One major problem of implantable biomedical devices is the source of their power. Batteries, as the main source of current implantable devices, deplete after a few years and either the battery or the whole device needs to be replaced. Usually, this procedure involves a new surgery which is costly and could cause some risks for the patient. In this paper, we study the energy harvesting at small scale for powering implantable biomedical devices. The device consists of a layer of cultured cardiac muscle cells (cardiomyocytes) and a layer of piezoelectric polymer polyvinylidene fluoride (PVDF). The cardiac muscle cells with the desired thickness are grown over the PVDF layer and as the cardiac cells contract the piezoelectric layer deforms and produces electricity. The proposed device uses both piezoelectric and flexoelectric effects of the PVDF layer. At the smaller thicknesses the flexoelectric effect becomes dominant. The amount of power is on the order of multiple microwatts and is sufficient to power variety of sensors and implantable devices in the body. Unlike the battery technology, the proposed energy harvester is autonomous and lasts for the lifetime of patients. In this article, we explain the configuration of the proposed energy harvester, the natural frequency of the device is calculated, the power output is optimized with respect to the thickness of the PVDF, and a resistance sweep is performed to find the optimized resistive load.
An Analysis Model Combining Gamma-Type Stirling Engine and Power Converter
