Dynamics of partial wetting

✍ Scribed by F. Brochard-Wyart; P.G. de Gennes

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 423 KB
• Volume: 39
• Category: Article
• ISSN: 0001-8686
• DOI: 10.1016/0001-8686(92)80052-y

✦ Synopsis

Two broad classes of models have been used to describe the motion of a contact line when the contact angle 0 deviates from the equilibrium value & : a) an Eyring approach, emphasizing the microscopic jump of a single molecule at the tip. b) a hydrodynamic approach, concentrating on the viscous losses inside the liquid wedge of angle 0. In the present review, we compare the predictions from both models, for two critical experiments :

1. The pull out of a vertical plate from a fluid at rest -showing (for finite &J a critical velocity V, above which the plate is completely wet.

2. The velocity of growth of a dry patch for a non wettable surface covered by a flat liquid film -which turns out to vary like 6: at small 8,.

The net conclusion is that, at small t3, and for low velocities V, the hydrodynamic losses dominate, while at large 0, and large V, the molecular features are probably important.

I. General aims1

A small liquid drop, deposited on a low energy suzface, forms a spherical cap, with a well defined equilibrium contact angle e,, related to the interfaclal tensions by the celebrated Young equation 0) Yso = YSL + Y cm 0,

(1) (y, ysol and ys refer respectively to the liqui&'air, soWhir, ~li~i~id interfaces).