Iris sibirica leaf surface: From plant adaptation to biomimetic replication

The present study highlights the vast wealth of information that may be retrieved from the surface of plant leaves, allowing researchers to harmoniously combine concepts from physical chemistry, biology, and plant science, with materials science and engineering, in the development of functional coatings and engineered films. The primary goal of this work was to conduct a comprehensive chemical, morphological, structural, optical, histological, potential distribution, and climatic characterization of Iris sibirica L. leaves. With it, three main axes of research are here reported and discussed: the physical-chemistry of the I. sibirica leaf cuticles, its environmental correlation, and the replication of its hydrophobic properties aiming at future applications. The chemical analysis of the intracuticular and epicuticular waxes on the leaf surfaces of I. sibirica revealed the presence of fatty acids (mainly palmitic and stearic acids), long-chain aliphatic alcohols, and sterols.

Comparison with previous studies enabled a biogeographical distinction between species with higher concentrations of ketones and those richer in alcohols. However, no significant discrimination was observed in the physical chemical parameters such as morphology and wettability. These findings highlight the sophisticated strategies plants use to adapt to environmental changes. Furthermore, the replication of the hydrophobic properties of the I. sibirica leaf surfaces in a transparent and self-standing di-ureasil hybrid film using a nanocasting approach was achieved. The water contact angle (CA) of the leaf-imprinted di-ureasil films demonstrated an impressive enhancement compared to the flat sample analog (97.4 ± 1.6 and 66.3 ± 5.6°, respectively), confirming the key role played by surface microstructure in determining wettability. However, the CA of the biomimetic film replicas remained lower than that of the natural leaf (117–133°), reinforcing the claim that surface wax composition is also pivotal.