Low-Frequency, High-Sensitivity Hydrophone Based on Ionic Polymer

Polymer materials have advantages over conventional materials in terms of flexibility and low-frequency response for acoustic-wave-receiving hydrophones. Herein, ionic polymer membrane with unique microstructures is designed and used for hydrophone application, and their piezoresistive and capacitive sensing properties are compared and investigated. The results demonstrate that the piezoresistive sensing properties mainly rely on the resistivity variation caused by the redistribution of ions, while the capacitive sensing properties are mainly due to the change in contact area between ionic polymer membrane and electrode. Furthermore, the effects of the microstructural parameters of the ionic polymer membranes on their response properties were investigated. The results indicate that microstructure with large base length, small interval, and moderate thickness shows higher response sensitivities, and micropyramids show better response sensitivity in contrast to that with microprismoids. In addition, the capacitive response also exhibits relative higher sensitivity and better stability than the piezoresistive response of ionic polymer membranes. Finally, an ionic polymer membrane with micropyramid array (base length $50~\mu $ m, interval $10~\mu $ m) is selected to design underwater hydrophones, and the ionic polymer membrane hydrophone prototype shows a high-sensitivity grade of $- 189.1~\pm ~2.0$ dB at low-frequency range of 20–150 Hz. This work provides a deep insight and opens up new possibilities for the design and developing of ionic polymer hydrophones and has potential applications for underwater detection and communication.