Development of a Nano-toughened multifunctional composite hydrogel based on chitosan and its applications in catalytic and flexible sensors.

In this study, we developed a novel composite catalytic hydrogel, which integrates excellent mechanical properties, catalytic activity, and sensing performance. Discarded hydrogel sensors are reused as templates for in-situ generation of metal nanoparticles, and multifunctional hydrogels combining sensing and catalysis are realized. Polyacrylamide (PAM) provides a three-dimensional network structure, while octadecyl methacrylate (SMA) acts as a hydrophobic association center, enhancing the structural stability of the hydrogel. Dopamine coated with silica (PDA@SiO₂) nanoparticles act as nanoreinforcement points, further improving the mechanical strength of the hydrogel. Graphene(GN) imparts the hydrogel with good electrical conductivity and sensing capabilities. The hydrogel exhibits a strain of 1878 %, a tensile strength of 668 kPa, and toughness of 5615.2 kJ/m, while also demonstrating excellent sensing performance, with gauge factor (GF) of 7.49 and response time of 168 ms, enabling a quick response to external strain. It effectively detects human motions, such as finger bending and joint movement. Additionally, PDA@SiO₂ acts as an active site for the synthesis of Ag NPs, facilitating the reduction of Rhodamine B at 25 °C with a catalytic rate constant of 0.504 min. After five catalytic cycles, the hydrogel retains over 99 % efficiency, demonstrating excellent cyclic stability and recyclability.