A Stretchable Sandwich Composite Film With Ultra‐Broadband Electromagnetic Interference Shielding and High‐Performance Photothermal Conversion Capability

ABSTRACT With the rapid growth demand for advanced integrated electronic systems, lightweight flexible electromagnetic interference (EMI) shielding films integrated with functional properties, such as excellent mechanical properties and self‐healing capability, are a research focus in high‐tech functional materials. Herein, a sandwich‐structured aramid nanofibers/silver nanoparticles/waterborne polyurethane (ANF/AgNPs/WPU, AAgW) composite film is fabricated using microwave synthesis combined with spin‐coating. AAgW composite film exhibits excellent stretchability, exceptional EMI shielding effectiveness (SE) in the frequency range of 6.0–60.0 GHz, and efficient photothermal conversion. AAgW film exhibits outstanding mechanical properties with a fracture strain of 406.4%. Notably, EMI SE of 40 dB is achieved in an ultra‐wide frequency range of 6.0–60.0 GHz when the thickness of AAgW composite film is only 26.0 μm. After 100 stretching cycles at 35% strain, the average SE in the X‐band remains at 19.6 dB. In addition, the AAgW film possesses an active heating ability through photothermal conversion, and its surface saturation temperature can reach 71°C under a one‐sun illumination. The integration of the “shielding‐heating” function provides a brand‐new solution for simultaneously achieving stretchable ultra‐wideband EMI shielding and photothermal conversion. This work shows great promise for applications in advanced wearable devices and high‐frequency communication terminals.