High-Performance Flexible Strain Sensors: The Role of In-Situ Cross-Linking and Interface Engineering in Liquid Metal–Carbon Nanotube-PDMS Composites

Abstract

The increasing demand for high-performance strain sensors has driven the development of innovative composite systems. This study focused on enhancing the performance of composites by integrating liquid metal, carbon nanotubes, and polydimethylsiloxane (PDMS) in an innovative approach that involved advanced interface engineering, filler synergy, and in situ cross-linking of PDMS in solution. Surface modification of liquid metal with allyl disulfide and hydrogen-containing polydimethylsiloxane significantly improved its stability and dispersion within the polymer matrix. Through in situ cross-linking in solution and subsequent segment rearrangement after solvent evaporation, a continuous filler network was formed within the composite. The composites exhibited enhanced thermal stability, achieving a thermal conductivity of up to 2.13 W/(m•K) while simultaneously attaining a high electrical conductivity of 416 S/cm. The composite demonstrated excellent thermal management capabilities, alongside remarkable mechanical properties, including over 400% elongation at break and a low modulus of 0.587 MPa, even at high filler content. These attributes make the composite highly suitable for flexible strain sensor applications. Notably, the composite demonstrated outstanding strain sensing capabilities, effectively monitoring both human motion and handwriting. This work highlighted the critical roles of interface modification, filler interactions, and in situ cross-linking in achieving significant improvements in thermal, electrical, and sensing performance, thereby advancing the potential applications of flexible electronic materials.