Hello Ramiz Raza

In your case, I cannot see a problem with using a 5 µm width and height. I am a little confused of your description of "which is joint between two main channel". Can you provide a diagram to illustrate what you are aiming to produce?

Generally there is a rule of thumb is to avoid structures with an aspect ratio less than 1:10 (height:width). This is to avoid channel collapse. Therefore, if the width of the channel is 100 µm, I would suggest a height of at least 10 µm.

It does depend on the materials and fabircation process though. If you provide more details it will be possible to provide you with a better answer. My suggestion would be to look at SU-8 photoresist. It is very versatile and lends itself to multi-layer processing.

I attach a paper created by the Microfluidics Consortium, providing guidelines for researchers to streamline large-scale production of devices. It is a few years old (2014) but should be a good starting point. It had contributions from Dolomite, IMT, Micronit, EV group and Sony DADC.

Hi Ramiz,

It would be nice if you elaborate your question a little bit. It depends on what material you are using and the fabrication flow that you follow. At this point, it is not clear what exactly is your process.

Jose

Jules Lloyd Hammond Jose Joseph

kindly see attached design - narrow channels is connected or joint between main channel. i am using SU-8 resist.. i want to do 2nd layer lithography of this design . one layer is main channel(height=5um) and other layer is narrow channels(height=5um) . is it possible to fabricate the same height of main channel and narrow channel using 2nd layer lithography ?

I'm confused as to why you would like to use a second layer?

Working under the assumption that the channels are connected and have the same height, it would make sense to pattern them in the same layer of SU-8. (there might be a case specific reason that I'm missing)

If the channels are positioned in the same layer then it's straightforward to pattern both using a single photo-mask with bulk exposure. The height of the channels would then correspond to the height of the SU-8 layer. The same could be achieved by using two masks and performing two exposures but this would just add extra steps.

My apologies if I misinterpreted your goal.

Max Krakers Thanks...you are right

As said by Max, go for one layer, it should not be a problem at all. If you are planning to use mask photolithography, you might want to use a high resolution mask (like chromium).

Good luck

If your final goal is a PDMS channel I would use a single mask with SU-8 2000 series that will allow the dimensions you require. If you are fabricating a channel on the substrate by depositing metals or oxides I would use LOR 5A and S1805 photoresists combination (many published processes online) that are much easier to work with and development takes less time.

The height of the channel is decided by the rpm of your spin coat process and you can find a table that will give you the values for each photoresist in its data sheet.

Ramiz , 5-um is not a big feature size for microchannels with current fabrication technologies. I just not very sure what the channel shape would look like with the multiplayer fabrication and with SU8 whose shape control is not very easy. I introduced a method for multiplayer-channel fabrication years ago, that can precisely controlled channel geometry. See https://iopscience.iop.org/article/10.1088/0957-4484/17/13/018/meta for the publication, then Dr.Albert van den Berg's group provided a more rigorous theoretical analysis regarding this method (https://pubs.rsc.org/en/content/articlelanding/2008/lc/b716382g/unauth#!divAbstract). After many groups' practices, it gradually becomes a standard micro/nano channel fabrication process. Hope it can bring you some convenience to your fabrication. Good luck!

Single layer lithography is sufficient to fabricate the above structure

As long as you are not varying the height of your channel. You are good to go for single step photolithography. Width and length of the feature will be taken care of by mask.