321 / 2021-04-29 22:25:26

Functional-switchable Adaptive Elastic Metasurface with Stacked Piezoelectric Patches

Elastic metasurface;Negative capacitance;Phase shift;Tunable

Acoustic metamaterials and absorbing materials

A metasurface is a two-dimensional manmade structure that possesses salient wave manipulation features by controlling the wavefront arbitrarily. Based on the concept of generalized Snell’s law, a metasurface could achieve any desired local phase shift profile that covers the full 2π range. However, most conventional metasurfaces have fixed functionalities or working frequencies once fabricated. This hinders their applications in intelligent systems, as well as in application scenarios embedded in sharply changeable environment, which may cause their working frequency shift or even make them fail. To overcome this disadvantage, we propose a functional-switchable adaptive elastic metasurface composed of stacked piezoelectric patches to manipulate elastic longitudinal waves with high transmission performance. In this study, stacked piezoelectric patches with same dimensions are connected to shunted negative capacitance circuits in order to actualize switchable functions without modifying the structure of the metasurface. Through proper tuning of the negative capacitance in the shunting circuit, the effective stiffness of the metasurface units could be changed continuously, which enables the metasurface to produce local phase shift cover 0 to 2π range. Moreover, analytical model and numerical simulations are developed to obtain the corresponding negative capacitances. The proposed metasurfaces are simulated based on FEMs to illustrate their multiple functionalities, including anomalous refraction, wave focusing and nonparaxial propagation in broadband frequencies, which can be easily switched by tuning the negative capacitance.