High-Speed, Compact, Adaptive Lenses Using In-Line Transparent Dielectric Elastomer Actuator Membranes

Electrically tunable adaptive lenses provide several advantages over traditional lens assemblies in terms of compactness, speed, efficiency, and flexibility. We present an elastomer-liquid lens system which makes use of an in-line, transparent electroactive polymer actuator. The lens has two liquid-filled cavities enclosed within two frames, with two passive outer elastomer membranes and an internal transparent electroactive membrane. Advantages of the lens design over existing systems include large apertures, flexibility in choosing the starting lens curvature, and electrode encapsulation with a dielectric liquid. A lens power change up to 40 diopters, corresponding to focal length variation up to 300%, was recorded during actuation, with a response time on the order of tens of milliseconds.Engineering and Applied Science

Tunable Lenses Using Transparent Dielectric Elastomer Actuators

Focus tunable, adaptive lenses provide several advantages over traditional lens assemblies in terms of compactness, cost, efficiency, and flexibility. To further improve the simplicity and compact nature of adaptive lenses, we present an elastomer-liquid lens system which makes use of an inline, transparent electroactive polymer actuator. The lens requires only a minimal number of components: a frame, a passive membrane, a dielectric elastomer actuator membrane, and a clear liquid. The focal length variation was recorded to be greater than 100% with this system, responding in less than one second. Through the analysis of membrane deformation within geometrical constraints, it is shown that by selecting appropriate lens dimensions, even larger focusing dynamic ranges can be achieved.Engineering and Applied Science

Electrohydrodynamic printing of a dielectric elastomer actuator and its application in tunable lenses

Optical lenses driven by dielectric elastomer (DE) actuators with tunable focal lengths are presented here. They are inspired by the architecture of the crystalline lens and the ciliary muscle of the human eye and have prompted a growing interest. The most commonly used DEs in tunable lenses have often required highly transparent films and also the need to encapsulate clear liquid silicone to act as the lens. There is a restriction on the properties of the tunable lens imposed by materials limitations. Here, the fabrication of a fully 3D printed tunable lens with an inhomogeneous structure is described. It exhibited a 29% change in focal length from 33.6 mm to 26.1 mm under a dynamic driving voltage signal control. Furthermore, it displayed excellent stability when the focal length was tuned from far to near (30.1 mm to 25.3 mm) for 200 cycles. The tunable lens obtained mimics the working principle of the human eye in auto adjusting the focal length and has evident potential applications in imaging, information storage, beam steering and bifocal technology

Electrohydrodynamic Printing of a Dielectric Elastomer Actuator and Its Application in Tunable Lenses

Optical lenses driven by dielectric elastomer (DE) actuators with tunable focal lengths are presented here. They are inspired by the architecture of the crystalline lens and the ciliary muscle of the human eye and have prompted a growing interest. The most commonly used DEs in tunable lenses have often required highly transparent films and also the need to encapsulate clear liquid silicone to act as the lens. There is a restriction on the properties of the tunable lens imposed by materials limitations. Here, the fabrication of a fully 3D printed tunable lens with an inhomogeneous structure is described. It exhibited a 29% change in focal length from 33.6 mm to 26.1 mm under a dynamic driving voltage signal control. Furthermore, it displayed excellent stability when the focal length was tuned from far to near (30.1 mm to 25.3 mm) for 200 cycles. The tunable lens obtained mimics the working principle of the human eye in auto adjusting the focal length and has evident potential applications in imaging, information storage, beam steering and bifocal technology

Perspective and Potential of Smart Optical Materials

The increasing requirements of hyperspectral imaging optics, electro/photo-chromic materials, negative refractive index metamaterial optics, and miniaturized optical components from microscale to quantum-scale optics have all contributed to new features and advancements in optics technology. Development of multifunctional capable optics has pushed the boundaries of optics into new fields that require new disciplines and materials to maximize the potential benefits. The purpose of this study is to understand and show the fundamental materials and fabrication technology for field-controlled spectrally active optics (referred to as smart optics) that are essential for future industrial, scientific, military, and space applications, such as membrane optics, light detection and ranging (LIDAR) filters, windows for sensors and probes, telescopes, spectroscopes, cameras, light valves, light switches, and flat-panel displays. The proposed smart optics are based on the Stark and Zeeman effects in materials tailored with quantum dot arrays and thin films made from readily polarizable materials via ferroelectricity or ferromagnetism. Bound excitonic states of organic crystals are also capable of optical adaptability, tunability, and reconfigurability. To show the benefits of smart optics, this paper reviews spectral characteristics of smart optical materials and device technology. Experiments testing the quantum-confined Stark effect, arising from rare earth element doping effects in semiconductors, and applied electric field effects on spectral and refractive index are discussed. Other bulk and dopant materials were also discovered to have the same aspect of shifts in spectrum and refractive index. Other efforts focus on materials for creating field-controlled spectrally smart active optics (FCSAO) on a selected spectral range. Surface plasmon polariton transmission of light through apertures is also discussed, along with potential applications. New breakthroughs in micro scale multiple zone plate optics as a micro convex lens are reviewed, along with the newly discovered pseudo-focal point not predicted with conventional optics modeling. Micron-sized solid state beam scanner chips for laser waveguides are reviewed as well

Soft dielectric elastomer oscillators driving bioinspired robots

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

A Review of Cooperative Actuator and Sensor Systems Based on Dielectric Elastomer Transducers

