I did this recently by exposing the PDMS to plasma at 150W for 1.5-2minutes and
got a  rock solid seal. The only thing to beware of is in my case I wanted to
develop out the SU8 that was left in the channel so that my channel had PDMS on
3 sides and glass on the other. So I exposed the SU8 with my mask and left it in
developer for about 20 min. Well this caused the PDMS completely shrivel up and
peel off the glass. So if you want to develop out any SU8 left in there, you
need to pump the developer in and wash it out quickly.

-Joe Grogan

Quoting Jiang Ziling :

>   Does anyone have experience bonding Su-8 with PDMS? I need to know
> the parameter of oxygen plasma treatment to PDMS before bonding.