GaN-based micro-LED arrays on flexible substrates for optical cochlear implants

Abstract

Currently available cochlear implants are based on electrical stimulation of the spiral ganglion neurons. Optical stimulation with arrays of micro-sized light-emitting diodes (LEDs) promises to increase the number of distinguishable frequencies. Here, the development of a flexible GaN-based micro-LED array as an optical cochlear implant is reported for application in a mouse model. The fabrication of 15m thin and highly flexible devices is enabled by a laser-based layer transfer process of the GaN-LEDs from sapphire to a polyimide-on-silicon carrier wafer. The fabricated 50 50m2 LEDs are contacted via conducting paths on both p- and n-sides of the LEDs. Up to three separate channels could be addressed. The probes, composed of a linear array of the said LEDs bonded to the flexible polyimide substrate, are peeled off the carrier wafer and attached to flexible printed circuit boards. Probes with four LEDs and a width of 230m are successfully implanted in the mouse cochlea both in vitro and in vivo. The LEDs emit 60W at 1mA after peel-off, corresponding to a radiant emittance of 6mWmm-2. © 2014 IOP Publishing Ltd.