A Novel MEMS Based Piezoresistive Vector Hydrophone for Low Frequency Detection

Presented in this paper, is a MEMS-based piezoresistive vector hydrophone. It is desirable that the application of piezoresistive effect and ingenious structure of the hydrophone may improve the low-frequency sensitivity of vector hydrophone as well as its miniaturization. The structure of this hydrophone consists of two parts: high-precision four-beam micro-structure and rigidity plastic cylinder which has the same density of water. The four-beam micro-structure consists of four vertical cantilever beams, and the whole structure is completely axial symmetry in the xoz plane and yoz plane. The fabrication of the micro-structure is completed by means of standard silicon-based MEMS technology, the properties of prepared vector hydrophones has been measured both by vibration-platform and in sound absorbing pool. The experiment results show that fabricating vector hydrophone based on theory of piezoresistive effect and MEMS technology is feasible. Both finite element modelling and experimental result give very close results of the resonance frequency of the device. This kind of hydrophone not only has several advantages such as small volume, light weight as well as simple structure, but also possesses directional pattern in form of "8"-shape.