High-field deformation of elastomeric dielectrics for actuators

This paper investigates the use of elastomeric dielectric materials with compliant electrodes as a means of actuation. When a voltage is applied to the electrodes, the elastomeric films expand in area and compresses in thickness. The strain response to applied electric fields was measured for a variety of elastomers. A nonlinear, high-strain, Mooney-Rivlin model was used to determine the expected strain response for a given applied field pressure. Comparing this analytical result to with experimentally measured strains, we determined that the electrostatic forces between the free charges on the electrodes are responsible for the observed response. Silicone polymers have produced the best combination of high strain and energy density, with thickness strains up to 41% and elastic energy densities up to 0.2 MJ/m(3). Response times of 2 ms have been experimentally measured. This paper also reports recent progress in making highly compliant electrodes. We have shown, for example, that gold traces fabricated in a zig-zag pattern on silicone retain their conductivity when stretched up to 80%, compared to 1-5% when fabricated as a uniform two-dimensional electrodelayer. Optimal loading of dielectric elastomers can have a significant impact on performance: and the paper describes techniques which that can increase output up to a factor of 5 compared to neutral loading conditions. Lastly, the paper briefly discusses the performance of various actuators that use dielectric elastomer materials. The technology appears to be well-suited to a variety of small-scale actuator applications. (C) 2000 Published by Elsevier Science B.V.