Dynamic wetting of a solid by a liquid is critical in a number of applications including high speed coating, enhanced oil recovery, penetration of a liquid into a solid matrix, and the spreading of drops on a solid surface. Air entrainment due to dynamic wetting failure is often the fundamental limit to line speed in liquid coating operations. Numerous empirical and theoretical approaches have been taken to modeling dynamic wetting of a solid by liquids with sharp interfaces between the liquid and vapor phases. However, it is well known that liquid vapor interfaces are not sharp at the molecular level. Here we discuss the effects a diffuse liquid vapor interfaces on wetting. More specifically, we examine, in the vein of Ockham’s razor, the minimum number of assumptions required to explain certain intriguing features of dynamic wetting under the assumption of a diffuse liquid vapor interface.
