Electrowetting

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Electrowetting

• Joe Martel

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Surface Tension Basics

• Minimize energy Minimize surface area
• Fluid/Solid Interaction
• Wetting
• Non-Wetting

http//en.wikipedia.org/wiki/Wetting
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Types of EWOD
Two-plane System Advantages Less evaporation,
smaller volume, greater exchange surface due to
squeezing of drop.
One-plane System Advantages Faster transport
than double plane at same applied voltage
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Altering Surface Tension
www.uni-ulm.de
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Movement
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Movement (Cont.)
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Dispensing Splitting
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Mixing
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Lippmann-Young Equation

• V applied electric potential
• ?LG liquid-gas surface tension (force/length)
• e dielectric constant (in vacuum and layer)
• ? contact angle (voltage or no voltage)
• d thickness of dielectric layer

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Lippmann-Young (Cont.)
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Navier-Stokes

• Incompressible
• Newtonian fluid
• No external forces
• Constant viscosity

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Applications Lab-on-a-chip

• Automatic processing
• Small sample sizes (ltpL)
• Uses similar fabrication to computer chips
• Current State
• Early design and testing
• Different type of flows
• Miniaturization of sensors

www.physorg.com
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Applications Computer Cooling

• Local hot-spot cooling
• Liquids have higher specific heat
• Constant temperature operation
• Current State
• Controlling droplets
• Effects on circuits

electronics-cooling.com
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References

• On-Chip Electrowetting Cooling Herman Oprins and
  Martine Baelmans
• The Movement of Micro Droplet with the Effects of
  Dielectric Layer and Hydrophobic Surface
  Treatment with R.F. Atmospheric Plasma in EWOD
  Structure Nah-Young Kim, Sung-Min Hong, and
  Soon-Sup Park
• http//en.wikipedia.org/wiki/Lab-on-a-chip
• http//www.iemn.univ-lille1.fr/sites_perso/microfl
  u/ewod.html
• Movies www.ee.duke.edu