A Temperature-Aware Fully-Wireless mm-Scale Optically-Enhanced Optogenetic Neuro-Stimulator

The design, development, and experimental validation of an inductively-powered 4-channel optical neuro-stimulator integrated circuit (IC) with on-chip neural recording, temperature monitoring, signal processing, and bidirectional wireless data communication are presented. Each stimulation channel employs a novel current amplifier that drives 0.1-10mA into the channel's dedicated µLED with only 150mV required headroom (smallest reported in literature). The amplifier yields a constant gain of 850A/A for the entire output current range, despite experiencing large supply voltage variations. The system's energy efficiency is further improved by inkjet printing of custom-designed optical µlenses on top of the device to enhance the generated light directivity. The chip is capable of simultaneous optical stimulation and LFP monitoring, that allows for on-the-fly stimulation parameter adjustment. A high-precision (0.1°C) temperature readout circuit is also integrated on the chip to shut off stimulation upon detection of an unsafe temperature increase. The IC is fabricated in a standard 130nm CMOS process and occupies 6mm
²
. Measurement results for different sensory/communication blocks are presented, as well as in-vitro experimental validation results showing simultaneous optical stimulation, electrical recording, and calcium imaging.