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?