Application of poly (3,4-ethylenedioxythiophene)-poly(styrene sulfonate) to poly(vinylidene fluoride) as a replacement for traditional electrodes

Abstract

Piezoelectric devices can be made more efficient by replacing the metal electrodes with polymer electrodes. Different conducting polymers were investigated to replace the metal electrodes currently used to actuate PVDF. After two years of working with the conducting polymer poly(3,4-ethylenedioxythiophene)-poly (styrene sulfonate), PEDOT-PSS, it was successfully deposited on the piezoelectric polymer poly(vinylidene fluoride), PVDF, in 5-10 micron thick layers. The biggest challenge presented was polymer on polymer adhesion. The fluorine in PVDF gives it the same "non-stick" properties as "Teflon®. Similar to applying metal electrodes, PVDF must be surface treated before the polymer will adhere. Unlike metal electrodes, a special primer must be applied before a layer of PEDOT-PSS can be applied. The primer used in this study is a modified recipe originating from a formulation developed by the Bayer/Starck Corp. This primer adheres the PEDOT-PSS to the PVDF using a polyurethane polymer mixed with PEDOT-PSS and a solvent. The primer and the PEDOT-PSS mixture are applied using an artist's airbrush to lightly spray each thin layer. Each layer is then dried using cool, forced air. This procedure is repeated until a layer approximately 10 microns thick has been achieved. Once the last layer is dry, the conductivity can be measured. Using two brass blocks to measure the resistance, the conductivity of the PEDOT-PSS layer is obtained. It has been found that the sprayed layer of PEDOT-PSS has a conductivity of ~ 0.05 S/cm; this is 2.5% of the published conductivity of ~2 S/cm. This level of conductivity is high enough to operate PVDF within the frequency range of 20 Hz to 300 Hz.