Rates of cavity filling by liquids

Significance In engineering and natural phenomena, various fluids contact rough/textured surfaces, e.g., wicking, facial creams, corrosion-preventive paints, and rain on plant leaves. Liquids on rough surfaces, especially those with cavities, pits, or pores, may or may not transit from the unfilled or partially filled (wetted) state to the fully filled (fully wetted) state. Either one of these states may be desired for a given application (compare superhydrophobicity) or even survival (compare oil-soaked feathers). In this article, we present five variables that control the wetting behavior (cavity filling) of water on intrinsically hydrophilic surfaces with micrometer-sized cavities. Our experimental results and theoretical analysis provide criteria for maintaining either the partially filled state, or quickly transiting to the fully filled state, and insights into other related wetting phenomena.