Orientador: Monica Alonso Cotta / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-06T19:04:57Z (GMT). No. of bitstreams: 1 Moreau_AlbertoLuisDario_M.pdf: 5884680 bytes, checksum: 286ffec6c18e2e2bd91cb558260527eb (MD5) Previous issue date: 2005 / Resumo: Este trabalho teve como objetivo implementar a técnica de espectroscopia de força no Microscópio de Força Atômica (AFM) existente no LPD/IFGW/UNICAMP e aplicá-la ao estudo de pontas e amostras funcionalizadas com tiol (mercaptoundecanoic acid). Em particular, foi necessária uma caracterização minuciosa da ponta de AFM, utilizando imagens de microscopia eletrônica. Avaliamos a metalização da ponta com Au (necessária para a funcionalização), o raio da extremidade da ponta e as formas de aproximação da mesma em relação à amostra. Um estudo da constante de mola da alavanca onde se localiza a ponta foi realizado para obtermos valores das forças absolutas medidas. As medidas de força foram realizadas em atmosfera de N2 para evitarmos forças capilares embora também tenhamos realizado algumas medidas em meio ambiente. Variamos a técnica utilizada para a metalização da ponta (sputtering e deposição térmica), a concentração da solução tiol/etanol e os tempos de funcionalização das pontas e amostras. As medidas de força de adesão do tiol nos mostraram que a rugosidade da amostra interfere significativamente na área de contato entre ponta e amostra e conseqüentemente na dispersão nas forças. Apesar disso, nossos resultados forneceram valores de força de adesão e energia livre com a mesma ordem de grandeza que a literatura na área. Em paralelo, foram realizados testes de resistência e durabilidade com pontas de nanotubos de carbono, em colaboração com o Dr. Daniel Ugarte, além de imagens de AFM de amostras de DNA plasmídico, um possível candidato para futuros trabalhos com pontas funcionalizadas / Abstract: In this work we have implemented the force spectroscopy technique using the Atomic Force Microscopy (AFM) equipment at the LPD/IFGW/UNICAMP; this technique was applied to the study of functionalized tips and samples with thiol (mercaptoundecanoic acid). In particular, a detailed characterization of AFM tips with Electron Microscopy was carried out. We have studied the tip metalization with Au (necessary for functionalization), the tip radius and the several modes of tip-sample approximation. We have also studied models for the cantilever spring constant in order to evaluate the absolute force values. The force measurements were carried out in N2 atmosphere to prevent capillary forces, though we also carried out some measurements in laboratory atmosphere. Tip metalization techniques (sputtering and thermal deposition), the thiol/ethanol solution concentration and the functionalization times of tip and samples were varied in this work. The sample roughness can interfere in the contact area between tip and sample, and, thus on the thiol adhesion force measurements ¿ particularly on force values dispersion. In spite of that, our measurements provided values for the thiol adhesion forces and free energies in the same order of magnitude of the literature in the area. Parallel to this work, we have carried out resistance and durability tests with carbon nanotubes tips, in collaboration with Prof. Daniel Ugarte, as well as AFM images of plasmid DNA samples, a likely candidate for future work using funcionalized tips / Mestrado / Física / Mestre em Física

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / As propriedades mecÃnicas de cÃlulas vivas possuem um papel crucial no bom desempenho de suas funÃÃes fisiolÃgicas. PorÃm, nosso conhecimento nesse assunto ainda à limitado. NÃo à totalmente compreendido como uma cÃlula responde, estrutural e mecanicamente, a uma tensÃo externa ou como a elasticidade das cÃlulas altera-se em organismos doentes em comparaÃÃo a organismos sadios. Recentemente, a biomecÃnica de cÃlulas do cÃncer (em particular, a elasticidade ou rigidez) tem sido apontada como um fator importante que està relacionado à funÃÃo, adesÃo, motilidade, transformaÃÃo e invasÃo da cÃlula neoplÃsica. Estudos in vivo mostram que transformaÃÃes cancerosas introduzem alteraÃÃes significativas na estrutura e comportamento celular. Essas diferenÃas tambÃm podem causar alteraÃÃes nas propriedades mecÃnicas, geralmente levando a uma maior deformabilidade da cÃlula. A quantificaÃÃo da alteraÃÃo de elasticidade, utilizando ensaios mecÃnicos em conjunto com um exame microscÃpico, pode tornar-se um poderoso diagnÃstico do cÃncer e abrir caminhos para novos tratamentos. Neste contexto, a Microscopia de ForÃa AtÃmica (AFM) se apresenta como uma ferramenta ideal para a investigaÃÃo de cÃlulas por sua alta resoluÃÃo, capacidade de nano-manipulaÃÃo de superfÃcies, possibilidade de trabalhar em meios lÃquidos e por ser uma tÃcnica nÃo destrutiva. Neste trabalho, propÃe-se a investigaÃÃo