Dissertations / Theses on the topic 'Atomic force microscopy- Nanomaterials'
To see the other types of publications on this topic, follow the link: Atomic force microscopy- Nanomaterials.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Atomic force microscopy- Nanomaterials.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Kent, Ronald Douglas. "Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35632.
Full textAbstract:
Incorporation of silver nanoparticles (AgNPs) into an increasing number of consumer products has led to concern over the potential ecological impacts of their unintended release to the environment. Dissolution is an important environmental transformation that affects the form and concentration of AgNPs in natural waters; however, studies on AgNP dissolution kinetics are complicated by nanoparticle aggregation. Herein, nanosphere lithography (NSL) was used to fabricate uniform arrays of AgNPs immobilized on glass substrates. Nanoparticle immobilization enabled controlled evaluation of AgNP dissolution in an air-saturated phosphate buffer (pH 7, 25 °C) under variable NaCl concentrations in the absence of aggregation. Atomic force microscopy (AFM) was used to monitor changes in particle morphology and dissolution. Over the first day of exposure to ⠥10 mM NaCl, the in-plane AgNP shape changed from triangular to circular, the sidewalls steepened, and the height increased by 6-12 nm. Subsequently, particle height and in-plane radius decreased at a constant rate over a 2-week period. Dissolution rates varied linearly from 0.4 to 2.2 nm/d over the 10-550 mM NaCl concentration range tested. NaCl-catalyzed dissolution of AgNPs may play an important role in AgNP fate in saline waters and biological media. This study demonstrates the utility of NSL and AFM for the direct investigation of un-aggregated AgNP dissolution.Master of Science
2
Rupasinghe, R.-A. Thilini Perera. "Probing electrical and mechanical properties of nanoscale materials using atomic force microscopy." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2268.
Full textAbstract:
Studying physical properties of nanoscale materials has gained a significant attention owing to their applications in the fields such as electronics, medicine, pharmaceutical industry, and materials science. However, owing to size constraints, number of techniques that measures physical properties of materials at nanoscale with a high accuracy and sensitivity is limited. In this context, development of atomic force microscopy (AFM) based techniques to measure physical properties of nanomaterials has led to significant advancements across the disciplines including chemistry, engineering, biology, material science and physics. AFM has recently been utilized in the quantification of physical-chemical properties such as electrical, mechanical, magnetic, electrochemical, binding interaction and morphology, which are enormously important in establishing structure-property relationship.
The overarching objective of the investigations discussed here is to gain quantitative insights into the factors that control electrical and mechanical properties of nano-dimensional organic materials and thereby, potentially, establishing reliable structure-property relationships particularly for organic molecular solids which has not been explored enough. Such understanding is important in developing novel materials with controllable properties for molecular level device fabrication, material science applications and pharmaceutical materials with desirable mechanical stability. First, we have studied electrical properties of novel silver based organic complex in which, the directionality of coordination bonding in the context of crystal engineering has been used to achieve materials with structurally and electrically favorable arrangement of molecules for an enhanced electrical conductivity. This system have exhibited an exceptionally high conductivity compared to other silver based organic complexes available in literature. Further, an enhancement in conductivity was also observed herein, upon photodimerization and the development of such materials are important in nanoelecrtonics.
Next, mechanical properties of a wide variety of nanocrystals is discussed here. In particular, an inverse correlation between the Young’s modulus and atomic/molecular polarizability has been demonstrated for members of a series of macro- and nano-dimensional organic cocrystals composed of either resorcinol (res) or 4,6-di-X-res (X = Cl, Br, I) (as the template) and trans-1,2-bis(4-pyridyl)ethylene (4,4’-bpe) where cocrystals with highly-polarizable atoms result in softer solids. Moreover, similar correlation has been observed with a series of salicylic acid based cocrystals wherein, the cocrystal former was systematically modified. In order to understand the effect of preparation method towards the mechanical properties of nanocrystalline materials, herein we have studied mechanical properties of single component and two component nanocrystals. Similar mechanical properties have been observed with crystals despite their preparation methods. Furthermore, size dependent mechanical properties of active pharmaceutical ingredient, aspirin, has also been studied here. According to results reduction in size (from millimetre to nanometer) results in crystals that are approximately four fold softer.
Overall, work discussed here highlights the versatility of AFM as a reliable technique in the electrical, mechanical, and dimensional characterization of nanoscale materials with a high precision and thereby, gaining further understanding on factors that controls these processes at nanoscale.
