02/06/2017 – S. Karpitschka – Marangoni Contraction of Evaporating Sessile Droplets of Binary Mixtures
Séminaire régulier IUSTI – 2 juin 2017 – 11h salle 250
Marangoni Contraction of Evaporating Sessile Droplets of Binary Mixtures
Stefan Karpitschka – Max Planck Institute Göttingen, Allemagne
The evaporation of sessile droplets of liquid mixtures is a ubiquitous natural and industrial process, relevant, e.g., for painting, for cleaning/drying of semiconductor surfaces, or for the patterned deposition of solutes on various length scales. For sessile droplets, the evaporation rate is not uniform but typically has a sharp peak at the contact line. This causes for instance the so-called coffee ring effect, an enrichment of solutes at the edge of the droplet. In the case of liquid mixtures, evaporation causes compositional gradients and thus induces Marangoni flows. Such Marangoni flows may have a significant impact on the droplet and change its shape, wetting behavior, and mobility. Surprisingly, they can also cause an apparent non-wetting behavior, even for liquids that should spread according to their surface energies. I will discuss origin and consequences of this “Marangoni Contraction”, and relate the apparent contact angle to the scaling behavior of the underlying hydrodynamic equations.