Hi,

I am trying to fabricate a device with 2 layer of SU8.
The first layer is just a simple straight microfluidic channel which is
around 200 um wide.

I am planning on fabricate a second layer of SU8 on the top of the
microchannel with a series of blocks along the length of the microchannel.
The second lyaer of SU8 needs to be really thick since the PDMS thickness is
going to be in between the first layer and the second layer,
so that I will have holes within the microchannel.

My question is that what might be the better process to process the second
layer of SU8?

Should I spin-coated and expose the first layer following a second layer
spin-coated and exposure and develop the whole wafer all at once,
or should I spin-coated, expose and develop the first layer and process the
second layer afterwards?

Any suggestion and opinions would be greatly appreciated.

Thanks a lot!

Jean