da resposta mecÃnica de cÃlulas cancerÃgenas (linhagens A-498 e ACHN), comparando-se com cÃlulas normais (RC-124), utilizando-se um MicroscÃpio de ForÃa AtÃmica e seus componentes como ferramentas de caracterizaÃÃo morfolÃgica de alta resoluÃÃo e caracterizaÃÃo das propriedades mecÃnicas dessas cÃlulas. Utilizando a sonda de AFM como nano-indentador e a partir dos dados de forÃa obtidos pelo microscÃpio, analisados por meio de modelos teÃricos adequados, temos por objetivo obter valores qualitativos e quantitativos da resposta elÃstica dessas cÃlulas. / The mechanical properties of living cells have a crucial role in the accomplishment of their physiological functions. However, our knowledge on this subject is still limited. Is not fully understood how a cell responds structurally and mechanically to an external pressure or as the elasticity of cells is altered in diseased organisms compared to healthy ones. Recently, the biomechanics of cancer cells, in particular the elasticity or stiffness, has been identified as an important factor that is related to function, adhesion, motility, invasion and transformation of the neoplastic cells. Studies in vivo show that cancerous transformations introduce significant changes in the structure and behavior of cells. These differences can cause changes in mechanical properties, often leading to greater cell deformability. Quantifying the change of elasticity using mechanical tests in conjunction with a microscopic examination, can become a powerful method for the diagnosis of cancer, and open new routes for treatments. In this context, Atomic Force Microscopy (AFM) is presented as an ideal tool for cell research due to its high resolution capability for surface nano-manipulation, ability to work in fluids and for being a noninvasive and nondestructive technique. This study investigates the mechanical response of cancer cells (lines A-498 and ACHN), compared to normal cells (RC-124). Using an AFM and its components as a morphological tool of high resolution characterization and characterization of the cells mechanical properties using the AFM probe as a nano-indenter, and from the strength data obtained by the microscope, and appropriate theoretical models to interpret these data to obtain qualitative and quantitative values of the elastic response these cells.

Esta tese apresenta o estudo inédito da obtenção e caracterização de filmes finos de xiloglucanas obtidas de duas fontes diferentes, Hymenaea courbaril (HXG) e Tamarindus indica (TXG) sobre lâminas de Si/SiO2 e lâminas modificadas com grupos amino, assim como a aplicação desses filmes na imobilização da lectina concanavalina A (Con A) por medidas de elipsometria e microscopia de força atômica (AFM). A diferença na estrutura fina de cada XG influenciou na espessura e morfologia de seus filmes finos. Os oligômeros XXXXG presentes apenas na HXG favorecem as interações com a superfície, assim como já observado para interação entre XG-celulose [Lima e Buckeridge, 2001]. A imobilização de Con A foi realizada sobre filmes de carboximetilcelulose (CMC) de HXG, TXG e poli(metacrilato de metila) (PMMA), lâminas de Si/SiO2 e partículas poliméricas decoradas com polissacarídeo PMMA/CMC. A adsorção de Con A foi mais pronunciada sobre os filmes de CMC. As camadas de Con A formadas sobre HXG e TXG apresentam potencial utilização no reconhecimento e detecção de carboidratos para desenvolvimento de diagnósticos para algumas doenças, por não comprometerem o sítio de ligação específica da lectina na adsorção. No caso das partículas PMMA/CMC cobertas com uma camada de Con A, a alta estabilidade coloidal do sistema confere às partículas a possibilidade de explorar a propriedade de aglutinação específica da lectina no reconhecimento de carboidratos. A enzima hexoquinase (HK) foi imobilizada sobre dois diferentes tipos de partículas poliméricas decoradas com polissacarídeo, PMMA/CMC e poliestireno/quitosana (PS/CH). Na primeira, HK perdeu drasticamente sua atividade catalítica, ao contrário do observado quando a mesma enzima foi imobilizada sobre PS/CH, onde a HK manteve aproximadamente 50% de sua atividade enzimática, podendo ser armazenada em temperatura e pressão ambientes por 1 mês e ser reutilizada até 3 vezes. A estrutura da camada de hidratação e a composição química de cada um dos polissacarídeos (CMC ou CH) na superfície das partículas são diferentes, provocando diferenças na conformação das moléculas de HK quando imobilizadas sobre cada tipo de partícula. Medidas de forças de adesão utilizando as partículas poliméricas coladas na extremidade de cantilevers de AFM (Colloidal Probe Technique) permitiram medir as espessuras dessas camadas hidratadas de polissacarídeos nas superfícies das partículas PMMA/CMC e PS/CH, da ordem de (20 ± 10) nm e (35 ± 11) nm, respectivamente. Essas medidas de força também evidenciaram o potencial dos