Paper Centrifuge
gizmodo.com
gizmodo.com
This is a well-written and very clear paper. It covers several aspects that went unmentioned in the Gizmodo article, and highlights that although building such a device may be trivial, evaluating and studying it is not.
Some highlights: the paper covers how the device was built in detail, including information on the three safety mechanisms used to ensure the operator doesn't get exposed to infected blood (shatterproof plastic capillaries, epoxied sample holders made from drinking straws, and sealing of the capillaries inside two paper discs). It is exclusively made from low-cost materials, but it's more than just a piece of paper, handles and some string (fishing wire).
The paper also covers the physical dynamics of the "paperfuge" in great detail, analyzing its rotational dynamics and building a theoretical model of motion that agrees well with the physical observations (captured with a 6000fps high-speed camera). It also shows that the max RPM varies with disc size, with 125000 RPM for a small disc (5mm diameter). The paper even mentions that this was submitted as a Guiness World Record.
Finally it shows that the paperfuge produces sample separation results on par with electromechanical centrifuges using similar spinning time (1.5min for paperfuge, 2min for centrifuge for plasma separation), and does an analysis of the resulting blood samples.
I really like that there's a comparison to commercial centrifuges, since that shows the quality of medical care isn't going down simply to be cheap. Overall it looks like a well thought out design.
On top of that, the g-force would be
a = v^2 / r
v = 2 * pi * 5mm * 125000/60 s^-1`
r = 5mm
I start to wonder if general relativity effects (frame-dragging?) start to become noticeable at that acceleration.
9,000 MPH = 0.00001342 C
Threshold for relativistic effects is .01 C according to this paper:
http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/rellim.ht...
EDIT: Rereading that paper, they're focused at the particle level, which may or may not make this irrelevant. I know anecdotally that GPS satellites have to take relativity into account. Geostationary satellites move at 1.9 miles per seconds, which is 6840 mph - quite a bit lower than our centrifuge. That being said, the precision required for GPS means that very small changes due to relative effects have a rather large impact. In short, where there is motion, there is relativity. Is it enough to measure here? Possibly - sticking a small microcontroller and having it report the time would be interesting. Is it enough to matter? The answer is relative.
So although you are technically correct (45 > 7) they are both significant.
[1] http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.... [2] https://en.wikipedia.org/wiki/Global_Positioning_System#Hist...
EDIT: I might be wrong on the “11km” part. See reply
http://physics.stackexchange.com/questions/1061/why-does-gps...
It's also less relevant when solving using the more common method which is time-tagging at the receiver, relativity might be a bigger pain if you are doing time-tagging at the transmitter but since the clocks of different satellites are not synchronized and can differ by as much as 1ms that delta would be more of an issue than relativity.
If you are doing normal GPS accuracy which is 15m you don't need to use relativistic correction in the receiver, is you are solving for almanac data you do not need to do relativistic correction in the receiver, you only really do relativistic corrections when you are using centimeter level accuracy GPS and even then you have considerably bigger corrections to do.
Yes relativity was accounted for when GPS was designed, but it's by no means would send you to China, not even to the wrong town.
What GPS needs to work is for the receivers to be able to calculate a proper geometric range delay or at least be constantly and consistently wrong when calculating the delay for different satellites in the cluster.
http://www.navipedia.net/index.php/GNSS_Basic_Observables
Discounting relativity would reduce accuracy, but it would be consistent and constant and so would not present that much of an issue, it's also by far not the biggest offender when it comes to corrections.
The other "relativistic" correction is one done in the receiver and is needed for geometric range delay calculation, basically taking into account that light doesn't travel in a straight path, we've kinda known that since the early days of classical optics - Fermat's principle or the principle of least time.
Now while it's true that we are using the "relativistic" version of this in our calculation solving the classical or even ignoring it all correctly as long as we account for other effects would still allow you to find a starbucks.
Since GPS was initially intended for military use it had other uses such as time keeping that can be used to synchronize communication, encryption and other things these errors can be cumulative whilst navigation errors are often not since the drift would be more or less uniform with all satellites you see.
https://www.amazon.com/s/ref=s9_dnav_bw_ct02_s?node=31798501...
Fill in the blanks, m/s:
v (in m/s) = pi * D * rpm / 60 (D in m)
3.141593 * 0.01 * 125,000 / 60 = 65.45 (m/s)
v (in km/h) = pi * D * rpm * 60 / 1000 (D in m)
3.141593 * 0.01 * 125,000 * 60 / 1000 = 235.62 (km/h)
2 * Pi * 0.005m * 125000/60 s^-1 = 65.4m/s = 235km/h.An aside: If you are not reading Nature you may be missing out on a lot. I would guess the same applies to Science.
