XIX Sympozjum Srodowiskowe PTZE - materialy.pdf
XIX Sympozjum Srodowiskowe PTZE - materialy.pdf
XIX Sympozjum Srodowiskowe PTZE - materialy.pdf
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<strong>XIX</strong> <strong>Sympozjum</strong> <strong>PTZE</strong>, Worliny 2009<br />
A NUMERICAL ANALYSIS OF FORCES IMPOSED<br />
ON PARTICLES IN AC DIELECTROPHORESIS<br />
Eugeniusz Kurgan, Piotr Gas<br />
AGH University of Science and Technology<br />
Deptartment of Electrical and Power Control Engineering<br />
al. Mickiewicza 30, 30-059 Kraków, Poland<br />
e-mail: kurgan@agh.edu.pl, piotr.gas@agh.edu.pl<br />
Abstract: This paper analyzes the forces, induced by the external AC field generated by interdigitated<br />
electrodes, imposed on the particles in AC conventional dielectrophoresis in a two-dimensional mathematical<br />
model. The conditions for the positive and negative dielectrophoresis are presented. Interdigitated electrodes are<br />
commonly used within such devices to generate the non-uniform electric fields that induce particle movement.<br />
Among other parameters, the magnitude of the DEP force depends upon the gradient of the square of the electric<br />
field that is generated by such arragements. By understanding the effect that the dimensions of the electrodes<br />
have on this quantity, micro-fluidic devices can be designed to produce the most effective dielectrophoretic<br />
effect on the biological and other physicalparticles. This article examines the relationship between the geometry<br />
of the interdigitated electrodes and the magnitude of the DEP force. This is done by obtaining and analyzing an<br />
equation for the gradient of the square of the electric field.<br />
Keywords: dielectrophoresis, polarization of particles, finite element method.<br />
Introduction<br />
In praxis knowledge of mechanism for the micro-fluidic transport and separation of small<br />
biological samples such as cells, proteins, and DNA is very important. For practical problems<br />
interdigitated electrodes are commonly used to generate the non-uniform electric fields. This<br />
field induces dipole moment and next the force resulting from this is the cause of particle<br />
movement. Among other factors, the magnitude of the dielectropho-retic force depends upon<br />
the gradient of the square of the magnitude of electric field that is generated by such<br />
electrodes. All materials from electrical point of view is composed of positive and negative<br />
charges which experience an electrostatic force when is placed in an electric field. In a<br />
uniform electric field, electrically neutral particles experience a dielectric polarization, but no<br />
net force. In a nonuniform electric field, however, forces acting on polarised charges are not<br />
balanced, and a motion called dielectrophoresis (DEP) occurs.<br />
Main equations<br />
When a particle is placed in an electrical field, it experiences a dielectrophoretic force given by<br />
[1, 2, 3]<br />
1<br />
F = qE+<br />
( m∇ ) E+ ∇( Q: ∇ E ) + ... (1)<br />
el<br />
6<br />
The first term in the above equation describes the coulombic interaction between the single<br />
charge q of the particle and the electrical field E and embodies all electrophoretic phenomena.<br />
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