Ce travail de thèse, débuté en 2015, a pour but de développer et d'étudier les propriétés de nouveaux liants polymères pour batteries Li-ion. Les synthèses organiques ainsi que leurs caractérisations associées et les tests électrochimiques ont été réalisées à Delft. Puis, des études de spectroscopie photo-électronique par rayons X (XPS) ont été réalisées à Pau pour déterminer et comprendre la réactivité de certain de ces nouveaux matériaux vis-à-vis du lithium. / This PhD work started in 2015, aimed to develop and investigate the properties of new polymers as binders for Li-ion batteries. Organic syntheses with associated characterizations and electrochemical tests were performed in Delft. Then, X-ray photoelectron spectroscopy studies were performed in Pau, to determine and understand the reactivity of some of these new materials toward lithium ions in coin cells.

L’objectif de cette thèse était de réaliser de nouveaux matériaux à émissivité variable dans l’infrarouge pour une application de régulation thermique des satellites artificiels. Dans ce contexte, l’étude s’est concentrée sur l’élaboration et la caractérisation de dispositifs électroémissifs à base d’un polymère conducteur électronique, le poly(3,4-éthylènedioxythiophène) (PEDOT) obtenu par électropolymérisation. Ces dispositifs électroémissifs ont ensuite été évalués dans des conditions partiellement représentatives de l’environnement spatial.La première partie de ce manuscrit a été consacrée à l’incorporation du PEDOT par électropolymérisation au sein d’une matrice hôte, formée à partir d’un réseau interpénétré de polymère (RIP) à base de caoutchouc nitrile (NBR) et de poly(oxyde d’éthylène) (POE). L’électropolymérisation par une méthode de chronopotentiométrie pulsée a permis d’obtenir des couches actives de PEDOT reproductibles, démontrant ainsi que le procédé électrochimique est bien contrôlé. En parallèle, des dispositifs électroémissifs de référence dont la couche active de PEDOT a été synthétisée par une polymérisation chimique oxydante, ont été élaborés. Le comportement électrochimique, les propriétés optiques dans l’infrarouge et la morphologie des couches actives obtenues par électropolymérisation ont été comparés à celles obtenues par une polymérisation chimique oxydante. Une répartition différente du PEDOT en fonction de la méthode d’incorporation a notamment été démontrée.Dans la deuxième partie de ce manuscrit, le comportement actionneur des dispositifs électroémissifs, qui est majoritairement induit par une insertion ou une expulsion d’ions au cours du procédé redox, a été étudié. Un screening de liquides ioniques, possédant des structures chimiques différentes, a été réalisé. Le mécanisme d’ion impliqué lors de la réaction redox a été identifié par une méthode simple consistant à observer la variation de volume de la couche active de PEDOT. Cette méthode a permis de souligner le rôle prédominant des cations au sein du procédé redox. L’utilisation de deux liquides ioniques a notamment permis une réduction significative de la déformation du dispositif électroémissif de référence tout en conservant de bonnes propriétés optiques dans l’infrarouge. Des mélanges de liquides ionique et de sel de lithium ont également été étudiés. En fonction de la concentration en sel de lithium au sein d’un liquide ionique, il est possible de contrôler le mécanisme ionique qui gouverne la réaction redox. Une concentration en sel en particulier entraine à la succession des deux mécanismes ioniques, ce qui donne lieu à un faible effet actionneur tout en préservant l’électro-activité et les propriétés optiques dans l’infrarouge du système.Dans la dernière partie de ce manuscrit, un prototype a été réalisé et évalué pour une application de contrôle thermique. Des radiateurs à base de dispositifs électroémissifs ont été fabriqués puis testés dans des conditions proches de l’environnement spatial. Ces radiateurs ont ensuite été comparés à la technologie actuellement utilisée sur les satellites artificiels, les réflecteurs optiques solaires. Des changements de température significatifs (12 °C) ont été mis en évidence, démontrant la pertinence de ce type de système pour une application de régulation thermique. Une faible consommation électrique de ces systèmes a été mise en avant au cours de ces travaux. Associé à la faible masse embarquée les dispositifs électroémissifs élaborés ont ainsi un intérêt double pour l’application visée par rapport à la technologie actuelle. / The aim of this PhD work is to design new coatings with variable emissivity in the infrared for an application of thermal regulation of artificial satellites. In this context, the study focuses on the development of electroemissive devices based on an electronically conducting polymer, the poly (3,4-ethylenedioxythiophene) (PEDOT). These electroemissive devices are then evaluated under space like environment.The first part of this manuscript was devoted to the incorporation of PEDOT by electropolymerization within a host matrix based on an interpenetrating polymer network (IPN) including nitrile butadiene rubber (NBR) and poly (ethylene oxide) (PEO). Electropolymerization by a pulsed chronopotentiometry method resulted in reproducible active PEDOT layers, demonstrating that the electrochemical process is well-controlled. In parallel, electroemissive deviceswhose active layer of PEDOT was synthesized by an oxidative chemical polymerization, were elaborated as refernce devices. The electrochemical behavior, the infrared optical properties and the morphology of the active layers obtained by electropolymerization were compared with those obtained by an oxidative chemical polymerization. In particular, different distribution of PEDOT according to the incorporation method was demonstrated.In the second part of this manuscript, the actuator behavior of electroemissive devices, that is predominantly induced by insertion or expulsion of ions during the redox process, was studied. A screening of ionic liquids with different chemical structures was carried out. The ion mechanism involved during the redox process was identified by a simple method consisting in observing the volume variation of the PEDOT active layer. This method highlighted the predominant role of cations in the redox process. The use of two ionic liquids allowed a considerable reduction of the actuator behavior of a reference electroemissive device while maintaining high optical properties in the infrared. Mixtures of ionic liquids and lithium salt were also studied. Depending on the lithium salt concentration, the possibility of controlling the ionic mechanism that governs the redox reaction was underlined. A salt concentration in particular leads to the succession of the two ionic mechanisms and results in a low actuator behavior while preserving the electro-activity and the optical properties of the system.In the last part of this manuscript, a prototype was evaluated for a thermal control application. Radiators based on electroemissive devices were fabricated and tested under conditions close to the space environment. These radiators were then compared to the technology currently used on artificial satellites, optical solar reflectors. Significant temperature changes (12 °C) were demonstrated, proving the relevance of this type of system for the thermal regulation of satellites. In addition, a low electrical consumption of these systems was highlighted during this work. Associated to a reduced on-board weight, the electroemissive devices designed at the LPPI, have thus a double interest for the intended application with respect to the current technology.

Anaerobic ammonium oxidation (anammox) by anammox bacteria contributes significantly to the global nitrogen cycle and plays a major role in sustainable wastewater treatment. To date, autotrophic nitrogen removal by anammox bacteria is the most efficient and environmentally friendly process for the treatment of ammonium in wastewaters; its application can save up to 60% of the energy input, nearly 100% elimination of carbon demand and 80% decrease in excess sludge compared to conventional nitrification/denitrification process. In the anammox process, ammonium (NH4+) is directly oxidized to dinitrogen gas (N2) using intracellular electron acceptors such as nitrite (NO2–) or nitric oxide (NO). In the absence of NO2– or NO, anammox bacteria can couple formate oxidation to the reduction of metal oxides such as Fe(III) or Mn(IV). Their genomes contain homologs of Geobacter and Shewanella cytochromes involved in extracellular electron transfer (EET). However, it is still unknown whether anammox bacteria have EET capability and can couple the oxidation of NH4+ with transfer of electrons to extracellular electron acceptors. In this dissertation, I discovered by using complementary approaches that in the absence of NO2–, freshwater and marine anammox bacteria couple the oxidation of NH4+ with transfer of electrons to carbon-based insoluble extracellular electron acceptors such as graphene oxide (GO) or electrodes poised at a certain potential in microbial electrolysis cells (MECs). Metagenomics, fluorescence in-situ hybridization and electrochemical analyses coupled with MEC performance confirmed that anammox electrode biofilms were responsible for current generation through EET-dependent oxidation of NH4+. 15N-labelling experiments revealed the molecular mechanism of the EET-dependent anammox process. NH4+ was oxidized to N2 via hydroxylamine (NH2OH) as intermediate when electrode was used as the terminal electron acceptor. Comparative transcriptomics analysis supported isotope labelling experiments and revealed an alternative pathway for NH4+ oxidation coupled to EET when electrode was used as electron acceptor. The results presented in my dissertation provide the first experimental evidence that marine and freshwater anammox bacteria can couple NH4+ oxidation with EET, which is a significant breakthrough that is promising in the context of implementing EET-dependent anammox process for energy-efficient treatment of nitrogen using bioelectrochemical systems.

