A study of implantable power harvesting transducers

Abstract

The power harvesting technologies for low-power electronic devices, such as wireless sensor networks and biomedical sensor applications, have received a growing attention in recent years. Of all possible energy sources such as mechanical vibrations, electromagnetic radiations and magnetic fields, the mechanical vibrations have been considered a promising choice for power harvesting in a wide variety of applications. This paper presents the development of two different piezoelectric MEMS generators to harvest energy at different vibration frequencies. For power harvesting at 1.5kHz vibration frequency, we present a generator comprising a silicon micro-cantilever with laminated PZT (lead zirconate titanate) material, and the interdigital electrode on the top of the PZT layer to transform mechanical strain energy into electrical charges by using the d33 mode of PZT. The piezoelectric cantilever generator was tested with using a shaker as the external vibration source. For power harvesting at frequency higher than 20kHz, we present a piezoelectric disk-shaped generator which is packaged by cohesive gel. The power generation efficiency of the fabricated devices was characterized. For the application of the power to the implanted medical sensors, the piezoelectric MEMS generator is claimed to be a power receiver of an additional vibration sources. An experimental model was also developed to study the power transmission efficiency and the charge ability of the MEMS generator device. A feasibility study of the piezoelectric MEMS generator as a power receiver was performed and some testing results are presented.