Geometrically controlled dynamics in evaporating sessile drops

Abstract eng:
Geometry is found to play a critical role in the evaporation kinetics and flow dynamics of volatile sessile drops of pure liquids and binary mixtures. In non-spherical drops, the coffee ring effect leads to a spatially uneven pattern along the contact line with high-concentration of particles observed at the “comers”. This contrasts to the homogeneous ring stain observed in spherical drops. The local and overall evaporation rates are found to change accordingly. The spontaneous onset and growth of thermocapillary instabilities in more volatile drops also becomes spatially dependent. In this case, “comers” become the areas where the instabilities are first detected, i.e. the most unstable regions. Finally, a segregation process is observed during the alcohol depletion in water-ethanol drops. This phenomenon, once again, is governed by geometry. All the observations are

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