Dissertations / Theses on the topic 'Atomic Force Microscopy'
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Payton, Oliver David. "High-speed atomic force microscopy under the microscope." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574416.
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SINCE its invention in 1986, the atomic force microscope (AFM) has revolutionised the field of nanotechnology and nanoscience. It is a tool that has enabled research into areas of medicine, advanced materials, biology, chemistry and physics. However due to its low frame rate it is a tool that has been limited to imaging small areas using a time lapse technique. It has only been in recent years that the frame rate of the device has been increased in a tool known as high-speed AFM (HSAFM). This increased frame rate allows, for the first time, biological processes to be viewed in real time or macro sized areas to be imaged with nanoscale resolution. The research presented here concentrates on a specific type of high-speed AFM developed at the University of Bristol called contact mode HSAFM. This thesis explains how the microscope is able to function, and presents a leap in image quality due to an increased understanding of the dynamics of the system. The future of the device is also discussed. III
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Grimble, Ralph Ashley. "Atomic force microscopy : atomic resolution imaging and force-distance spectroscopy." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312277.
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Carnally, Stewart Antoni Michael. "Carbon nanotube atomic force microscopy." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491631.
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This thesis concerns the manufacture of carbon nanotube atomic force microscope (NTAFM) probes and their employment in the high-resolution imaging of biological macromolecules. Attention was focused initially on synthesis of carbon nanotubes and the refinement of the growth processes to obtain nanotubes of controlled dimensions. These growth processes were subsequently used to grow nanotubes directly onto AFM tips, followed by attempts at controlling the dimensions of these directly-grown nanotubes. Individually fabricated NTAFM probes are also described, along with attempts to optimise the strength of the AFM probe-nanotube interaction through the use of various hydrophobic coatings. NTAFM probes produced by both techniques, but predominantly through individually assembled probes using hydrophobic coatings, were used to image a range of natural and synthetic nucleic acid molecules and investigate the influence of the use of a nanotube probe on the dimensions observed.
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Jeong, Younkoo. "HIGH SPEED ATOMIC FORCE MICROSCOPY." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236701109.
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Vithayaveroj, Viriya. "Atomic force microscopy for sorption studies." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-09282004-121825/unrestricted/vithayaveroj%5Fviriya%5F200412%5Fphd.pdf.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2005.Dr. Rina Tannenbaum, Committee Member ; Dr. Michael Sacks, Committee Member ; Dr. Sotira Yiacoumi, Committee Chair ; Dr. Costas Tsouris, Committee Co-Chair ; Dr. Ching-Hua Huang, Committee Member. Vita. Includes bibliographical references.
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Muys, James Johan. "Cellular Analysis by Atomic Force Microscopy." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1158.
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Exocytosis is a fundamental cellular process where membrane-bound secretory granules from within the cell fuse with the plasma membrane to form fusion pore openings through which they expel their contents. This mechanism occurs constitutively in all eukaryotic cells and is responsible for the regulation of numerous bodily functions. Despite intensive study on exocytosis the fusion pore is poorly understood. In this research micro-fabrication techniques were integrated with biology to facilitate the study of fusion pores from cells in the anterior pituitary using the atomic force microscope (AFM). In one method cells were chemically fixed to reveal a diverse range of pore morphologies, which were characterised according to generic descriptions and compared to those in literature. The various pore topographies potentially illustrates different fusion mechanisms or artifacts caused from the impact of chemicals and solvents in distorting dynamic cellular events. Studies were performed to investigate changes in fusion pores in response to stimuli along with techniques designed to image membrane topography with nanometre resolution. To circumvent some deficiencies in traditional chemical fixation methodologies, a Bioimprint replication process was designed to create molecular imprints of cells using imprinting and soft moulding techniques with photo and thermal activated elastomers. Motivation for the transfer of cellular ultrastructure was to enable the non-destructive analysis of cells using the AFM while avoiding the need for chemical fixation. Cell replicas produced accurate images of membrane topology and contained certain fusion pore types similar to those in chemically fixed cells. However, replicas were often dehydrated and overall experiments testing stimuli responses were inconclusive. In a preliminary investigation, a soft replication moulding technique using a PDMS-elastomer was tested on human endometrial cancer cells with the aim of highlighting malignant mutations. Finally, a Biochip comprised of a series of interdigitated microelectrodes was used to position single-cells within an array of cavities using positive and negative dielectrophoresis (DEP). Selective sites either between or on the electrode were exposed as cavities designed to trap and incubate pituitary and cancer cells for analysis by atomic force microscopy (AFMy). Results achieved trapping of pituitary and cancer cells within cavities and demonstrated that positive DEP could be used as a force to effectively position living cells. AFM images of replicas created from cells trapped within cavities illustrated the advantage of integrating the Biochip with Bioimprint for cellular analysis.
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Konopinski, D. I. "Forensic applications of atomic force microscopy." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1402411/.
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The first project undertaken was to develop a currently non-existent forensic technique -- data recovery from damaged SIM cards. SIM cards hold data valuable to a forensic investigator within non-volatile EEPROM/flash memory arrays. This data has been proven to be able to withstand temperatures up to 500°C, surviving such scenarios as house fires or criminal evidence disposal. A successful forensically-sound sample extraction, mounting and backside processing methodology was developed to expose the underside of a microcontroller circuit's floating gate transistor tunnel oxide, allowing probing via AFM-based electrical scanning probe techniques. Scanning Kelvin probe microscopy has thus far proved capable of detecting the presence of stored charge within the floating gates beneath the thin tunnel oxide layer, to the point of generating statistical distributions reflecting the threshold voltage states of the transistors. The second project covered the novel forensic application of AFM as a complimentary technique to SEM examination of quartz grain surface textures. The analysis and interpretation of soil/sediment samples can provide indications of their provenance, and enable exclusionary comparisons to be made between samples pertinent to a forensic investigation. Multiple grains from four distinct sample sets were examined with the AFM, and various statistical figures of merit were derived. Canonical discriminant analysis was used to assess the discriminatory abilities of these statistical variables to better characterise the use of AFM results for grain classification. The final functions correctly classified 65.3% of original grouped cases, with the first 3 discriminant functions used in the analysis (Wilks' Lambda=0.336, p=0.000<0.01). This degree of discrimination shows a great deal of promise for the AFM as a quantitative corroborative technique to traditional SEM grain surface examination.
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Acosta, Mejia Juan Camilo. "Atomic force microscopy based micro/nanomanipulation." Paris 6, 2011. http://www.theses.fr/2011PA066691.
