IEEE Trans Biomed Eng. 2019 Feb;66(2):573-583. doi: 10.1109/TBME.2018.2850753. Epub 2018 Jul 10.
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.
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.
Systematic in vitro characterization showed that the TFEA's bending stiffness was 6.40 × 10 N·m near the base and 1.26 × 10 N·m 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 10 times less bending stiffness, 97% less electrode area, and comparable physiological thresholds.
Using a simplified structure and stable fabrication method, the present TEFA produced physical and physiological performance comparable to existing commercial devices.
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.
为了改进现有的手动组装的人工耳蜗电极阵列，我们制作了一种薄膜电极阵列（TFEA），其在 8mm 长度上的最大电极密度为 15 个电极，每个电极具有 75μm×1.8μm（直径×高度）的盘形电极。
所采用的微制造方法包括光刻胶转移、剥离、两步氧等离子体刻蚀和发烟硝酸释放，以降低剥离复杂性、保护金属层并提高释放效率。
系统的体外特性表明，TFEA 的弯曲刚度在基底附近为 6.40×10 N·m，在尖端附近为 1.26×10 N·m。TFEA 电极产生的平均阻抗为 16 kΩ，最大电流限制为 800μA，在盐水中使用单极刺激用 1-kHz 正弦电流测量。TFEA 原型被植入猫耳蜗，以获得单极刺激用 41-μs/相双相脉冲的电诱发听觉脑干和下丘的体内测量。这两种生理反应都产生了约 300μA 的阈值和 5-8dB 高于阈值的动态范围。与现有阵列相比，本 TFEA 的弯曲刚度低 10 倍，电极面积小 97%，但生理阈值相当。
使用简化的结构和稳定的制造方法，本 TFEA 产生的物理和生理性能与现有的商业设备相当。
本 TFEA 代表了朝着自动化过程的进一步发展，该过程可以取代人工耳蜗电极阵列的劳动密集型和昂贵的手动组装。