dois sistemas estudados (PMMA/CMC - Con A e PS/CH - HK) como métodos qualitativos para a detecção dos açúcares manose, glicose e frutose. / This thesis presents the study on thin film formation and characterization of xyloglucans extracted from two different sources, Hymenaea courbaril (HXG) and Tamarindus indica (TXG) onto Si/SiO2 wafers or amino-terminated wafers, as well as the application of these films as substrates for the immobilization of the lectin concanavalin A (Con A) by means of ellipsometry and atomic force microscopy (AFM). The difference in the fine structure of each XG exerted influence on film thickness and morphology. The oligomers XXXXG present only in HXG favor the interactions with the surfaces, as already observed for the interaction between XG-cellulose [Lima and Buckeridge, 2001]. Con A was immobilized onto films of carboxymethylcellulose (CMC), HXG, TXG and poly(methyl methacrylate) (PMMA), Si/SiO2 wafers and on polysaccharide decorated polymeric particles PMMA/CMC. The adsorption of Con A was more pronounced on CMC films. Con A layers formed on HXG and TXG present potential application in the recognition and detection of carbohydrates for diagnostic development, once the specific sugar binding site is not involved in the adsorption process. In the case of polymeric particles PMMA/CMC covered with a Con A layer, the high colloidal stability of the system confers to particles the possibility to explore the lectin property of specific agglutination with carbohydrates. The enzyme hexokinase (HK) was immobilized onto two different types of polysaccharide decorated polymeric particles, PMMA/CMC and polystyrene/chitosan (PS/CH). In the first one, HK drastically lost its catalytic activity. The same enzyme immobilized onto PS/CH kept approximately 50% of its enzymatic activity, even after storing under room temperature and pressure for 1 month. Moreover upon immobilizing HK could be reused up to 3 times. The structure of the hydration layer and the chemical composition due to the presence of each polysaccharide (CMC or CH) on the polymeric particle surface provided different environment, generating differences in the conformation of immobilized molecules of HK on each particle. Measurements of adhesion forces using the polymeric particles glued on the extremity of AFM cantilevers (Colloidal Probe Technique) allowed to measure the thicknesses of these hydrated polysaccharide layers on the surfaces of the PMMA/CMC and PS/CH particles as (20 ± 10) nm and (35 ± 11) nm, respectively. These force measurements had also evidenced the potential of the two studied systems (PMMA/CMC - Con A and PS/CH - HK) as qualitative methods for detection of the sugars mannose, glucose and fructose.

Esta tese aborda a aplicação de técnicas avançadas de processamento e análise de imagens em problemas originais envolvendo imagens de microscopia de força atômica. Para isso, foi desenvolvida uma série de algoritmos para a caracterização e o entendimento do processo de formação de novos materiais poliméricos com perspectivas de inúmeras aplicações tecnológicas. As análises envolveram a determinação da orientação da morfologia de substratos para alinhamento de cristais líquidos, contagem e estimativa dos raios de domínios em filmes automontados POMA/PVS, análise do aumento da fotoluminescência em filmes PPV e estudos da curvatura espontânea de macromoléculas de polímeros. Dentre os algoritmos principais podemos citar a determinação da inclinação dos autovalores da matriz de covariância das coordenadas dos pontos da forma, aplicação da técnica dos máximos regionais e diagramas de Voronoi, filtros passabanda 2D através da transformada de Fourier e extração da curvatura multiescala. A implementação destes algoritmos envolveu algoritmos básicos de análise de imagens tais como esqueletização, dilatações exatas e extração do contorno de formas. A principal contribuição deste trabalho foi a implementação do software denominado SPIA (Scanning Probe Image Analysis) que possui ferramentas para análise e processamento de imagens incluindo todas as que foram utilizadas no decorrer deste trabalho além de outras ferramentas. Este software foi desenvolvido em ambiente Delphi sob o paradigma da orientação a objetos para plataformas Windows NT/9X/2000/XP. Possui uma interface amigável e semelhante a outros softwares dedicados a processamento de imagens. Todas as técnicas aplicadas foram testadas extensivamente e os resultados que corroboram sua eficiência são mostrados ao longo da tese / This thesis address the application of advanced techniques of processing and analysisof images in original problems involving images of atomic force microscopy. For this, a series of algorithms for characterization and understanding of process of formation of new polymeric materials was developed and implemented, with perspectives of many technological