Porous Liquid Metal-Elastomer Composites with Strain-Enhanced Electromagnetic Interference Shielding

Abstract

The inherent metallic conductivity and superior fluidity of liquid metals (LMs) endow LM-elastomer composites with exceptional electrical conductivity and remarkable stretchability, thereby offering considerable advantages in the fabrication of flexible electromagnetic interference (EMI) shielding materials. Typically, the formation of LM networks within elastomer matrices is accomplished via the conventional sugar-templating technique; however, several limitations of this approach significantly restrict its practical application. In this study, we present an enhanced sugar-templating method that incorporates a mixed skeleton composed of gallium (Ga) powders and sugar powders, enabling precise modulation of LM concentration to fabricate porous LM-elastomer composites. This method yields highly stretchable elastomer composites embedded with liquid-metal droplets, which exhibit pronounced improvements in electromagnetic interference shielding effectiveness (EMI SE) upon mechanical stretching. The resulting porous LM-elastomer composites demonstrate a fracture strain of up to 470%, a density of 1.6 g/cm3, an electrical conductivity of 103 S/m, and an EMI SE of 23 dB. Notably, the average total shielding effectiveness (SET) of LMEF-20 increases monotonically from 14.88 dB at 0% strain to 29.98 dB at 100% strain, indicating its potential for EMI shielding applications involving large mechanical deformation. For comparison, elastomer composites containing discrete LM droplets were also prepared and evaluated for their EMI shielding performance. Collectively, this work offers valuable insights for advancing the development of stretchable electronics, soft robotics, and multifunctional materials featuring interpenetrating network architectures.