Soft Variable Area Energy Harvester

Abstract

Capacitors are great tools to store electrostatic energy and can discharge current almost instantly when needed. Thus, they are widely used in electrical circuits and have become a crucial part of everyday life. Besides, variable capacitors are a vital component of electrostatic energy harvesters that can harvest mechanical energy. However, traditional rigid capacitors exhibit low capacitance due to a thick dielectric layer in between the electrodes limiting the charge storing capacity. Due to their rigid nature, harvesting mechanical energy by varying capacitance is limited to sliding or oscillating the electrodes up and down in a systematic way. Thus, they cannot convert all kinds of mechanical energy into electricity constraining the conversion efficiency. Here we create soft electrical double layer capacitors, which innately offer higher capacitance due to the small distance between the charged layers. Being deformable in nature, they can convert all kinds of mechanical input (slide, stretch, squish, twist, bend) into electrical energy. These devices generate around 0.23 mW m-2 by harnessing energy from mechanical motion without the need for an external power source unlike the traditional electrostatic energy harvesters. We have characterized the behavior of these devices as a function of several parameters including material properties and physical deformation. The devices behave as expected and the response of the devices to deformation match a physics-based model. The soft device generates an electrical signal when deformed, which may be useful for oceanic energy harvesting as well as wind energy harvesting. Besides, these devices can harvest human motion thereby find applications in wearable electronics, healthcare systems like rehabilitation and prosthetics.