A miniaturized, wirelessly-powered, reflector-coupled single channel opto neurostimulator

We report a free-floating, wirelessly-powered, single channel opto neurostimulator consisting of a reflector-coupled microscale light emitting diode (μLED) and a mm-sized receiver (Rx) coil for untethered optogenetics neuromodulation. An optimized two-coil inductive link delivers over 4 mW instantaneous power at a low operating frequency to continuously drive the μLED while minimizing device invasiveness and tissue exposure to electromagnetic radiation. The reflector-coupled μLED enables significantly enhanced light intensity compared to a bare μLED. The temperature increase of the activated stimulators is <;1 °C, well below the safety limit of biomedical implants. In vivo experiment and histological analysis verify the efficacy of wireless optical stimulation in the rat cortex, using c-Fos as a report of light-evoked neuronal activity.