Only the back half of Nature is actual research papers, which often are indeed very slow going. The other half is science news written clearly - it's fascinating, not a chore at all - and with a level of knowledge and sophistication unmatched elsewhere (AFAIK), and most importantly it will completely change your perspective: There is a world of research and knowledge that you won't even know exists if you read the more 'popular' science press.
A little time reading Nature will save you much more time reading less informative publications.
Wouldn't want to waste words on silly shit like methods, references, discussions, etc in a CNS paper, would we?
LIGO doesn't even bother sending papers to Nature or science any more. The editors at both are unbearably pompous.
Not including JSTOR and other subscriptions for these Journals. The bill 10 years ago was about $70,000 for journal access on computers where I had the print copies in boxes behind the journals or in the storage area collecting dust.
Almost no organization can afford to pay for all the stores, so even universities have limited access in the sense that they can only offer their students and staff a limited selection of what is available. Subscription fees are too high, single journals are often only available in bundles with other journals/topics, increasing the price further. Publishers act as gatekeepers to (often publicly funded!) knowledge.
[1]: https://www.macfound.org/fellows/965/
[2]: https://en.wikipedia.org/wiki/Foldscope
[3]: https://www.ted.com/talks/manu_prakash_a_50_cent_microscope_...
There are probably a lot of problems like this that involve making something incredibly cheap to be used in the developing world.
I think people would do that for free if they could know the bare minimum big picture of how their contribution would be used (ie, malaria treatment, even if you have no idea how your gadget could fit in). It could be something like "Need a device that can reach X rpms and can only be made of Y and Z and must cost less than N" and then just see what people can come up with.
I'm not sure how it would work on more complex problems but for clever solutions that rely on limited resources and simplicity I would love to see what people could come up with.
Another example of this kind of innovation that comes to mind is using freezing wax as a heat source to keep neonatal babies warm.
http://extreme.stanford.edu/projects/embrace
The problem statement for that would be something like, "neonates need to be kept at a stable temp."
For this one it might be, "We need some way to separate blood solids from liquids." But maybe even that is too close to a "solution stated as a problem after the fact."
I think that challenges like this are commonly used as exercises for undergrad design students. But I love the idea of expanding it. A version of the x-prizes that require basically no capital, just imagination.
Not anywhere close to the $0.20 cost of this paper centrifuge, but still a pretty huge savings compared to the $6k-$10k units generally available currently.
See "DO I REALLY NEED TO BUY A CENTRIFUGE?" section here-> http://www.ginandluck.com/clarified-citrus-centrifuge-proces...
Also, do you have to clean this one each time (as opposed to using different bottles placed inside?
Kind of like how I started cooking sous vide 5 years ago with nothing but a pot, a probe thermometer, some ziplock bags, and a ton of patience. 3 meals later an I was wiring together my first home-made circulator...
BTW, did you document the home made circulator? I bought a bunch of Anovas during cyber Monday, and wondering if that works out economically...
Back of the envelope calculation: U-235 is a little less than 1% of naturally occurring Uranium, so supposing that you could load up 1 gram of Uranium per spin session, you'd get a maximum of 10 milligrams per session, so you'd need about 2.2 million sessions to get the requisite 22kg of U-235. Of course, you'd get nowhere near 100% efficiency out of a hand centrifuge in the first spin session, so it would probably require a cascade of several stages. If each stage gets rid of half of the U-238, then the number of spins you would need to get to 100% would asymptotically approach 2x, so we are looking at 4.4 million spin sessions. If each were to take 1 minute, we'd need about 8 years.
To be honest that seems overly optimistic, and there are probably technical details like dealing with UF6 gas that are way harder than I thought.
(happy to be corrected by a Nuclear engineer if there is one around).
I know that when I centrifuge something delicate, even having even a very light magnetic force brake on the centrifuge on can screw up the pellet at the bottom. Rapidly changing the g-force direction like this seems like the worst case scenario.
2. The diameter of the tube is small. It's nearly 1-D dynamics in there.
3. Very large g-forces only happen at top rotational speeds. When not rotating, the material gets slowly mixed back up, but at the regular (i.e. very slow) diffusion speed.
So: separation works always towards the outside + re-mixing is a much slower process = it works as expected.
Seems a propos! :)
I'd love to see how far one can go with 'simple' physics.
A bit curious, why is a cheap centrifuge hard to build? It seems like a pretty simple device and motors are pretty cheap.
