Dielectric elastomers (DEs) are a relatively new electroactive polymer (EAP) transducer technology. They are capable of over 100% strain when actuated, and can be used as sensors to measure large strains. In actuation mode, the DE is subject to an electric field; in sensing mode, the capacitance of the dielectric elastomer is measured. In this work, a dielectric elastomer configured as a circular membrane clamped around its outer edge over a sealed chamber and inflated by a bias pressure is studied in order to characterize its static and dynamic electromechanical behavior. In both cases, the experiments were conducted with prestretched dielectric elastomer actuators fabricated from 0.5 mm or 1 mm thick polyacrylate films and unless stated otherwise carbon grease electrodes were used. The static tests investigate the effect of flexible electrodes and passive layers on the electromechanical response of dielectric elastomer membrane actuators and sensors. To study the effect of the flexible electrodes, four compliant electrodes were tested: carbon grease, silver grease, graphite spray, and graphite powder. The electrode experiments show that carbon grease is the most effective electrode of those tested. To protect the flexible electrodes from environmental hazards, the effect of adding passive elastic layers to the transducers was investigated. A series of tests were conducted whereby the position of the added layers relative to the transducer was varied: (i) top passive layer, (ii) bottom passive layer, and (iii) passive layers on both the bottom and top of the transducer. For the passive layer tests, the results show that adding elastic layers made of the same material as the DE dramatically changes both the mechanical and electrical response of the actuator. The ability to use capacitance measurements to determine the membrane's maximum stretch was also investigated. The experiments demonstrate that the capacitance response can be used to sense large mechanical strains in the membrane ï ³ 25%. In addition, a numerical model was developed which correlates very well with the experimental results especially for strains up to 41%. The dynamic experiments investigate the dynamic response of a dielectric elastomer membrane due to (i) a time-varying pressure input and (ii) a time-varying voltage input. For the time-varying pressure experiments, the prestretched membrane was inflated and deflated mechanically while a constant voltage was applied. The membrane was cycled between various predetermined inflation states, the largest of which was nearly hemispherical, which with an applied constant voltage of 3 kV corresponded to a maximum strain at the pole (center of membrane) of 28%. These experiments show that for higher voltages, the volume displaced by the membrane increases and the pressure inside the chamber decreases. For the time varying voltage experiments, the membrane was passively inflated to various predetermined states, and then actuated. Various experiments were conducted to see how varying certain system parameters changed the membrane's dynamic response. These included changing the chamber volume and voltage signal offset, as well as measuring the displacement of multiple points along the membrane's radius in order to capture its entire motion. The chamber volume experiments reveal that increasing the size of the chamber onto which the membrane is clamped will cause the resonance peaks to shift and change in number. For these experiments, the pole strains incurred during the inflation were as high as 26 %, corresponding to slightly less than a hemispherical state. Upon actuation using a voltage signal with an amplitude of 1.5 kV, the membrane would inflate further, causing a maximum additional strain of 12.1%. The voltage signal offset experiments show that adding offset to the input signal causes the membrane to oscillate at two distinct frequencies rather than one. Lastly, experiments to capture the entire motion of the membrane revealed the different mode shapes the membrane's motion resembles. / Master of Science

