Piezoelectric and electrostrictive polymeric actuator materials

Piezoelectric and electrostrictive polymers are widely used in many areas of electromechanical actuation and transduction. This paper summarizes the current status and recent works in this class of polymers. For the piezoelectric polymers, the electromechanical properties of poly(vinylidene fluoride-trifluoroethylene) copolymers (P(VDF-TrFE)), which possess the best piezoelectric performance among the known piezopolymers, are presented. In order to improve the strain capability and other electromechanical properties, the large electrostrictive response and high electromechanical conversion efficient near a first order ferroelectric-paraelectric transition of P(VDF-TrFE) copolymer were exploited. It is shown that the copolymer, treated with high energy electron irradiation, exhibits high electrostrictive strains (-5% longitudinal strain under 150 MV/m and 3.5% transverse strain under 110 MV/m) with high strain energy density, high load capability and improved electromechanical coupling factor. For the comparison, the works related to the Maxwell stress induced strain response in soft polymers are also discussed.