But presumably this could be for regions in which even those materials are difficult to obtain.
https://www.amazon.com/Digital-Photo-Laser-Tachometer-Contac...
[edit:] from article:
A centrifuge is an essential tool for hospitals and labs across the world. Trouble is, centrifuges are expensive, bulky, and require electricity. In poor regions where tropical diseases flourish, these instruments can be hard to come by, thus limiting the ability of point-of-care healthcare workers to do their work. [...] The device, dubbed the “paperfuge,” can reach spinning speeds of 125,000 revolutions per minute (RPM), and exert centrifugal forces equivalent to 30,000 g’s. It’s roughly a hundred times faster than previous non-electrical efforts, and it’s considered the fastest rotational speed ever recorded for a human-powered device.
From http://catb.org/jargon/html/H/hack.html
> Originally, a quick job that produces what is needed, but not well.
See also http://catb.org/jargon/html/meaning-of-hack.html and https://stallman.org/articles/on-hacking.html
its sad that people have to die because they don't have access to the technology that's not that expensive and readily available in the "developed countries".
And now we have to come up with some pathetic paper gizmos to justify our actions? Are we really that developed? Seems to me that we are going backwards...
How does this make the West go backward? The researches are helping to improve the situation.
If you are so concerned, you can go donate to charities that distribute vaccines.
Iraq - Iran - 1 million dead Vietnam - up to 4 million dead Afghanistan - up to 1.5 million dead
+ trillions of dollars we spent to support all of this.
paper centrifuge? its like a slap on the face.
And how are the inventors supposed to do that?
All the while that is getting built people need help now, and this clever adaptation of a toy fills that niche. Eventually they'll have access to the more advanced modern wonders, but for now this can help people almost immediately.
Initially? Has that changed now?
The founder, Nicholas Negroponte went on tear around the world claiming to have saved millions of children and being the father of tablet computing. He even talked about throwing OLPCs out of helicopters on to those brown and black masses. Even claimed that mothers would be better off getting a laptop than subsidized food. I recall he shat on some reporter who had the audacity to quote UNDP analysis that showed spending on lunch-at-school programs had far more impact than spending on teacher technology.
I'm actually far more optimistic these days about tech in difficult areas. The computing power (and screens!) we can get out of just a small battery is phenomenal compared to OLPC's time.
I did not meet any Negroponte fans out in the field.
Now implement it.
Paper Centrifuge s seems like one of many reasonable stopgaps until your better solution is realized. It'd be sad if we let people die simply because we looked down on practical solutions for not being high-tech enough.
"Expensive" is relative, and the technology has extra costs outside of itself that have been paid in some parts of the world, but not in others. In a part of the world where electricity may as well be unobtainium, that heavy, carefully-calibrated, $1000 centrifuge isn't much better than the scrap value of the metal it's made from (while still being obscenely, prohibitively expensive for the people it would help).
> justify our actions
Who's talking about justification, besides you? There isn't anything to justify.
> Are we really that developed?
We've got shinier toys, if you want to call that "developed". We haven't improved upon the human race itself, if that's what you mean. Humans are naturally selfish and tribal. Society shifts tribal boundaries, and social structures like government can force selfishness into a longer-term view, but that's about all.
paper centrifuge? come on...
I'm just surprised it took this long. That particular lesson was... 26 years ago for me.
First words of the article.
If you can find a way to make pick-up-sticks into a seawater desalinator, I'll bet you could get a nice article written up about you too.
A lot of centrifuges are just controlled by a potentiometer. You couldn't pay me enough to to get close enough to turn one of those off while it is self-destructing. The amount of energy involved is enormous. Someone blew up a (rather inexpensive) medical centrifuge at my school when they balanced some non-water liquid with water. It was a huge mess. Centrifuges are basically designed to contain the most dangerous bits when they explode. They don't keep your error from spraying all over the room.
Regardless, having spent thousands of hours in a lab, I think the traditional lab centrifuge is probably more dangerous.
It could be different for specifically engineered bio-weapon, but IMO the benefits of better detection far outweigh the risks, especially in the developing world.
Yes, a full-blown centrifuge could be made safer (put a shield around it, yadda-yadda). But if the paper device is made safe enough, I don't see why it should not be used when there are no better options. And it appears that it could be made safe enough.
Years ago, one of our customers had ignored a number of increasingly strongly worded safety bulletins, the end result being that just as they were going to hoist their megabuck ROV back aboard, the winch motors stopped and - for an encore - it turned out they hadn't tested the brake in ages, either - so it was incapable of halting the winch.
Now, the ROV itself would very gently drift towards the bottom. Too bad the umbilical cord between it and the winch weighs several kilos per meter.
