Dual-gradient cellulose nanofiber/MOFs/liquid metal/graphene nanoplatelet composite films for enhanced electromagnetic interference shielding, joule heating, and strain sensing

The rapid proliferation of wireless electronics has created an urgent demand for EMI shielding materials that are environmentally friendly, highly efficient, and multifunctional. However, synergistically achieving the aforementioned multiple performance attributes in practical applications remains a highly challenging task. Herein, we propose a dual-gradient asymmetric structured composite film composed of cellulose nanofiber (CNF), porous Zn/Co-ZIF (ZIF Zn/Co ) particles, liquid metal (LM), and graphene nanoplatelets (GNPs). The film features a three-layer architecture: a top CNF/ZIF Zn/Co absorption layer, a middle CNF/ZIF Zn/Co /LM transition layer, and a bottom CNF/ZIF Zn/Co /GNPs reflection layer. Benefiting from its unique dual-gradient asymmetric structure design, the optimized composite film with 50 wt% ZIF Zn/Co , 10 wt% LM, and 16 wt% GNPs achieved an impressive EMI SE of 47.42 dB at a thickness of 0.4 mm. Notably, the film maintained good structural integrity and stable EMI shielding effectiveness under various chemical and high/low-temperature environmental conditions. Beyond shielding performance, the material demonstrates remarkable Joule heating performance, achieving a saturation temperature of 76.4 °C under a low driving voltage of merely 5 V. Furthermore, the film demonstrates reliable strain sensing for real-time monitoring of various human motions, including finger bending and elbow flexion, with distinct and reproducible signal patterns. This study constructs an efficient and multifunctional EMI shielding material to meet the urgent demand for reliable shielding protection for electronic devices in complex environments.