High-field electrostriction of elastomeric polymer dielectrics for actuation

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 compress 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. Using this model, 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 strains exceeding 30% and energy densities up to 0.15 MJ/m(3). Based on the electrostatic model, the electromechanical coupling efficiency is over 50%. 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 EPAM retain their conductivity when stretched up to 80%, compared to 1-5% when fabricated as a uniform 2-dimensional electrode. Lastly, the paper presents the performance of various actuators that use EPAM materials. The technology appears to be well-suited for a variety of small-scale actuator applications.