Self-assembled capillary arrowsJ. C. Loudet and B. Pouligny
Université de Bordeaux, Centre de Recherche Paul Pascal - CNRS - 115 Avenue A. Schweitzer, Pessac, F - 33600, France, EU
received 10 November 2008; accepted in final form 18 December 2008; published January 2009
published online 30 January 2009
Anisotropic particles adsorbed at a water-air interface are known to aggregate due to capillary interactions. We show that the packing configuration of a pair of prolate ellipsoids critically depends on their relative size and/or aspect ratio mismatch. While identical particles simply pack side-by-side, particles of slightly different sizes are observed to systematically self-assemble into characteristic arrows, i.e. with a finite angle between their axes. The occurrence of such arrows cannot be explained within the far-field approximation of interacting polar quadrupoles. A numerical analysis is worked out which allows us to explore the near-field characteristics of the capillary interaction. Results clearly show the destabilization of the side-by-side configuration due to a size mismatch, in agreement with experimental observations.
82.70.Dd - Colloids.
68.03.Cd - Surface tension and related phenomena.
68.08.Bc - Wetting.
© EPLA 2009