Routing Acoustic Waves via a Metamaterial with Extreme Anisotropy

Routing acoustic waves without backscattering losses is presently of great interest. Unlike both conventional approaches using defects in sonic crystals and emerging approaches based on topological edge states, this study proposes a radically different theoretical framework that utilizes extremely anisotropic media to engineer backscattering-immune waveguides. The exact condition for one-way wave propagation along zigzag paths is derived. The proposal is experimentally validated using spoof surface acoustic waves, and the results could have implications for on-chip wave manipulation, as well as noise control.