Ein Dielektrischer Elastomer Aktuator (DEA) ist ein dehnbarer Kondensator, der aus einem Elastomerfilm besteht, der sich zwischen zwei flexiblen Elektroden befindet. Bei Anlegen einer elektrischen Spannung, ziehen sich die Elektroden aufgrund elektrostatischer Wechselwirkungen an, wodurch das Elastomer in z-Richtung zusammengepresst wird und sich dementsprechend in der x-,y-Ebene ausdehnt. Hierdurch werden Aktuationsbewegungen erreicht, welche sehr präzise über die Spannung gesteuert werden können. Zusätzlich sind DEAs kostengünstig, leicht und aktuieren geräuschlos. DEAs können beispielsweise für Produkte im medizinischen Bereich oder für optischer Komponenten genutzt werden. Ebenso kann aus diesen Bauteilen Strom erzeugt werden. Das größte Hindernis für eine weite Implementierung dieser Materialien liegt in den erforderlichen hohen Spannungen zum Erzeugen der Aktuationsbewegung, welche sich tendenziell im Kilovolt-Bereich befinden. Dies macht die Elektronik teuer und die Bauteile unsicher für Anwender. Um geringere Betriebsspannungen für die DEAs zu erreichen, sind signifikante Materialverbesserungen - insbesondere des verwendeten Elastomers - erforderlich. Um dies zu erreichen, können die dielektrischen Eigenschaften (Permittivität) der Elastomere gesteigert und/oder deren Steifigkeit (Young-Modul) gesenkt werden. In der vorliegenden Arbeit konnte die Aktuationsleistung von Silikonfilmen durch die Addition organischer Dipole erheblich verbessert werden. Hierfür wurde ein Verfahren etabliert, um funktionalisierte Dipole kovalent an das Polymernetzwerk zu binden. Dieser als "One-Step-Verfahren" bezeichnete Ansatz ist einfach durchzuführen und es werden homogene Filme erhalten. Die Dipoladdition wurde anhand verschiedener Silikone erprobt, die sich hinsichtlich ihrer mechanischen Eigenschaften unterschieden. Bei maximalem Dipolgehalt verdoppelte sich die Permittivität aller untersuchten Silikone und die Filme wurden deutlich weicher. Hierbei war festzustellen, dass die Netzwerkstruktur der verwendeten Silikone einen erheblichen Einfluss auf die erreichte Aktuationsdehnung hat. Abhängig vom Netzwerk erfolgte eine enorme Steigerung der Aktuationsleistung im Bereich von 100 % bis zu 4000 %. Dadurch können die Betriebsspannungen in DEAs deutlich abgesenkt werden, so dass sie tendenziell bei Spannungen unterhalb von einem Kilovolt betrieben werden können. / Dielectric elastomer actuators (DEAs) are compliant capacitors consisting of an elastomer film between two flexible electrodes. When a voltage is applied the electrostatic attraction of the electrodes leads to a contraction of the polymer in the z-direction and to a corresponding expansion in the x,y-plane. DEAs show high actuation strains, which are very accurate and adjustable by the applied voltage. In addition these devices are low-cost, low-weight and the actuation is noise-free. DEAs can be used for medical applications, optical components or for energy harvesting. The main obstacle for a broad implementation of this technology is the high driving voltage, which tends to be several thousand volts. For this reason the devices are unsafe for users and the needed electronic components are expensive. A significant improvement of the materials - especially of the used elastomer - is necessary to lower the actuation voltages. This can be achieved by improving the dielectric properties (permittivity) of the elastomer and/or by lowering it's stiffness (Young's modulus). In this work the actuation performance of silicone lms was improved significantly by the addition of organic dipoles. A simple procedure was developed, in which functionalized dipoles were bound to the polymer matrix, leading to homogenous and transparent films. This so-called "one-step-film-formation" was tested on various silicones with different mechanical properties. For the highest dipole content the permittivity of all tested silicones was doubled and the modified films showed a substantially lower stiffness. It was proven that the structure of the macromolecular network has a clear impact on the achievable actuation properties. For the highest dipole contents the actuation performance increased remarkably by 100 % up to 4000 % in respect to the investigated network. The addition of organic dipoles to the elastomer enables a signicant reduction of the needed driving voltage for DEAs below one kilovolt.

