Capillarity and Wetting Phenomena: Drops, Bubbles, Pearls, by Pierre-Gilles de Gennes

By Pierre-Gilles de Gennes

As i look out my window within the early morning, i will see beads of droplets gracing a spider net. The movie of dew that has settled at the threads is volatile and breaks up spontaneously into droplets. This phenomenon has implications for the therapy of cloth fibers (the technique referred to as "oiling"), glass, and carbon. it truly is no less significant whilst using mascara! I take my morning bathe. the instant I step out, I dry off in terms of evaporation (which makes me suppose chilly) and by way of dewetting (the technique wherein dry parts shape spontaneously and extend on my skin). As I rush into my automobile lower than a pelting rain, my realization is stuck via small drops caught on my windshield. I additionally discover better drops rolling down and others higher nonetheless that, like snails, go away in the back of them a path of water. I ask myself what the adaptation is among those rolling drops and grains of sand tumbling down an incline. i'm wondering why the smallest drops stay caught. The solutions to such questions do aid motor vehicle brands deal with the skin of glass and alter the lean of windshields.

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Colloid Interface Sci. 133, 452 (1989). 2 Capillarity and Gravity Liquids display rather peculiar properties. 1), move up inclined planes, or rise in very small capillary tubes.! Moreover, drops may lose their spherical shape under the influence of gravity. 1 The Capillary Length /'1;-1 There exists a particular length, denoted A;-l, beyond which gravity becomes important. It is referred to as the capillary length. 8 m/ S2. 1) The distance A;-l is generally of the order of few mm (even for mercury, for which both 'Y and p are large).

20) e The maximum height is reached when = 0, at which point h = y'21\;-1. When observing water on clean glass, the height of the meniscus turns out to be 4 mm, which gives direct information on the value of the capillary length. Remark. 16) leading to ,de/ds = pgz. With ds = -dz/ cose, we get pgzdz = - , cos e de. By interpretation, with the boundary condition e = ~ for z = 0, we get ~pgz2 = ,(I - sin e). The height h of the meniscus is the value of z for = E. 18) once more. , at the wall). Finally, the equilibrium of forces over the entire meniscus in vertical projection is ,cos e E = J pgz(x) dx.

38) References 1 H. Bouasse, Capillarite et phenomenes superficiels (Capillarity and Surface Phenomena) (Paris: Delagrave, 1924). 2 W. Wick, Gouttes d'eau (Water Drops) (Paris: Millefeuilles, 1998). 3 J. Rowlinson and B. : Oxford University Press, 1982). 4 A. W. Adamson, Physical Chemistry of Surfaces (New York: John Wiley and Sons, 1990). References 31 5 Pierre Simon de Laplace, Oeuvres completes de Laplace, t IV, Supplement au livre X du traite de la mecanique celeste (Complete Works of Laplace, tome 4, Supplement to Book 10 of the Treatise On Celestial Mechanics), p.

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