Particle Separation Using Dielectrophoresis

2003 ◽  
Author(s):  
J. Kadaksham ◽  
P. Singh ◽  
N. Aubry
Keyword(s):  
Dielectric Properties ◽  
Electric Field ◽  
Lagrange Multiplier ◽  
Numerical Scheme ◽  
Particle Separation ◽  
Dielectrophoretic Force ◽  
Dipole Interactions ◽  
Time Required ◽  
Particle Chains ◽  
Er Fluid

A numerical scheme based on the distributed Lagrange multiplier (DLM) method is used to simulate the process of separation of particles with different dielectric properties suspended in an electrorheological (ER) fluid and subjected to a nonuniform electric field. The dielectrophoresis induced separation of particles is possible only when the sign of Clausius-Mossoti factor for the particles is different, as in this case the dielectrophoretic force moves them to different regions of the device. The time required for separation of particle in simulations is larger than that given by an order or magnitude analysis because of the formation of particle chains which arise due to the dipole-dipole interactions among the particles and move much more slowly than isolated particles.

Electrostatic Forces on Particles Floating Within the Interface Between Two Immiscible Fluids

2007 ◽  
Author(s):  
Nadine Aubry ◽  
Pushpendra Singh
Keyword(s):  
Dielectric Properties ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
External Electric Field ◽  
Capillary Force ◽  
Electrostatic Force ◽  
Immiscible Fluids ◽  
Electrostatic Forces ◽  
Dipole Interactions

The objective of this paper is to study the dependence of the electrostatic force that act on a particle within the interface between two immiscible fluids on the parameters such as the dielectric properties of the fluids and particles, the particle’s position within the interface, and the electric field strength. It is shown that the component of electrostatic force normal to the interface varies as a2, where a is the particle radius, and since in equilibrium it is balanced by the vertical capillary force, the interfacial deformation caused by the particle changes when an external electric field is applied. In addition, there are lateral electrostatic forces among the particles due to the dipole-dipole interactions which, when the distance between two particles is O(a), vary as a2, and remain significant for submicron sized particles.

Particle-Particle Interactions on the Surface of a Drop Subjected to a Uniform Electric Field

2008 ◽  
Author(s):  
S. Nudurupati ◽  
M. Janjua ◽  
P. Singh ◽  
N. Aubry
Keyword(s):  
Electric Field ◽  
Immiscible Liquid ◽  
The Other ◽  
Uniform Electric Field ◽  
Particle Interactions ◽  
Drop Surface ◽  
Dielectrophoretic Force ◽  
Dipole Interactions ◽  
Electric Field Direction ◽  
Local Direction

We recently proposed a technique in which an externally applied uniform electric field was used to alter the distribution of particles on the surface of a drop immersed in another immiscible liquid. Particles move along the drop surface to form a ring near the drop equator or collect at the poles depending on their dielectric constant relative to that of the two liquid involved. This motion is due to the dielectrophoretic force that acts upon particles because the electric field on the surface of the drop is non-uniform, despite the fact that the applied electric field is uniform. This technique could be useful to concentrate particles at a drop surface within well-defined regions (poles and equator), and separate two types of particles at the surface of a drop. In this paper we show that in addition to the dielectrophoretic force the particles also interact with each other via the dipole-dipole interactions to form chains or move away from each other depending the local direction of the electric field. The regions in which the local electric field is normal to the drop surface, i.e., the poles, the particles move away from each other. On the other hand, near the equator, where the local direction of electric field is tangential to the drops surface, they form chains that are aligned parallel to the electric field direction.

Redistribution and Removal of Particles From Drop Surfaces

2009 ◽  
Author(s):  
S. Nudurupati ◽  
M. Janjua ◽  
P. Singh ◽  
N. Aubry
Keyword(s):  
Dielectric Properties ◽  
Electric Field ◽  
Physical Properties ◽  
Electric Field Intensity ◽  
Drop Size ◽  
Dimensionless Parameter ◽  
Critical Value ◽  
Uniform Electric Field ◽  
Dielectrophoretic Force ◽  
Drop Radius

It was recently shown by us that particles distributed on the surface of a drop can be concentrated at the poles or equator of the drop by subjecting the latter to a uniform electric field. In this paper, we present experimental results for the dependence of the dielectrophoretic force on the parameters of the system such as the particles’ and drop’s radii and the dielectric properties of the fluids and particles, and define a dimensionless parameter regime for which the technique can work. Specifically, we show that if the drop radius is larger than a critical value, that depends on the physical properties of the drop and ambient fluids and the particles, it is not possible to concentrate particles and thus clean the drop of the particles it carries at its surface because the drop breaks or tip-streams at an electric field intensity smaller than that needed for concentrating particles. However, since the dielectrophoretic force varies inversely with the drop radius, the effectiveness of the concentration mechanism increases with decreasing drop size, and therefore the technique is guaranteed to work provided the drop radius is sufficiently small.

Dielectric properties of dielectrophoretically assembled particulate-polymer composites

1998 ◽  
Vol 13 (1) ◽  
pp. 205-210 ◽  
Author(s):  
C. P. Bowen ◽  
R. E. Newnham ◽  
C. A. Randall
Keyword(s):  
Dielectric Properties ◽  
Electric Field ◽  
Electric Fields ◽  
Dipole Interaction ◽  
Filler Materials ◽  
Polymer Phase ◽  
Dipole Interactions ◽  
Assembly Technique ◽  
Composite Microstructure ◽  
Property Changes

The dielectrophoretic effect is a phenomenon in which dipole-dipole interactions are induced between particles in a suspension by an electric field.1−5 This dipole interaction leads to the formation of chains or fibrils parallel to the applied electric field. Recently, the dielectrophoretic effect has been shown to be a possible composite assembly technique permitting property changes to be induced with the appropriate electric fields.6,7 The results presented in this paper show that the dielectrophoretic assembly process can be used to engineer anisotropy into composite materials. Various filler materials are aligned in a thermoset polyurethane matrix and the dielectric properties are measured. Comparisons are drawn between the dielectrophoretically assembled composites and those processed conventionally in the absence of an electric field. Dielectric properties are modeled with modified mixing laws and discussed in relation to the composite microstructure and the alpha relaxations of the polymer phase.

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