Arun,

Here are the parameters that I follow for O2 plasma bonding of glass/PDMS:
- 200 mTorr O2
- 400 W plasma
- 15 seconds exposure

I DO NOT clean the PDMS.  It does not seem to matter whether it is fresh or
several months old.

I DO clean the glass slides with methanol.

The two surfaces bond irreversibly within seconds after contact.

It seems that the bonding fails mostly due to over exposure.  Try cutting your
time even more.

Jack Rundel
Ph.D. Candidate
Department of Chemistry
Oregon State University