Shaping contactless forces through anomalous acoustic scattering

TL;DR

This paper demonstrates that subwavelength-structured acoustic metasurfaces can control contactless forces independently of object shape and size, enabling advanced manipulation like self-guidance and pulling.

Contribution

It introduces a novel approach using anomalous acoustic metasurface scattering to surpass traditional limits of wave-based contactless manipulation.

Findings

Achieved autonomous guidance of metasurface objects by acoustic waves.

Demonstrated contactless pulling of metasurface objects.

Showed control of forces independent of object shape and size.

Abstract

Waves impart momentum and exert force on obstacles in their path. The transfer of wave momentum is a fundamental mechanism for contactless manipulation, yet the rules of conventional scattering intrinsically limit the radiation force based on the shape and the size of the manipulated object. Here, we show that this intrinsic limit can be overcome for acoustic waves with subwavelength-structured metasurfaces, where the force becomes controllable by the arrangement of surface features, independent of the object's overall shape and size. Harnessing such anomalous metasurface scattering, we demonstrate complex actuation phenomena: self-guidance, where a metasurface object is autonomously guided by an acoustic wave, and contactless pulling, where a metasurface object is pulled by the wave. Our results show that bringing metasurface physics, and its full arsenal of tools, to the domain of mechanical manipulation opens the door to diverse actuation mechanisms that are beyond the limits of traditional wave-matter interactions.