Flexible and Multifunctional Papers with Nacre-Mimetic MXene/Chitosan Nanostructures for Joule/Solar Heating and Motion Monitoring

Paper, traditionally a two-dimensional assembly of randomly distributed cellulose fibers with a rough and porous surface, provides an ideal substrate for loading nanostructured materials. Integrating multifunctionality into papers offers exciting opportunities for flexible electronic materials, which are promising for wearable and portable device applications. Herein, a simple layer-by-layer (LBL) spray coating method was employed to alternatively deposit MXene and chitosan (CS) layers on paper substrate for producing flexible and multifunctional papers. The CS chain played a pivotal role as “bridge”, linking Ti 3 C 2 T x MXene and ensuring the strict arrangement of hard MXene nanosheets with the intercalation of soft CS layers to construct a typical brick-and-mortar structure, a result of the electrostatic adsorption and strong hydrogen bonding interactions between these components. The electrically conductive nature of MXene coupled with this highly ordered structure endowed the nacre-mimetic-coated paper (MCP) with a high electrical conductivity of 1.09 S cm –1, positioning it as an efficient heater capable of reachinga saturated temperature of 120 °C at 9 V driving voltage and 70 °C under a solar irradiation of 3.0 W/cm 2 . Additionally, the MCP served as a flexible sensor to accurately monitor both large- and small-scale human motions in real time. This work offers profound insights into the fabrication and functions of paper-based flexible electronic materials, and paper-based composites may become the next generation of functional materials used in electronic device fields.