Marine-bioinspired interface: Ionically crosslinked alginate/MXene@Fe₃O₄/TPU composite film for EMI shielding, infrared stealth, and thermal management

MXene films have long been hindered by weak interfacial adhesion, environmental instability, and poor flexibility, compromising functionality. Inspired by robust marine organism interfaces, we propose a synergistic “interfacial adhesion–chemical barrier” strategy to construct a core–shell MXene-based composite film combining mechanical flexibility with interfacial stability. Electrospun Fe₃O₄/TPU nanofibers serve as the core for mechanical support and impedance matching. A polydopamine layer is in-situ deposited to create a high-affinity interface, followed by sodium alginate-assisted uniform coating of MXene nanosheets and Ca²⁺-mediated “egg-box” crosslinking, forming a robust shell anchoring MXene and imparting excellent interfacial stability. Optimizing SA content yields an optimal strength-toughness balance while maintaining high MXene integration, exhibiting resistance to friction and washing without performance degradation. The 71 µm thickness of MXene/SA@Fe3O4-TPU (MSFT) film delivers an average EMI shielding effectiveness of 46.9 dB (SSE 3577 dB·cm²·g⁻¹) over 5.8–18 GHz, along with efficient electrothermal and photothermal conversion. Ultralow infrared emissivity (ε = 0.22) synergizes with the low thermal conductivity of the core layer, enabling combined infrared stealth and passive thermal management. This strategy provides a facile and scalable route to multifunctional flexible MXene films for complex environments.