I have access to a Heraeus Oven that can pull vacuum, the gauge on it
usually hangs between 50 and 0 mbar at minimum Nitrogen flow, though
for baking the lab manual says to keep it at 300 mbar with Nitrogen.
When I degass the PDMS mix in there I set it to 50 mbar, I don't use
heat, and I use a different oven to bake in.

I will have to check if I can bring FDTS into the lab first. I also
have access to a plasma etcher that has chloroform (I think, their web
server is down right now), oxygen, and a few others. What about the
biosafety of these chemicals on the PDMS?

-Nathan

On Sat, Mar 27, 2010 at 12:22 PM, Kevin Paul Nichols
 wrote:
> Nathan,
>
> To get PDMS to come off, you don't need a very well controlled
> hydrophobic layer. Just use perfluorodecyltrichlorosilane (FDTS)
> applied in a vacuum desiccator, and then baked at ~110. You can find
> FDTS suppliers here: http://www.chemexper.com/
>
> 1) Place your Si wafers (with no PDMS on them, this is just so you end
> up with a long fluorinated molecule sticking up from the surface so
> the PDMS will peel off easily later) in a vacuum desiccator connected
> to house vacuum (do a google image search for vacuum desiccator to see
> what these look like). 2) Place 10-20 uL of FDTS in a small container
> (the top of an eppendorf tube works well) in the bottom of the chamber
> (location doesn't matter much). 3) Pull house vacuum, and leave them
> for ~2 hours (exact time will be more or less depending on the vacuum
> strength and container size). 4) Bake the wafers at 110 for ~2 hours.
>
> There are lots of methods out there to get higher contact angles, but
> that will be good enough.
>
> If you have a goniometer, measure the static contact angle and check
> that it's at least 90 with DI water. If you don't have a goniometer
> handy, just pipette (or somehow dispense) a few microliters of DI
> water on the surface, and make sure that it forms tight balls that
> roll around easily.
>
> Also, keep in mind that most people use PDMS precisely because you
> don't need to ablate, etch, or otherwise chemically attack it. You can
> just use "soft lithography" which uses a stamp to mold the PDMS as it
> cures. Si molds are common, but glass and metal (even CNC machined
> brass molds are good enough for some microfluidic applications). There
> are hundreds of papers out there describing it, if you're interested.
>
> Kevin P Nichols, Ph.D.
>
> Postdoctoral Scholar
> Ismagilov Group
> Department of Chemistry
> Gordon Center CIS E305
> University of Chicago
> 929 East 57th Street
> Chicago, IL 60637
>
> E: kpnichols@uchicago.edu
> T: 773-834-8474
> F: 773-834-3544
>
> On Fri, Mar 26, 2010 at 11:31 PM, Nathan McCorkle  wrote:
>> I am using a laser to ablate PDMS to make channels. I tried peeling
>> off the PDMS layer, but it was attached quite well to both polished
>> aluminum wafers as well as silicon wafers. I am not sure what the best
>> method of getting the PDMS to release will be, please help!
>>
>> -Nathan McCorkle

--
-Nathan McCorkle
---
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics