Dissertations / Theses on the topic 'Interface Force'

In atomic force microscopy (AFM) a cantilever, with a sharp tip attached to its free end, is scanned over a surface. Forces from the surface aect the tip causing cantilever deection, which is registered by a detector. This information is then used to create a topographical image of the surface on nanoscale. We were a part of a project that developed a new type of AFM, namely intermodulation atomic force microscopy (IMAFM). It is based on dynamic AFM, but instead of one drive frequency, two or more frequencies are used. This generates more information from the sample. Our part in this project was to improve the software already in use. This will facilitate future simulations and experiments; and also utilize the available information in a new way.
Vid atomic force microscopy (AFM) fors en skarp spets, placerad pa den fria anden av en kantilever, over en yta. Krafterna fran ytan pa spetsen orsakar avvikelser i kantileverns beteende, vilket registreras av en detektor. Denna information utnyttjas sedan for att skapa en topogrask bild av ytan i nanoskala. Vi var involverarde i ett projekt dar det utvecklas en ny typ av AFM, intermodulation atomic force microscopy (IMAFM). Denna grundar sig pa dynamisk AFM, men istallet for en drivfrekvens utnyttjas tva eller era. Vilket i sin tur genererar mer information fran samma matning. Var uppgift i projektet var att utveckla mjukvaran som anvands vid experimenten. Detta for att underlatta framtida experiment samt utnyttja den tillgangliga informationen pa ett nytt satt.

In the first part of this study, frictional and normal forces in aqueous solutions were measured between a glass particle and oligopeptide films grafted from a glass plate. Homopeptide molecules consisting of 11 monomers of different amino acids were each "grafted from" an oxidized silicon wafer using microwave-assisted solid phase peptide synthesis. Oligopeptides increased the magnitude of friction compared to a bare hydrophilic silicon wafer. Friction was a strong function of the nature of the monomer unit and was lower for hydrophilic films. There was a strong adhesion and therefore friction between surfaces of opposite charges. Changes in adhesion and friction depended on the hydrophobicity and electrostatic forces: hydrophobic films and oppositely charged films produced high friction, whereas hydrophilic and like-charges produced low friction. Friction was lower in phosphate buffered saline than in pure water due to the screening of the double layer attraction for oppositely charged surfaces and additional lubrication by hydrated salt ions. We also investigated antimicrobial action of poly (allyl amine) (PA) when covalently bonded to glass. Glass surfaces were prepared by a two-step procedure where the glass was first functionalized with epoxide groups using 3-glycidoxypropyltrimethoxy silane (GOPTS) and then exposed to PA to bind via reaction of a fraction of its amine groups. Antibacterial properties of these coatings were evaluated by spraying aqueous suspensions of bacteria on the functionalized glass slides, incubating them under agar, and counting the number of surviving cell colonies. The PA film displayed strong anti-microbial activity against both Gram-positive and Gram-negative bacteria. Films that were prepared by allowing the PA to self assemble onto the solid via electrostatic interactions were ineffective antimicrobials. Such films had an insufficient positive charge and did not extend far from the solid. Thus we found that antimicrobial activity was correlated with a combination of the ability of the polymer chain to extend into solution and a positive surface potential.
Ph. D.

Inorganic-polymer hybrid materials have a high potential to enable major advances in material performance in a wide range of applications. This research focuses on characterizing and tailoring the physics and chemistry of inorganic-polymer interfaces in fabricating high-performance zeolite-polymer mixed-matrix membranes for energy-efficient gas separations. In addition, the topic of novel metal nanoparticle-coated polymer microspheres for optical applications is treated in the Appendix. In zeolite/polymer mixed-matrix membranes, interfacial adhesion and interactions between dope components (zeolite, polymer and solution) play a crucial role in determining interfacial morphology and particle dispersion. The overarching goal is to develop accurate and robust tools for evaluating adhesion and interactions at zeolite-polymer and zeolite-zeolite interfaces in mixed-matrix membrane systems. This knowledge will be used ultimately for selecting proper materials and predicting their performance. This project has two specific goals: (1) development of an AFM methodology for characterizing interfacial interactions and (2) characterization of the mechanical, thermal, and structural properties of zeolite-polymer composites and their correlation to the zeolite-polymer interface and membrane performance. The research successfully developed an AFM methodology to determine interfacial interactions, and these were shown to correlate well with polymer composite properties. The medium effect on interactions between components was studied. We found that the interactions between two hydrophilic silica surfaces in pure liquid (water or NMP) were described qualitatively by the DLVO theory. However, the interactions in NMP-water mixtures were shown to involve non-DLVO forces arising from bridging of NMP macroclusters on the hydrophilic silica surfaces. The mechanism by which nanostructured zeolite surfaces enhanced in zeolite-polymer interfacial adhesion was demonstrated to be reduced entropy penalties for polymer adsorption and increased contact area. ¡¡¡¡¡¡Metal nanoparticle (NP)-coated polymer microspheres have attracted intense interest due to diverse applications in medical imaging and biomolecular sensing. The goal of this project is to develop a facile preparation method of metal-coated polymer beads by controlling metal-polymer interactions. We developed and optimized a novel solvent-controlled, combined swelling-heteroaggregation (CSH) technique. The mechanism governing metal-polymer interaction in the fabrication was determined to be solvent-controlled heteroaggregation and entanglement of NPs with polymer, and the optical properties of the metal/polymer composite beads were shown to make them useful for scattering contrast agent for biomedical imaging and SERS (Surface-Enhanced Raman Scattering) substrates.

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2007.
Dr. J. David Frost, Committee Chair ; Dr. G. Wayne Clough, Committee Co-Chair ; Dr. William F. Marcuson III, Committee Member ; Dr. Paul W. Mayne, Committee Member ; Dr. Susan Burns, Committee Member.

This thesis presents the design and development of an electrochemical atomic force microscope (AFM) equipped with photothermal excitation for actuation of the cantilever for the study of the solid-liquid interface. A rigorous analysis of noise in the optical beam deflection method is presented and leads to innovative techniques for the reduction of the detection noise to levels well below the thermal noise of the cantilever. An AFM stochastic simulation demonstrates that thermal noise fundamentally limits the measurement of hydration structures at the mica-water interface, whereas tip-sample vibrations may dominate the measurement of the last two hydration layers above the surface. Commonly overlooked problems associated with the traditionally used piezoacoustic excitation are described and quantified with respect to the frequency-modulation (FM) and amplitude-modulation (AM) methods of dynamic AFM operation. After a description of the statistical mechanics of the electric double layer (EDL) of aqueous solutions, a three-dimensional atomic-resolution FM-AFM force spectroscopy experiment of the water-mica interface is presented alongside a detailed analysis of the damping and force profiles used for the determination of the absolute tip-sample distance by comparison to simulations. Lastly, the statistical mechanics of modern ionic liquid EDL electrochemistry are vulgarized, followed by a thorough investigation of cyclic voltammetry of 1-butyl-3-methylimidazolium hexafluorophosphate at the Au(111) interface with comparison to published electrochemical impedance spectroscopy results. The electrochemical observations are complemented by force spectroscopy measurements performed using AM-AFM at different electrode electrochemical potentials across a 2 V window - no relationship between potential and EDL structure was observed.
Cette thèse présente la conception et le développement d'un microscope électrochimique à force atomique (AFM) équipé d'excitation photothermique pour l'actionnement du levier pour l'étude de l'interface solide-liquide. Une analyse rigoureuse de bruit dans la méthode de déviation du faisceau optique est présentée et conduit à des nouvelles techniques pour la réduction du bruit de détection à des niveaux en dessous du bruit thermique du levier. Une simulation stochastique d'AFM démontre que le bruit thermique limite fondamentalement la mesure des structures d'hydratation à l'interface mica/eau, tandis que les vibrations méchaniques peuvent dominer la mesure des deux dernières couches d'hydratation au dessus de la surface. Des problèmes couramment négligés associés à l'excitation piezoacoustique traditionnellement utilisée sont décrits et quantifiés par rapport à la modulation de fréquence (FM) et à la modulation d'amplitude (AM) des méthodes de l'AFM en mode dynamique. Après une description de la mécanique statistique de la double couche électrique (EDL) de solutions aqueuses, des measures de spectroscopie de force de l'interface mica-eau acquises en mode FM-AFM en trois dimensions sont présentées à côté d'une analyse détaillée des profils d'amortissement et de la force utilisée pour la détermination d'une distance absolue entre la pointe et l'échantillon par comparaison à des simulations. Enfin, la mécanique statistique de l'électrochimie ionique moderne est vulgarisée, suivie d'une enquête approfondie de la voltampérométrie cyclique du 1-butyl-3-méthylimidazolium hexafluorophosphate près de l'interface du Au(111) avec comparaison avec les résultats publiés de spectroscopie d'impédance électrochimique. Les observations électrochimiques sont complétées par des mesures de spectroscopie de force réalisée à l'aide d'AM-AFM à différents potentiels électrochimiques d'électrodes à travers une fenêtre de 2 V - aucune relation entre la structure et le potentiel EDL n'a été observée.