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A l’échelle nanoscopique, un problème scientifique fondamental réside dans la difficulté de manipuler de façon interactive et répétable un nano-objet. Cette difficulté est un frein majeur pour des applications comme les nanotransistors, les nanosystèmes ou les futurs NEMS (Nano Electro Mechanical System). Ces dispositifs émergents sont ainsi ralentis dans leur cadre expérimental. Cette thèse s’inscrit dans la continuité des recherches développées au sein de l’équipe de microrobotique de l'ISIR. Elle se focalise sur l'exploitation de capteurs d'effort pour la manipulation contrôlée à plusieurs doigts actifs. Le microscope à force atomique est utilisé pour ses propriétés de capteur d'effort. Dans un premier temps, un préhenseur composé de deux doigts indépendants avec mesures des forces d'interaction a été conçue. Avec ce système original, des micromanipulations en trois dimensions de microsphères ont été réalisée avec succès dans l'air, en mesurant de façon continue les efforts d'interaction. Ce système a aussi été utilisé pour saisir et déposer des nanofils afin de former des nanocroix, ces dernières étant des nanostructures émergentes pour la fabrication, par jonctions, de nanotransistors. Par la suite, des oscillateurs en quartz ont été utilisés pour la caractérisation de nanostructures, avec retour d'effort dynamique. Le comportement non-linéaire en raideur de nanohélices lors de l'élongation a été caractérisé pour la première fois sur la totalité de la plage. Enfin, des sondes en quartz de haute fréquence ont été exploitées pour augmenter la vitesse d'acquisition d'images de l'AFM. De cette manière, la tâche de manipulation et d'imagerie en parallèle sous AFM a été optimisée et de nombreuses applications sont maintenant envisagées
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Sykulska-Lawrence, Hanna Maria. "Atomic force microscopy for Martian investigations." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4396.
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The Phoenix Mars Lander includes a Microscopy, Electrochemistry and Conductivity Analyser (MECA) instrument for the study of dust and regolith at the Martian arctic. The microscopy payload comprises an AFM and Optical Microscope (OM) to which samples are delivered by a robot arm. The setup allows imaging of individual dust and soil particles at a higher spatial resolution than any other in-situ instrument. A fully functioning test-bed of the flight microscopy setup within an environmental chamber to simulate Mars conditions was assembled at Imperial College, enabling characterization of the microscopes. Samples are collected on small disks rotated to the vertical position for imaging, with each substrate surface promoting different adhesion mechanisms. The vertical mounting necessitates good adhesion of particles to substrates. Moreover, to achieve safe operation and good AFM scans, a sparse field of particles is required. This work investigates models and experimental setups which consider the adhesion mechanisms of particles, including under Mars conditions. These models incorporate the forces from the AFM cantilever during scanning, particle-substrate adhesion and particle-tip adhesion. The solution offered to the problem of unstable particles is substrates with engineered features, micromachined in silicon, to trap and stabilise particles for AFM and reduce the loading of the sample to a suitable level. Various designs were investigated in a series of tests, and a final design was created for a substrate for AFM during the mission. The substrates were fabricated and incorporated on the sample wheel on Phoenix, now on Mars. The MECA results are discussed, focusing in particular on the characterization, calibration and cataloguing of samples using the Imperial College testbed. The best ways of obtaining data from the setup were investigated. These strategies were used during the Phoenix mission. Finally, the extant microscopy data acquired during surface operations are presented and the overall operations procedures discussed.
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Anderson, Evan V. "Atomic Force Microscopy: Lateral-Force Calibration and Force-Curve Analysis." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/337.
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This thesis reflects two advances in atomic force microscopy. The first half is a new lateral force calibration procedure, which, in contrast to existing procedures, is independent of sample and cantilever shape, simple, direct, and quick. The second half is a high-throughput method for processing, fitting, and analyzing force curves taken on Pseudomonas aeruginosa bacteria in an effort to inspire better care for statistics and increase measurement precision.
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Cisneros, Armas David Alejandro. "Molecular assemblies observed by atomic force microscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1182777560689-53566.
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We use time-lapse AFM to visualize collagen fibrils self-assembly. A solution of acid-solubilized collagen was injected into the AFM fluid cell and fibril formation was observed in vitro. Single fibrils continuously grew and fused with each other until the supporting surface was completely covered by a nanoscopically well-defined collagen matrix. Laterally, the fibrils grew in steps of ~4 nm suggesting a two-step mechanism. In a first step, collagen molecules associated together. In the second step, these molecules rearranged into a structure called a microfibril. High-resolution AFM topographs revealed substructural details of the D-band architecture. These substructures correlated well with those revealed from positively stained collagen fibers imaged by transmission electron microscopy. Secondly, a covalent assembly approach to prepare membrane protein for AFM imaging that avoids crystallization was proposed. High-resolution AFM topographs can reveal structural details of single membrane proteins but, as a prerequisite, the proteins must be adsorbed to atomically flat mica and densely packed in a membrane to restrict their lateral mobility. Atomically flat gold, engineered proteins, and chemically modified lipids were combined to rapidly assemble immobile and fully oriented samples. The resulting AFM topographs of single membrane proteins were used to create averaged structures with a resolution approaching that of 2D crystals. Finally, the contribution of specific amino acid residues to the stability of membrane proteins was studied. Two structurally similar proteins sharing only 30% sequence identity were compared. Single-molecule atomic force microscopy and spectroscopy was used to detect molecular interactions stabilizing halorhodopsin (HR) and bacteriorhodopsin (BR). Their unfolding pathways and polypeptide regions that established stable segments were compared. Both proteins unfolded exactly via the same intermediates. This 3 Molecular Assemblies observed by AFM observation implies that these stabilizing regions result from comprehensive contacts of all amino acids within them and that different amino acid compositions can establish structurally indistinguishable energetic barriers. However, one additional unfolding barrier located in a short segment of helix E was detected for HR. This barrier correlated with a Pi-bulk interaction, which locally disrupts helix E and divides into two stable segments.
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Sobek, Joanna Amanda. "Atomic force microscopy studies of potassium channels." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669955.
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Markiewicz, Peter C. "Atomic force microscopy studies of mesoscopic structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq35239.pdf.
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Spitzner, Eike-Christian. "Subsurface and MUSIC-Mode Atomic Force Microscopy." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-94864.