applications. The analysis was applied to the determination of orientation of the morphology of substrates for alignment of liquid crystals, counting and estimative of radiuses of granules in layer-by-layer polymer films, analysis of enhancement of photoluminescence in PPV cast films, as well as the study of curvature spontaneous of macromolecules. The principal algorithms included are determination of inclination of eigenvectors of matrix of covariance of coordinates of points of shape,application of regional maxima technique and Voronoi diagrams, passband filters 2D through Fourier Transform and curvature multiscale. The implementation of these algorithms involved a series of image analysis algorithms such as squeletonization, exact dilations and extracting of contour of shapes. The principal contribution of this work was to develop a software called SPIA (Scanning Probe Image Analysis) that includes tools for analysis of processing of images including that were used in this work. This software was developed in Delphi under object orientation paradigm to Windows NT/9X/2000/XP. It has a friendly interface similar to other image processing softwares. All this techniques were tested extensively and the results that corroborate the robustness of the algorithms are included throughout the thesis

[pt] Nesta tese foi estudado o mecanismo de deformação mecânica de semicondutores III-V, em especial do InP, através da criação de defeitos utilizando um microscópio de força atômica e o indentador Triboscope. A liberdade de torção da ponta do AFM dificulta o controle e a reprodutibilidade dos experimentos de nanoindentação, por outro lado, através desta liberdade da técnica foi possível medir a pressão necessária para a criação das primeiras discordâncias no cristal. Foi realizado um estudo da deformação mecânica do óxido nativo presente na superfície do InP(100) e do GaAs(001) através de indentações utilizando o nanoindentador. Impressões plásticas residuais atribuídas à camada de óxido nativo foram observadas na superfície dos semicondutores. O processo de deformação plástica do InP foi estudado a partir de nanoindentações utilizando uma ponta Berkovich e uma ponta conosférica. O processo de deformação do InP com a ponta Berkovich apresenta descontinuidades para indentações realizadas com altas forças que são associadas a sucessivos escorregamentos de planos {111} seguidos de travamento das discordâncias. A distribuição de pressão na região indentada para a ponta conosférica é isotrópica, permitindo uma melhor visualização da transição elástico/plástico da deformação do material. Para essa ponta a deformação plástica do InP é iniciada com um evento catastrófico, que aparece nas curvas de indentação como uma descontinuidade. Foram observadas características ao redor das indentações, indicando o aparecimento de discordâncias na superfície do cristal. Microscopia eletrônica de transmissão foi utilizada para a observação das seções transversais das indentações que apresentaram alta densidade de discordâncias formadas pelos planos {111} escorregados. / [en] In this thesis, the mechanical deformation mechanism of semiconductors III-V was studied, especially for InP. Defects were produced by indentations using an atomic force microscope and a Triboscope nanoindenter. The AFM tip torsion during indentation difficult the control and the reproducibility of AFM nanoindentation experiments. Nevertheless, the tip torsion allowed the measurement of the materials Yield stress. A study of the mechanical deformation mechanism of the native oxide that is presented in the surface of InP (100) and GaAs (100) was done. The residual plastic impressions attributed to native oxides were observed on the semiconductors surface. The plastic deformation process of the InP was studied in nanoindentation experiments using a Berkovich and a conosferical tip. The InP deformation mechanism observed with a Berkovich tip presents discontinuities for indentations performed at high loads, that are associated with successive slip of {111} planes along the <110> directions. The pressure distribution on the indented region, applied by the conosferical tip, is isotropic allowing a better visualization of the elastic/plastic transition in a material deformation process. The plastic deformation of InP using this tip is initialized with a catastrophic event, that appears in the indentation curves as a discontinuity. Small cracks were observed around the indentations using both tips, suggesting that some dislocations loops ends on the InP surface. Bigger cracks were observed in indentations with the conosferical tip and they were attributed to material fracture produced by the locking of dislocations near the surface. Transmission electron microscopy was done in the nanoindentation cross section showing a high density of defects created by the slip of the {111} planes.