Récupérer l'énergie mécanique ambiante est une alternative prometteuse afin d'assurer l'autonomie énergétique d'appareils nomades. Le développement des générateurs électrostatiques souples reste toutefois à ce jour anecdotique du fait des hautes tensions de polarisation employées, de la nécessité de grandes déformations mécaniques mais aussi de l'utilisation de matériaux peu conventionnels et mal caractérisés. Le but de cette thèse est d'apporter des avancées scientifiques et des solutions aux verrous technologiques précités. Tout d'abord, une caractérisation rigoureuse des propriétés électriques et mécaniques de deux matériaux communément utilisés pour ces applications (acrylate VHB 4910 et silicone Polypower) nous a donné accès aux propriétés physiques dans un fonctionnement réel de ces polymères : influence de la précontrainte, de la nature des électrodes... Ces données ont permis d'élaborer des lois analytiques fiables que nous avons ensuite insérées dans un modèle thermodynamique permettant de définir avec précision les puissances et densités d'énergie récupérables pour ces générateurs. Des pistes d'amélioration des matériaux utilisés dans les applications générateurs peuvent être dégagées de notre modèle. Le second verrou à lever concerne la source haute tension de polarisation nécessaire à ces générateurs électrostatiques. Pour cela, nous avons proposé une solution innovante couplant l'élastomère diélectrique à un électret. Différentes configurations de générateurs hybrides dans des géométries 2D et 3D ont été évaluées. Enfin, nous avons réalisé un prototype qui a délivré une puissance de l'ordre de 35µW sachant qu'une optimisation de ce prototype est réalisable et que des puissances récupérées de plusieurs centaines de µW sont tout à fait réalistes. / Scavenging mechanical ambient energy is a promising solution to ensure the autonomy of wearable transducers. Nevertheless, the development of soft electrostatic generator (DEG) is up to now slow down due to the use of high bias voltage, high strain and innovative mischaracterized materials. The aim of this Ph-D thesis is to propose innovative solutions to these technological barriers. Firstly, a complete characterization of the electrical and mechanical properties of two commonly used dielectric polymer (acrylate VHB 4910 and silicone Polypower) has revealed the true physical properties of these polymers and especially the influence of the pre-stress and the nature of the electrode used. Thanks to these data, reliable analytic laws have been proposed and inserted into our thermodynamic model in order to predict the output power and scavenged energy density for the DEG. Moreover, our model allow us to propose improvements for the materials used in these applications. The second challenge is to propose an alternative to the high bias voltage needed for these soft generators. We have proposed an innovative solution combining an electret and a dielectric elastomer. Various configurations of hybrid generators in 2D or 3D geometry have been modelled and evaluated. Finally, a prototype has been designed allowing scavenging 35µW. With an appropriate optimization of our prototype, hundreds of µW can be scavenged.

Precise manipulation of heterogeneous droplets on an open droplet microfluidic platform could have numerous practical advantages in a broad range of applications, from proton exchange membrane (PEM) fuel cells and microreactors, to medical diagnostic platforms capable of assaying complex biological analytes. Toward the aim of developing electrically controllable micropost arrays for use in open droplet manipulation, custom-designed titanium dioxide (TiO2)- loaded poly(dimethylsiloxane) (PDMS) micropost arrays were developed in this work and indirectly mechanically actuated by applying an electric field. Initial experiments explored the bulk properties of TiO2-loaded PDMS films, with scanning electron microscopy (SEM) confirming a uniform TiO2 particle distribution in the PDMS, and tensile testing of bulk films showing an inverse relationship between TiO2 % (w/w) and Young’s Modulus with the Young’s Moduli quantified as 4.22 ± 0.51 MPa for unloaded PDMS, 2.27 ± 0.18 MPa for 10 % (w/w) TiO2, and 1.39 ± 0.20 MPa for 20 % (w/w) TiO2. Following bulk material evaluation, soft lithography methods were developed to fabricate TiO2- loaded PDMS micropost arrays. Mathematical predictions were applied to design microposts of varying shape, length, and gap spacing to yield super-hydrophobic surfaces actuatable by an electric field. Visual inspection and optical microscopy of the resulting arrays confirmed a non- collapsed micropost geometry. Overall, round microposts that were 100, 200, and 300 μm in length, 15 μm in diameter, and spaced 50 μm apart were produced largely free of defects, and used in contact angle measurements and micropost deflection experiments. Droplet contact angles measured on the arrays remained above 120° indicating the arrays successfully provided super- hydrophobic surfaces. Individual microposts deflected most notably above an electric field strength of 520 kV/m (12.5 kV nominal voltage). The ability to mechanically deflect customized microposts using an electric field demonstrated by this work is promising for translating this technology to precise droplet manipulation applications. Indirect actuation of droplets could enable the manipulation of liquids with varying electrical properties, which is a limitation of current micropumping technologies. Once optimized, electrically actuated micropost arrays could significantly contribute to the micro- handling of heterogeneous, highly ionic, and/or deionized fluids. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-03-03 17:25:49.785

