Experimental Soft Condensed Matter Group Harvard University, Prof. D. A. Weitz Cool Picture of the Moment

Glass coating for PDMS microfluidic channel by sol-gel methods

Soft lithography using polydimethylsiloxane (PDMS) allows one to fabricate complex microfluidic devices easily and at low cost. However, PDMS swells in the presence of many organic solvents significantly degrading the performance of the device. We have developed a method to coat PDMS channels with a glass-like layer using sol-gel chemistry. This coating greatly increases chemical resistance of the channels; moreover, it can be functionalized with a wide range of chemicals to precisely control interfacial properties. This method combines the ease of fabrication afforded by soft-lithography with the precision control and chemical robustness afforded by glass.

SEM images of PDMS channel cross sections are shown above. The uncoated channel has a standard rectangular cross-section, as shown in (a). The coated channel has a round cross section, as shown in (b). The rounded shape is due to the uncured liquid coating wetting the channel walls and collecting in the corners. It is cured by heating at 100 C for 2 minutes. The coating can be applied to hundreds of microfluidic devices in parallel using a new passive coating method which we have developed.

To study the chemical resistance of the coating, we flow toluene, an organic solvent that significantly swells PDMS, through coated and uncoated channels. In the movies, shown in real-time, the uncoated channel swells and collapses in a matter of seconds. By contrast, the coated channel channel is not swollen, and remains clear, open, and functional.

The devices therefore retain the low-cost and ease of fabrication of stamped PDMS devices but gain the the chemical resistance and versatility of more expensive glass-etched or micro-capillary devices.

For more information contact Adam Abate.

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