Actuators based on PVDF sheets with flexible PEDOT polymer electrodes

Piezoelectric polymer sheets traditionally have metallic electrodes that increase considerably the stiffness of the sheet and correspondingly decrease its piezoelectric response, whether as an actuator or a sensor. We have developed methods for applying electrodes of the conducting polymer poly(ethylene dioxythiophene) (PEDOT) to sheets of poly(vinylidene fluoride) (PVDF). Our most recent method involves printing the PEDOT onto the PVDF. PEDOT electrodes of reasonable thickness have considerably higher resistance than metal electrodes, so we have calculated the response of the voltage and current as a function of position on the electrodes of a single electroded PVDF sheet. We have done this both for a rectangular sheet with an ac voltage applied at one end, and for a semicircular sheet with ac voltage applied to a small semicircular metal tab at the center of the circle. In this way we find the response as a function of frequency, and determine the necessary electrode thickness for various applications. We have made bimorphs of two such electroded sheets that are glued together to give a bending response. We have also constructed actuators made of two bimorphs attached together at both ends. Better response is achieved than for similar actuators constructed from sheets with metal electrodes.