Thermocapillary-driven motion of a sessile drop: Effect of non-monotonic dependence of surface tension on temperature

Karapetsas, G and Sahu, K C and Sefiane, K and Matar, O K (2014) Thermocapillary-driven motion of a sessile drop: Effect of non-monotonic dependence of surface tension on temperature. Langmuir, 30 (15). pp. 4310-4321. ISSN 0743-7463

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Abstract

We study the thermocapillary-driven spreading of a droplet on a nonuniformly heated substrate for fluids associated with a non-monotonic dependence of the surface tension on temperature. We use lubrication theory to derive an evolution equation for the interface that accounts for capillarity and thermocapillarity. The contact line singularity is relieved by using a slip model and a Cox-Voinov relation; the latter features equilibrium contact angles that vary depending on the substrate wettability, which, in turn, is linked to the local temperature. We simulate the spreading of droplets of fluids whose surface tension-temperature curves exhibit a turning point. For cases wherein these turning points correspond to minima, and when these minima are located within the droplet, then thermocapillary stresses drive rapid spreading away from the minima. This gives rise to a significant acceleration of the spreading whose characteristics resemble those associated with the " superspreading" of droplets on hydrophobic substrates. No such behavior is observed for cases in which the turning point corresponds to a surface tension maximum

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IITH Creators:
IITH CreatorsORCiD
Item Type: Article
Uncontrolled Keywords: Drops; Substrates; Surface tension
Subjects: Chemical Engineering > Biochemical Engineering
Divisions: Department of Chemical Engineering
Depositing User: Team Library
Date Deposited: 22 Dec 2014 11:41
Last Modified: 05 Mar 2015 10:28
URI: http://raiithold.iith.ac.in/id/eprint/1225
Publisher URL: http://dox.doi.org/10.1021/la5002682
OA policy: http://www.sherpa.ac.uk/romeo/issn/0743-7463/
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