Sarreal Ressa Reneth, Bhatti Pamela
College of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Sensors (Basel). 2020 Oct 26;20(21):6087. doi: 10.3390/s20216087.
According to the National Institute of Deafness and other Communication Disorders 2012 report, the number of cochlear implant (CI) users is steadily increasing from 324,000 CI users worldwide. The cochlea, located in the inner ear, is a snail-like structure that exhibits a tonotopic geometry where acoustic waves are filtered spatially according to frequency. Throughout the cochlea, there exist hair cells that transduce sensed acoustic waves into an electrical signal that is carried by the auditory nerve to ultimately reach the auditory cortex of the brain. A cochlear implant bridges the gap if non-functional hair cells are present. Conventional CIs directly inject an electrical current into surrounding tissue via an implanted electrode array and exploit the frequency-to-place mapping of the cochlea. However, the current is dispersed in perilymph, a conductive bodily fluid within the cochlea, causing a spread of excitation. Magnetic fields are more impervious to the effects of the cochlear environment due to the material properties of perilymph and surrounding tissue, demonstrating potential to improve precision. As an alternative to conventional CI electrodes, the development and miniaturization of microcoils intended for micromagnetic stimulation of intracochlear neural elements is described. As a step toward realizing a microcoil array sized for cochlear implantation, human-sized coils were prototyped via aerosol jet printing. The batch reproducible aerosol jet printed microcoils have a diameter of 1800 μm, trace width and trace spacing of 112.5 μm, 12 μm thickness, and inductance values of approximately 15.5 nH. Modelling results indicate that the coils have a combined depolarization-hyperpolarization region that spans 1.5 mm and produce a more restrictive spread of activation when compared with conventional CI.
根据美国国立耳聋及其他交流障碍研究所2012年的报告，全球人工耳蜗（CI）使用者的数量正从32.4万稳步增加。位于内耳的耳蜗是一种蜗牛状结构，呈现出一种音频拓扑几何形状，其中声波根据频率在空间上被过滤。在整个耳蜗中，存在着毛细胞，它们将感知到的声波转换为电信号，该电信号由听神经携带，最终到达大脑的听觉皮层。如果存在无功能的毛细胞，人工耳蜗可以弥补这一差距。传统的人工耳蜗通过植入的电极阵列将电流直接注入周围组织，并利用耳蜗的频率-位置映射。然而，电流会在耳蜗内的传导性体液外淋巴中扩散，导致兴奋扩散。由于外淋巴和周围组织的材料特性，磁场对外耳环境的影响更具抗性，显示出提高精度的潜力。作为传统CI电极的替代方案，本文描述了用于对耳蜗内神经元进行微磁刺激的微线圈的开发和小型化。作为实现适合耳蜗植入的微线圈阵列的第一步，通过气溶胶喷射打印制作了人体尺寸的线圈原型。批量可重复生产的气溶胶喷射打印微线圈直径为1800μm，迹线宽度和迹线间距为112.5μm，厚度为12μm，电感值约为15.5nH。建模结果表明，与传统人工耳蜗相比，这些线圈具有一个跨越1.5mm的联合去极化-超极化区域，并且产生的激活扩散更具局限性。
