Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 44: Micro- and Nanofluidics I
CPP 44.5: Vortrag
Donnerstag, 17. März 2011, 15:00–15:15, ZEU 160
Omniphobicity Scrutinized with a Phase-Field Approach — •Walter Mickel1,2 and Thierry Biben1 — 1Université de Lyon, F-69000, Lyon, France; Université Lyon 1, F-69622, Villeurbanne, France; CNRS, UMR5586, Laboratoire PMCN — 2Institut für Theoretische Physik, Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen, Germany
Spreading liquids on a rough surface with pillars may result in a penetrated Wenzel-state where liquid enters the grooves or a fakir state with air-pockets suspending the liquid above. On micronic scales this behavior is very well described with the Wenzel- and Cassie-Baxter laws. According to this theory hydrophobic materials are needed to obtain superhydrophobic states due to the roughness induced amplification of the hydrophobicity. An inversion of the wetting behavior due to roughness, could not be explained by the theory. However experiments from Ramos[1] and simulations from Daub[2] showed that intrinsic hydrophilic materials could render hydrophobic with appropriate surface structures. Such materials are called omniphobic.
We study the mechansims which lead to omniphobic substrates with a phase-field model[3] coming from mesoscale to nanoscale wetting. With this model we investigate the free energy landscape to quantify metastabilities and dynamic transistions. Further we report the impact of several roughness parameters on the wetting inversion. We discuss the capillary filling of grooves and show a mesoscopic wetting theory.
[1] S. Ramos, Langmuir 26 (2010) 5141-6 [2] C.D. Daub, Faraday Discussions 146 (2010) 67-77 [3] T. Biben, PRL 100 (2008) 186103