-100 pN unbinding forces typically observed by AFM for receptor-ligand pairs. The plot of adhesion force versus log (loading rate) revealed a linear regime, from which we deduced a kinetic off-rate constant of dissociation, k(off) approximately 0.07 s(-1). This value is in the range of that estimated for the multivalent interaction involving two NTA, using fluorescence measurements, and may account for an increased binding stability of the NTA-His6 bond. We conclude that the NTA-His6 system is a powerful, well-suited platform for the stable, oriented immobilization of proteins in AFM single-molecule studies. PMID:17712775

  16. Crystallization of Probucol in Nanoparticles Revealed by AFM Analysis in Aqueous Solution.

    PubMed

    Egami, Kiichi; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu

    2015-08-01

    The crystallization behavior of a pharmaceutical drug in nanoparticles was directly evaluated by atomic force microscopy (AFM) force curve measurements in aqueous solution. A ternary spray-dried sample (SPD) was prepared by spray drying the organic solvent containing probucol (PBC), hypromellose (HPMC), and sodium dodecyl sulfate (SDS). The amorphization of PBC in the ternary SPD was confirmed by powder X-ray diffraction (PXRD) and solid-state 13C NMR measurements. A nanosuspension containing quite small particles of 25 nm in size was successfully prepared immediately after dispersion of the ternary SPD into water. Furthermore, solution-state 1H NMR measurements revealed that a portion of HPMC coexisted with PBC as a mixed state in the freshly prepared nanosuspension particles. After storing the nanosuspension at 25 °C, a gradual increase in the size of the nanoparticles was observed, and the particle size changed to 93.9 nm after 7 days. AFM enabled the direct observation of the morphology and agglomeration behavior of the nanoparticles in water. Moreover, AFM force-distance curves were changed from (I) to (IV), depending on the storage period, as follows: (I) complete indentation within an applied force of 1 nN, (II) complete indentation with an applied force of 1-5 nN, (III) partial indentation with an applied force of 5 nN, and (IV) nearly no indentation with an applied force of 5 nN. This stiffness increase of the nanoparticles was attributed to gradual changes in the molecular state of PBC from the amorphous to the crystal state. Solid-state 13C NMR measurements of the freeze-dried samples demonstrated the presence of metastable PBC Form II crystals in the stored nanosuspension, strongly supporting the AFM results.

  17. Fracture Growth Testing of Titanium 6AL-4V in AF-M315E

    NASA Technical Reports Server (NTRS)

    Sampson, Jeffrey W.; Martinez, Jonathan; McLean, Christopher

    2015-01-01

    The Green Propellant Infusion Mission (GPIM) will demonstrate the performance of AF-M315E monopropellant in orbit. Flight certification requires a safe-life analysis of the titanium alloy fuel tank to ensure inherent flaws will not cause failure during the design life. Material property inputs for this analysis require testing to determine the stress intensity factor for environmentally-assisted cracking (K (sub EAC)) of Ti 6Al-4V in combination with the AF-M315E monopropellant. Testing of single-edge notched specimens SE(B) representing the bulk tank membrane and weld material were performed in accordance with ASTM E1681. Specimens with fatigue pre-cracks were loaded into test fixtures so that the crack tips were exposed to the monopropellant at 50 degrees Centigrade for a duration of 1,000 hours. Specimens that did not fail during exposure were opened to inspect the crack surfaces for evidence of crack growth. The threshold stress intensity value, KEAC, is the highest applied stress intensity that produced neither a failure of the specimen during the exposure nor showed evidence of crack growth. The threshold stress intensity factor of the Ti 6Al-4V forged tank material when exposed to AF-M315E monopropellant was found to be at least 22.0 kilopounds per square inch. The stress intensity factor of the weld material was at least 31.3 kilopounds per square inch.