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Ziel dieser Arbeit war die Entwicklung neuer Methoden in der Rasterkraftmikroskopie, um die Qualität und Interpretierbarkeit von Oberflächenabbildungen auf der Nanometerskala, vor allem jener sehr weicher Proben, entscheidend zu verbessern. Der für polymere und biologische Materialien standardmäßig verwendete intermittierende Kontaktmodus führt auf weichen Oberflächen zu verfälschten Abbildungen der Topographie und der mechanischen Eigenschaften. In dieser Arbeit wurden Techniken entwickelt, die einerseits zerstörungsfreie, tiefenaufgelöste Rasterkraftmikroskopie und andererseits Einzelmessungen mit variabler Dämpfung im intermittierenden Kontaktmodus ermöglichen. Die laterale Auflösung beider Methoden liegt dabei im Rahmen herkömmlicher Techniken (< 10 nm). Die Tiefenauflösung konnte im Vergleich zu anderen Methoden um eine Größenordnung auf unter 1 nm verbessert werden. Die neuen Methoden wurden auf einer breiten Palette polymerer Materialien angewandt. Die räumliche Struktur oberflächennaher Bereiche eines Blockcopolymerfilms konnte im Vergleich zu herkömmlichen Methoden deutlich genauer abgebildet werden. Gleiches wurde auf elastomerem Polypropylen erreicht. Es konnten weiche, amorphe Deckschichten auf teilkristallinen Polymeren nachgewiesen und vermessen werden, was in der organischen Elektronik eine wichtige Rolle spielen kann. Die innere Struktur selbstangeordneter Nanodrähte aus Oligothiophen-Aggregaten konnte aufgelöst werden und es wurde die Selbstanordnung von Kollagenfibrillen im gequollenen Zustand beobachtet.
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Smith, Benjamin A. "Cellular biomechanics investigated by atomic force microscopy." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85648.
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Living biological cells are highly complex, multifunctional systems whose physical attributes are relatively unknown. Critical functions involving plasticity of cell morphology, connectivity and response to stimuli are proposed to be fundamentally related to the micromechanical character and the ability of the cell to exert directed mechanical signaling. Unique abilities of atomic force microscopy in measuring cellular viscoelastic properties (on length scales from nanometers to microns) are explored with specific applications to (1) airway smooth muscle cells and (2) hippocampal neurons. Surface indentation techniques for stiffness mapping, as well as quantitative measurements of frequency-dependent complex rheology are featured. Structural and molecular determinants of dynamic mechanical behavior are identified. In smooth muscle cells, an isotropic fiber network provides strong resistance to deformation. Actin polymerization is largely responsible for stiffening following contractile activation, not myosin cross-bridge formation as expected. On neuronal dendrites, stiffness contrast correlates with known distributions and stability of cytoskeletal elements: microtubules along the shafts and dynamic actin in the spines (micron-sized surface protrusions). Focus is given to dendritic spines as the post-synaptic contact sites for most excitatory transmission between neurons. Large heterogeneity is observed in spine mechanical properties, but stiffer spines appear to be associated with axon-like contacts. Spines may stiffen in response to synaptic stimulation, in agreement with recent observations of actin-based stabilization of spine shape (reduced motility) following excitatory treatments.Remarkably, the frequency dependence of the complex shear moduli (0.5-100 Hz indentations) of both cellular systems is described well by the same rheological model: that of soft glassy materials existing just above the glass transition. The central feature of this model is that storage ( G') and loss moduli (G") scale in parallel as a weak power-law function of frequency. Power-law exponents (alpha), measured to be of the order 0.1, are related to the level of molecular agitations in the cell and determine the degree of solid-like (G' >> G" with a glass transition at alpha = 0) or fluid-like behavior (G' << G" with alpha = 1 for a pure fluid). The soft glassy hypothesis is founded on the concepts of disorder and metastability of structural elements. A Newtonian viscosity (pure fluid) component is also identified with significant effects for high frequency deformations. Together these properties are critical for describing cellular remodeling: contraction in smooth muscle cells or synaptic plasticity at dendritic spines.
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Jarvis, Suzanne Philippa. "Atomic force microscopy and tip-surface interactions." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359441.
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Cassidy, A. M. C. "Probing pharmaceutical materials using atomic force microscopy." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597359.
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Microscopic techniques were used to study the surface behaviour of model active pharmaceutical ingredients (APIs) and excipients, while under stress, and this was compared with the response of the bulk material. The model APIs were caffeine/oxalic acid, caffeine/malonic acid cocrystals and aspirin whilst spheronised microcrystalline cellulose (s-MCC), pregelatinised starch (PGS) and dicalcium phosphate dehydrate served as examples of excipients. The difference between the surface and bulk behaviour of caffeine cocrystals in response to storage in controlled humidity environments was investigated. Surface imaging illustrated an anisotropic element to the microstructure of the caffeine cocrystals, which became more pronounced at the extremities of relative humidity (RH) storage. The trends in surface reactivity which were observed for the cocrystals were found to follow those previously reported for bulk behaviour, using PXRD. Atomic force microscopy imaging, however, gave an earlier indication of incompatibility between the ecocrystals and > 75% RH, with surface transformations occurring on a shorter timescale than indicated from the results of bulk analysis. This work represents the first reported analysis of organic molecular cocrystals by AFM. The material properties and subsurface structure of s-MCC and PGS were examined using AFM. Phase imaging and force measurements identified heterogeneity in the material properties of these excipient particles. In the case of s-MCC, the results were used to support a theory for intragranular porosity. The solid-state hydrolysis of aspirin crystals in the presence of dicalcium phosphate dehydrate was studied, using in situ AFM techniques.
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Sapcharoenkun, Chaweewan. "Controlled nanostructure fabrication using atomic force microscopy." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7593.
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Scanning probe microscopy (SPM) nanolithography has been found to be a powerful and low-cost approach for sub-100 nm patterning. In this thesis, the possibility of using a state-of-the-art SPM system to controllably deposit nanoparticles on patterned Si substrates with high positional control has been explored. These nanoparticles have a range of interesting properties and have been characterised by electron microscopy and scanning probe microscopy. The influence of different deposition parameters on the nanoparticle properties was studied. Contact mode atomic force microscopy (AFM)-based local oxidation nanolithography (LON) was used to oxidise sample surfaces. Two different substrates were studied which were native oxide silicon (Si) and molybdenum (Mo). A number of factors that influence the height and width of the oxide features were investigated in order to achieve the optimal oxidation efficiency. The height and width of the oxide structures were found to be strongly dependent on the applied voltage and scan speed. The tunneling AFM (TUNA) technique was used to measure the ultralow currents flowing between the tip and the sample during the oxidation process. It was found that a threshold voltage for our oxidation experiments was -4.0 ± 1.6 V applied to the tip when fabricating geometric patterns as well as 2.9 ± 1.6 V and 2.8 ± 2.2 V applied to the substrate for nanodot fabrication. In addition, comparisons of nanodot-array patterns produced with different AFM tips were studied. The influence of applied voltage, type of AFM tip and substrate, humidity and ramping time has been studied for dot formation providing a comparison between native oxide Si and Mo surfaces. The nanodot sizes were found to be clearly dependent on the applied voltage, type of substrate, relative humidity and ramping time. Dip-pen nanolithography (DPN) was used to study a direct deposition strategy for gold (Au) nanodot fabrication on a native oxide Si substrate. In this process, hydrogen tetrachloroaurate (HAuCl4) molecules were deposited onto the substrate via a molecular diffusion process, in the absence of electrochemical reactions. This approach allowed for the generation of Au dots on the SiO2 substrate without the need for surface modification or additional electrode structures. The dependence of the size of the Au dots on different „scanning coating‟ (SC) times of AFM tips was studied. A thermal annealing process was used to decompose the generated HAuCl4 molecular dots to leave Au (0) metal dots. A stereomicroscope has been used for preliminary observation of different steps of Au deposition treatments. A scanning electron microscope (SEM) was used to characterise the SC AFM tips both before and after the DPN process. SEM energy-dispersive X-ray spectroscopy (EDS) has provided information about the elemental content of deposited particles for different annealing temperatures. Fountain-pen nanolithography (FPN) has also been used to study nanowriting of HAuCl4 salt and a variety of solvents on a native oxide Si surface. In this technique, a nanopipette was mounted within an AFM to deliver appropriate solutions to the silica substrate. We found that an aqueous Au salt solution was the most suitable ink for depositing gold using the FPN technique. In the case of solvents alone, ethanol and toluene were achieved with depositing onto a SiO2 substrate using the FPN technique.
