Phase Transition driven Electromechanically Reconfigurable 3D THz Metadevice

Terahertz (THz) electromagnetic radiation has numerous promising applications including 6G wireless communication, fingerprint chemical sensing, security screening, and centimeter-level object localization. However, the lack of efficient devices to generate, manipulate, and detect THz waves has remained a key technological challenge. Electrically reconfigurable metasurfaces with 3D resonators would allow for new paradigms of light-matter interaction inaccessible through their 2D counterparts. In this work, we demonstrate a robust platform to realize THz metadevices with colossal structural reconfiguration between planar and 3D geometries powered by the phase transition in VO₂. We combine two counteracting driving forces for the actuation of the resonators – (i) inhomogeneous stress-induced folding, which is non-volatile, and (ii) strain associated with the insulator-to-metal transition in VO₂, which is volatile. This massive structural reconfiguration allows for advanced THz manipulation capabilities, while the electrical stimulus ensures high compactness and integrability. THz metadevices with 3D reconfigurable split ring resonators have been fabricated and characterized to illustrate the proposed platform. Beyond the functionalities enabled by the massive structural reconfiguration of THz resonators, the unique material properties of VO₂ such as the hysteretic nature of the phase transition of VO₂, is also harnessed to demonstrate multi-state memory effect using transient sub-threshold current stimulus. Hence, these novel VO₂ MEMS metasurfaces are functionally versatile, spectrally scalable, and electrically controlled and hence are highly attractive for the realization of 6G communication devices such as reconfigurable intelligent systems, holographic beam formers, and spatial light modulators.