Augmenter la durée de vie d'une pile, voire s'en passer est aujourd'hui devenu une obligation pour les microsystèmes. En effet, à cette échelle, le remplacement des piles et leur rejet dans l'environnement sont problématiques. La voie préconisée pour répondre à cet enjeu est d'utiliser des sources d'énergie renouvelables (solaire, thermique et mécanique). Pour cela, nous proposons de développer une plateforme de récupération d'énergie multi-sources/multi-charges (MANAGY) capable de s'adapter à son environnement pour en extraire le maximum d'énergie et répondre à des applications diverses. L'architecture est constituée de chemins directs et de chemins indirects où l'énergie provenant des sources est d'abord transférée dans une unité de stockage avant d'être réutilisée par les charges du microsystème. L'utilisation de cette nouvelle architecture permet d'optimiser le transfert d'énergie entre sources et charges et améliore le rendement du système de 33%. Avant de développer une architecture multi-sources, nous avons cherché à améliorer le rendement de la source photovoltaïque (PV) qui, au vu de l'état de l'art, a la densité de puissance la plus élevée. La recherche du rendement maximum de la source PV revient à la recherche du point de puissance maximum (MPPT). Il existe pour chaque condition d'irradiance, de température, et d'énergie extraites un couple tension-courant permettant à la source de fournir un maximum de puissance (MPP). Grâce à l'utilisation de deux chemins de puissance, nous arrivons simultanément à créer une boucle de régulation faible puissance agissant sur le rapport cyclique du système de gestion d'énergie (MPPT) et une boucle de régulation de la tension de sortie agissant sur le transfert de l'énergie. La modélisation du système nous a permis de spécifier ses performances. Pour atteindre les performances requises, des architectures innovantes ont été réalisées qui ont fait l'objet de trois brevets. De plus, des blocs ne sont activés qu'aux instants de changement d'état du système et sont conçus, quand cela a été possible, avec des transistors fonctionnant en mode faible inversion. Toutes ces optimisations permettent au système de fonctionner sur une large plage de variation de l'éclairement (de conditions intérieures supérieures à 500 lux à extérieures) avec un rendement proche de 90%. / Enhancing the life time of battery or being able to work without it is today mandatory for microsystems. Most of systems are nowadays limited by the capacity of the embedded battery. Moreover the replacement and waste of baterries is no more possible at this scale. One way to achieve longer life time is the use of renewable energy sources (solar, thermal, or kinetic). This work proposes to develop a new energy harvesting platform with numerous sources and loads (MANAGY) able to adapt itself to the surrounding environment in order to extract the maximum of energy while answering to various of applications. The architecture is composed of directs and indirects power paths where the extracted energy coming from renewable sources is firstly transferred to a storage unit before being used by loads. This novel architecture makes it possible to optimize the energy transfer between sources and loads and to achieve a 33% gain. Before developing this architecture with numerous sources, we have searched to enhance the efficiency of the photovoltaic source which has the best power density at the state of the art. Looking for improving the efficiency of the PV source is the same as tracking the maximum power point (MPPT). There is for each irradiance, temperature and quantity of energy extracted a couple of voltage and current enabling the PV source to deliver the maximum of power (MPP). Thanks to the two power paths used we are able to create a low power feedback loop adjusting the duty cycle from the power management unit (MPPT) while having a second feedback loop optimizing the power transfer and regulating the output voltage. Thanks to a high level model we have specified the system performances. To achieve the performances required we have realized novel architectures protected through three patents. Moreover, blocs are only activated when the system changes its state and furthermore there are designs, when achievable, with transistors working in weak inversion. All these optimizations make the system working for a large range of irradiance (from inside conditions higher than 500 lux to outdoor conditions) with an efficiency close to 90%.

