Copper-coated yarn architectures for knitted fabrics with enhanced strain sensitivity and wrist posture recognition

Abstract

Knitted flexible sensors, owing to their looped architecture, exhibit excellent stretchability, comfort, and responsiveness, enabling real-time monitoring of biomechanical motion. Here, we systematically investigated the electromechanical performance of conductive fabrics composed of stainless steel, silver-plated, and copper-plated yarns across rib, half-air layer, and air-layer knitting structures. Among them, copper-plated rib fabrics with (35r × 35r)/5 cm density demonstrated superior sensing performance, with stable resistance variation (∼2 to ∼1 kΩ from 0° to 90° wrist bending), high linearity (R²= 0.959), good stability (δ = 0.232 after 100 cycles), and a gauge factor (GF) of ∼2.73. An equivalent resistance model was established to elucidate the impact of loop geometry on sensor performance, confirming that higher coursewise density lowers resistance and enhances sensitivity. A wearable knitted wristband sensor was fabricated that accurately distinguishes wrist postures. These findings highlight the potential of structured conductive knits as customizable, high-performance platforms for next-generation wearable health monitoring and rehabilitation systems.