Strategies to improve electrode positioning and safety in cochlear implants

An injection-molded internal supporting rib has been produced to control th e flexibility of silicone rubber encapsulated electrodes designed to electr ically stimulate the auditory nerve in human subjects with se severe to pro found hearing loss, The rib molding dies, and molds for silicone rubber enc apsulation of the electrode, were designed and machined using AutoCad and M asterCam software packages in a PC environment. After molding, the prototyp e plastic ribs were iteratively modified based on observations of the perfo rmance of the rib/silicone composite insert in a clear plastic model of the human scala tympani cavity, The rib-based electrodes were reliably inserte d farther into these models, required less insertion force and were positio ned closer to the target auditory neural elements than currently available cochlear implant electrodes, With further design improvements the injection -molded rib may also function to accurately support metal stimulating conta cts and wire leads during assembly to significantly increase the manufactur ing efficiency of these devices. This method to reliably control the mechan ical properties of miniature implantable devices with multiple electrical l eads may be valuable in other areas of biomedical device design.