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I wondered how the lateral flow tests strips worked, so after doing a test with one I took it apart. The deceptively simple interior hides quite complex molecular science. I'm not a molecular biologist, so I've kept the description of operation simple. There are versions of these strips that can do multiple tests simultaneously, and also versions that are read optically to give a more analogue reading. (The blood analysis uses the blood-plasma for the test.) If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- http://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty. #ElectronicsCreators

I was feeling a bit under the weather, and i thought, let's give myself one of these lateral flow covered tests, just to confirm that i've not somehow picked up covert, even though i am vaccinated, it came back negative such to come regarding cold. However, i thought that these were quite interesting, so i've found out how they work and i'm going to explain how they work. Now, i'm also going to explain how the test is done so to do the test. You get these little dropper bottles and you get a carrier solution here.

You snap this off and you pour the small quantity of carrier solution into this bottle. You then - and this is absolutely the worst bit you get this little cotton tipped swab and you have to stick it into the back of your throat sad throat, that's a tonsil area, i i don't have tonsils, don't know or or that area, and then you rub It around neither side, that's when you gag it just about made me throw up. Then you stick this up your nose and you twirl it round and run the nostrils, but you have to push it right far to the back and you'll, probably sneeze as well. It's very intrusive once you've got your sample of stuff, you place it into that liquid and you press it around to really mix in with that liquid and then once you've done that for about 15 seconds, you squeeze this little plastic tube, and then you drag it Out so it squeezes it off the pad, and you end up with as much of a concentrated dose in there as possible.

I'm keeping this plan, i'm not going to contaminate it, because i i want to keep that test. Then you pop this lid in and you have a little squeezy dropper bottle. Quite clever. You put a couple of drops into this reservoir here and it starts the process of wicking along inside and after about 30 minutes uh, you will have a indication either.

Just the c, a line will appear or t for a positive conformation and the c, which is the confirmation line. But let's take a look inside this bit and see how it does that clue. It's incredibly clever, but strangely simple as well and there's a lot of connections with pregnancy tests are doing the same for a hormone. She popped the lid off.

Let me zoom down in this and just show you actually you know i've taken a picture. I could show you, but i shall zoom down. I shall zoom down and show you what's in here in fact i'll just zoom right up to here, so you can actually see the real thing in a closer vicinity. So here's a pad that takes the liquid.

It soaks along and then it goes to this waste pad here right. Tell you what let's uh, bring a picture and i'll show you the whole process here so inside is this wicking pad and it's formed of multiple materials, multiple layers with chemical, impregnations and parts of it. When you put the carrier liquid in with the potential virus, it lands in this area and absorbs into this large area wicking pad, which is quite thick, and then it starts wicking along this, a blotting paper up to the other end as it does so, it passes Through this zone, when it passes through this zone, it has sort of molecular keys with dye on them and by dye, i'm i'm actually talking like gold molecules. It's a tiny, tiny, infinitively small amount gold, but enough to create this of the red lines that are seen so as it passes through.

If there are the virus particles it latches onto them, with that marker dye, it then continues up through two areas which has mil which have molecular keys. The first area is the test area, and if the molecules do have the virus, then the virus is trapped onto these little test keys and it makes the die visible. At that point, it causes a concentration of the die. It then continues up and there's another set of keys that will just generically latch onto everything and else as it passes, and the whole point of that is to show that the whole process has happened properly, that the chemicals were right and that the whole process did Go through this zone to actually display the test.

The liquid then continues into this pad, and that is just basically the waste pad where it just collects all the residue, and that's fundamentally it just for the fact that these antibodies this these little keys that latch onto that signature will make the line visible. That is fundamentally how the test works. It's very clever, very strong hints of the blotting paper, the sort of the filter paper chromatography. If you remember getting that at school, i don't know if they still even do that anymore, but they've got other versions of these.

That can do multiple tests at once, so you can actually have a whole load of lines that has a liquid pass. That will run a whole load of tests and it's not just things like it's, not just that sort of mucol stuff in the carrier liquid. You can use urine in them. You can also uh extract the when they put blood through it.

