Team:ETH Zurich/Process/Validation
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+ | To test the different PDMS channels, we engineered an arabinose-dependent sfGFP reporter plasmid. | ||
[[File:ETHZ_arabinose_gradient.png|500px|center|thumb|'''Figure 3: Proof of principle, arabinose-inducible GFP gradient created in the microfluidic PDMS devise ''' ]] | [[File:ETHZ_arabinose_gradient.png|500px|center|thumb|'''Figure 3: Proof of principle, arabinose-inducible GFP gradient created in the microfluidic PDMS devise ''' ]] | ||
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Revision as of 00:11, 29 October 2011
Final Setup and Validation
This page presents description of our final channel design as well as description of its construction, which we did by ourselves. Our final channel is built out of polydimethylsiloxane (PDMS) and constructed with a technique called photolithography. Finally we performed some experiments in the channel in order to validate our design.
Final Channel Design
On the left is the design of our final microfluidic devices, which we made out of polydimethylsiloxane (PDMS). The three chips differ between themselves in their shape and dimensions. On the left side of the chips, each design has a reservoir attached to one end of the channels.
Dimensions of the chips:
- The size of the first two chips is 15 x 33 mm, the size of the last one is 23 x 46 mm.
- The width of the channels is either 0.5 or 1 mm
- Channel length:
- Large chip: (from top to bottom) 30 mm, 15 mm and ca. 60 mm
- Small chip: all 20mm
Final Channel Construction
To construct the microfluidic channels, we used the technique photolithography. Photolithography is done by photopatterning of structures by using a mask (drawing of channels in 2D) and is based on the utilization of particular substances (photoresists) that become soluble to particular solvents after being exposed to UV light [1].
Hereafter a brief description of the photolithography technique: [2]
First, a mask for the microfluidic devices is made by printing the design on glass or quartz or simply on a regular transparency. Then, an SU-8 negative photoresist is spun onto a Si wafer until the final thickness of the photoresist is achieved. The transparency photomask is placed over the Si waver coated with photoresist and the photoresist is exposed to UV light, after which a postexposure bake is performed to crosslink selectively the exposed portions of the photoresist causing the solidification of the material. The sample is put in a beaker containing SU-8 developer to remove the unexposed SU-8. After the sample containing the exposed SU-8 only is is taken out of the baker and dried, PDMS is applied over the SU-8 mold and allowed to cure. SU-8 is removed and a glass is bounded to the PDMS. The channels are constructed. You can read more about the technique here.
![](/wiki/images/d/d6/ETHZ_photolithography.png)
You can see below some photos of the channel building process:
Setup Validation
To test the different PDMS channels, we engineered an arabinose-dependent sfGFP reporter plasmid.
References
[1] [http://www.elveflow.com/microfluidic/16-start-with-microfluidic http://www.elveflow.com/microfluidic/16-start-with-microfluidic]
[2] [http://www.springerlink.com/content/q744ww56gvg05753/#section=91916&page=1 Microfluidic Techniques: Reviews and Protocols, Shelley D. Minteer,
Chapter 3: Fabrication of Polydimethylsiloxane Microfluidics Using SU-8 Molds, Rabih Zaouk, Benjamin Y. Park and Marc J. Madou]