Dynamic Dewetting Regimes Explored
Date
2009
Authors
Fetzer, R.
Ralston, J.
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Journal article
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Journal of Physical Chemistry C, 2009; 113(20):8888-8894
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Abstract
To resolve issues concerning the manner in which substrate wettability and heterogeneity influence contactline motion, we investigate the dewetting process that occurs when a bubble contacts a hydrophobic surfaceimmersed in water. Titania surfaces, partly coated with a self-assembled monolayer of octadecyltrihydrosilane,were used to achieve a wide range of surface composition and wettability. For all surfaces, two distinctdynamic regimes were detected: the initial stage of the dewetting process is captured by hydrodynamics(partly affected by inertia), whereas the regime of low contact line speeds is well described by the molecularkinetic approach, indicating a thermally activated process. In the hydrodynamic regime, physically reasonablemodel parameter values were obtained where inertia is negligible. In the low speed regime, however, theresults contradicted the common expectation that the activation free energy of displacements correlates withthe work of adhesion. Rather quantitative agreement with a microscopic pinning energy was obtained. Ourdata and analysis strongly indicate that pinning controls contact line motion in the low velocity regime ofcontact line motion on chemically heterogeneous surfaces.
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Copyright 2009 American Chemical Society