OBJECTIVE: To improve the existing manually assembled cochlear implant electrode arrays, a thin-film electrode array (TFEA) was microfabricated having a maximum electrode density of 15 sites along an 8-mm length, with each site having a 75 μm × 1.8 μm (diameter × height) disk electrode. METHODS: The microfabrication method adopted photoresist transferring, lift-off, two-step oxygen plasma etching, and fuming nitric acid release to reduce lift-off complexity, protect the metal layer, and increase the release efficiency. RESULTS: Systematic in vitro characterization showed that the TFEA's bending stiffness was 6.40 × 10-10 N·m2 near the base and 1.26 × 10-10 N·m2 near the apex. The TFEA electrode produced an average impedance of 16 kΩ and a maximum current limit of 800 μA, measured with 1-kHz sinusoidal current using monopolar stimulation in saline. A TFEA prototype was implanted in a cat cochlea to obtain in vivo measurements of electrically evoked auditory brainstem and inferior colliculus responses to monopolar stimulation with 41-μs/phase biphasic pulses. Both physiological responses produced a threshold of ∼300 μA and a dynamic range of 5-8 dB above the threshold. Compared with existing arrays, the present TFEA had 104 times less bending stiffness, 97% less electrode area, and comparable physiological thresholds. CONCLUSION: Using a simplified structure and stable fabrication method, the present TEFA produced physical and physiological performance comparable to existing commercial devices. SIGNIFICANCE: The present TFEA represents a step closer toward an automated process replacing the labor-intensive and expensive manual assembly of the cochlear implant electrode arrays.
OBJECTIVE: To improve the existing manually assembled cochlear implant electrode arrays, a thin-film electrode array (TFEA) was microfabricated having a maximum electrode density of 15 sites along an 8-mm length, with each site having a 75 μm × 1.8 μm (diameter × height) disk electrode. METHODS: The microfabrication method adopted photoresist transferring, lift-off, two-step oxygen plasma etching, and fuming nitric acid release to reduce lift-off complexity, protect the metal layer, and increase the release efficiency. RESULTS: Systematic in vitro characterization showed that the TFEA's bending stiffness was 6.40 × 10-10 N·m2 near the base and 1.26 × 10-10 N·m2 near the apex. The TFEA electrode produced an average impedance of 16 kΩ and a maximum current limit of 800 μA, measured with 1-kHz sinusoidal current using monopolar stimulation in saline. A TFEA prototype was implanted in a cat cochlea to obtain in vivo measurements of electrically evoked auditory brainstem and inferior colliculus responses to monopolar stimulation with 41-μs/phase biphasic pulses. Both physiological responses produced a threshold of ∼300 μA and a dynamic range of 5-8 dB above the threshold. Compared with existing arrays, the present TFEA had 104 times less bending stiffness, 97% less electrode area, and comparable physiological thresholds. CONCLUSION: Using a simplified structure and stable fabrication method, the present TEFA produced physical and physiological performance comparable to existing commercial devices. SIGNIFICANCE: The present TFEA represents a step closer toward an automated process replacing the labor-intensive and expensive manual assembly of the cochlear implant electrode arrays.
Authors: Jonathan T W Kuo; Brian J Kim; Seth A Hara; Curtis D Lee; Christian A Gutierrez; Tuan Q Hoang; Ellis Meng Journal: Lab Chip Date: 2013-02-21 Impact factor: 6.799
Authors: P Bhatti; J Van Beek-King; A Sharpe; J Crawford; S Tridandapani; B McKinnon; D Blake Journal: Biomed Res Int Date: 2015-07-05 Impact factor: 3.411
Authors: Jae-Ik Lee; Richard Seist; Stephen McInturff; Daniel J Lee; M Christian Brown; Konstantina M Stankovic; Shelley Fried Journal: Elife Date: 2022-05-24 Impact factor: 8.713