A strong, stretchable, adhesive, conductive, transparent cellulose-based hydrogel for wearable strain sensors and arrays

Conductive hydrogels have received extensive attention in flexible electronics due to their diverse characteristics. However, the multifunctional incompatibility between conductive fillers and hydrogel matrices remains challenging. In this paper, a simple and low-cost strategy is adopted to introduce nanocellulose and 2-acrylamide-2-methylpropane sulfonic acid into the polyacrylamide network, and a strong, tough, adhesive, and transparent double-network hydrogel is successfully prepared by a one-step method. The introduction of nanocellulose effectively forms a large number of hydrogen bonds, which significantly improves the mechanical properties of the hydrogel. The prepared hydrogel not only has excellent mechanical properties, such as stretchability, fatigue resistance, a high tensile strength of 0.8 MPa, and a high strain of 1200%, but also has excellent adhesion, conductivity (5.91 S m-1), and high transparency (85% at 550 nm). The flexible strain sensor assembled using the prepared hydrogel can be used to detect human motion, including subtle and large movements, showing excellent sensitivity and stability.