The subject of diploma project is constructional solution of haptics interface construction for virtual reality output device. Construction is oriented only for virtual contact with objects. Force feedback on the user and deformation of objects are not used. Used programs: Autodesk INVENTOR 10, ANSYS WORKBENCH.

The purpose of this study was to quantify the contact forces between the lower and upper hands to the stick shaft during the ice hockey slap and wrist shot. Four cohorts (male/female x high/low calibre; HC, LC) of ice hockey players were tested using three sticks of different shaft bending stiffnesses (77, 87, 102). Forty-one subjects (21 male, 20 female) performed seven slap and seven wrist shots with each of the three stick types. Force at the stick-hand interface was recorded at 1000 Hz using 32 piezoresistive sensors about the shaft at the upper and lower-hand grip locations. The results demonstrated the feasibility for direct measurement of forces at the hand-stick interface while executing shooting tasks in ice hockey. As anticipated, peak forces acquired during both the slap and wrist shot differed by calibre and by gender, with males exhibiting higher forces than females, and HC players demonstrating higher forces than LC players, within each gender; however, stick type was not a significant factor. Notably, each player displayed unique, repeatable "force signatures". In general, for both slap and wrist shots, grip force patterns demonstrated typical bimanual coordination patterns pertinent to understanding the mechanical dynamic control of the stick for effective performance.
Le but de cette étude était d'examiner les forces de contact entre les mains et le baton de hockey pendant l'exécution de lancers frappés et de tirs du poignet. Quatre cohortes (homme/femme x haut / bas calibre; HC, LC) de joueurs de hockey sur glace ont été testés en utilisant trois bâtons de rigidités différentes (77, 87, 102). Quarante et un sujets (21 hommes, 20 femmes) ont effectué sept lancers frappés et sept tirs du poignet avec chacun des trois types de bâton. La force de pression a été enregistrée à 1000 Hz en utilisant 32 capteurs piézorésistifs aux interfaces entre la main et le bâton. Les résultats ont démontré la faisabilité de la mesure directe des forces à l'interface main-bâton lors de l'exécution de tirs au hockey sur glace. Les forces de pointe atteintes au cours de lancers frappés et de tirs du poignet différaient en fonction du calibre et du sexe, les hommes présentant des forces supérieures comparativement aux femmes. De plus, les joueurs de HC ont démontré des forces supérieures par rapport aux joueurs LC. Par contre, le type de bâton ne représentait pas un facteurs significatif pour la production de force qui plus est, chaque joueur a affiché une 'signature' de force reproductible et constante. En général, les modèles de forces pour les lancers frappés et les tirs des poignets ont démontré des pattrons de coordination bimanuelle à la compréhension du contrôle mécanique dynamique du bâton et possiblement a l'évaluation de la performance.

Ionic liquids (ILs) present new approaches for controlling interactions at the solid-liquid interface. ILs are defined as liquids consisting of bulky and asymmetric ions, with a melting point below 373 K. Owing to their amphiphilic character they are powerful solvents but also possess other interesting properties. For example, ILs can self-assemble and are attracted to surfaces due to their charged nature. As a result, they are capable of forming nanostructures both in bulk and at interfaces. This thesis describes how the solid-IL interface responds to external influences such as elevated temperatures, the addition of salt and polarisation. An improved understanding of how these factors govern the surface composition can provide tools for tuning systems to specific applications such as friction. Normal and friction forces are measured for ethylammonium nitrate (EAN) immersed between a mica surface and a silica probe, at different temperatures or salt concentrations. The results demonstrate that an increase in temperature or low concentrations of added salt only induce small changes in the interfacial structure and that the boundary layer properties remain intact. In contrast, at sufficiently large salt concentrations the smaller lithium ion prevails and the surface composition changes. The interfacial layer of a similar IL is also investigated upon the addition of salt and the results reveal that lithium ions affect the surface composition differently depending on the ion structure of the IL. This demonstrates that the surface selectivity strongly depends on the ion chemistry. Remarkably, a repulsive double layer force manifests itself for EAN at 393 K, which is not observed for lower temperatures. This indicates a temperature dependent change in EAN’s microscopic association behaviour and has general implications for how ILs are perceived. A new method is developed based on a quartz crystal microbalance to investigate how the surface compositions of ILs respond to polarisation. The approach demonstrates that interfacial layers of both a neat IL and an IL dissolved in oil can be controlled using potentials of different magnitudes and signs. Furthermore, the method enables two independent approaches for monitoring the charges during polarisation which can be used to quantify the surface composition. The technique also provides information on ion kinetics and surface selectivity. This work contributes to the fundamental understanding of the solid-IL interface and demonstrates that the surface composition of ILs can be controlled and monitored using different approaches.
Jonvätskor möjliggör nya tillvägagångssätt för att kontrollera interaktioner vid gränsskiktet mellan fasta ytor och vätskor. Jonvätskor definieras som vätskor som består av stora och asymmetriska joner med en smältpunkt under 373 K. På grund av sin amfifila karaktär är de starka lösningsmedel men har också andra intressanta egenskaper. Jonvätskor kan till exempel självorganisera sig och attraheras till ytor på grund av sin laddning. En följd av detta är att de bildar nanostrukturer både i bulk och på ytor. Denna avhandling beskriver hur gränsskiktet mellan fasta ytor och jonvätskor svarar på yttre påverkan såsom en ökning i temperatur, tillsättning av ett salt samt polarisering. En ökad förståelse för hur dessa faktorer styr ytkompositionen av jonvätskor kan bidra med verktyg för att kontrollera system till specifika applikationer såsom friktion. Normala- och friktionskrafter mäts för etylammonium nitrat (EAN) mellan en glimmeryta och en kolloidprob vid olika temperaturer eller saltkoncentrationer. Resultaten visar att en ökning av temperatur eller låga koncentrationer av tillsatt salt bara marginellt framkallar ändringar i strukturen på gränsytan och att det adsorberade lagret förblir intakt. När saltkoncentrationen emellertid var tillräckligt hög får den mindre litiumjonen överhanden och ytsammansättningen ändras. Ytlagret av en liknande jonvätska undersöks också vid tillsättning av salt och resultaten avslöjar att litiumjoner påverkar ytsammansättningen annorlunda beroende på jonstrukturen av jonvätskan. Detta visar att ytselektiviteten starkt beror på jonkemin. En repulsiv dubbellagerkraft yttrar sig anmärkningsvärt för EAN vid 393 K vilket inte observeras vid lägre temperaturer. Detta indikerar en ändring i EANs mikroskopiska sammansättningsbeteende och har generella återverkningar för hur jonvätskor uppfattas. En ny metod har utvecklats baserad på en kvartskristall mikrovåg för att undersöka hur ytsammansättningen av jonvätskor reagerar på polarisering. Denna metod visar att det adsorberade lagret av både en ren jonvätska och en jonvätska löst i olja kan kontrolleras genom att applicera spänningar med olika tecken och storlekar. Dessutom möjliggör metoden två oberoende tillvägagångssätt för att övervaka laddningarna under polarisering vilket kan användas för att kvantifiera ytsammansättningen. Tekniken ger också information om jonkinetik och ytselektivitet. Detta arbete bidrar till den grundläggande förståelsen av gränsskiktet mellan fasta ytor och jonvätskor och visar att ytsammansättningen av jonvätskor kan kontrolleras och övervakas med olika tillvägagångssätt.

QC 20160518

Ce travail de thèse est consacré à l’étude des déformations d’interfaces liquides par l’action d’une onde laser continue. Nous démontrons que la diffusion élastique d'une onde laser dans un milieu turbide induit une force diffusive en volume qui donne naissance à des écoulements permanents au sein du fluide. Les contraintes visqueuses associées à ces écoulements, à l’approche d’une interface liquide molle, peuvent engendrer la déformation de celle-ci jusqu’à la déstabiliser et former un jet. Dans ce manuscrit, nous présentons une étude expérimentale de ce nouveau couplage lumière-fluide complétée par des simulations numériques. Nous présentons également une étude des déformations et instabilité d'interfaces par la pression de radiation optique, due au contraste d’indice de réfraction entre les deux phases liquides en coexistence, dans des milieux transparents. Nous avons enfin analysé la combinaison de ces deux couplages dans les milieux turbides, force diffusive et pression de radiation participant différemment à la déformation d’interfaces liquides. Pour ce faire, nous avons eu recours à différents systèmes fluides turbides et transparents, ayant pour particularité principale de présenter une tension interfaciale extrêmement faible
This thesis work is dedicated to liquid interface deformations from a continuous laser wave. We demonstrate that elastic scattering of the incident wave in turbid medium induces a scattering force density giving birth to permanent bulk flows in the fluid. Near a soft interface, viscous stresses associated to these flows can deform the interface up to instability and produce a liquid jet. In this manuscript, we report an experimental study dedicated to this new light-fluid coupling in combination with numerical simulations. We also study interface deformations and instability induced by radiation pressure, due to refractive index contrast between the two liquid phases in coexistence, in transparent fluids. We finally analyzed the combination of both couplings in turbid media, scattering force and radiation pressure which differently operate for the interface deformation. To do this, we used different turbid and transparent fluids systems, which have the main particularity to present very low interfacial tension

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: purple membrane; photomechanics; photoinduced conformation change; photocycle; photoactive; photoinduced; bimetallic bending; bacteriorhodopsin; atomic force microscope; tip-sample interface; molecular conformation; PLDS; photoreactive; AFM. Includes bibliographical references (p. E-1-E-4).

