High-Strength Conductive Hydrogel Fiber Prepared Via Microfluidic Technology for Functionalized Strain Sensing.

The rapid advancement of wearable flexible electronics has heightened the demand for hydrogel materials that combine mechanical robustness with electrical conductivity. Herein, the TEMPO-oxidized cellulose nanofibers-Graphene nanosheets/poly(vinyl alcohol)-sodium alginate-tannic acid (TOCN-GN/PVA-SA-TA, TGG) composite hydrogel fibers are prepared by microfluidic spinning technology to solve the bottleneck problems of poor dispersion of GN and imbalance of mechanical-conductive properties of traditional hydrogels. TOCN, acting as a biotemplate, effectively inhibits GN agglomeration via hydrogen bonding and mechanical interlocking, thereby enhancing GN dispersion and facilitating the formation of 3D conductive networks within hydrogel fibers. The optimized TGG fibers achieved a tensile strength of 0.96 MPa, 150% elongation at break, and electrical conductivity of 2.66 S m^-1, while exhibiting enhanced energy dissipation and fatigue resistance. As strain sensors, TGG fibers demonstrated high sensitivity (gauge factor is 1.81 at 40-100% strain) and rapid response (≈0.3 s), enabling precise monitoring of joint movements, facial micro-expressions, and swallowing actions. Furthermore, PDMS-encapsulated textile sensors enabled encrypted Morse code transmission, demonstrating innovative potential for next-generation flexible electronics in health monitoring and human-machine interfaces.