Hmm.  That could be problematic when approached simply from a chemical point of
view.  The problem is, as far as the developer transport is concerned, you are
developing a feature with an aspect ratio of ~600:1 (12000 µm:20µm).  This makes
a very long line for the dissolved SU-8 to diffuse.

To think outside the box, perhaps you could heat the substrate up to ~100ºC, and
apply pressure to one of the ports.  Un-crosslinked SU-8 has a glass transition
temperature of 55ºC, so by 100ºC, it should have some definite flowability.
Maybe by pressurizing the port (or perhaps, applying solvent under pressure?),
you may be able to push the material out. (just brainstorming here - no idea of
feasibility at all, but it seems as likely as trying to develop it out).

As an alternative, you could try to pattern the material prior to bonding.  This
presents difficulties of its own, however, since fully crosslinked SU-8 is
extremely difficult to bond.

Best Regards,
Chad Brubaker

EV Group       invent * innovate * implement
Technology - Tel:  480.727.9635, Fax:  480.727.9700  e-mail:
c.brubaker@EVGroup.com, www.EVGroup.com

-----Original Message-----
From: prabhu arumugam
Sent: Monday, August 14, 2006 11:35 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] Developing S8 channels through reservoir ports

Dear SU 8 experts,

I am trying to develop a 20 micron high SU8 channel
(1.2 cm long) bonded between glass and silicon through
the fluidic ports at either end of the channel. I am
not able to develop the channel fully. I exposed for
20 s and developed in an ultrasonic bath.  Could
anyone share their experience/tricks/tips in solving
this.