Spontaneous detachment of oil drops from solid substrates: governing factors

We carried out experiments on detachment of oil drops from glass substrates in solutions of an anionic surfactant. The three-phase contact line shrinks spontaneously, and eventually the oil drop detaches from the substrate. Consecutive video frames of such drops are digitized, and the time dependenc...

Full description

Saved in:
Bibliographic Details
Published in:Journal of colloid and interface science 2003-01, Vol.257 (2), p.357-363
Main Authors: Kolev, V.L., Kochijashky, I.I., Danov, K.D., Kralchevsky, P.A., Broze, G., Mehreteab, A.
Format: Article
Language:English
Subjects:
Chemistry
Cleaning of oil from solid surface
Contact angle
Detachment of oil drops from solid substrate
Detergency
Drag force at moving contact line
Dynamic contact line
Exact sciences and technology
General and physical chemistry
Roll-up mechanism
Solid-liquid interface
Surface physical chemistry
Young equation—dynamic
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We carried out experiments on detachment of oil drops from glass substrates in solutions of an anionic surfactant. The three-phase contact line shrinks spontaneously, and eventually the oil drop detaches from the substrate. Consecutive video frames of such drops are digitized, and the time dependencies of the contact radius and angle are determined. Three stages of detachment of a drop, situated above a horizontal substrate, can be distinguished. They correspond to three different driving factors: (1) the interfacial tension decrease because of surfactant adsorption, (2) the aqueous meniscus spontaneously advances owing to the penetration of water between the oil and solid phases, and (3) at sufficiently small contact radius the shape of the oil–water interface becomes unstable and the drop detaches under the action of buoyancy. Analyzing the experimental data, we identified two important characteristics of the drop-detachment process: the velocity of spontaneous advance of the contact line and the line drag coefficient. In the case of moving contact line, a dynamic Young equation must be used, which takes into account the line drag force. The latter is proportional to the velocity of contact-line motion. The experimental data agree with the latter dependence, from whose slope the line drag coefficient is determined.
ISSN:0021-9797
1095-7103
DOI:10.1016/S0021-9797(02)00052-8