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

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/cm2, 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.

Fabrication of Planar Microelectrode Array Using Laser-Patterned ITO and SU-8

“…Even though the proposed method employed SU-8 photolithography with a photomask in this study, an alternative method can be applied with polymer insulation and laser patterning of the polymer. Previously, we showed that a laser can pattern various thin-film polymers as well as metals such as polydimethylsiloxane (PDMS), liquid crystal polymer, and thin film of platinum and the platinum-iridium alloy [36,37]. Eventually, therefore, MEAs can be fabricated without any high-cost thin-film microfabrication processes such as photolithography, etching, and wet processes.…”

Cochlear Implant Users can Effectively Combine Place and Timing Cues for Pitch Perception

“…In brief, current spread was modeled using an inverse law and assuming the electrode array was linear and parallel to modeled nerve fibers. The interelectrode spacing varies among companies with Cochlear having a spacing of 0.4 to 0.9 mm (Fu 2002; Arnoldner et al 2007; Ertas et al 2022), Advanced Bionics having a spacing of 0.85 to 3.0 mm (Ertas et al 2022), and MED-EL having a spacing of 1.9 to 2.4 mm (Arnoldner et al 2007; Vermeire et al 2015; Shin et al 2021; Ertas et al 2022). Rationale for using simple models of electrode geometry and summation of electric fields was described in the study by Litvak et al (2007).…”

Recent Advances in Cochlear Implant Electrode Array Design Parameters

“…Recent research asserted that a higher speech perception score was achieved with more than eight channels [ 122 , 123 ]. Producing high density CI electrode arrays using conventional methods is limited due to channel interactions, reduction in the production yield, and increasing costs [ 121 ]. Therefore, innovations are needed for improving CI electrode array designs with a low cost and a high density of electrodes [ 121 ].…”

“…Their placement in the cochlea and their inability to totally cover the human hearing range are among the biggest issues. Due to limited number of electrodes and channels of conventional CIs (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), further research on integrating more channels should be carried out [121]. Channel interactions occur when adjacent electrodes are too close to each other; therefore, increasing the number of stimulations has been considered unnecessary, and it has been propounded that using more than eight channels is not effective on speech perception [121].…”

“…Due to limited number of electrodes and channels of conventional CIs (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), further research on integrating more channels should be carried out [121]. Channel interactions occur when adjacent electrodes are too close to each other; therefore, increasing the number of stimulations has been considered unnecessary, and it has been propounded that using more than eight channels is not effective on speech perception [121]. However, while 3-4 channels are adequate for simple sentence recognition, 30 or more channels are required for difficult speech conditions [69].…”