3
Wood, Erin Leigh. "An Atomic Force Microscopy Nanoindentation Study of Size Effects in Face-Centered Cubic Metal and Bimetallic Nanowires." ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/260.
Full textAbstract:
The enhancement of strength of nanoscale materials such as face-centered cubic metal nanowires is well known and arises largely from processes mediated by high energy surface atoms. This leads to strong size effects in nanoscale plasticity; ,smaller is stronger. Yet, other factors, such as crystalline defects also contribute greatly to the mechanical properties. In particular, twin boundaries, which are pervasive and energetically favorable defects in face-centered cubic metal nanowires, have been shown to greatly enhance the strength, furthermore this increase in strength has been shown to be directly influenced by the twin density. However, attempts to control the introduction of beneficial defects remains challenging. Additionally, even minor local variations in the crystalline structure or size of metal nanowires may have drastic effects on the yielding of metal nanowires, which are difficult to measure through tensile and bending tests.
In this study, atomic force microscopy based nanoindentation techniques are used to measure the local plasticity of Ni-Au bimetallic as well as Cu and Ag metallic nanowires. In the first part of the thesis the hardness of bimetallic nanowires synthesized through template-assisted electrodeposition is measured and found to show significant size-effects. It was found that the nanoindentation hardness was governed by materials properties, the observed indentation size effects were dependent on geometrical factors.
The second part of this thesis presents a methodology to control the crystal structure of Ag and Cu nanowires through direct electrodeposition techniques, which were tested directly as grown on the substrate to limit effects of pre-straining. Ag nanowires showed marked size-effects as well as two distinct modes of deformation which we attribute to the defects that arise during crystalline growth. We also show control of the surface microstructure in Cu nanowires which leads to strengths that are more than doubled compared to single crystalline Cu nanowires. Finally, we present support from classic crystal growth theory to justify that the observed plasticity in Ag and Cu nanowires is largely dependent on defects that are nucleated through changes in the growth environment.
4
Becerril-Garcia, Hector Alejandro. "DNA-Templated Nanomaterials." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1823.pdf.
Full text
5
Martinez-Morales, Alfredo Adolfo. "Synthesis, characterization and applications of novel nanomaterial systems and semiconducting nanowires." Diss., [Riverside, Calif.] : University of California, Riverside, 2010. http://proquest.umi.com/pqdweb?index=0&did=2019838541&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1273864032&clientId=48051.
Full textAbstract:
Thesis (Ph. D.)--University of California, Riverside, 2010.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed May 14, 2010). Includes bibliographical references. Also issued in print.
6
Kent, Ronald Douglas. "Controlled Evaluation of Metal-Based Nanomaterial Transformations." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/74998.
Full textAbstract:
Metal-based nanoparticles (MNPs) are becoming increasingly common in commercial products. Release of these materials into the environment raises concerns about the potential risks they pose to aquatic life. Predicting these risks requires an understanding of MNPs' chemical transformations. In this study, arrays of immobilized MNPs fabricated by nanosphere lithography (NSL) were used to investigate environmental transformations of MNPs. Specifically, sulfidation of silver nanoparticles (Ag NPs) and dissolution of copper-based nanoparticles (Cu NPs) were investigated. Atomic force microscopy (AFM) and transmission electron microscopy were the primary analytical techniques for these investigations. Because the MNPs were immobilized on a solid surface, the samples were field deployable, environmentally relevant metal concentrations were maintained, and the confounding influence of MNP aggregation was eliminated. Ag NP samples were deployed in a full-scale wastewater treatment plant. Sulfidation occurred almost exclusively in anaerobic zones of the WWTP, where the initial sulfidation rate was 11-14 nm of Ag converted to Ag2S per day. Conversion to Ag2S was complete within 7-10 d. Dissolution rates of Cu-based NPs were measured in situ over a range of pH by flow-cell AFM. Based on the measured rates, CuO/Cu(OH)2 NPs dissolve completely within a matter of hours at any pH, metallic Cu NPs persist for a few hours to days, and CuxS NPs do not dissolve significantly over the time scales studied. Field deployment of samples in a freshwater stream confirmed these conclusions for a natural aquatic system. This research demonstrates that environmental transformations of MNPs will be a key factor in determining the ultimate form and concentration of NPs that aquatic organisms will be exposed to.Ph. D.
7
Colaço, Élodie. "Design and characterization of biomimetic biomineralized nanomaterials." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2529.