  18. Analysis of time-resolved interaction force mode AFM imaging using active and passive probes.

    PubMed

    Giray Oral, Hasan; Parlak, Zehra; Levent Degertekin, F

    2012-09-01

    We present an in-depth analysis of time-resolved interaction force (TRIF) mode imaging for atomic force microscopy (AFM). A nonlinear model of an active AFM probe, performing simultaneous topography and material property imaging on samples with varying elasticity and adhesion is implemented in Simulink®. The model is capable of simulating various imaging modes, probe structures, sample material properties, tip-sample interaction force models, and actuation and feedback schemes. For passive AFM cantilevers, the model is verified by comparing results from the literature. As an example of an active probe, the force sensing integrated readout and active tip (FIRAT) probe is used. Simulation results indicate that the active and damped nature of FIRAT provides a significant level of control over the force applied to the sample, minimizing sample indentation and topography error. Active tip control (ATC) preserves constant contact time during force control for stable contact while preventing the loss of material property information such as elasticity and adhesive force. Simulation results are verified by TRIF mode imaging of the samples with both soft and stiff regions. PMID:22813887

  19. Rational fabrication of a gold-coated AFM TERS tip by pulsed electrodeposition.

    PubMed

    Yang, Li-Kun; Huang, Teng-Xiang; Zeng, Zhi-Cong; Li, Mao-Hua; Wang, Xiang; Yang, Fang-Zu; Ren, Bin

    2015-11-21

    Reproducible fabrication of sharp gold- or silver-coated tips has become the bottleneck issue in tip-enhanced Raman spectroscopy, especially for atomic force microscopy (AFM)-based TERS. Herein, we developed a novel method based on pulsed electrodeposition to coat a thin gold layer over atomic force microscopy (AFM) tips to produce plasmonic TERS tips with high reproducibility. We systematically investigated the influence of the deposition potential and step time on the surface roughness and sharpness. This method allows the rational control of the radii of gold-coated TERS tips from a few to hundreds of nanometers, which allows us to systematically study the dependence of the TERS enhancement on the radius of the gold-coated AFM tip. The maximum TERS enhancement was achieved for the tip radius in the range of 60-75 nm in the gap mode. The coated gold layer has a strong adhesion with the silicon tip surface, which is highly stable in water, showing the great potential for application in the aqueous environment. PMID:26482226

  20. Extension of gravity center method for diameter calibration of polystyrene standard particles with a metrological AFM

    NASA Astrophysics Data System (ADS)

    Misumi, Ichiko; Takahata, Keiji; Sugawara, Kentaro; Gonda, Satoshi; Ehara, Kensei

    2012-06-01

    In the particle diameter calibration using metrological AFM, the distance between center points of neighboring two particles is referred to as "lateral diameter" when a single-layer close-packed structure of particles is successfully formed. The distance between an apex of a particle and a substrate is referred to as "vertical diameter." In the previous studies, lateral diameter was calculated by manually selecting and extracting a line profile from metrological AFM data and directly applying a method to calculate a pitch of one-dimensional grating. As the manual line profile extraction depends on who does it, however, there is a possibility that calculated lateral diameter is varied from person to person. We developed a technology to calibrate diameter of polystyrene latex (PSL) particles by using our metrological AFM. In this study, the gravity center method is extended to three dimensions to calculate position of and the center of gravity in each particle. Lateral diameter, which was defined as distance between gravity centers of neighboring two particles, is calibrated and uncertainty in the lateral diameter calibration is evaluated. Deformation of particles was also estimated by using Young's modulus of thin film PSL and bulk PSL.

  1. A Novel Dog-Bone Oscillating AFM Probe with Thermal Actuation and Piezoresistive Detection †

    PubMed Central

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-01-01

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments. PMID:25365463

  2. A novel dog-bone oscillating AFM probe with thermal actuation and piezoresistive detection.

    PubMed

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-01-01

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments. PMID:25365463

  3. Single-cycle-PLL detection for real-time FM-AFM applications.

    PubMed

    Schlecker, Benedikt; Dukic, Maja; Erickson, Blake; Ortmanns, Maurits; Fantner, Georg; Anders, Jens

    2014-04-01

    In this paper we present a novel architecture for phase-locked loop (PLL) based high-speed demodulation of frequency-modulated (FM) atomic force microscopy (AFM) signals. In our approach, we use single-sideband (SSB) frequency upconversion to translate the AFM signal from the position sensitive detector to a fixed intermediate frequency (IF) of 10 MHz. In this way, we fully benefit from the excellent noise performance of PLL-based FM demodulators still avoiding the intrinsic bandwidth limitation of such systems. In addition, the upconversion to a fixed IF renders the PLL demodulator independent of the cantilever's resonance frequency, allowing the system to work with a large range of cantilever frequencies. To investigate if the additional noise introduced by the SSB upconverter degrades the system noise figure we present a model of the AM-to-FM noise conversion in PLLs incorporating a phase-frequency detector. Using this model, we can predict an upper corner frequency for the demodulation bandwidth above which the converted noise from the single-sideband upconverter becomes the dominant noise source and therefore begins to deteriorate the overall system performance. The approach is validated by both electrical and AFM measurements obtained with a PCB-based prototype implementing the proposed demodulator architecture.

