Wireless Energy and Data Transfer for In-Vivo Epileptic Focus Localization

This paper presents a wireless energy transfer and a wireless data communication link for neural signal monitoring-more specifically, fast ripple detection for epilepsy patients. Wireless data are transferred on the same channel as the wireless energy transfer link by shifting resonance frequency of the implanted part. The remote powering link consists of a four-coil resonant inductive link structure and a power management unit on the implant side. Modulated information on the implant is demodulated using an envelope detector type amplitude shift keying demodulator in the external unit. Power transfer efficiency in air without data communication is measured as 36% for 10 mW output power at 8.4 MHz excitation frequency, while the external and the implanted coils are separated by 10 mm. Under the same experimental conditions, 1 Mbit/s data communication is achieved while maintaining a power transfer efficiency of 33%. Moreover, in-vitro tests employing mock cerebrospinal fluid are performed and 1 Mbit/s data communication is performed with an efficiency of 33% while all other parameters are preserved. Finally, hermetical sealing capability of the packaging that is composed of epoxy and Parylene-C is successfully tested for one month to evaluate the implant's short-term performance.