Capillary-induced interactions between colloids at an interface
  Within a general framework we study the effective, deformation-induced interaction between two colloids trapped at a fluid interface. As an application, we consider the interface deformation owing to the electrostatic field of charged colloids. The effective interaction is attractive and overcomes the direct electrostatic repulsion at large separations if the system is not mechanically isolated. Otherwise, a net attraction seems possible only for large enough colloidal charges. 
Alvaro Dominguez, Martin Oettel, Siegfried Dietrich