As industry becomes increasingly reliant on robotic assistance and human-computer interfaces, the demand to understand the human sensorimotor system’s characteristics intensifies. Although this field of research has been going on for over a century, new technologies push the limits of the human motor system and our knowledge of it. With new technologies come new abilities, and, in the area of medical care and rehabilitation, the need to expand our knowledge of the sensorimotor system comes from both the patient and physician. Two studies relating to human force interaction are presented in this thesis. The first study focuses on humans’ ability to bimanually recreate forces. That is, to feel a force on one hand and reproduce that force on the other. This skill is applicable in everyday lives from tasks such as a gardener using shears to trim a bush to a surgeon tying a delicate suture. These two tasks illustrate the different factors in this study on force recreation, which are the effects of: (1) occupational force dexterity, (2) force magnitude, and (3) the number of fingers used in the recreation task. Results showed statistical significance for force magnitude and number of fingers as factors in bimanual force recreation but not for occupation. The second study examines how humans compensate for force perturbations in different directions with respect to the line of action and the effects of restricting movement time. A dynamic tracking task was presented to participants in which they were told to follow a moving target as accurately as possible. During a fixed interval along the target’s path, a force field would perturb them in an undisclosed direction. Nine force conditions and three speeds were tested on both the left and right hands. Statistical analyses and comparison of error data indicate an effect of force direction on compensation accuracy. Speed is demonstrated as a statistically significant factor on accuracy, and a linear relationship between speed and error is posited.

Virtual Reality is a powerful tool for training, simulation, and computer aided design. The sensation of being in a real environment, while interacting with VR simulation is usually referred as sense of presence or sense of immersion. In most of the current applications the focus has been in providing a good visual and sound feedback to the user. However, the lack of mechanoreception/touch and proprioception/force feedback, or in other words, the impossibility of really touching the virtual objects makes the interaction unreal and more difficult. The rapid advances in VR and the development of techniques such as virtual medicine, virtual training and virtual prototyping have highlighted the lack of an effective input/feedback interface in these technologies and this led to research activity in all aspects of input and feedback technology related to touch/force sensation and reflection. This work presents the development of a generic integrated haptic (touch/force) feedback interface for use in VR and telepresence applications. The interface presented here consists of a 7 DOF input control/force feedback exoskeleton and a multi-functional input control/touch feedback glove interface. The arm exoskeleton monitors the motions of the human arm and feed back force sensations using ultra light weight pneumatic Muscle Actuators (pMA) to obtain high power weight outputs in a light comfortable and inherently safe structure. The glove interface monitors the motions of the hand and feed back touch sensations such as contact pressure, surface texture and temperature. These hardware systems have been integrated together and have been interfaced with a virtual reality system to permit exploration and testing of interactions with virtual environments. It is believed that the use of the system in VR, particularly, in all design and rapid prototyping applications will provide enhanced performance and will augment the design-production process.

Ageing is linked to a decrease in mobility, which affects the quality of life of many elderly individuals. This is a growing challenge in industrialised societies since the proportion of elderly individuals is becoming larger. One potential solution that would keep these individuals active and independent is the use of mobility assist devices. These devices are designed to reduce the energy demand of the user with the use of electric motors providing torques at joints of the lower limb. Although promising, these devices have a problem: they become uncomfortable after prolonged usage. This is especially true for devices designed to produce substantial assistance. The research goal consisted of quantifying the performance of the physical interfaces, or points of attachments, of an experimental device with multiple interface adjustments. The device was fabricated with design criteria similar to active assist devices to simulate the mechanical behaviour of these particular devices. This analysis provided design recommendations that could ultimately enhance the performance of assist devices available on the market and thus the quality of life of many individuals. This research used force mapping and motion capture to quantify the kinetic and the kinematic compatibility of the device. Experimental results have shown that the position, shape and other parameters of the interfaces had an effect on the relative movement of the brace, or the brace performance. The device interface migration was greater when the interfaces were positioned furthest away form the joint. An increasing level of assistance showed more relative movement between the brace and the user. Interface geometry had a noticeable effect on force distribution over the interface. The results and methodology of this research offers an in depth understanding of the mechanical behavior of the physical interfaces of the developed assist device. Nevertheless, further research and development in the field of human machine interactions are needed in order to develop a physical human-machine interface that will ensure the success of powered assist devices in the future.

Automation in manufacturing has come far by using industrial robots. However, industrial robots require tremendous efforts in static calibration due to their lack of senses. Force and vision are the most useful sensing capabilities for a robot system operating in an unknown or uncalibrated environment [4]and by integrating sensors in real-time with industrial robot controllers, dynamic processes need far less calibration which leads to reduced lead time. By using robot systems which are more dynamic and can perform complex tasks with simple instructions, the production efficiency will rise and hence also the profit for companies using them.

Although much research has been presented within the research community, current industrial robot systems have very limited support for external sensor feedback, and the state-of-the-art robots today have generally no feedback loop that can handle external force- or position controlled feedback. Where it exists, feedback at the rate of 10 Hz is considered to berare and is far from real-time control.

A new system where the feedback control can be possible within a real-time behavior, developed at Lund Institute of Technology, has been implemented and deployed at Linköping Institute of Technology.

The new system for rapid feedback control is a highly complex system, possible to install in existing robot cells, and enables real-time (250 Hz) sensor feedback to the robot controller. However, the system is not yet fully developed, and a lot of issues need to be considered before it can reach the market in other than specific applications.

The implementation and deployment of the new interface at LiTH shows that the potential for this system is large, since it makes production with robots exceedingly flexible and dynamic, and the fact that the system works with real- time feedback makes industrial robots more useful in tasks for manufacturing.

La téléopération ouvre des possibilité nouvelles d'interaction avec le micro-monde. Avec des systèmes adaptés il devient possible de manipuler des éléments aux échelles microscopiques. L'ajout d'un retour haptique apporte une information supplémentaire nécessaire à une interaction naturelle. Cette thèse aborde la problématique de la conception d'une chaîne de téléopération haptique par la conception de ses éléments clefs. La première partie décrit l'optimisation de l'interface haptique à un degré de liberté haute fidelité issue des précédents travaux du laboratoire. Un premier travail augmente la précision des efforts produits. Cette amélioration est liée à une optimisation de la mesure de la vitesse de l'interface à des fréquences d’échantillonnage élevées. Un second point traite de la validation et quantification précise des forces de l'interface. La deuxième partie décrit deux nouveaux capteurs de force conçu spécifiquement pour les interactions avec le micro-monde. Ces fonctionnent sur le même principe de mesure par compensation. Deux approches sont suivies pour augmenter les fréquences des forces mesurable par le capteur. La première s'attache à réduire la masse en concevant un nouveau capteur à l'échelle micrométrique avec des technologies MEMS. Une deuxième approche modifie la conception du capteur et supprime la raideur dans le guidage. La troisième partie décrit la conception d'une nouvelle interface haptique à plusieurs degrés de liberté. Les éléments clefs de sa conception sont l'utilisation d'un palier à air, pour un guidage sans frottement, et de moteurs linéaires à induction, pour une inertie réduite
Teleoperation opens up new possibilities for interaction with the micro-world. Adequate systems make it possible for human to manipulate elements on microscopic scales. An added haptic feedback provides information crucial for a natural interaction. A bilateral coupling between the subsystems offers the best haptic transparency. This thesis addresses the design of a complete haptic teleoperation chain by focusing on its key elements. Three parts are detailed: The first part describes improvements of the high fidelity one degree of freedom haptic interface designed previously. First, the precision of the forces produced is improved. This improvement is related to the measurement of the motor velocity at high sampling frequencies. Then, the device is precisely caracterized. The second part describes the design of two new force sensors designed specifically for interactions with the micro-world. The forces are measured by compensation. Two approach are observed to expand the frequencies of forces measurable by the sensors. First approach try to reduce the mass, a new sensor on a micrometric scale is built with MEMS technologies. The second approach offer a new design of the sensor. In particular, the stiffness in the guidance is removed. The third part describes the design of a new haptic interface with multiple degrees of freedom. This interface combines the performances of the one degree of freedom interface with a 2D configuration. The key elements of its design are the an air bearing for frictionless guidance and linear induction motors for reduced inertia

The adsorbed layer morphology of a series of surfactants under different conditions has been examined primarily using atomic force microscopy (AFM). The morphologies of single and double chained quaternary ammonium surfactants adsorbed to mica have been characterised using AFM at concentrations below the cmc. Mixing these different types of surfactants systematically allowed a detailed examination of the change in adsorbed film curvature from the least curved bilayers through to most curved globules. From this study a novel mesh structure was discovered at curvatures intermediate to bilayers and rods. A mesh was again observed in studies examining the morphology change of adsorbed nonionic surfactant films on silica with variation in temperature. Other surfactant mixtures were also examined including grafting non-adsorbing nonionic surfactants and diblock copolymers into quaternary ammonium surfactant films of different morphologies.

