ELECTROSTRICTION OF POLYMER DIELECTRICS WITH COMPLIANT ELECTRODES AS A MEANS OF ACTUATION

The electrostriction of elastomeric polymer dielectrics with compliant electrodes is potentially useful as a small-scale, solid-state actuat or technology. Electrostrictive polymer (EP) materials are capable of efficient and fast response with high strains (> 30%), good actuation pressures (up to 1.9 MPa), and high specific energy densities (up to 0 .1 J g(-1)). In this article, the mechanism of electrostriction is sho wn to be due to the electrostatic attraction of free charges on the el ectrodes. Although EP actuators are electrostatics based, they are sho wn to produce 5-20 times the effective actuation pressure of conventio nal air-gap electrostatics at the same electric field strength. The th in uniform dielectric films necessary for fabrication of EP actuators have been fabricated by techniques such as spin coating, casting, and dipping. A variety of materials and techniques have been used to produ ce the compliant electrodes, including lift-off stenciling techniques for powdered graphite, selective wetting of ionically conductive polym ers, and spray coating of carbon blacks and fibrils in polymeric binde rs. Prototype actuators have been demonstrated in a variety of configu rations such as stretched films, stacks, rolls, tubes, and unimorphs. Potential applications of the technology in areas such as microrobots, sound generators, and displays are discussed in this article. (C) 199 8 Published by Elsevier Science S.A.