EWOD actuation using multimaterial technology
(metal/SU-8/Teflon®) : displacement of biological liquids
Current digital microfluidic systems are often based on the electrowetting effect to perform electrowetting on dielectric (EWOD) which allows fundamental droplet handling operations. The EWOD effect is observed for a conductive droplet placed on an insulating layer which covers a bottom conducting electrode. We propose the photoresist SU-8 as innovative insulating dielectric layer. The results concern the transport of droplets with different prototypes.
Main properties of the device are :
- transport of discret volume of liquid,
- total control of the displacement,
- ability of biochemical treatment of the drop during its transport via functionalized areas or Patterned Wetting Surfaces (PWS)
Two different systems
| Two-plane system | One-plane system | |
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A double plane system where drop is sandwiched
between 2 substrates. Advantages : less evaporation, smaller volume and greater exchange surface due to squeezing of the drop. |
A single plane where the mass electrode is embedded in
the Teflon® layer. Advantages : transport faster as double plane at lower applied voltage. |
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Description of the complete device
The transport part consists of the array of independently addressable control electrodes patterned in a 20 nm thick layer of nickel, which is further coated with dielectric. A hydrophobic layer of Teflon AF 1600 (20 nm) is then deposited.
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Interplane gap: 300 µm; applied voltage : 80 V
Droplet velocity : about 10 mm/s (5 pads/s) |
Droplet Velocity : about 20 mm/s (10 pads/s) |
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