Microfluidics: A Step in the Right Direction

Microfluidic devices are great tools for producing fine droplets or emulsions. Most microfluidic devices make use of either a cross-flow or flow-focusing junction — the former produces droplets by crossing two streams of immiscible liquids, say oil and water; the latter achieves the same result by flowing two immiscible liquids through a narrow channel.

Tae Goo Kang and co-workers at the A*STAR Institute of Microelectronics1 have now designed and fabricated a range of silicon-based microfluidic devices that make use of a stepwise flow-focusing junction to generate droplets of tunable size and emulsion characteristics.

To make the microfluidic device, Kang’s team used a deep reactive-ion etching tool to cut micrometer-deep trenches in a silicon wafer. They then used an oxygen plasma ashing and silicon isotropic etching tool to polish the edges of the trenches, and finally capped the device with plain glass or hard plastic. Through this strategy, they were able to create microfluidic devices with ‘microchannels’ that meet at a stepwise flow-focusing junction.

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