A piezoelectric micro-cantilever acoustic vector sensor designed considering fluid–structure interaction

We developed a piezoelectric micromachined cantilever acoustic vector (PEMCAV) sensor. We modeled the device using a “lumped” approach that considers fluid–structure interaction, the piezoelectric effect, and the mechanical impedance of the cantilever. Due to the high flexibility, the influence of the medium is significant, so fluid–structure interaction must be considered in theoretical modeling. We compared the model data to experimental results. The design parameters optimized using the derived analytical open-circuit sensitivity equation are presented, and the physical characteristics of the sensor are discussed. We used a micromachining technique to fabricate the sensor, added a preamplifier, and tested it using a reference hydrophone under a frequency range of 100 Hz–1 kHz. The analytical predictions and experimental results were in good agreement with respect to frequency response and the directivity of the sensor. Even when the sensor was much smaller than the wavelength (ka≪1), the proposed sensor exhibited a typical cosine directivity pattern, and the measured sensitivity at 100 Hz was −194 dBV/μPa.