Variations in surface structures and wettability in the genus Pachnoda Burmeister

Abstract

In order to grow and live, all species need access to water and often the ability to control their intake thereof. Among species throughout the world, several animals and plants are known for unique surface patterns and features that influence their wettability in such a way that water is always readily accessible, even in arid and hot climates. In this work, the authors report a journey into the genus Pachnoda, studying 12 species or subspecies to compare their surface properties and wettabilities. This work reveals exceptional natural surface morphologies based on a honeycomb structure with significant variations depending on the Pachnoda genus. Even if the materials present on their surface are intrinsically hydrophilic, some of the species have parahydrophobic properties with apparent contact angles of up to 145° and extremely strong water adhesion. Only the Cassie–Baxter equation can explain these results indicating the presence of trapped air within these surface structures when a liquid, such as water, makes contact. Among the species explored here, water hydrophobicity and adhesion are controlled by the dimensions of the honeycombs, the presence of lamellar structures on the border of these features and the presence of roughness in their internal structures.