Dresden 2017 – wissenschaftliches Programm
CPP 62.2: Vortrag
Donnerstag, 23. März 2017, 15:15–15:30, ZEU 255
Wetting over pre-existing liquid films - a tsunami on microscale — •Hannu Teisala, Anke Kaltbeitzel, Werner Steffen, Hans-Jürgen Butt, and Doris Vollmer — Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
Wetting of solids by liquids is a ubiquitous phenomenon of our everyday life. It is of utmost importance in several industrial operations including variety of coating applications, self-cleaning, oil recovery, heat transfer, and water harvesting from humid air. Static wetting situations, where the surface tension forces, γ, between solid, liquid, and gas phases balance with gravity leading to an energetically favored equilibrium state, are rather well understood. Comprehension of dynamic wetting situations, which are more common in real environment, is a challenge. Especially, wetting over pre-existing liquid films and the hydrodynamics within menisci - which are determined by the interplay of surface tension forces, gravity, and viscous stresses within the liquid - are poorly understood. Here we show how negative Laplace pressure acting at the meniscus of silicone oil, a common lubricant, induces a strong capillary suction that dominates the interface curvature and hydrodynamics when the meniscus is resting on or advancing over a thin film of the same liquid. The drastic consequences of negative Laplace pressure in wetting over liquid films have not been recognized earlier. Our findings add knowledge in the field of wetting and contribute to resolving generic issues such as homogeneous film formation in coating and meniscus formation, its hydrodynamics, and depletion of lubricant on slippery, lubricated surfaces.