Hysteresis during contact angles measurement
| Autor: | M. D. Savage, Ramon L. Cerro, Javier Fuentes, M. Elena Diaz |
|---|---|
| Rok vydání: | 2010 |
| Předmět: |
Condensed matter physics
Chemistry Vapor pressure business.industry Drop (liquid) Contact line Surfaces Coatings and Films Electronic Optical and Magnetic Materials Physics::Fluid Dynamics Condensed Matter::Soft Condensed Matter Biomaterials Contact angle Condensed Matter::Materials Science Colloid and Surface Chemistry Optics Adsorption Sessile drop technique Metastability Molecule business |
| Zdroj: | Journal of Colloid and Interface Science. 343:574-583 |
| ISSN: | 0021-9797 |
| DOI: | 10.1016/j.jcis.2009.11.055 |
| Popis: | A theory, based on the presence of an adsorbed film in the vicinity of the triple contact line, provides a molecular interpretation of intrinsic hysteresis during the measurement of static contact angles. Static contact angles are measured by placing a sessile drop on top of a flat solid surface. If the solid surface has not been previously in contact with a vapor phase saturated with the molecules of the liquid phase, the solid surface is free of adsorbed liquid molecules. In the absence of an adsorbed film, molecular forces configure an advancing contact angle larger than the static contact angle. After some time, due to an evaporation/adsorption process, the interface of the drop coexists with an adsorbed film of liquid molecules as part of the equilibrium configuration, denoted as the static contact angle. This equilibrium configuration is metastable because the droplet has a larger vapor pressure than the surrounding flat film. As the drop evaporates, the vapor/liquid interface contracts and the apparent contact line moves towards the center of the drop. During this process, the film left behind is thicker than the adsorbed film and molecular attraction results in a receding contact angle, smaller than the equilibrium contact angle. |
| Databáze: | OpenAIRE |
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