Experimental observations of bands of suspended colloidal particles subject to shear flow and steady electric field

  • Andrew Yee
  • Minami YodaEmail author
Research Paper


Manipulating suspended colloidal particles flowing through a microchannel is of interest in microfluidics and nanotechnology. However, the flow itself can affect the dynamics of these suspended particles via wall-normal “lift” forces. The near-wall dynamics of particles suspended in shear flow and subject to a dc electric field was quantified in combined Poiseuille and EO flow through a ~ 30 μm deep channel. When the two flows are in opposite directions, the particles are attracted to the wall. They then assemble into very high aspect ratio structures, or concentrated streamwise “bands,” above a minimum electric field magnitude, and, it appears, a minimum near-wall shear rate. These bands only exist over the few micrometers next to the wall and are roughly periodic in the cross-stream direction, although there are no external forces along this direction. Experimental observations and dimensional analysis of the time for the first band to form and the number of bands over a field of view of ~ 200 μm are presented for dilute suspensions of polystyrene particles over a range of particle radii, concentrations, and zeta potentials. To our knowledge, there is no theoretical explanation for band assembly, but the results presented here demonstrate that it occurs over a wide range of different particle and flow parameters.


Colloidal particle assembly Colloidal suspensions Microfluidics Electroosmotic flow Poiseuille flow 



This work was supported by the Mechanical Sciences Division of the U.S. Army Research Office (contract number W911NF-16-1-0278). We thank Shaurya Prakash at the Ohio State University for his advice and comments, and J. P. Alarie at the University of North Carolina for providing the fused-silica microchannels.

Supplementary material

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Supplementary material 1 (AVI 25894 KB)
10404_2018_2136_MOESM2_ESM.pdf (254 kb)
Supplementary material 2 (PDF 254 KB)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.G. W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlantaUSA

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