Contact line dynamics in the late-stage coalescence of diethylene glycol drops.
We investigated the contact line dynamics of a composite drop formed as a result of the coalescence during the condensation of two diethylene glycol (DEG) drops at -4 degrees C on a silicon surface. The composite drop relaxes exponentially toward equilibrium with a typical relaxation time, tc, which depends on the equilibrium radius, R, of the composite drop. The value of tc is found to be in the range of 10-100 s for R approximately 1-4 microm. The relaxation dynamics is found to be larger by 6 orders of magnitude than that predicted by bulk hydrodynamics because of high dissipation in the contact line vicinity. Similar to low viscous liquids (water), this high dissipation can be attributed to an Arrhenius factor resulting from the phase change in the contact line vicinity and to the influence of surface defects that pin the contact line.
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Equipe du Supercritique pour l'Environnement, les Matériaux et l'Espace, Ecole Supérieure de Physique et Chimie Industrielle, Laboratoire de Physique et Mécanique des Milieux Hétérogènes, rue Vauquelin, 75231 Paris Cedex 05, France. daniel.beysens@cea.fr
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