Efficient Fabrication of Highly Elastic, Self-Adhesive MXene-Doped Lignin-Based Conductive Hydrogels for Flexible Strain Sensing Applications

Conductive hydrogels are used in a wide variety of applications, including human motion detection, conversion, and storage of energy and self-powered wearable devices. However, their poor mechanical properties or poor adhesion to various materials has seriously hindered their prospects in the direction of flexible wearable electronic devices. Herein, alkali lignin was sulfonated to disperse silica nanoparticles (LSNs) as a mechanical reinforcing agent. Subsequently, the sulfonated lignin can form a self-catalytic system (LSNs–Fe3+) with iron ions to efficiently prepare conductive hydrogels at room temperature. This preparation strategy of “one-stone-two-birds” endows the hydrogel with excellent high elasticity and self-adhesiveness. In addition, the doping of MXene endows the hydrogel with a superior conductivity. Specifically, the prepared hydrogels containing 1.5 wt % LSNs have excellent tensile properties (∼700% elongation and ∼76.0 kPa tensile strength) and nice adhesion properties (∼19.9 kPa self-adhesion). In addition, the assembled hydrogel sensor has a high sensitivity and cyclic stability and can monitor human movement in real time. In conclusion, the conductive hydrogel designed in this study was expected to be an excellent candidate for flexible, wearable electronics.