Manufacturable 32-Channel Cochlear Electrode Array and Preliminary Assessment of Its Feasibility for Clinical Use.

Soowon Shin,Kyou-Sik Min,Seung-Ha Oh,Gwangjin Choi,Yoonhee Ha,Sangwoo Kim,Junewoo Hyun

doi:10.3390/mi12070778

Abstract

(1) Background: In this study, we introduce a manufacturable 32-channel cochlear electrode array. In contrast to conventional cochlear electrode arrays manufactured by manual processes that consist of electrode-wire welding, the placement of each electrode, and silicone molding over wired structures, the proposed cochlear electrode array is manufactured by semi-automated laser micro-structuring and a mass-produced layer-by-layer silicone deposition scheme similar to the semiconductor fabrication process. (2) Methods: The proposed 32-channel electrode array has 32 electrode contacts with a length of 24 mm and 0.75 mm spacing between contacts. The width of the electrode array is 0.45 mm at its apex and 0.8 mm at its base, and it has a three-layered arrangement consisting of a 32-channel electrode layer and two 16-lead wire layers. To assess its feasibility, we conducted an electrochemical evaluation, stiffness measurements, and insertion force measurements. (3) Results: The electrochemical impedance and charge storage capacity are 3.11 ± 0.89 kOhm at 1 kHz and 5.09 mC/cm, respectively. The V/H ratio, which indicates how large the vertical stiffness is compared to the horizontal stiffness, is 1.26. The insertion force is 17.4 mN at 8 mm from the round window, and the maximum extraction force is 61.4 mN. (4) Conclusions: The results of the preliminary feasibility assessment of the proposed 32-channel cochlear electrode array are presented. After further assessments are performed, a 32-channel cochlear implant system consisting of the proposed 32-channel electrode array, 32-channel neural stimulation and recording IC, titanium-based hermetic package, and sound processor with wireless power and signal transmission coil will be completed.

Highlights

A cochlear implant (CI) is a surgically implanted electronic medical device that restores sound perception for people with congenital or severe hearing loss by delivering modulated electrical stimulation to auditory nerves through an electrode array inserted in the cochlea
Since the fabricated 32-channel electrode array has a three-layered arrangement consisting of a 32-channel electrode layer and two 16-lead wire layers, where only the wire bundle is shown in the bottom view of the electrode
The implantable pulse generator (IPG) of the conventional CI consists of an intracochlear electrode array, lead wires, electronics, a hermetic package and a coil for wireless telemetry [23]

Summary

Introduction

A cochlear implant (CI) is a surgically implanted electronic medical device that restores sound perception for people with congenital or severe hearing loss by delivering modulated electrical stimulation to auditory nerves through an electrode array inserted in the cochlea. An intact cochlea has approximately 35,000–50,000 spiral ganglion cells, which sense the electrical potential induced by changes in the ionic concentration of synaptic connections with hair cells and generate the first auditory action potential. The deficiency or damage of cochlear hair cells causes sensory neural hearing loss (SNHL) because hair cells trigger the action potential in spiral ganglion cells. The location of the hair cells in the inner cochlea is related to the frequency that stimulates the corresponding spiral ganglion cells. Each electrode stimulates ganglion cells at different locations, allowing the auditory nerve to deliver the corresponding sound frequency

Methods

Results

Discussion

Conclusion