Les élastomères diélectriques sont de plus en plus utilisés pour la réalisation des transducteurs dans de nombreux domaines industriels : interface haptique, robotique, biomimétisme, conversion d’énergie. Pour le fonctionnement de toutes ces applications, le polymère électroactif est soumis à une haute tension (de 1 à 10kV). Toutefois, le courant de fuite diminue l’efficacité et la durée de vie des dispositifs utilisant ces matériaux.Par ailleurs, une précontrainte mécanique (étirement) est généralement appliquée au polymère pour accroître l’efficacité énergétique dans la conversion mécanique-électrique. Les courants de fuite (et donc le champ de claquage du polymère) seront ainsi conditionnés par cette précontrainte et ce point doit faire l’objet d’une étude détaillée.L’objet de ce travail de thèse est de mener des analyses de courant de fuite sur des polymères électroactifs (élastomères polyacrylates du commerce VHB4910 et silicones Sylgard 186) non contraints et contraints mécaniquement pour évaluer l’amélioration ou la dégradation des performances électriques lorsqu’ils seront plus tard intégrés en géométrie électrode-polymère-électrode dans des transducteurs.Tout d’abord, nous avons mené une étude exhaustive sur l’influence des facteurs externes (étirement, température, champ électrique, nature de l’électrode) sur les propriétés électriques du polyacrylate VHB4910. Les études ont été réalisés sur des durées de polarisation courtes (quelques minutes) et longues (jusqu’à 15 heures). Au cours de ce travail, nous sommes également intéressés à l’étude du phénomène d’autocicatrisation sur le sylgard 186. Les tests ont été conduits pour différents types d’électrodes (or, aluminium, graphène, nanoplaquettes de graphène : GnP) déposées sur la surface de silicone. Une analyse par microscopie optique de la zone évaporée a été menée.La finalité de ces travaux aura permis d’optimiser des structures de récupération d’énergie électrostatique à base de polymères électroactifs. / Electroactive polymers known as dielectric elastomers have shown considerable promise for transducers. They are attractive for a wide range of innovative applications including softs robots, adaptive optics, haptic interface or biomedical actuation thanks to their high energy density and good efficiency. For the functioning of all these application, the electroactive polymer is subjected to high electrical field. Nevertheless, the performances of these transducers are affected by the losses and especially the ones induced by the leakage current.Mechanical pre-stretch is an effective method to improve actuation when a voltage is applied to the device made up of a dielectric elastomer sandwiched between two compliant electrodes. The overall performances of the structure (electromechanical conversion, efficiency, strain induced…) depend strongly on the electric and mechanical properties of the elastomer. Regarding electric characteristics, dielectric permittivity, dissipation factor and electric breakdown field have been deeply investigated according to various parameters such as frequency, temperature, pre-stretch, or nature of the electrodes but complete analysis of the leakage current is missing in the scientific literature.Thus, this work reports an extensive investigation on the stability of the current-time characteristics in dielectric elastomer. Particularly, we focus on the influence of the nature of the electrodes and pre-stress applied to the transducer. In order to evaluate the influence of the time duration on the behavior of the leakage current, short and long-term electrical stress times was applied during short times and up to 15 hours.Leakage current in electroactive polymers were discussed for a commercial polyacrylate (VHB4910 from 3M) currently used for soft transducers applications. This current is investigated as a function of external factors (stretching, temperature, type of material for electrodes)In order to evaluate the limitations in term of voltage and in the goal to increase the lifetime of these transducers, the second part of our study is focused on the dielectric strength of silicone rubbers for various types of electrodes (gold, Aluminum, graphene nanoplatelets, graphene : GnP). The effect of self-healing is particularly studied and a selection of electrodes for soft transducers based on dielectric elastomers is proposed.

