Marangoni Contraction of Evaporating Sessile Droplets of Binary Mixtures
Orateur : Stefan Karpitschka
Max Planck Institute Göttingem
Abstract : 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.
Date et lieu : vendredi 2 juin à 11h en salle 250 à l’IUSTI