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Baker, Andrew Arthur. "High resolution atomic force microscopy of polysaccharides." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264076.
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Mazzeo, Aaron D. (Aaron David) 1979. "Accurate capacitive metrology for atomic force microscopy." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33912.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 219-224).
This thesis presents accurate capacitive sensing metrology designed for a prototype atomic force microscope (AFM) originally developed in the MIT Precision Motion Control Lab. The capacitive measurements use a set of commercial capacitance sensors intended primarily for use against a flat target. In our design, the capacitance sensors are used with a spherical target in order to be insensitive to target rotations. The moving AFM probe tip is located approximately at the center of the spherical target to make the capacitive sensing insensitive to the probe tip assembly's undesirable rotation on the order of 3 x 10⁻⁴ rad for 10 [mu]m of lateral travel [48]. To accurately measure displacement of the spherical target relative to the capacitance sensors, models for the capacitance between a sphere and a circular disc were developed with the assistance of Katherine Lilienkamp. One of the resulting non-linear models was combined with the appropriate kinematic transformations to accurately perform measurement scans on a 20 [mu]m x 20 [mu]m surface with step heights of 26.5 nm. The probe tip positions during these scans were also calculated in real- time using Lilienkamp's non-linear capacitance model with a set of transformations and 3-D interpolation techniques implemented at 10 kHz. The scans were performed both in tapping and shear detection modes.
(cont.) Localized accuracy on the order of 1 nm with RMS noise of approximately 3 nm was attained in measuring the step heights. Surface tracking control and speed were also improved relative to an earlier prototype. Lateral speeds of approximately 0.8 [mu]m/s were attained in the tapping mode. In addition to improving the original prototype AFM's scan speed and ability to attain dimensional accuracy, a process for mounting an optical fiber probe tip to a quartz tuning fork was developed. This mounting process uses Post-it notes. These resulting probe-tip/tuning-fork assemblies were tested in both the tapping and shear modes. The tests in the tapping mode used the magnitude of the fork current for accurate surface tracking. The tests performed in the shear mode used the magnitude and phase of the fork current for accurate surface tracking.
by Aaron David Mazzeo.
S.M.
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Yeo, Yee 1977. "Image processing for precision atomic force microscopy." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88854.
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Vicary, James Alexander. "High-speed atomic force microscopy for nanofabrication." Thesis, University of Bristol, 2006. http://hdl.handle.net/1983/b79a500e-8856-470f-a3aa-bde7f531cb0a.
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Sun, Mingzhai. "Cell mechanics studied using atomic force microscopy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5499.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on June 17, 2009) Vita. Includes bibliographical references.
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Dudda, Bruna. "Morphology of leds by atomic force microscopy." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6647/.
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The concern of this work is to present the characterization of blue emitting GaN-based LED structures by means of Atomic Force Microscopy. Here we show a comparison among the samples with different dislocation densities, in order to understand how the dislocations can affect the surface morphology. First of all we have described the current state of art of the LEDs in the present market. Thereafterwards we have mentioned in detail about the growth technique of LED structures and the methodology of the characterization employed in our thesis. Finally, we have presented the details of the results obtained on our samples studied, followed by discussions and conclusions.
L'obiettivo di questa tesi é quello di presentare la caratterizzazione mediante Microscopia a Forza Atomica di strutture di LED a emissione di luce blu a base di nitruro di gallio (GaN). Viene presentato un confronto tra campioni con differente densità di dislocazioni, allo scopo di comprendere in che modo la presenza di dislocazioni influisce sulla morfologia della superficie. Innanzitutto, viene descritto il presente stato dell'arte dei LED. Successivamente, sono forniti i dettagli riguardanti la tecnica di crescita delle strutture dei LED e il metodo di caratterizzazione adottato. Infine, vengono mostrati e discussi i risultati ottenuti dallo studio dei campioni, seguiti dalle conclusioni.
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Barker, Emily Clare. "Characterisation of Gelation by Atomic Force Microscopy." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/85526.
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This thesis presents investigations into supramolecular gels by Atomic Force Microscopy (AFM), rheometry and Small Angle Neutron Scattering (SANS) to study the assembly and disassembly processes of gels and their physical properties to develop a deeper understanding of the relationship between microscopic and macroscopic properties of gels. Supramolecular gels, which have a reversible nature and can be switched via external stimuli, and peptide gels of biological relevance were studied with the above-mentioned techniques.
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Mattocks, Philip. "Scanning tunnelling microscopy and atomic force microscopy of semiconducting materials." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/scanning-tunnelling-microscopy-and-atomic-force-microscopy-of-semiconducting-materials(9bc10301-2c4d-4dfb-a374-f65ee37ae23a).html.
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Michael Faraday first documented semiconducting behaviour in 1833 whenhe observed that the resistance of silver sulphide decreased with temperature,contrary to the behaviour of normal conducting materials. Up untilthe middle of the twentieth century, semiconductors were used as photodetectors,thermisters and rectifiers. In 1947 the invention of the transistor byBardeen and Brattain lead to the integrated circuit and paved the way formodern electronics. The need to produce smaller and faster transistors hasdriven research into new semiconductors. This thesis will first introduce the physics of semiconductors, followed bya description of the experimental techniques employed; scanning tunnellingmicroscopy (STM) and atomic force microscopy (AFM). Chapter 3 is concernedwith explaining anomalous scanning tunnelling spectroscopy resultsobtained for Si(100) and GaAs(110). To this end, a one-dimensional planarmodel, in which surface states affect the charge distribution and tunnellingin the system is proposed. Graphene, a novel two-dimensional material,is introduced in Chapter 4. Scanning tunnelling microscopy measurementsof graphene suspended on a metal grid are presented in this chapter. Finally,Indium antimonide Schottky contacts are investigated using conductingatomic force microscopy in Chapter 5.
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Clarke, Richard John. "Hydrodynamics of the atomic force microscope." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/10649/.
