(a) Equivalent circuit model of electrode–tissue interface, with interface reactance represented by a single capacitor CP. RP: charge transfer resistance, RS: Tissue/electrolyte resistance. (b) Equivalent circuit model of electrode–tissue interface, with interface reactance represented by a constant phase element (ZCPA). (c) Illustration of experimental setup. Ag/AgCl reference electrode, Platinum core of the concentric bipolar electrode, and Stainless steel outer shell of the bipolar electrode were connected to the potentiostat as the reference, working, and counter electrode, respectively. (d) Illustration of the geometry and dimension of the bipolar electrode tip.