When marbles challenge pearls

The spectacular nature of non-wetting drops mainly arises from their extreme mobility, and quick-silver, for instance, was named after this property. There are two ways to make water non-wetting, and they both rely on texture: either we can roughen a hydrophobic solid, which makes drops looking like pearls, or we can texture the liquid with a hydrophobic powder that isolates the resulting marble from its substrate. We observe, here, races between pearls and marbles, and report two effects: (1) the static adhesion of the two objects is different in nature, which we interpret as a consequence of the way they meet their substrates; (2) when they move, pearls are generally quicker than marbles, which might arise from the dissimilarity of the liquid/air interface between these two kinds of globules.

Automated summary

The spectacular nature of non-wetting drops is due to their extreme mobility, as exemplified by quicksilver. Two methods to achieve non-wetting involve utilizing texture: roughening a hydrophobic solid to create pearl-like drops, or texturing the liquid with a hydrophobic powder to isolate the resulting marble from its substrate. In this study, we observe and report two effects: the static adhesion of pearls and marbles differs in nature, potentially due to their interaction with the substrate; when in motion, pearls are generally faster than marbles, possibly due to differences in the liquid/air interface between these two types of droplets.