A 2-DOF wideband electrostatic transducer for energy harvesting and implantable applications

This paper reports the modeling, fabrication and characterization of a SOI-based electro-mechanical transducer used for energy harvesting. The electrostatic transducer couples the ultrasonic energy with the vibration of a seismic mass, converting ultrasonic mechanical energy into electrical energy by means of polarized movable capacitor with comb structures. To extract ambient kinetic energy with arbitrary motion directions, this paper introduces a novel 2D resonator with resonance frequencies of 38520 Hz and 38725 Hz. Working in diagonal direction, the -10 dB bandwidth is 302 Hz, twice wider than 1D resonator devices. The measured dynamic frequency response shows that a maximum peak-to-peak output voltage of 10 mV can be obtained through a 1 M ohm resistive load, and the harvested power is calculated as 0.1 nW. Potential applications for powering battery-free implanted biomedical devices are also discussed in this paper.