Bioinspired cross-aligned multilayered nanocellulose films through shear-induced orientation

This study investigates the biomimetic fabrication of multilayered nanocomposite films with a cross-aligned architecture, a design directly inspired by the mechanically robust structure of natural load-bearing materials, such as the intervertebral disc and wood cell wall. The films were fabricated by precise layer-by-layer assembly in which cellulose nanocrystals (CNCs) were oriented by controlled shear, with each successive layer rotated perpendicularly to the previous one. Additionally, UV-assisted photopolymerization rapidly locked the aligned structures, resulting in stable and cohesive films composed of locally anisotropic CNC layers. First, the structural anisotropy was tracked from the liquid suspension phase using small-angle light scattering (SALS) and dichroism to understand the influence of its structure on the anisotropic organization of the resulting films. Second, small- and wide-angle X-ray scattering (SAXS and WAXS) analyses of the UV-cured films provided quantitative nanoscale evidence of the permanent CNC alignment in layers, together with the perpendicular CNC orientation across layers after fabrication. By comparison with unidirectionally aligned materials, the mechanical performance of the resulting architecturally-structured films is remarkable, as they exhibit a 51% increase in compression modulus and a 91% improvement in tensile ductility. These findings open up new perspectives for the design of bioinspired materials with tailored structural and mechanical properties, able to mimic natural hierarchical architectures.