Hi All,
I am currently working on SU-8 microfabrication. My propose is fabricating a
PDMS seive for immobilizing cells by using SU-8 mold. We designed a
microchannel with a seive pattern that consist of 3 short arc, gap between
them is 8 μm, middle arc is 20μm in width and 80μm in length and the two
short arcs located in each sides of the middle arc with much smaller size in
length. we do microfabrication with SU-8 2050, and we hope that we could get
a PDMS channel with a hight of 50μm. Unfortunately, during our fabrication
process we find that it's hard to get a sieve pattern that thoughly from top
to bottom. By using this SU-8 mold we cannot immoblize the cells, because
the PDMS sieve doesnot touched the bottom that all cells just flows away.
We basically attribrite this phenomena to an unefficient development, but
things does not work when we prolong the develop time. Could any one give me
some advice? thanks.

PS: our procedurs are as follows:

・         Spin PR (SU8 2050): 500rpm 15s and 3000 rpm 40s (expected PR film
thickness 50μm)
・         Soft bake: 65C / 5min, 95C / 15 min
・         Expose: 15 seconds or 10 seconds
・         Post Expose bake (PEB): 65C / 5min, 95C / 15 min
・         Development: 3~4 min with agitation in SU-8 developer
 .       Hard bake (Cure): 200C in 20 mins

lowing the temprature slowly after each baking step.

--
Liang Zhao
School of Chemistry and Chemical Engineering, Nanjing University