A 4-DOF MEMS Energy Harvester Using Ultrasonic Excitation

This paper presents a microelectromechanical systems (MEMS)-based energy harvester that is designed to harvest electrical energy from an external source of ultrasonic waves. The harvester features a novel 4-degree-of-freedom (DOF) mechanical design that uses three translational resonance modes and one rotational mode, with electrostatic transducers being implemented to perform the conversion of mechanical to electrical energy. The 4-DOF design of the system allows energy to be harvested regardless of the device's orientation, which holds particular benefits for potential applications that include the powering of implanted biomedical devices. Full characterization of the fabricated MEMS harvester is performed, which shows that the device is able to generate electrical power outputs of 180, 189, and 49.1 nW due to ultrasonic excitation from the x-, y-, and z-directions, respectively.