Shape-induced capillary interactions of colloidal particles

¹ Division of Engineering and Applied Sciences, Harvard University Cambridge, MA 02138, USA
² University of Twente, Faculty of Applied Physics, Physics of Fluids P.O. Box 217, 7500 AE Enschede, the Netherlands
³ Department of Engineering Sciences and Applied Mathematics Northwestern University - Evanston, IL 60208, USA
⁴ Department of Mechanical Engineering, Northwestern University Evanston, IL 60208, USA

Received: 27 July 2005
Accepted: 21 September 2005

Abstract

We show that near-spherical micrometer-sized colloidal particles at an interface of two fluids experience inter-particle forces merely as a consequence of their shape-induced capillary interaction. The interaction is strong even if the deviations from sphericity are on the nm-scale, and can hardly be avoided in experiment. For particles of 2m radius, a deformation of can result in an attractive potential of 2k_BT at a distance of 4 particle radii. Dynamical simulations of many particles confirm that the forces lead to aggregates of dendritic or hexagonal-lattice type. The latter pattern exhibits strong herringbone-phase orientational order.