  4. Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample.

    PubMed

    Guo, Shifeng; Zhu, Xiaoying; Jańczewski, Dominik; Lee, Serina Siew Chen; He, Tao; Teo, Serena Lay Ming; Vancso, G Julius

    2016-09-01

    Protein charge at various pH and isoelectric point (pI) values is important in understanding protein function. However, often only trace amounts of unknown proteins are available and pI measurements cannot be obtained using conventional methods. Here, we show a method based on the atomic force microscope (AFM) to determine pI using minute quantities of proteins. The protein of interest is immobilized on AFM colloidal probes and the adhesion force of the protein is measured against a positively and a negatively charged substrate made by layer-by-layer deposition of polyelectrolytes. From the AFM force-distance curves, pI values with an estimated accuracy of ±0.25 were obtained for bovine serum albumin, myoglobin, fibrinogen and ribonuclease A over a range of 4.7-9.8. Using this method, we show that the pI of the 'footprint' of the temporary adhesive proteins secreted by the barnacle cyprid larvae of Amphibalanus amphitrite is in the range 9.6-9.7. PMID:27454881

  5. Nanoscopic imaging of mechanical properties of metal films with magnetic-force-controlled AFM

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.-I.; Yamada, H.; Matsushige, K.; Ishida, T.; Mizutani, W.; Tokumoto, H.

    1999-08-01

    We have succeeded in measuring the Young's moduli of inorganic films with a diamond tip of 160-200 nm in diameter using magnetic-force-controlled atomic force microscopy (MFC-AFM). The measurement of Young's moduli was carried out by detecting the tip amplitude on the sample with an applied force of 20 nN. This technique was applied successfully to obtain Young's moduli mapping of gold islands with 1 nm thickness and nickel films with 10 nm thickness. We obtained an effective spring constant of 3000 N m -1 on gold and 21 000 N m -1 on nickel using MFC-AFM. We could normalize the effective area of the contact radius between the tip and the sample. A value of 350 GPa was derived for the Young's modulus of the nickel film, indicative of the elasticity of native nickel oxide (NiO 2). This shows that the MFC-AFM technique measures the mechanical properties of a thin layer on top of the sample.

  6. Statistical analysis of AFM topographic images of self-assembled quantum dots

    SciTech Connect

    Sevriuk, V. A.; Brunkov, P. N. Shalnev, I. V.; Gutkin, A. A.; Klimko, G. V.; Gronin, S. V.; Sorokin, S. V.; Konnikov, S. G.

    2013-07-15

    To obtain statistical data on quantum-dot sizes, AFM topographic images of the substrate on which the dots under study are grown are analyzed. Due to the nonideality of the substrate containing height differences on the order of the size of nanoparticles at distances of 1-10 {mu}m and the insufficient resolution of closely arranged dots due to the finite curvature radius of the AFM probe, automation of the statistical analysis of their large dot array requires special techniques for processing topographic images to eliminate the loss of a particle fraction during conventional processing. As such a technique, convolution of the initial matrix of the AFM image with a specially selected matrix is used. This makes it possible to determine the position of each nanoparticle and, using the initial matrix, to measure their geometrical parameters. The results of statistical analysis by this method of self-assembled InAs quantum dots formed on the surface of an AlGaAs epitaxial layer are presented. It is shown that their concentration, average size, and half-width of height distribution depend strongly on the In flow and total amount of deposited InAs which are varied within insignificant limits.