Les microscopes en champ proche sont très largement utilisés pour caractériser des propriétés physiques à l’échelle du nanomètre. Afin d’assurer la cohérence et l’exactitude des mesures dimensionnelles qu’ils retournent, ces microscopes ont besoin d’être étalonnés périodiquement. Le raccordement à la définition du mètre SI est assuré par le biais d’étalons de transfert dont les caractéristiques dimensionnelles sont étalonnées à l’aide d’un Microscope à Force Atomique métrologique (mAFM).Les travaux de thèse portent sur la contribution à la mise en place du Microscope à Force Atomique métrologique du LNE dans le but de caractériser et réduire l’incertitude de mesure. Une tête AFM passive thermiquement et spécifiquement conçue pour des applications de nanométrologie dimensionnelle a été développée et intégrée au mAFM. Elle comporte un système original pour mesurer les déflexions du levier nécessaire à la détection des forces s’exerçant à l’extrémité de la pointe. Il utilise une évolution de la méthode du levier optique qui permet de déporter les sources de chaleurs à l’extérieur de l’instrument. Pour cela, un nouveau capteur a été développé. Il est basé sur l’utilisation d’un bundle composé de 40 000 microfibres optiques structurées en quatre quadrants. Il remplace avantageusement une photodiode quatre quadrants et permet de transporter le signal lumineux jusqu’à des photodiodes placées à l’extérieur de l’instrument. Ce système a été modélisé, caractérisé et validé expérimentalement. La tête AFM ainsi développée est passive thermiquement. Sa conception repose sur la dissociation complète de la chaine métrologique, constituée en Zerodur, afin de lui conférer une excellente stabilité thermique et mécanique. Pour les mêmes raisons, le châssis de la tête qui supporte l’ensemble des composants et notamment le système de mesure des déflexions du levier est entièrement conçu en Invar. Cette tête repose sur une structure motorisée constituée de trois moteurs à reptation permettant l’approche de pointe mais également le réglage des interféromètres. Après intégration de la tête dans le mAFM, l’ensemble de l’instrument a été caractérisé afin d’établir son bilan d’incertitude. Plusieurs composantes ont ainsi été évaluées expérimentalement comme la non-linéarité et la stabilité de la mesure de position par interférométrie, les rotations parasites du scanner, les erreurs d’Abbe, les défauts de rugosité et de planéité des miroirs ainsi que les erreurs de bras mort. L’impact de chaque composante a été quantifié et listé dans le bilan d’incertitude. Ces travaux ont permis d’avoir une première estimation de l’incertitude de mesure du mAFM. / Scanning probe microscopes are very well used for characterization at the manometer scale. To ensure the measurement coherency and the accuracy of the results, those microscopes need to be periodically calibrated. It’s done thanks to reference standards whose dimensional characteristics are measured by a metrological atomic force microscope (mAFM) for example.The aim of this thesis work is the improvement of the metrological AFM of the LNE in order to reduce the measurement uncertainty. To reach this goal, a thermally passive AFM head has been developed and integrated on the instrument. It contains an original system to measure the cantilever deflexion and thus detect the force acting between the sample and the tip. This system is based on the optical beam deflection method but allow deporting the heat sources outside the instrument. To reach this goal, a new specific sensor has been developed. It is based on a four quadrant optic fibre bundle that contains 40 000 micro-fibre and which is ideal to replace the existing four quadrant photodiode and its conditioning electronic circuit with the bundle and its conditioning electronic circuit placed outside the instrument. This sensor has been modelled, and experimentally validated.The Developed AFM head which integrates the deflection measurement system is then thermally passive. Its design is based on the complete dissociation of the metrological loop and the structural loop. The metrological loop is made of Zerodur® in other to acquire an excellent mechanical and thermal stability and thus reduce the thermal dilatation. For the same reason, the AFM head support frame is fully made of Invar. The AFM head is placed on a motorized frame based on three piezo-leg motors (tripod) to make the tip/sample approach but also to set the interferometer signal quality. The interferometer signal is improved by combining the linear displacements of the three motors to generate small rotations. This allows setting the parallelism of the mirrors linked to the head with those linked to the translation stage.Once the AFM head integrated on the instrument, the assembly is characterized in order to establish the uncertainty budget. Different uncertainty components have been experimentally evaluated as for example: the interferometer non linearity, the drift of the XYZ position, the parasitic rotations of the translation stage, the Abbe error, the roughness and the flatness of the mirrors and the dead path errors. The impact of the each component has been quantified and listed in the uncertainty budget. This allowed getting a first estimation of the combined uncertainty of the instrument.

