Hacker News new | comments | show | ask | jobs | submit login
Paper Centrifuge (gizmodo.com)
412 points by mhb on Jan 11, 2017 | hide | past | web | favorite | 129 comments

As usual, what you really want to do is read the paper: http://www.nature.com/articles/s41551-016-0009

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.

> As usual, what you really want to do is read the paper:

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.

If you read Nature and science papers, plan on reading the supplementary materials (typically 20-200 pages) where we are forced to put all the real science. And the online methods (a half measure spurred by outrage at the preceding).

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.

Agree. Nature News and Comment [1] is where I usually go first for my science news

- [1] http://www.nature.com/news/

At $199 a year it is extremely expensive. I remember I was paying close to $1,000 a year for the journal my 1,000 student college I work for.

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.

So how does someone not connected to a university get access to all this essential knowledge? Subscribing as an individual to JSTOR, etc. is far too expensive (thousands per year, I believe) and complicated. I don't want the administrative burden of my own research library.

The sarcastic answer: You have to pirate papers. There is a popular Russian hub for science papers that contains almost every paper ever published in the last couple of years. It is used by many academics.

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.

Thanks a lot for the summary. It's so hard to look at simple things and see how difficult it is to make them a product, and even harder to see the edge cases that prevent it from being used in healthcare.

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.

Holy crap. 125,000RPM for a 5mm disc means the edge is spinning at nearly 9,000mph.

On top of that, the g-force would be

    a = v^2 / r 
    v = 2 * pi * 5mm * 125000/60 s^-1`
    r = 5mm 
...giving 87,000 gees?!

I start to wonder if general relativity effects (frame-dragging?) start to become noticeable at that acceleration.

Quick math and google says no:

9,000 MPH = 0.00001342 C

Threshold for relativistic effects is .01 C according to this paper:


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.

I believe in GPS satellites relativistic effects are due in greater part to the difference in gravity between the surface of the earth and the satellite, more so than the special relativity effects.

According to a reference[1] from Wikipedia[2] the effect would be 45 μs for general relativity 7 μs for special relativity, combining into a 38 μs drift.

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...

Relativity has almost no effect on GPS at it's worse it would have an accuracy degradation of less than 1cm, there are considerably bigger sources of errors in GPS than relativity and various corrections to those. Shadows, echoes, atmospheric effects and the doppler effect have considerable effect on GPS accuracy, relativity will not.

Relativity has a massive effect on GPS. If unaccounted for, the error would increase by 11km per day.

EDIT: I might be wrong on the “11km” part. See reply


No it doesn't http://www.physicsmyths.org.uk/gps.htm This would only be an issue if you had substantial drift between different sattlites the 38 microsecond delay is irrelevant since all satellites in the constellation have a similar delay.

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.


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.

Thank you. Is it fair to say that the 38µs correction done in the satellites is more for GPS’s other use? That is, as a source of accurate timekeeping to the receivers? It sounds like positioning is not affected like I thought, but the designers felt the need to engineer a solution to the relativity problem nonetheless.

There are different corrections for relativity, one is the "one time adjustment" that all clocks got which is on average closer to earth clock rates but it's not 100% constant since general and special relativity do not affect all satellites in the same manner and they all got the same clock correction.

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.

Yes, putting MC and check it's time after a device-lifetime of use would be quite an interesting experiment.

Where do you get those 9000 mph from? as far as I can see the edge velocity will be 65.45 m/s or 236 km/h:

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)
or, in km/h

   v (in km/h) = pi * D * rpm * 60 / 1000  (D in m)

   3.141593 * 0.01 * 125,000 * 60 / 1000 = 235.62 (km/h)
These values are valid for a disc with a 5 mm radius. If that '5 mm' indicates the diameter the values would be halved to 32.72 m/s or 118 km/h.

You used 5m instead of 5mm, putting you out by a factor of 1000:

    2 * Pi * 0.005m * 125000/60 s^-1 = 65.4m/s = 235km/h.