The adsorbed layer morphology of a series of surfactants under different conditions has been examined primarily using atomic force microscopy (AFM). The morphologies of single and double chained quaternary ammonium surfactants adsorbed to mica have been characterised using AFM at concentrations below the cmc. Mixing these different types of surfactants systematically allowed a detailed examination of the change in adsorbed film curvature from the least curved bilayers through to most curved globules. From this study a novel mesh structure was discovered at curvatures intermediate to bilayers and rods. A mesh was again observed in studies examining the morphology change of adsorbed nonionic surfactant films on silica with variation in temperature. Other surfactant mixtures were also examined including grafting non-adsorbing nonionic surfactants and diblock copolymers into quaternary ammonium surfactant films of different morphologies.

Le champ de force CLAYFF est largement employé pour modéliser les interfaces de minéraux argileux – et minéraux apparentés – avec une phase aqueuse. Dans les simulations, les particules d’argile sont typiquement représentées par des feuillets semi-infinis, ainsi seules les surfaces parallèles au plan du feuillet (surfaces basales) sont considérées. Cette simplification est valable dans la mesure où ces surfaces sont majoritaires, mais les feuillets d’argile sont en réalité de taille nanométrique et terminés par des surfaces latérales, ou bordures. Ces surfaces peuvent non seulement adsorber les espèces en solution mais sont aussi sujettes aux transferts de proton, et tous les processus physico-chimiques liés à l’acidité de la phase aqueuse se produisent de façon prédominante au niveau des bordures. En ajoutant au champ de force CLAYFF un terme angulaire métal-O‑H dont les paramètres ont été correctement ajustés, les simulations réalistes des interfaces de bordure deviennent possibles.Les paramètres des termes Al-O‑H et Mg-O‑H ont été obtenus à partir de calculs DFT sur des modèles structuraux du bulk, de la surface basale et de la bordure de la gibbsite Al(OH)3 et de la brucite Mg(OH)2, dont les feuillets peuvent être considérés comme le squelette des minéraux argileux et apparentés. De plus, le terme Si-O‑H a été paramétré à partir d’un modèle de bordure de la kaolinite Al2Si2O5(OH)4. Les propriétés structurales et dynamiques issues de simulations de dynamique moléculaire DFT et classiques basées sur CLAYFF avec et sans terme métal-O‑H ont été comparées. Le champ de force modifié améliore nettement la description des surfaces hydroxylées : l'orientation et la dynamique librationnelle des groupes hydroxyles, les liaisons hydrogène dans lesquelles ils sont impliqués, et la coordination des atomes de métal appartenant aux bordures sont tous plus proches de la réalité
The CLAYFF force field is widely used to model the interfaces of clay minerals – and related layered materials – with an aqueous phase. In the simulations, clay particles are typically represented by semi-infinite layers, i.e. only surfaces parallel to the layer plane (basal surfaces) are considered. This simplification is acceptable to a certain extent, but clay layers are really nanosized and terminated by lateral surfaces or edges. These surfaces can not only adsorb solvated species but are also subject to proton transfers, and all physico-chemical processes related to the aqueous phase acidity predominantly occur at the edges. By adding to the CLAYFF force field a Metal-O‑H angle bending term whose parameters are correctly adjusted, the simulations of edge interfaces become possible.The parameters of Al-O‑H and Mg-O‑H terms were obtained from DFT calculations on bulk, basal surface and edge structural models of gibbsite Al(OH)3 and brucite Mg(OH)2, whose layers can be considered as the backbones of clay minerals and related materials. In addition, the Si-O‑H term was parametrized from an edge model of kaolinite Al2Si2O5(OH)4 . Molecular dynamics simulations based on DFT and on CLAYFF with and without Metal-O‑H term were performed. The modified force field clearly improves the description of hydroxylated surfaces : the orientation and the librational dynamics of the hydroxyl groups, the hydrogen bonding, and the coordination of metal atoms belonging to the edge are all closer to reality

About 90% of all chemicals are produced with the help of catalysts, substances with the ability to accelerate reactions without being consumed. Metal oxides play a prominent role in catalysis, since they are able to act reversibly in many chemical processes. Zink oxide (ZnO) is used to catalyse a number of industrially important reactions. For many of these reactions water is present as a reactant, product, or byproduct. The surface structure has a significant impact on the catalytic activity. However, currently, no experimental method simultaneously offers the spatial and temporal resolution to directly follow a catalytic process. This thesis explores surface structure dependent dynamical behavior for ZnO surfaces, nanoparticles, and water interfaces, using the computational chemistry method Molecular Dynamics, which enables detailed studies of structural and dynamical processes. Quantum mechanical (QM) calculations have been performed to obtain the energetics of the materials as a function of structure. This data has been used to parametrize reactive force-fields (ReaxFF), since the catalytic processes require both far larger and longer simulations than the capabilities of QM calculations on current computers. The simulations show that when steps are present on the surface, during crystal growth of ZnO, the creation of energetically favorable structures is accelerated. At the ZnO - water interface, structures that favor hydrogen bonding is promoted. At low, monolayer, coverage water adsorbs both molecularly and dissociatively, whereas at high coverage dissociated adsorption is favored. During evaporation from the monolayers, the ratio of dissociated and molecular water is preserved. Surface steps stabilizes the dissociated state as well as increases the rate of dissociation. The dynamical properties of ZnO nanoparticles were explored using Raman measurements and simulation. In both simulation and experiment certain vibrations were suppressed in the nanoparticles, compared to bulk. The simulations show that a narrow surface region lack the bulk-specific vibrations.

In the automotive industry, a kind of fuel additives, known as surfactant, is used to protect metallic surfaces. Its efficiency strongly depends on factors such as temperature, solvent properties and the presence of other surfactants in the system. In this thesis, both classical and ReaxFF molecular dynamics (MD) simulations are used in studying the impacts of these factors on the adsorption of organic surfactants at the fluid-solid interface. Firstly, a classical MD simulation study of competitive adsorption is carried out on a multi-functional phenol and amine surfactant model with ethanol at the oil/iron oxide interface. As the concentration of ethanol increases, the ethanol molecules effectively compete for the adsorption sites on the iron oxide surface. This observation concurs with the experimental findings of similar oil/iron oxide systems. Unlike most MD interfacial studies, ReaxFF MD uses a fully flexible and polarizable solid surface. The second part of the thesis includes a study on the effect of polarity of organic molecules on the structure of iron oxide using ReaxFF-based MD simulations. The simulation results suggest that care must be taken when parameterising empirical and transferable force fields because the fixed charges on a solid slab may not be a perfect representation of the real system, especially when the solid is in contact with polar compounds. Lastly, but not the least, missing ReaxFF interaction parameters for Fe/N have been developed to simulate the adsorption of amine based surfactant on iron oxide. The parameterisation of the force field is done by fitting these interaction parameters to a set of quantum mechanical data involving iron-based clusters. These newly developed parameters are able to capture chemisorption and proton transfer between hexadecylamine and iron oxide.

In individuals with diabetes mellitus, foot ulceration presents one of the most important risk factors in lower limb amputation. The investigation of foot ulceration is in-turn dependent on the study of plantar pressure and shear forces acting at the foot. The purpose of this study was to determine and assess the feasibility of the available methods and techniques to measure 'plantar pressure' and 'shear stresses' acting at the foot/shoe interface. From earlier studies using force-plate systems it can be concluded that the simultaneous measurement of 'shear stress' and 'pressure' is crucial in the diagnosis of plantar ulceration. However, methods to quantify both in conjunction with each other in an in-shoe situation are not well demonstrated. Investigations revealed various methods and processes to measure 'pressure' but on the other hand there seems to be a comparative lack in information of the procedures to 'measure shear stresses.

