Design optimization of contactless generator for implantable energy harvesting system utilizing electrically-stimulated muscle

Abstract

We propose an energy harvesting device driven by a contraction of an electrically-stimulated skeletal muscle for an alternative battery of implantable medical devices. In order to realize a durable generator, we proposed a contactless plucking mechanism utilizing parallel leaf springs and magnets, with which the generator can be driven without friction. By utilizing this mechanism, the generator can be driven not only in a contraction phase, but also a relaxant phase. We optimized the stiffness of the parallel leaf springs, air gap between the magnets, and magnetic circuit in order to maximize generated power of the generator. The generated power of the prototype in nonliving environment was evaluated. The result showed the protype could achieve 35.8 μW, the value of which is enough to drive the implantable medical devices. Finally, the generated power was evaluated in the ex-vivo experiment using a gastrocnemius muscle of a toad with a weight of 193.4 g. In this experiment, the generator achieved 18.1 μW from only 3.5 g of the skeletal muscle. Also, we confirmed that the generated power exceeded the power consumption of the electrical stimulation on the skeletal muscle. Hence, we concluded the results showed the feasibility of the energy harvesting system with proposed mechanism.