1024-channel-scalable wireless neuromonitoring and neurostimulation rodent headset with nanotextured flexible microelectrodes

We present a compact wireless headset system for simultaneous multi-site neural recording and neurostimulation in the rodent brain. The system comprises flexible-shaft microelectrodes, neural amplifiers, neurostimulators, a digital time-division multiplexer (TDM), a micro-controller and a ZigBee wireless transceiver. The system is built by parallelizing up to four 0.35μm CMOS integrated circuits (each having 256 neural amplifiers and 64 neurostimulators) to provide a total maximum of 1024 neural amplifiers and 256 neurostimulators. Each bipolar neural amplifier features 54dB-72dB adjustable gain, 1Hz-5KHz adjustable bandwidth with an input-referred RMS noise of 7.99μV and dissipates 12.9μW. Each current-mode bipolar neurostimulator generates arbitrary waveform programmable biphasic currents in the range of 20-250μA and dissipates 2.6μW in the standby mode. Reconfigurability is enabled by stacking a set of dedicated mini-PCBs that share a common signaling bus within as small as 22×30×15mm³ volume. The system features flexible polyimide-based microelectrode array design that maximizes pad packing density. Electrodeposition pad nanotexturing reduces the electrode-tissue interface impedance from an average of 2MΩ to 30K at 100Hz. The system has been validated in vivo in Sprague-Dawley rats.