A self-powered acoustic sensor excited by ultrasonic wave for detecting and locating underwater ultrasonic sources

Triboelectric nanogenerators (TENGs) have great potential for utilizing acoustic energy. However, as for the ultrasonic source, the high frequency vibration may aggravate mechanical wear and weaken the stability of the TENG device. Meanwhile, the reported complicated structure design and fabrication greatly hinder the development of TENG for ultrasonic energy harvesting. In this study, we find an interesting phenomenon that perfluorinated polymer film under sonication can be separated from its attached adhesive. Based on this ultrasoundinduced separation, an easy-fabricated and compact-structured ultrasound-driven TENG (UD-TENG) is proposed to harvest ultrasonic energy in a facile way. The mechanism of the coupling between weak adhesion of perfluorinated polymer film and ultra-high ultrasonic pressure verified by simulation and experiment is investigated. The relationship between the surface energy and the film-adhesive separation force is determined by comparing different films. Furthermore, the intensity and direction of ultrasound further reveals the effect of ultrasound parameters on UD-TENG's output performance. UD-TENG can achieve high charging rate of 75 mu C/s and exhibit excellent stability with no obvious attenuation of the voltage signal after sonicating for 1 h. A series of practical devices driven by the UD-TENG serving as power supplier are demonstrated. Finally, a self-powered acoustic sensor which can collect ultrasonic signal from multiple angles is developed for underwater ultrasonic wave detection and sound source location. This work provides a new guidance for the study of harvesting ultrasonic energy and expands the underwater applicability of TENGs.