  7. Structure and Permeability of Ion-channels by Integrated AFM and Waveguide TIRF Microscopy

    PubMed Central

    Ramachandran, Srinivasan; Arce, Fernando Teran; Patel, Nirav R.; Quist, Arjan P.; Cohen, Daniel A.; Lal, Ratnesh

    2014-01-01

    Membrane ion channels regulate key cellular functions and their activity is dependent on their 3D structure. Atomic force microscopy (AFM) images 3D structure of membrane channels placed on a solid substrate. Solid substrate prevents molecular transport through ion channels thus hindering any direct structure-function relationship analysis. Here we designed a ~70 nm nanopore to suspend a membrane, allowing fluidic access to both sides. We used these nanopores with AFM and total internal reflection fluorescence microscopy (TIRFM) for high resolution imaging and molecular transport measurement. Significantly, membranes over the nanopore were stable for repeated AFM imaging. We studied structure-activity relationship of gap junction hemichannels reconstituted in lipid bilayers. Individual hemichannels in the membrane overlying the nanopore were resolved and transport of hemichannel-permeant LY dye was visualized when the hemichannel was opened by lowering calcium in the medium. This integrated technique will allow direct structure-permeability relationship of many ion channels and receptors. PMID:24651823

  8. APOBEC3G Interacts with ssDNA by Two Modes: AFM Studies

    NASA Astrophysics Data System (ADS)

    Shlyakhtenko, Luda S.; Dutta, Samrat; Banga, Jaspreet; Li, Ming; Harris, Reuben S.; Lyubchenko, Yuri L.

    2015-10-01

    APOBEC3G (A3G) protein has antiviral activity against HIV and other pathogenic retroviruses. A3G has two domains: a catalytic C-terminal domain (CTD) that deaminates cytidine, and a N-terminal domain (NTD) that binds to ssDNA. Although abundant information exists about the biological activities of A3G protein, the interplay between sequence specific deaminase activity and A3G binding to ssDNA remains controversial. We used the topographic imaging and force spectroscopy modalities of Atomic Force Spectroscopy (AFM) to characterize the interaction of A3G protein with deaminase specific and nonspecific ssDNA substrates. AFM imaging demonstrated that A3G has elevated affinity for deaminase specific ssDNA than for nonspecific ssDNA. AFM force spectroscopy revealed two distinct binding modes by which A3G interacts with ssDNA. One mode requires sequence specificity, as demonstrated by stronger and more stable complexes with deaminase specific ssDNA than with nonspecific ssDNA. Overall these observations enforce prior studies suggesting that both domains of A3G contribute to the sequence specific binding of ssDNA.

  9. AFM and pulsed laser ablation methods for Cultural Heritage: application to archeometric analysis of stone artifacts

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Veltri, S.; Stranges, F.; Bonanno, A.; Xu, F.; Antici, P.

    2015-09-01

    In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface's roughness is evaluated from very small artifact's fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

  10. A novel dog-bone oscillating AFM probe with thermal actuation and piezoresistive detection.

    PubMed

    Xiong, Zhuang; Mairiaux, Estelle; Walter, Benjamin; Faucher, Marc; Buchaillot, Lionel; Legrand, Bernard

    2014-10-31

    In order to effectively increase the resonance frequency and the quality factor of atomic force microscope (AFM) probes, a novel oscillating probe based on a dog-bone shaped MEMS resonator was conceived, designed, fabricated and evaluated. The novel probe with 400 μm in length, 100 μm in width and 5 μm in thickness was enabled to feature MHz resonance frequencies with integrated thermal actuation and piezoresistive detection. Standard silicon micromachining was employed. Both electrical and optical measurements were carried out in air. The resonance frequency and the quality factor of the novel probe were measured to be 5.4 MHz and 4000 respectively, which are much higher than those (about several hundreds of kHz) of commonly used cantilever probes. The probe was mounted onto a commercial AFM set-up through a dedicated probe-holder and circuit board. Topographic images of patterned resist samples were obtained. It is expected that the resonance frequency and the measurement bandwidth of such probes will be further increased by a proper downscaling, thus leading to a significant increase in the scanning speed capability of AFM instruments.