Full textAbstract:
La fabrication de composites constitués de collagène et d’hydroxyapatite a un grand intérêt dans la science des matériaux et la recherche biomédicale tout particulièrement pour des applications aux niveaux des tissus osseux. L’objectif est de synthétiser, à l’échelle nanométrique, un biomatériau à partir de ces 2 composantes d’une manière contrôlée dans le but de moduler ses propriétés physicochimiques, structurales et mécaniques. Ce projet de thèse met en évidence le rôle du collagène dans le mécanisme de minéralisation dans le but d’élaborer un nanomatériau biomimétique biomineralisé. Pour ce faire, plusieurs stratégies ont été mises en place: (i) assemblage de collagène et de cristaux d’hydroxyapatite préformés, (ii) minéralisation de l’hydroxyapatite par catalyse enzymatique (iii) élaboration de multicouches d’enzyme minéralisés par la méthode « couche-par-couche » dans un nanofilm ou nanotube en présence de collagène ou non. La caractérisation des différents matériaux nanostructurés minéralisés ainsi obtenus est réalisée par plusieurs techniques physicochimiques notamment la microscopie électronique à transmission (TEM) et à balayage (SEM), la microscopie à force atomique (AFM), la spectroscopie vibrationnelle (IR et Raman), le turbiscan, la microbalance à cristal de quartz (QCM-D) et la mesure de diffusion de la lumière (DLS)The design of a composite based on collagen and hydroxyapatite crystals attractes a great interest in materials science and biomedical research particularly for bone tissue applications. The objective is to synthesize, at the nanoscale, a biomaterial from these two components in a controlled conditions in order to modulate its physicochemical, structural and mechanical properties. This thesis project highlights the role of collagen in the mineralization mechanism with the aim of developing a biomimetic biomineralized nanomaterial. To this end, several strategies have been suggested: (i) assembly of collagen with preformed hydroxyapatite crystals, (ii) mineralization of hydroxyapatite by enzymatic catalysis (iii) elaboration of mineralized enzyme-based multilayers by the "layer-by-layer" strategy to form a nanofilm or nanotube in the presence of collagen or not. The characterization of the various mineralized nanostructured materials obtained is performed by several physicochemical techniques including transmission electron microscopy (TEM) and scanning electron microscopy (SEM), atomic force microscopy (AFM), vibrational spectroscopy (IR and Raman), turbiscan, quartz crystal microbalance (QCM-D) and light scattering measurement (DLS)
8
Iwasiewicz-Wabnig, Agnieszka. "Studies of carbon nanomaterials based on fullerenes and carbon nanotubes." Doctoral thesis, Umeå : Department of Physics, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1312.
Full text
9
Yu-Su, Sherryl Yao Sheiko Sergei. "Molecular visualization of polymer thin films by atomic force microscopy towards patterning and replication of soft nanostructures for nanomaterial design and construction /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2277.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Jun. 26, 2009). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Curriculum of Applied Sciences and Engineering." Discipline: Applied and Materials Sciences; Department/School: Applied and Materials Sciences.
10
Rasel, Md Alim Iftekhar. "Experimental exploration of boron nitride nanoparticle interaction with living cells." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/118067/1/Alim_Rasel_Thesis.pdf.
Full textAbstract:
There is a growing interest among researchers on the interaction of living systems and biomaterials from the perspective of advanced biomedical engineering applications. Nanomaterials are employed in different biological applications (biosensing, molecular imaging, delivering drug particles, anticancer therapy etc.) because of their noble properties. Recently, boron nitride (BN NP) have attracted significant interest due to its superior chemical, physical and thermal properties and have found practical applications in fields like industrial tool manufacturing, electrical devices, photocatalysis and lubrication. However, studies to assess boron nitride for biomedical applications have been largely limited.
This project aims at evaluating BN NP as a potential tool for advanced bioengineering applications. The study is conducted by focusing on four key aspects: nanomaterial characteristics, biocompatibility, uptake process and effect on biophysical properties. Simultaneously, Hydroxyapatite (HAP) was also assessed as a point of reference.
