Transcutaneous Induction-Power and IR-Data Linked, Long-Duration, Implantable Neural-Interface System

Abstract

Efforts to combat the devastating effects caused by neurological disorders and injuries have been a topic of research for decades. Presently, neuroprosthetics, like cochlear implants, are in common use and effectively restore some degree of biological function. This field, however, is far from mature and the development of neuroprosthetics for other biological systems is extraordinarily challenging. This dissertation presents a system-level design of an implantable, fully-wireless, neural-interface research platform. The implantable device, designed for implantation into the abdominal region of a rat, can reside in an enclosure cavity measuring 18.0 mm wide, 26.0 mm long and 12.49 mm high. It includes an MSP430 running a custom operating system and 264 Mbit of non-volatile memory to store recorded neural data from an Intan RHS2116. An onboard lithium-ion battery, which is recharged by wireless power, provides over ten minutes of energy for a neurological stimulation and recording experiment. Data transfer and wireless power are accomplished via interaction with a custom-designed base station. Transdermal wireless communication is achieved with IR communication in the near-infrared region. Downlink data transmission was measured at 115.2 kbps through 5.5 cm of free space, 0.8 mm of sapphire crystal and 4.0 mm of phantom tissue with a packet-loss rate of 0%, given a sample of 10000 transmitted packets. Uplink communication reached 2 Mbps with zero packet errors out of a sample of 10010 transmitted packets at a separation distance of 2.7 cm through a combination of free space, 0.8 mm of sapphire crystal and 3.0 mm of phantom tissue. Inductively-coupled resonators, operating at 13.56 MHz, provide wireless-power capabilities. 243 mW of power was delivered, post rectifier, to the implant voltage-regulator output at 2.3 cm. End-to-end wireless-power efficiency at this distance was 3.34%, and at a distance of 3.2 cm, 195 mW was successfully transferred.