Certains problèmes d’audition trouvent leur origine dans des anomalies de transmission de l’énergie des vibrations acoustique par la chaîne des osselets de l’oreille moyenne. Il se pratique aujourd’hui des opérations chirurgicales visant à la reconstruire. Un outil permettant d’évaluer la qualité de transmission des vibrations par de la chaîne ossiculaire pendant l’opération apporterait une aide substantielle au praticien afin dans le but d’optimiser la configuration des osselets. Les travaux présentés dans ce manuscrit traitent de la conception d’un capteur microsystème adapté à la mesure de l’amplitude de vibrations des osselets. Nous y avons particulièrement développé les travaux de modélisation de la structure mécanique du capteur. Il s’agit d’une structure communément employée pour les capteurs tactiles dont nous modélisons le comportement en régime harmonique. Dans une la deuxième partie nous présentons une étude d’optimisation du capteur en vue de son utilisation « tenu en main » par le chirurgien. Celle-ci repose notamment sur l’utilisation d’un modèle électrique équivalent de l’oreille moyenne et d’un logiciel d’optimisation multicritères. Nous présentons dans cette partie un concept de filtre mécanique des basses fréquences par l’utilisation des propriétés viscoélastiques des matériaux polymères. La dernière partie traite des travaux de réalisation des différents composants d’un capteur basé sur les matériaux polymères. Les travaux de réalisation et de test de membranes en résine SU8 y sont présentés ainsi que l’intégration de jauges en matériaux électroactifs chargés en nanoparticules. L’utilisation d’une technique de moule perdu pour réaliser la structure mécanique du capteur est discutée. / Acoustic transmission anomalies of the middle ear ossicular chain can result in hearing losses. Nowadays some surgical interventions allow significant hearing improvements by reconstructing the ossicular chain. A tool able to evaluate vibration transmission along the ossicular chain would be of great help to the surgeon. The work presented in this manuscript deals with the conception design of a MEMS sensor adapted suitable ftoor ossicle’s vibration amplitude measurement. Modelling of the sensor structure mechanical behaviour has been particularly developed. The presented structure which is similar to onethat widely used in tactile sensors conception design that wewas modelled ins the harmonic vibrating regime here.

O escopo deste trabalho foi o desenvolvimento de microrreatores em tecnologia LTCC para produção de biodiesel, com foco na otimização de uma geometria de micromisturador. Esta proposta é resultado das oportunidades identificadas em três áreas do conhecimento: Microtecnologia, Intensificação de processos e Biocombustíveis. A principal ferramenta de desenvolvimento desta proposta é a fluidodinâmica computacional. Os microcanais baseados em geometrias com sucessivos cotovelos foram os escolhidos, para a investigação computacional e experimental. A metodologia computacional desenvolvida para alcançar os objetivos propostos envolve as etapas de: definição de um padrão de comparação, projeto das distâncias entre cotovelos, escolha de uma geometria com base na comparação entre diversas geometrias baseadas em sucessivos cotovelos e a otimização da geometria em função dos parâmetros fluidodinâmicos. Paralelamente, ensaios para a produção de biodiesel foram realizados, bem como, a investigação da produção de emulsões para avaliar como uma etapa do processo de produção do biodiesel. A geometria escolhida e otimizada foi a serpentina 3D, o que permitiu a otimização do módulo de tempo de residência e o projeto do microrreator. Finalizando, um microrreator foi projetado com parâmetros ótimos, obtendo assim a intensificação de processo por meio de conceitos de microtecnologia, para aplicação na produção de biocombustíveis. / The scope of this work was the development of microreactors in LTCC technology for biodiesel production, with a focus on the optimization of a micromixer geometry. This proposal is resulted from the opportunities identified in three areas of knowledge: Microtechnology, processes intensification and Biofuels. The main tool for development of this proposal is the computational fluid dynamics (CFD). The microchannels geometry with successive elbows were chosen for computational and experimental research. The computational methodology developed to achieve the proposed goals involves the following steps: defining a standard of comparison, a project of the distances between elbows, a choice of geometry based on the comparison between different geometries based on successive elbows and geometry optimization for the parameters hydrodynamic. In addition, tests for the production of biodiesel were being made and the investigations of production of emulsions to evaluate a step in the producing of biodiesel process. The geometry was chosen and optimized serpentine 3D, allowing the optimization of residence time module and the design of the microreactor. Finally, a microreactor was designed with optimal parameters, thus obtaining the intensification process through microtechnology concepts for application in the biofuels production.

