Intelligent shielding material based on VO2 with tunable near-field and far-field electromagnetic response

Intelligent electromagnetic interference (EMI) shielding materials, which can generate reversible and real-time EM responses to external stimuli, have an attractive prospect in smart wearable electronics. Herein, we design and fabricate flexible and intelligent vanadium dioxide (VO2)/cellulose nanofiber (CNF) shielding composites, showing a controllable EM response based on the reversible metal-to-insulator transition characteristic of VO2 by thermal stimuli. With the phase transition of VO2 between the insulating M phase and metallic R phase at-68 degrees C, the electrical conductivity of VO2/CNF composites is reversibly changed between-0.3 and-446.5 S/ m, leading to a tunable shielding effectiveness (SE) between-18.7 and-52.8 dB in the frequency of 8.2-12.4 GHz. The lattice strain of VO2 driven by thermal stimuli radically changes the EM parameters and impedance matching of VO2/CNF composites, which dominates the attenuation mechanism of EM waves. Uniquely, we demonstrate the VO2/CNF composites with a proof of concept to reversibly control the on and off of the wireless transmission. Moreover, the VO2/CNF composites exhibit an outstanding near-field shielding performance, which is potential to be applied in the electronic packaging field. This intelligent EMI shielding material has a broad prospect in the smart EM devices of next generation.