Multi‐Responsive Hydrogels Based on Carboxylated Carbon Quantum Dots

Abstract Multi‐responsive hydrogels have been widely applied in the field of smart wearable sensors. Developing hydrogel‐based sensors with high sensitivity, sensing stability, stretchability, and multi‐responsiveness remains a key focus of current research. However, most existing studies still emphasize single‐responsive hydrogels, which exhibit significant performance limitations and result in restricted applications. In this study, carboxylated carbon quantum dots (CCQDs) with a small particle size (average 1.92 nm) are prepared. A composite conductive hydrogel (CMAD) is developed by combining CCQDs, hydroxyethyl cellulose (HEC), and calcium polyacrylate copolymer (PAM‐PAA‐Ca). The incorporation of CCQDs enhances the crosslinking density of the hydrogel, not only endowing the hydrogel with excellent self‐healing properties but also significantly enhancing its mechanical performance (stress: 363.1 kPa; strain: 658.1%). Moreover, the CMADs‐x hydrogel exhibits outstanding fluorescence characteristics and strain sensitivity (GF 1 = 1.59; GF 2 = 2.48; GF 3 = 0.505), with short response and recovery times (0.3s), along with multi‐responsive capabilities to light, stress, and pH, making it suitable for use as a multi‐responsive hydrogel sensor. This work provides new insights into the design and mechanisms of next‐generation hydrogel‐based smart wearable sensors.