Esta tesis aborda la actividad biológica de la fibronectina (FN) como proteína de interfase en la interacción célula-material. La tesis investiga la respuesta de la proteína, en términos de cantidad adsorbida y conformación, ante diferentes propiedades físico-químicas del material. Además, se correlaciona la respuesta celular temprana y la funcionalidad celular con el estado de la proteína adsorbida sobre el material. Para ello se prepararon diferentes series de materiales con propiedades físico-químicas controladas. La distribución de FN sobre las diferentes superficies se caracterizó mediante el uso de la microscopía de fuerza atómica (AFM) y la densidad superficial adsorbida fue cuantificada mediante técnicas de marcado radioactivo y western blot. La respuesta celular se evaluó en términos de la adhesión inicial a las superficies, así como los procesos posteriores de diferenciación, proliferación, reorganización y producción de matriz extracelular. Se investigó el efecto de la nanotopografía en la adsorción de la FN y el comportamiento celular sobre una serie de topografías controladas en la escala nanométrica, obtenidas mediante el spin casting de soluciones de ácido poli(L-láctico)/poliestireno (PLLA/PS) de distintas concentraciones. La migración del PLLA hacia la superficie del film durante el proceso de spin coating proporciona superficies de PLLA con nanopicos de diferentes tamaños (14, 29 y 45 nm). El tamaño de la nanoestrutura afecta a la densidad de FN adsorbida, siendo mayor en la superficie de menor nanotopografía. En cuanto a la respuesta celular inicial, se observan adhesiones focales más desarrolladas y mejor reorganización celular de la capa de FN adsorbida en las superficies de mayor topografía (29 and 45 nm), lo que resulta en una mayor producción y organización de nueva matriz. Por otra parte se empleó una familia de materiales con sutiles variaciones en la composición química: polímeros acrílicos (polimetil, etil y butil acrilato -PMA, PEA y P
González García, C. (2012). BIOLOGICAL ACTIVITY OF FIBRONECTIN AT THE CELL-MATERIAL INTERFACE [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17701
Palancia

La mise en forme des zéolithes dans le domaine industriel est une chimie qui a été mise au point de manière empirique. De récentes études sur l’impact physico-chimique des liants sur les propriétés des zéolithes montrent qu’une étude rigoureuse et détaillée des processus se produisant lors de la mise en forme manque, et permettrait de mieux maîtriser sa mise en œuvre. A ce jour aucune étude ab initio n’a été menée sur ce sujet.Dans le travail proposé, la ZSM-5 (MFI) et l’effet du liant sur ses propriétés sont étudiés via l’utilisation de modèles quantiques (VASP DFT périodique) et de modèles de champs de force réactifs (ReaxFF). Un ensemble de modèles de la surface externe de la ZSM-5 a été construit, étudié (nature de la surface, hydratation, sites acides, …) et comparé à des données expérimentales (RMN du proton, FT-IR, adsorption de molécules sondes) de manière à pouvoir simuler ensuite mis au contact de liant et/ou composant du liant. Deux types de sites d’alumination de surface ont été mis en évidence, les hydroxyles pontant Al-OH-Si et de l’eau non dissociée sur la surface Al-(H2O)(OH)n. Grâce à la modélisation de l’adsorption de pyridine ou de diterbutylpyridine, l’acidité du premier type de sites a été montrée comme étant la plus forte et plus particulièrement aux localisations permettant un fort confinement. Le second type de sites a été montré comme étant le plus stable en surface et a fait le sujet d’études d’hydratation et de déshydratation. Les simulations des interactions avec les liants montrent que l’alumine a une forte interaction avec les zone riches en aluminium de la zéolithe et que le sodium issu de la silice empoisonne les sites acides des zéolithes. L’optimisation des paramètres du champ de force réactif et les simulations ont permis la modélisation à l’échelle adaptée de la mise en contact de surface de zéolithes avec des surfaces de liants. Les caractéristiques de la surface et les interactions avec le liant ont été mises en lien avec les expériences conduite à IFPEN, ce qui apporte un éclairage nouveau sur les phénomènes physico-chimiques se produisant lors de la mise en forme
Zeolites are nanoporous aluminosilicates crystals of prominent fundamental and industrial importance. Among these, ZSM-5 is one of the most investigated solid, with paramount industrial use, that can be obtained in various forms. Some of these (hierarchical forms, nanoslabs, nanosheets and nanocrystals) exhibit a very high surface over volume ratio which make them useful for multiple industrial processes. The shaping is used to adapt ZSM-5 (and zeolites in general) to the needs of the industrial reactors. Empirically, preparing a technical zeolite is a strong industrial know-how, but with limited physic-chemical understanding of the zeolite-binder interface. Periodic Density Functional Theory (DFT, VASP, PAW, PBE dDsC) calculations of the relative stability of relevant surface orientations for silicalite and ZSM-5 crystals ((100), (010) and (101)) were performed at different hydration levels thanks to ab initio thermodynamics. Their relative acidities (pyridine and di-tertbutylpyridine adsorption) and spectral features (vibration modes, NMR chemical shifts) are determined. The interaction of the most relevant ones with binders (alumina, silica) is simulated ab initio, and an empirical reactive force field (ReaxFF) is built on purpose to model larger scales. Several kinds of surface sites have been identified. Bridging Al-OH-Si are present at the pore mouth, of similar or higher stability with respect to bulk sites. These are not stable at the outermost surface, where the following groups prevail: Si-OH, Al-OH and most importantly water adsorbed on aluminum Al-(H2O)(OH)n. Models of pyridine and 2,6-ditertbutylpyridine adsorption show that the acidity of the bridging groups is stronger than the other, and more particularly with a strong confinement. Al-(H2O)(OH)n surface site are shown to be the most stable at the external surface of ZSM-5 and are studied upon the hydration and dehydration of the ZSM-5 external surfaces. The results issue from these DFT simulations are compared to FT-IR, 1H NMR, and pyridine/2,6-ditertbutylpyridine adsorption experiments conducted at IFPEN. The interaction between zeolite and binders (silica, alumina) is first modeled by the interaction of the zeolite with small components like Si(OH)4, Na+ - present in some silica sources - and Al(OH)3(H2O). The results show that alumina components are more strongly attracted by the aluminum of the zeolitic network than silicic species. Na+ binds more strongly with the zeolite rather than silica and these results are once more compared to experimental data. The reactive force field parameters optimization is allowing to model larger external zeolite surfaces that are in contact with more realistic binder surfaces. All these results provide a rational understanding of a large set of experimental observations from the literature, that remained so far poorly understood. These findings are likely not limited to the case of the MFI framework (some of them already appeared to be valid for zeolite Beta), as our conclusions are mainly dictated by local topology aspects. The zeolite we investigate and the reactive sites we reveal are of both fundamental and industrial importance

Vast improvements in robotics and wireless communication have made teleoperated robots significantly more prevalent in industry, defense, and research. To help bridge the gap for these robots in the workplace, there has been a tremendous increase in research toward the development of biomimetic robotic hands that can simulate human operators. However, current methods of control are limited in scope and do not adequately represent human muscle memory and skills. The vision of this thesis is to provide a pathway for overcoming these limitations and open an opportunity for development and implementation of a cost effective methodology towards controlling a robotic hand. The first chapter describes the experiments conducted using Flexpoint bend sensors in conjunction with a simple voltage divider to generate a cost-effective data glove that is significantly less expensive than the commercially available alternatives. The data glove was able to provide sensitivity of less than 0.1 degrees. The second chapter describes the molding process for embedding pressure sensors in silicone skin and data acquisition from them to control the robotic hand. The third chapter describes a method for parsing and observing the information from the data glove and translating the relevant control variables to the robotic hand. The fourth chapter focuses on the feasibility of the brain computer interfaces (BCI) and successfully demonstrates the implementation of a simple brain computer interface in controlling a robotic hand.
Master of Science