The initial yank as the ROV freefell to the sea surface and the inertia of the drum ensured enough cable was paid out for the weight of it to keep the winch going faster and faster. Basically you had a very large loop with the ROV at one end, the winch at another.
This drum was designed for some 30rpm or so at the maximum design speed. Based on a video from a surveillance camera, we found the drum did close to 200 rpm as a few tons of cable pulled at it.
At this point, thinking the brakes must have been stuck disengaged, some brave soul with poor judgment and an axe appears, chopping off the hydraulic hoses to the brake. Lucky for him, the brakes weren't able to stop the thing anyway - otherwise, he would have found out if the designers had made the frame sturdy enough to remain intact during the retardation which would have followed.
This brave soul then realises that the game will be up in a few moments' time anyway - when the drum runs out of cable, at which point being anywhere near the winch will be very bad for you.
He runs like mad, disappear from the frame and then, seconds later - kerrrr-whaaang as the umbilical is ripped from the drum, the drum is torn from the frame and it all disappears into the large, blue waste disposal.
That led to a quite interesting post mortem. They found assorted bits and pieces of the winch all over the deck.
Somewhat off topic, but disintegrating centrifuges got me started...
https://www.youtube.com/watch?v=hvrgFPcPXfo
https://www.youtube.com/watch?v=RAcfaMDcY68
https://www.youtube.com/watch?v=b7pRfix_sNg
It's pretty scary.
(Someone else posted one of these links originally, I'll try to find it)
The device only requires a single person to be present.
> that means making a glovebox, which increases cost significantly.
You don't need a glovebox, you just need a way to pull on one of the strings from outside the box.
You need a glovebox so you can load your samples... although technically I guess that outboarding the strings works too.
At the low end and low RPMs all you need is some string and some paper. At moderate RPMs you could use (scavenge, even) off the shelf components to achieve your aims. For instance, how fast could you spin a bicycle wheel under human power before the system becomes dangerous?
From memory, an unbalanced bicycle wheel doesn't become noticeable to the rider (whose weight is holding the wheel down) until somewhere around 20 mph. A fair quality wheel doesn't get scary until about 25, but if you want to run down a valley or mountain road with your hands off the brakes (35+), you need the sort of quality that gives the lay person sticker shock.
Now, a wheel mounted to a block of wood doesn't have 150 lbs of anchoring it in place, but that's not the only device with bearings that can be located.
Hell, a washer with a broken water pump could work, if you knew how to rig it.
but really, what are we - stuck in the stone age? Its year 2017, there is no reason why those people should not have access to the advanced technology we enjoy today in the west.
make a pathetic paper centrifuge and give ourselves a pat on the back, really?
What have we become?
Even if you find the situation bad, these researchers helped improve the situation.
but lets not kid ourselves that this is some kind of solution that those people deserve. its an interesting student project, sure, if all equipment fails - there is a way to get your hematocrit count manually.
How would most of us feel if we came into an office for a blood draw and saw this toy? At the same time when there are machines widely available that will do complete CBC and other panels of blood tests on a single vacutainer tube in under 3 minutes?
Oh, good, I don't have to reschedule this appointment just because a firmware update took out their centrifuges. Eh? There's been a mass outbreak and the centrifuges are just busy?
Frantic centrifuging
"I might be dying of malaria; I don't care"
Unfortunately, we live in the reality in which not everyone has access to the same technology as the West. Some scientists and researchers should absolutely work on problems assuming that we'll be able to get the optimal solution to everyone. But that doesn't mean that there shouldn't be others trying to work within the reality that acknowledges that this isn't the case.
This is something like a mosquito net. Cheap, easy to distribute, and shockingly effective against malaria. Personally, I like the laser solution more, but you can't deny helping people now for a more ideal solution later.
The trick, as always, is to also get the better solution later. And things like this centrifuge help! People have access to more advanced medical techniques and data than they had before. They'll get diagnosed sooner and more accurately. The next generation will be healthier, more energetic, and more optimistic about their chances at a longer life. They'll have more strength and will for the hard task of building up their home and country, and in a generation or two will be on their way to things like reliable power grids, communication infrastructure, transport, and more.
But they'll need things to help bootstrap them first. Iodine for clean water and paper centrifuges for diagnostics are just a few of the first steps for people who have so little modern riches are useless to them. It only took us a few generations to get here, and I bet they bootstrap faster and harder than anything we've seen, like so much of the Asian peoples.
While, yes, ideally all humans would receive the same high standard of healthcare, pragmatically it's just not going to happen anytime soon. Before that happens, this is a very useful (and clever) tool.