Electrochemical fabrication of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibrils on microfabricated neural prosthetic devices

This paper describes methods for electrochemically polymerizing conducting polymer poly(3,4-dioxyethylenethiophene) (PEDOT) nanofibrils on microfabricated neural prosthetic devices from aqueous solutions containing polyacrylic acid (PAA). These fibrils have characteristic sizes ranging from 100 to 1000 nm in diameter, depending on the concentration, molecular weight of PAA and thickness of the film. The PEDOT nanofibril-coated electrodes have significantly lower electrical impedance due to their higher effective surface area. We propose a mechanism of nanofibril formation involving locally anisotropic variations in EDOT monomer transport and PEDOT film growth due to segregation of the PAA counter-ions. This deposition method provides an improvement in the electrical properties by increasing the effective surface area of the electrodes, while still maintaining the overall small electrode size. It is also opens up new reliable and reproducible strategies for the direct electrochemical polymerization of conducting polymer nanofibrils on a variety of electrodes.