A transceiver integrated piezoelectric micromachined ultrasound transducer array for underwater imaging

In this article, a scandium-doped aluminum nitride (Sc0.2Al0.8N) piezoelectric micromachined ultrasound transducer (PMUT) array for underwater imaging is presented. The reported PMUT array integrates a transmitter and a receiver in one transduction cell, in which the outer top electrode is used for transmitting while the inner top electrode is employed for simultaneously receiving ultrasonic waves, respectively. A 7 × 8 transduction cell array with characteristic size of 500μm is designed in a bioinspired honeycomb architecture and developed based on a piezoelectric on silicon-on-insulator (SOI) platform. The top electrode of the transduction cell is split into the outer and inner sections with the optimized size ratio for achieving transceiver integration in one cell. The fabricated PMUT array exhibits a transmit sensitivity of 146.59 dB (re: 1 μPa/V), and a receive sensitivity of −173.70 dB (re: 1 V/μPa) at its resonant frequency of around 150 kHz in water. In order to demonstrate the feasibility of underwater imaging, the PMUT array and its signal conditional circuits are packaged using an acoustically transparent material. Ultrasonic pulse-echo imaging with the developed PMUT array is demonstrated without implementation of a switching circuit to separate the transmit and reflected signals, due to the transceiver integration approach proposed in our work. This work demonstrates the feasibility of underwater imaging for the transceiver integrated PMUT array, which has great commercial value for minimized and portable underwater imaging.