Electrokinetic Micro Flows

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Electrokinetic Micro Flows

• Mark Fleury
• Chemical Engineering

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Electrokinetic Flows-A summary

• Why do we need Electrokinetics?
• How does it work?
• What does it look like?
• Questions

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Why do we need Electrokinetics?

• Lab on a chip
• Working on scales too small for mechanical
  devices
• Effective scales range from 1nm to 10 microns

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How does it work?

• Charged particles (ions) respond to an applied
  electric field by moving.
• If conditions are right, the fluid moves with the
  ions creating bulk flow.
• What are the right conditions?
• Ions in solution
• Applied electric field
• Charged channel surface

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If ions are too spread out, only they move and
not the fluid.
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Electrokinetics requires a charged surface

• Charged surface attracts ions to the channel
  wall.
• This is called the Electric Double Layer (EDL)
• Charged surface is independent of applied
  electric field.

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Look at the math Navier Stokes Equation
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Standard parabolic solution
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Navier Stokes w/ Electrokinetic Term
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Velocity profile w/ only Electrokinetic Effects
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Combined Velocity ProfileElectric and Pressure
Effects
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Summary

• Applications-Lab on a chip
• Whats required
• Ions
• Charged surface
• Applied electric field
• How does it work?
• Moving ions in solutions creates moving wall
• Equations describe flow.
• Questions?

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