Neurological degenerative diseases like stroke, Alzheimer, Amyothrophic Lateral Sclerosis (ALS), Parkinson and many others are constantly increasing their incidence in the world health statistics as far as the mean age of the global population is getting higher and higher. This leads to a general need for effective, at-home and low-cost rehabilitative and health-daily-care tools. The latter should consist either of technological devices implemented for operating in a remote way, i.e. tele-medicine is quickly spreading around the world, or very-advanced computer-based and robotic systems to realize intense and repetitive trainings. This is the challenge in which Information and Communications Technology (ICT) is asked to play a major role in order to bring medicine to reach further advancements. Indeed, no way to cope with these issues is possible outside a strong and vivid cooperation among multi-disciplinary teams of clinicians, physicians, biologists, neuro-psychologists and engineers and without a resolute pushing towards a widespread inter-operability between Institutes, Hospitals and Universities all over the world, as recently highlighted during the main International conferences on ICT in healthcare. The establishment of well-defined standards for gathering and sharing data will then represent a key element to enhance the efficacy of the aforementioned collaborations. Among the others, stroke is one of the most common neurological pathologies being the second or third cause of mortality in the world; moreover, it causes more than sixty percent survivors remain with severe cognitive and motor impairments that impede them in living normal lives and require a twenty-four-hours daily care. As a consequence, on one side stroke survivors experience a frustrating condition of being completely dependent on other people even to perform simple daily actions like reach and grasp an object, hold a glass of water to drink it and so on. States, by their side, have to take into account additional costs to provide stroke patients and their families with appropriate cares and supports to cope with their needs. For this reason, more and more fundings are recently made available by means of grants, European and International projects, programs to exchange different expertise among various countries with the aim to study how to accelerate and make more effective the recovery process of chronic stroke patients. The global research about this topic is conducted on several parallel aspects: as regard as the basic knowledge of brain processes, neurophysiologists, biologists and engineers are particularly interested in an in-depth understanding of the so-called neuroplastic changes that brain daily operates in order to adapt individuals to life changes, experiences and to realize more extensively their own potentialities. Neuroplasticity is indeed the corner stone for most of the trainings nowadays adopted by the standard as well as the more innovative methods in the rehabilitative programs for post-stroke recovery. Specifically speaking, motor rehabilitation usually includes long term, repetitive and intense goal-directed exercises that promote neuroplastic mechanisms such as neural sprouting, synapto-genesis and dendritic branching. These processes are strictly related with motor improvements and their study could - one day - serve as prognostic measures of the recovery. Another aspect of this eld of neuroscience research is the number of applications that it makes feasible. One of the most exciting is to connect an injured brain to a computer or a robotic device in a Brain-Computer or Brain-Machine Interface (BCI or BMI) scheme aiming at bypassing the impairments of the patient and make him/her autonomously move again or train his/her motor abilities in a more effective way. This kind of research can already count an amount of literature that provides several proofs of concept that these heterogeneous systems constituted by humans and robots can work at the purpose. A particular application of BCI for restoring or enhancing, at least, the reaching abilities of chronic stroke survivors was implemented and is still currently being improved at I.R.C.C.S. San Camillo Hospital Foundation, an Institute for the rehabilitation from neurological diseases located in Lido of Venice and partially technically supported by the Department of Information Engineering of Padua in range of an agreement signed in 2009. This specific BCI platform allows patients to train and improve their reaching movements by means of a robotic arm that provides a force that helps patients in completing the training exercise, i.e. to hit a predetermined target. This force feedback is however subject to a strict condition: during the movement, the person has to produce the expected pattern of cerebral activity. Whenever this is accomplished, a force is delivered proportionally to the entity of the latter activity, otherwise the patient is obliged to operate without any help. In this way, this platform implements the so-called operant-learning, that is one of the most effective conditioning techniques to make a subject learn or re-learn a task. If, on one hand, the primary and explicit task is to improve a movement, on the other side the secondary but most important task is to deploy the perilesional part of the brain - still healthy - in becoming responsible for the control of the movement. It is a popular and widely-accepted opinion within the neuroscience community, indeed, that a healthy region of the sensorimotor area nearby the damaged one - which was previously in charge of performing the (reaching) movement - can optimally accomplish the impaired motor function substituting the original control area. Technically speaking, the main crucial feature that can ensure the effectiveness of the whole system is the precise and in real-time identification and quantification of the cerebral pattern associated with the movement, the worldwide named movement-related desynchronization (MRD). Starting from its original definition, passing through the most used techniques for its recognition, the thesis work presents a series of criticisms of the current signal processing method to detect the MRD and a complete analysis of the possible features that can better represent the movement condition and that can be more easily extracted during the on-line operations. Brain - it is well-known - learns by trials and errors and it needs a slightly-delayed (in the range of fraction of seconds) feedback of its performance to learn a task in the best way. This BCI application was born with the purpose to provide the above-mentioned feedback: however, this is only feasible if a computationally easy and contingent signal processing technique is available. This thesis work would like to cope with the lack of a well-planned real-time signal analysis in the current experimental protocol.
L'identificazione e la quantificazione in tempo reale dei correlati cerebrali del movimento e' uno degli aspetti piu' critici nell'ambito delle cosiddette Brain-Computer Interface (BCI), ovvero quelle applicazioni in cui un individuo, dopo uno specifico percorso di apprendimento, impara a controllare un computer (o un altro dispositivo) tramite la modulazione volontaria della sua attivita' cerebrale, con lo scopo finale di trarre vantaggio dall'utilizzo dell'apparecchiatura cosi' controllata. La BCI e' solo uno delle molteplici tecniche di riabilitazione motoria oggigiorno disponibili. Indipendentemente dalla specifica tecnica scelta, il metodo riabilitativo mira a recuperare le funzionalita' del cosiddetto sistema sensorimotorio, quel complesso di aree corticali e strutture sotto-corticali che permette ad un individuo di ricevere impulsi somatosensoriali dal mondo esterno, di elaborare la risposta motoria piu' opportuna e realizzarla grazie agli attuatori finali del movimento rappresentati dai muscoli. Per perseguire questo obbiettivo, la maggior parte delle tecniche riabilitative, ivi compresa la BCI, pongono grande attenzione alla promozione e sfruttamento di quei processi spontanei che il cervello costantemente impiega per svolgere le sue attivita', adattarsi a nuove condizioni ambientali e anche cercare di recuperare le abilita' perse a seguito di un evento dannoso quale un ictus. Questi fenomeni vengono generalmente riassunti nel termine neuroplasticita' e sono stati paradossalmente sfruttati per anni nella pratica clinica, ma solo recentemente sono diventati materia di rigorosi e approfonditi studi scientici portati avanti da neuroscienziati provenienti da ogni tipo di formazione (neurologi, neurofisiologi, biologi, ingegneri, neuropsicologi, ...). Nel particolare contesto della riabilitazione motoria che ambisce essenzialmente a promuovere fenomeni di (ri-)apprendimento motorio da parte del paziente colpito da ictus, la letteratura ha fermamente indicato il condizionamento operante come la strategia piu' efficace per favorire i processi di plasticita' corticale e, di conseguenza, il recupero, seppur parziale, della motricita'. Il condizionamento operante si applica tramite la ripetitiva associazione di un comportamento corretto (scorretto) effettuato dal soggetto e uno stimolo gratificante (penalizzante) dato contestualmente o in un tempo appena successivo all'esecuzione del comportamento. Sfruttando il fondamentale meccanismo di apprendimento del cervello per prove ed errori, esso impara a utilizzare il comportamento corretto per svolgere il compito richiesto. Tale comportamento corretto e', in questo caso, lo sfruttamento di risorse ridondanti prima dell'ictus ma ancora sane dopo l'evento per controllare le funzioni motorie rimaste indebolite o completamente perse a seguito del danno cerebrale. Data la fondamentale importanza della contingenza tra l'attivita' cerebrale del paziente coinvolto nell'esperimento e lo stimolo di feedback, un robusto algoritmo di elaborazione del segnale cerebrale si rende fortemente necessario. In questo lavoro di tesi e' stata analizzata una particolare applicazione BCI per la riabilitazione motoria di pazienti lievemente o moderatamente aetti da emiparesi dovuta a ictus e sono stati proposti degli algoritmi con la relativa soluzione software per la realizzazione ottimale della strategia di apprendimento operante durante il recupero di un movimento di raggiungimento. Il vincolo principale da considerare per ottenere questo tipo di risultato e' la possibilita' di identificare e quanticare il correlato neurofisiologico legato al movimento, la cosiddetta desincronizzazione movimento correlata, in tempo reale durante l'esecuzione del movimento da parte del soggetto. Nell'ottica del condizionamento operante, un dispositivo haptico inserito nel sistema funge da feedback positivo che aiuta il paziente a completare il movimento nel solo caso in cui venga riconosciuta la desincronizzazione. In caso contrario, il soggetto non riceve alcun feedback o il suo movimento viene reso piu' difficile. Dopo un primo capitolo introduttivo sul sistema sensorimotorio arricchito con alcune informazioni riguardanti la particolare patologia in questione, il secondo capitolo introduce gli elementi fondamentali della piattaforma sperimentale utilizzata, ovvero l'elettroencefalogramma (EEG) e la BCI nella sua accezione generale, accennando anche ai maggiori successi in questo ambito delle ICT applicate alla medicina riabilitativa. Nel capitolo 3 viene descritta la particolare piattaforma BCI basata su EEG menzionata sopra e nei capitoli 4 e 5 vengono presentate ampiamente le analisi, le procedure e i risultati sviluppati ed ottenuti in questi anni di studio. In particolare, nella prima parte del capitolo 4 viene illustrato l'algoritmo con cui e' possibile identificare e rimuovere in tempo reale un particolare evento di disturbo che puo' verificarsi durante la registrazione EEG, il cosiddetto artefatto electrode pop dovuto al temporaneo sollevamento di un elettrodo che causa abnormi valori negativi nelle tracce EEG. Una volta rimosso questo tipo di eventp, il segnale viene filtrato e nella seconda parte del capitolo 4 viene presentata un'esaustiva analisi dell'energia delle tracce EEG acquisite durante la registrazione dell'esperimento di cui sopra in soggetti sani di controllo e in alcuni pazienti reduci da ictus. Inoltre, viene suggerita una versione modificata del piu' noto metodo di quantificazione della desincronizzazione fornito da Pfurtscheller e colleghi a partire dagli anni '70 i cui risultati promettenti sono forniti e discussi nel capitolo finale della tesi. La tesi si conclude con una breve sezione dedicata alle prospettive future di applicazione della piattaforma con l'integrazione delle soluzioni software apportate da questa tesi e alle questioni ancora aperte da risolvere al fine di ottimizzare il sistema BCI in tutti i suoi aspetti in modo da realizzare nel modo piu efficace il condizionamento operante e promuovere quei processi spontanei che sottostanno al recupero funzionale della motricita'.

