Electrostriction of polymer films for microactuators

The investigation of electrostrictive polymers (EPs) as a means of microactuation is described, EP materials are squeezed and stretched by electrostatic forces generated with compliant electrodes. This approach offers several advantages over existing actuator technologies, including high strains (> 30%), good actuation pressures (1.9 MPa), and high specific energy densities (0.1 J/g). In addition, the actuation is fast, uses lightweight materials, and has the potential for high energy efficiencies. Although EP actuators are electrostatics based, they offer 5 to 20 times the effective actuation pressure of conventional air-gap electrostatics at the same electric field strength. The gain is due to replacing air with a higher dielectric material, and to using two orthogonal modes of electromechanical coupling (stretching and squeezing) rather than one. Analysis of the mechanism of EP actuation is discussed. We also discuss fabrication techniques such as spin coating, casting, and dipping, as well as polymer and electrode materials. We describe demonstrations of prototype mini- and microactuators in a variety of configurations such as stretched films, stacks, rolls, tubes, and unimorphs. Last, we suggest potential applications of the technology in areas such as microrobots, sound generators, and displays.