PAN/PI-Derived Carbon Nanofibrous Membranes with MXene-Assisted Contact Modulation for Heat-Resistant Piezoresistive Sensing and Thermal Warning Response

Flexible piezoresistive sensors for protective textiles should maintain pressure-responsive conductivity after thermal exposure, whereas many polymer-based sensing layers soften, degrade, or lose signal output under heat. Herein, we report a self-supporting PAN/PI-derived carbon nanofibrous membrane with MXene-assisted contact modulation for heat-resistant piezoresistive sensing and temperature-triggered warning. Electrospun PAN/PAA membranes were stabilized and carbonized to construct a thermally durable conductive fibrous framework, in which PAN serves as the principal carbon-forming precursor and the PAA-derived PI intermediate assists structural retention during thermal conversion. Surface-deposited Ti3C2Tx MXene nanosheets further introduce conductive junctions and pressure-responsive contact interfaces. The optimized PPNF-MX3 sensor exhibits a broad pressure range of 0.05–250 kPa, a low-pressure sensitivity of 8.16 kPa–1, and response/recovery times of 520/572 ms. It retains 97.51% of its electromechanical response after 10,000 bending-release cycles at room temperature and 83.16% after 1200 cycles following thermal exposure at 350 °C for 660 s. The carbonized membrane exhibits thermal-shielding behavior and flame-induced structural retention, while the integrated system enables repeatable temperature-triggered warning at 495 °C. These results demonstrate the potential of PPNF-MX3 as a multifunctional sensing and thermal-warning platform for intelligent protective textiles exposed to demanding thermal environments.