Assembly of vorticity-aligned hard-sphere colloidal strings in a simple shear flow

X. Cheng, X. Xu, S. A. Rice, A. R. Dinner, I. Cohen

Research output: Contribution to journalArticlepeer-review

68 Scopus citations


Colloidal suspensions self-assemble into equilibrium structures ranging from face- and body-centered cubic crystals to binary ionic crystals, and even kagome lattices. When driven out of equilibrium by hydrodynamic interactions, even more diverse structures can be accessed. However, mechanisms underlying out-of-equilibrium assembly are much less understood, though such processes are clearly relevant in many natural and industrial systems. Even in the simple case of hard-sphere colloidal particles under shear, there are conflicting predictions about whether particles link up into string-like structures along the shear flow direction. Here, using confocal microscopy, we measure the shear-induced suspension structure. Surprisingly, rather than flow-aligned strings, we observe log-rolling strings of particles normal to the plane of shear. By employing Stokesian dynamics simulations, we address the mechanism leading to this out-of-equilibrium structure and show that it emerges from a delicate balance between hydrodynamic and interparticle interactions. These results demonstrate a method for assembling large-scale particle structures using shear flows.
Original languageEnglish (US)
Pages (from-to)63-67
Number of pages5
JournalProceedings of the National Academy of Sciences
Issue number1
StatePublished - Dec 23 2011
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-018-02
Acknowledgements: X.C. and I. C. would like to acknowledge T. Beatus, J. Brady, Y.-C. Lin, J. McCoy, D. Pine, and L. Ristroph for help with experiments and useful discussions. X. X., S. A. R., and A. R. D would like to thank J. Brady, J. Morris, and J. Swan for help with the Stokesian dynamics simulations and useful discussions. The research by X. C. and I. C. was supported by grants from the Department of Energy, Basic Energy Sciences. This publication is based on work supported in part by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). X. X., S. A. R., and A. R. D. acknowledge financial and central facilities assistance of the University of Chicago MRSEC, supported by the National Science Foundation (NSF DMR-MRSEC 0820054).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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