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

- Poly-3,4-ethylenedioxythiophene was successfully doped with chondroitin sulfate (PEDOT-CS) by electropolymerisation on neural electrode arrays.
- Electrochemical impedance spectroscopy of PEDOT-CS could be fit with a Randles equivalent circuit.
- Impedance at 1 kHz was reduced by electrode coating but not correlated with effective electrode area.
- Impedance and phase angle at low frequencies was correlated with effective electrode area.
- The charge density of the PEDOT-CS modified electrodes was dependant on the electrode area.

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.