So-called, “Dynamic biomaterials” comprised of stimuli-responsive hydrogels are useful in a wide variety of biomedical applications including tissue engineering, drug delivery, and biomedical implants. More than 150,000 peer-reviewed articles (as of 2016) have been published on these materials, and more specifically, over 100,000 of these are on the most widely studied, poly(N-isopropylacrylamide). This thermoresponsive polymer in a crosslinked hydrogel network undergoes a large volume phase transition (𝑉/𝑉0 ~ 10 − 100) within a small temperature range (𝑇 ~ 1 − 3𝐾) making it particularly useful for tissue engineering applications because of the ability to control the topographical configuration of cells into tissue modules which can be applied in multiple layers to form three dimensional constructs. Nevertheless, applications with poly(N-isopropylacrylamide) hydrogels are hindered by two key obstacles: 1. there is presently no quantitative prediction of mechanical properties over the volume phase transition and 2. the mechanisms of cell attachment and detachment remain controversial and unclear. Current polymer-solution theory, first postulated by Paul Flory and Maurice Huggins in 1942, successfully predicts hydrogel swelling for non-stimuli-responsive polymers based on an empirically derived interaction parameter. However, for stimuli-responsive polymer hydrogels, this theoretical framework fails to quantitatively predict swelling and mechanical properties of the polymer. Currently, only qualitative agreement with experiment has been shown. Cell-cell and cell-matrix interactions are mediated through proteins collectively known as cell adhesion molecules. For cell-matrix interactions, these are generally the transmembrane protein, integrin, and the serum protein, fibronectin. It is widely accepted that nearly all molecular mechanisms of cell-matrix interactions are dependent on recognition of the peptide sequence Arg-Gly-Asp. However, much less is known about mechanical mechanisms involved in cell-cell and cell-matrix interactions. Obstacles to the advancement of these applications are 1) unclear mechanisms of cell release and 2) extended exposure of cells to hypothermic conditions. The author, in collaboration with others, has published work demonstrating reduced cell exposure to hypothermic conditions during tissue module release and elucidated a mechanism of tissue module release: mechanical strain. The central hypothesis of work in this proposal is that tissue module release occurs due to a mechanical strain-rate coinciding with critical force needed overcome the dynamic bond strength of cell adhesion molecules. Advances in this area could improve biomaterial design and accelerate the field of regenerative medicine by reducing or eliminating the need for allograft transplants. This dissertation project, then, seeks to address these two obstacles through biophysical characterization methods and analysis including: atomic force microscopy, scanning electron microscopy, laser-scanning confocal micrscopy, phase-contrast microscopy, and mass-balance analysis. It is hypothesized that, (1) mechanical properties of PNIPAAm hydrogels are quantitatively predicted based on crosslinker ratio in the water-rich phase, (2) release of cells from micropatterned PNIPAAm hydrogels occurs when the lateral strain in the surface exceeds ϵ > 0.25, and (3) the molecular mechanism of rapid cell release from micro-patterned PNIPAAm hydrogels is mediated by the transmembrance protein integrin and its extracellular matrix receptor, fibronectin. Results from these studies could be useful for improving the design of biomaterials based on PNIPAAm hydrogels for applications in tissue engineering.

The aim of this thesis is concerned with the influence of sliding velocity on capillary adhesion at the nanometer scale. In ambient conditions, capillary condensation which is a thermally activated process, allows the formation of a capillary meniscus at the interface between an atomic force microscope (AFM) probe and a substrate. This capillary meniscus leads to a capillary force that acts as an additional normal load on the tip, and affects the adhesion and friction forces. The Atomic Force Microscopy (AFM) offers interesting opportunities for the measurement of surface properties at the nanometer scale. Nevertheless, in the classical imaging mode, limitations are encountered that lead to a non stationary state. These limitations are overcome by implementing a new AFM mode (called Circular AFM mode). By employing the Circular AFM mode, the evolution of the adhesion force vs. the sliding velocity was investigated in ambient conditions on model hydrophilic and hydrophobic surfaces with different physical-chemical surface properties such as hydrophilicity. For hydrophobic surfaces, the adhesion forces or mainly van der Waals forces showed no velocity dependence, whereas, in the case of hydrophilic surfaces, adhesion forces, mainly due to capillary forces follow three regimes. From a threshold value of the sliding velocity, the adhesion forces start decreasing linearly with the logarithm increase of the sliding velocity and vanish at high sliding velocities. This decrease is also observed on a monoasperity contact between a atomically flat mica surface and a smooth probe, thus eliminating the possibility of the kinetics of the capillary condensation being related to a thermally activated nucleation process as usually assumed. Therefore, we propose a model based on a thermally activated growth process of a capillary meniscus, which perfectly explains the experimental results. Based on these results, we focused on directly investigating with the Circular mode the role of capillary adhesion in friction mechanisms. We investigated the influence of the sliding velocity on the friction coefficient, and a decrease following three regimes, similar to the sliding velocity dependence of the capillary adhesion, was observed for hydrophilic surfaces that possess a roughness higher than 0.1 nm. Whereas, an increase of the friction coefficient was observed on hydrophilic (Mica) or hydrophobic (HOPG) atomically flat surfaces that posses a roughness lower than 0.1 nm. However, in this latter case, the three regimes are not established. Finally, on a rough hydrophobic surface, the friction coefficient was sliding velocity independent. A direct comparison with capillary adhesion behavior with the