There are better chemical than HMDS and TCMS.  For release agents you
are looking for the highest achievable water contact angle.  Teflon has
13 fluorine molecules facing out and a contact angle of 120 degrees.
With a heptadecafluoride there are 17 fluorine molecules facing out and
a contact angle of 130 degrees.  Good news but the real secret is to
totally dehydrate before the chemical sees the mold.  If it sees
moisture it reacts with the moisture but breaks free later when it sees
moist room air.  This gives erratic surface tension modification.  How
big are your molds?  Bill

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Shao Guocheng
Sent: Tuesday, August 11, 2009 7:37 PM
To: General MEMS discussion
Subject: HDMS treatment of SU8 mold used for PDMS thin film fabrication

Hi, Bill,

    thx for the reply. sorry, I do actually mean HMDS. I want to
silanize the mold so it will be easier to release PDMS film from the SU8
mold.   I know people usually use TMCS. But heard some people say HMDS
can work as well.   How long do I need to do the treatment if put couple
drops of HMDS along with my SU8 mold into a evacuated dessicator?.  thx


Shao