The effect of substrate surface treatment (substrate sputter cleaning) in a cathodic arc plasma prior to unbalanced magnetron deposition of transition metal nitride coatings on the performance of the coated components has been investigated. In particular the influence of parameters such as ion species, ion energy and exposure time on the changes in substrate surface topography, microstructure and micro-chemistry were studied employing transmission electron microscopy, energy dispersive X-ray analysis, electron energy loss spectroscopy, X-ray diffraction, atomic force microscopy and optical microscopy. The consequences for both the microstructure of subsequently grown transition metal nitride coatings and their adhesion were elucidated. The relevance for practical applications was demonstrated using the example of dry high-speed milling tests, which showed that an appropriate choice of substrate surface pre-treatment parameters can double the life time of the coated tools. This was found to be due to an improved adhesion as a result of a combina-tion of reduced oxygen incorporation at the interface between coating and substrate and local epitaxial growth of the coating. The latter is promoted by certain sub-strate surface pre-treatment procedures, which provide clean surfaces with preserved crystallographic order.

Mestrado emEngenharia Mecânica
In robotics, the teleoperation of biped humanoids is one of the most exciting topics. It has the possibility to bypass complex dynamic models with learning demonstration algorithms using human interaction. For this procedure, the Humanoid Project at the University of Aveiro - PHUA, ingrained in the production of a 27 degree-of-freedom full body humanoid platform teleoperated by means of haptic devices. The current project also comprises a robot model that has be imported into the Virtual Robot Experimentation Platform: V-REP. The usage of the simulator allows multiple exercises with greater speed and shorted setup times, when compared to the teleoperation of the real robot, besides providing more safety for the platform and the operator during the tests. By using the simulator, the user can perform tests and make achievements towards the reproduction of human movement with the interaction of two haptic devices providing force feedback to the operator. The performed maneuvers have their kinematic and dynamic data stored for later application in learning by demonstration algorithms. However, the production of more complex and detailed movements requires large amounts of motor skill from the operator. Due to the continuous change of users in the PHUA, an adaptation period is required for the newly arrived operators to develop an a nity with the complex control system. This work is focused on developing methodologies to lower the required time for the training process. Thanks to the versatility of customization provided by V-REP, it was possible to implement interfaces which utilized visual and haptic guidance to enhance the learning capabilities of the operator. A dedicate workstation, new formulations and support tools that control the simulation were developed in order to create a more intuitive control over the humanoid platform. Operators were instructed to reproduce complex 3D movements under several training conditions (with visual and haptic feedback, only haptic feedback, only visual feedback, with guidance tools and without guidance). Performance was measured in terms of speed, drift from intended trajectory, response to the drift and amplitude of the movement. Findings of this study indicate that, with the newly implemented mechanisms, operators are able to gain control over the humanoid platform within a relatively short period of training. Operators subjected to the guidance programs present an even shorter period of training needed, exhibiting high performance in the overall system. These facts support the role of haptic guidance in acquiring kinesthetic memory in high DOFs systems.
Em robótica, a teleoperação de robôs bípede humanóides é um dos tópicos mais emocionante. Tem a possibilidade de contornar modelos dinâmicos rígidos, com algoritmos de aprendizagem por demonstração utilizando interação humana. Para este procedimento, o Projeto Humanóide da Universidade de Aveiro - PHUA, empanha-se na produção de uma plataforma humanóide de corpo inteiro teleoperado com dispositivos hapticos. O estado presente do projeto apresenta um robô humanóide com 27 graus de liberdade. O projeto actual apresenta um modelo do robô importado para a Virtual Robot Exper- imentation Platform: V-REP. O uso do simulador permite vários exercícios com maior velocidade e tempos de preparação curtos, quando comparado com a teleoperação do robô real, além de proporcionar mais segurança para a plataforma e do operador durante os ensaios. Ao utilizar o simulador, o utilizador pode realizar testes à reprodução de movimento humano com a interacção de dois dispositivos de meios hápticos que fornecem força de retorno para o operador. As manobras realizadas têm os seus dados cinemáticos e dinâmicos armazenados para posterior aplicação na aprendizagem por algoritmos de demonstração. No entanto, a produção de movimentos mais complexos e detalhados requer grandes quantidades de habilidade motora do operador. Devido à mudança contínua de usuários no PHUA, um período de adaptação é necessário para os operadores recém-chegados a desenvolver uma a nidade com o complexo sistema de controlo. Este trabalho é focado no desenvolvimento de metodologias para diminuir o tempo necessário para o processo de formação dos utilizadores. Graças à versatilidade de personalização fornecidos pela V-REP, foi possível implementar interfaces que utilizaram orientação visual e haptica para melhorar as capacidades de aprendizagem do operador. Uma estação de trabalho, novas formulações e ferramentas de apoio que controlam a simulação foram desenvolvidos a m de criar um controle mais intuitivo sobre a plataforma humanóide. Os operadores foram instruídos a reproduzir movimentos complexos em 3D sob diversas condições de treino (com feedback visual e haptico, apenas feedback haptico, apenas feedback visual, com ferramentas de orientação e sem orientação). O desempenho foi medido em termos de velocidade, a desvio de trajectória pretendida, a resposta à desvio e o tempo gasto para a criação do movimento. Os resultados deste estudo indicam que, com os mecanismos recém-implementadas, os operadores são capazes de ganhar o controlo sobre a plataforma humanóide dentro de um período relativamente curto de treino. Operadores submetidos a programas de orientação apresentam um período ainda mais curto de formação necessária, exibindo alto desempenho no sistema global. Estes fatos justi cam o papel da orientação haptica em adquirir memória cinestésica em sistemas DOFs elevados.

Computers are developed continuously to satisfy the human demands, and typical tools used everywhere for ranging from daily life usage to all kinds of research. Virtual Reality (VR), a virtual environment simulated to present physical presence in the real word and imaginary worlds, has been widely applied to simulate the virtual environment. People’s feeling is limited to visual perception when only computers are applied for simulations, since computers are limited to display visualization of data, while human senses include sight, smell, hearing, taste, touch and so on. Other devices can be applied, such as haptics, a device for sense of touch, to enhance the human perception in virtual environment. A good way to apply VR applications is to place them in a virtual display system, a system with multiply tools displays a virtual environment with experiencing different human senses, to enhance the people’s feeling of being immersed in a virtual environment. Such virtual display systems include VR dome, recursive acronym CAVE, VR workbench, VR workstation and so on. Menus with lots of advantages in manipulating applications are common in conventional systems, operating systems or other systems in computers. Normally a system will not be usable without them. Although VR applications are more natural and intuitive, they are much less or not usable without menus. But very few studies have focused on user interfaces in VR. This situation motivates us working further in this area. We want to create two models on different purposes. One is inspired from menus in conventional system and the sense of touch. And the other one is designed based on the spatial presence of VR. The first model is a two-dimensional pie menu in pop-up style with spring force feedback. This model is in a pie shape with eight options on the root menu. And there is a pop-up style hierarchical menu belongs to each option on the root menu. When the haptics device is near an option on the root menu, the spring force will force the haptics device towards to the center of the option and that option will be selected, and then the sub menu with nine options will pop up. The pie shape together with the spring force effect is expected to both increase the speed of selection and decrease the error rate of selection. The other model is a semiautomatic three-dimensional cube menu. This cube menu is designed with a aim to provide a simple, elegant, efficient and accurate user interface approach. This model is designed with four faces, including the front, back, left and right faces of the cube. Each face represents a category and has nine widgets. Users can make selections in different categories. An efficient way to change between categories is to rotate the cube automatically. Thus, a navigable rotation animation system is built and is manipulating the cube rotate horizontally for ninety degrees each time, so one of the faces will always face users. These two models are built under H3DAPI, an open source haptics software development platform with UI toolkit, a user interface toolkit. After the implementation, we made a pilot study, which is a formative study, to evaluate the feasibility of both menus. This pilot study includes a list of tasks for each menu, a questionnaire regards to the menu performance for each subject and a discussion with each subject. Six students participated as test subjects. In the pie menu, most of the subjects feel the spring force guides them to the target option and they can control the haptics device comfortably under such force. In the cube menu, the navigation rotation system works well and the cube rotates accurately and efficiently. The results of the pilot study show the models work as we initially expected. The recorded task completion time for each menu shows that with the same amount of tasks and similar difficulties, subjects spent more time on the cube menu than on the pie menu. This may implicate that pie menu is a faster approach comparing to the cube menu. We further consider that both the pie shape and force feedback may help reducing the selection time. The result for the option selection error rate test on the cube menu may implicates that option selection without any force feedback may also achieve a considerable good effect. Through the answers from the questionnaire for each subject, both menus are comfortable to use and in good control.

