Ultrasonic energy transmission and conversion using a 2-D MEMS resonator

This letter reports a novel ultrasonic-based method to power biosensors. Compared with commonly used radiofrequency radiation methods, ultrasonic power transmission is relatively safe for the human body and does not cause electronic interference. To extract ambient kinetic energy with arbitrary motion directions, a novel 2-D microelectromechanical systems energy converter is designed with resonance frequencies of 38520 and 38725 Hz. Working in the diagonal direction, the device has a bandwidth of 302 Hz, which is twice wider than that of a comparable 1-D resonator device. A storage capacitor is charged up to 0.95 V in 15 s, when the converter is driven by an ultrasonic transducer at a distance of 0.5 cm, indicating the energy-conversion capability of 21.4 nW.