<p>Soft actuators and sensors are currently used in many industrial applications due to their capability to produce an accurate response. Researchers have studied dielectric electroactive polymers (DEAPs) because these types of structures can be utilized as actuators and as sensors being able to convert electrical energy into mechanical and vice versa. However, production of this kind of structures is complex and in general involve several steps that are time consuming. Customization of these types of structures will be ideal to enhance the performance of the devices based on the specific application. 3D printing technologies have emerged as innovative manufacturing processes that could improve fabrication speed, accuracy, and consistency with low cost. This additive manufacturing technique allows for the possibility of increased device complexity with high versatility. </p> <p>This research studied the potential of 3D printing technologies to produce DEAPs, soft actuators, and flexible sensors. The study presents novel designs of these composite flexible structures, utilizing the most flexible conductive and nonconductive materials available for fused deposition modeling, achieving versatility and high performance in the produced devices. <a>Produced DEAP actuators showed an actuation and electric resistivity higher than other electroactive structures like shape memory alloys and ferroelectric polymers.</a> In addition, this research describes the electromechanical characterization of a flexible thermoplastic polyurethane, (TPU), produced by additive manufacturing, including measurement of the dielectric constant, percentage radial elongation, tensile proprieties, pre-strain effects on actuation, surface topography, and measured actuation under high voltage. DEAP actuators were produced with two different printing paths, concentric circles and lines, showed an area expansion of 4.73% and 5.71% respectively. These structures showed high resistance to electric fields having a voltage breakdown of 4.67 kV and 5.73 kV respectively. <a>Those results are similar to the resistant of the most used dielectric material “VHB 4910”. </a></p> <p>The produced soft pneumatic actuators were successfully 3D printed in one continuous process without support material. The structures were totally sealed without the use of any sealing material or post process. Computational simulations were made to predict the response of the designed structures under different conditions. These results were compared with experimental results finding that the theoretical model is able to predict the response of the printed actuators with an error of less than 7%. This error is satisfactorily small for modeling 3D printed structures and can be further minimized by characterization of the elastomeric material. Besides that, two different grippers were designed based on the opening and closing movements of single bellows actuators. The functionality of both designs was simulated and tested, finding that both designs are capable lifting a heavier rigid structure. </p> <p>Finally, this study presents a computational simulation of a 3D printed flexible sensor, capable of producing an output signal based on the deformation caused by external forces. Two different sensors were designed and tested, working based on a capacitance and resistance change produced by structural deformation. Computational analysis indicate the capacitance sensor should undergo change of capacitance from 3 to 8.5 pF when is exposed to 30 kPa; and the resistance sensor should experience an increase from 101.8 to 103 kΩ when is exposed to 30 kPa. </p>

