8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.75Diffusion of colloidal particles in closed cavities: squareand cylindrical ductsAlessandra Imperio, 1 Johannes Padding, 2 and Wim Briels 11 University of Twente, P. O. Box 217, 7500 AE, Enschede, Netherlands2 IMCN, Université Catholique de Louvain, Louvain-la-Neuve, BelgiumHydrodynamic interactions can be very important in colloidal systems. We study their effect on aparticle confined in micro-cavities. This condition is relevant for many technological applications,involving particles in micro-porous materials. Most of the past work in modeling the mobility of aparticle under confinement has focused on a flat walls or infinitely long cylinders; the motion in aclosed cylinder has been studied in [1, 2, 3] and recently via experiments on micro-sized particlesin [4]. We study the diffusion of a sphere in a closed cylinder via simulations (Multi-ParticleCollision Dynamics). The radius of the cylinder and its height are respectively R = H = 9d, dcolloid diameter. Although the confinement is not extreme the diffusion is strongly affected. Wecalculate the diffusion coefficients for different particle positions. When the particle is in the midplane,experimental data are available and we find good agreement with them [5]. We also study tothe case of a square duct in order to compare the motion nearby a curved surface and near corners,for small Reynolds numbers. When a particle is placed on the axis of an infinitely long conduits,it is expected that the walls effects is larger for circular cavities rather than square cavities, as theaverage sphere’s distance from the walls is least in the cylinder. On the other side, the conditionsin which the particle is fully confined or it is placed in eccentric position in the square duct havenot been fully understood yet. References[1] J. R. Blake, J. Fluid Mech 95, 209 (1979)[2] O. Sano, J. Phys. Soc. Japan 56, 2713 (1987)[3] N. Lecoq et al. , J. Fluid. Mech 585, 127 (2007)[4] H. B. Eral et al. , Langmuir 26, 16722 (2010)[5] A. Imperio et al. , JCP DOI:10. 1063/1. 3578186 (2011)75