High conductive, mechanical properties and temperature-sensitive alginate-based hydrogel enhanced with tunicate cellulose nanocrystals for wearable flexible sensors.

Conductive hydrogels (CHs) have garnered significant interest as promising candidates for flexible wearable electronics, offering alternatives to conventional rigid metal-based sensors. However, existing CHs often suffer from compromised mechanical integrity, limited conductivity, inadequate thermoresponsiveness, and functional singularity. Herein, a multifunctional hydrogel with exceptional conductivity, mechanical robustness, and temperature sensitivity was engineered via free-radical polymerization of N-isopropylacrylamide (NIPAM) within a sodium alginate (SA) matrix reinforced with tunicate cellulose nanocrystals (TCNCs), followed by ionic crosslinking in calcium chloride (CaCl₂) solution. The resultant hydrogel demonstrated remarkable mechanical properties (tensile strength: 152.4 kPa, elongation at break: 626.9 %), high conductivity (13.9 S/m), strain-sensitive behavior (gauge factor [GF] = 0.96 for 50-100 % strain, GF = 1.56 for 100-200 %, GF = 2.50 for 200-300 %), and pronounced thermoresponsiveness (temperature coefficient of resistance [TCR] = -7.0643 %/°C for 25-30 °C, TCR = 3.7569 %/°C for 30-40 °C, TCR = 1.3776 %/°C for 40-50 °C). These attributes stem from synergistic physical-chemical crosslinking networks, enabling real-time monitoring of human motion and temperature fluctuations. This work advances the design of high-performance CHs for next-generation wearable sensing technologies.