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

: Goßler, C.; Bierbrauer, C.; Moser, R.; Kunzer, M.; Holc, K.; Pletschen, W.; Köhler, K.; Wagner, J.; Schwaerzle, M.; Ruther, P.; Paul, O.; Neef, J.; Keppeler, D.; Hoch, G.; Moser, T.; Schwarz, U.T.


Journal of Physics. D. Applied Physics 47 (2014), Nr.20, Art.205401, 6 S.
ISSN: 0022-3727
ISSN: 1361-6463
Fraunhofer IAF ()
cochlear implants; optogenetics; micro-LED array; flexible substrate

Currently available cochlear implants are based on electrical stimulation of the spiral ganglion neurons. Optical stimulation with arrays of micro-sized light-emitting diodes (µLEDs) 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 15 µm 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 × 50 µm(2) LEDs are contacted via conducting paths on both pand n-sides of the LEDs. Up to three separate channels could be addressed. The probes, composed of a linear array of the said µLEDs bonded to the flexible polyimide substrate, are peeled off the carrier wafer and attached to flexible printed circuit boards. Probes with four µLEDs and a width of 230 µm are successfully implanted in the mouse cochlea both in vitro and in vivo. The LEDs emit 60 µW at 1 mA after peel-off, corresponding to a radiant emittance of 6 mWmm(-2).