Buckling-induced reconfigurability in underwater acoustic scatterers

Abstract

In this work, we explore switchable acoustic scattering from underwater particles via instability-induced internal pattern transformation in the 50 kHz-80 kHz frequency range. Our wavelength scale aqueous scatterer is designed based on modeling using the finite element method for a square lattice of air-filled voids within a shape memory polymer and is directly 3D printed. The structure undergoes a buckling transformation when subjected to an external deformation while simultaneously being heated. Through computational and experimental results, we demonstrate that the deformation state change leads to programmable acoustic transparency, or opacity, for the scattering particle. Underwater propagation experiments resolved in the near field illustrate that the switchable acoustic characteristics are frozen in the structure with rapid cooling after compression, and the initial acoustic state can be automatically recovered through reheating.