  11. EEMD based pitch evaluation method for accurate grating measurement by AFM

    NASA Astrophysics Data System (ADS)

    Li, Changsheng; Yang, Shuming; Wang, Chenying; Jiang, Zhuangde

    2016-09-01

    The pitch measurement and AFM calibration precision are significantly influenced by the grating pitch evaluation method. This paper presents the ensemble empirical mode decomposition (EEMD) based pitch evaluation method to relieve the accuracy deterioration caused by high and low frequency components of scanning profile during pitch evaluation. The simulation analysis shows that the application of EEMD can improve the pitch accuracy of the FFT-FT algorithm. The pitch error is small when the iteration number of the FFT-FT algorithms was 8. The AFM measurement of the 500 nm-pitch one-dimensional grating shows that the EEMD based pitch evaluation method could improve the pitch precision, especially the grating line position precision, and greatly expand the applicability of the gravity center algorithm when particles and impression marks were distributed on the sample surface. The measurement indicates that the nonlinearity was stable, and the nonlinearity of x axis and forward scanning was much smaller than their counterpart. Finally, a detailed pitch measurement uncertainty evaluation model suitable for commercial AFMs was demonstrated and a pitch uncertainty in the sub-nanometer range was achieved. The pitch uncertainty was reduced about 10% by EEMD.

  12. Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample

    NASA Astrophysics Data System (ADS)

    Guo, Shifeng; Zhu, Xiaoying; Jańczewski, Dominik; Lee, Serina Siew Chen; He, Tao; Teo, Serena Lay Ming; Vancso, G. Julius

    2016-09-01

    Protein charge at various pH and isoelectric point (pI) values is important in understanding protein function. However, often only trace amounts of unknown proteins are available and pI measurements cannot be obtained using conventional methods. Here, we show a method based on the atomic force microscope (AFM) to determine pI using minute quantities of proteins. The protein of interest is immobilized on AFM colloidal probes and the adhesion force of the protein is measured against a positively and a negatively charged substrate made by layer-by-layer deposition of polyelectrolytes. From the AFM force-distance curves, pI values with an estimated accuracy of ±0.25 were obtained for bovine serum albumin, myoglobin, fibrinogen and ribonuclease A over a range of 4.7-9.8. Using this method, we show that the pI of the ‘footprint’ of the temporary adhesive proteins secreted by the barnacle cyprid larvae of Amphibalanus amphitrite is in the range 9.6-9.7.

  13. Nano-scale Topographical Studies on the Growth Cones of Nerve Cells using AFM

    NASA Astrophysics Data System (ADS)

    Durkaya, Goksel; Zhong, Lei; Rehder, Vincent; Dietz, Nikolaus

    2009-11-01

    Nerve cells are the fundamental units which are responsible for intercommunication within the nervous system. The neurites, fibrous cable-like extensions for information delivery, of nerve cells are tipped by highly motile sensory structures known as the growth cones which execute important functions; neural construction, decision making and navigation during development and regeneration of the nervous system. The highly dynamic subcomponents of the growth cones are important in neural activity. Atomic Force Microscopy (AFM) is the most powerful microscopy technique which is capable of imaging without conductivity constraint and in liquid media. AFM providing nano-scale topographical information on biological structures is also informative on the physical properties such as: elasticity, adhesion, and softness. This contribution focuses on AFM analysis of the growth cones of the nerve cells removed from the buccal ganglion of Helisoma trivolvis. The results of nano-scale topography and softness analysis on growth cone central domain, filopodia and overlying lamellopodium (veil) are presented. The subcomponents of the growth cones of different nerve cells are compared to each other. The results of the analysis are linked to the mechanical properties and internal molecular density distribution of the growth cones.

  14. Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample

    NASA Astrophysics Data System (ADS)

    Guo, Shifeng; Zhu, Xiaoying; Jańczewski, Dominik; Lee, Serina Siew Chen; He, Tao; Teo, Serena Lay Ming; Vancso, G. Julius

    2016-09-01

    Protein charge at various pH and isoelectric point (pI) values is important in understanding protein function. However, often only trace amounts of unknown proteins are available and pI measurements cannot be obtained using conventional methods. Here, we show a method based on the atomic force microscope (AFM) to determine pI using minute quantities of proteins. The protein of interest is immobilized on AFM colloidal probes and the adhesion force of the protein is measured against a positively and a negatively charged substrate made by layer-by-layer deposition of polyelectrolytes. From the AFM force–distance curves, pI values with an estimated accuracy of ±0.25 were obtained for bovine serum albumin, myoglobin, fibrinogen and ribonuclease A over a range of 4.7–9.8. Using this method, we show that the pI of the ‘footprint’ of the temporary adhesive proteins secreted by the barnacle cyprid larvae of Amphibalanus amphitrite is in the range 9.6–9.7.

