Source: Sadeghpour, Sina, Michael Kraft, and Robert Puers. "Highly Efficient Piezoelectric Micromachined Ultrasound Transducer (PMUT) for Underwater Sensor Networks." In 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), pp. 162-165. IEEE, 2019.
A low voltage (<3V) PMUT based ultrasound transducer to perform ultrasonic communication for underwater sensor nodes at distances of 1-2 m is presented. The parasitic components of the PMUT array were minimized to improve its frequency response and power consumption. For the first time, the concept of coupled Piezoelectric Bulk Micromachined Ultrasound Transducer (cPB-MUT) is introduced. In a cPB-MUT, the small PMUT elements are coupled to the bulk silicon substrate through the vibration of water, which produces a strong vibration in the entire substrate. This leads to a 209 Pa/V@1cm transmission sensitivity and above 43dB SNR@20cm, at 33 kHz underwater, using 3 Vp-p.