Nanofiber yarn strain sensor with interpenetrating 3D MXene network via conjugated electrospinning and deep deposition

Driven by the growing demand for human-machine interaction and smart health monitoring, one-dimensional flexible strain sensors have attracted considerable interest due to their excellent flexibility and compatibility with textile integration. However, conventional sensors based on surface conductive coatings are often hindered by poor interfacial adhesion, inadequate environmental stability, and slow response dynamics. To address these challenges, this study proposes a “deep deposition” strategy to construct polyamide/polyvinyl alcohol (PA/PVA) nanofiber yarns (MPPY) featuring an internal three-dimensional interconnected conductive network via conjugated electrospinning. By precisely tuning the PA/PVA flow ratio, the yarn composition and porosity were tailored, while the intrinsic hydrophilicity of PVA facilitated full cross-sectional infiltration of MXene nanosheets. Subsequent twisting and plying further enhanced mechanical robustness and conductivity uniformity, yielding a three-ply yarn that was then incorporated into elastic fabrics via embroidery for customizable patterning. The resulting yarns exhibited an ultrafast response time (58 ± 2 ms at 10% strain) and demonstrated remarkable sensitivity across multiple strain regimes, with gauge factor values of 1.82 (0–50% strain), 9.71 (50–80% strain), and 22.93 (100% strain), while maintaining a coefficient (R 2 ) above 0.98 throughout. The yarn-integrated textile demonstrated outstanding durability, withstanding over 6000 stretching-releasing cycles at 50% strain, along with excellent washability, and resistance to corrosion in artificial sweat. By implementing patterned configurations (e.g., straight-line and serpentine-line), the fabric sensor facilitated real-time and precise monitoring of multi-joint human motions, including those of the neck, wrist, spine, and knee. This study provides a novel design pathway toward next-generation wearable electronic textiles with high reliability, fast response, and practical versatility.