Functional patterning of PDMS microfluidic devices using integrated chemo-masks

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Original entry by Caspar Floryan, APPHY 225 Fall 2010

Reference

"Functional patterning of PDMS microfluidic devices using integrated chemo-masks" Mark B. Romanowsky, Michael Heymann, Adam R. Abate, Amber T. Krummel, Seth Fraden and David A. Weitz. Lab on a Chip 10, 1521–1524 (2010).

Keywords

PDMS, Microfluidics, Emulsions, Patterning, Chemo-masks

Summary

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A new method for patterning surface properties in PDMS (Polydimethylsiloxane) channels is presented here. Air reservoirs were created in the PDMS. As the polymer cured, the reservoirs diffused oxygen into nearby channel segments thus inhibiting functional polymer growth. The placement of the reservoirs controlled the polymerization pattern. PDMS is an important and commonly used material in microfluidics. It is used to quickly mold channels, valves and other microfluidic features. Some microfluidic applications require spatially patterned surface properties which are difficult to create using existing techniques, often requiring extremely precise photomask alignments. The method presented here uses simple oxygen reservoirs to robustly control the polymerization of PDMS. The air reservoirs can have irregular shapes and this method could enable patterning of 3-D devices if the chemo-masks are placed above or below, as well as beside flow channels. Chemo masks modestly increase the footprint of PDMS devices.

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Soft Matter Connection

This paper touches on several aspects of soft matter, including microfluidics, polymers (PDMS), and emulsions. Microfluidics manipulate fluids at low Reynolds numbers and at a small scale where statistical mechnics become important. PDMS is a important material from which microfluidics are made of and itself also exhibits soft matter traits. Emulsions are forms of soft matter consisting of droplets of one fluid inside, surrounded by another.