3D Knitted Fabric Composite Architecture for Ultra-Stretchable Electrical Conductors with Superior Conductive Stability During Large Deformations.

This work proposes an innovative design strategy for ultra-stretchable conductors leveraging additive-manufactured knitting technology. By exploring the fundamental relationships between loop-scale structural features and knit-scale mechanical properties, both numerical simulations and experimental studies are carried out to investigate how topological loop-patterns govern the deformation mechanisms of 3D-knitted fabric architectures. Upon comparing the structural characteristics and mechanical properties of various knitted patterns, the rib-knits featuring a distinctive bilayer configuration show a particular elastic deformation process spanning three distinct stages, including structure unfolding, geometric extension, and material stretching. Based on this understanding, 2 + 2 rib-knitted fabric architecture for a stretchable conductor is constructed, in which conductive EGaIn liquid-metals are coated onto polytetrafluoroethylene (PTFE) fibers with polymethacrylate (PMA) serving as the intermediate adhesive. The resultant EGaIn@PMA/PTFE fabric (EP2F) architecture demonstrates remarkable conductivity (≈5.02 × 103 S cm-1) and stability, even after stretching up to 750% strain (≈4.76 × 103 S cm-1, conductivity variation less than 5%), along with high mechanical strength, as evidenced by a fracture stretching stress exceeding 400 MPa. The mechanical performances of the as-fabricated EP2F architecture can be further tailored across optimized knit patterns and fiber materials. This work would provide a productive and systematic strategy for designing stretchable conductors with practical applications in advanced wearable electronics.