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Label-free Isolation and Enrichment of Cells Through Contactless Dielectrophoresis
Published on: September 3, 2013
Dielectrophoretic force on a sphere near a planar boundary
Edmond W K Young1, Dongqing Li
1Department of Mechanical and Industrial Engineering, University of Toronto, ON, Canada.
Langmuir : the ACS Journal of Surfaces and Colloids
|December 1, 2005
Summary
The dielectrophoretic (DEP) force, previously omitted, significantly impacts particle-surface gap distances in electrophoresis. Including DEP force leads to higher, more accurate gap predictions, especially at low particle density or high electric fields.
Area of Science:
- Colloid and Surface Science
- Electrokinetics
- Physics of Soft Matter
Background:
- Accurate calculation of electrophoretic mobility requires precise gap distance between colloidal particles and surfaces.
- Forces like van der Waals, electrical double layer, and gravity influence this gap.
- The dielectrophoretic (DEP) force's role in determining this gap was previously underestimated or omitted.
Purpose of the Study:
- To analytically determine the dielectrophoretic (DEP) force acting on a spherical colloidal particle near a surface.
- To investigate the impact of including the DEP force on the calculated particle-surface gap distance.
- To analyze how various parameters influence the equilibrium gap distance.
Main Methods:
- Analytical integration of the Maxwell stress over the particle surface to determine the DEP force.
- Modeling the balance of van der Waals, electrical double layer, gravitational, and DEP forces.
- Investigating the influence of particle density, electric field strength, particle size, zeta potentials, and Hamaker constants.
Main Results:
- Omission of the DEP force consistently led to underpredicted gap distances.
- The DEP force significantly increases gap distances, particularly at low particle densities or high electric fields, reaching micron-scale separations.
- Larger particles generally exhibited smaller equilibrium gap distances.
- Gap distance increases with lower particle density, higher electric field strength, higher zeta potentials, and lower Hamaker constants.
Conclusions:
- The dielectrophoretic force is crucial for accurately determining particle-surface gap distances in electrophoretic systems.
- Previous models underestimated gap distances due to the omission of this force.
- Understanding these forces and parameters is vital for controlling colloidal particle behavior in electric fields.
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