Beyond superhydrophobicity: A fluorine-free and scalable strategy to impart wood with comprehensive robustness

The extensive utilization of superhydrophobic wood is currently impeded by the poor durability of coatings and the reliance on toxic low-surface-energy chemicals. Herein, a fluorine-free superhydrophobic coating was developed, and consequently, a superhydrophobic wood with comprehensive robustness was fabricated based on this formulation. Specifically, the essential surface roughness was created using SiO 2 particles. Cellulose nanofibrils (CNFs) were incorporated simultaneously as a dispersant and a reinforcing phase, suppressing particle agglomeration and enhanced the durability of the superhydrophobic wood. Furthermore, low-surface-energy modification utilizing hexadecyltrimethoxysilane (HDTMS) and polydimethylsiloxane (PDMS) were implemented to achieve hydrophobic grafting at the molecular level and cross-linked encapsulation at the macroscopic scale. Through the synergistic design that integrates mechanical reinforcement of CNFs, chemical inertness with minimized surface energy of HDTMS/PDMS, and hierarchical surface architectures of SiO 2 , the superhydrophobic performance of wood was systematically optimized across the physical, chemical, and structural dimensions. Specifically, the surface exhibited superhydrophobicity with a static contact angle of 157.6° and a sliding angle of 6.3°. The material also demonstrated excellent durability, maintaining its superhydrophobicity after prolonged exposure to harsh conditions, including saltwater immersion (96 h), chemical corrosion (pH = 2–12), sandpaper abrasion (200 cm under 100 g), tape peeling (200 cycles), UV aging (216 h), and outdoor exposure (25 days). This durability arises from the synergy between its chemically stable components and reinforced micro-nano structure, in which nano-SiO 2 particles play a key role in enhancing UV resistance by absorbing and scattering radiation to prevent polymer photo-oxidation. The coating also demonstrated broad substrate universality, performing effectively on diverse materials such as paper, cotton, glass, wood, and metals, highlighting its potential as a universal superhydrophobic solution. In summary, this work presents a scalable, eco-friendly strategy for creating durable, high-performance superhydrophobic wood, paving the way for next-generation materials.