Ionic polymer transducers (IPTs) are soft sensors and actuators which operate through a coupling of micro-scale chemical, electrical, and mechanical mechanisms. The use of ionic liquid as solvent for an IPT has been shown to dramatically increase transducer lifetime in free-air use, while also allowing for higher applied voltages without electrolysis. This work aims to further the understanding of the dominant mechanisms of IPT actuation and how these are affected when an ionic liquid is used as solvent. A micromechanical model of IPT actuation is developed following a previous approach given by Nemat-Nasser, and the dominant relationships in actuation are demonstrated through an analysis of electrostatic cluster interactions. The elastic modulus of Nafion as a function of ionic liquid uptake is measured using uniaxial tension tests and modeled in a micromechanical framework, showing an excellent fit to the data. Charge transport is modeled by considering both the cation and anion of the ionic liquid as mobile charge carriers, a phenomenon which is unique to ionic liquid IPTs as compared to their water-based counterparts. Numerical simulations are performed using the finite element method, and a modified theory of ion transport is discussed which can be extended to accurately describe electrochemical migration of ionic liquid ions at higher applied voltages. The results presented here demonstrate the dominant mechanisms of IPT actuation and identify those unique to ionic liquid IPTs, giving directions for future research and transducer development. / Master of Science

La Fabrication Additive (FA) est un procédé de fabrication qui a commencé à se développer dans les années 80 et qui atteint actuellement une maturité qui lui permet d’être utilisé de manière rentable et fonctionnelle par les industriels. La fabrication additive est définie comme étant le procédé de mise en forme d’une pièce par ajout de matière, à l’opposé de la mise en forme traditionnelle par enlèvement de matière (usinage). Cette nouvelle technologie est une réelle révolution et permet de relever de nouveaux défis technologiques sans précédent. Que ce soit sur un axe matériau ou plus largement dans le cadre de l’usine du futur, la fabrication additive est un réel levier de croissance, mais de nombreux travaux de recherche sont encore à mener afin de perfectionner cette nouvelle technologie. C’est autour de cette problématique que les travaux de thèses se sont focalisés avec un accent sur l’intégration de matériaux électroactifs pour la réalisation de fonction mécatronique tirant profit des procédés de Fabrication Additive. Les actions de recherche montrent que la fabrication additive de matériaux électroactifs sera de plus en plus employée pour la réalisation de fonctions mécatroniques hybrides qui combineront à la fois la structure mécanique, des circuits intégrés en silicium, des pistes conductrices et des matériaux couplés imprimés, intégrant ainsi des fonctionnalités, telles que des capteurs, des affichages ou des sources d’énergie. Les travaux montrent le potentiel applicatif autour du contrôle de santé des structures en composites, mais aussi du contrôle de forme d’instrument pour la chirurgie. Pour arriver au développement de ces dispositifs, les points suivants ont été développés autour des matériaux électroactifs et de leurs règles d’intégrations et d’optimisation. / Additive Manufacturing (FA) is a manufacturing process that began to develop in the 1980s and is now mature enough to be used in a cost-effective and functional way by manufacturers. Additive manufacturing is defined as the process of shaping a part by adding material, as opposed to traditional shaping by material removal (machining). This new technology is a real revolution and enables us to meet new unprecedented technological challenges. Whether on a material axis or more widely as part of the plant of the future, additive manufacturing is a real growth driver, but many research work is yet to be conducted to perfect this new technology. It is around this issue that the work of theses focused with a focus on the integration of electroactive materials for the realization of mechatronics function taking advantage of Additive Manufacturing processes. Research shows that additive manufacturing of electroactive materials will be increasingly used for the realization of hybrid mechatronic functions that will combine both the mechanical structure, silicon integrated circuits, conductive tracks and printed coupled materials, integrating as well as features, such as sensors, displays or power sources. The work shows the potential application around the health control of composite structures, but also the instrument shape control for surgery. To arrive at the development of these devices, the following points have been developed around electroactive materials and their integration and optimization rules.