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With a proven ability to uncover fundamental biological processes, the atomic force microscope (AFM) represents one of the most valuable and versatile tools available to the biophysical sciences. We study the unsteady small-scale flows generated within the AFM by its sensing probe (a long thin cantilever), which have received relatively little attention to date, yet which are increasingly relevant in an age of microdevices. The early parts of this thesis investigate some canonical two-dimensional flows driven by oscillations of an infinite-length rigid cantilever. These prove amenable to analysis and enable us to investigate many of the important physical phenomena and compile a comprehensive collection of asymptotic expressions for the drag. The corresponding results lay out the influence of a nearby wall, geometry and oscillation frequency. The limitations of a two-dimensional approach are then explored through the development of a novel unsteady slender-body theory (USBT) for finite-length cylinders, an asymptotic treatment of which offers corrections to traditional resistive-force-theory (RFT) methods by accounting for geometric factors and flow inertia. These ideas are then extended to the study of thin rectangular plates. Two key parameters are identified which promote two-dimensionality in the flow, namely the frequency of oscillation and the proximity of a nearby boundary. We then examine flexible cylinders and plates by coupling the hydrodynamics to linearized elastic beam and plate equations, which simulate the hydrodynamically-damped high-speed deformable motion of the AFM's cantilever, when driven either externally or by Brownian motion. In the latter case, we adopt an approach which offers notable improvements over the most advanced method currently available to the AFM community.
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Sweetman, Adam. "Forces at the nanoscale : interactions in atomic force microscopy and dielectrophoresis." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11213/.
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Interactions at the nanoscale are governed almost exclusively by electromagnetic forces, but the interplay between different scaling laws produces a vast array of behaviours. We investigate radically different systems spanning almost three orders of magnitude of length scales, and use a variety of experimental techniques to determine the forces present in each regime, and the interplay between them. An important prototypical surface in SPM science has been the Si(100) surface, which due to it’s unstable buckling and complex electronic structure has fostered considerable debate in the surface science community. We have used small amplitude, high sensitivity combined qPlus STM/AFM to investigate tip -- sample interactions on the Si(100) surface at low-temperature in UHV, with a focus on the chemical, and electronic properties of the system and how these are modified by the probe. We present the first atomic resolution combined force/tunnel current results on the surface and show that great care must be taken in interpreting either pure AFM or pure STM data. We also examine tip -- sample interactions on arrays of thiol passivated spin-cast nanoparticles in both UHV and ambient conditions and show for the first time how minor modifications to the experimental parameters can radically alter the data collected, most likely due to the thiol -- surface -- tip interaction. We also present SKPM and voltage spectroscopy of the same samples and show the importance of electrostatic interactions in correct height determination of these network arrays, in parallel with the caution that must be maintained in interpreting CPD data. A key mechanism for the manipulation of meso-scale objects in solution is Dielelectrophoresis, which offers strong material and size specificity and a high degree of spatial control. In the final experimental chapter we investigate the effect of inhomogenous electric fields on nanoparticles in aqueous solution, and reveal how previously uninvestigated electrochemical effects can become important even at high frequencies, and may offer a new and exciting route for the control of self organised nanowires in solution.
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Farstad, Mari Helene. "Atomic force microscopy studies of wool fibre structures." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6802.
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Gale, Marla. "Collagen assembly as examined by atomic force microscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1995. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ45475.pdf.
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Gießibl, Franz J. [Verfasser]. "Progress in atomic force microscopy / Franz J. Gießibl." Augsburg : Universität Augsburg, 2007. http://d-nb.info/1077692749/34.
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Brownhill, Matthew. "Atomic Force Microscopy Studies of Supported Biological Molecules." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517793.
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Round, Andrew Neal. "Atomic force microscopy of plant cell wall polysaccharides." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297475.
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Sedman, Victoria L. "Atomic force microscopy investigations of peptide self-assembly." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10297/.
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The ability of short peptide fragments to self-assemble in isolation as amyloid and amyloid-like structures has prompted their use as model systems for the study of amyloid formation and recently also for their utilisation as novel nanofibrillar material. The atomic force microscope (AFM) is used here to investigate the self-assembly of two peptide systems and the development of strategies to directly manipulate and control the structures they form. The studies presented in Chapter 2 address the self-assembly of a peptide fragment of the human amylin polypeptide; amylin (20-29). In the opening study we use ex situ AFM imaging to characterise the early stages of amylin (20-29) fibril formation. High-resolution images reveal that following an initial lag phase, fibrils displaying a globular appearance are formed, which over time are replaced by flat ribbon-like fibrils with no periodicity displaying a range of polymorphic structures and assemblies. Following on from these findings, we investigate the influence of solution conditions on amylin (20-29) fibril formation utilising in situ AFM imaging. Altering the pH and electrolyte composition affords a range of morphologies including, truncated and long branched or unbranched flexible fibrils and globular aggregates. Following on from this characterisation chapter, in Chapter 3 a strategy to assemble specifically functionalised fibrillar material from chemically modified amylin (20-29) peptides was investigated. Azide and alkyne moieties were successfully coupled to the amylin (20-29) peptides. Ex situ AFM imaging and Congo red binding confirmed that the additional steric bulk had no detrimental effects on the fibril forming capacity of the peptides. Finally, in Chapter 4 the focus turns to the self-assembly of a dipeptide of phenylalanine which corresponds to the core recognition motif of the beta-amyloid polypeptide. Here, the AFM is used to study the physical properties of the well-ordered, discrete, hollow nanotubes which are formed. Their chemical stability in organic solvents and considerable thermal stability under both dry and wet heating conditions is revealed. Finally, the use of strong magnetic fields to directly control and orientate the diphenylalanine nanotubes was examined by AFM. The results presented throughout this thesis demonstrate the versatility of self-assembling peptides for the generation of fibrillar nanostructures that can be directly modified and controlled to generate novel architectures and functionalised well ordered nanomaterials.
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Blackley, Harriet. "Atomic force microscopy investigations of β-amyloid fibrillization." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311761.
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Winkel, Alexander Kevin. "Atomic force microscopy of polymer and oligomer surfaces." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247543.
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Suresh, Swetha. "Probing protein-lipid interactions using atomic force microscopy." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609231.
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Glynos, Emmanouil. "Atomic force microscopy on self-assembled polymer structures." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/13925.
