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Phys Rev Lett. 2014 May 16;112(19):196101. Epub 2014 May 12.

Metastable states and wetting transition of submerged superhydrophobic structures.

Author information

1
State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
2
State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China and Key Laboratory of High Energy Density Physics Simulation, Center for Applied Physics and Technology, Peking University, Beijing 100871, China.
3
Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA.

Abstract

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.

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