Directing differential cellular response by manipulating the physical characteristics of the material is regarded as a key challenge in biomaterial implant design and tissue engineering. In developing various biomaterials, the influence of substrate properties, like surface topography, stiffness and wettability on the cell functionality has been investigated widely. However, such study to probe into the influence of substrate conductivity on cell fate processes is rather limited. The need for such an understanding is based on the fact that specific tissues in the body are electrically active in nature, such as in brain, heart and skeletal muscle. These tissues make use of electrical conductivity as an effective cue for tissue homeostasis, development, regeneration and so on. Moreover, understanding the importance of underlying conductivity in basic biological processes is essential in developing electrically conductive biomaterials with the ability to simulate normal electrophysiology of the body by interfacing with bioelectric fields in cells and tissues. Electrical stimulation and charge conduction can regulate numerous intracellular signalling pathways, can interact with cytoskeleton proteins to modulate the morphology, increase protein synthesis and on the more can favor the ECM protein conformational changes. On these grounds, the present dissertation illustrates that persistent electrical activation influences the multipotency of hMSCs and acts like a promoter towards selective differentiation of hMSCs into neural/cardiomyogenic or osteogenic lineage. Besides, continual exposure to electric field stimulated conducting culture environments lead to growth arrest while enhancing differentiation. In total, this dissertation suggests the dominant role of conductivity in inducing my oblast differentiation and hMSc lineage commitment that involves EF stimulated in vitro culture conditions. Also, a knowledge base with qualitative and quantitative understanding of stem cells and their response to substrate physical properties and external field effect was developed through this comprehensive study. Such an improved understanding of the ability of hMSCs in sensing electrical conductivity may lead to the development of culture additives/conditions that better induce directed stem cell differentiation.

Elektroakustische Systeme wie Lautsprecher, die elektrische Signale in akustische Signale umwandeln, sind heute Eckpfeiler der Kommunikation. Von Mikrotreibern in Kopfhörern und Smartphones über Audiosysteme in Fahrzeugen und Wohnzimmern bis hin zu großen Beschallungsanlagen in öffentlichen Räumen, Kinos und Konzerten sowie zahlreichen technischen Anwendungen sind sie heute ein allgegenwärtiger Bestandteil des täglichen Lebens. Die gängigsten Lautsprechertechnologien basieren auf elektrodynamischen Wandlern. Seit der ersten Patentierung vor 145 Jahren wurden diese, die notwendige Leistungselektronik sowie die Methoden zur Auslegung und Systembeschreibung im Klein- und Großsignalbereich kontinuierlich weiterentwickelt. Die Forschung befasst sich aber auch ständig mit alternativen Technologien, die Vorteile gegenüber konventionellen Antrieben haben können. In diesem Zusammenhang haben dielektrische Elastomere (DE) in den letzten 25 Jahren zunehmend an Aufmerksamkeit gewonnen. Sie versprechen u.a. einen höheren Wirkungsgrad, neuartige Konstruktionen und eine erhebliche Gewichtsreduktion. Zudem können sie aus kostengünstigen Ausgangsmaterialien ohne den Einsatz von Seltenen Erden oder ferroelektrischen Materialien hergestellt werden, was die Abhängigkeit von Rohstoffimporten verringert und neue Anwendungsfelder eröffnet. Trotz sehr aktiver Forschung und Entwicklung bei Materialien, Design und Herstellung gibt es bisher nur wenige kommerziell verfügbare Aktuatoranwendungen. Eine grundlegende Voraussetzung für die Etablierung einer Technologie sind standardisierte und nachvollziehbare Methoden zur prädiktiven Systembeschreibung und zum rechnergestützten Systementwurf. Diese sind für DE in dynamischen Anwendungen noch nicht verfügbar. In dieser Arbeit wird die etablierte Entwurfsmethodik zur prädiktiven Beschreibung kleinsignaliger dynamischer Systeme mit elektromechanischen und akustischen Netzwerken auf dielektrische Elastomere erweitert. Das Kernelement ist die Ableitung der elektromechanischen Wandlermodelle für DE-Längs- und Dickenoszillatoren. Basierend auf dieser Systembeschreibung, werden Auslegungskriterien für DE-basierte Schallquellen aufgestellt. Der Fokus liegt dabei auf der praktischen Anwendbarkeit und der Generierung von technologischen Vorteilen gegenüber elektrodynamischen Wandlern. Aus diesen Kriterien werden neuartige Wandlerkonzepte in Form von rollenaktorgetriebenen Lautsprechermembranen und unimorphen Membranen entwickelt, analysiert und als Demonstratoren realisiert. Darüber hinaus wird die Leistungselektronik untersucht, auf deren Basis Schaltungen zur Durchführung messtechnischer Untersuchungen und zum Betrieb der Demonstratoren entwickelt und realisiert wurden. Ziel der Arbeit ist es, Anwendungsentwicklern mit der vorgestellten Entwurfsmethodik einen besseren Zugang zur Technologie zu ermöglichen und so zur Entwicklung von DE-basierten Schallquellen im Speziellen und dynamischen DE-Aktoren im Allgemeinen beizutragen.:1 Introduction 1 2 Fundamentals of Dielectric Elastomers 5 3 Electromechanical Network Model of Dielectric Elastomers 9 3.1 Transducer Network Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.1 Electrostatic Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.1.2 Simulative-experimental Validation . . . . . . . . . . . . . . . . . . . . . . 