Large-area crack-free photonic crystals coating on leather with brilliant and robust iridescent structural color

Fabricating large-area, crack-free colloid photonic crystals (PCs) with highly saturated and robust structural color is essential for their practical applications, such as in the fields of aesthetic decoration, color printing, and textile coloring. However, due to the inhomogeneity of evaporation-induced assembly processes, the fabrication of structure-controllable and large-area PCs with rare defects remains a significant challenge. Here, a large-area, crack-free photonic crystal coating was prepared using a finely controlled doctor-blade-assisted assembly method on a pre-wetted porous leather substrate. The mixture of polymethyl methacrylate spheres suspension (12.5 wt%) and polyacrylate nano-binders was used as prepared without post-treatment. Pre-wetting the porous leather can increase fluid flow in the liquid film and effectively counteract the outward capillary force during the evaporation-induced self-assembly process, thereby reducing the cracks in the PC. Moreover, incorporating polyacrylate nano-binders improves structure stability and further prevents crack formation in the PC coating on leather. The structural colors’ richness can be tuned by varying the particle size, enabling coverage across the entire visible light spectrum. More importantly, applying a waterborne polyurethane encapsulation layer significantly enhances the mechanical and chemical stability of the colorful, enabling it to withstand over 100 cycles of friction, bending, and acid-base soaking without damage.