O trabalho descrito nesta tese mostra a aplicação de um sistema de detecção condutométrica sem contato acoplado capacitivamente (C4D) para monitorar interações biomoleculares em microssistemas analíticos. Inicialmente, o desempenho analítico de microssistemas fabricados em vidro, poli(dimetilsiloxano) (PDMS) e poliéster-toner (PT) foi avaliado de modo a escolher o melhor material (em termos de facilidades de fabricação, custo e repetibilidade) para os ensaios biomoleculares. Dentre os materiais estudados, os dispositivos fabricados em PT mostraram-se mais adequados para testes rápidos, onde a repetibilidade analítica não é o parâmetro mais importante. Os dispositivos fabricados em PDMS e selados contra uma placa de vidro apresentaram os melhores resultados em termos de repetibilidade e o desempenho analítico foi similar aos dispositivos de vidro. Dessa maneira, os dispositivos fabricados em PDMS/vidro foram escolhidos para a demonstração dos objetivos da tese. Por outro lado, os dispositivos fabricados em PT foram explorados para estudar a configuração geométrica do sistema de C4D. A instrumentação para monitoramento dos ensaios de ligação foi composta basicamente de dois sistemas de C4D, um software escrito em LabVIEW e um sistema de bombeamento das soluções. De modo a encontrar a configuração ideal da cela de detecção, geometrias contendo três, quatro e cinco eletrodos foram avaliadas em dispositivos de PT. A configuração ótima foi composta de três eletrodos, espaçados simetricamente. Nesta geometria, um eletrodo é utilizado para aplicar o sinal senoidal de excitação e os outros dois são utilizados para capturar o sinal resultante. As dimensões dos eletrodos (largura e espaçamento entre eles) foram otimizados usando ferramentas quimométricas. O complexo avidina-biotina foi utilizado como modelo de ligação para mostrar a aplicabilidade do sistema proposto. Para os microssistemas biomoleculares, os eletrodos (com geometria otimizada) foram fabricados sobre a superfície de uma placa de vidro por fotolitografia, sputtering e lift-off. Os eletrodos de detecção foram isolados com uma camada de óxido de silício com espessura de 50 nm, depositada pelo processo de deposição química em fase de vapor assistida por plasma. A camada de SiO2 foi modificada quimicamente com solução de 3-amino-propil-trietóxi-silano em etanol. Para imobilização covalente de biotina, uma alíquota de 10 ?L de fotobiotina dissolvida em água (0,1 mg/mL) foi adicionada à superfície e exposta a radiação ultravioleta (365 nm, 10 mW/cm2) durante 15 min. A detecção foi realizada aplicando um sinal senoidal, a partir de um gerador de funções, ao eletrodo de excitação registrando o sinal resultante nos dois eletrodos receptores. Para minimizar a captura de ruído elétrico, os experimentos foram realizados em uma gaiola de Faraday. O controle e a aquisição de dados foi feito mediante um software escrito em LabVIEW monitorando os sensorgramas de condutividade em tempo real. Os canais microfluídicos foram fabricados em PDMS por litografia suave e selados irrevesivelmente contra a placa de vidro contendo os eletrodos isolados e modificados quimicamente. As soluções (tampão e amostra) foram manuseadas com auxílio de uma bomba peristáltica ou duas bombas seringas. Soluções contendo tampão e avidina foram introduzidas nos microcanais e as mudanças de conductividade foram monitoradas em função do tempo. As soluções contendo avidina permaneceram em contato com a superfície modificada até o sinal de condutividade atingir um patamar de equilíbrio. Depois disso, solução tampão foi introduzida no microcanal para remover os analitos adsorvidos à superfície. Duas válvulas solenóides foram