Worlds Smallest Tesla Valve? - Shrinky Dink (Shrink Film) Microfluidics

if you ask someone to explain how a computer works from the ground up their answer will probably start something along the lines of well a computer is a device that can do math and it's based around transistors to understand transistors imagine a tiny water valve that you can turn on and off if you chain these valves together in the right way you can make logic gates and then from there you can do computation now picture this conversation happening between two people but the one having it explained to them wasn't quite paying attention but had to give a presentation about it on Monday to a bunch of engineers so monday arrives they show up in their boss goes well Gary what are we building to which he replies well we're gonna build a series of tiny valves they can do math and everyone just went well ok then and got to work this is basically how I imagined the field of microfluidic starting as you probably guessed from the title today we're talking about micro fluidics but just like asking what are all the things you can do with a computer attempting to cover the whole field of micro fluidics in one video would be insane so let's just start with the basics microfluidics is the study and creation of devices that use tiny fluid channels to accomplish an incredible array of tasks and like computers you can fill them full of tiny valves that just like transistors can be used to actually do math and form logic gates and such but that's considerably more complicated than what we're going to be working on today for this first video we're just gonna be focusing on designs that use the shape size and arrangement of solid channels to accomplish different tasks for mixing to sorting to give you an idea of the possibilities one of the hardest parts of micro fluidics is making the actual flow cells themselves designing them is fairly easy and can even be fairly intuitive but taking a design and carving it into some block of material at the scale that flow cells typically operate is normally an expensive undertaking requiring specialized equipment and weird expensive materials consider that the channels in many of the images i've shown our fraction of the width of a human hair some only a few micrometers wide so the question remains well then how would you average people ever get a chance to explore this amazing field and reap the many benefits of incorporating micro fluidics into your projects well it really depends what your application is very simple micro fluidics can be made using nothing but paper and crayons drawing an outline of a design on some paper is enough to make a pseudo channel such that when you put a drop of water in one of the it'll wick down the paper channel without bleeding into the surrounding paper or you can use masking tape to make very reasonable but simple designs here's a simple one I made with some yeast cells flowing through it the channels are made by a gap between two pieces of masking tape and sealed with another piece on top but these methods kind of suck decent for simple Diagnostics but nothing compared to the actual utility of a flow cell that you can attach several tanks of liquid to and have fluid flowing through it doing chemistry keeping cells alive running tests or anything else you could want for potentially hours on end for that we'll need something which is normally sold as a children's toy and costs almost nothing this is shrink film also known as shrinky dinks the idea is that it's a sheet of polystyrene which is pre stretched as they made it so normally you draw on the rough surface of the sheet with pencil crayons or your medium of choice then bake the sheets and as they heat up and melt will contract thicken and Harden ending up about 1/5 of the original size a pack of 6 sheets of this stuff costs all of 7 Canadian buckles which is enough to make a couple dozen flow cells at least the first paper that I found that uses this material used a standard printer to print designs onto the film shrink it and then use the raised ink as a negative mold to make the actual flow cells using PDMS a type of clear castable silicon but a later paper by the same group forgoes the PDMS and just carve their design into the plastic itself in the paper they use knives and similar cutting tools to scribe their designs into the plastic this is great for giving very thin channels but the issue is that it doesn't quite give as much flexibility and design choice and they made their designs by hand I chose to go a different route and went with CNC milling my designs in the plastic using the tip of a V cutter this gives way more control and lets you do far more complex designs though there are a few tricks to actually make this work first the bed of the CNC cutter must be as flat as physically possible and since the film naturally wants to curl a lot of tape needs to be used to pull the sheet tight and flatten it to the bed also make sure the rough surface of the plastic is the one you're cutting into next is that we don't want to cut through the plastic in fact we barely want to cut it at all as the parts are baked and shrink any detail we carve into the surface will shrink in the X and y direction but will become much thicker in the Z direction so a shallow wide groove a deep thin trench after heating okay let's cut some designs as usual with my particular setup I made my designs in Inkscape and used an online tool called Jas cut to generate the g-code to run the CNC cutter I've put a link to all the SVG files I've used in the description if you'd like to use the designs I made but you'll need to generate your own g code to match your machine the actual milling is pretty straightforward the sheets are about 2.8 millimeters thick and I only take a single 1.5 millimeter deep cut however because PVC has a habit of being a bit melty sometimes or even often the designs aren't perfect after the first pass so once a whole design is finished cutting without moving anything I run the program a second time this clears away any rough bits of plastic that might be left over once that's done the designs can be untaped and prepped for shrinking and assembly before we go further there's still a bit of debris in the channel and literally anything left in there will end up clogging the final cells so manually pick out any large debris and then using a bit of acetone on a swab a very quick gentle pass removes any powdered plastic and clears the channels don't use a soaking wet swab it only needs the slightest hint of acetone on it anymore and you'll seriously damage the plastic and have to start all over before we can do any shrinking we need to make the top plates for all of the flow cells I cut pieces to match the designs out of scrap material from previous runs and drilled four to five millimeter