Buckling of drying droplets of colloidal suspensions

Onset of Buckling in Drying Droplets of Colloidal Suspension

Authors: N. Tsapis, E. R. Dufresne, S. S. Sinha, C. S. Riera, J.W. Hutchinson, L. Mahadevan, and D. A. Weitz

Physical Review Letters 94, 018302 (2005)

Soft matter keywords

buckling, elastic shell, drying, sol-gel, Leidenfrost effect

By Tom Kodger

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Abstract from the original paper

Minute concentrations of suspended particles can dramatically alter the behavior of a drying droplet. After a period of isotropic shrinkage, similar to droplets of a pure liquid, these droplets suddenly buckle like an elastic shell. While linear elasticity is able to describe the morphology of the buckled droplets, it fails to predict the onset of buckling. Instead, we find that buckling is coincident with a stress-induced fluid to solid transition in a shell of particles at a droplet’s surface, occurring when attractive capillary forces overcome stabilizing electrostatic forces between particles.

Practical Application of Research

Rapidly dried droplets which contain suspended colloids are found in several industrial areas, and probably in your home office (unless you use a laser printer). Spray drying where fine powders are made by the evaporation of aerosols have been used in the manufacture of foodstuffs, pharmaceuticals, polymers, and detergents.

Capillarity at Work

The authors use a water droplet with suspended colloidal particles, with no added ions; therefore the capillary length l= √(γ/ρ* g) ≈ 2.5mm at 100°C