Buckling instability induced by polymer solution drying

The large shape distortions that occur during the drying of sessile drops of polymer solution are shown to be related to a buckling instability. As solvent evaporates, polymers accumulate near the vapor/drop interface and, depending on the experimental conditions, can form a glassy skin which bends as the volume it encloses decreases. A comparison of the times that characterize drying kinetics and glassy skin formation enables us to predict instability occurrence. Good agreement is found with measurements performed at different polymer concentrations, drop volumes and drying rates.