The Research Of The Neuro-Stimulating Microelectrodes For Visual Prosthesis

Visual information composes 90% of the overall information people obtained. Blindness can be induced by eye illness or mechanically injury and affects millions of people worldwide. Currently, vision loss cannot be effectively treated. Recent advances in bioengineering and micro-technology have led to the development of highly sophisticated micro-electronic devices that are designed to stimulate viable neuronal tissue using microelectrodes in the hope of helping the blind to restore some functional vision. The microelectrodes, by which the charges are injected into the visual cortex, retina or optic nerve, serves as the interface between the electronics and the biological tissue and are the key component of the visual prosthesis. Therefore, to study the property of the neuro-stimulating microelectrodes is of significant importance in the vision rehabilitation research.In this paper, the microelectrodes used in different international visual prosthesis groups were introduced, and several kinds of implantable neuro-stimulating electrode array were fabricated, such as metal microwire array based on Print Circuit Board (PCB), cylinder penetrating electrode with different probe length, FMA electrode array and polyimide-based flexible thin film electrode. In order to enable the electrode with good biocompatibility, we employed tungsten and Pt/Ir alloy as the electrode material, C-Parelyene and Teflon as the insulation layer and polyimide as the substrate material of the flexible thin film electrode. The tip of microwire electrode was exposed and modified using electrochemical etching method; various moulds were designed to help fabricate electrodes and optimize the configuration for the fixation in the chronical animal experiment.The basic theory of electrode-electrolyte electrochemical process and the equivalent electrical circuit were studied in this paper, and thereafter proposed the precise three-electrode system to test the electrode-electrolyte interface impedance. Moreover, the cell-culture method was used to evaluate the biocompatibility of the insulated flexible thin film electrode, and the influence of the electrical stimulation on the optic nerve neurogliocytes was observed.