An Electret-Based Angular Electrostatic Energy Harvester for Battery-Less Cardiac and Neural Implants

Abstract

The implantable microsystems are conventionally powered using batteries that have limited life-span and bio-compatibility issues. Hence, energy harvesting as an alternate and continuous power source in miniaturized implantable medical devices, especially cardiac and neural implants, has been investigated in this paper. An electret-based electrostatic energy harvester has been proposed with angular electrode structures along with a switching converter circuit to harvest maximum possible energy. The proposed harvester incorporates the properties of both area-overlap and gap closing topologies to achieve larger capacitance variation with respect to displacement, as is observed in the results. The maximum power that can be scavenged from the proposed harvester with an active surface area of $2.5\times 3.5$ mm2 and volume 0.4375 mm3 at maximum displacement is $9.6~\mu \text{W}$ ; along with a maximum power per unit surface area of $109.71~\mu \text{W}$ /cm2, which is within the advised limit of power density for in vivo implantable applications. Hence, the proposed electrostatic harvester can be used as a power source for cardiac and neural implants.