Layering and packing in confined colloidal suspensions

Confinement modifies the properties of a fluid. The particle density is no longer uniform but depends on the distance from the walls; parallel to the walls, layers with different particle densities form. This affects the particle packing in the layers. We investigated colloidal fluids with volume fr...

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Bibliographic Details
Published in:Soft matter 2022-06, Vol.18 (25), p.4699-4714
Main Authors: Villada-Balbuena, Alejandro, Jung, Gerhard, Zuccolotto-Bernez, Angel B, Franosch, Thomas, Egelhaaf, Stefan U
Format: Article
Language:English
Subjects:
Chemistry
Colloids
Confocal microscopy
Distribution functions
Electrostatic properties
Molecular dynamics
Particle density (concentration)
Particle interactions
Radial distribution
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Summary:Confinement modifies the properties of a fluid. The particle density is no longer uniform but depends on the distance from the walls; parallel to the walls, layers with different particle densities form. This affects the particle packing in the layers. We investigated colloidal fluids with volume fractions between 0.19 and 0.32 confined between rough walls. The particle-particle interactions were dominated by hard-sphere interactions but also contained some electrostatic interactions. The particle locations were determined using confocal microscopy and served to calculate the density profile, radial distribution function, anisotropic and generalized structure factors but also to characterize the arrangement of the wall particles leading to the roughness of the walls. The experiments are complemented by molecular dynamics simulations and fundamental-measure theory. While the particle arrangements are mainly controlled by hard-core interactions, electrostatic interactions become more important as the volume fraction decreases. Furthermore, the structure of the rough walls was varied and found to have a significant effect on the fluid structure. An appropriate representation of the rough walls in the simulations is thus crucial to successfully mimic the experiments. Confinement modifies the properties of a fluid. We investigated the inhomogeneous density profiles and the anisotropic packing of colloidal fluids confined between parallel rough walls using experiments, computer simulations and theory.
ISSN:1744-683X
1744-6848
DOI:10.1039/d2sm00412g