Particle distribution and velocity in electrokinetically induced banding

  • Massimiliano RossiEmail author
  • Alvaro Marin
  • Necmettin Cevheri
  • Christian J. Kähler
  • Minami Yoda
Research Paper


Colloidal particles may be repelled from/attracted to the walls of glass micro-channels when an electro-osmotic flow is combined with a Poiseuille flow. Under certain conditions, the particles assemble into bands after accumulating near the walls (Cevheri and Yoda in Lab Chip 14(8):1391–1394, 2014). The fundamental physical mechanisms behind these phenomena remain unclear and up to now only measurements within \(1\,\upmu \hbox {m}\) of the walls have been available. In this work, we applied a 3D particle-tracking technique, astigmatism particle tracking velocimetry, to measure the concentration and velocity distribution of particles across the depth of the entire micro-channel. The experiments show that the particles are depleted in the bulk as they become concentrated near the bottom and top walls and this particle redistribution depends strongly upon the bulk particle concentration. The results suggest that bands form in a region where particles are practically immobile and their volume fraction increases at least an order of magnitude with respect to the original volume fraction. Our results suggest that particle accumulation and band formation near the walls may be triggered by forces generated in the bulk since the banding and particle accumulation extends at least a few \(\upmu \hbox {m}\) into the channel, or at length scales beyond the range of surface forces due to wall interactions.


Electrokinetic banding Electro-osmotic flow Micro/nanoparticles Self-assembly Astigmatic-PTV Micro-PIV 



The authors acknowledge financial support by the American National Science Foundation Fluid Dynamics Program (CBET-1235799) and the Deutsche Forschungsgemeinschaft (KA1808/12 and KA1808/22).

Supplementary material

Supplementary material 1 (MP4 3816 kb)

Supplementary material 2 (MP4 4980 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Institute of Fluid Mechanics and AerodynamicsBundeswehr University MunichNeubibergGermany
  2. 2.Physics of FluidsUniversity of TwenteEnschedeThe Netherlands
  3. 3.G. W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlantaUSA

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