Hi,

Spin coat a +ve PR of less than 1 micron, before making a spin of SU8. Dont
expose/develop the +ve PR.
Do the process for SU8 and go for optimized developing w.r.t thickness and then
keep the glass slide in petri dish. Then use a pipette for dropping ISO over the
parts very slowly. You need a little patience in this procedure.  I made even 25
sq.micron parts with SU2050 using this procedure.

Kallempudi Sreenivasa Saravan

PhD student, Electronics Engineering,
1054, FENS, Sabanci University,
Orhanli, 34956,
Tuzla, Istanbul, Turkey.


----- Original Message ----
From: "[email protected]" 
To: [email protected]
Sent: Saturday, May 17, 2008 7:00:01 PM
Subject: MEMS-talk Digest, Vol 67, Issue 16

   1. Stiction of SU-8 under water (Evan Shechter)
 Hi,

We have free (released, untethered) blocks that must be free to slide over a
surface.  Currently, the blocks are SU-8, the surface is glass, and they are
immersed in a saline solution.   Typically, the blocks attach themselves to
the glass substrate and become difficult to slide. I am looking for a way to
reduce stiction of this system.  Do you have any suggestions, or experience
with something like this?  Any idea what the predominant force is in a
system such as this?

Some solutions I have in mind are:
1. low-friction coating on substrate.  fluorinated films seem to be helpful
in stiction in air but do they help under water?
2. reduce charge.  if electrostatic charge is the predominant attractive
force, would dissipating the charge help. What is the best way to do this?
3. different materials - while su-8 and glass are currently preferable,
other materials may also be considered
4. ultrasonic stage - i've read that placing the device on an ultrasonic
vibrational platform may reduce stiction, but I've only seen it in reference
to systems in an air medium.

Does anyone have experience with any of the solutions listed above?