Randles circuit model for characterizing a porous stimulating electrode of the retinal prosthesis

To develop a visual prosthesis, it is necessary to understand the changes in the electrochemical properties of stimulating electrodes implanted in the body. To evaluate these properties, we examined three types of equivalent circuit models that represented the electrode interface 23 weeks after the stimulation began. The results indicated that the Randles circuit model with Warburg impedance exhibited the difference in the electrochemical properties of the active and inactive electrodes, which might have been caused by the desorption of adsorbed protein from the electrode surface owing to the stimulation current. This model can be used to characterize the changes in the properties of porous stimulating electrodes.