Triboelectric hydrophone for underwater detection of low-frequency sounds

A hydrophone is the core part of sonar and plays an important role in underwater acoustic detection applications. However, there is still room for hydrophones to improve their ability to detect low-frequency signals in their fabrication, dimensions, sensitivity, and types. This study presents an innovative triboelectric hydrophone (TH) for high-sensitivity detection of underwater low-frequency sound. The TH consists of a hemispherical shell, an acoustic coupling agent, and a multi-layer membrane triboelectric nanogenerator (TENG). When utilizing the acoustic impedance matching among water, the shell, and the coupling agent, sound waves could easily penetrate the waterproof shell into the coupling agent. Then, the sound waves can be received and converted into electrical signals by the TENG. The TH has the characteristics of a working frequency ranging from 30 Hz to 800 Hz and a heart-shaped directional pattern. The receiving sensitivity of the TH is greater than − 192 dB in the frequency range from 150 Hz to 500 Hz, which offers remarkable sensitivity to low-frequency sounds. With these capabilities, the TH is demonstrated for detecting underwater sounds generated by objects falling and other sources. The results indicate that the exploration of TENG-based underwater acoustic devices offers a promising avenue for the development of hydrophones.