Tunable flexural waves by piezoelectric metasurface with shunt circuits

Elastic metasurfaces have been rapidly developed for effective modulation of elastic wave propagation. Among them, utilizing the electromechanical coupling effect of piezoelectric materials provides a promising way to design tunable and multifunctional elastic metasurfaces, but piezoelectric metasurfaces still face big challenges in theoretical guidance and experiments. In this paper, a tunable piezoelectric metasurface is proposed for achieving modulation of flexural wave in broad working frequency range. Based on the developed electromechanical coupling model, the piezoelectric patch with shunt resistor–inductor circuit is analyzed, and the functional unit of metasurface with only two piezoelectric patches is designed for modulating the flexural wave in thin plate. By using Antoniou’s circuit and considering the effect of impedance in circuit, the arbitral phase shift of functional unit is experimentally achieved by adjustable shunt circuits to verify the turnability in a full 2$\pi$ range. Further, the piezoelectric metasurface by assembling functional units can realize multiple functions, like tunable anomalous refraction and wave focusing, by adjusting shunt circuits.