Enhancement of piezoelectric micromachined ultrasonic transducer using polymer membrane for underwater applications

Abstract

An effort to enhance receiving response of piezoelectric micromachined ultrasonic transducers (pMUT) at low frequency was reported. PMUTs were fabricated with the vibrating membrane formed by a layer of polydimethylsiloxane (PDMS) polymer. Lead zirconate titanate, Pd (Zt,Ti)O₃ (PZT) was utilized as the piezo-active layer, sputtered with nickel electrodes. Spin coating and low temperature wafer bonding were proposed as part of the key fabrication methods. Fabricated transducers were characterized in the compact acoustic tank setup using 500 kHz and 1.25 MHz reference projectors. Analyses revealed the maximum receiving response was -36.6 dB re 1V of 200 kHz burst at 10 λ hydrophone-projector separations and 20 V peak to peak of drive voltage on reference projector. Finally, response spectrum of the transducer was plotted against two commercialized bulk hydrophones at equivalent frequency band for validation and comparison.