An Aerosol Jet Printed Microcoil for Cochlear Micromagnetic Stimulation

A cochlear implant conveys a lost sensation of sound through direct electrical stimulation of responsive neural elements within the inner ear. Delivered from an implanted electrode array, the cochlea's frequency-to-place mapping enables users to achieve remarkable speech perception with these devices. Yet, performance variability persists, often due to a poor spectral representation caused by current spreading within the intracochlear fluid. As an alternative approach, magnetic stimulation involves pulsing electrical current through microcoils to locally induce electrical fields enhancing spatial selectivity. This work details the fabrication and testing of an aerosol jet printed (AJP) 4-turn, 600 µm diameter silver microcoil coated in Parylene-C for micromagnetic stimulation. The goal is to develop a post-processing approach to AJP directly on conventional cochlear arrays substrates optimized for atraumatic insertion and flexibility. With a measured upper current limit of 90 mA, coils were printed on planar and non-planar surfaces demonstrating an average inductance of 3.54 nH and 4.57 nH, and an average impedance of 35.47 + 3.19i Ω and 39.78 + 1.47i Ω, respectively.