Thermally reconfigurable helical shape memory alloy-based metamaterial

Abstract

This paper presents our investigation and experimental validation of a thermally reconfigurable shape memory alloy (SMA)-based metamaterial with the offered degree of freedom of SMA mechanical features. The metamaterial unit cell consists of a two-way helical SMA acting as the resonator element and a cartridge heater for controlling the excitation temperature of the helical SMA. Experimental results of electrical control of the cartridge heater's excitation temperature show that as the temperature increases from room temperature (25 degrees C) to approximately 92 degrees C-corresponding to input DC voltages of 0 and 4 V, respectively-the metamaterial structure acts as a switchable absorber with an absorptivity of 97.2% and a reflector with a reflectivity of 89.4% at 7.13 GHz. Additionally, it deforms to its initial state as the temperature decreases to room temperature.