Sustainable and Tough MXene Hydrogel Based on Interlocked Structure for Multifunctional Sensing

Abstract

Traditional hydrogel sensors containing MXenes as a conductive substrate will inevitably face the problem of excessive stacking of MXene nanosheets, which limits electron transport, thus reducing conductivity and sensitivity. Moreover, existing MXene hydrogels generally exhibit poor mechanical properties and fragility. In addition, it is necessary to prepare degradable electronic skins for reducing environmental pollution and recycling energy materials─MXene. How to find a balance between mechanical properties and degradation properties is a challenge. In this work, we overcome this challenge by combining a dynamic covalent strategy and establishing a self-modified interlocked structure. A biodegradable physically cross-linked hydrogel (OMDDH─ordered MXene dynamic degradable hydrogel) is constructed, and a highly interconnected three-dimensional (3D) MXene@CS-Pba network is prepared, thus endowing the sensor with excellent conductivity (24 × 10–4 S cm–1). For excellent mechanical properties, dynamic covalent interactions, hydrogen-bonding interactions between the dual networks, and chain entanglement of poly(vinyl alcohol) (PVA) totally build interlocked structures, thus endowing the hydrogel with excellent mechanical strength (1000 kPa). In an acidic environment, the dynamic covalent bond is broken, and the chain entanglement of PVA is also disentangled due to the disruption of the electrostatic equilibrium, resulting in the release of MXene for recycling (recycling conductivity: 22 × 10–4 S cm–1). Undoubtedly, we exhibit a strategy to construct ordered and degradable MXene hydrogels possessing excellent conductivity, high mechanical strength, and degradation performance, which lays the sensors’ wide applications in smart devices.