Three-Dimensional Printing of High-Sensitivity Micro-Architected Piezoelectric Hydrophones with Designed Beam Patterns

Piezoelectric hydrophones are crucial for underwater applications such as communication and seafloor mapping. Limited by the brittleness of piezoelectric ceramics, conventional manufacturing methods restrict hydrophones’ shapes to simple geometries such as disks, cylinders, or spheres, which limits the sensitivity, directivity pattern, and working frequency bandwidth of the device.<br/>Here, we present a new class of high-performance 3D printed piezoelectric hydrophones consisting of rationally designed micro-architectures. Using a high-resolution light-based printing process, and thanks to a liquid sealing sintering process, the piezoelectric coefficients and electromagnetic coupling factor can reach respectively 92% and 85% of the pristine material’s values, the highest values among all existing 3D printing work.<br/>We have developed a framework to artificially manipulate the piezoelectric coefficients of an architected material by modifying the spatial arrangement of unit cell struts. This can be harnessed to develop a new class of metamaterial hydrophones whose sensitivity can be locally manipulated. We take advantage of this framework to generate hydrophones with sensitivities ~10 dB higher than the commercial ones, and whose directivity patterns can be inversely designed.<br/>This work holds great promises for high frequency sound localization without the need of hydrophone arrays, and for low frequency sound monitoring thanks to a hydrostatic figure of merit five times higher than the one of commercial transversely isotropic piezoelectric hydrophones.