Mechanically Robust and Flexible Polyurethane /Liquid Metal Film with 5000-Bend Stability for Electromagnetic Interference Shielding

Abstract

Gallium-based liquid metal has attracted considerable interest for flexible electromagnetic interference shielding owing to its high electrical conductivity and intrinsic deformability. Herein, flexible polyurethane/liquid metal/polyurethane composite films were fabricated through a combination of electrospinning and electrospraying, in which eutectic gallium-indium particles were confined between two thermoplastic polyurethane nanofibrous layers to construct a leak-resistant sandwich architecture. The porous fibrous framework effectively immobilized liquid metal particles and promoted the formation of interconnected conductive pathways after mechanical activation. The interconnected liquid metals network endowed the PL5P composite film with shielding effectiveness above 20 dB across the 4−18 GHz frequency range at an ultrathin thickness of only 0.18 mm. Quantitative electromagnetic analyses revealed pronounced impedance mismatch and strong dielectric attenuation, indicating that substantial initial reflection was accompanied by efficient dissipation of the electromagnetic waves entering the film. Moreover, the composite films retained stable shielding performance after 5000 bending cycles and water immersion, while maintaining an elongation at break exceeding 350%. This work provides a simple and scalable strategy for engineering leak-resistant liquid-metal architectures into ultrathin, flexible, and durable electromagnetic interference shielding materials.