The holographic algorithm and design for propagation of flexural Lamb waves and particles manipulation using elastic metasurfaces

Abstract

Controlling propagation of flexural waves is fundamental for energy and information transportation. In recent years, the acoustic holographic method has been developed in air and water for controlling arbitrary wavefronts. Nevertheless, it has not been applied to flexural Lamb waves. Considering the similar form of wave equation, here we develop the Weighted Gerchberg–Saxton(GSW) holographic algorithm for propagation of flexural Lamb waves. The labyrinth-type metasurfaces are used to modulate the amplitudes and phases by the holographic algorithm. Different kinds of wavefronts for the flexural Lamb waves, such as acoustic focusing, are achieved both numerically and experimentally, which can match well with each other. The holographic algorithm for the multi-frequency range is further developed, which is suitable for tuning the flexural Lamb waves. Additionally, we realize the acoustic cloaking by the holographic flexural waves bottle. The flexural waves can be designed to circumvent the obstacle. Finally, the particles are trapped to the nodal lines, which is utilized for visualizing the flexural waves. The splitting of particles pile is further realized by the focusing of flexural waves. This work paves the way for controlling propagation of flexural Lamb waves, thereby opening up the realm of energy transportation, acoustic cloaking, and nondestructive testing.