Ultra-strong and tough cellulose-based conductive hydrogels via orientation inspired by noodles pre-stretching.

Due to the unsatisfactory mechanical properties of natural polymer-based conductive hydrogels, their applications are limited. Shaanxi Biangbiang noodles can be toughened by applying external mechanical forces through stretching and beating movements; this process provides inspiration for the preparation of high-strength hydrogels. In this paper, we propose a strategy for the preparation of ultrastrong and ultratough conductive hydrogels by directional prestretching and solvent exchange. Neatly arranged fiber bundles containing many intermolecular hydrogen bonds and metal ion coordination bonds are successfully constructed inside the prepared hydrogels. The hydrogel has exceptional mechanical properties, with a fracture stress exceeding 50 MPa, fracture strain approaching 105 %, fracture toughness exceeding 30 MJ m, and high conductivity reaching 11.738 ± 0.06 mS m. Impressively, the hydrogel can maintain its high mechanical properties after being frozen at an ultralow temperature of -80 °C for 7 days. Compared with other tough hydrogels, natural tendons and synthetic rubbers, the hydrogel exhibits excellent mechanical properties. The cellulose-based conductive hydrogel prepared in this study can be applied to robotic soft tissues (such as the Achilles tendon) that require high strength and are operated in extreme environments.