Facile spraying fabrication of hierarchical 3D-architected lycopodium spore-based superhydrophobic coatings with robust self-cleaning and anti-bacterial properties

In this paper, an environmentally friendly superhydrophobic (SHP) coating that can be applied to various substrates for protective purposes had been developed through a spraying technique. This coating was composed of Lycopodium spores (LS, with a micron-sized 3D spherical structure), nano-TiO₂, and stearic acid (STA), creating a hierarchical rough structure with a stable cross-linked network. The morphological structure and composition of the obtained coating were thoroughly analyzed. The coating was found to possess outstanding static and dynamic SHP behavior, with a maximum contact angle (CA) of 162.7° and a low sliding angle (SA) of 5.6°. Moreover, this coating not only exhibited superhydrophobicity on a variety of substrates but also demonstrated diversified self-cleaning and water-repellent properties. Meanwhile, the wetting and self-cleaning mechanisms were also discussed. The exceptional stability of the resultant coating was proved by mechanical, chemical and thermal stability tests. In addition, a study was conducted to investigate the impact of SHP coatings on Bacillus subtilis growth and activity when applied to a wooden substrate. The synergistic effect of the high hydrophobicity and the photocatalytic action of TiO₂ enabled the resulting coating to achieve an anti-bacterial efficiency of 88.7 % against Bacillus subtilis, which confirms that the challenges faced by plant-based coating materials in resisting biofouling can be effectively resolved. The as-prepared coating provides an important approach for the preparation of green SHP coatings.