Piezoelectric energy harvesting and ultra-low-power management circuits for medical devices

Piezoelectric energy harvesting enables the development of sustainable, batteryless medical devices, powered by microwatts level energy transduction and low frequency body area motions. To optimize the energy harvested by piezoelectric materials, energy harvesting circuits are needed to maximize extraction suitable for powering medical devices. This paper reviews the state-of-the-art energy harvesting and management circuits for self-powered implantable and wearable medical devices. Both laboratory and commercially available self-powered piezoelectric implantable and wearable systems are described. Power consumption, power transfer efficiency, energy stability, and system reliability of various piezoelectric materials and power harvesting and management circuits are compared and analyzed. The paper provides a comprehensive review of the many state-of-the-art integrated ultra-low-power management circuits that can significantly enhance the device power output extracted by up to tenfold. It includes power harvesting interface, dc-dc converters, maximum power point tracking, and cold start-up circuits. Finally, guidelines are presented for the choice of optimum designs to address the limitations and provide medical devices with reliable and highly efficient power harvesting at nanowatts level.