Design and development of PVDF-based hydrophone for underwater applications

Abstract

Traditional ceramic-based hydrophones are exposed to low flexibility and narrow sensing band in low-frequency applications, which limits their usage in underwater acoustic sensing. To address the limitations, a hydrophone based on a stacked polyvinylidene-fluoride (PVDF) architecture is proposed. The designed hydrophone is made of four 1 mm PVDF layers stacked with three copper electrodes, whereas the two PVDF pairs are poled in opposite directions such that bending-induced charges cancel, but hydrostatic charges add constructively enhancing sensitivity and robustness. Finite-element simulations using solid mechanics and pressure acoustics modules in COMSOL Multiphysics are utilized to determine layer stresses and the modal response. Parametric sweeps indicate that a 2 mm polyurethane jacket provides the best compromise between acoustic transparency and structural damping. In FEM simulations, a flat open-circuit sensitivity of −203 ± 1 dB re 1 V/μPa up to 6 kHz is achieved. The hydrophone fabrication was processed through epoxy-bonded lamination followed by low-pressure polyurethane molding and then calibrated in a Colmar T1 standing-wave tube (100 Hz–1.2 kHz). Experimental free-field voltage sensitivity of −203 ± 2 dB re 1 V/μPa is achieved, which is within ±2% error of the simulated model, validating the accuracy of the electromechanical coupling.