Beam-Membrane Coupled Piezoelectric Micromachined Ultrasonic Transducers with Enhanced Transmitting Sensitivity

Abstract

Piezoelectric micromachined ultrasonic transducers (PMUTs) are a promising alternative to conventional bulk piezoelectric ceramic-based ultrasonic transducers. However, the transmitting sensitivity of the reported PMUTs is far from satisfactory. In this paper, we report a beam-membrane coupled PMUT (BM-PMUT), which enhances the transmitting sensitivity via simultaneously increasing the acoustic emission areas and maintaining the comparable vibration amplitude. Experimental results show that the center and edge transmitting sensitivities of the BM-PMUT are 108.1 and 96 nm/V at 370 kHz, which are 109.9 and 49.6 nm/V at 677 kHz for the traditional PMUT (T-PMUT). Thus, the BM-PMUT realizes piston-like mode shapes and achieves around twofold improvement in the effective acoustic emission area relative to the traditional T-PMUT of the same size. Due to the larger acoustic emission areas and comparable vibration amplitudes, the normalized far-field sound pressure level of the BM-PMUT is 8.5 dB higher than that of the T-PMUT.

Micromechanical piezoelectric micromachined ultrasonic transducer array package enhancement with integrated frontliners

“…Failing to achieve impedance matching between the PMUT and the medium can lead to the attenuation of acoustic pressure, resulting in undetectable signals. Moreover, the structure of the matching layer is crucial in increasing the resilience of PMUT arrays to external stress and preventing the rupture of piezoelectric films [14]. Therefore, as a strategy to increase the sensitivity and lifetime of PMUT arrays, the design of the matching layer is receiving increasing attention.…”

Editorial for the Special Issue on Micro and Smart Devices and Systems

“…However, the reported emission sensitivities of PMUTs are far from satisfactory. Mengjiao Qu et al [ 9 ] report a beam-membrane-coupled PMUT (BM-PMUT) that improves the emission sensitivity by simultaneously increasing the sound emission area and maintaining comparable vibration amplitudes. In their report, BM-PMUTs achieve a piston-like mode shape, leading to approximately a twofold improvement in effective sound emission area compared to traditional T-PMUTs of similar size.…”