Theoretical Study of Electroosmotic Helical Flow in Microchannel

1
Theoretical Study of Electroosmotic Helical Flow
in Microchannel
2002. 3. 22. Kim Sung Jae
Pohang University of Science and
Technology Department of Chemical Engineering
and Division of Mechanical and Industrial
Engineering
2
Introduction
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• Applying non-uniform surface charge condition by
  the slip condition

• Applying AC field

• Stability analysis of the flow field

• Arrange electrodes in suitable positions

4

• The slip velocity condition is clearly
  applicable for typical electroosmotic flow
  applications across a wide range of conditions,
  and in calculating the development of the outer
  flow solution, the slip velocity can be
  approximated as occurring at the wall.

- J. G. Santiago, Anal. Chem., 2001, 73, 2352-2365

• e 80?8.854?10-12 C2/Jm (water)
• z -0.1 V
• E 104 V/m
• m 10-3 kg/ms

e.g.)
Lc 100 mm
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Numerical Simulation
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5cm
200mm
70mm

• Applying non-uniform surface charge condition by
  the slip condition

• Arrange electrodes in suitable positions

7

• Flow3D package which utilize 3D FDM method is
  used to obtain the flow field and particle
  trajectories.
• The microchannel is divided by 11250 cubic
  cell elements.
• 2D FEM is used to obtain potential field which
  is generated by various electrode position.
• The bottom surface of channel is divided by
  1050 triangular elements.

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Simulation Results
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• There is no helical motion due to non-uniform
  surface potential conditions

Fig. Particle trajectory of (c) type surface
potential.
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• We have to investigate electrical field due to
  the position of electrodes.

• The electric field is simply governed by

with complex boundary conditions.
Fig. Example of complex electrode.
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(a)
(b)
(c)
(d)

• Fig. Potential contour of channel.
• Left side of the channel. zz0.
• (b) Bottom surface of the channel. (c) Middle y-z
  plane. zz0/2.
• (d) Middle y-z plane. zz0/4.

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(a)
(b)
(c)
(d)

• Fig. Potential contour of channel.
• Left side of the channel. zz0.
• (b) Bottom surface of the channel. (c) Middle y-z
  plane. zz0/2.
• (d) Middle y-z plane. zz0/4.

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Fig. Particle trajectory in the microchannel.
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(b)
(a)
(c)
Fig. Pressure contours in the microchannel.
(a) x-z plane (b) y-z plane (c)
x-y plane
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Fig. Velocity magnitude contours in the
microchannel. (a) y-z plane at x0
(b) x-y plane
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• Further study of electric potential
• Applying AC electric field.
• Presentation of output