Retroreflection of flexural wave by using elastic metasurface

The metasurface is widely used in wave manipulation because it has an excellent capability of phase modulation in a simple way. In this work, we propose an elastic metasurface that can achieve retroreflection of a flexural wave on a thin metal plate. The elastic metasurface is composed of only two subunits with a simplified design. By carefully selecting the thickness and material of the subunits, the phase of flexural wave is re-modulated, and retroreflection is achieved at different incident angles. Furthermore, a single-phase metasurface and a two-component metasurface with fixed constraints and free boundaries, respectively, are studied. The results show that this type of elastic metasurface conveniently steers reflection of the flexural wave, and it may have potential applications in vibration control, energy harvesting, and piezoelectric sensors.