Hi

I think the PDMS is not sticking on SU8 - if you look on some paper
from G Whiteside (the "father" of PDMS) and Duffy you can read is not
sticking on some organic stuff. Usualy you need some oxygen  bonds on
the surface . Thoese are activated during Palsma Oxygen

Good luck
Petru

On Tue, Mar 18, 2008 at 1:45 PM, Steven Yang  wrote:
> My microfluidic pattern is made of SU-8 on the Si substrate. I tried
>  to seal the pattern with a piece of PDMS. The PDMS is Oxygen plasma
>  treated at 20W for 20s to achieve a hydrophlic surface toward the
>  pattern. and SU-8 pattern also oxygen plasma treated under 100W for 1
>  minute after its hardbake at 150C. After that, two sides was contact
>  and hot press at 100C for 2 hours in a vaccum oven.
>
>  However, the bonding did not succeed. The problem probably comes from
>  that the PDMS did not show the adhesive property to SU-8 once they
>  were contacted. Actually, the PDMS is always show a "stick on" effect
>  when it is contacted to other materials, such as glass dish, or Si
>  substrate, even after the oxygen plasma treatment. But when it contact
>  to my SU-8 pattern surface, the effect did not show up. I read a lot
>  of work doing SU-8 and PDMS bonding with Oxygen treatment, but why does my
>  work turns out that the PDMS seems does not have the possibility to be
>  bonded on it?