Electrochemical deposition and characterization of conducting polymer polypyrrole/PSS on multichannel neural probes

Abstract The conducting polymer polypyrrole (PPy) doped with polystyrene sulfonate (PSS) was electrochemically deposited onto the electrode sites of micromachined neural probes. The surface morphology of the films was found to vary with coating thickness. Examinations of atomic force microscope (AFM) images of the coatings using the power spectral density (PSD) method revealed the spatial frequency dependence of surface roughness. The magnitude of the impedance of the PPy/PSS coated electrode at the biologically relevant frequency of 1 kHz decreased with increasing thickness as the film roughens. The lowest impedance was observed at a thickness of ∼13 μm. This decrease in impedance was correlated to the increase in effective surface area. The power-law behavior of the impedance spectra was quantitatively correlated with the fractal characteristics of the polymer-coated electrode surface morphology. High quality neural signals were recorded acutely from cerebellum of guinea pig through the PPy/PSS coated electrodes.