  15. AFM-porosimetry: density and pore volume measurements of particulate materials.

    PubMed

    Sörensen, Malin H; Valle-Delgado, Juan J; Corkery, Robert W; Rutland, Mark W; Alberius, Peter C

    2008-06-01

    We introduced the novel technique of AFM-porosimetry and applied it to measure the total pore volume of porous particles with a spherical geometry. The methodology is based on using an atomic force microscope as a balance to measure masses of individual particles. Several particles within the same batch were measured, and by plotting particle mass versus particle volume, the bulk density of the sample can be extracted from the slope of the linear fit. The pore volume is then calculated from the densities of the bulk and matrix materials, respectively. In contrast to nitrogen sorption and mercury porosimetry, this method is capable of measuring the total pore volume regardless of pore size distribution and pore connectivity. In this study, three porous samples were investigated by AFM-porosimetry: one ordered mesoporous sample and two disordered foam structures. All samples were based on a matrix of amorphous silica templated by a block copolymer, Pluronic F127, swollen to various degrees with poly(propylene glycol). In addition, the density of silica spheres without a template was measured by two independent techniques: AFM and the Archimedes principle. PMID:18503284

  16. Advantages and limitations of OM, SEM, TEM and AFM in the study of ancient decorated pottery

    NASA Astrophysics Data System (ADS)

    Arenas-Alatorre, J.; Silva-Velazquez, Y.; Alva Medina, A.; Rivera, M.

    2010-03-01

    This paper presents results from the study of two fragments of pre-Hispanic pottery, decorated with red pigment, using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM). Capabilities and limitations of these techniques in the analysis of archaeological material are highlighted with special emphasis on TEM, AFM and MFM due to their contribution in the study of the pigment layer at micro and nano scale. The analyzed samples come from the archaeological sites of El Tajin and Xochicalco, both in Mexico. Results of conventional TEM and HRTEM analysis of the red pigment showed nanometric Fe2O3 particles in both samples but different particle shape and size distributions: specimen from El Tajin presented irregular particles between 50-100 nm while that from Xochicalco exhibited semispherical shapes in the 3-25 nm range. AFM images showed the topography of the pigments, which are related to the texture of their surface and thus to the production process. Finally, MFM showed different contrast regions suggesting the presence of ferromagnetic elements forming clusters and domain orientations on the color layer.

  17. Simulation of CNT-AFM tip based on finite element analysis for targeted probe of the biological cell

    NASA Astrophysics Data System (ADS)

    Yousefi, Amin Termeh; Mahmood, Mohamad Rusop; Miyake, Mikio; Ikeda, Shoichiro

    2016-07-01

    Carbon nanotubes (CNTs) are potentially ideal tips for atomic force microscopy (AFM) due to the robust mechanical properties, nano scale diameter and also their ability to be functionalized by chemical and biological components at the tip ends. This contribution develops the idea of using CNTs as an AFM tip in computational analysis of the biological cell's. Finite element analysis employed for each section and displacement of the nodes located in the contact area was monitored by using an output database (ODB). This reliable integration of CNT-AFM tip process provides a new class of high performance nanoprobes for single biological cell analysis.

  18. Linking of Sensor Molecules with Amino Groups to Amino-Functionalized AFM Tips

    PubMed Central

    2011-01-01

    The measuring tip of an atomic force microscope (AFM) can be upgraded to a specific biosensor by attaching one or a few biomolecules to the apex of the tip. The biofunctionalized tip is then used to map cognate target molecules on a sample surface or to study biophysical parameters of interaction with the target molecules. The functionality of tip-bound sensor molecules is greatly enhanced if they are linked via a thin, flexible polymer chain. In a typical scheme of tip functionalization, reactive groups are first generated on the tip surface, a bifunctional cross-linker is then attached with one of its two reactive ends, and finally the probe molecule of interest is coupled to the free end of the cross-linker. Unfortunately, the most popular functional group generated on the tip surface is the amino group, while at the same time, the only useful coupling functions of many biomolecules (such as antibodies) are also NH2 groups. In the past, various tricks or detours were applied to minimize the undesired bivalent reaction of bifunctional linkers with adjacent NH2 groups on the tip surface. In the present study, an uncompromising solution to this problem was found with the help of a new cross-linker (“acetal-PEG-NHS”) which possesses one activated carboxyl group and one acetal-protected benzaldehyde function. The activated carboxyl ensures rapid unilateral attachment to the amino-functionalized tip, and only then is the terminal acetal group converted into the amino-reactive benzaldehyde function by mild treatment (1% citric acid, 1–10 min) which does not harm the AFM tip. As an exception, AFM tips with magnetic coating become demagnetized in 1% citric acid. This problem was solved by deprotecting the acetal group before coupling the PEG linker to the AFM tip. Bivalent binding of the corresponding linker (“aldehyde-PEG-NHS”) to adjacent NH2 groups on the tip was largely suppressed by high linker concentrations. In this way, magnetic AFM tips could be