There is a huge demand for low-cost and compact laser devices in particular for point-of-care diagnostic, sensing, or optical communication. Organic solid-state lasers (OSLs) have a great potential to fill that gap due to their specific properties such as high optical gain, low lasing threshold, and spectral tunability. To miniaturize OSLs for micro-optical circuits two aspects are required: The spectrum of the laser should be easily tunable, and the pumping energy should be provided in a simple and compact method, in the best case electrically. In this work, we developed a simple, compact, easy to manufacture, and electrically tunable laser resonator using electroactive polymers. The cavity is formed between a highly reflecting distributed Bragg reflector (DBR) and a highly reflecting silver layer sandwiching a soft elastomer layer. A transparent electrode made by indium tin oxide is placed on the glass substrate below the DBR. If an external voltage between the transparent bottom electrode and the metal layer is applied, the elastomer layer is compressed by the electrostatic pressure, which leads to a blue shift of the optical modes of the microcavity. If an active material with a broad emission spectrum, such as organic molecules, is included inside the cavity layer, it enables the development of an electrically tunable OSL. Hence, we demonstrate a cost-effective approach towards an electrically tunable organic laser source particularly suitable for easily processable lab-on-chip devices. In the second part, a novel organic light emitting diode (OLED) architecture is realized enabling high current densities with low optical losses in the prospect of the realization of an electrically driven OSL. For this purpose, an additional highly conductive lateral transport layer (LTL) is introduced to achieve expansion of the charge recombination to the electrode-free area. Simulations by equivalent circuit approach allow for an analysis of the lateral distribution of the vertical current density to predict the lateral current density distribution in the high excitation regime (current densities ≈ 1 kA/cm² ). Moreover, the Joule heating of the device is reduced by restructuring the OLED layer stack. Thus, high current densities close to the predicted lasing threshold of 1 kA/cm² could be achieved. The results of the thesis presenting a significant step towards the development of an electrical pumped OSL.:1 Introduction 2 Theoretical Background 2.1 Optical Cavities 2.1.1 Fabry-Perot Resonator 2.1.2 Transfer Matrix Algorithm 2.1.3 Distributed Bragg Reflector 2.1.4 Optical Microcavities 2.1.5 Tunable Optical Cavities 2.2 Organic Semiconductors 2.2.1 Properties 2.2.2 Electronic Structure 2.2.3 Absorption and Emission Spectra 2.2.4 Electrical Current 2.2.5 Doping 2.3 Organic Light Emitting Diodes 2.3.1 Basic OLED 2.3.2 Pin-OLED 2.3.3 OLEDs at High Excitation 2.4 Organic Lasers 2.4.1 Fundamentals of a Laser 2.4.2 Organic Molecules as Active Medium 2.4.3 Electrical Pumping of Organic Lasers 2.5 Dielectric Elastomer Actuators 2.5.1 Principle of Operation 2.5.2 Silicone-Based Materials 2.5.3 Compliant Electrodes 3 Experimental Methods 3.1 Sample Fabrication 3.1.1 Dielectric Elastomer Actuators 3.1.2 Organic Light Emitting Diodes 3.2 Characterization Techniques 3.2.1 Optical Characterization 3.2.2 Electrical Characterization 4 Tunable Optical Cavities with Dielectric Elastomer Actuators 4.1 Design of the Tunable Optical Microcavity 4.1.1 Tunable Cavity with Thin Metal Electrode . 4.1.2 Compliant Metal Electrodes on Dielectric Elastomer Films 4.1.3 Actuator Performance of Thick Metal Electrode 4.1.4 Electro-mechanical Characteristic 4.2 Tunable Emission of Optical Elastomer Cavities 4.2.1 Incorporation of Organic Laser Dyes in the Elastomer 4.2.2 Tunable Photoluminescence Spectra 4.2.3 Lasing in Elastomer Cavities 5 Novel Architecture for OLEDs at High Excitation 5.1 OLEDs at High Excitations Using Emission from Metal-free Area 5.1.1 Simulation of the Lateral Distribution of the Vertical Current Density 5.1.2 Investigation of the Lateral Emission 5.1.3 Organic Zener Junction 5.1.4 Simulation of High Excitation Behavior 5.2 Reduction of Self-heating for OLEDs at High Excitation 5.2.1 Crossbar-OLED at High Current Densities 5.2.2 Change in Layer Structure 5.3 Fully Transparent Metal-free OLEDs 5.3.1 Highly doped C 60 as a Transparent Electrode 5.3.2 Investigation of the External Quantum Efficiency 6 Conclusion and Outlook / Insbesondere durch die wachsende Nachfrage in Point-of-Care-Diagnostik, Sensorik oder optischer Kommunikationstechnologie wird eine große Anzahl von günstigen und kompakten Laserbauteilen benötigt. Aufgrund ihrer spezifischen Eigenschaften, wie hoher optische Verstärkung, niedriger