University of Illinois, Urbana-Champaign
North Carolina A&T State University, Greensboro
University of California - Irvine
Stanford University, Palo Alto
University of Notre Dame
Northwestern University
In this lab, students will make a simple microfluidic device. They will use this device to investigate the behavior of fluids at this small scale and discover that fluids exhibit laminar flow instead of the more familiar turbulent flow. They will learn what factors causes this different flow behavior and how mcrofluidics in holds great promise for transforming medicine.
If you have any questions about this lab, please contact Joe Muskin at (217) 265-6481 or by email at jmuskin@uiuc.edu.
Purpose:
Chemistry done in test tubes or microtubes use relatively large amounts of liquid in an open environment. If the chemicals are expensive or hard to make, smaller volumes are often desired. Microfluidics allows small scale chemistry so these substances can be created and tested more readily. However, fluids can behave differently in small volumes compared to our experiences with the same fluids in large volumes. If a liquid dyed red and blue are poured side by side, we might expect that it would mix and a purple liquid immerges from the bottom. This activity allows you to test how these fluids behave at the small scale.
Materials:
PDMS
Disposable cup
Petri dish
Puffy Paint
Pre-drilled 2 x 3 inch Plexiglas plates
Large binder clips
Pie tin
Food coloring
Isopropyl (rubbing) alcohol
Plastic knife
Writing utensil
Click on the image above to open a full sized version.
Experimental Procedure
Make microchannel master.
Trace around a Petri dish on a piece of paper and mark the inlets and outlet using the Plexiglas as a guide.
Draw the pattern to test.
Trace pattern with Puffy Paint and allow to dry overnight.
Make microchannels
Add 15 β 25 grams of PDMS elastomer base to a drinking cup (for 1 Petri dish)
Add 1/10 mass (1.5 β 2.5grams) of curing agent crosslinker to the cup and stir with plastic knife.
Carefully pour the PDMS mixture into the Petri dish and gently tap and blow to remove air.
Place the Petri dish into an oven at 65ΒΊ C to cure the PDMS in about 30 minutes. PDMS can also be cured at room temperature for 2 β 3 days.
Assemble Microchannel Device
Remove PDMS from Petri dish when it has cured (firm to the touch).
Add a backing plate of Plexiglas to the bottom (flat side) of the microchannel device.
Add an inlet plate of Plexiglas to the top (channel side) of the microchannel device.
Add binder clips to hold the Plexiglas plates in place.
Determine Device Flow Results
Fill pipettes with fluid.
Carefully add liquids to microfluidic device being sure to add liquid to both channels at about the same rate.
Downloadable Materials:
Activity Guide
Instructors guide containing all relevant information to conduct the lab.
Presentation for teacher to introduce the activity to students. Unlike our other presentations, this one includes video files. Thee files are available for download, but they are in Windows Media Video format. If you're using a Windows machine, you should be able to play them without difficulties, but other platforms may require some effort. We will be updating this presentation in the future to utilize a cross-platform video format.
As with all labs, it is a good idea to use eye protection. However, the supplies used in this lab are very safe, consisting of only water to ethanol colored with food coloring, and PDMS, a polymer that has been tested and found to be safe.
Acknowledgements:
Thanks to Josh Tice, Sarah Perry and Dr. Paul Kenis for all their expertise and assistance.
