Contact line, pinning

Plot the shape of the contact line pinned to a defect using Eq. X-30 for water on polyethylene, stearic acid, and platinum. Assume that the upper cutoff length is 2 mm. How does the shape of the pinned contact line compare with your observations of raindrops on dirty windows ... 

Within a feasibility window lie coating quality windows defined by features and sensitivities of the flow states. Similar augmented continuation schemes make it possible to track through parameter space the limiting states at which a microvortex appears or disappears, a static contact line pins to an edge or moves free, a machining flaw creates an unacceptably thick streak, and so forth - and in addition to see how the feasibility and quality windows depend on shape and dimensions of the coating applicator. 

Liu, Y., Zhang, X. Nanobubble stability induced by contact line pinning. J. Chem. Phys. 138, 014706 (2013)... 

I have not touched upon certain areas of research that require a greater knowledge of hydrodynamics or more sophisticated equipment in order to explore their phenomena on the molecular level. Nor have I taken up the wetting and dewetting of real (i.e., dirty) surfaces, on which the contact line pins, so that it may adopt highly complex shapes. 

FIG. 24 Schematic depicting the pinning and depinning of the contact line on an oxide inhomogeneity. (a) Liquid wets the solid metal surface (a) with the equilibrium contact angle 0 - (b) The contact line pins at the intersection of the pure metal/metal oxide interface of the oxide until the contact angle increases to the value of (c) When this occurs, wetting commences over the oxide surface (/ ). 

FIG. 27 Contact line pinning at a geometrical eccentricity on a rough surface. 

Forsberg PSH, Priest C, Brinkmann M, Sedev R, Ralston J (2010) Contact line pinning on microstnictured surfaces for liquids in the Wenzel state. Langmuir 26 860-865... 

Liu J, Mei Y, Xia R (2011) A New wetting mechanism based upon triple contact line pinning. Langmuir 27 196-200... 

---