Electrode Coatings for Neurostimulation and Cardiac Pacing Applications*

Neurostimulation and cardiac pacing electrodes have many applications each requiring biocompatibility and the ability to exchange charge between the underlying metallic electrode and the ionic fluid surrounding it. The trend toward smaller electrodes as well as higher current applications has resulted in the need for improved charge transfer. With this goal, cubic nitride coatings with columnar microstructure have been added to the electrodes using reactive magnetron sputtering in a nitrogen rich atmosphere. These coatings which provide capacitive coupling between the electrode and the biological solutions increase the surface area improving the required charge transfer. Coating performance is measured electrochemically using cyclic voltammetry with the coated metal as the working electrode, a platinum coiled wire as the counter electrode, and phosphate buffered saline as the electrolyte. We report on the thickness dependence of the coating performance and delineate important parameters influencing this performance.