High k Dielectric Elastomeric Materials for Low Voltage Applications C. Walder a , M. Molberg a,b , D. M. Opris a , F. A. Nüesch a , C. Löwe a *, C. J.G. Plummer b , Y. Leterrier b , J.-A. E. Månson b a Laboratoy for Functional Polymers, Swiss Federal Laboratories for Material Testing and Research (Empa), CH-8600 Dübendorf, ZH, Switzerland. b Laboratoire de Technologie des Composites et Polymères (LTC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, VD, Switzerland ABSTRACT In principle EAP technology could potentially replace common motion-generating mechanisms in positioning, valve control, pump and sensor applications, where designers are seeking quieter, power efficient devices to replace conventional electrical motors and drive trains. Their use as artificial muscles is of special interest due to their similar properties in terms of stress and strain, energy and power densities or efficiency. A broad application of dielectric elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices. The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the problem. We prepared composites from cross-linked silicone elastomers or thermoplastic elastomers (TPE) by blending them with organic fillers exhibiting a high dielectric constant. Well characterized monomeric phthalocyanines and modified doped polyaniline (PANI) were used as filler materials. In addition, blends of TPE and an inorganic filler material PZT were characterized as well. We studied the influence of the filler materials onto the mechanical and electromechanical properties of the resulting mixtures. A hundredfold increase of the dielectric constant was already observed for blends of an olefin based thermoplastic elastomer and PANI. Keywords: dielectric elastomer, electroactive polymer, mechanical properties, polymer blend 1. INTRODUCTION Dielectric elastomer actuators are electric field driven polymer transducers [1, 2], which have exceptional properties such as large strains (up to 380 %), fast response (>1 KHz), lightweight, noise free actuation and inexpensive processing. The soft materials can be used to design novel sensors, actuators and generators for applications ranging from robotics, prosthetics to optics. A variety of demonstrators based on DEA have been realized [3], however only a few products are currently on the market [4, 5]. DEA are based on the electromechanical response of an elastomer film (typically silicone or acrylic polymers) with compliant electrodes on each surface. When a voltage is applied an electrostatic pressure is built up, the almost incompressible film shrinks in thickness and expands in area; electrical energy is directly converted into mechanical energy. The simple working principle of actuators based on dielectric elastomer technology is shown in figure 1. Using a simple electrostatic model (opposite charges on the electrodes attract each other, while the like charges on the electrodes repel each other so called Maxwell stress), we can derive the effective pressure produced by the electrodes on the film as a function of the applied voltage. This pressure, p, is p = ε r ε 0 E 2 = ε r ε 0 (V/t) 2 equation 1 ε r and ε 0 are the permittivity of free space and the relative permittivity (dielectric constant) of the polymer, respectively. E is the applied electric field; V is the applied voltage; and t is the film thickness. *christiane.loewe@empa.ch ; phone 41 44 823 44 99; fax 41 44 8; empa.ch Electroactive Polymer Actuators and Devices (EAPAD) 2009, edited by Yoseph Bar-Cohen, Thomas Wallmersperger, Proc. of SPIE Vol. 7287, 72870Q · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.815926 Proc. of SPIE Vol. 7287 72870Q-1 Downloaded from SPIE Digital Library on 20 Nov 2009 to 129.132.191.129. Terms of Use: http://spiedl.org/terms EMPA20090569