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SL1S for microfluidics prototypes?  

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MikeH
(@mikeh-2)
Trusted Member
SL1S for microfluidics prototypes?

Has anyone used the SL1S to make microfluidics devices?  Ideally, this would involve creating plates with small embedded hollow tubes along the length of the device and connections at the surface to allow for fluid injection and recovery.  Something like this:

https://www.dantecdynamics.com/solutions-applications/applications/microfluidics/

Posted : 05/01/2022 10:24 pm
Reid
 Reid
(@reid)
New Member
RE: SL1S for microfluidics prototypes?

It depends on what you're printing. The SL1S has a XY resolution of 47? microns and a Z resolution of ~10 microns, with a recommended layer height of 25microns. 

If your channels are larger then that range, then sure it can be useful. If you require pretty accurate channels, or rounded channels, then this can throw some wrenches into that due to the layer "stepping" that occurs. I've printed off some parts off a Form3 (more 'accurate' but much slower) and had them measured with a profilometer and the results weren't.....amazing. Granted, I was printing things off with channel sizes around ~30 microns, so it was on the knife's edge of its capabilities. 

However, the SL1S worked well for relatively large (100um+) channels, just be sure to clear them WELL before curing and thoroughly dry those channels. We blast IPA followed by compressed air to clear the channels, because any residual resin/IPA can block your channels. 

Posted : 10/01/2022 5:18 pm
MikeH
(@mikeh-2)
Trusted Member
Topic starter answered:
RE: SL1S for microfluidics prototypes?

Thanks for the reply.  The immediate project is for a 300 µ diameter "tube" embedded within a flat plate and the tube is 300 mm long.  Aside from the SL1S work envelope being too small for the part length, my suspicion is that the tube walls will most likely collapse in on themselves or just get plugged with liquid resin that will be next to impossible to flush out of the part before the part can be cured.  Does that sound like a logical conclusion?

 

Posted : 10/01/2022 11:15 pm
Reid
 Reid
(@reid)
New Member
RE: SL1S for microfluidics prototypes?

I didn't see a mention about the wall thickness, but I haven't had parts "collapse" on me with any of the resins that I've tried on the Form or even in DLP/MSLA prints. If anything, they may be mildly flexible or slightly brittle, but not the sort of collapsing that I'd think of with, say, a really soggy noodle. I have printed capillary mounts that are around....150um? in diameter if I remember correctly, and while those had a tendency to get clogged with resin during curing, it was avoidable with the appropriate flushing and drying as I had mentioned earlier. 

Posted : 10/01/2022 11:24 pm
MikeH
(@mikeh-2)
Trusted Member
Topic starter answered:
RE: SL1S for microfluidics prototypes?

Sorry, collapse was a poor choice of wording. I meant that residual liquid resin in a long hollow, horizontal tube could be difficult to remove before it gets cured.  If the undrained resin cures, it could partially or completely block the tube. 

The requirement for a 300 µ hollow tube made by a laser with 45 µ X/Y pixel seems like a non-starter to me but it would be nice to get confirmation from someone that has tried it.

Posted : 11/01/2022 6:31 pm
Reid
 Reid
(@reid)
New Member
RE: SL1S for microfluidics prototypes?

Circular features are already a non-starter and typically why SLA, with a directed laser dot, is preferred for those applications. We exclusively use a Form3 for circular features that are critical to be relatively circular. You get into issues if that tube makes an elbow as you then deal with the Z-stepping appearing, but that is a feature inherent of any FDM process.

Hollow tubes and residual resin, as I had mentioned before twice, can be cleared with pressurized IPA (aka a squeeze bottle) and compressed air. My process has been to let parts wash immersed in a bath, followed by light drying (shake/hang to dry for a few minutes), followed by a quick pressurization till I see liquid flowing out of the end of the tube. Repeat with air to clear the channel. Obviously easier to diagnose with a clear resin. 

Posted : 11/01/2022 6:40 pm
MikeH
(@mikeh-2)
Trusted Member
Topic starter answered:
RE: SL1S for microfluidics prototypes?

Thanks Reid - not sure how I missed your earlier comments about flushing the enclosed cavities but that makes sense.  I'd originally looked at FormLabs for this a couple years ago but there didn't seem to be a lot of interest in the subject from that community and even FormLabs themselves couldn't provide much info.

I think I see your point on SLA vs MSLA, but as I understand it, the SL1S produces ~45x45 µ cured square feature whereas the Form 3 produces an ~85 µ cured circular feature and they both have similar cured layer heights.  Depending on the application, I suppose that one system might have an advantage over the other.

Posted : 13/01/2022 8:40 pm
Reid
 Reid
(@reid)
New Member
RE: SL1S for microfluidics prototypes?

Not sure where you got the 85um circular feature - I believe that's just the laser spot size. In any case, I am willing to print out a test print (no charge; I'm curious too) for you to see if the Form or SL1S is a viable alternative - I'm assuming the latter isn't, and I'm still waiting for mine to be delivered anyway. Let me know if you are interested. 

Posted : 13/01/2022 10:13 pm
MikeH
(@mikeh-2)
Trusted Member
Topic starter answered:
RE: SL1S for microfluidics prototypes?

I was thinking that the 85µ FL3 laser spot size would have some bearing on the printed feature dimensions and that influence might be different the 45µ pixel size with the SL1S.  It occurs to me (now) that the X/Y resolution of each device is also different and that might be more important.  As I understand it the SL1S can lay down "pixels" along X and Y in 45µ increments, that is two "pixels" can be separated nu 45, 90, 135µ, etc. whereas I think that the FL3 X/Y resolution is much less, perhaps < 10 µ?

Thanks for offering to print a sample.  We've decided to go a different way on the original project, but there may be different applications coming down the road.  I can send you a small sample file if you are still interested.  Just let me know where to send it and what file type you want.  I would be doing the CAD in either Alibre or Onshape and both of those can generate a few neutral CAD formats as well as STL.

Posted : 13/01/2022 10:51 pm
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