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

Cornell Affiliated Author(s)

Author

X. Cheng
X. Xu
S.A. Rice
A.R. Dinner
Itai Cohen

Abstract

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.

Date Published

Journal

Proceedings of the National Academy of Sciences of the United States of America

Volume

109

Issue

1

Number of Pages

63-67,

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862908246&doi=10.1073%2fpnas.1118197108&partnerID=40&md5=e591b7b54945a9848ff1a283e8af7aab

DOI

10.1073/pnas.1118197108

Group (Lab)

Itai Cohen Group

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