Electrostatic Energy Harvesting of Kinetic Motions Using a MEMS Device and a Bennet Doubler Conditioning Circuit

This work is concerned with the design of a microelectromechanical system (MEMS) device that can harvest kinetic energy from its environment using only classical microfabrication techniques. The device is composed of a cantilever beam, where a proof mass is linked to its tip in order to tune the natural frequency of the device. Two stationary electrodes are standing side by side with the cantilever beam to form two out-of-phase variable capacitances with a rotary interdigitated design suitable for flexural bending motions. A Bennet doubler is implemented as a conditioning circuit while taking advantage of the variable capacitances to harvest the kinetic energy of the beam. Finite element modeling is used to estimate the variation of the capacitance and deduce an analytical model from the results. For the dynamic response, a reduced-order model based on a single-mode projection is derived and numerically solved, from the equation of motion of the beam. The response of the system depicts a clear benefit regarding the harvested energy kept in a storage capacitance.