Skip to main content
×
Home
    • Aa
    • Aa

Dipolophoresis in large-scale suspensions of ideally polarizable spheres

  • JAE SUNG PARK (a1) and DAVID SAINTILLAN (a1)
Abstract

The nonlinear dynamics of uncharged ideally polarizable spheres freely suspended in a viscous electrolyte in a uniform electric field are analysed using theory and numerical simulations. When a sphere polarizes under the action of the field, it acquires a non-uniform surface charge, which results in an electro-osmotic flow near its surface that scales quadratically with the applied field magnitude. While this so-called induced-charge electrophoresis yields no net motion in the case of a single sphere, it can drive relative motions by symmetry breaking when several particles are present. In addition, Maxwell stresses in the fluid also result in non-zero dielectrophoretic forces, which also cause particle motions. The combination of these two nonlinear electrokinetic effects, termed dipolophoresis, is analysed in detail by using numerical simulations. An efficient simulation method based on our previous analysis of pair interactions is presented and accounts for both far-field and near-field electric and hydrodynamic interactions in the thin-Debye-layer limit, as well as steric interactions using a novel contact algorithm. Simulation results in large-scale suspensions with periodic boundary conditions are presented. While the dynamics under dielectrophoresis alone are shown to be characterized by particle chaining along the field direction, in agreement with previous investigations, chaining is not found to occur under dipolophoresis, which instead causes transient particle pairings and results in a non-uniform microstructure with large number of density fluctuations, as we demonstrate by calculating pair distribution functions and particle occupancy statistics. Dipolophoresis is also found to result in significant hydrodynamic dispersion and velocity fluctuations, and the dependence of these two effects on suspension volume fraction is investigated.

Copyright
Corresponding author
Email address for correspondence: dstn@illinois.edu
Linked references
Hide All

This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

P. C. Hiemenz & R. Rajagopalan 1997 Principles of Colloid and Surface Chemistry. CRC.

T. B. Jones 1995 Electromechanics of Particles. Cambridge University Press.

C. Pozrikidis 1992 Boundary Integral and Singularity Methods for Linearized Viscous Flow. Cambridge University Press.

W. B. Russel , D. A. Saville & W. R. Schowalter 1989 Colloidal Dispersions. Cambridge University Press.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×
MathJax

Keywords:

Type Description Title
VIDEO
Movies

Park and Saintillan supplementary movie
Movie 3. Two-dimensional particle dynamics in a monolayer of 100 spheres undergoing dipolophoresis (combination of dielectrophoresis and induced-charge electrophoresis) under a uniform external electric field, in a periodic box of dimensions 50 x 3 x 50 and at a volume fraction of 5.59%. The electric field points in the vertical direction. DIP results in particle pairing events, as well as in the formation of transient particle clusters and clarified regions. It also causes hydrodynamic diffusion. The occasional particle flickers are a consequence of the periodic boundary conditions, by which a particle leaving the simulation box immediately reenters on the other side.

 Video (5.1 MB)
5.1 MB
VIDEO
Movies

Park and Saintillan supplementary movie
Movie 2. Dynamics in a suspension of 100 spheres undergoing dipolophoresis (combination of dielectrophoresis and induced-charge electrophoresis) under a uniform external electric field, in a periodic box of dimensions 20 x 20 x 20 and at a volume fraction of 5.24%. The electric field points in the vertical direction. DIP results in the formation of transient particle clusters, and also causes hydrodynamic diffusion. The occasional particle flickers are a consequence of the periodic boundary conditions, by which a particle leaving the simulation box immediately reenters on the other side.

 Video (5.1 MB)
5.1 MB
VIDEO
Movies

Park and Saintillan supplementary movie
Movie 1. Dynamics in a suspension of 100 spheres undergoing dielectrophoresis under a uniform external electric field, in a periodic box of dimensions 20 x 20 x 20 and at a volume fraction of 5.24%. The electric field points in the vertical direction. DEP forces give rise to the formation of particle chains in the direction of the field. The occasional particle flickers are a consequence of the periodic boundary conditions, by which a particle leaving the simulation box immediately reenters on the other side.

 Video (3.7 MB)
3.7 MB

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 16 *
Loading metrics...

Abstract views

Total abstract views: 54 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 25th May 2017. This data will be updated every 24 hours.