Sustainable construction of lignin-containing cellulose nanofibrils reinforced antifreeze deep eutectic solvent gel for wearable human motion strain sensors

Gel is one of the most promising flexible sensing materials for wearable devices, health monitoring, and electronic skin. However, their inherent brittleness, low-temperature freezing, and poor mechanical properties have greatly hindered their practical applications. In this study, a series of lignin-containing cellulose nanofibrils (LCNFs) reinforced deep eutectic solvent (DES) gels were successfully prepared. The effects of LCNFs concentration, CaCl 2 dosage and solvent exchange time on the conductivity, antifreeze and mechanical properties of the DES gels were systematically investigated. Results demonstrated that the optimized DES gel (Ca 18 L 0.75 PAM-3h) exhibited outstanding mechanical properties (0.75 MPa stress, 1593% strain), high conductivity (2.29 S/m), and excellent antifreeze properties (−80 °C) due to the multiple molecular interactions among polyacrylamide (PAM) chains, LCNFs, Ca 2+ , and DES. Additionally, the DES recovered during LCNFs preparation was reused for gel fabrication, thereby enhancing resource efficiency and minimizing waste generation. When used as a strain sensor for real-time human motion monitoring, the DES gel showed excellent sensitivity (GF = 13.66) and stability. This work provided a feasible pathway for developing high-performance DES gels based on the synergistic effects of LCNFs and DES, and which showed great potential for applications in flexible sensing.