A structural change of a surface led to a significant drop of the roll-off angle/sliding angle. We hypothesize that this is due to a change in the wetting regime. Is there a certain value that separates Cassie-Baxter from Wenzel wetting regime, something like "ROA < x° correspond to Cassie-Baxter while ROA > x° correspond to Wenzel wetting regime."
Benjamin,
To my knowledge, Wenzel considered only rough surfaces, in which the liquid touched the 'hills and valleys' without entrapping air. Cassie/Baxter went a step further by incorporating the formation of liquid-air interfaces as happens on feathers. Cassie/Baxter regime reduces to Wenzel's regime if you leave out the contribution of liquid-air interface from their equation.
Arie
Hi Benjamin
A transition criteria from Wenzel to Cassie-Baxter can be obtained from energy minimization method. The apparent contact angle depend on surface topography and roughness factor.etc,. Maybe you can read the paper 'Optimizing Super-Hydrophobic Surfaces: Criteria for Comparison of Surface Topographies'. There is a clear illustration.
this will help you in understanding
http://www.tandfonline.com/doi/abs/10.1163/156856108X369958
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