holes to match the lower design as you do this make sure the rough faces of the plastic are facing each other but once that's done it's finally shrinking time I found the best way to do this was in a toaster oven that was preheated to 3 2015 model tray pre warming in the oven you'll want to start with a few test pieces first before you use your actual designs just to make sure that things are at the right temp then just pop the designs onto the tray close the oven and watch the magic happen the shrinking can be a bit chaotic but don't panic given a bit of time it usually evens out though sometimes it may need a gentle nudge once everything is shrunken you can take them out and gently flatten them if necessary while still warm let them cool enough that you can touch them then stack and align the halves and pop them back into the oven this is the hardest part of this process and getting the two halves to stick is like the most frustrating game of chicken if you wait too long everything melts and is ruined but if you don't wait long enough they won't stick properly so it can take several attempts luckily if you're careful not to squish your designs if a bond fails you can just try again in either case when you think you're ready quickly take the tray out of the oven and use a flat bit of metal to very gently press the two halves together once it starts to firm up remove the metal or it'll cool the half it's touching too quickly making the pair crack back apart also don't push too hard or you swish your design and plug one or more of the channels one quick note is that you don't need to limit yourself to just two layers if you're feeling adventurous you can do more layers and do it as high as you like in theory I just didn't bother for this video but when everything goes just perfectly you end up with these amazing little flow cells with perfect channels at a fraction of the size that would otherwise be possible with just a CNC machine the smallest channels I've made are less than 100 microns in diameter before we can test these we need to add some plumbing I'm using this one millimeter Teflon tubing that we just happen to find but really any small tubing should be fine I like this stuff because even if it's too big a bit of heating you can stretch and shrink the diameter for a perfect fit for now I'm using hot glue to seal these as I'm not doing anything more delicate yet but that's not really a great method for this to get fluid into the tubes I use a needle with a sharp point cutoff which is then inserted into the tubing and glued to seal it okay let's fire these up first a simple mixer the idea here is that you put two different fluids in one end and you get a mixed fluid as the output here's the first test running it reversed to save on plumbing you can see everything flowing beautifully now running it properly I've got yellow and blue dye connected to the input and I'm using suction on the output to pull the two fluids through at the same time evenly as you can see once the fluids mixed we get a nice green output this next design I actually made too small to save on CNC time but it's meant to be a lot larger there are two inputs and two outputs but for the first test I only plumbed up a single input the idea is that you're meant to flow saline through the bigger input and put a blood sample in the smaller input the blood gets carried around the spiral and as it flows it tends to hug the inner wall but the largest cells will slowly migrate towards the outer wall as the cells whip around the spiral just like if they were in a tiny centrifuge this is useful because any cells large enough to be affected and migrate will tend to be the extremely rare oversized cells which are indicative of an early stage cancer so using this you can actually collect lots of them so they can be analyzed even though the rare and hard to target you could in this way potentially figure out what sort of cancer you have and where it probably is using just a blood sample we may come back to this design and explore it in more detail in a future video and maybe even give it a test of some real blood finally this one I was particularly excited about because there are almost no papers that actually made a microfluidic version of this design and most just simulated it so this is actually one of the smallest of these in the world as far as I can tell many of you probably recognize this as a Tesla valve it's a one-way valve with no moving parts fluids can only flow in one direction easily and in the other direction they get turned around and sort of self clog stopping the flow because of how tiny this is it's hard to really demonstrate the one-way action as I'm feeding in liquid it's easy to feel the difference though in one direction fluid flows easily and gently pressing on the syringe is enough to make it flow but in the other direction I have to apply significant force to overpower the system I can do it but when I release the pressure fluid instantly stops flowing so I'd call that a success either way this test is proof of just how much detail you can obtain with this method these channels are tiny but they maintain their shape through the whole process and the design even works well I can see why lots of people simulate these though having made this I can see why you'd want to tweak the design a bit to improve its performance on such a small scale but luckily with this method making these cells is so cheap and easy that if you come up with a better design you can have it made in no more than an afternoon for nothing more than pennies worth of material but that's where I think I'm gonna leave it for now micro fluidics is such an amazing field and we'll definitely be talking about it again in the future I had to leave out so much so I hope this small taste was enough to get you excited and start thinking about what crazy tiny devices you want to make and if you've got ideas for flow cells you'd like me to try and make be sure to leave me a comment and let me know I've included some links to papers I referenced in the description for those of you who'd like to do some more reading before I close out I want to say a big thank you to my amazing patrons and channel members who make these videos and this research possible if you'd like to support the channel and help keep the flow of videos coming then consider becoming a channel member or supporting on patreon I also recently made a cofee account for those who'd like to support but don't like the other two platforms and that's we're all in this video as always be sure to subscribe if you're new and ring that bell to see when I post new videos if you'd like to see these projects long before they make it into videos then be sure to head over to my other social media pages especially Instagram that's all for now and I'll see you next week

