Particle Dielectrophoresis Modeling in COMSOL 4.2a

Model definition

The modeled domain. The red electrodes are set to 10 V (AC) and the blue electrodes are set to ground (0 V).

• Buffer properties:‒ conductivity 0.56 S/m, relative permittivity 78

• Alternating currents (AC)

‒ Peak potential 10V

‒ frequency 10 Hz

• Modeling domain 30um x 30um x 30um

• Particle density 1050 kg/m3, radius 500nm

‒ pDEP group: conductivity 0.95 S/m, relative permittivity 36

‒ nDEP group: conductivity 0.01 S/m, relative permittivity 2.55

Electric field:

Particle trajectories:

DEPgDpp FFFvmdtd

FD – drag force

Fg – gravitational force

FDEP – dielectrophoretic force

e

i

JDiEJ

QJ

Dielectrophoretic Force

The dielectrophoresis force can be determined from the electric field by

003

~2~~~

)~( EErealrealrFfp

fpfp

ifff

~Complex permittivity of medium

Complex permittivity of particles ippp

~

The sign of the DEP force depends

on Clausius-Mossotti factor :fp

fpCMf

~2~~~~

0~

0~

CM

CM

freal

freal Positive DEP (pDEP), particles attracted to the regions of high electric field magnitude.

Negative DEP (nDEP), particles repelled from the regions of high electric field magnitude.

Two groups of particles are released from the mid-plane of the domain: one group with pDEP and one group with nDEP.

Dielectrophoretic Force

• Use the electric field calculated from the

electric current interface to compute the

DEP force.

• Type in the complex relative permittivity

of the particles and the buffer.

• Activate ‘Use piecewise polynomial

recovery on field’ to improve the accuracy

of force calculation.

Particle Release

Release the particles from the mid-plane

of the domain

Results and Discussions

• The particles (red) with positive Clausius-

Mossotti factor (fCM= 0.19) are attracted to

the high field region.

• The particles (blue) with negative

Clausius-Mossotti factor (fCM= -0.49) are

repelled from the high field region.High field region