In Situ Observing Ciliary Biomimetic Three-Dimensional Vector Hydrophone

The miniaturization of low-frequency marine underwater acoustic detection systems presents new requirements for 3-D vector hydrophones. Inspired by fish lateral lines, we have introduced a biomimetic 3-D vector hydrophone. It features a microstructure with a monolithically integrated four-beam central block and cilium, capable of detecting underwater acoustic signals from three dimensions. Simulations were conducted to determine the natural frequencies and stress of the hydrophone, helping establish the structural parameters. The arrangement of piezoresistors on the four beams was meticulously designed to minimize interaxis coupling. The hydrophone chip was fabricated using the MEMS technology, followed by comprehensive testing. The hydrophone effectively operates within a detection frequency band of 20–500 Hz. The sensitivities for the three axes are −189 dB at 500 Hz, −189.6 dB at 500 Hz, and −200.9 dB at 500 Hz (0 dB = 1 V/<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>Pa), respectively. The concave point depths are 30.4, 29.8, and 26.9 dB, with the voltage density of self-noise at −106 dB at 500 Hz. These results indicate that the biomimetic 3-D vector hydrophone holds promising prospects for low-frequency underwater acoustic detection applications.