I've been able to do this in the past.  The trick is to half bake the
slab.  30-40min at 80 C should do the trick.  The slab should be a tad
tacky to the touch.  You might also want to try making the slab with a
slightly higher ratio of curing agent than recommended (e.g. 5:1 instead
of 10:1 polymer to curing agent).  Once the slab is done, pour on your
uncured PDMS and fully cure.  I like to do this overnight (at least
8hrs) just to be sure.

Lee Pang
[email protected]


-----Original Message-----
From: [email protected]
Subject: [mems-talk] PDMS question

I wondering if anyone has had experience with bonding PDMS to PDMS. I
don't
mean bonding two cured slabs using oxygen plasma. I want to take one
slab that
is already cured, and then pour new liquid PDMS on top of it in order to

encapsulate some stuff that I put on the slab.

I tried taking a piece of cured PDMS and pouring new PDMS on top of it
without
involving anything to be encapsulated, just so I could see how the
adhesion was,
and it turned out to be terrible.

If anyone has any suggestions on getting liquid PDMS to bond to cured
PDMS, it
would be greatly appreciated.