A bidirectional knitted strain sensor via AgNWs/MXene hybridization for broad-range multi-stage sensing

Abstract

Textile-based strain sensors are pivotal for next-generation wearable electronics, yet reconciling high sensitivity, broad strain tolerance, and bidirectional sensing remains a persistent challenge, rooted in the intrinsic sensitivity-range trade-off. Herein, we address this bottleneck by developing a bidirectional strain sensor via MXene/silver nanowire (AgNW) functionalization of 2 × 2 interlock knitted fabric, constructing a hierarchical conductive architecture through a facile sequential impregnation strategy. This tailored hierarchical network enables synergistic regulation of interfacial slippage and conductive pathway reconstruction, thereby yielding exceptional comprehensive electromechanical performance. The sensor exhibits a wide tensile strain range (0–100%) with tunable multi-stage gauge factors (GFs = 10.15–101.80), complemented by an ultra-low detection limit (0.033% strain) and rapid response/recovery times (288/384 ms). For compressive sensing, topological compaction of the fabric loops induces triple-regime sensitivity (S₁ = 0.065 kPa⁻¹ for <5 kPa; S₂ = 0.0157 kPa⁻¹ for 5–20 kPa; and S₃ = 0.0029 kPa⁻¹ for 20–100 kPa), alongside robust stability over 1000 consecutive loading–unloading cycles. Systematic experiments confirm that the bidirectional sensing capability originates from the synergistic effect between the reversible deformation of the 2 × 2 interlock fabric substrate and the responsive adjustment of the MXene–AgNWs conductive network. Validated by real-time physiological signal monitoring and extreme-strain durability tests (up to 250% tension), this sensor platform bridges the gap between broad-range detection and high sensitivity, holding great potential for advanced smart textiles and precision healthcare diagnostics.