14 3.1.3 Mechanical Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.1.4 Determination of the Parameters at the Operating Point . . . . . . . . . 19 3.1.5 Electromechanical Transducer Model . . . . . . . . . . . . . . . . . . . . . 23 3.2 Electrical Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.3 Operating Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.4 Mechanical Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4 Power Electronics 37 4.1 Fundamental Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2 Alternative Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 4.2.1 Adapted Circuit Designs for Capacitive Loads . . . . . . . . . . . . . . . . 39 4.2.2 Summing Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.3 Realization of Power Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.3.1 Coupling Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.3.2 Branch to Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.3.3 Charging Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.3.4 Additional Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.3.5 Implemented Power Electronics . . . . . . . . . . . . . . . . . . . . . . . . 46 5 Design of DE Loudspeakers 49 5.1 State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.1.1 Membrane and Bubble-Loudspeakers . . . . . . . . . . . . . . . . . . . . 49 5.1.2 Annular Membrane Actuators . . . . . . . . . . . . . . . . . . . . . . . . . 52 5.1.3 Preformed Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 5.1.4 Thickness Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 5.2 Fundamental Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.3 Proposed Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 6 DE-Roll Actuator based Loudspeaker Driver 61 6.1 Fundamentals of DERA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 6.2 Stability Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6.3 Model Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 6.3.1 Fundamental Implementation . . . . . . . . . . . . . . . . . . . . . . . . . 65 6.4 Construction and Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 6.4.1 PolyPower Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 VTable of Contents 6.4.2 Elastosil Actuator Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . 77 6.4.3 Overview of Manufactured Actuators . . . . . . . . . . . . . . . . . . . . . 78 6.5 Measurement Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6.5.1 Static Function Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 6.5.2 Electrical Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.5.3 Dynamic Electromechanical Measurements . . . . . . . . . . . . . . . . . 83 6.6 Electromechanical Test Results and Model Updating . . . . . . . . . . . . . . . . 85 6.7 Radial Actuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 6.8 Acoustic Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.8.1 Acoustic Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.8.2 Selection of loudspeaker diaphragm . . . . . . . . . . . . . . . . . . . . . 92 6.8.3 Loudspeaker in Closed Cabinet . . . . . . . . . . . . . . . . . . . . . . . . . 96 6.8.4 Loudspeaker in Vented Cabinet . . . . . . . . . . . . . . . . . . . . . . . . 98 6.8.5 Bending Wave Transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.9 Acoustic Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.10 Demonstrator Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.11 Considerations towards Large-Signal Behaviour . . . . . . . . . . . . . . . . . . . 112 7 Dielectric Elastomer Unimorph Membrane 115 7.1 Membrane Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 7.2 Model-based Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.3 Headphones demonstrator construction . . . . . . . . . . . . . . . . . . . . . . . 119 7.4 Measurements and Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 8 Summary and Outlook 129 Appendix 133 A ANSYS APDL simulation code for DE elementary cell model . . . . . . . . . . . . 136 B Additional comparisons of measurement and simulation data . . . . . . . . . . 138 / Electroacoustic systems such as loudspeakers, which convert electrical signals into acoustic signals, are nowadays cornerstones of communication. From microdrivers in headphones and smartphones, to audio systems in vehicles and living rooms, to large sound reinforcement systems in public spaces, cinemas and concerts, as well as numerous technical applications, they are nowadays a ubiquitous part of everyday life. The most common loudspeaker technologies are based on electrodynamic transducers. Since the first patent 145 years ago, they, the necessary power electronics as well as the methods for design and system description in the small- and large- signal range have been continuously developed. However, research is also constantly looking at alternative technologies that may have advantages over conventional drives. In