An Efficient Acoustic Power Transfer Using a Self-Biased Electrostatic MEMS Transducer

This paper presents the analysis, design and experimental characterisation of an electronic circuit that raises capacitive MEMS transducers to the level of piezoelectric transducers for acoustic energy transfer through the skin. Capacitive micromachined ultrasonic transducers (CMUTs) are competitive with commonly used piezoelectric transducers. However, as their efficiency depends on their static bias voltage (typically $40 \sim 120 \mathrm{~V}$), they are not commonly used in body implanted devices. This work proposes a discrete electronic circuit that builds a 60 V bias voltage from a 2.2 V battery voltage and charges the same battery with an ultrasonic-to-electrical energy conversion efficiency of 16.6%.