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Revision as of 02:30, 27 October 2006
Our microfluidic channel research is going well. We have successfully constructed polydimethylsiloxane (PDMS) microchannels and altered their surface chemistry via O2 plasma coating. The O2 plasma coating process creates a hydrophilic environment in the channels so that when placed on low density Eiken agar, they create a microfluidic device by drawing liquid from the media itself (see photo bottom right). Our swarm assays are grown on this media, and when the channels are placed on the edge of the colony, swarming E. coli swim through the channels. At this point, we have successfully demonstrated the ability of our swarming cells to work with this microfluidic device using differential interference contrast (DIC) microscopy (see photo bottom center). It is our goal to also be able to use a combination of DIC and fluorescence microscopy to track E. coli strains containing various fluorescent proteins (RFP, YFP, and GFP).
We are also currently working on developing a technique to use thinner sections of media in order to increase the quality of our DIC microscopy. We have considered two methods of action. The first involves using an acrylic microscope slide of our design that has a shallow chamber in the middle with a bonded glass bottom (see photo bottom left). This would allow us to pour small amounts of agar into the slide, and the entire swarm assay along with the microchannel experiments would be carried out on the slide itself. The other avenue we are considering is using spin coating techniques to apply thin layers of Eiken agar to standard glass slides. Both methods are currently being tested for viability.
The sequence of photos below show a single E. coli cell swimming along the side of our microfluidic channel. The channel is 10 microns wide and the growth medium used is 0.25% Eiken agar. The movie sequence was taken using a Nikon Eclipse Differential Interference Contrast microscope using a 40x air objective. The photos were adjusted for increased contrast and clarity using Scion Image (Scion Corp.) and Adobe After Effects.