Both BN NP and HAP were characterised based on their size, shape, surface charge and porosity to quantify the physical parameters of materials that dictate cellular response to nano-sized materials. The cytotoxicity of BN NP was extensively studied by conducting a number of biological assays. Overall, BN NP was found to be biocompatible within certain concentration range (0-50 μg/ml). Once the biocompatibility of BN NP was established, focus was placed on studying the uptake process and adopted mechanism. Cells were sectioned into thin slides (80 nm) after being cultured with nanomaterials and later imaged using transmission electron microscopy (TEM). Nanomaterials were observed inside cell cytoplasm, which confirmed successful internalisation of BN NP by human cells. The uptake process was extensively studied by analysing the microscopic images in a time dependent manner. The uptake mechanism of both BN NP and HAP was observed to be endocytosis.
Finally, the effect of nanomaterial uptake on the biophysical properties of cells was investigated. While assessing nanomaterials, previous studies were largely limited to biological assay. However, in this study, it was hypothesised that, apart from biological consequences, nanomaterials uptake will also affect the physical properties of cells. Robust and accurate experimental techniques were developed to quantify the cell stiffness and adhesion property using Atomic force microscopy (AFM). The obtained results revealed increase in cell stiffness for BN NP treated cells (50 and 100μg/ml) and a significant decrease in adhesion property for HAP treated cells (100μg/ml). Together, these results demonstrated the effect of nanomaterial uptake on biophysical properties of cells and explained the underlying mechanism. This was an innovative way of studying the physical wellbeing of cells, which also contributed in the existing knowledge of nanomaterial toxicity.
In summary, BN NP was evaluated in this study through an organised approach considering a number of key aspects. Collectively, this research develops a better understanding of the interaction between BN NP and human cells in in vitro condition and establishes a primary framework for nanomaterial assessment for biomedical use. The results validate BN NP's potential as a suitable biomedical engineering tool and emphasises the need for more research efforts in this field.
11
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.
Full text
12
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.
Full textAbstract:
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.
13
Jeong, Younkoo. "HIGH SPEED ATOMIC FORCE MICROSCOPY." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236701109.
Full text
14
Soussou, Asma. "Etude des propriétés structurales, morphologiques et électrochimiques de couches minces de nanocomposites hybrides de type hydroxyde double lamellaire (HDL) / biomolécules : application aux biocapteurs de polyphénols." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0302/document.
Full textAbstract:
Les polyphénols sont des bioproduits générés par le métabolisme des végétaux. Récemment, ils ont attiré l’attention par leur impact potentiellement positif sur la santé, en grande partie lié à leur capacité antioxydante. Ils interviennent également dans les arômes de vin, café, thé… et intéressent donc l’industrie agroalimentaire. Le développement de biocapteurs adaptés à ces molécules est donc nécessaire, tout en respectant certains critères (simplicité d’utilisation, rapidité de la mesure, faible coût). Dans le cas des biocapteurs enzymatiques, l’étape déterminante est l'immobilisation de l’enzyme sur la surface du transducteur sans affecter ses performances.Dans cette thèse nous avons utilisé des matériaux de type « hydroxyde double lamellaires » (HDLs) comme matrice d’immobilisation de la tyrosinase, enzyme reconnaissant spécifiquement les polyphénols, afin de fonctionnaliser la surface d’électrodes d’or sérigraphiées. L’objectif était d’élaborer des microbiocapteurs pour détecter les polyphénols extraits du thé vert.Les HDLs ont été synthétisés par la méthode de coprécipitation directe, puis caractérisés par différentes méthodes physiques (spectroscopies Raman et infrarouge, diffraction des RX) afin de confirmer leur composition et de définir leur structure cristalline. Puis, des films minces bidimensionnels de HDL de différentes compositions ont été réalisés en faisant varier différents paramètres comme la nature du substrat, la concentration de la solution initiale de HDL et la méthode de dépôt (auto-assemblage « SAM » ou spin coating). L’étude morphologique de ces films a été réalisée par microscopie de force atomique (AFM) afin d’optimiser l’état de surface avant l’immobilisation de la tyrosinase. Le greffage de cette dernière a également été étudié par AFM. Enfin, une étude électrochimique (par voltammétrie cyclique et chronoampérométrie) nous a permis de déterminer les caractéristiques analytiques des microbiocapteurs ampérométriques ainsi élaborés. Les résultats ont montré que nos systèmes présentent une grande sensibilité aux polyphénols et sont capables de détecter ces molécules grâce à leur oxydation et aussi à la réduction des composés enzymatiquement générés par la réaction catalytique. Ils sont dynamiques dans une large gamme linéaire de détection (jusqu'à 1000 ng.mL-1) et peuvent également détecter des traces de polyphénols (de m’ordre de quelques pg.mL-1)Polyphenols are in abundance in diet, being present in various fruits or vegetables, but also in tea or wine. Their antioxidant properties attracted an increasing interest of different researchers in the field of medicine and food manufacturers. Consequently, very intensive studies have been conducted to develop efficient polyphenols biosensors, while respecting certain criteria (simplicity of use, speed of measurement, low cost). In the case of enzymatic biosensors, the decisive step is the immobilization of the enzyme on the transducer surface without affecting its performances.In this thesis, we used layered double hydroxides (LDHs) as a host matrix to immobilize tyrosinase, an enzyme recognizing specifically polyphenols, at the surface of screen printed gold electrodes. Polyphenols used to