A non-resonant kinetic energy harvester for bio-implantableapplications

Bio-implantable devices are attracting much attention, as they provide effective solutions for monitoring and treatment of diverse health problems. Examples for already-developed devices include pressure sensors, pacemakers, muscle stimulators, and glucose sensors that can control and monitor diseases ranging from heart-related disorders to diabetes. Batteries that are currently used in bio-implants have limited energy storage capacities, requiring frequent battery replacements and thus limiting the functionality of such medical devices. In this respect, energy harvesting from human body movements offers a promising alternative as on-board power for implantable medical devices. The aim of this project is to develop an implantable power generator capable of converting the kinetic energy existing in body movements into electricity at any part of the body. The generator is designed to be bio-compatible with a volume less than 1 cm3 for implantability. Energy is generated from daily activities such as walking, running, and twisting through the utilization of electromagnetic induction principles. An important aspect of the design is the non-resonant device nature. Accordingly, it is possible to generate energy from a variety of body activities at different frequencies. Simulations were performed on COMSOL software for design optimization. The device was manufactured using a combination of micro-fabrication and CNC technologies. Initial testing on a linear shaker platform resulted in an open circuit voltage and output power of 6.25 mV and 0.33 µW, respectively. The device was integrated on a wristband to test real-life performance. The voltage and power during normal walking were measured to be 4.4 mV and 0.14 µW. These values increased to 6.85 mV and 0.2 µW when running. Several improvements in the design and testing scheme were proposed to take these values at even higher levels. The findings and results reported here are important steps forward to develop electronic self sufficient bio-implants that do not need battery replacements and can generate their own energy autonomously in the body.