Experimental observation of the crystallization of hard sphere colloidal particles by sedimentation onto flat patterned surfaces

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by Tom Kodger


I.B. Ramsteiner, K.E. Jensen, D.A. Weitz, F. Spaepen. PRE 79, 011403 (2009);


Colloidal crystal, patterned substrate, bond order parameter, template


We present a confocal microscopy study of 1.55 μm monodisperse silica hard spheres as they sediment and crystallize at the bottom wall of a container. If the particles sediment onto a feature less flat wall, the two bottom layers crystallize simultaneously and layerwise growth follows. If the wall is replaced by a hexagonal template, only layerwise growth occurs. Our results complement earlier numerical simulations and experiments on other colloidal systems.

Capillarity In Action

FIG. 1. Selected snapshots of the first three sedimented layers for four different area densities labels on top. Darker particles have higher-order parameters.

While this paper contains very little capillarity, despite applying sedimentation concepts, the paper contains several useful experimental approaches, such as a bond order parameter, that could be used in other capillarity analyses.

Briefly, the experiment system contains monodispersed silica spheres at low volume fraction in a fluorescent DMSO/water solution. Due to a density difference between the 2 components, these spheres slowly sediment according to,

<math>u_0=\frac{1}{18}\sigma^2\Delta\rho g/\eta \approx 4.7mm</math>