study the biosensors were extracted from green tea.LDHs nanosheets were prepared by the co-precipitation method. In a first step, their structural properties were characterized by X-ray powder diffraction, Raman and Infra-Red spectroscopies, confirming crystalline phase and chemical composition of LDHs. In a second step, LDHs-thin films were prepared by self-assembly and spin coating deposition under various experimental conditions (nature and concentration of LDHs …), and studied by Atomic Force Microscopy (AFM) to obtain information about the surface morphology of the host matrix before enzyme immobilization. The presence of tyrosinase after the immobilization step was also confirmed by AFM. Electrochemical characteristics of the amperometric biosensors, whose design is based on this study, were determined by cyclic voltammetry and chronoamperometry. This study showed that these systems are highly sensitive to polyphenols, detecting them by their oxidation but also by the reduction of compounds enzymatically generated. They exhibit also other very attractive characteristics for the detection of complex mixture of polyphenols: a large dynamic range (up to 1000 ng.mL-1)and a very low detection limit (few pg.mL-1)
15
Muys, James Johan. "Cellular Analysis by Atomic Force Microscopy." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1158.
Full textAbstract:
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.
16
Konopinski, D. I. "Forensic applications of atomic force microscopy." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1402411/.
Full textAbstract:
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.
17
Acosta, Mejia Juan Camilo. "Atomic force microscopy based micro/nanomanipulation." Paris 6, 2011. http://www.theses.fr/2011PA066691.
Full textAbstract:
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
18
Sykulska-Lawrence, Hanna Maria. "Atomic force microscopy for Martian investigations." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4396.
Full textAbstract:
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.
19
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.
Full textAbstract:
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.
20
Anderson, Evan V. "Atomic Force Microscopy: Lateral-Force Calibration and Force-Curve Analysis." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/337.
Full textAbstract:
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.
21
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.
Full textAbstract:
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.
22
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.
Full text
23
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.
Full text
24
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.
Full textAbstract:
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.
25
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.
Full textAbstract:
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.
26
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.
Full text
27
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.
Full textAbstract:
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.
28
Sapcharoenkun, Chaweewan. "Controlled nanostructure fabrication using atomic force microscopy." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7593.
Full textAbstract:
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.
29
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.
Full text
30
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.
Full textAbstract:
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.
31
Yeo, Yee 1977. "Image processing for precision atomic force microscopy." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88854.
Full text
32
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.
Full text
33
Sun, Mingzhai. "Cell mechanics studied using atomic force microscopy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5499.
Full textAbstract:
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.
34
Dudda, Bruna. "Morphology of leds by atomic force microscopy." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6647/.
Full textAbstract:
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.
35
Barker, Emily Clare. "Characterisation of Gelation by Atomic Force Microscopy." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/85526.
Full textAbstract:
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.
36
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.
Full textAbstract:
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.
37
Clarke, Richard John. "Hydrodynamics of the atomic force microscope." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/10649/.
Full textAbstract:
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.
38
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.
Full text
39
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.
Full text
40
Gießibl, Franz J. [Verfasser]. "Progress in atomic force microscopy / Franz J. Gießibl." Augsburg : Universität Augsburg, 2007. http://d-nb.info/1077692749/34.
Full text
41
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.
Full text
42
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.
Full textAbstract:
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
43
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.
Full text
44
Sedman, Victoria L. "Atomic force microscopy investigations of peptide self-assembly." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10297/.
Full textAbstract:
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.
45
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.
Full text
46
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.
Full text
47
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.
Full text
48
Glynos, Emmanouil. "Atomic force microscopy on self-assembled polymer structures." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/13925.
Full textAbstract:
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.
49
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.
Full text
50
Looi, Lisa. "Interaction between polystyrene spheres by atomic force microscopy." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844419/.
Full textAbstract:
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.