Ultrasonic power and data transfer for active medical implants using adaptive beamforming

Wireless power transfer provides a sustainable power source for active medical implants. Recent developments in biosensors, MEMS technologies and the advent of ubiquitous computing has opened up the potential for a millimeter-sized active medical implant for continuous health monitoring. Frequent wireless communication and data processing requires more energy than traditional active medical implants. Therefore, a continuous power source is needed. This study investigated the development of an ultrasonic power transfer (USPT) system for active medical implants. The system, comprised of a wearable and an implantable device, can transfer both power and data between the implant and the wearable. By implementing beamforming, it can adapt to misalignment between the transmitter and the receiver. In the experiments, the receiver outputs 0.16 mW after rectification, when transmitting through 0.5 cm of water. By measuring the time-of-flight (ToF) of a pulse transmitted from the receiver, implant position feedback is achieved. Data transfer is demonstrated at a rate of 1 kbit/s, across a 4 cm path in water, which is adequate for many biomedical applications.