Plant cuticle-inspired surface functionalization of bamboo: integrating fire resistance, superhydrophobicity, and bioprotection

The widespread application of bamboo, a renewable and eco-friendly material, is hindered by its inherent flammability, hygroscopicity, and susceptibility to biological degradation. Inspired by the hierarchical barrier architecture of the plant leaf cuticle, this study pioneers a cuticle-mimetic bilayer design to develop a multifunctional modified bamboo (PPCU-PDB) via a vacuum-assisted layer-by-layer strategy. This design uniquely couples a crosslinked, cutin-like inner network with a wax-like outer hydrophobic layer. A crosslinked network of polyethyleneimine, phytic acid, and copper(II) ions (PEI-PA-Cu 2+ , PPCU) was constructed on delignified bamboo as the cutin-analogous inner layer, followed by grafting with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDTS) to form the wax-like outer layer. Atomic force microscopy (AFM) and three-dimensional laser scanning microscopy revealed a cross-scale roughness hierarchy (microscale Sa = 12.00 ± 0.31 μm, nanoscale Ra = 44 ± 1.02 nm), which is crucial for stabilizing the Cassie-Baxter wetting state. The modified material achieved a limiting oxygen index (LOI) of 43.19 ± 1.10%. The peak heat release rate (P HRR ) and total heat release (THR) decreased by 50.45 ± 2.21% and 19.98 ± 1.45%, respectively, compared to untreated bamboo. A water contact angle (WCA) of 151.3 ± 1.8° confirmed superhydrophobicity, accompanied by improved dimensional stability (anti-swelling efficiency, ASE = 59.91 ± 2.34%). Antibacterial rates against Staphylococcus aureus and Escherichia coli both exceeded 99.99%, and anti-mold efficacy against Aspergillus niger reached 75 ± 0%. Notably, the biomimetic bamboo retained self-extinguishing capability (LOI′ = 35.68 ± 0.94%) and robust coating integrity even after 14 days of water leaching, a level of post-leaching flame retardancy seldom achieved by bio-based modification systems. This work provides a new cuticle-inspired paradigm for high-performance, durable, and multifunctional bamboo materials.