Ultrahigh strain response of field-actuated elastomeric polymers

Extremely large strains were achieved with elastomeric polymer films that are subject to high electric fields. The films were coated on both sides with compliant electrode material. When voltage was applied, the film compressed in thickness and expanded in area. The strain response is dominated by the electrostatic forces produced by the charges on the compliant electrodes. Actuated strains up to 117% were demonstrated with silicone elastomers, and up to 215% with acrylic elastomers. A key to achieving these large strains is to introduce a high prestrain to the film. Specific energy densities were much greater than those of other field-actuated materials. Because the response is electrostatic in nature, the actuation mechanism is predicted to be fast. Response speeds in excess of 2000 Hz have been demonstrated in silicones. Acrylic response speeds are more than an order of magnitude slower, although the reason for this difference is not yet known. Measurement of material viscoelastic and electrical properties predicts that high efficiencies (> 80%) may be achieved with efficient driver circuits. A variety of actuators, including electrooptical devices, diaphragm pumps, and musclelike linear actuators, have been demonstrated with these materials, suggesting that this technology is well suited to small-scale electromechanical devices and robots.