A prototype flexible microelectrode array for implant-prosthesis applications

This paper describes techniques for the fabrication of flexible microelectrodes for recording and stimulation within the human body. The intention of the effort was to develop a prototype microelectrode array for selective electrical stimulation of the cochlear nerve in cases of profound sensory deafness. The prototype array is formed on both sides of a thin-film plastic insulating substrate^? and consists of platinum conductor-elements, 0·3 μm thick and 12·7 μm wide, terminating at electrode surfaces, 250 μm wide. Metallisation of the substrate is accomplished by sputtering, and the electrode patterns are defined by photolithographic-etching techniques. Insulation of the array is achieved by dip coating in Silastic. Short term (nonstimulated) animal-tolerance studies indicate that the electrodes are biologically inert. Long-term implant studies are currently in progress, and experiments are planned to determine tissue-reaction and electrolytic-dissolution effects due to prolonged electrical stimulation. Microelectrodes using the fabrication techniques described can be applied, in practically any geometry desired, to the development of functional sensory and motor prostheses.