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In Part A we started our studies by investigating the morphology of physisorbed linear and star polybutadiene (PB) on a freshly cleaved mica surface from dilute solution after solvent evaporation . For the case of linear PB, we found that the dependence of the Mw on the observed polymer structures is crucial for samples with relatively high surface density where the interactions among the adsorbed polymers become significant. For a relatively high surface density we observed a tendency of the adsorbed polymers to aggregate for all the molecular weight molecules and an isotropic structural pattern was observed. We explained these structural phenomena with increasing surface density in terms of the molecular interactions of the adsorbed polymers when in good solvent conditions and after the abrupt solvent evaporation. For the case of star PB we present a study of the structure and growth of star shaped polymer monolayers on mica. The fine structure study revealed that the monolayer morphology depends strongly on the functionality (number of arms) of the star polymer. We studied poly(isoprene-b-ethylene oxide) block copolymer micelles on mica under ambient conditions (in our laboratory). We found that the time dependent behaviour of the polymeric islands arises from the surface 'aging’ of freshly cleaved muscovite mica from highly hydrophillic when freshly cleaved to less hydrophillic with the exposure time in ambient conditions. In part B the AFM is proposed for the first time as a tool to image the surface of polymer microbubbles at the nanometer range in liquid and to perform reproducible measurements on the nano/micro mechanical properties. We applied the AFM to assess structural aspects of the microbubble shell and probe their mechanical properties. As microbubbles are large objects compared to the overall size of usual AFM tips a convolution between the AFM tip and the microbubble was typical of the acquired topographies. However, a small part of the top of the bubble was imaged with nanometer resolution and roughness measurements are reported. Using contact mode AFM force-distance curves were captured and the range of stiffness (or effective spring constant) of BiSphere microbubbles was systematically measured.
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Mela, Ioanna. "Alternative DNA structures, studied using atomic force microscopy." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648609.
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Looi, Lisa. "Interaction between polystyrene spheres by atomic force microscopy." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844419/.
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The interaction between a single polystyrene particle and a polystyrene substrate has been previously reported by a number of investigators. However, the effects of relative humidity, applied load and contact time on the adhesion of polystyrene surfaces have not been investigated and these effects are poorly understood. It is the primary aim of the current work to characterise the effect of the aforementioned parameters on the adhesion of polystyrene surfaces using atomic force microscopy. The polystyrene used in this study contained 1% of divinyl benzene as a cross-linking agent. The adhesion forces between an individual polystyrene particle, normally 12-14 mum in diameter, and the surface of a compacted tablet of the same material have been measured at various relative humidities using a custom-built instrument and a commercial AFM. The commercial instrument has the capability of scanning the sample surface, and allowing greater control over the relative motion between the sample and probe. One of the achievements of this work is that a technique has been developed whereby an image of the surface of the tablet can be obtained using the attached particle as a probe scanning in non-contact mode. From the work conducted using the custom-built instrument, the dependency of adhesion forces on the relative humidity is greatest at relative humidities above 60% where capillary forces cause a sharp increase in adhesion with increasing relative humidity. Hysteresis was observed in the solid-solid contact gradient of the accompanying force curves, suggesting non-elastic behaviour at the contact area of the surfaces. Using the commercial AFM it was observed that adhesion values are consistently higher than results obtained from the custom built instrument across the range of relative humidity from 2% RH to 50% RH. This is due to the selection of smooth, single particle contact sites in the commercial AFM experiments. The measured adhesion forces from the custom-built instrument were found to be significantly lower than predictions for adhesion from the contact mechanics theories of JKR and DMT. This can be attributed to the effect of surface roughness and multiple contacts, which are not taken into account in either the JKR or DMT contact mechanics theories. At humidites below 60% the results obtained from the commercial AFM are in much better agreement with the predicted pull-off forces from the JKR model, because smooth, single particle contact regions could be selected. Using the custom-built instrument and the AFM Explorer, the effect of applied load on the adhesion force between a polystyrene particle and a polystyrene substrate was studied at low, medium and high relative humidity. Increasing the applied load has little effect on the measured adhesion forces at low and medium relative humidity but at high relative humidity of 60 to 65% RH, a transition was observed at an applied load of 1000 - 1200 nN. Above this transition the adhesion force increased steadily with applied load due to the yield stress of the material in the contact region being exceeded. The experimental values of applied load have been coupled with published values of Young's modulus, Poisson's ratio and hardness to predict the contact area from contact mechanics models of JKR and Maugis-Pollock. When coupled with the published value of yield stress for the material, the applied load for the onset of plastic flow is predicted. The value of 1508 nN predicted by the plasticity-based MP model agrees approximately with the observed transition in behaviour.
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Bahrami, Arash. "Nonlinear Dynamics of Tapping Mode Atomic Force Microscopy." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/39176.
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A mathematical model is developed to investigate the grazing dynamics of tapping mode atomic force microscopes (AFM) subjected to a base harmonic excitation. The nonlinear dynamics of the AFM microcantilever are studied in both of the monostable and bistable phases with the microcantilever tip being, respectively, located in the monostable and bistable regions of the static bifurcation diagram in the reference configuration. Free-vibration responses of the AFM probes, including the microcantilever natural frequencies and mode shapes, are determined. It is found that, for the parameters used in a practical operation of an AFM, the natural frequencies and mode shapes of the AFM microcantilever are almost the same as those of a free-end microcantilever with the same geometry and made of an identical material. A multimode Galerkin approximation is utilized to discretize the nonlinear partial-differential equation of motion and associated boundary conditions governing the cantilever response and obtain a set of nonlinearly coupled ordinary-differential equations (ODE) governing the time evolution of the system dynamics. The corresponding nonlinear ODE set is then solved using numerical integration schemes. A comprehensive numerical analysis is performed for a wide range of the excitation amplitude and frequency. The tip oscillations are examined using nonlinear dynamic tools through several examples. The non-smoothness in the tip/sample interaction model is treated rigorously. A higher-mode Galerkin analysis indicates that period doubling bifurcations and chaotic vibrations are possible in tapping mode microscopy for certain operating parameters. It is also found that a single-mode Galerkin approximation, which accurately predicts the tip nonlinear responses far from the sample, is not adequate for predicting all of the nonlinear phenomena exhibited by an AFM, such as grazing bifurcations, and leads to both quantitative and qualitative errors. A point-mass model is also developed based on the single-mode Galerkin procedure to compare with the present distributed-parameter model.
In addition, a reduced-order model based on a differential quadrature method (DQM) is employed to explore the dynamics of the AFM probe in the bistable phase where the multimode Galerkin procedure is computationally expensive. We found that the DQM with a few grid points accurately predicts the static bifurcation diagram. Moreover, we found that the DQM is capable of precise prediction of the lowest natural frequencies of the microcantilever with only a few grid points. For the higher natural frequencies, however, a large number of grid points is required. We also found that the natural frequencies and mode shapes of the microcantilever about non-contact equilibrium positions are almost the same as those of the free-end microcantilever. On the other hand, free-vibration responses of the microcantilever about contact equilibrium positions are quite different from those of the free-end microcantilever. Moreover, we used the DQM to discretize the partial-differential equation governing the microcantilever motion and a finite-difference method (FDM) to calculate limit-cycle responses of the AFM tip. It is shown that a combination of the DQM and FDM applied, respectively, to discretize the spatial and temporal derivatives provides an efficient, accurate procedure to address the complicated dynamic behavior exhibited by the AFM probe. The procedure was, therefore, utilized to study the response of the microcantilever to a base harmonic excitation through several numerical examples. We found that the dynamics of the AFM probe in the bistable region is totally different from those in the monostable region.Ph. D.
