Stable and unstable surface evolution during the drying of a polymer solution drop.
Drying of a sessile drop of a complex liquid can lead to intriguing complex shapes. We report here a study dealing with a model system, made of a hydrosoluble polymer that is glassy when pure. Under solvent evaporation, polymers accumulate near the vapor/drop interface and may form a glassy skin, which bends as the volume of liquid it encloses decreases. The conditions for the occurrence of this buckling instability have been investigated; the experimental results are well explained by a model that compares the characteristic times for drying and for the formation of a glassy skin. Depending on the experimental conditions, different types of shape distortion take place; secondary instabilities that break the axisymmetry are also observed.
Pauchard
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Laboratoire FAST, Bâtiment 502, Campus Universitaire, Unité Mixte de Recherche Paris VI, Paris XI, CNRS UMR 7608, 91405 Orsay Cedex, France.
Allain
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