Routing Acoustic Waves via a Metamaterial with Extreme Anisotropy

Routing and guiding acoustic waves around sharp corners without backscattering losses is of great interest in the acoustics community. Sonic crystals are primarily utilized to design backscattering-immune waveguides. While conventional approaches use defects to guide waves, a considerably more sophisticated and robust approach was recently developed based on topological edge states. Here, we propose a radically different theoretical framework based on extremely anisotropic media for engineering backscattering-immune waveguides. We theoretically derive the exact condition for one-way wave propagation in zigzag paths. While the theoretical underpinning is universal and applicable to acoustic and electromagnetic waves, the experimental validation is conducted using spoof surface acoustic waves. The proposed metamaterial opens up possibilities for wave manipulation and leads to applications in on-chip devices and noise control.