3D printed PDMS microfluidics tips and tricks (ESCARGOT)

[@v_saggiomo]

obviously ask here if I forgot something :)

[@sbpark3087]

I am trying to make microfluidic channels using DLP printed resin mold and PDMS. But curing inhibition occured at the interface between resin and PDMS. I have tried several methods such as wahing with isopropanol, UV curing, PVA coating, baking, and surface silanization. But couldn't solve the problem. Can you provide any suggestion to solve this problem? Thank you in advance.

[@v_saggiomo]

hi there (and sorry for the late reply). We used PFOTS (a perfluoro compound) to make the surface of the DLP printed part non reactive. We first was and cure the printed part, then we do plasma for activating the surface and a chemical vapour deposition to cover the part with a silane. The method is described here: pubs.rsc.org/en/content/articlelanding/2020/an/c9an02407g#!divAbstract

[@sbpark3087]

Thank you for your kind reply. i will try that method.

[@kedronox]

Good video! No one in my lab did something like this before, but they've put new project in line which includes different micro fluid channels, now gonna try to make them, thank you!

[@SianaGearz]

You can probably also use HIPS support material for peace of mind. Since it's made to be dissolved (in limonene), you can reasonably expect it to not have another polymer additive; and it will dissolve in acetone just the same.

[@etle113]

Nice trick of using partially cured resin to enable sticking of the next pdms layer. When I can't just use regular O2 plasma or corona discharge to make a solid to solid bonds, I usually let the bottom layer cure completely and treat the surface with Dow corning OS1200 primer before pouring the next layer. This stuff is magical. You can get the PDMS to permanently (i.e. stronger than pdms it self) bond to most treated materials during the cure. Very useful to embed tubing or other structures in the pdms. It is just a bit hard to procure and has a limited shelf life.

[@v_saggiomo]

that's very good to know, for the tubing you insert the tubing first and then cover the connection with the OS1200? need to give a try :)

[@TeotoniodeCarvalho]

This channel is pure gold! Subscribed without thinking twice. Keep up the good work! Greetings from Brazil!

[@jojoflyfffan]

Just stumbled onto this channel and had a quick question. Why did you choose ABS and not a water soluble polymer like PVA? is PDMS compatible with H2O? i assume so right? Also greeting from the netherlands!

[@v_saggiomo]

you're right. It is possible to use PVA and someone did it years after we used ABS/acetone. In 2015, when we did it, PVA was not yet that much available, and very difficult to print. Nowadays it's better. a second point is that ABS/Acetone is faster than PVA/water as acetone is swelling the PDMS just a little bit that favours the dissolution of the ABS. cheers :)

[@YouGenom]

Nice idea to use ABS, I knew it was soluble but didn't expect it to dissolve over 12h in a microfluidic device.

[@v_saggiomo]

it can take waaaaay less if you push it out while dissolving :)

[@YouGenom]

@@v_saggiomo Now I have to buy those sub-millimeter nozzles :D (I meant 0.2mm, which I don't have atm)

[@biosense7714]

Ahhh this channel is AMAZING!

[@loopbeats1861]

Hi thank you for sharing your great technique for that could please share what type of PDMS (I mean viscosity level) and where can I buy it in Europe? Thanks

[@v_saggiomo]

sylgard 184, VWR or Fernell

[@awaisahmadsiddiqi6505]

Thank you so much.

[@Guyuncensored]

can I use pva and water? it can be safer. just need humidity levels control.

[@v_saggiomo]

yes but it will take ages to dissolve

[@dahoumaria263]

the explication is freeking good thank youvery much hope you have a nice day

[@정성수분석화학전공한]

I also wanted to do research on microfluidics in our lab, so I referred to your videos and papers. However, the abs we bought didn't melt even after putting them in acetone for over a day. It was similar with a syringe. I think maybe there is problem with abs. Could you tell me the company name and product name of the abs you used?

[@v_saggiomo]

we use various brands, most of them made in NL (like real filament, or Jupiter filament). Just buy the cheapest ABS you can find, or if the design is not that difficult, you can try to print in PVA and dissolve it in water.

[@Andreas-gh6is]

Have you used microfluidics produced with this method for something practical?

[@v_saggiomo]

we've used for making 1 euro NMR coil for detecting pico moles of materials www.nature.com/articles/s41467-017-02575-0 (a coil around a micro channel is practically impossible to do with any other methodology) but also, if you check who cited this paper, you can see how many people without experience in microfabrication used this method for making various microfluidic devices :)

[@Matlock24]

Have you ever managed to do this technique using 3d printed parts from a form labs SLA or Polyjet printer?

[@v_saggiomo]

well, yes and no. Resin are cross linked polymers while FDM are thermoplastic, this means that for the resin (usually acrylate based) you need to break covalent bonds. So it works but with harsh chemicals (sulphuric acid for example), not really nice to handle.

[@lamiaaj2456]

what is the reference of these flat sheet of ABS please! Thank you so much

[@v_saggiomo]

the one I use are from here: modelshop.co.uk/Shop/Item/ABS-sheet-175-307mm/ITM6961

[@rock3tcatU233]

Great tips, but doesn't microfluidics require sub-100 micron channels?

[@v_saggiomo]

not really, as long as you can use microliters.... :)

[@app134]

Sub 1000um

[@katerinasaiti9572]

Which is the smallest diameter you can design for a channel?

[@v_saggiomo]

depends on the nozzle of the printer (400um the standard, 250um doable, 100um very difficult)

[@katerinasaiti9572]

@@v_saggiomo one more question! With this methodology, if I mixture oil and water phases (with T formation), which is the smallest size of droplet, I can have? It depends only on the flow rate?

[@v_saggiomo]

@@katerinasaiti9572 very difficult to say. It depends MOSTLY from the flow and the geometry (T shape versus Flow focus droplet formation). My guess would be 50-100um. here we did something similar twitter.com/V_Saggiomo/status/1400722212185948161

[@Gelatinousblob33]

where did you get the curing agent?

[@v_saggiomo]

it comes with the PDMS (sylgard 184)

[@sakjietan4685]

Any recommend method to combine pdms to pdms together ?

[@v_saggiomo]

if the pdms is already cure, then just plasma oven, otherwise they will not stick into each other. If not fully cured they will just stick together.

[@Guyuncensored]

if its half cured. its easier if you make one part lean on hardener and the other part rich. 5:1 and the other one 20:1.