Integrated CMOS wireless power transfer for neural implants

Wireless power transfer is commonly realized by means of near-field inductive coupling and is critical to many existing and emerging applications in biomedical engineering. We present simulation results that support the possibility of an integrated receiver coil on a CMOS substrate useful for neural implants. It is shown that by following simple guidelines such structures can deliver power in the 10-20 miliwatt range while the transmitter with 100mW transmit power and the receiver are separated by 10mm of biological tissue. The results indicate that the optimum coil geometries only require a few turns and the optimum frequency for an on-chip power receiver is approximately 100MHz. We conclude by way of a case study that uses an integrated CMOS receiver buried under 10mm of skin, fat, skull and dura that achieves 18% power transfer efficiency.