Design and Fabrication of Cross-Beam Integrated Microsphere Piezoelectric MEMS Vector Hydrophone

High-performance vector hydrophones that can acquire underwater acoustic vector information are crucial to the effectiveness of underwater target monitoring. In this article, a novel piezoelectric MEMS vector hydrophone (PMVH) is proposed with <tex-math notation="LaTeX">d_31 </tex-math> working mode, which has a cross-beam integrated microsphere structure. The passive acoustic receiving unit has been integrated for a low-density microsphere instead of the ordinary cilium by increasing the sensing area of the receiving unit. Heterogeneous integrated preparation of high-quality PbZr <tex-math notation="LaTeX">_0.52 </tex-math> Ti <tex-math notation="LaTeX">_0.48 </tex-math> O3 (PZT) thin film was realized on the cross-beam by sol-gel technology. The optimized geometric size of the sensitive structure was determined by simulation analysis. Based on the optimized parameters, the microelectron mechanical systems (MEMS) technology was employed to fabricate the hydrophone microdevices, and a prototype of the PMVH has been assembled. The PMVH is verified experimentally in a standing bucket wave calibration system. The experimental results show that compared to the bionic cilia MEMS vector hydrophone (CVH), the receiving sensitivity reaches up to −177.71 dB (re 1 V/ <tex-math notation="LaTeX">μ </tex-math> Pa) at 1000 Hz, which is higher than 19.3 dB. Moreover, the bandwidth of the PMVH reaches 20–1150 Hz, which exhibits a satisfactory eight-shaped directivity. The results of this work pave a new way for development of piezoelectric hydrophones for underwater communications and acoustic monitoring.