utilizadas para permitir um controle automático da distribuição das soluções nos microcanais. O limite de detecção obtido para a interação entre avidina e biotina foi de 75 nmol L-1. / The study reported in this thesis shows the application of a capacitively coupled contactless conductivity detection (C4D) for monitoring biomolecular interactions on analytical microsystems. Initially, the analytical performance of the microsystems fabricated in glass, poly(dimethylsiloxane) (PDMS) and polyester-toner (PT) was investigated in order to choose the best material (in terms of fabrication facilities, costs and repeatability) for the biomolecular assays. Among all substrate materials studied, devices fabricated in PT showed suitability for quick experiments, in which the analytical repeatability is not the most important parameter. The devices fabricated in PDMS and sealed against a glass plate presented the best results in terms of repeatability and the analytical performance was similar to that one of glass devices. For this reason, PDMS/glass devices were chosen for showing the goals of this thesis. On the other hand, PT devices were employed to study the geometrical design of the C4D system. The instrumentation for monitoring binding assays was basically composed of two C4D systems, a software written in LabVIEW and a solution pumping system. In order to find the suitable detection cell configuration for this dual-C4D system, designs containing three, four and five electrodes were evaluated on PT devices. The optimal design was composed of three electrodes symmetrically spaced. In this configuration, one electrode is used for applying an excitation sinusoidal wave and the other two for picking up the resulting signal. The dimensions of the electrodes (width and gap) were optimized by chemometric tools. The avidin-biotin complex was used as a binding model for showing the feasibility of the proposed system. For the biomolecular microsystems, electrodes were fabricated on glass surface using photolithographic, sputtering and lift-off processes. Detection electrodes were insulated with a 50-nm silicon oxide layer deposited by plasmaenhanced chemical vapor deposition. The SiO2 layer was functionalized by immersing the cleaned surface in a 3-aminopropyltriethoxy-silane solution in ethanol for 3 h. For biotinylation of the amino-silane layer, 10 ?L of photobiotin dissolved in deionized water (0.1 mg/mL) was dropped on the modified glass surface and exposed to a 365 nm UV radiation at intensity of 10 mW/cm2 for 15 min. Detection was carried out by passing a sinusoidal excitation signal from the function signal generator to the first electrode and picking up the resulting signal at the two receiver electrodes. To reduce electrical noise pickup, all measurements were carried out in a Faraday cage. The data acquisition was obtained in a software written in LabVIEW and the conductivity sensorgrams were recorded in real-time. The microfluidic network was fabricated in PDMS by soft lithography and irreversibly sealed against the electrodes plate. Solutions were handled into microfluidic channels using a peristaltic pump or two syringe pumps. Buffer and avidin-containing solution was injected into the microchannels and conductivity changes were monitored over time. Avidin solutions were allowed to remain in contact with the surface until a stable conductivity had reached equilibrium. Avidin-free buffer solutions were then injected to rinse off non-specifically bound analytes. Two solenoid valves were used to allow an automatic dispensing of the sample/buffer solution into microchannels. The limit of detection found for avidin-biotin system was 75 nmol L-1.