Laserschwelle und spektrale Durchstimmbarkeit, sind organische Festkörperlaser geeignete Kandidaten, um diese Lücke zu schließen. Für die Anwendung als mikrooptische Systeme werden zwei wesentliche Komponenten benötigt: Die spektrale Durchstimmbarkeit sowie das Pumpen des Lasers sollten mit einem einfachen und kompakten Verfahren realisiert werden, im besten Fall durch Anlegen einer elektrischen Spannung. In der vorliegenden Arbeit wurde ein kompakter, elektrisch durchstimmbarer Laserresonator entwickelt, welcher mittels eines dielektrischen Elastomeraktuators in wenigen Prozessschritten realisiert werden kann. Der Resonator besteht aus zwei hochreflektierenden Spiegeln, einem dielektrischen Bragg-Spiegels und einem Metallspiegel, die eine Resonatorschicht aus einem weichen, verformbaren Elastomer umschließen. Für die elektrische Aktuation wird eine Spannung zwischen einer transparenten Bodenelektrode aus Indiumzinnoxid unterhalb des Bragg-Spiegel und der Metallschicht angelegt. Durch die elektrostatische Anziehung beider Elektroden wird die Elastomerschicht zusammengedrückt, wodurch die optischen Moden des Resonators eine Blauverschiebung der Wellenlänge erfahren. Durch die Integration einens Fluoreszenzfarbstoffes mit einem breiten Emissionsspektrum innerhalb der Resonatorschicht, wird die Umsetzung eines elektrisch durchstimmbaren, organischen Festkörperlasers ermöglicht. Im zweiten Teil der Arbeit wird ein neuartiges Design für organische Leuchtdioden (OLED) vorgestellt, um diese bei hohen Stromdichten zu betreiben und gleichzeitig die optischen Verluste, die beim Einbau in einen optischen Mikroresonator auftreten, zu minimieren. Hierfür wird eine zusätzliche hoch leitfähige, organische Schicht, die laterale Transportschicht, in den Schichtaufbau der OLED integriert. Aufgrund des verstärkten lateralen Ladungsträgertransports wird die Rekombinationszone bis außerhalb der Elektroden bedeckten Fläche ausgeweitet. Mithilfe einer Simulation, welche die organischen Schichten mittels eines Ersatzschaltbildes beschreibt, war es möglich, die laterale Verteilung der vertikalen Stromdichte zu bestimmen und damit Vorhersagen über die Stromdichtenverteilung bei hohen Anregungen (≈ 1 kA/cm² ) zu treffen. Darüber hinaus ermöglicht eine geänderte Schichtreihenfolge der OLED, die Joulesche Erwärmung des Bauteils zu reduzieren. Dadurch ist es möglich, hohe Stromdichten überhalb der vorherge sagten Laserschwelle von 1 kA/cm² zu erreichen. Diese Ergebnisse stellen eine wichtige Voraussetzung für die Entwicklung eines elektrisch gepumpten, organischen Festkörperlasers dar.:1 Introduction 2 Theoretical Background 2.1 Optical Cavities 2.1.1 Fabry-Perot Resonator 2.1.2 Transfer Matrix Algorithm 2.1.3 Distributed Bragg Reflector 2.1.4 Optical Microcavities 2.1.5 Tunable Optical Cavities 2.2 Organic Semiconductors 2.2.1 Properties 2.2.2 Electronic Structure 2.2.3 Absorption and Emission Spectra 2.2.4 Electrical Current 2.2.5 Doping 2.3 Organic Light Emitting Diodes 2.3.1 Basic OLED 2.3.2 Pin-OLED 2.3.3 OLEDs at High Excitation 2.4 Organic Lasers 2.4.1 Fundamentals of a Laser 2.4.2 Organic Molecules as Active Medium 2.4.3 Electrical Pumping of Organic Lasers 2.5 Dielectric Elastomer Actuators 2.5.1 Principle of Operation 2.5.2 Silicone-Based Materials 2.5.3 Compliant Electrodes 3 Experimental Methods 3.1 Sample Fabrication 3.1.1 Dielectric Elastomer Actuators 3.1.2 Organic Light Emitting Diodes 3.2 Characterization Techniques 3.2.1 Optical Characterization 3.2.2 Electrical Characterization 4 Tunable Optical Cavities with Dielectric Elastomer Actuators 4.1 Design of the Tunable Optical Microcavity 4.1.1 Tunable Cavity with Thin Metal Electrode . 4.1.2 Compliant Metal Electrodes on Dielectric Elastomer Films 4.1.3 Actuator Performance of Thick Metal Electrode 4.1.4 Electro-mechanical Characteristic 4.2 Tunable Emission of Optical Elastomer Cavities 4.2.1 Incorporation of Organic Laser Dyes in the Elastomer 4.2.2 Tunable Photoluminescence Spectra 4.2.3 Lasing in Elastomer Cavities 5 Novel Architecture for OLEDs at High Excitation 5.1 OLEDs at High Excitations Using Emission from Metal-free Area 5.1.1 Simulation of the Lateral Distribution of the Vertical Current Density 5.1.2 Investigation of the Lateral Emission 5.1.3 Organic Zener Junction 5.1.4 Simulation of High Excitation Behavior 5.2 Reduction of Self-heating for OLEDs at High Excitation 5.2.1 Crossbar-OLED at High Current Densities 5.2.2 Change in Layer Structure 5.3 Fully Transparent Metal-free OLEDs 5.3.1 Highly doped C 60 as a Transparent Electrode 5.3.2 Investigation of the External Quantum Efficiency 6 Conclusion and Outlook

