CMOS Neural Probe With Multi-Turn Micro-coil Magnetic Stimulation

Micro-coil magnetic stimulation has been shown to be an effective method of neurostimulation while circumventing issues that limit the more commonly used implantable electrodes. Micro-coils do not need direct electrical contact with biological tissue, allowing for complete device encapsulation. This allows for the stimulation effectiveness to be maintained over long periods of time and eliminates the electrode-tissue interface, which is prone to electrochemical effects that can damage the probe and/or tissue. Recent work has demonstrated programmable micro-coil neural probes integrating CMOS technology with the micro-coil design. This work proposes a neural probe that co-optimizes a multi-turn micro-coil design with configurable CMOS current drivers for each micro-coil to maximize the induced electric field gradients. A four wire interface is used to multiplex power, deliver the stimulation current, and program the micro-coil current configuration. The proposed probes are characterized in a saline bath with a maximum stimulation current of 9 mA per 16-turn micro-coil, when simultaneously driving two micro-coils on a 3.5 V supply. Preliminary in vitro testing with mouse olfactory bulb slices and a commercial MEA show the probes are capable of producing changes in neural behavior.