sliding velocity is expected to give new insights to explain this interplay. / The aim of this thesis is concerned with the influence of sliding velocity on capillary adhesion at the nanometer scale. In ambient conditions, capillary condensation which is a thermally activated process, allows the formation of a capillary meniscus at the interface between an atomic force microscope (AFM) probe and a substrate. This capillary meniscus leads to a capillary force that acts as an additional normal load on the tip, and affects the adhesion and friction forces. The Atomic Force Microscopy (AFM) offers interesting opportunities for the measurement of surface properties at the nanometer scale. Nevertheless, in the classical imaging mode, limitations are encountered that lead to a non stationary state. These limitations are overcome by implementing a new AFM mode (called Circular AFM mode). By employing the Circular AFM mode, the evolution of the adhesion force vs. the sliding velocity was investigated in ambient conditions on model hydrophilic and hydrophobic surfaces with different physical-chemical surface properties such as hydrophilicity. For hydrophobic surfaces, the adhesion forces or mainly van der Waals forces showed no velocity dependence, whereas, in the case of hydrophilic surfaces, adhesion forces, mainly due to capillary forces follow three regimes. From a threshold value of the sliding velocity, the adhesion forces start decreasing linearly with the logarithm increase of the sliding velocity and vanish at high sliding velocities. This decrease is also observed on a monoasperity contact between a atomically flat mica surface and a smooth probe, thus eliminating the possibility of the kinetics of the capillary condensation being related to a thermally activated nucleation process as usually assumed. Therefore, we propose a model based on a thermally activated growth process of a capillary meniscus, which perfectly explains the experimental results. Based on these results, we focused on directly investigating with the Circular mode the role of capillary adhesion in friction mechanisms. We investigated the influence of the sliding velocity on the friction coefficient, and a decrease following three regimes, similar to the sliding velocity dependence of the capillary adhesion, was observed for hydrophilic surfaces that possess a roughness higher than 0.1 nm. Whereas, an increase of the friction coefficient was observed on hydrophilic (Mica) or hydrophobic (HOPG) atomically flat surfaces that posses a roughness lower than 0.1 nm. However, in this latter case, the three regimes are not established. Finally, on a rough hydrophobic surface, the friction coefficient was sliding velocity independent. A direct comparison with capillary adhesion behavior with the sliding velocity is expected to give new insights to explain this interplay.

The methanol-to-olefins reaction is an important industrial process for the production of light olefins (C2-C4). Silicoaluminophosphates are the most common catalysts for this process with SAPO-34 (CHA), SAPO-18 (AEI) and their intergrowths being considered the most catalytically active and selective. Understanding the crystal growth of such materials is important for control of the structure and defect incorporation, which can have a large effect on the catalytic behaviour. In this thesis, the synthesis, characterisation, catalysis and crystal growth of such materials are investigated. A series of CHA/AEI intergrowth materials were synthesised by sequential increases in silicon content, where low silicon content led to formation of AEI and higher silicon content led to CHA and intergrowth formation. X-ray diffraction and MAS-NMR were used to quantify the amount of intergrowth and there was a strong correlation between both techniques. Atomic Force Microscopy (AFM) revealed the mechanism by which these intergrowth structures grow. There is competition at the surface between the spiral-growth and layer-growth mechanisms, which has a significant effect on the resulting intergrowth, as intergrowth formation is only permitted with a layer-growth mechanism. Intergrowth on screw dislocations is not allowed, and thus discrete blocks of pure-phase AEI or CHA form. These intergrowth materials were tested for their performance in the methanol-to-olefins reaction. With a higher level of silicon, the catalysts had a larger acid site density but equivalent acid strength. The conversion of methanol over the catalysts correlated with the acid site density, where a greater acid site density led to higher conversion and faster deactivation. The selectivity over time was similar for all catalysts, with a high selectivity to ethylene and propylene. However, at the same percentage conversion, the C2/C3 ratio showed a strong correlation to the cage shape. Catalysts with a higher ratio of AEI cages had a higher selectivity to C3 and C4 products than the other catalysts, owing to the larger size of the internal AEI cage compared to the CHA cage. The crystal growth mechanism on SAPO-18 was investigated in detail to interrogate the complex spiral pattern that forms on the surface. Spirals form in a triangular type pattern due to differences in growth rates in different crystallographic directions. Interlaced terraces were also present. The unit cell and the relative orientation of the AEI cages define the different growth rates. In-situ AFM was used to investigate the dissolution behaviour of SAPO-18 and SAPO-34. In both cases, dissolution occurred via classical step retreat. The similarity in the layer stacking in both materials led to equivalent structure dissolution in both cases. The 0.9 nm layers dissolved first to 0.7 nm (closed cages) then to 0.4 nm (unstable intermediates). Dissolution of SAPO-18 revealed unusual spiral dissolution pits near the core of the dislocations. CHA/AEI intergrowth materials were also prepared using a dual-template method, where two templates, morpholine for CHA and N,N-diisopropylethylamine for AEI, were combined during synthesis. The phase transition from CHA to AEI occurred at different molar ratios with different synthesis procedures. XRD modelling confirmed the synthesis of an intergrowth phase at a molar ratio of 70% morpholine and 30% DPEA. Changes in chemical shift in the 13C MAS-NMR were used to observe the different template interactions with the framework as the ratio of CHA and AEI cages changed.

