Abstract
Optical microscopy and multi-particle tracking are used to investigate the cross-correlated diffusion of quasi two-dimensional colloidal particles near an oil-water interface. The behaviors of the correlated diffusion along longitudinal and transverse direction are asymmetric. It is shown that the characteristic length for longitudinal and transverse correlated diffusion are particle diameter and the distance from particle center to the interface, respectively, for large particle separation . The longitudinal and transverse correlated diffusion coefficient and are independent of the colloidal area fraction when , which indicates that the hydrodynamic interactions(HIs) among the particles are dominated by HIs through the surrounding fluid for small . For high area fraction , the power law exponent for the spatial decay of begins to decrease, which suggests the HIs are more contributed from the 2D particle monolayer self for large .
Highlights
The dynamic behavior of confined colloidal suspensions has recently received a considerable amount of attentions [1,2,3,4,5,6]
The behaviors of the longitudinal and transverse correlated diffusion of particles confined by a two-dimensional (2D) interface or viscous membrane are different [2,16,17,18,19,20,21]: DE!1=r and D\!1=r2, which is caused by the break in the spatial symmetry
We report an experimental measurement of the cross-correlated diffusion of colloidal particles near a waterdecahydronaphthalene interface
Summary
The dynamic behavior of confined colloidal suspensions has recently received a considerable amount of attentions [1,2,3,4,5,6]. Microfluidic devices, porous media, fluid interface or cell membrane [7,8,9,10,11,12,13,14,15] are real-world circumstances in which particles are usually spatially confined. Colloid behavior in spatially confined environments is more complicated than that in unbounded three-dimensional (3D) fluid bulk. The correlated diffusions coefficient DE and D\ between a pair of particles in 3D bulk are well known as DE,D\!1=r and DE~2D\ [16]. The behaviors of the longitudinal and transverse correlated diffusion of particles confined by a two-dimensional (2D) interface or viscous membrane are different [2,16,17,18,19,20,21]: DE!1=r and D\!1=r2, which is caused by the break in the spatial symmetry
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