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Bickmore, Barry Robert. "Atomic Force Microscopy Study of Clay Mineral Dissolution." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/25984.
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An integrated program has been developed to explore the reactivity of 2:1 phyllosilicates (biotite and the clays montmorillonite, hectorite, and nontronite) with respect to acid dissolution using in situ atomic force microscopy (AFM). Three techniques are described which make it possible to fix these minerals and other small particles to a suitable substrate for examination in the fluid cell of the atomic force microscope. A suite of macros has also been developed for the Image SXM image analysis environment which make possible the accurate and consistent measurement of the dimensions of clay particles in a series of AFM images, so that dissolution rates can be measured during a fluid cell experiment. Particles of biotite and montmorillonite were dissolved, and their dissolution rates normalized to their reactive surface area, which corresponds to the area of their edge surfaces (Ae). The Ae-normalized rates for these minerals between pH 1-2 are all ~10E-8 mol/m2*s, and compare very well to other Ae-normalized dissolution rates in the literature. Differences between the Ae-normalized rates for biotite and the BET-normalized rates (derived from solution chemical studies) found in the literature can be easily explained in terms of the proportion of edge surface area and the formation of leached layers. However, the differences between the Ae-normalized montmorillonite rates and the literature values cannot be explained the same way. Rather, it is demonstrated that rates derived from solution studies of montmorillonite dissolution have been affected by the colloidal behavior of the mineral particles. Finally, the dissolution behavior of hectorite (a trioctahedral smectite) and nontronite ( a dioctahedral smectite) were compared. Based on the differential reactivity of their crystal faces, a model of their surface atomic structures is formulated using Hartman-Perdock crystal growth theory, which explains the observed data if it is assumed that the rate-determining step of the dissolution mechanism is the breaking of connecting bonds between the octahedral and tetrahedral sheets of the mineral structure.Ph. D.
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LAU, JOAN M. "IMAGING MEMBRANE PROTEINS USING ATOMIC FORCE MICROSCOPY TECHNIQUES." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1022192720.
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Dhanapala, Hembathanthirige Yasas. "Dielectric Constant Measurements Using Atomic Force Microscopy System." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1347907325.
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Tokumasu, Fuyuki. "DNA-Protein Interactions Studied by Atomic Force Microscopy." Kyoto University, 2000. http://hdl.handle.net/2433/181362.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第8094号
人博第80号
11||148(吉田南総合図書館)
新制||人||20(附属図書館)
UT51-2000-C44
京都大学大学院人間・環境学研究科人間・環境学専攻
(主査)教授 豊島 喜則, 教授 池永 満生, 教授 速水 正憲, 教授 竹安 邦夫
学位規則第4条第1項該当
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Li, Tai-De. "Atomic force microscopy study of nano-confined liquids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24674.
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Thesis (Ph.D.)--Physics, Georgia Institute of Technology, 2009.Committee Chair: Riedo, Elisa; Committee Member: Davidovic, Dragomir; Committee Member: Goldman, Daniel I.; Committee Member: Landman, Uzi; Committee Member: Lyon, L. Andrew
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Pulleine, Ellie Mui Mui. "Developing cell identification methods using atomic force microscopy." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8074/.
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This body of work describes the development of a non-invasive and label-free method for characterization of cell surface markers. The motivation for such a method is the ability to measure cells whilst maintaining function, minimizing contamination and disturbance but enabling downstream applications. The technique would impact on life sciences applications including; phenotype identification of both individual and populations of cells, dynamic measurement of cellular response and monitoring cell-microenvironment interactions. The method described centers on molecular recognition interactions which are associated with specific binding forces. These specific forces can be measured in a highly sensitive manner using force instruments. In this study atomic force microscopy (AFM) was employed because of its powerful capability of highly sensitive force measurement at a nanoscale spatial resolution. The objective to develop a force based method for characterization of cell surface molecules may be considered in more specific aims; the development of a functional AFM probe for identification of specific molecules and establishment of quantitative measurement of surface markers. The probe developed has a colloidal geometry which encourages multivalent binding due to greater contact areas, which can reveal presence on cells in just few measurements. On non-deformable surfaces few interactions occur and regular force increments and probability of unbinding indicate presence of target molecules. With multivalent interactions on deformable samples other variables of adhesion indicate identification of interactions; namely distance of total separation, total peaks of unbinding and energy for total separation. With these variables, the identity of HeLa and HFF1 cells was indicated by cluster of differentiation markers 24, 44 and 98 in a semi-quantitative manner. Additionally individual mesenchymal stems cells are identified by the presence of cluster of differentiation marker 90 and dynamic measurement of Human Leukocyte Antigen. Single-cell force spectroscopy was employed to investigate cellular binding to cancerous matrices to gain greater understanding of tumour angiogenesis. Total internal reflection fluorescence microscopy was employed to inform the experimental setting of contact area and sampling density. The method developed illustrates the potential of force based measurement for label-free, non-invasive measurements on cells. Further development and automation may allow the dynamic measurement of multiple markers. This would allow for a number of applications; the identification of true stem cell clones which is of great importance for stem cells therapies, for monitoring of differentiation, where both short and long term activations could be investigated.
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Huang, Peng. "Algorithmic approaches to high speed atomic force microscopy." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11019.
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Thesis (Ph.D.)--Boston UniversityThe atomic force microscope (AFM) has a unique set of capabilities for investigating biological systems, including sub-nanometer spatial resolution and the ability to image in liquid and to measure mechanical properties. Acquiring a high quality image, however, can take from minutes to hours. Despite this limited frame rate, researchers use the instrument to investigate dynamics via time-lapse imaging, driven by the need to understand biomolecular activities at the molecular level. Studies of processes such as DNA digestion with DNase, DNA-RNA polymerase binding and RNA transcription from DNA by RNA polymerase redefined the potential of AFM in biology. As a result of the need for better temporal resolution, advanced AFMs have been developed. The current state of the art in high-speed AFM (HS-AFM) for biological studies is an instrument developed by Toshio Ando at Kanazawa University in Japan. This instrument can achieve 12 frames/sec and has successfully visualized the motion of protein motors at the molecular level. This impressive instrument as well as other advanced AFMs, however, comes with tradeoffs that include a small scan size, limited imaging modes and very high cost. As a result, most AFM users still rely on standard commercial AFMs. The work in this thesis develops algorithmic approaches that can be implemented on existing instruments, from standard commercial systems to cutting edge HS-AFM units, to enhance their capabilities. There are four primary contributions in this thesis. The first is an analysis of the signals available in an AFM with respect to the information they carry and their suitability for imaging at different scan speeds. The next two are algorithmic approaches to HS-AFM that take advantage of these signals in different ways. The first algorithm involves a new sample profile estimator that yields accurate topology at speeds beyond the bandwidth of the limiting actuator. The second involves more efficient sampling, using the data in real time to steer the tip. Both algorithms yield at least an order of magnitude improvement in imaging rate but with different tradeoffs. The first operates beyond the bandwidth of the controller managing the tip-sample interaction and therefore the applied force is not well-regulated. The second keeps this control intact but is effective only on a limited set of samples, namely biopolymers or other string-like samples. Experiments on calibration samples and λ-DNA show that both of the algorithms improve the imaging rate by an order of magnitude. In the fourth contribution, extended applications of AFMs equipped with the algorithmic approaches are the tracking of a macromolecule moving along a string-like sample and a time optimal path for repetitive non-raster scans along string-like samples.