this context, dielectric elastomers (DE) have gained increasing attention over the past 25 years. They promise, among other things, higher efficiency, novel designs and considerable weight reduction. Moreover, they can be manufactured from inexpensive starting materials without the use of rare-earths elements or ferroelectric materials, which reduces the dependence on raw materials imports and opens up new fields of application. Despite very active research and development of materials, designs and fabrication, there are only few commercially available actuator applications so far. A fundamental requirement for the establishment of a technology are standardized and comprehensible methods for predictive system description and for computer-aided system design. These are not yet available for DE in dynamic applications. In this work, the established design methodology for the predictive description of smallsignal dynamic systems using electromechanical and acoustic networks is being extended to dielectric elastomers. The core element is the derivation of the electromechanical transducer models for DE longitudinal and thickness oszillators. Based on this system description, design criteria for DE based sound sources are established. The focus lies on practical applicability and the generation of technological advantages compared to electrodynamic transducers. From these criteria, novel transducer concepts in the form of roll actuator driven loudspeaker diaphragms and unimorph membranes are developed, analyzed and realized as demonstrators. In addition, the power electronics are examined, on the basis of which circuits for carrying out metrological investigations and for operating the demonstrators were developed and implemented. The goal of the work is to provide application developers with better access to the technology using the presented design methodology and thus contribute to the development of DE-based sound sources in particular and dynamic DE actuators in general.:1 Introduction 1 2 Fundamentals of Dielectric Elastomers 5 3 Electromechanical Network Model of Dielectric Elastomers 9 3.1 Transducer Network Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.1 Electrostatic Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.1.2 Simulative-experimental Validation . . . . . . . . . . . . . . . . . . . . . . 14 3.1.3 Mechanical Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.1.4 Determination of the Parameters at the Operating Point . . . . . . . . . 19 3.1.5 Electromechanical Transducer Model . . . . . . . . . . . . . . . . . . . . . 23 3.2 Electrical Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.3 Operating Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.4 Mechanical Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4 Power Electronics 37 4.1 Fundamental Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2 Alternative Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 4.2.1 Adapted Circuit Designs for Capacitive Loads . . . . . . . . . . . . . . . . 39 4.2.2 Summing Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.3 Realization of Power Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.3.1 Coupling Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.3.2 Branch to Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.3.3 Charging Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.3.4 Additional Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.3.5 Implemented Power Electronics . . . . . . . . . . . . . . . . . . . . . . . . 46 5 Design of DE Loudspeakers 49 5.1 State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.1.1 Membrane and Bubble-Loudspeakers . . . . . . . . . . . . . . . . . . . . 49 5.1.2 Annular Membrane Actuators . . . . . . . . . . . . . . . . . . . . . . . . . 52 5.1.3 Preformed Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 5.1.4 Thickness Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 5.2 Fundamental Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.3 Proposed Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 6 DE-Roll Actuator based Loudspeaker Driver 61 6.1 Fundamentals of DERA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 6.2 Stability Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6.3 Model Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 6.3.1 Fundamental Implementation . . . . . . . . . . . . . . . . . . . . . . . . . 65 6.4 Construction and Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 6.4.1 PolyPower Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 VTable of Contents 6.4.2 Elastosil Actuator Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . 77 6.4.3 Overview of Manufactured Actuators . . . . . . . . . . . . . . . . . . . . . 78 6.5 Measurement Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6.5.1 Static Function Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 6.5.2 Electrical Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.5.3 Dynamic Electromechanical Measurements . . . . . . . . . . . . . . . . . 83 6.6 Electromechanical Test Results and Model Updating . . . . . . . . . . . . . . . . 85 6.7 Radial Actuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 6.8 Acoustic Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.8.1 Acoustic Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.8.2 Selection of loudspeaker diaphragm . . . . . . . . . . . . . . . . . . . . . 