Design and Optimization of a Dual-Channel Differential Triboelectric Sensor for Underwater Low-Frequency Acoustic Detection

This work presents a novel marine acoustic sensor based on a differential dual-channel triboelectric nanogenerator (TENG) design for underwater low-frequency sound wave detection. By constructing a magnetically levitated vibration pickup system and optimizing the suspension height of the magnetic vibration system, the sensor achieves a resonant frequency of 35 Hz at a compact size of 18 mm in length, exhibiting high sensitivity to low-frequency acoustic waves and potential for deep-water applications. The differential sensing mechanism of the dual-channel TENG not only doubles the output voltage sensitivity of the triboelectric sensor but also significantly enhances its common-mode noise rejection capability. Compared to single-channel TENG sensors, the dual-channel differential TENG vector sensor (DTVS) demonstrates a markedly improved signal-to-noise ratio (SNR). The fabricated DTVS operates within a frequency range of 20–100 Hz, achieving a maximum sensitivity of 16.7 V/g in air. Underwater, its equivalent sound pressure sensitivity reaches up to −178.8 dB, with sensitivity fluctuations below 10 dB across the 20–100 Hz frequency band. Compared to traditional 8105 piezoelectric hydrophones, the DTVS exhibits superior low-frequency sensitivity and a more compact size. Additionally, it outperforms fiber-optic hydrophones and MEMS cilium hydrophones in terms of system simplicity, self-powered operation, and cost-effectiveness. The DTVS demonstrated a working depth of up to 200 m underwater, with horizontal and vertical directivity resolutions reaching 30 dB, highlighting its promising potential as an underwater acoustic vector sensor.