This paper studies the bistable nature of the hydrophobic contact angle on the rough surfaces. It was experimentally shown that a droplet of liquid can liquid can form two different contact angles on a surface that has roughness patterns. External disturbances can cause a transition between the two different energy states. This paper verifies the theoretical prediction by matching experiments and establishes a design criterion for a robust hydrophobic rough surface on which the contact angle will not change due to external disturbances. This fact is critical in microfluidic applications, where a rough surface is used for applications based on wettability amplification.

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