Non-spherical bubbles

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By Sung Hoon Kang

(not finished yet)


Title: Non-spherical bubbles

Reference: A. B. Subramaniam, M. Abkarian, L. Mahadevan, H. A. Stone, Nature 438, 930 (2005).

Soft matter keywords

surface tension, gas-liquid interface, bubble

Abstract from the original paper

Surface tension gives gas bubbles their perfect spherical shape by minimizing the surface area for a given volume1. Here we show that gas bubbles and liquid drops can exist in stable, non-spherical shapes if the surface is covered, or ‘armoured’, with a close-packed monolayer of particles. When two spherical armoured bubbles are fused, jamming of the particles on the interface supports the unequal stresses that are necessary to stabilize a non-spherical shape.

Soft matter example

Fig. 1. Non-spherical gas bubbles. In a–d, the bubbles are covered with charge-stabilized, fluorescent polystyrene beads, each of 2.6 um diameter. a, Two initially spherical armoured bubbles. b, The bubbles are compressed between two glass plates (see supplementary information for details), which exposes naked interfaces that spontaneously coalesce. c, The gas bubble maintains a stable ellipsoidal shape even after the side plates are removed. d, Armoured bubble with a stable saddle shape. e, The ability to maintain a saddle curvature allows a hole to be introduced into the bubble to create a permanent change of topology into a genus-1 toroid; here the particles are ground zirconium, of average diameter 200 um. f,Non-spherical shapes can be similarly maintained on mineral-oil droplets in water armoured with 4.0-um fluorescent polystyrene particles. Scale bars (um): a–c, 100; d, 200; e, 500; and f, 16.

References