Wenzel-Cassie wetting transition

Antifogging Self-cleaning Superhydrophobicity Wenzel Cassie-Baxter transition Superoleophobicity Re-entrant angle Directional wetting Unidirectional wetting... 

E. Bormashenko, R. Pogreb, G. Whyman, and M. Erlich, Cassie-Wenzel wetting transition in vibrating drops deposited on rough surfaces Is the dynamic Cassie-Wenzel transition a 2D or ID affair Langmuir 23,6501-6503 (2007). G. Azimi, R. Dhiman, H.-M. Kwon, A. T. Paxson, and K. K. Varanasi, Hydrophobicity of rare-earth oxide ceramics. Nature Mater. 12, 315-320 (2013). 

Stability of the Cassie wetting regime and the Cassie-Wenzel transition have been extensively studied in recent years. 

Application of various external stimuli, such as pressure or vibration, could convert Cassie wetting state into the Wenzel one. " It has been accepted for a long time that the Cassie wetting regime corresponds to a higher energetic state, and the Cassie-Wenzel transition is irreversible. Acmally the situation is more complicated... 

Evaporation of the drop also could promote the wetting transition. Evaporation induced Cassie—Wenzel transitions were first reported by McHale et alp Then evaporation induced wetting transition on the polymer honeycomb and hierarchical superhydrophobic surfaces was studied by Bormashenko The strong dependence... 

Bormashenko E, Bormashenko Y, Stein T, Whyman G, Bormashenko E. (2007) Why do pigeon feathers repel water Hydrophobicity of Pennae, Cassie—Baxter wetting hypothesis and Cassie-Wenzel capillarity-induced wetting transition. / Colloid Interf Sci 311 212-216. 

Bormashenko E, Pogreb R, Whyman G, Erlich M. (2007) Cassie-Wenzel wetting transition in vibrated drops deposited on the rough surfaces Is dynamic Cassie-Wenzel transition 2D or ID affair Langmuir Li 6501—6503. 

The Cassie-Baxter-Wenzel theory [44, 47,48] defines the critical contact angle value on the smooth surface above this value, the Cassie-Baxter model is more stable wetting state and below this value the Wenzel model is the most stable wetting state. If the measured contact angle on a smooth surface is lower than this critical value and if the superhydrophobic behaviour is observed, the transition between the two models should be possible like, for example, with the LDPE surface treated in both plasmas. In this case, the roughness factor is 1.043, the contact angle on the dried surface reaches a value of 171° and the contact angle on the same surface partially wetted with water vapour or dipped in water is only 140°. 

Ran, C., Ding, G., Liu, W, Deng, Y., and Hon, W. 2008. Wetting on Nanoporous Alumina Surface Transition between Wenzel and Cassie States Controlled by Surface Stmcture. Langmuir 24 9952. 

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