An anti-freezing and strong wood-derived hydrogel for high-performance electronic skin and wearable sensing

Inspired by the highly aligned, well-ordered microstructure, and anisotropic mechanical properties of biological soft tissues, artificial electronic skins (e-skins) have been widely reported in recent years. However, challenges remain in achieving green, high mechanical properties, and multifunctionality simultaneously. In this work, we present a smart e-skin system with an anisotropic structure that couples a cellulose scaffold (CS) derived from natural wood with a polyvinyl alcohol (PVA)/MXene nanosheets (PM) network through a facile freeze-thawing process, featuring high toughness and excellent conductivity. With the addition of a biocompatible cryo-protectant, the smart e-skin exhibit ambient stability, anti-freezing properties, and moisturizing capability. The strong cross-linking and bonding between the 3D hierarchical CS and PM polymer network enhancing the mechanical strength of the e-skin in a specific direction, and the tensile strength along the longitudinal direction reached 12.01 MPa. The wood-derived hydrogel e-skin is 75 times and 23 times stronger than the isotropic cellulose hydrogel and pure PVA hydrogel. The soft PM polymer network endows the rigid cellulose skeleton with outstanding flexibility. Importantly, the e-skin with remarkable electromechanical sensing can realize the real-time monitoring of various human motions. In addition, the e-skin can also realize the private information transmission and even object recognition in aquatic environments. This study provides a facile strategy for developing next-generation wearable devices and multifunctional e-skin systems with bionic characteristics.