What's the best way to mix PDMS?

[Nathan McCorkle]

I plan on spin coating PDMS onto aluminum wafers around 4PM this
afternoon... I haven't opened it up yet to tell how viscous it is and
I'm wondering what the best way to thoroughly mix the two parts (1:10
part mix) together... stirring with a pipet is my first idea, just
dunno if that will be thorough enough or introduce air bubbles

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

[Brent Neal]

If you're too viscous and have trouble with getting good mixing
without introducing a lot of bubbles, try thinning it down with
toluene. If you're spin casting, you're looking for thin films anyway
and you'll thus want a lower viscosity resin. The toluene will evap
off.

B

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Brent Neal, Ph.D.
http://brentn.freeshell.org

[Nathan McCorkle]

Sounds good, I'm looking to get about 50 micron layers, still thin
enough to add solvent?

[Brent Neal]

On Tue, Mar 9, 2010 at 11:41, Nathan McCorkle <nmz...@gmail.com> wrote:
> Sounds good, I'm looking to get about 50 micron layers, still thin
> enough to add solvent?
>
>

Should be. If not, you can always coat 2 layers. :)

B

[Tuhina A Vijay]

Mix it with a glass rod in a beaker and then keep it in a vacuum desiccator for an hour.  Make sure that the volume of the container is atleast double the volume of PDMS you have taken. You can wait upto 2 to 3 hours before you pour on to your Al sheet. That is the pot life.

If you end up introducing bubbles after you pour keep you sheet/ mold in the desiccator for a while.

Tuhina A Vijay,
Dept. of Chemical Engineering,
Indian Institute of Technology Bombay,
Mumbai, India

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[Nathan McCorkle]

Thanks, I ended up mixing in plastic weigh boats, and watched the
weight on a scale as I pipetted by volume... turns out that the
densities of the base and curing agent are pretty much the same, so
mix by either volume or weight and as long as you're consistent it
will be fine.

The vacuum oven without heat is how I degassed it from the bubbles I introduced.

Thanks for the support everyone!

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[Natalia Tchemodanov]

Hi, I used sylgard (corning) PDMS that had the two parts separated in the package and it was dispensed using like a painter's caulking gun. Actually sylgard used to send free samples in that type of package to anyone that requested from a university email acct. You can mix the PDMS with a pipet but it's going to create bubbles (not that many, because mostly they will go away as it cures). If bubbles are a problem with your application you can use a vacuum pump to remove them while your dishes cure.

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