Twist-Densified Collagen-Silver Nanowire Hydrogel Yarns for Conductive, Bioactive Sutures and Smart Textiles.

Tissue-interfaced bioelectronics require fibers that are conductive, strong, and bioactive, properties difficult to combine because conductive fillers that improve percolation tend to disrupt hydrogel networks and bioactivity. Twist densification was recently shown to convert collagen hydrogels into superhelical yarns with tendon-like mechanics. We extend this strategy to conductive composites by incorporating silver nanowires (AgNWs) into collagen hydrogels and co-assembling them into fibers. The completed gel network locks nanowires in place; subsequent twisting and cross-linking induce an approximately 60-fold volumetric densification and align collagen fibrils and AgNWs into a superhelical architecture. Incorporating the conductive phase before densification decouples electronic percolation from gel-network formation, allowing high conductivity (>24 S/mm) and preserved collagen bioactivity to coexist in a single yarn. A quantitative model attributes this conductivity to densification-driven volumetric percolation, alignment-enhanced longitudinal transport, and a mechanical route to junction de-insulation. Consistent with this model, sub-percolating yarns show a strain-induced decrease in resistance attributable to Poisson-contraction-driven junction compaction. The dense collagen matrix modulates Ag+ release, suppressing the cytotoxic burst release of bare nanowires while sustaining antibacterial activity. The yarns function as conductive surgical sutures in porcine tissue and as building blocks for woven smart textiles that integrate strain sensing with electrical stimulation.