Polymer Cochlear Electrode Array: Atraumatic Deep Insertion, Tripolar Stimulation, and Long-Term Reliability

This thesis addresses another vital issue in the polymer-based neural implants: the long-term reliability issue. After suggesting a new method of forming mechanical interlocking to improve polymer-metal adhesion, the author performs accelerating aging tests to verify the method's efficacy. The aforementioned three topics have been thoroughly examined through various in vitro and in vivo studies. Verification foresees the development of LCP-based cochlear electrode array for an atraumatic deep insertion, advanced stimulation, and long-term clinical implant. Polymer-based devices have attracted attentions in the neural prosthetic field due to their flexibility and compatibility to micro-fabrication process. Liquid crystal polymer (LCP) is an inert, highly water-resistant polymer suitable for the encapsulation of electronic components and as a substrate material for fabricating neural interfaces. The author has designed, fabricated, and evaluated LCP-based cochlear electrode array for an improved polymer-based cochlear implant. The thesis deals with 3 key topics: atraumatic deep insertion, tripolar stimulation, and long-term reliability. Atraumatic insertion of the intracochlear electrode and resulting preservation of residual hearing have become essential in state-of-the-art cochlear implantation. A novel tapered design of LCP-based cochlear electrode array is presented to fulfill such goals. For high-density and pitch-recognizable cochlear implant, channel interaction should be avoided. Local tripolar stimulation using multi-layered electrode sites are shown to achieve highly focused electrical stimulation.