Highly Stretchable Liquid-Metal/Elastomeric Foam Based on a Slidable Double Network for Absorption-Dominated Electromagnetic Interference Shielding

An ideal electromagnetic interference (EMI) shielding material possessing lightweight, high EMI shielding efficiency (EMI SE > 60 dB), low reflectivity (R < 0.5 or SER < 3 dB), and excellent stretchability (strain >200%) with a stable EMI SE is remarkably desirable but challenging to design for avoiding electromagnetic pollution caused by the rapid development of electronic devices. Here, an elastomeric foam (SDEP/LM) with a slidable double-network structure covered with a thin layer of liquid metal is developed, achieving a porosity of 67% and a low density of 1.1 ± 0.1 g/cm3, a fracture strain of 1400%, a super high tearing energy of 31.6 kJ/m2, and a high absorption-dominated EMI shielding performance (SE of 66 dB with a thickness of 2 mm). The absorption efficiency (Aeff) for all samples exceeded 99.99%. This unique absorption-dominated EMI shielding ability is completely different from the reflection-dominated EMI shielding behavior of conventional liquid-metal-based materials and is attributed to the porous structure and elasticity of the polymer matrix. Furthermore, the EMI shielding performance is stable when stretched.