A Novel Piston-Like Piezoelectric Micromachined Ultrasonic Transducer Based on Mass Loading Effect

This paper proposes a novel piezoelectric micromachined ultrasonic transducer (pMUT), through using MEMS technology to form a proof mass on the central circular diaphragm. Compared with the traditional pMUT, the proposed pMUT has advantages: (1) The resonant frequency of pMUT can be adjusted by proof mass; (2) The mode shape changes from Gaussian-like to piston-like, which enables higher output power. The resonant frequency and output power characteristics of pMUT with different proof mass thickness and diameter are analyzed. In this work, the sound pressure level of 160 dB at 8.86 MHz is achieved, which is 4 dB higher than that of the traditional pMUT benefiting from the piston diaphragm movement. This work provides constructive advice for designing pMUT for better performance of transmission.