Design of Return/Ground Electrode for Neural Stimulator

Probe used for neural stimulation has two parts- the stimulating and return electrodes. Most of the researches are evolving around designing stimulating electrode(s) to stimulate the neurons almost neglecting return electrode. Although some of the research group are using part of the stimulating electrodes as return electrode(s), while others are using a common electrode placed far away from the stimulating electrode as a return electrode. Designing return electrode is as important as the stimulating one is. It has a profound affect on the overall performance of a stimulator. The impedance of a probe is influenced equally by both the electrodes. So careful design of a return electrode can reduce the overall impedance and the required power of a probe dramatically. Here we are presenting a few designs of return electrode and their analysis to find out the best one. We have tested some of the fabricated designs in 0.9% saline solution and found that donut design has less resistance but suffers from high capacitance at higher frequency.