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

[Display omitted] • The intelligent VO 2 /cellulose nanofiber (VO 2 /CNF) composites were designed and fabricated successfully. • The lattice distortion across the phase transition of VO 2 induced by thermal stimuli changes EM parameters of composites. • The application of composites in control of the wireless transmission was demonstrated. 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 (VO 2)/cellulose nanofiber (CNF) shielding composites, showing a controllable EM response based on the reversible metal-to-insulator transition characteristic of VO 2 by thermal stimuli. With the phase transition of VO 2 between the insulating M phase and metallic R phase at ∼68 °C, the electrical conductivity of VO 2 /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 VO 2 driven by thermal stimuli radically changes the EM parameters and impedance matching of VO 2 /CNF composites, which dominates the attenuation mechanism of EM waves. Uniquely, we demonstrate the VO 2 /CNF composites with a proof of concept to reversibly control the on and off of the wireless transmission. Moreover, the VO 2 /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. [ABSTRACT FROM AUTHOR]