Microfluidics Interviews #2: Paper-based microfluidics 

Hi there! Two things: 1. English subtitles are available in the settings menu of this video. Click "CC" to the left of the gear icon on the lower right of your RU-vid player. 2. This video was shot in the spring of 2016, and constitutes the end of our series on microfluidics. You can learn more about what Laura was up to in the years before and after we shot this video in the description. Her PhD studies laid the groundwork for the rapid development in 2020 of COVID-19 diagnostic kits using paper-based microfluidics: www.espci.psl.eu/en/news/2020/a-new-generation-of-molecular-testing-for-covid-19. Enjoy!

Excellent work! The Lutetium project has done an excellent job of showcasing modern research in an elegant and approachable method. I look forward to the upcoming work!

Amazing! I thought that the folded wax paper microfluidic devices were excellent, but the other things mentioned, such as using a smartphone for electrophoresis and diagnostics is even more exciting. Excellent work! I hope we can see more of this technology being used in the near future.

Amazing! Great stuff, it blows my mind. Thanks a lot!

The work seems very amazing. Keep exploring

Speechless 🙊

Very interesting for sure! I wonder how these mixed paper+electrical microfluidic circuits look. For example, is there a way to make a small valve? That would give a bit more control to, say, let a reaction sit for a while in a small reservoir before continuing through another chamber, or to let reactions take place at specific timesteps. Oh, and of course if there are plans to have an on-paper PCR? In theory, with a phone-based heating element and the right materials (even including the gel strip with electrodes, if it can be added to the paper), it sounds doable, and could be very exciting!

Very exciting work. Can you help connect with the lab

It was an extremely informative video, Thank you so much. well I wish to know what paper did she used tp make those ?

Hi, this video is quite informative and very interesting. is it possible to know the brand of ink that Laura used? Thank you

She claims to not need other equipment besides a modified phone type device, but literally in her paper it requires a suitcase that has a heater (probably a cold compartment too) and an "optical system of detection". This is nothing new, and we certainly have the same tests in the same or smaller size factor (putting shit in a suitcase) She probably means to replace the suitcase with the phone device, but again this is certainly something that's already done (piezoelectric plates and a single UV LED)

As a pre-med student these seem very impractical and short sighted, possibly even idiotic Clearly the only tests that can be done are qualitative (positive/negative/control) Doing a single test on one layer makes sense, because it is simply one layer, but the reason there are not significantly more of these types of tests is imo stability and accuracy How do they stop the paper from filtering nearly everything not dissolved directly in the liquid. Say you wanted to test urine with multiple assays, how would you be able to test protein levels, salt, and glucose. The protein would stay on the top layer/input hole and can only move on the surface level, while the sugar is incorporated into the paper (as cellulose is a sugar they will "stick" together), and the salt is diluted throughout the paper as it absorbs the water; and looking it up it seems celluloses charge causes pockets of charge (not uniform) along with sometimes seeming to prefer one ion over another. There doesn't seem to be any way to avoid these pockets due to how it's processed. These unpredictable and unavoidable pockets would make it impossible to accurately determine ionconcentrations, or anything else with charge as well. Leaving an insane amount of room for false negatives, especially from all this hugely variable saturations Also, nucleic acids are famously unstable (especially at room/surrounding environment temp) and are often very messy when it comes to binding (which your cells fix them all the time by having tons of them, and multiple ways of detecting when they aren't binding as they ought to, and also multiple ways of either correcting it or simply decoupling them). How is it possible to prevent, or even better, correct missbound sites. How do you prevent false positives, especially if it happens to be an especially "sticky" acid There is no "logistical" way I can see where you can ship these without destroying it in the process, as well as contamination being very likely (likely that random bits from organisms will find there way to the testing site because that's just field work)... false positives for days And one of the biggest problems I see is temperature, in the field it's usually difficult to keep things at the temp they need (most being below room temp, or at body temp). You wouldn't be able to do tests at higher temps (PCR is good example @Xasin) as the wax would melt again and contaminate everything. And if you're bringing equipment to control temp, then it is simple enough to bring most everything else, as they usually come hand in hand for field testing They only viable way I can see this actually panning out, is how it already has. Which is use highly stable compounds (say antibodies) that then react to release a dye or become fluorescent. And again the ones that already exit (not just pregnancy but drug tests too, and ) are generally just good enough for the most simple of tasks. Trying to make it more complicated seems like nothing but adding more failure points for a very small gain of yes or no. Especially if your trying to detect with things that have an extremely variable response, such as testing immunocytes or nucleic acids TLDR: i don't see how this is better than what we have. The only way this is feasible (IMO) is by doing what has already been done, and anything more is just not reliable in any meaningful way. But I am just a pre-med, so if she and her team have figured out how to overcome all of these things (and likely significantly more) then good on her. I am very cynical on this, but I would love to hear how any of this can be done, both easily and on the cheap since that's the entire point