Shear-flow-induced assembly of 2D nanosheets for the fabrication of composite films with high tensile strength.

High-performance bioinspired composite materials require the precise alignment of synthetic nanosheets to mimic the mechanical properties of highly ordered laminated microstructures found in nature. Here, we detail a nanosheet superspreading alignment strategy for fabricating nanocomposite films that uses shear-flow forces at the interface between two immiscible phases to induce long-range, high-order alignment of the 2D nanosheets that enhances the films' mechanical properties. In situ interface crystallization or cross-linking follows the alignment and effectively locks the oriented configuration (the resulting orientation order parameter is >0.85). Subsequent solvent dewetting enables continuous film formation over large areas while maintaining well-defined microstructural integrity. This process overcomes the misorientation and aggregation typical of conventional alignment methods and can be scaled using a multi-nozzle extrusion setup compatible with commercial heating and film-collection components. The step-by-step procedures cover the nanosheet precursor preparation, the continuous-film fabrication and their microstructural characterization and require ≤23 days to complete. The procedures are applicable to a broad range of nanosheet materials, including graphene oxide, MXenes, transition-metal dichalcogenides and layered clays, and the resulting composite films exhibit enhanced mechanical strength, toughness and multifunctionality. Nanocomposites based on graphene oxide and clay nanosheets exhibit a tensile strength of up to 1,215 ± 80 MPa (mean ± s.d) and a Young's modulus of 198.8 ± 6.5 GPa, while clay-based nanocomposite films reach a toughness of 36.7 ± 3.0 MJ m-3. Superspreading alignment is a versatile and robust approach for the scalable fabrication of high-performance composites for materials science.