Durable Gas-entrapping Microstructured Surfaces (GEMS)

Realizing liquid-repellent surfaces without relying on coatings has remained an elusive goal due to the time-dependent degradation and perfluorocarbon unsustainability. In this context, we are investigating gas-entrapping microtextured surfaces (GEMS) comprising arrays of mushroom-shaped doubly reentrant cavities (DRCs). GEMS that have garnered much interest due to their ability to “repel” liquids regardless of the surface chemical make-up. When submerged, they entrap air and their subsequent performance, for instance for frictional drag reduction, depends on the durability of the air entrapment. This requires in depth assessment of the durability of air entrapment in GEMS and the various factors that influence it such as liquid surface tension, cavity dimensions, hydrostatic pressure, breakthrough pressure, and capillary condensation. In response, here, we combine experiments and computational fluid dynamics to investigate the stabilization of advancing liquids on DRCs of circular, square, hexagonal geometries carved on wetting substrates. For comparison, we investigated simple cylindrical cavities under similar conditions. We also explain why DRCs with sharp corners undergo faster Cassie-to-Wenzel transitions than circular DRCs. These findings will lead to superior GEMS.