Correlation of impedance and effective electrode area of chondroitin sulphate doped PEDOT modified electrodes

Neural electrode arrays were coated with PEDOT doped with chondroitin sulphate. The impedance of the individually addressable microelectrodes were measured and fit with a 2 time constant equivalent circuit. The typically reported impedance at 1 kHz was significantly reduced with very thin coatings, but showed no correlation with effective electrode area. The impedance and phase angle at low frequencies was correlated with the effective electrode area. The charge density of the electrode was also correlated with the linear diffusion electroactive area.