Channel: The Thought Emporium

Views: 705,441

Rating: 4.9506292 out of 5

Keywords: microfluidic, microfluidics, micro, cnc, milling, shrink film, shrinky dink, crafts, biotech, biomedical, tesla, tesla valve, one way valve, flow filtration, blood test, diy, how to, tutorial, research, biology, chemistry, science, smallest, worlds smallest

Id: eNBg_1GPuH0

Length: 11min 25sec (685 seconds)

Published: Sat Apr 06 2019

Reddit Comments

[u/stalinorgel]

This is the same guy who cured his lactose intolerance with self made gene therapy. He is still alive and kicking. Great channel.

[u/microfluidics]

I am a microfluidics engineer, who has been working in this field for a while now, so any questions regarding microfluidics, fire away.

[u/DoucheForHung]

A joyful watch. I fell smarter now and the best thing about it... I have almost no idea what I just saw... But it's interesting

[u/Arcterion]

Ooo, that's neat as fuck. :D

[u/antiquemule]

Check out David Weitz' lab at Harvard for loads of cool applications:

Microfluidics at the Weitzlab

[u/thebestasmrfr]

Interesting 😀

[u/The_Funny_Faggot]

Very cool, I did a bit of research using microfluidics especially how to simplify it and I believe it is going to be important in the future of biomedical research. I'm used to a much higher tech way of producing these devices using silicon wafers and PDMS molds so it was cool to see you can do this with much more basic equipment (obviously you cant get very high accuracy of channel widths using this technique but its cool nonetheless). Many research groups have used this to create so called organs on a chip for liver, brain and lung. Its a very versatile techniques because you can grown cells in these and create dynamic, and easily controlled cellular environments then study the effects on cells, its been used to model stroke, look at neuron grown, tumor invasion just to list a few.

[u/spencebah]

Tesla Valve at 9:15

[u/DohRayMe]

Learnt about, Shrinky Dink, Tesla valve, Cancer cells and blood. Very good video.