Study Of Electrochemical Characteristics And Implant Able Feasibility Of Au Flexible Retinal Microelectrode Array Based On Parylene-C

Visual prosthesis has been proposed as a promising method to restore visual function of AMD and RD patients. Microelectrode arrays play an important role in epiretinal prosthetic implants by transmitting electrical pulses from current stimulators to evoke inner retinal cells. Electrical signals are then transmitted to the visual cortex through the optic nerve, forming artificial visual images in the brain. Safety and long-term reliability are essential requirements for microelectrode arrays used as implantable devices.Considering the structure characteristics and implanting requirements of retina microelectrode array, the key component of retinal prosthesis, implantable epi-retinal Au microelectrode array based on Parylene-C with a diameter of 200μm was designed and fabricated. Implanting experiments were performed on the eyes of rats. In vitro and in vivo measurements were performed. The retina microelectrode surface morphology observed under scanning electron microscopy (SEM) presented good roughness, suggesting a low electrochemical impedance and high ability of charge injection. To measure electrochemical characteristics of the microelecrode array, the in vitro electrochemical characteristics of this microelectrode array are investigated by electrochemical impedance spectroscopy, cyclic voltammetry and potential transient measurements using a three-electrode electrochemical cell containing phosphate-buffered saline (PBS). The electrochemical impedance, charge storage capacity (CSC) and charge injection capacity (CIC) of the microarray were calculated respectively.The average impedance of the Au electrodes at 1 KHz was 36.54±0.88 KΩ. The average phase angle at 1 KHz was -73.52±1.3°. The average CSC of the Au electrodes was 103.33±15 μC/cm2. The CIC of the microelectrode was 22.3 μC/cm2. The array implanted on the retina of rat shows good flexibility. Results showed that morphological and electrochemical properties of the flexible gold electrode met the requirements of retinal stimulating electrodes. The low cost and simplified manufacturing design of retinal microelectrode was proposed which shows potential for use in neurostimulation applications and can in vivo electrophysiological experiments on animals.