Orientador: Luiz Otávio Saraiva Ferreira. / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T04:03:41Z (GMT). No. of bitstreams: 1 Silva_MarioEduardodeBarrosGomeseNunesda_M.pdf: 3848213 bytes, checksum: ebb7fc7d814e03c6ae81ee577ddb158f (MD5) Previous issue date: 2012 / Resumo: A caracterização das propriedades mecânicas de filmes finos faz-se necessária para o projeto e fabricação de Microsistemas Eletromecânicos (MEMS - Micro-Electro-Mechanical Systems), que demanda dados precisos dos materiais. Esta pesquisa descreve um novo método de caracterização das propriedades mecânicas de filmes finos, barato e aplicávela uma ampla gama de materiais. Além do mais, este método também pode ser utilizado para avaliar a resistência das microestruturas durante cada etapa do processo de fabricação, e mesmo do sistema completo. Para realizar os experimentos de caracterização é utilizado um perfilômetro de superfície. Perfilômetros de superfície são dispositivos utilizados para medir a espessura e rugosidade de filmes, sendo essenciais em laboratórios de microfabricação. Tal fato permite que seja possivel repetir os experimentos deste trabalho em qualquer laboratório que possua um perfilômetro de superfície, sem a necessidade de investimento em novos equipamentos. O método de caracterização baseia-se na flexão de microestruturas suspensas. Os corpos de prova são fabricados no material em teste, e um perfilômetro de superfície é usado para defleti-los, e a partir dos dados desse experimento, pode-se calcular o módulo de Young. Caso os corpos de prova venham a se fraturar é possivel calcular a tensão de ruptura. Em uma primeira etapa do trabalho, foram caracterizados filmes de óxido de silício, fabricados por óxidação térmica de um substrado de silício monocristalino. Na segunda etapa, o método de caracterização foi expandido para filmes sobrepostos de materiais diversos e, foram caraterizados filmes de nitreto de silício, fazendo uso de microestruturas compostas de nitreto de silicio, depositado pelo método de vapor químico de baixa pressão (LPCVD), sobre o óxido de silício fabricado por óxidação térmica. O presente trabalho também sugere uma forma de utilizar o mesmo método de caracterização para determinar o coeficiente de Poisson, fazendo uso de várias amostras com expessuras diversas. Os corpos de prova foram fabricados no Centro de Componentes Semicondutores (CCS) da Universidade Estadual de Campinas (UNICAMP), e os experimentos de deflexão realizados no Laboratório de Microfabricação (LMF) do Laboratório Nacional de Nanotecnologia (LNNano) / Abstract: The mechanical properties characterization of thin films is necessary for MEMS (Micro-Electro-Mechanical Systems) design and manufacture, which requires accurate materials data. This research describes a new method for mechanical properties characterization of thin films, inexpensive and applicable to a wide range of materials. Also, this method can be used to evaluate the resistance of the microstructures during each step of the manufacturing process, and even the complete system. To perform the experiments of characterization is used a surface profilometer. Surface profilometers are devices generally used to measure the films thickness and roughness, and they are essential in microfabrication laboratories. This fact allows the possibility of repetitive the experiments of this work in any laboratory that has a surface profilometer, without the necessity to invest in new equipment. The characterization method is based on bending of suspended microstructures. The specimens are fabricated in the material under test, and a surface profilometer is used to deflect then, and from this experiment data, it's possible to calculate the Young's modulus. If the specimens fracture, it is possible to calculate the tensile strength. In a first step, were characterized films of silicon oxide, manufactured by thermal oxidation of a monocrystalline silicon substrate. In the second step, the characterization method has been expanded to superimposed films of various materials and films of silicon nitride were characterized, by making use of microstructures consisting of silicon nitride, deposited by the method of low-pressure chemical vapor (LPCVD), over the silicon oxide produced by thermal oxidation. The present work also suggests a way to use the same characterization method for determining the Poisson's ratio, using various samples with different thickness. The specimens were fabricated in the Center for Semiconductor Components (CCS) of University of Campinas (UNICAMP), and the deflection experiments performed in the Microfabrication Laboratory (LMF) of Brazilian Nanotechnology National Laboratory (LNNano) / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Les actionneurs piézoélectriques sont très utilisés pour les systèmes de positionnement pour des tâches à l'échelle micro/nanométrique en raison de leur haute résolution (sub-micrométrique), leur grande bande passante, et une densité de force élevée. Cependant, ils sont caractérisés par des non-linéarités telles que l'hystérésis et la dérive lente, par une grande sensibilité à l’environnement, et pour certains par des comportements oscillatoires. Ces caractéristiques ont un impact considérable sur les tâches que ces actionneurs doivent effectuer et leur contrôle reste souvent difficile. Différents correcteurs robustes ont été développés pour contrôler les actionneurs piézoélectriques. Il s'agit notamment de l'approche grand gain, des approches H-inf, des approches de contrôle basée sur l'observation des perturbations, ...etc. Ces techniques ont démontré une amélioration