Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 97: Wetting and Liquids at Interfaces and Surfaces I (joint session CPP/DY/O)
O 97.10: Talk
Thursday, March 19, 2020, 12:00–12:15, ZEU 255
Lucas-Washburn equation applies for four phase contact point — •Peyman Rostami1,2 and Günter Auernhammer1,2 — 1Max Planck Institute for Polymer Research, 55128, Mainz, Germany — 2Leibniz Institute of Polymer Research, 01069, Dresden, Germany
A four-phase contact point, e.g., in merging of immiscible drops, is the point where the liquid-liquid interface advances along the contact line of one drop. The dynamics of drop merging involve various driving and dissipating forces in the dynamics of the four-phase contact point. The viscous friction, i.e. the flow field, within liquids is influenced by the different boundary conditions on the different interfaces (liquid-gas, liquid-liquid, liquid-solid). Additionally, Marangoni stresses between the two liquids and the spreading coefficients along the contact lines play a role. Effectively, these effects lead to a capillary force acting on the four-phase contact point. In total, the situation resembles the capillary flow in open V-shaped groove. The important difference is that, in the classical problem, the grooves are made out of two solid walls, but in the present case one of the *walls* is liquid, i.e., flowable and deformable. We investigate a range of liquids with different combination of physical properties (viscosity ratio, surface and interfacial tensions). The results show a good qualitative agreement for different liquids of the experimental results with the classical Washburn equation (h~square root of time), where h is the filled length of the *groove*.