Digital Microfluidics: Difference between revisions
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=Background= | =Background= | ||
It has been realized in recent years that the classical concept of microfluidics, i.e., the confinement of the flow of single phase liquids to networks of narrow channels, has some fundamental drawbacks. The most obvious one is the fact that in small dimensions, the Reynolds number Re of the flow rarely exceeds unity, such that the flow is purely laminar (the threshold for turbulence is Re > 200). As a consequence, mixing two substances is difficult, and may proceed only by diffusion or, in some cases, be achieved via viscous dephasing. Hence, there has been considerable development towards the use of isolated water droplets suspended in an oily phase. The main advantage considered in this context is the twisty flow pattern emerging within the droplets when they are moved through the channel system. Mixing of two aqueous components is achieved in this way within each droplet separately, and is found to proceed quite efficiently. | |||
Another advantage of this approach, which has been rarely referred to (if at all), is that each droplet may carry chemically different contents. If the volume fraction of the oily phase is kept small, the droplets will touch each other, separated only by a thin oil lamella. A chemical reaction may then be induced, at a precisely defined time, by destroying the lamella, e.g., by local heating. | |||
==Discrete flow (droplet-based)== | ==Discrete flow (droplet-based)== | ||
Revision as of 17:56, 23 November 2007
Background
It has been realized in recent years that the classical concept of microfluidics, i.e., the confinement of the flow of single phase liquids to networks of narrow channels, has some fundamental drawbacks. The most obvious one is the fact that in small dimensions, the Reynolds number Re of the flow rarely exceeds unity, such that the flow is purely laminar (the threshold for turbulence is Re > 200). As a consequence, mixing two substances is difficult, and may proceed only by diffusion or, in some cases, be achieved via viscous dephasing. Hence, there has been considerable development towards the use of isolated water droplets suspended in an oily phase. The main advantage considered in this context is the twisty flow pattern emerging within the droplets when they are moved through the channel system. Mixing of two aqueous components is achieved in this way within each droplet separately, and is found to proceed quite efficiently.
Another advantage of this approach, which has been rarely referred to (if at all), is that each droplet may carry chemically different contents. If the volume fraction of the oily phase is kept small, the droplets will touch each other, separated only by a thin oil lamella. A chemical reaction may then be induced, at a precisely defined time, by destroying the lamella, e.g., by local heating.
Discrete flow (droplet-based)
Electrowetting actuation
Research groups
- Duke University
- MEMS Lab, Washington University, Karl F. Böhringer
- Harvard, Weitz Group
- Wheeler Microfluidics Laboratory
- Garrell research group, UCLA
- Kim's Group, UCLA
- Max Plank Institute
Private Companies
Web links