Entirely soft robots with animal-like behavior and integrated artificial nervous systems will open up totally new perspectives and applications. To produce them we must integrate control and actuation in the same soft structure. Soft actuators (e.g. pneumatic, and hydraulic) exist but electronics are hard and stiff and remotely located. We present novel soft, electronicsfree dielectric elastomer oscillators, able to drive bioinspired robots. As a demonstrator we present a robot that mimics the crawling motion of the caterpillar, with integrated artificial nervous system, soft actuators and without any conventional stiff electronic parts. Supplied with an external DC voltage, the robot autonomously generates all signals necessary to drive its dielectric elastomer actuators, and translates an in-plane electromechanical oscillation into a crawling locomotion movement. Thereby, all functional and supporting parts are made of polymer materials and carbon. Besides the basic design of this first electronic-free, biomimetic robot we present prospects to control the general behavior of such robots. The absence of conventional stiff electronics and the exclusive use of polymeric materials will provide a large step towards real animal-like robots, compliant human machine interfaces and a new class of distributed, neuron-like internal control for robotic systems.

Dielectric elastomer actuators (DEAs) have been used for artificial muscles for years. Recently the DEA-based deformable surfaces have demonstrated controllable microscale roughness, ease of operation, fast response, and possibilities for programmable control. DEA muscles used in bioinspired robotic arms for large deformation and strong force also become desirable for their efficiency, low manufacturing cost, high force-to-weight ratio, and noiseless operation. The DEA-based responsive surfaces in microscale roughness control, however, exhibit limited durability due to irreversible dielectric breakdown. Lowering device voltage to avoid this issue is hindered by an inadequate understanding of the electrically-induced wrinkling deformation as a function of the deformable dielectric film thickness. Also, the programmable control and geometric analysis of the structured surface deformation have not yet been fully explored. Current methods to generate anisotropic wrinkles rely on mechanical pre-loading such as stretching or bending, which complicates the fabrication and operation of the devices. With a fixed mechanical pre-loading, the device can only switch between the flat state and the preset wrinkling state. In this thesis, we overcome these shortcomings by demonstrating a simple method for fabricating fault-tolerant electro-responsive surfaces and for controlling surface wrinkling patterns. The DEA-based system can produce different reversible surface topographies (craters, irregular wrinkles, structured wrinkles) upon the geometrical design of electrode and application of voltage. It remains functional due to its ability to self-insulate breakdown faults even after multiple high voltage breakdowns, and the induced breakdown punctures can be used for amplification of local electric fields for wrinkle formation at lower applied voltages. We enhance fundamental understanding of the system by using different analytical models combined with numerical simulation to discuss the mechanism and critical conditions for wrinkle formation, and compare it with the experimental results from surface topography, critical field to induce wrinkles in films of different thickness, and wrinkling patterns quantitatively analysed by different disorder metrics. Based on the results, we demonstrate its wide applicability in adjustable transparency films, dynamic light-grating filter, molding for static surface patterns, and multi-stable mirror-diffusor-diffraction grating device. For DEAs used for macroscopic-scale deformation in robotic arms, the main issue that undermines the performance of DEA muscles is the trade-off between strong force and large displacement, which limits the durability and range of potential robotic and automation applications of DEA-driven devices. In this thesis, this challenge is tackled by using DEAs in loudspeaker configuration for independent scaling-up of force and displacement, developing a theoretical prediction to optimise the operation of such DEAs in bioinspired antagonistic system to maximise speed and power of the robotic arm, and designing a clutch-gear-shaft mechanical system collaborating with the muscles to decouple the displacement and output force. Therefore, the trade-off between force and displacement in traditional DEA muscles can be resolved. The mechanical system can also convert the short linear spurt to an unlimited rotary motion. Combining these advantages, continuous movement with high output force can be accomplished.