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Phoenix666 writes:

When a material, typically a liquid, is confined by surfaces that it doesn't like, the material can be expelled from the confining region in a process called "dewetting."

University of Pennsylvania researchers have now discovered a new facet of this "dewetting" process, showing it is easier to initiate than previously believed. Using computer modeling, they showed how variations in the density of water molecules that are confined between two hydrophobic surfaces, can speed along this process.

Better understanding of dewetting would be helpful in both controlling it and promoting it. On one hand, dewetting decreases the stability of thin films, such as the ones found in smartphone displays. On the other, dewetting is crucial to the function of the water-repelling superhydrophobic surfaces. Dewetting is also implicated in the initiation of boiling. The first places where bubbles appear in a boiling pot of water have to do with dewetting at certain surface sites.
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Visualizing their simulations revealed a new phenomenon: In the initial stages of dewetting, stable bubbles of vapor to form near one surface, rather than span both surfaces.

"As these voids grow, it's possible for them to reach across the surface and make a tube," Patel said. "But, by that point, the vapor tube is already bigger than the critical size predicted by the previous theory and also requires less energy to form. As a result, it's easier to induce dewetting through this new pathway than by starting with a vapor tube and growing it."

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