A piezoelectric micro-cantilever acoustic vector sensor

An acoustic vector sensor measures the direction of wave propagation as well as the acoustic pressure. We investigate feasibility of using a piezoelectric micro-cantilever (PEMC) as an acoustic vector sensor in water at the frequencies range below 500 Hz. In order to measure the propagation direction, we try to devise the properties of a PEMC so that its deflection is proportional to the particle velocity due to acoustic waves. We found that the desired property can be obtained with PEMC if it is designed to be flexible enough. Under the assumption that the PEMC affects little on the wave propagation, we have developed a simple lumped parameter model to predict the relationship between the acoustic pressure of a progressive wave and the deflection of PEMC. The developed model shows that the deflection of PEMC is dependent on the magnitude and direction of the incoming progressive wave. In addition, the frequency of the wave is also found to affect the responses of PEMC. Based on the developed simple lumped parameter model, a PEMC acoustic vector sensor was designed with PEMC of 400 μm long 200 μm wide 5.25 μm thick for operating around 200 Hz. The designed PEMC acoustic vector sensor was fabricated by micro-machining and packaged inside cater-oil-filled rubber housing so that it can be tested in the water. The expected dependence of the fabricated PEMC on the direction and acoustic pressure can be observed in the experiments at the target frequency range.