significative des performances mais mènent souvent à des correcteurs d'ordre élevé qui sont difficiles à mettre en œuvre. Cette thèse consiste à développer des correcteurs pour des actionneurs piézoélectriques en combinant l'analyse d'intervalle et les techniques classiques de commande.Les avantages principaux d’utiliser des intervalles est qu'ils permettent de modéliser facilement les incertitudes paramétriques en les limitant par des bornes. Par ailleurs, les travaux existants démontrent qu’il est possible de synthétiser de manière plus simplifiée des correcteurs robustes d’ordre faible, c-à-d ordre inférieur à celui du modèle. L'état de l'art sur l'utilisation des techniques par intervalle pour la synthèse de correcteurs peut être présenté en deux catégories : les techniques par intervalle basées sur des fonctions de transfert, et les techniques par intervalle basées sur la représentation d’état. Les techniques par intervalle basées sur les fonctions de transfert sont actuellement limitées pour modéliser et synthétiser des correcteurs pour des systèmes monovariables incertains tandis que les techniques basées sur la représentation d'état sont bien adaptées pour des systèmes multivariables incertains. Néanmoins, ces travaux existants pour des systèmes multivariables sont limités aux modèles avec des matrices d'état et d'entrée de structures spéciales. En outre, elles ne portent que sur le degré de stabilité du système en boucle fermée et ne prennent pas donc en compte des spécifications sur les performances. Cette thèse développe des outils de synthèse de correcteurs robustes pour des systèmes multivariables à incertitudes paramétriques dans l’approche d’état par intervalle sans structure particulière et en considérant à priori des performances. Des validations expérimentales sur différents actionneurs piézoélectriques, et ce en commande en position et en force, sont efféctuées. Enfin, la thèse propose également l’extension des observateurs à entrée inconnue pour les systèmes par intervalle afin de compléter les techniques de commande proposées. / Piezoelectric actuators are widely used at micro/nanoscale because of their simpleconfiguration, high resolution (sub-nanometric), high speed (large bandwidth upto 1kHz), and high force density. However, they are characterized by some nonlinearitiessuch as hysteresis, internal friction and creep,...etc. These characteristicsconsiderably impact the dynamics of the piezoactuators which makes the controlof these systems not a trivial task. Various robust controllers have been developedto control piezoelectric actuators. These include high gain feedback approach, H1approach, disturbance observer based control approach,...etc. Those techniquesdemonstrated a significant improvement of the control performance, but they oftenderive controllers with high-order which are difficult for implementation. Tobypass this limitation, we focus on the thesis on combining interval analysis withclassical controller design techniques to obtain a low order controllers. The mainadvantage of intervals is that they permit to model parametric uncertainties easilyby bounding them. Furthermore, the process of modeling the system uncertaintiesby intervals makes the synthesis of robust controller with low order relatively easy.The state of the art on the use of interval techniques to design and derive robustcontrollers for uncertain system can be divided into two categories: intervaltransfer functions based approaches and interval state-space representation basedapproaches. Interval transfer functions based designs have been widely used tomodel and to control SISO (Single Input single Output) systems subjected to uncertainties.These approaches make the synthesis of robust controllers for suchsystems easy with providing good performance. However, the current work thatuse interval transfer functions are limited to systems in SISO case. In the otherside, the state-space based approaches have been shown to be well adapted tosynthesis robust controllers for multivariable systems. Nevertheless, the excitingworks are limited to systems with state and input matrices of special structures.Furthermore, they address only the degree of stability of the closed-loop systemwithout discussing performance specification. In order to make the design of robustcontroller using interval state-space approach possible for any interval state-spacestructure, this thesis will explore the interval state-space control design using robustpole assignment technique. This proposed approach will guarantee the stability and the desired performance of the closed-loop system also it allows to obtaina low order controller.For this matter, an algorithm based on Set Inversion Via Interval Analysis(SIVIA) combined with interval eigenvalues computation is proposed to seek for aset of robust gains. This recursive SIVIA-based algorithm allows to approximatewith subpaving the set solutions [K] that satisfy the inclusion of the eigenvaluesof the closed-loop system in a desired region in the complex plan. Furthermore,simple algorithms are proposed to find the optimal feedback gains among the rangeof robust gains [K] as well as the range of the gains that satisfy input constraints,all with the help of interval analysis. Finally, in order to improve the controllerperformance, we were directed our attention to nonlinear control approaches andespecially interval sliding mode control (ISMC) design using interval observers.The effectiveness of the proposed approaches are tested by a real experimentationon several platforms developed in our laboratory to achieve robust performance.

