Relationship between characteristic lengths and effective Saffman length in colloidal monolayers near a water–oil interface**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474054, 11774417, and 11604381) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20160238).

Abstract

The hydrodynamic interactions (HIs) in colloidal monolayers are strongly influenced by the boundary conditions and can be directly described in terms of the cross-correlated diffusion of the colloid particles. In this work, we experimentally measured the cross-correlated diffusion in colloidal monolayers near a water–oil interface. The characteristic lengths of the system were obtained by introducing an effective Saffman length. The characteristic lengths of a particle monolayer near a water–oil interface were found to be anisotropic in the longitudinal and transverse directions. From these characteristic lengths, the master curves of cross-correlated diffusion are obtained, which universally describe the HIs near a liquid–liquid interface.