Cell adhesion to extracellular matrices (ECM) is critical to many cellular processes including differentiation, proliferation, migration, and apoptosis. Alterations in adhesive mechanisms are central to the behavior of cells in pathological conditions including cancer, atherosclerosis, and defects in wound healing. Although significant progress has been made in identifying molecules involved in adhesion, the mechanisms that dictate the generation of strong adhesive forces remain poorly understood. Specifically, the role of nanoscale geometry of the adhesive interface in integrin recruitment and adhesion forces remains elusive due to limitations in the techniques available for engineering cell adhesion environments. The objective of this project was to analyze the role of nanoscale geometry in cell adhesion strengthening to ECM. Our central hypothesis was that adhesive interactions are regulated by integrin clusters whose recruitment is determined by the nanoscale geometry of the adhesive interface and whose heterogeneity in size, spacing, and orientation modulates adhesion strength. The objective of this project was accomplished by 1) developing an experimental technique capable of producing nanoscale patterns of proteins on surfaces for cell adhesion arrays, 2) assessing the regulation of integrin recruitment by geometry of the adhesive interface, and 3) determining the functional implications of adhesive interface geometry by systematically analyzing the adhesion strengthening response to nanoscale patterns of proteins. A printing technique was developed that patterns proteins into features as small as 90nm with high contrast and high reproducibility. Cell adhesion arrays were produced by directly immobilizing proteins into patterns on mixed-SAMs surfaces with a protein-resistant background. Colocalization analysis of integrin recruitment to FN patterns demonstrated a concentrating effect of bound integrins at pattern sizes with areas equivalent to small nascent focal adhesions. At adhesion areas below 333 × 333 nm2, the frequency of integrin recruitment events decreased significantly indicating a threshold size for integrin clustering. Functionally, pattern sizes below the threshold were unable to participate in generation of adhesion strength. In contrast, patterns between the threshold and micron sizes showed a relationship between adhesion strength and area of individual adhesion points, independent of the total available adhesion area. These studies introduce a robust platform for producing nanoscale patterns of proteins in biologically relevant geometries. Results obtained using this approach yielded new insights on the role of nanoscale organization of the adhesive interface in modulating adhesion strength and integrin recruitment.

Los catecoles son compuestos aromáticos presentes en una gran variedad de sistemas naturales. Dada su gran versatilidad a nivel de propiedades fisicoquímicas, adquieren papeles clave en diferentes procesos naturales. Entre otros, los grupos catecol se encuentran en las proteínas adhesivas de los mejillones formando parte de aminoácido L-DOPA, que se considera responsable del extraordinario poder adhesivo de estos organismos en condiciones de extrema humedad. Este fenómeno ha fascinado a los científicos durante décadas y grandes esfuerzos se han destinado a entender e imitar estos sistemas. Otras propiedades de los catecoles, como su capacidad de formar complejos metálicos o su actividad redox, también han sido estudiadas tanto a nivel fundamental como en sistemas aplicados. En la presente tesis nos centramos en la obtención de sistemas de escala nanométrica basados en derivados de catecol y en el estudio de sus propiedades. Para ello, se llevó a cabo un trabajo multidisciplinar que incluye la síntesis de nuevos compuestos orgánicos, la obtención de nanoestructuras y el uso de microscopías y técnicas litográficas. En primer lugar se estudió la influencia de la densidad y orientación de los grupos catecol en las propiedades interfaciales de monocapas autoensambladas (SAMs) con unidades de catecol en el exterior; usando una punta de AFM o mediante la adsorción de nanopartículas magnéticas. Además, se estudió el efecto de la unidad de catecol en el proceso de formación y la estructura final de las monocapas. Por otro lado se llevó a cabo la síntesis de materiales poliméricos nanoestructurados basados en la funcionalidad catecol. Para ello se emplearon tanto metodologías clásicas como la síntesis confinada en pequeños volúmenes en superficie mediante el uso de litografía por escritura directa asistida por AFM. Esta técnica nos permitió fabricar estructuras de polidopamina y partículas de polímeros de coordinación mediante la deposición en superficie de los precursores de estos materiales en forma de gotas en la escala del femtolitro. De esta forma demostramos la viabilidad de la técnica para posicionar materiales funcionales en áreas concretas de una superficie.
Catechols are aromatic derivatives present in a variety of environments in nature. Due to their broad physicochemical versatility, they play pivotal roles in multiple natural processes. Probably their most popular appearance is in the adhesive proteins of mussels in the form of the rare aminoacid L-DOPA, which is considered to be essential for the strong adhesion of mussels to surfaces under high humidity conditions. This phenomenon has fascinated scientists for decades and intensive research has been carried out in order to understand and mimic these systems. Furthermore, other chemical properties of catechols, such as their metal-chelating and redox behaviour have also been addressed for both fundamental understanding and practical application. In this thesis we were interested in the obtention of nanoscale catechol-based systems and the study of their properties. For that, a multidisciplinary work was carried out which included the synthesis of new organic compounds, the preparation of nanostructures and the use of advanced microscopies and lithographic techniques. The role of packing density and orientation of catechol moieties in the interfacial properties of catechol-terminated SAMs was studied at the local scale using an AFM tip or, alternatively, magnetic nanoparticles. The influence that the presence of the catechol ring has on the formation and final structure of SAMs was also addressed. On the other hand, the synthesis of catechol-based polymers in confined volumes was performed using direct-write AFM-assisted lithography. Polydopamine and coordination polymer particles were fabricated directly on surfaces by controlled delivery of their molecular precursors in the shape of femtolitre-sized droplets. With that, we demonstrated the viability of using this technique to place functional amorphous materials on specific areas of surfaces.

Les interfaces haptiques à retour d'effort sont des dispositifs robotiques capables deproduire des forces à destination de l'utilisateur en téléopération et en réalité virtuelle. L'utilisation d'interface à retour d'effort en Conception Assistée par Ordinateur (CAO) offre de nouvelles perspectives pour la création et la conception de formes 3D grâce à une interactivité à la fois visuelle et kinesthésique. Elles permettent à la fois de visualiser, de manipuler en temps réel des objets virtuels et d'en ressentir les efforts (liés aux contacts, à la déformation, etc.).Les travaux présentés dans cette thèse contribuent au développement d'interfaces àretour d'effort pour répondre au mieux aux besoins de la CAO. Dans ce mémoire, l'accent est placé sur la problématique de la stabilité et son exploitation pour la commande de l'interface mais aussi pour la conception électromécanique. L'ensemble des travaux porte sur une interface à un degré de liberté.Dans un premier temps, différents facteurs liés au système mécanique (amortissement, modes vibratoires) et à l'environnement virtuel (échantillonnage, retard. . .) agissant sur la stabilité d'une interface sont mis en évidence à l'aide de critères fréquentiels. Ensuite, la conception d'une interface (choix et dimensionnement des composants) est ramenée sous forme d'un problème d'optimisation incluant une contrainte liée à la stabilité (en termes de domaine d'utilisation) et un critère de maximisation de la transparence (en termesd'inertie du dispositif).Dans un second temps, l'architecture de commande des dispositifs haptiques est étudiée. À l'aide d'une nouvelle condition de stabilité asymptotique pour les systèmes en temps discret à retard variable et en utilisant un observateur d'état augmenté comme alternative à l'utilisation standard de la méthode des différences finies arrières, la synthèse d'une nouvelle architecture de commande est proposée.La dernière partie du mémoire aborde la description du banc d'essai expérimental développé pendant le travail de thèse ainsi que les résultats des tests réalisés.

Depuis son invention en 1986, les microscopes à force atomique (AFM) ont été des puissants outils pour la caractérisation des matériaux et des propriétés des matériaux à l'échelle nanométrique. Cette thèse est entièrement dédiée à la mesure de l'interaction entre une sonde AFM et une surface avec une nouvelle technique AFM appelée Force Feedback Microscopy (FFM). La technique a été développée et utilisée pour l'étude d'échantillons biologiques. Le principe central de la technologie FFM est que la force totale moyenne appliquée à la pointe est égal à zéro. En conséquence, en présence d'une interaction pointe-échantillon, une force égale et contraire doit être appliquée à la pointe par une boucle de rétroaction. La force de réaction est ici appliquée à la pointe à travers le déplacement d'un petit élément piézoélectrique positionné à la base du levier AFM. La boucle de rétroaction permet d'éviter instabilités mécaniques tels que le saut au contact, permettant la mesure complète de la courbe d'interaction. En plus, il donne la possibilité de mesurer simultanément les parties élastique et inélastique de l'interaction. La technique a été appliquée à l'étude des interactions à l'interface solide/gaz, avec un intérêt particulier pour l'observation de la formation et de la rupture des ponts capillaires entre pointe et échantillon. Ensuite, on a focalisé notre attention aux interfaces solide/liquide. Dans ce contexte, courbes complètes de type DLVO sont caractérisées d'un point de vue élastique et dissipatif. Nous avons développé des nouveaux modes d'imagerie AFM pour l'étude des biomolécules. Images de phospholipides et de l'ADN à force constante ont été réalisées et certaines propriétés mécaniques comme le module de Young des échantillons ont été évaluées. En plus, nous avons réalisé une étude spectroscopique de l'élasticité et du coeffcient d'amortissement de l'interaction entre des cellules vivantes de type PC12 et une pointe AFM en nitrure de silicium. L'étude montre que le FFM est un instrument capable de mesurer l'interaction à des fréquences qui ne sont pas nécessairement liées aux résonances caractéristiques du levier. L'étude spectroscopique pourrait avoir dans le futur des applications importantes pour l'étude des biomolécules et des polymères.