92 6.8.3 Loudspeaker in Closed Cabinet . . . . . . . . . . . . . . . . . . . . . . . . . 96 6.8.4 Loudspeaker in Vented Cabinet . . . . . . . . . . . . . . . . . . . . . . . . 98 6.8.5 Bending Wave Transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.9 Acoustic Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.10 Demonstrator Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.11 Considerations towards Large-Signal Behaviour . . . . . . . . . . . . . . . . . . . 112 7 Dielectric Elastomer Unimorph Membrane 115 7.1 Membrane Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 7.2 Model-based Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.3 Headphones demonstrator construction . . . . . . . . . . . . . . . . . . . . . . . 119 7.4 Measurements and Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 8 Summary and Outlook 129 Appendix 133 A ANSYS APDL simulation code for DE elementary cell model . . . . . . . . . . . . 136 B Additional comparisons of measurement and simulation data . . . . . . . . . . 138

La pile à combustible apparaît comme une technologie prometteuse pour la conversion énergétique à faible impact environnemental mais sa commercialisation à grande échelle nécessite de relever certains défis économiques et technologiques. Tout d'abord, pour fonctionner, la pile a besoin de systèmes (compresseurs, convertisseurs,...) parfois volumineux et coûteux en énergie. Ensuite, le prix de certains éléments constituants la pile reste élevé car ce sont des produits à haute valeur technologique utilisant des matériaux parfois très onéreux (membrane polymère, couche catalytique,...). L'optimisation du système pile à combustible et des éléments environnants n'est pas le seul défi à relever. En effet, la durabilité des assemblages membrane-électrodes (AME) constitue une barrière majeure à la commercialisation de ces systèmes pour des applications stationnaires ou dans les transports. Afin d'améliorer la durabilité de ces assemblages, il est nécessaire de bien caractériser les différents éléments les constituant et de déterminer et de quantifier les mécanismes de dégradation. Le premier chapitre de cette thèse présente une étude bibliographique sur les PEMFC et l'électrochimie fondamentale régissant le fonctionnement de ces systèmes. Le second chapitre présente les matériaux composant les différents éléments du système ainsi que les méthodes expérimentales utilisées pour caractériser les AME. Le chapitre suivant évoque l'étude et la mise en oeuvre d'une technique électrochimique de caractérisation d'un empilement, notamment la mesure de surface active des différentes cellules. Enfin, le quatrième et dernier chapitre concerne une étude du vieillissement hétérogène d'empilements de trois cellules / Proton exchange membrane (PEM) fuel cells are seen as a promising technology for environmentally friendly energy conversion but its wide spread commercialization need taking up several technological and economic challenges. First, to operate PEM fuel cells require sizeable and energy consuming surrounding systems (compressors, converters,...). Then, elements constituting the cell remain costly because with high technological value and using expensive materials (polymer membrane, catalyst layer,...). The optimization of the system and the surrounding elements is not the only challenge to take up. Indeed, durability of the membrane electrode assembly (MEA) constitutes the major barrier to commercialization of these systems for stationary or transport applications. In order to increase durability of the assemblies, a better understanding of the aging mechanisms is necessary. The first chapter of the thesis introduces a bibliographical study on PEMFC and the fundamental electrochemistry governing the system operation. The second chapter introduces materials composing the different system elements and experimental methods used for PEMFC characterization. The next chapter deals with a study on stack characterization, particularly the development of an electrochemical technique allowing active surface area measurement of the cells composing the stack. Finally, the last chapter deals with heterogeneous aging within PEMFC stacks

Electroactive polymers are a class of materials capable of reallocating their shape in response to an electric field while also having the ability to harvest electrical energy when the materials are mechanically deformed. Electroactive polymers can therefore be used as sensors, actuators, and energy harvesters. The parameters for manufacturing flexible electroactive polymers are complex and rate limiting due to number of steps, their necessity, and time intensity of each step. Successful additive manufacturing processes for electroactive polymers will allow for scalability and flexibility beyond current limitations, advancing the field, opening additional manufacturing possibilities, and increasing output. The goal for this research was to use additive manufacturing techniques to print conductive and dielectric substrates for building flexible circuits and sensors. Printing flexible conductive layers and substrates together allows for added creativity in design and application.