Self-Healing Conductive Hydrogels Based on Collagen and Carboxymethyl Cellulose for Movement Monitoring

Conductive hydrogels have attracted significant attention in the fields of tissue engineering and flexible electronics. However, the development of conductive hydrogels whose polymeric matrix is composed of natural macromolecules without any synthetic polymer component remains challenging. Herein, self-healing conductive hydrogels composed of collagen (COL), oxidized carboxymethyl cellulose (OCMC), and MXene were fabricated. These hydrogels, formed via multiple dynamic bonds (imine bonds of COL and OCMC, borate ester bonds of OCMC and 1,4-phenyldiboric acid, and hydrogen bonds), exhibited excellent self-healing ability, injectability, and remoldability. Meanwhile, the dynamic covalent cross-linked network and the incorporation of MXene nanosheets effectively addressed the inherent shortcomings of pure collagen hydrogels. The storage modulus and loss modulus of the self-healing conductive hydrogels increased from 48.9 and 8.6 Pa to 3320.2 and 1075.5 Pa, respectively; additionally, the moduli still maintained the initial levels after three cycles of destruction and recovery. Moreover, the environmental stability of the hydrogels, including enzymatic resistance, swelling resistance, and thermal stability, was substantially improved and could be regulated by MXene concentration. Hemolysis and MTT assays revealed that the self-healing conductive hydrogels were biocompatible. Additionally, the hydrogel demonstrated high conductivity (2.04 S/m), fast response time (0.16 s), good stress sensitivity (0.30 kPa–1), remarkable fatigue resistance (>2000 cycles), and excellent electrical self-healing efficiency (98.7% ± 1.6% within 30 min). Consequently, it can be employed as a sensor to monitor human movements in real-time.