Hello Liang,

I think Gareth is right, it looks like a lot of thickness (50um) and too much
short development time, especially if you take into account the sieves
dimensions (around 20um). It will be difficult develop the unsposed parts... or
perhaps impossible at all: You have light scattering so it is possible that at
any depth some photons are reaching the SU-8 under de sieve mask, so could be
polymerised and so it will very difficult develop it.

I really don´t understand exactly your channel-sieve sistem, especially the arc-
sieve geometry, but looks like something like a block with "holes" with arc
shape. You want the SU-8 just as a mould to get the chanel with "walls" with arc
shape in PDMS. You can´t get holes from one side to other in su-8, so your
walls in PDMS are not so high as you want, and cells flow away freely, isn´t
it?Well, why not make the channel directly in SU-8? The only thing you will need
is invert the mask, leaving the sives clear and the channel dark. I hope this
idea works well for you.

regards

Eowin

--- Den ons 2008-10-29 skrev Liang Zhao :
Från: Liang Zhao 
Ämne: Re: [mems-talk] SU-8 microfabrication problem
Till: "General MEMS discussion" 
Datum: onsdag 29 oktober 2008 11.00

thanks,
The channel was transparent and patterns of seives was opaque arcs which
located in the channel. That is to say, by using SU-8, the channel patterns
was a positive mold and with a very small holes (the seives). Our obstacle
was how to make the holes thoughly from top to bottom? The unefficient
development or unefficient exposure? I am not sure if I explain it clear.
Now, we still working on it. We tried different exposure time but cannot
solve such a problem.
the exposure dosage we tried was: 400mJ/cm2, 200mJ/cm2, 100mJ/cm2, 50mJ/cm2,
but no one works. could any one help me? Thanks.