You can use methanol to prevent the PDMS sticking during alignment
(there is a paper by David Beebe which uses this method - I can dig out
the full reference if you need it).
I'm not sure about alignment stages though. I would be interested in one
myself if you find anything.
Best regards

Ciro Chiappini wrote:
> Hi and thanks in advance
> I will need to align two PDMS (or other transparent polymer) halves
> with micrometric precision and then make them contact in order to
> bind. at first I was thinking of using the EVG 620 aligner or any
> other photolithography aligner or this purpose, but I'm concerned
> about the clearance since the PDMS mold is much thicker than a wafer
> and once the two halves come in contact they are permanently bound.
> Also I will need to stick one of the halves to a dummy mask in order
> for it to be held in place. Do any of you know about commercially
> available alignment stages for this kind of purposes? I will only need
> an alignment stage, since we already have plenty of microscopes for
> optical visualization.