Les propriétés mécaniques des objets complexes à l’échelle nanométrique constituent un enjeu majeur dans de nombreux domaines comme les nano-biotechnologies. La microscopie à force atomique (AFM) est l’outil idéal pour la mesure de force à cette échelle et permet de pratiquer des expériences d’indentation sur des objets nano et micrométriques isolées. Cette thèse de doctorat s’inscrit dans un contexte de développement d’un nano-objet à visée théranostique composé d’une coque polymère vitreuse contenant un coeur liquide fluoré. Les propriétés mécaniques de ces particules sont hautement mises à contribution, que ce soit pour le transport au sein d’un environnement biologique par voie intraveineuse ou pulmonaire, l’imagerie échographique ou encore la libération contrôlée d’un principe actif par ultrasons. La complexité de ces systèmes, aussi bien du fait de leur géométrie sphérique que de leur aspect composite, rend difficile l’appréciation de leurs propriétés mécaniques, et notamment de leur élasticité. En partant du constat que les objets composites présentent une élasticité variant avec la profondeur d’indentation, une méthode semi-analytique (CHIMER : Coated Half-space Indentation Model for Elastic Response) a été mise en oeuvre afin d’interpréter leur élasticité apparente. Afin de valider cette méthode, des films minces reposant sur des substrats de polydiméthylsiloxane (PDMS) ont été caractérisés par nanoindentation AFM. L'accord obtenu entre le modèle et les données expérimentales permet de comprendre et de prévoir le comportement élastique de films rigides reposant sur un substrat mou. Cette méthode a ensuite été utilisée pour interpréter l’élasticité apparente des capsules polymères. L’influence de l’épaisseur des capsules et de l’élasticité volumique des matériaux qui les composent a ainsi pu être mise en évidence. Cette méthode d’analyse originale a également permis de montrer l’effet de la température et de la fréquence sur l’élasticité apparente des capsules polymères contenant un coeur liquide fluoré. / The mechanical properties of complex objects at the nanometric scale are of great interest in many fields such as nanobiotechnology. Atomic Force Microscopy (AFM) is the ideal tool to measure forces at the nanometer scale and to perform indentation experiments onto isolated objects. This PhD work takes place in the context of the development of a nano-object intended to theranostic applications. These nanoparticules are composed of a glassy polymeric capsule containing a liquid fluorinated core. The mechanical properties of these capsules are fully deployed for the transportation in biological media as well as for the bouncing of ultrasound imaging and their localized destruction. The complexity of those systems, both in term of geometry and composite aspect, makes it difficult to assess their mechanical properties, in particular their elasticity. Giving the fact that composite objects show a variation of their elasticity according to the indentation depth, a semi-analytical method (CHIMER : Coated Half-space Indentation Model for Elastic Response) has been implemented to interpret the apparent elasticity of such system. In order to support this method, polydimethylsiloxane (PDMS) based bilayers have been investigated by AFM nanoindentation. A good agreement between the model and the experimental data has been found and the elastic behavior of a rigid film laid over a soft substrate has been well described at the nanometer scale. This model has also been used to investigate the apparent elasticity of polymeric capsules. The influence of the shell thickness and of the bulk elasticity of the polymer has been therefore shown. Moreover, this original approach has been used to describe the effects of temperature and frequency on the apparent elasticity of polymeric capsules filled with a fluorinated liquid core.