They separate the red cells from the white cells, so the actual just the white cells, the color, doesn't interfere with it and that can also be used in similar stuff. Like this, it's very clever, very neat, and you think you know it's so simple, but in reality that simplicity underlies the fact that the scientists have engineered these molecules to lock on to a particular keyed signature of the virus. It makes it very clever. So if you're wondering how these little tests work, that is how they work.

It just seems so simple just that liquid flowing along blotting paper, but the science behind it is incredibly sophisticated and very impressive.

17 thoughts on “How a lateral flow test strip works (kept simple)”
  1. Avataaar/Circle Created with python_avatars Glynn Cleaver says:

    We have something similar in beekeeping for testing for American foulbood a bacteria infection that kills bees. Thank you for showing how they work

  2. Avataaar/Circle Created with python_avatars CheadleBiker says:

    You can still get covid when you're vaccinated. I did 10 consecutive days of positive results with those, 2 months after my second Ox-AZ.

  3. Avataaar/Circle Created with python_avatars Steve Mitchell says:

    Shows the process but not how it works, i.e how it can detect a dead virus molecule and identify it as a certain strain, hard enough for a lab to clarify.

  4. Avataaar/Circle Created with python_avatars China North Airguns says:

    Funny how you need to shove the sample wand up into your brain, but it's so contagious you need to stay 6 feet away and cover your face, unless you are a politician at cop26.

  5. Avataaar/Circle Created with python_avatars stuart liddle says:

    Brilliant explanation, they should definitely be left for the full passage of time and be sure to allow your juices to ferment in the liquid for best results.

  6. Avataaar/Circle Created with python_avatars Richard Smith says:

    gold nanoparticles, to be specific. Which is a ruby red color(if very small). Purplish blue if on the larger side.

  7. Avataaar/Circle Created with python_avatars Sean Redmond says:

    Thats the older revision test, in the new one the carrier solution is already in the bottle, with foil lid 🙂

  8. Avataaar/Circle Created with python_avatars Jason williams says:

    You actually showed using the test BETTER than the muppets i have seen using them that have been trained in their use.
    Good job.

  9. Avataaar/Circle Created with python_avatars D S says:

    Hope your cold is better. I like that you chose to post this in the same week that I used one… Only mine had two lines.

  10. Avataaar/Circle Created with python_avatars karel degreef says:

    You can not be vaccinated => it's an experimental Gen therapie 😉
    you are either wackcinated , sorry but that's the truth 😮

  11. Avataaar/Circle Created with python_avatars Sixteen Cats in a trench coat. says:

    I absolutely hate doing the swab bit, I’ve done 4 or 5 of those test, I don’t mind doing it though, I think it’s incredibly cool that we have them and the vaccines and all the rest.

  12. Avataaar/Circle Created with python_avatars D W says:

    I've been binge watching your channel for a few days now. I loved your LED bulb series and your powerbank videos. I bought a pair of LED bulbs and took them apart last night and figured out how it works from your videos and using a continuity tester to verify what parts are connected. Turns out I have one of the "two resistors in parallel" bulbs so I can clip one and lower the power so it lasts longer.

    Cheers buddy from Canada!

  13. Avataaar/Circle Created with python_avatars Tech Gorilla says:

    Would you like me to send you a strip that I use to test my INR readings at home? They're quite sophisticated.

  14. Avataaar/Circle Created with python_avatars Jonathan Pearce says:

    The new tests issued by UK gov are nasal only, no throat swab needed. Currently testing daily for work, which is fun…

  15. Avataaar/Circle Created with python_avatars Mark Ingram says:

    I think the 'C' might stand for "Control" instead of "confirmation", but I could be mistaken

  16. Avataaar/Circle Created with python_avatars Goofy Brained says:

    Also that those 'molecular keys' are specific enough that they can tell SARS-CoV-2 from other 'common cold' virus – even in mixed company

  17. Avataaar/Circle Created with python_avatars Peter Stevens says:

    You should checkout the electronic covid tests kits, the electronics are totally unnecessary, but possibly hackable? the ones I've head of use a 32bit mcu

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