This paper presents an overview of cooperative actuator and sensor systems based on dielectric elastomer (DE) transducers. A DE consists of a flexible capacitor made of a thin layer of soft dielectric material (e.g., acrylic, silicone) surrounded with a compliant electrode, which is able to work as an actuator or as a sensor. Features such as large deformation, high compliance, flexibility, energy efficiency, lightweight, self-sensing, and low cost make DE technology particularly attractive for the realization of mechatronic systems that are capable of performance not achievable with alternative technologies. If several DEs are arranged in an array-like configuration, new concepts of cooperative actuator/sensor systems can be enabled, in which novel applications and features are made possible by the synergistic operations among nearby elements. The goal of this paper is to review recent advances in the area of cooperative DE systems technology. After summarizing the basic operating principle of DE transducers, several applications of cooperative DE actuators and sensors from the recent literature are discussed, ranging from haptic interfaces and bio-inspired robots to micro-scale devices and tactile sensors. Finally, challenges and perspectives for the future development of cooperative DE systems are discussed

Wave Propagation in Viscoelastic Dielectric Elastomer Media

Dielectric elastomers (DEs) are capable of producing large deformation under electric stimuli, which makes them desirable materials for a variety of applications including biomimetics, dynamics, robotics, energy harvesting, and waveguide devices. In general, DEs possess intrinsic hyperelasticity and viscosity. Such material properties may significantly affect the dynamic performance of DE-based devices. The delicate interplay among electromechanical coupling, large deformation, material viscosity and dynamics makes modeling of the performance of DE-based devices more challenging. Therefore, in order to provide guidelines for the optimal design of DE waveguide devices, it is essential to develop appropriate and reliable models, and efficient numerical methods to examine their performance first. In this thesis, by integrating the state-of-art finite-deformation viscoelasticity theory into the framework of small-amplitude wave propagation superposed on a finitely deformed medium, the Rayleigh-Lamb wave propagation in a viscoelastic DE medium is investigated. Simulation results have demonstrated the effects of material viscosity, status of relaxation, external electric load, and mechanical pre-stretch on the dispersion behavior of the wave. For both pure elastic and viscoelastic DE media, waves with certain frequencies could be filtered by actively tuning electric loads. Moreover, some interesting findings conclude that the material viscoelasticity may cause some significant changes in the wave dispersion behavior. Therefore, incorporating the material viscosity in modeling DE waveguide is expected to provide more accurate prediction on their performance. This thesis will help to better understand the fundamentals of wave propagation in DE media and trigger more innovative and optimal design for DE waveguide applications

Intelligente Antriebssysteme für dynamische Anwendungen auf Basis dielektrischer Elastomere

Dielektrische Elastomere (DE) ermöglichen die Entwicklung leichter, geräuschloser und ressourcenschonender Systeme, die als Aktoren eine sehr hohe Flexibilität aufweisen. Dies betrifft sowohl Design- als auch Ansteuerungsmöglichkeiten. Als intelligente Materialien können DE zusätzlich als Sensoren genutzt werden. Ihr großer Arbeitsbereich in Bezug auf Dehnung und Frequenz ist die Grundlage für ein weites Spektrum an Anwendungsmöglichkeiten. Ziel dieser Arbeit ist es, innovative Systemkonzepte zu entwickeln, welche die Ansteuerungsmöglichkeiten in höheren Frequenzbereichen ausnutzen, sowie die dafür nötigen dynamischen Grundlagen zu erforschen. Am Beispiel einer smarten Vibrationsmassage wird DE-Aktorik zur Erzeugung der Vibration genutzt, während die sensorischen Eigenschaften für die Überwachung des Systemzustands zuständig sind. Die Massage kann somit optimal an Benutzer:innen angepasst werden. Erweiterte Auslegungskonzepte ermöglichen die systematische Betrachtung einer veränderlichen Gewichtslast sowie eines einstellbaren Systemdrucks. Um darauf aufbauend auch intelligente Systeme für noch höhere Frequenzbereiche zu entwickeln, stellt der zweite Teil das per Laservibrometrie untersuchte dynamische Membranverhalten der DE beim Übergang bis in den akustischen Bereich vor. Das resultierende Frequenzverhalten, die entstehenden Moden sowie insbesondere der Einfluss durch verschiedene Parameter bilden die Basis für die Entwicklung komplexer hochfrequenter Aktor-Sensor-Systeme.Dielectric elastomers (DE) enable the development of lightweight, silent and resource-saving systems. In actuator systems, they offer a high degree of flexibility in terms of design and control options. Being classified as a smart material, DE can additionally be used as sensors. Their large operating range regarding material strain and frequency creates the basis for a wide range of possible applications. The goal of this work is the development of innovative system concepts that exploit the actuation capabilities in higher frequency ranges and to explore the necessary dynamic fundamentals. At the example of a smart vibration massage system, the DE actuator technology is used to generate the vibration, while the sensing capabilities are responsible for monitoring the system state. This allows an optimal massage adaption to individual users. The developed advanced system concepts include systematic consideration of variable weight loads as well as adjustable system pressure. For the development of intelligent systems in even higher frequency ranges, the second part presents the dynamic DE membrane behavior in transition to the acoustic frequency range, which is investigated by laser vibrometry. The resulting frequency behavior, the forming modes and specifically the influence of various parameters create the basis for the development of complex high-frequency actuator-sensor systems