TY - JOUR
T1 - Assembly of vorticity-aligned hard-sphere colloidal strings in a simple shear flow
AU - Cheng, Xiang
AU - Xu, Xinliang
AU - Rice, Stuart A.
AU - Dinner, Aaron R.
AU - Cohen, Itai
PY - 2012/1/3
Y1 - 2012/1/3
N2 - 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.
AB - 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.
KW - Colloids
KW - Shear-induced structure
UR - http://www.scopus.com/inward/record.url?scp=84862908246&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84862908246&partnerID=8YFLogxK
U2 - 10.1073/pnas.1118197108
DO - 10.1073/pnas.1118197108
M3 - Article
C2 - 22198839
AN - SCOPUS:84862908246
SN - 0027-8424
VL - 109
SP - 63
EP - 67
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 1
ER -