Taro leaf inspired micro/nanocellulose-based hierarchical structural coating and its application on O/W separation and food preservation

Abstract

The water-repellent and antibacterial capabilities are essential criteria for textile and packaging materials. This research creates a non-fluorinated, superhydrophobic coating inspired by the hierarchical structure of the Taro leaf, utilizing an emulsion of alkyl ketene dimer (AKD, as secondary roughness) encapsulated within cellulose nanofibres (CNFs), assembling with cellulose microparticles (CMPs, as primary roughness) and TiO2 nanoparticles (as tertiary roughness). The post-recrystallization of AKD plays a vital role in the formation of multi-level surface roughness. Attributing to the driving force generated by water evaporation, the orientation of recrystallized AKD can be regulated either parallel or perpendicular to the substrate. The coated paper exhibited a water contact angle (WCA) of 166.7 ± 3.2° on unsized paper and up to 173 ± 2.0° on filter paper. Cooling temperature and cooling rate play a crucial role on the formation of uniform and stable platelet structures according to the morphology analysis of AKD's recrystallization. Due to the strong superhydrophobicity and the incorporation of TiO2 nanoparticles, the coating possesses self-cleaning and anti-fungal qualities, successfully preventing tomatoes from rotting. In short, this research presents a sustainable approach for the production of aqueous-phase coatings, with potential applications in waterproof surfaces and food packaging.