Energy harvesting exploits a variety of physical effects, including the piezoelectric effect that uses kinetic energy in the environment. A team led by Professor Susan Trolier-McKinstry of Penn State University in Pennsylvania is looking into this. The researchers coated both sides of a flexible metal foil with the piezoelectric material PZT to construct a wristwatch-sized device. It contains a freely rotating eccentric brass rotor with an embedded magnet and multiple PZT beams with a magnet on each beam. When the rotor magnet approaches one of the beams, the magnets repel each other and deflect the beam. The slow frequency of a moving wrist is thus converted into a higher frequency vibration, considerably increasing the effectiveness of the piezoelectric element .
Energy harvesters are used to power devices on the Internet of Things (IoT). They make it possible to provide a rechargeable battery or a supercapacitor with a continuous supply of electricity, thus reducing the costs of battery replacement and improving sustainability.