Thin-film multielectrode arrays for a cochlear prosthesis

The design and fabrication of flexible thin-film microelectrode arrays for use in a cochlear prosthesis are described. The electrode array is designed to be inserted through the round window of the cochlea into the spiral scala tympani chamber of the cochlea. A lifetime of decades under stimulation is sought. The electrode array is comprised of photolithographically defined platinum-on-tantalum conductors sandwiched between polyimide layers. A liquid polyimide is used, which polymerizes in two stages. After the first stage of curing, the polyimide is susceptible to photolithographic etching, allowing patterned access holes to be cut into the top layer of the insulating sandwich. After the second cure, the polymer becomes inert biocompatible Kapton. The processing techniques and the electrode test results are presented.