Bioinspired MXene-based nanocomposite fibers

Two-dimensional transition metal carbides/nitrides (MXenes), integrating high mechanical strength and excellent electrical conductivity, photothermal conversion, and electrochemical energy storage, are an ideal building block for constructing high-performance fibers, which have promising applications in flexible electronics, aerospace, and energy storage devices, and among many others. Various methods have been developed to assemble MXene nanosheets into macroscopic fibers by wet-spinning, coating, electrospinning, and biscrolling. However, the weak interfacial interactions, misalignment, and void defects during the assembly usually degrade the properties of the resultant MXene fibers, limiting their practical applications. Natural nacre shows extraordinary mechanical properties because of the aligned and compact structure with the abundant interfacial interactions between aragonite platelets and organic matrix, which provides inspiration for assembling MXene nanosheets into high-performance macroscopic fibers. In this review, the intrinsic mechanical, electrical, and thermal properties of MXene nanosheets are firstly introduced, followed by analyzing the relationship between the structure and mechanical properties of natural nacre. The recent research progress of bioinspired MXene-based nanocomposite fibers (BMNFs) is then reviewed, highlighting how to rationally design the interfacial interactions between adjacent MXene nanosheets, improve the alignment of MXene nanosheets, and remove the void defects in BMNFs. Next, the applications of BMNFs in electrical wires, electromagnetic interference shielding, Joule heating, photothermal conversion, thermoelectric and triboelectric generators, sensors, supercapacitors, and artificial muscles are discussed. Finally, the existing challenges in the field of BMNFs are summarized and a perspective on the future roadmap for BMNFs to promote their practical applications is proposed.