  19. High aspect ratio AFM Probe processing by helium-ion-beam induced deposition.

    PubMed

    Onishi, Keiko; Guo, Hongxuan; Nagano, Syoko; Fujita, Daisuke

    2014-11-01

    A Scanning Helium Ion Microscope (SHIM) is a high resolution surface observation instrument similar to a Scanning Electron Microscope (SEM) since both instruments employ finely focused particle beams of ions or electrons [1]. The apparent difference is that SHIMs can be used not only for a sub-nanometer scale resolution microscopic research, but also for the applications of very fine fabrication and direct lithography of surfaces at the nanoscale dimensions. On the other hand, atomic force microscope (AFM) is another type of high resolution microscopy which can measure a three-dimensional surface morphology by tracing a fine probe with a sharp tip apex on a specimen's surface.In order to measure highly uneven and concavo-convex surfaces by AFM, the probe of a high aspect ratio with a sharp tip is much more necessary than the probe of a general quadrangular pyramid shape. In this paper we report the manufacture of the probe tip of the high aspect ratio by ion-beam induced gas deposition using a nanoscale helium ion beam of SHIM.Gas of platinum organic compound was injected into the sample surface neighborhood in the vacuum chamber of SHIM. The decomposition of the gas and the precipitation of the involved metal brought up a platinum nano-object in a pillar shape on the normal commercial AFM probe tip. A SHIM system (Carl Zeiss, Orion Plus) equipped with the gas injection system (OmniProbe, OmniGIS) was used for the research. While the vacuum being kept to work, we injected platinum organic compound ((CH3)3(CH3C5H4)Pt) into the sample neighborhood and irradiated the helium ion beam with the shape of a point on the apex of the AFM probe tip. It is found that we can control the length of the Pt nano-pillar by irradiation time of the helium ion beam. The AFM probe which brought up a Pt nano-pillar is shown in Figure 1. It is revealed that a high-aspect-ratio Pt nano-pillar of ∼40nm diameter and up to ∼2000 nm length can be grown. In addition, for possible heating

  20. Mechanical properties of UO2 thin films under heavy ion irradiation using nanoindentation and finite element modeling

    NASA Astrophysics Data System (ADS)

    Elbakhshwan, Mohamed S.; Miao, Yinbin; Stubbins, James F.; Heuser, Brent J.

    2016-10-01

    The mechanical response of UO2 to irradiation is becoming increasingly important due to the shift to higher burn-up rates in the next generation of nuclear reactors. In the current study, thin films of UO2 were deposited on YSZ substrates using reactive-gas magnetron sputtering. Nanoindentation was used to measure the mechanical properties of the as-grown and irradiated films. Finite element modeling was used to account for the substrate effect on the measurements. In order to study the effect of displacement cascades accompanying gas bubbles, 5000 Å UO2 films were irradiated with 600 keV Kr+ ions at 25 °C and 600 °C. These irradiation conditions were used to confine radiation damage effects and implanted gas within the film. Results showed an increase in the film hardness and yield strength with dose, while elastic modulus initially decreased with irradiation and then kept increasing with dose. The change in hardness and elastic modulus is attributed to the introduction of gas bubbles and displacement cascade damage. Irradiation at 600 °C resulted in a decrease in the hardness and elastic modulus after irradiation using 600 keV Kr+ at a dose of 1E14 ions/cm2. Both hardness and elastic modulus then increased with irradiation dose. This behavior is attributed to recrystallization during irradiation at 600 °C and the formation of nanocrystallite regions with diameter and density that increase with dose. The calculation of the critical resolved shear stress (CRSS) demonstrated that nanocrystals are the primary cause for film hardening based on the Orowan hardening mechanism.