Multifunctional Ionic Liquid-Engineered Polyacrylamide/Cationic Guar Gum Hydrogels with Integrated Antifreezing and Antibacterial Properties for Advanced Wearable Sensors

Hydrogels are regarded as promising materials for flexible electronics and wearable sensors. However, it remains a significant challenge to simultaneously achieve high mechanical robustness, environmental tolerance, high electrical conductivity, antibacterial properties, self-healing ability, strong adhesion, and multimodal sensing performance in a single system. Addressing this, the multifunctional hydrogel (denoted as PCET) was developed by integrating polyacrylamide (PAM), biocompatible natural polymer cationic hydroxypropyl trimethylammonium guar gum (CGG), the ionic liquid 1-ethyl-3-methylimidazolium bromide ([Emim]Br), and natural polyphenol tannic acid (TA) through a synergistic cross-linking strategy. The PCET hydrogel demonstrated ionic conductivity (0.8 S/m) and functioned as a multimodal sensor, with strain sensitivity (GF = 1.65), reliable cycling stability, and responsive detection of pressure and temperature (TCR = 0.51%/°C). Furthermore, it exhibited strong substrate adhesion (∼50 kPa) and supported real-time motion monitoring, handwriting recognition, and electrocardiogram detection. [Emim]Br acted as a multifunctional agent that enhanced mechanical properties (toughness: 441 kJ·m–3, strength: 124 kPa, elongation: 840%) and conferred both antifreezing (freezing point: −28.65 °C) and antibacterial capabilities. Moreover, the chemical reaction between Fe3+ and TA can promote rapid gelation. This work underscored the versatile role of [Emim]Br and provided a viable strategy for the development of multistimulus-responsive wearable sensor devices based on hydrogels.