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BATTISTELLA, ALICE. "Atomic Force Microscopy-based essay for biomedical applications." Doctoral thesis, Università degli Studi di Trieste, 2021. http://hdl.handle.net/11368/2996075.
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The investigation of cellular mechanical properties for the evaluation of the cell physiological state
has emerged as a hot topic in the last decade. In this framework, different aspects of the mechanobiology are considered in three biomedical fields. First, the alteration of the mechanical phenotype, the cell structure and morphology of melanoma cells according to the levels of production of a factor involved in the cytoskeleton organization, are considered. Secondly, mechanotransduction, and more precisely the capability of cells to adapt their mechanics to the environmental condition was investigated on the effect of a heart failure on cardiac pericytes. In the last part, the mechanical properties of oocytes have been identified as a scoring system to evaluate the quality of oocytes to be selected for the practice of the in vitro fertilization. In particular, I investigated the evolution of the oocyte stiffness and viscosity during post-ovulatory ageing, one of the processes responsible for the decreased yields of in vitro fertilization. Here, two mechanical parameters were found, able to predict ageing status of the oocytes before any visual feature due to degradation. allowing to introduce a novel classification for pre-apoptotic and non-fertile oocytes.The investigation of cellular mechanical properties for the evaluation of the cell physiological state has emerged as a hot topic in the last decade. In this framework, different aspects of the mechanobiology are considered in three biomedical fields. First, the alteration of the mechanical phenotype, the cell structure and morphology of melanoma cells according to the levels of production of a factor involved in the cytoskeleton organization, are considered. Secondly, mechanotransduction, and more precisely the capability of cells to adapt their mechanics to the environmental condition was investigated on the effect of a heart failure on cardiac pericytes. In the last part, the mechanical properties of oocytes have been identified as a scoring system to evaluate the quality of oocytes to be selected for the practice of the in vitro fertilization. In particular, I investigated the evolution of the oocyte stiffness and viscosity during post-ovulatory ageing, one of the processes responsible for the decreased yields of in vitro fertilization. Here, two mechanical parameters were found, able to predict ageing status of the oocytes before any visual feature due to degradation. allowing to introduce a novel classification for pre-apoptotic and non-fertile oocytes.
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PUKHOVA, VALENTINA. "DYNAMIC ATOMIC FORCE MICROSCOPY RESOLVED BY WAVELET TRANSFORM." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/259234.
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Atomic Force Microscopy (AFM) is perhaps the most significant member of the scanning probe microscopes family and, because of its capability of working in air and liquid environments with virtually no limitations on imaging conditions and types of samples, it is definitely one of the most widely used. It has become an indispensable tool to measure mechanical properties at the nanoscale in various research contexts.
Scanning probes used in AFM are micromechanical oscillators (typically cantilevers) and the theory of AFM dynamics is based on the analysis of the oscillating modes of beam resonators or the simpler spring-mass model. Cantilevers can be driven by the thermal excitation and/or an external driver. Usually cantilevers are driven near resonances corresponding to flexural eigenmodes that can be described as damped harmonic oscillators. Advanced techniques consider multifrequency excitation or band excitation to broaden the measurable events in tip-sample interactions, thus expanding the variety of sample properties that can be accessed.
Multifrequency methods imply excitation and/or detection of several frequencies of the cantilever oscillations and concern the associated nonlinear cantilever dynamics. Such excitation/detection schemes provide higher resolution and sensitivity to materials properties such as the elastic constants and the sample chemical environment with lateral resolution in the nanometer range. In order to measure these parameters, information on peak force of interaction, energy dissipation and contact dynamics is required. Techniques to measure the parameters of the cantilever in the stationary regime are well established. In dynamics methods the external driver (thermal noise, piezoelectric driver, etc.) excites the cantilever and a number of techniques have been implemented to gain information from the tip-sample interactions, but usually the interaction of the tip with the surface is revealed by the modification of the average value of the amplitude, frequency or phase shift over many oscillation cycles. Reconstruction of the complete evolution of the interaction force between the tip and the sample surface during a single interaction event is not even considered.
As an alternative to these well established techniques and to push further the AFM possibilities, it is important to examine the possibility of analyzing single-event or impulsive interactions. This opens the possibility to capture the information conveyed by the sensing tip in a single interaction,
in contrast to the cycle average used in many dynamic techniques. The single-event interactions are basically of the impact kind, with the simultaneous excitation of many cantilever eigenmodes and/or harmonics. The averaging techniques provide superior sensibility, allowing to probe
the details of force interactions down to the molecular level, but to study single-event interactions it is mandatory to provide analysis techniques that are able to characterize all excited cantilever oscillation modes at once without averaging. The temporal evolution of the amplitude, phase and frequency during few oscillation cycles of the cantilever provides information that cannot be obtained with standard methods. In the present thesis a data analysis method allowing to retrieve these quantities during an impulsive cantilever excitation is proposed.
This thesis concentrates on the dynamics of the flexural modes of the thermally driven cantilever in air when its tip is excited by a single impact on the sample surface. The signal analysis is based on the combination of wavelet and Fourier transforms that can be applied to a broad class of
AFM impulsive measurements. To exemplify the method, a short time interval around the jump-to-contact (JTC) transition in ambient conditions is investigated, with the aim to characterize the transient excitation of the cantilever eigenmodes before and after the impact. The experimental evidences that high-order flexural modes are excited in air upon a single impact tip–sample interaction induced by the JTC transition are presented. The way to retrieve information about the instantaneous total force act ing on the cantilever tip, contact dynamics and energy dissipation at all frequencies simultaneously, without averaging or interruption, is developed. The exploration of these transient conditions of the cantilever is not possible with dynamic techniques based on the resonant driving or using Fourier transform analysis alone.
The analysis presented in this work is useful to deal with nonrepeatable experiments and to determine the exact single interaction dynamics in terms of the full cantilever spectral excitations, features that are not normally considered in dynamical AFM techniques.