Les microalgues présentent un vrai potentiel d’innovation dans les principaux secteurs industriels tel que l’énergie, l’agroalimentaire, la cosmétique et la santé. Elles sont considérées comme étant la solution privilégiée pour répondre aux besoins énergétiques futurs et ainsi permettre une transition des énergies fossiles vers les énergies renouvelables. Néanmoins, les systèmes de production à grande échelle à partir de microalgues nécessitent encore des améliorations afin de les rendre économiquement compétitifs et durables tout en préservant l’environnement.Ainsi, l’objectif de cette thèse consiste à évaluer une nouvelle voie pour l’extraction de composés d’intérêt à partir de microalgues et de caractériser leur performance en termes d’efficacité d’extraction. L’utilisation combinée de champs électriques pulsés, et de compressions mécaniques (à travers un système microfluidique dédié) en tant que prétraitements à l’extraction de composés lipidiques, riches en énergie, produits par la microalgue Chlamydomonas reinhardtii, a donc été étudiée. Les mécanismes mis en jeu, à l’échelle de la cellule, ont été mis en évidence.Ce projet de thèse s’est déroulé dans le contexte d’une collaboration entre les laboratoires SATIE de l’ENS Paris-Saclay et LGPM de CentraleSupélec Paris-Saclay.Les résultats obtenus ont permis de confirmer le potentiel des technologies utilisées dans l’amélioration du rendement d’extraction de l’huile algale. Cette étude démontre notamment le rôle important de la paroi cellulaire de l’algue en tant qu’obstacle à une extraction optimale. Une étude approfondie de sa réponse physiologique aux prétraitements et aux conditions de stress est proposée. / Microalgae have a real potential in the innovation of the main industrial sectors such as energy, food, cosmetics and health. They are considered as a promising solution to meet future energy needs and thus enable a transition from fossil to renewable energies. Nevertheless, large scale production systems using microalgae still need improvements to become economically competitive and sustainable while preserving the environment.Thus, the aim of this thesis is to evaluate an innovative approach for the extraction of compounds of interest from microalgae and characterize their performance in terms of extraction efficiency. The effect of combining pulsed electric fields and mechanical compressions (through a dedicated microfluidic system) as pretreatments for the extraction of lipids, energy-rich compounds produced by the microalga Chlamydomonas reinhardtii, was therefore studied. The mechanisms involved, at the cellular scale, were highlighted.This project took place in the context of a collaboration between the laboratories SATIE of ENS Paris-Saclay and LGPM of CentraleSupélec Paris-Saclay.The obtained results have confirmed the potential of the technologies to improve the algal oil extraction. Furthermore, this study demonstrates the important role of the algae’s cell wall as an obstacle to an optimal extraction. A comprehensive study of the microalgae’s physiological response to pretreatments and stress conditions is proposed.

