Hierarchical flexible WPU/Ni/Wood composites with bump structure for electromagnetic interference shielding and Joule heating

Driven by the increasingly urgent demand for flexible, lightweight, and multifunctional electromagnetic interference shielding materials, this study used natural Balsa wood as the substrate, constructed a conductive-magnetic network by electroless nickel plating on the wood surface, and combined it with a waterborne polyurethane (WPU), polyethylene glycol (PEG) and silane coupling agent (KH550) composite flexible structure to successfully prepare the high-performance flexible nickel-coated multilayer wood-based composite F-BWN. The optimal sample (0.39 mm thick, 20 min nickel deposition, 20 MPa cold pressing for 15 min) exhibited a conductivity of 45.7 S·cm⁻¹ , a tensile strength of 87.3 MPa, an average electromagnetic shielding effectiveness of 61.85 dB in the 8.2–12.4 GHz band, and a surface temperature of 163.7 °C at 1.75 V. The composite material exhibited excellent Joule heating performance and adjustable infrared stealth ability. Notably, unlike previously reported wood-based EMI shields that were either rigid or lacked multifunctional integration, our F-BWN uniquely combined high flexibility, strong mechanical strength, outstanding shielding effectiveness, and excellent Joule heating performance in a single material. The nickel-plated wood surface, combined with the flexible WPU/PEG/KH550 matrix, formed a layered conductive-magnetic configuration. The highly conductive nickel network on the wood surface strongly reflected most incident electromagnetic waves, while the magnetic hysteresis behavior and the presence of Ni further attenuated the residual wave energy that penetrated into the material. The material also exhibited good flexibility, environmental durability, and cyclic stability. The material also exhibited good flexibility, environmental durability, and cyclic stability. This work provided a sustainable strategy for developing high-performance flexible electromagnetic shielding materials and promoted the high-value application of biomass materials in flexible electronics and intelligent protection.