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[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]

[Display omitted] • A novel strategy was proposed to achieve flexible liquid metal/cellulose nanofiber film. • The film exhibits excellent structural stability and EMI shielding effectiveness of ~ 65 dB. • Simulation in the frequency domain was introduced to investigate the shielding mechanism. Liquid metal (LM) is a promising candidate for electromagnetic interference (EMI) shielding due to the superb electrical conductivity and easy processing. However, poor compatibility caused by high surface tension, insulated oxide shells formed during processing, and unmanageable fluidity at elevated temperature of LM severely hinder its application in the field of EMI shielding. Herein, we develop a novel processing strategy integrating ball-milling dispersion, freeze-drying and compression molding to achieve free-standing and flexible LM/cellulose nanofiber composites (LM/CNF) film, in which the oxide shells of LM droplets generated by ball-milling are broken by mechanical compression, and LM droplets are coalesced while confined by CNF to construct a continuously conductive path. As a result, the robust LM/CNF film shows tensile strength of above 30 MPa, and it possesses electrical conductivity of 96,000 S/m, leading to remarkable shielding effectiveness (SE) of above 65 dB with a thickness of only 300 µm in a broad frequency range of 4–18 GHz covering C-band, X-band and Ku-band. Moreover, LM/CNF film exhibits excellent structural stability and EMI shielding performance reliability after high-temperature treatment. Besides, simulation in the frequency domain with ANSYS HFSS 2019 R2 is performed to intuitively understand the shielding mechanism of LM/CNF film. It is found that the attenuation of electromagnetic waves is mainly based on reflection. This study proposes a fresh scenario to achieve high-performance EMI shielding material and paves the way for potential applications of LM in portable and wearable smart electronics. [ABSTRACT FROM AUTHOR]