Piezoelectric actuators employing PVDF coated with flexible PEDOT-PSS polymer electrodes

Piezoelectric polymer sheets usually have metallic electrodes that considerably stiffen the sheet and correspondingly decrease its piezoelectric response in actuator and sensor applications. We have developed both airbrush and inkjet printing methods for applying electrodes of the conducting polymer poly(ethylene dioxythiophene) (PEDOT-PSS) to sheets of poly(vinylidene fluoride) (PVDF). PEDOT-PSS electrodes of reasonable thickness have considerably higher resistance than metal electrodes. We calculated the voltage and current response as a function of position on the electrodes of a single "electroded" PVDF sheet. We did 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. By finding the response as a function of frequency, we can determine the necessary electrode thickness for various applications. Next we calculated the extension-mode piezoelectric response of a rectangular sheet to an ac voltage applied at one end. We made and tested 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. Finally, we compare results for these high-displacement, low-force actuators with those for low-displacement, high-force actuators of direct extension designs, and propose a cylindrical actuator design with intermediate displacement and force