Metastable states and wetting transition of submerged superhydrophobic structures

• Published in: Physical review letters Vol. 112; no. 19; p. 196101
• Main Authors: Lv, Pengyu, Xue, Yahui, Shi, Yipeng, Lin, Hao, Duan, Huiling
• Format: Journal Article
• Language: English
• Published: United States 16.05.2014
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.112.196101

Superhydrophobicity on structured surfaces is frequently achieved via the maintenance of liquid-air interfaces adjacent to the trapped air pockets. These interfaces, however, are subject to instabilities due to the Cassie-Baxter-to-Wenzel transition and total wetting. The current work examines in situ liquid-air interfaces on a submerged surface patterned with cylindrical micropores using confocal microscopy. Both the pinned Cassie-Baxter and depinned metastable states are directly observed and measured. The metastable state dynamically evolves, leading to a transition to the Wenzel state. This process is extensively quantified under different ambient pressure conditions, and the data are in good agreement with a diffusion-based model prediction. A similarity law along with a characteristic time scale is derived which governs the lifetime of the air pockets and which can be used to predict the longevity of underwater superhydrophobicity.