Biomimicking natural wood to fabricate isotropically super-strong, tough, and transparent hydrogels for strain sensor and triboelectric nanogenerator applications

Abstract

Hydrogels with high strength and toughness exhibit promising prospects for a wide range of applications. However, the construction of isotropically strong and tough transparent hydrogels remains challenging. Herein, we describe an innovative and efficient wood-inspired biomimicking strategy integrating multiscale structures to synthesize isotropically strong, tough, conductive, and transparent hydrogels. Water-induced processes simultaneously achieved cellulose and lignin self-assembly into a cellulose skeleton and lignin nanoparticles, which synergistically functioned as enhanced phases to provide high strength and toughness. The resulting hydrogels exhibited interesting properties, such as excellent strength (4.6 MPa), high toughness (6.0 MJ m⁻³), good conductivity (8.2 mS cm⁻¹), and anti-freezing properties. Owing to these features, multiple applications such as strain sensors and self-powered triboelectric nanogenerators (TENGs) are demonstrated. This study explores the natural features of renewable resources to overcome the challenges of simultaneously achieving high strength, toughness, conductivity, and anisotropy, offering an effective strategy for creating isotropically functional hydrogels with high strength and toughness.