  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 inter-face. The characteristic lengths of the system were
obtained by introducing an effec-tive 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.
