| Colloidal monolayers at a fluid-fluid interface are nowadays routinely realized in experiments, while the technological improvements in the last years have rendered these systems a useful testbed experimental model of questions of fundamental or technological relevance, respectively. Under generic conditions the dominant interaction between the particles of the monolayer is a capillary force due to the induced deformation of the fluid interface -- a specificity of colloids at fluid interfaces as opposed to colloids in bulk. This presentation will focus on the theoretical modelling of this capillary force and its effect on the static and dynamic properties of the monolayer. The mathematical description of the capillary interaction is formally analogous to two-dimensional screened Newtonian gravity, whereby the range of the interaction is the capillary length lambda. In typical monolayers there is a good separation of scales (lambda ~ millimeter, particle size ~ micrometer). Thus, the properties of a capillary-dominated monolayer can exhibit a crossover from those of a Yukawa fluid to those of a self-gravitating fluid. The signature of this crossover on the equilibrium states and the dynamic evolution has been studied with the help of theoretical analysis and numerical simulations, including an assessment of the relevance of the capillary interaction in comparison to the other interparticle forces that have been observed in monolayers (electric forces between charged particles, magnetic forces between magnetized particles, elastic forces in fluid-nematic interfaces). |
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