Design and analysis of a flexible hydrophone based on PVDF with aluminum film substrate and PDMS encapsulation

Unmanned underwater vehicles (UUVs) need hydrophones for underwater acoustic sensing. However, previous hydrophones were rigid in shape and unable to realize conformal installation. In this paper, a flexible hydrophone with great installation adaptability was presented. Polyvinylidene fluoride (PVDF) piezoelectric film was applied as the transducing material. A flexible aluminum film was selected as the substrate. These two films were sandwiched by polydimethylsiloxane (PDMS) layers. Finite element simulation revealed that the sensitivity and bandwidth of the hydrophone were enhanced by using the aluminum film substrate. The sensing performance improvement was ascribed to the suppressed in-plane stress of the PVDF film. Prototypes were fabricated and tested. The fabricated hydrophone exhibited a sensitivity of −211 dB (ref. 1 V/μPa) at 500 Hz. It owned a 20–500 Hz working frequency range and an omnidirectional pattern. Besides, the sensitivity difference caused by shape changes was within 2.3 dB. Furthermore, the hydrophone showed good waterproofing ability.