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Microfluidics on the Form3 using clear resin

Does anybody have any suggestions on printing microfluidic chips / components on the Form 3 using clear resin? It seems that the smallest channel I can reliably achieve is a 1.1mm diameter circular channel. This seems fairly large and I think the printer should be able to go smaller. I believe that some resins haven’t quite been fine tuned for the Form 3 - is clear one of them? It seems that maybe the laser output is too powerful for the clear and may be over exposing. Does anybody have suggestions?

Formlabs has a whitepaper on that topic: https://3d.formlabs.com/rs/060-UIG-504/images/WP-EN-Desktop-Millifluidics-With-SLA-3D-Printing.pdf?mkt_tok=eyJpIjoiTkRaaU1EaGpNemhpTUdKbSIsInQiOiJ0XC95bFE3VmU3QzdNeE5BYTNHREQ4VkhEXC9sN3dwdE8rME9FOWpIXC9GMEFQRTk1Zmgxc1NnZzhHM0RtOU9hbkJTN1JFanBBMVNHV3BpRlpBMVwvTTBZTGtHemlyaEZDc3lHWnlqdGJ6QTZKc2lqUEVNdkgrMW90WUtRTERFakExMTUifQ%3D%3D

got that by email some weeks ago…

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Awesome thanks! I’ll start from there

Hello @cerberus20541 did you had any luck in printing smaller channels? I have gone through the Formlabs White paper about microfluidics, but haven’t been able to replicate the results presents there. First I have tried printing 0.4 mm diameter circular channel, but there is no visible channel after printing. In few hours I will have print results of the same model with different channel diameter 0.5, 0.6, 0.8, and 1 mm. Hopefully some of this models will work :slight_smile:

Hi Hepi,

We are still working on it. I have a new employee that is currently tasked with optimizing the parameters so hopefully we can get some results from that. We are testing different channel diameters from 1.3mm to 0.3 and the smallest diameter I can reliably get is 1.1mm. We have an AnyCubic and can get down to 0.7 with the clear resin from them so more than likely we will be using that option. We might also try some of the dental resin but given the cost it seems unlikely at this point. I can buy another Anycubic + 1kg of clear resin for the cost of another tray and resin tank from Formlabs alone…

Yeah, small channels don’t print well in clear on the Form 3, even with 2mm diameter we got clogged up channels when they were sufficiently long.

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Hey @cerberus20541, thanks for reply, much appreciated. Well, another fail regarding the models I mentioned in previous post :frowning: . It seems that there might be some problem with the printer itself since the channel became visually clogged after 20 mm or so. I have printed all the channels vertically and one with 1 mm in diameter is visible open up to middle of the chip, and after that the channel is not so well defined. IMO, another reason of channel clogging may be due viscosity of the resin. I myself also have Anycubic Photon Mono, and I find that this cheap resins are quite less viscose in comparison to Formlabs Clear resin. Therefore easier to push out the residue resin from the channels. Soon I will be getting the Anycubic clear resin, and will try to do my microfluidics in this manner.

Hi @hepi - I agree about the viscosity being thicker but I’m not sure if that is causing issues with flushing. I actually broke a test block in half so I could see the interior of the channels and they were completely solid at the center so the viscosity wasn’t so much of an issue in those cases. The material had cross-linked so it is definitely something to do with being exposed in areas where it shouldn’t be. I suspect the laser is too powerful and is overexposing the clear resin but I have no way of testing this theory since I can’t control the output of the UV laser. I think the DLP system in the AnyCubic probably results in a better result for the clear resins?

Are the sides of the block that your channels are in vertical? Could there be some internal reflections in the block that causes the channels fill in?

Hi @billb,

The channels are oriented perpendicular to the build plane which should result in the best case. I don’t know about the internal reflections though. That is something I hadn’t considered. Since the block is constructed from clear resin, where do you think the internal reflections would come from? From the resin itself? Or from the build plate? If from the build plate I would think only the first few layers would be affected and from what I see it gets worse the deeper the print goes. BTW I have tried attaching the print itself but apparently we are limited to 7MB file uploads…it would be great if we could share directly and others could try the print as well.

Hey @cerberus20541, sorry for not replying sooner. I have managed to print the 650 um-ish microfluidic chip, with 45 degrees angle of print using Beta settings in Preform. Well, I have to note that the channel was designed as 1 mm in diameter. Also, I have tried with designed channel of 800 um, but the print failed with full raft detaching from the build plate.
Still didn’t obtained clear resin to try on my Anycubic. Will give feedback as soon as I manage to print something.
Also, I’m having the same issue as deeper the print goes, since the channels are obviously closing with higher the models are. Didn’t tried yet to print vertical chips, with vertical channels in beta settings, but that may be something that we will need to consider, since beta settings provide better resolutions for smaller dimensions and parts.

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Good day, I managed to print microfluidic channels with the clear resin from about 0.1-0.5mm successfully and reliably. We noticed that orientation is very important. You would want it to be perpendicular to the building platform (so you want the channels to be up straight of the platform). If it’s flat, you won’t get any channels in it. We also notice that if you want other designs, that have multiple orientations with respect to the platform, then channels will collapse on themselves and hence become blocked. The room temperature for some reason also plays a crucial role, as the cooler it is, the more unsuccessful channels you will get. Ideally, you want the room temperture to be between 15-20 degrees celcius.

Hi Nayson - we were good on the orientation but temperature is something I had not considered. The Form heats up the print chamber though, I’m not sure if there is any way to manually control that? Also, the chamber is enclosed when the “door” is down which should prevent any influence from ambient, however, I’ll try some prints at lower ambient temperatures like you have suggested and see if we get any improvements. Thank you!

Yes, there is no way you could control the printing temperature, but as I said, we noticed that if it’s too cold or hot, the majority of our prints fail. Another thing you should consider is that after you are done with the printing and then put it in the bath to remove the excess resin, the next step WHICH IS VERY CRUCIAL is to make sure that your channels are still intact. We usually use a need to blow through the channels so that it removes any access resin or alcohol from the bath. If you cure it by skipping this step, I will guarantee you that all channels with definitely be blocked. So preserve then channels by first blowing wind into them, and then push some excess alcohol through them. Only after you are sure that your channels are okay do you put it in the cure.

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hey guys- i am in the same boat. I can only get down to 0.75mm for a few mm length by temporarily constricting a 1.6mm diameter vertical cylinder on the Form 2. On the Form 3 it wont even come out at all. I thought that the Form 3 was supposed to have better resolution?? sigh…