Hi All:

There is a recent paper by Karin Glasmastar from Chalmers University in
Sweeden that investigated this problem. It is published in one of the most
recent edition of Langmuir (it is still under the asap category).
They indeed found that there is a lot of silicone transfer whenever PDMS is
contacted to a surface. They suggest that a UV-ozone treatment reduced this
transfer. We found in our work that leaving the  PDMS overnight in ethanol
allowed the leach out of most of the unreacted monomers and oligomers. A
better way was to use a soxhlet extraction in ethanol too.
Karim


-----Original Message-----
From: Alik Widge [mailto:alik@cs.cmu.edu]
Sent: Sunday, June 01, 2003 12:11 PM
To: General MEMS discussion
Subject: Re: [mems-talk] PDMS residue imprint


I recall seeing one paper where PDMS microstamps were extracted overnight
in chloroform to remove low molecular weight residues. I personally have
not had the problem you describe, so I've never tried the extraction. You
should expect, though, that it would cause swelling of your PDMS (as most
organic solvents do), so if the PDMS is adhered to something already, I
suspect it would delaminate due to the strain of the expansion.

Alik Widge
MEMS Laboratory
Carnegie Mellon University


--On Friday, May 30, 2003 4:02 PM -0500 Christopher Khoury
 wrote:

> Group,
>
> is anyone familiar with removing excess residues or uncured monomer from
> PDMS? A patterned imprint residue is highly noticable anytime PDMS comes
> in contact with glass in particular. Usually this imprint can be seen
> through side illumination or scattering off the glass.        So far I've
tried
> pulsed and unpulsed sonication of the PDMS mold in both water and dilute
> ethanol, this only seems to improve things marginally.
>
> Thanks,
>
> C. Khoury
>
>
> Christopher Khoury
> Microsystems Engineer
> Nanosphere, Inc.
> 1818 Skokie Blvd Suite 200
> Northbrook IL 60062
> 847-656-0240
>
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