Abstract: Conformal electromagnetic interference (EMI) shielding films present considerable promise for addressing electromagnetic compatibility challenges in thin and lightweight electronic devices, owing to their superior electrical conductivity, mechanical robustness, and effective EMI shielding performance. However, harmonizing electrical conductivity with mechanical properties under strain remains a significant challenge. Herein, a novel stretchable EMI shielding composite film based on thermoplastic polyurethane (TPU) is reported, featuring adaptive conductive networks through the construction of trilayer solid-liquid-solid structures incorporating liquid metal (LM) and silver (Ag) flakes. The intermediate LM layer establishes a continuous and strain-adaptive conductive network during stretching, ensuring long-range electrical stability, while the outer Ag layers facilitate vertical electrical interconnections with LM and prevent LM leakage from the polymer matrix under high strain. Remarkably, the Ag/LM/TPU composite film retains EMI shielding effectiveness (SE) of over 83 % even at 200 % of strain. Furthermore, the composite film exhibits excellent conformal EMI shielding capabilities on printed circuit board assemblies (PCBA), with near-field SE exceeding 62 dB across the 0.5-6 GHz. This work offers a novel design paradigm for fabricating stretchable conductive composites with adaptive conductive networks and sustained electrical stability, concurrently advancing a viable strategy for conformal EMI shielding technology for next-generation miniaturized electronics.

Key words: Conformal electromagnetic interference shielding, Liquid metal, Adaptive conductive network, Electronic packaging