Validation Of High Density Electrode Arrays For Cochlear Implants

Validation of High Density Electrode Arrays for Cochlear Implants

Creating high resolution, or high-density, electrode arrays may be the key for improving cochlear implant users' speech perception in noise, comprehension of lexical languages, and music appreciation. Contemporary electrode arrays use multipolar stimulation techniques such as current steering (shifting the spread of neural excitation in between two physical electrodes) and current focusing (narrowing of the neural spread of excitation) to increase resolution and more specifically target the neural population. Another approach to increasing resolution incorporates microelectromechanical systems (MEMS) fabrication to create a thin film microelectrode (TFM) array with a series of high density electrodes. Validating the benefits of high density electrode arrays requires a systems-level approach. This hypothesis will be tested computationally via cochlea and auditory nerve simulations, and in vitro studies will provide structural proof-of-concept.

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

This book describes the design, fabrication and evaluation of a polymer-based neural interface for a cochlear electrode array, reviewed in terms of fabrication process, functionality, and reliability. Polymer-based devices have attracted attention in the neural prosthetic field due to their flexibility and compatibility with micro-fabrication process. A 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 an 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 an LCP-based cochlear electrode array is presented to meet 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. 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.

Bridging the Gap in Neuroelectronic Interfaces