Self-adaptive acoustic cloak enabled by soft mechanical metamaterials

Abstract

Acoustic cloaks enable exciting object concealment by manipulating sound waves and have attracted research efforts from different approaches such as transformation acoustics. However, the challenge still lies in the practical implementation of those cloaks that require complex material designs. Here, we show that an underwater acoustic cloak can be automatically achieved by deforming a soft mechanical metamaterial with Poisson’s ratio of -1. The deformation of such an auxetic structure is demonstrated to be able to automatically and passively fulfill the requirement of quasi-conformal mapping for cloak design. Such a self-adaptive acoustic cloak exhibits a wide frequency and angular bandwidth, which opens an avenue for convenient design of various kinds of acoustic metamaterials.