A highly sensitive and stretchable double-layer conductive network structure CB/TPU/CB/MXene strain sensor for human–machine interaction

Abstract

Flexible sensors have emerged as a transformative technology in human-centered applications, enabling real-time physiological monitoring, human–machine interaction, and adaptive responses through their unique conformability, sensitivity, and multi-modal sensing capabilities. However, achieving both high sensitivity and a broad detection range remains a critical challenge in current flexible strain sensor research. This study introduces a carbon black/thermoplastic polyurethane/carbon black/MXene (CTCM) film sensor featuring a dual-network architecture. The electrospun carbon black/thermoplastic polyurethane (CT) composite acts as a structural scaffold and a primary conductive network, ensuring mechanical compliance. A secondary conductive network, composed of ultrasonically assembled MXene/carbon black nanoparticles, is chemically crosslinked with the CT matrix. This configuration establishes multiscale interfacial coupling that synergistically enhances charge transport and mechanical robustness. Through this hierarchical design—leveraging dual-network interactions and hydrogen bonding reinforcement—the sensor exhibits exceptional performance: a high maximum gauge factor (GF_max = 1765), a 0.1% strain detection limit, rapid response times (62 ms loading and 67 ms unloading), and excellent durability (>8000 cycles at 100% strain). Notably, the tensile strain capability of the composite significantly surpasses that of pure TPU, extending from 97.6% to 298.7%. This dual-network strategy establishes a new paradigm for next-generation wearable electronics, effectively overcoming the typical trade-off between detection breadth and sensitivity via controlled hierarchical charge transport pathways and tailored energy dissipation mechanisms.