Bio-Based Self-Healing Polyurethane with Dynamic Networks and MXene/AgNWs Synergy for Dual-Mode Pressure and Humidity Sensing

The development of sustainable dual-mode flexible sensors with self-healing ability, reprocessability, and multifunctionality holds promise for the future wearable technology. Herein, a bio-based waterborne polyurethane (BSWPU) was synthesized from a vanillin-derived polyol and castor oil, using butanedione dioxime (DMG) as a chain extender. The incorporation of dynamic Schiff base and oxime-carbamate bonds endowed BSWPU with high mechanical properties (tensile strength: 8.6 MPa, elongation at break: 242.5%), high healing efficiency (94%), thermal remoldability, and chemical degradability under alkaline conditions, supporting its suitability as a substrate for flexible sensors. Furthermore, an MXene/AgNWs conductive network was integrated onto the BSWPU substrate to fabricate a dual-mode pressure-humidity sensor. With 20 wt % MXene, the sensor exhibited a pressure sensitivity of 43.29 kPa–1 and a humidity-induced resistance change of 37.8%. The sensor was able to detect stimuli ranging from large-scale joint movements to subtle facial expressions and to distinguish humidity variations associated with different breathing patterns and motion states. It also enabled encoded signal transmission via Morse code. In addition, the sensor showed thermally assisted self-healing and alkali-triggered chemical degradability. Overall, this work offers a feasible strategy for constructing more sustainable self-healing dual-mode flexible sensors for wearable electronics.