Abstract
The transport behavior of a system of gravitationally driven colloidal
particles is investigated. The particle interactions are determined by the
superparamagnetic behavior of the particles. They can thus be arranged in a
hexagonal order by application of an external magnetic field. Therefore the
motion of the particles through a narrow channel is governed by this
positioning and a layered structure forms parallel to the walls. The
arrangement of the particles is perturbed by diffusion and the motion induced
by gravity. Due to these combined influences a density gradient forms along the
direction of motion of the particles. A reconfiguration of the ordered
structure is observed leading to a reduction of the number of layers.
Experiments and Brownian dynamics (BD) simulations show that this is due to the
density gradient along the channel. Furthermore we will present simulation
results for particles in counterflow and for various channel geometries.
1) M.~Koppl, P. Henseler, A. Erbe, P. Nielaba and P. Leiderer, Phys.
Rev. Lett. 97, 208302 (2006)
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