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The proliferation of web based technologies has resulted in new forms of communities and organizations with enormous implications for design of learning and education. This thesis explores learning occurring within open source software (OSS) communities. OSS communities are a dominant form of organizing in software development with implications not only for innovative product development but also for the training of a large number of software developers. The central catalyst of learning within these communities is expert-novice interactions. These interactions between experts and novices or newcomers are critical for the growth and sustenance of a community and therefore it is imperative that experts are able to provide newcomers requisite advice and support as they traverse the community and develop software. Although prior literature has demonstrated the significance of expert-novice interactions, there are two central issues that have not been examined. First, there is no examination of the role of external events on community interaction, particularly as it relates to experts and novices. Second, the exact nature of expert help, particularly, the quantity of help and whether it helps or hinders newcomer participation has not been studied. This thesis studies these two aspects of expert-novice interaction within OSS communities. The data for this study comes from two OSS communities. The Java newcomer forum was studied as it provided a useful setting for examining external events given the recent changes in Java's ownership. Furthermore, the forum has a rating system which classifies newcomers and experienced members allowing the analysis of expert-novice interactions. The second set of data comes from the MySQL newcomer forum which has also undergone organizational changes and allows for comparison with data from the Java forum. Data were collected by parsing information from the HTML pages and stored in a relational database. To analyze the effect of external events, a natural experiment method was used whereby participation levels were studied around significant events that affected the community. To better understand the changes contextually, an extensive study of major news outlets was also undertaken. Findings from the external event study show significant changes in participation patterns, especially among newcomers in response to key external events. The study also revealed that the changes in participation of newcomers were observed even though other internal characteristics (help giving, expert participation) did not change indicating that external events have a strong bearing on community participation. The effect of expert advice was studied using a logistic regression model to determine how specific participation patterns in discussion threads led to the final response to newcomers. This was supported by social network analysis to visually interpret the participation patterns of experienced members in two different scenarios, one in which the question was answered and the other where it was not. Findings show that higher number of responses from experienced members did not correlate with a response. Therefore, although expert help is essential, non-moderated or unguided help can lead to conflict among experts and inefficient feedback to newcomers. / Master of Science

Le travail présenté dans ce mémoire concerne la réalisation d’un microsystème intégrant une centrale inertielle permettant la détection de mouvements. Le microsystème étudié est composé d’un accéléromètre capacitif associé à son électronique de traitement. L’accéléromètre capacitif a conduit à l’élaboration d’un outil logiciel afin de le pré-dimensionner. Ce pré-dimensionnement a été effectué en fonction des spécifications de l’application et de la technologie de fabrication. Cet outil intègre des modèles fluidiques et électrostatiques en vue de calculer des paramètres du modèle de l’accéléromètre pour une simulation système. L’électronique de traitement de l’accéléromètre capacitif a été conçue autour d’un convertisseur ”Sigma-Delta”. L’architecture ”Sigma-Delta” a nécessité des modifications pour pouvoir être adaptée au capteur. Nous avons alors développé, sous ”Matlab-Simulink”, une bibliothèque de composants permettant d’ajuster le fonctionnement du convertisseur. Une fois l’architecture optimisée et les caractéristiques des composants connues, la conception de l’architecture ”Sigma-Delta” est ainsi réalisable sous le logiciel CADENCE. / The aim of this thesis is the realisation of microsystem for movements detection. This microsystem is composed of capacitive accelerometers and of their electronics. The conception of capacitive accelerometers has induced developement of a software for the first dimensionnement of sensors. This software computes parameters of capacitive accelerometers thanks to electrostatic models, flow models, specifications of application and fabrication process. The electronics of capacitive accelerometer is a ”Sigma-Delta” convertor. The adaptation of convertor leads to developement of components libraries for ”Matlab-Simulink”. The simulation systems allows to fit parametres convertor for the application. After that,the conception of convertor under CADENCE software is then possible.