Relationship between Characteristic Lengths and Effective Saffman Length in Colloidal Monolayers near a Water-Oil Interface

TL;DR

This study experimentally investigates how hydrodynamic interactions in colloidal monolayers near a water-oil interface are characterized by anisotropic characteristic lengths, revealing universal behavior through effective Saffman length analysis.

Contribution

The paper introduces an experimental method to measure characteristic lengths in colloidal monolayers near a liquid-liquid interface and relates these to hydrodynamic interactions using an effective Saffman length.

Findings

Characteristic lengths are anisotropic near the interface.

Universal master curves describe cross-correlated diffusion.

Hydrodynamic interactions are effectively characterized by the Saffman length.

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 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.