PDMS does shrink by a percent or two on curing.

There are two ways I know to alleviate this - the first is simply to cure at
room temperature (although this takes longer, ~24-48 hours, and holes become
harder to punch cleanly). The second is to scale your SU-8 master to
compensate. The shrinkage should be reproducible if identical curing
conditions and PDMS thickness is used each time.

Hope this helps.

On Sun, Sep 27, 2009 at 17:28, nidhi maheshwari  wrote:

> Dear All,
>
> I have to do some photolithography patterning into PDMS channels. I am
> facing a challenge in alignment as PDMS seems to be shrinking once it
> is taken out from the master on which it is casted. The extent of
> shrinkage also varies from one PDMS sheet to another.
> Incidentally, this PDMS is not even matching the SU-8 master from
> which it was casted (tried aligning PDMS channels and SU-8 master on
> double sided aligner).
>
> I would like to know if such a problem was faced by anyone and what
> can be the plausible solution to it.
>
> Regards,
> Nidhi Maheshwari