Layering and packing in confined colloidal suspensions. Issue 25 (15th June 2022)

• Record Type: Journal Article
• Authors: Villada-Balbuena, Alejandro; Jung, Gerhard; Zuccolotto-Bernez, Angel B.; Franosch, Thomas; Egelhaaf, Stefan U.
• Is Part Of: Soft matter. Volume 18:Issue 25(2022)
• Page Start: 4699
• Page End: 4714
• Publication Date: 2022-06-15
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/d2sm00412g
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : 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. Abstract : 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.