A single-layered elastic metasurface for switching wide-angle asymmetric transmission of flexural waves

A limitation of present elastic metasurfaces remains in their modest flexibility to meet convertible functions on demand. Here, a feasible single-layered lossless metasurface is theoretically proposed and experimentally demonstrated for adjusting the asymmetric transmission of flexural waves. The easily reconstructed unit is derived from multiple pillared resonators; then, the number of units per period can be changed depending on the desired integer parity. In addition, the asymmetric transmission is physically realized by the uneven diffraction of the ±1st orders in opposite fields of the designed metasurface. Requiring neither active modules nor passively multilayer or loss-induced strategies, our design using only a layer of lossless metasurface allows the elastic-wave behavior to switch between efficient symmetric and asymmetric transmissions. Furthermore, a high contrast ratio of transmitted energy is verified in experiments and simulations within a wide-angle range. The present work is connected with the pragmatic applications of metasurfaces in timely directional vibration control and compactly elastodynamic rectifications.