Induced polarization imparts piezoelectricity in non-crystalline polymer films

Abstract Piezoelectric materials produce linear deformation in response to an applied electric field and are essential for precision control devices. The conventional view is that polymers must be crystalline and possess a remanent polarization after an artificial poling in order to gain piezoelectricity. For ferroelectric polymer poly(vinylidene difluoride), the required poling field is exceptionally high, up to 150–200 volts per micron. Here, we circumvent this limitation by utilizing the elastic displacement of the electric dipoles and creating a net polarization. In this case, the dielectric acts as a piezoelectric as long as a bias electric field is applied, with its piezoelectric coefficient increasing proportionally to the strength of the electric field until polarization saturation sets in. Experiments indicate that a sub-coercive field of 68 volts per micron can induce a high piezoelectric coefficient d 33 of − 36 picometers per volt in an unpoled poly(vinylidene fluoride-trifluoroethylene) film. The proposed methodology is further extended to amorphous polymers, providing an opportunity to discover new piezoelectrics within the dielectric family.