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Issue 8, 2017
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Dynamic self-assembly of charged colloidal strings and walls in simple fluid flows

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Abstract

Colloidal particles can self-assemble into various ordered structures in fluid flows that have potential applications in biomedicine, materials synthesis and encryption. These dynamic processes are also of fundamental interest for probing the general principles of self-assembly under non-equilibrium conditions. Here, we report a simple microfluidic experiment, where charged colloidal particles self-assemble into flow-aligned 1D strings with regular particle spacing near a solid boundary. Using high-speed confocal microscopy, we systematically investigate the influence of flow rates, electrostatics and particle polydispersity on the observed string structures. By studying the detailed dynamics of stable flow-driven particle pairs, we quantitatively characterize interparticle interactions. Based on the results, we construct a simple model that explains the intriguing non-equilibrium self-assembly process. Our study shows that the colloidal strings arise from a delicate balance between attractive hydrodynamic coupling and repulsive electrostatic interaction between particles. Finally, we demonstrate that, with the assistance of transverse electric fields, a similar mechanism also leads to the formation of 2D colloidal walls.

Graphical abstract: Dynamic self-assembly of charged colloidal strings and walls in simple fluid flows

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Supplementary files

Article information


Submitted
08 Nov 2016
Accepted
18 Jan 2017
First published
24 Jan 2017

Soft Matter, 2017,13, 1681-1692
Article type
Paper

Dynamic self-assembly of charged colloidal strings and walls in simple fluid flows

Y. Abe, B. Zhang, L. Gordillo, A. M. Karim, L. F. Francis and X. Cheng, Soft Matter, 2017, 13, 1681
DOI: 10.1039/C6SM02524B

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