Multi-functional thermal-mechanical anisotropic metasurface with shape memory alloy actuators

Metasurfaces are two-dimensional (2D) artificial electromagnetic (EM) materials comprising subwavelength periodic or non-periodic arrays of resonator elements. Multi-functional metasurfaces have shown magnificent potentials for many applications, including wireless communication, radar systems, and security. EM functions of metasurfaces can generally be switched or controlled by electrical or optical components, but these conventional tuning technologies suffer from complexity, high cost, and design limitations for large scales and function integration. Therefore, this paper proposes a novel thermal–mechanical anisotropic metasurface to provide multiple functionalities through mechanical transformation due to thermal stimulus on two shape memory alloy actuators, switching EM functionality between absorption and reflection. The absorptivity and reflectivity at 10.5 GHz are 96.5% and 81.33%, respectively. It consists of the motional metasurface and stational metasurface where mechanical transformation is achieved by the motional metasurface. In addition to the mechanical transformation, its function is switched depending on incident EM wave direction due to anisotropy that could achieved the transmission enhancement in ratio of 11.02 dB at operation frequency 5.9 GHz in opposing excitation. The proposed idea is numerically and experimentally demonstrated and discussed.