Anisotropic and Hindered Diffusion of Colloidal Particles in a Closed Cylinder

• Published in: Langmuir 2010-11, Vol.26 (22), p.16722-16729
• Main Authors: Eral, H. B, Oh, J. M, van den Ende, D, Mugele, F, Duits, M. H. G
• Format: Article
• Language: English
• Subjects: Anisotropy; Chemistry; Colloidal state and disperse state; Colloids - chemistry; Colloids: Surfactants and Self-Assembly, Dispersions, Emulsions, Foams; Diffusion; Exact sciences and technology; General and physical chemistry; Microfluidic Analytical Techniques; Microscopy, Confocal; Models, Molecular; Particle Size; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Printing
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la102273n

Video microscopy and particle tracking were used to measure the spatial dependence of the diffusion coefficient (D α) of colloidal particles in a closed cylindrical cavity. Both the height and radius of the cylinder were equal to 9.0 particle diameters. The number of trapped particles was varied between 1 and 16, which produced similar results. In the center of the cavity, D α turned out to be 0.75D 0 measured in bulk liquid. On approaching the cylindrical wall, a transition region of about 3 particle diameters wide was found in which the radial and azimuthal components of D α decrease to respective values of 0.1D 0 and 0.4D 0, indicating asymmetrical diffusion. Hydrodynamic simulations of local drag coefficients for hard spheres produced very good agreement with experimental results. These findings indicate that the hydrodynamic particle−wall interactions are dominant and that the complete 3D geometry of the confinement needs to be taken into account to predict the spatial dependence of diffusion accurately.