This is an impressively high spin rate. The sub-$1k centrifuges on Amazon look like they about 10,000 RPM, although at least one gets 100,000 RPM.


You're wrong. 125,000 RPM with a 5 mm diameter is 235.58 km/hour or 146.4 mph, giving you 1,712,957 m/s^2 or 174,613 Gs (weird!)

No it isn't, you must have mistyped something. The diameter, not radius is 5mm, not that it makes a big difference. The top speed is a little over 30 meters per second or 70 mph. (Edit: possibly because you turned seconds into 1/s for some reason? Either way, the edge of the disk is not going hypersonic or anywhere close to it)

It's my fault - I misread R_d as diameter and not radius. The disc is indeed 5mm in radius (10mm in diameter). With this value, the speed of the disc edge is 65m/s or about 145mph.

Actually the radius is 5mm in the paper, it was nneonneo that got that part wrong.

The wrong part doesn't come from the 5mm, it comes from being orders of magnitude wrong by some other method.

Oh, yeah I know. Didn't mean to imply your main point was incorrect.

If I was using this thing, I would fix one end to a solid endpoint and pull the other end so that I would not be in the line of fire if the thing exploded.

The video shows them doing exactly this with one end tied to a door handle.

The lab behind this invention is led by Manu Prakash, a MacArthur Fellow [1] with a knack for unconventional solutions. He's the same guy who developed Foldscope, an ultra low cost microscope [2][3].

[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_...

Heh, not surprising. I must follow this Man.

Looking at this makes me want to find a way to crowdsource basic research problems like this to try and take advantage of the ingenuity of people who would otherwise never even know that this kind of problem existed.

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.

I think that if you could get the problem statement as concise as "Need a device that can reach X rpms and can only be made of Y and Z and must cost less than N" then the battle is won.

Another example of this kind of innovation that comes to mind is using freezing wax as a heat source to keep neonatal babies warm.


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.

I agree that identifying the 'leaf' problems is the majority of the work but it would be nice to see if you could improve the quality of some of the solutions to these problems by opening them up to the entire world. It would be interesting to see if people in the 3rd world (who are used to making do with less and clever use of materials) could even improve on some lab solutions.

This is slightly off-topic -- but for any kitchen nerds out there, Dave Arnold of Cooking Issues (amazing podcast[0]) and Searzall fame is doing a crowdfunding campaign[1] to build an "affordable" centrifuge for the kitchen/bar. His goal is to make it the next piece of high-end modernist cooking gear within reach of the home cook...

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.

[0] http://heritageradionetwork.org/series/cooking-issues/

[1] https://blog.modernistpantry.com/spinzall/

Not sure the $6k centrifuge isn't a lot better though.

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?

Of course the home cook doesn't need a centrifuge -- but I sure do want one!

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...

My point is, that section discusses pricing.

BTW, did you document the home made circulator? I bought a bunch of Anovas during cyber Monday, and wondering if that works out economically...

Part of me wonders, A.) if it's possible to enrich uranium using something like this, and B.) how many man-years of hand-spinning it would take to get enough weapons-grade material that way.

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'd be suspect about the quality of the centrifuging since it is changing directions on every spin. But I haven't read the paper so maybe they have checked that.

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.

Wouldn't the g-force direction always be the same (away from the center) regardless of direction of spin and zero at the inflection between spin directions (normal gravity excepted)?

If you have something slung on one side of the tube, it will rapidly want to go to the other side of the tube as the centrifuge switches direction on the reverse spin.

1. The g-force always acts in one direction: towards the outside of the disc.

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.

Yes I understand what you are saying, that the force is going to the outside of the disc, but using even light braking (over minutes or even hours for ultracentrifuging) can disturb a pellet or separation. This is rapidly coming to a complete stop and reversing direction over and over.

Ultracentrifuges are a whole different animal than blood centrifuges. The former are used for separating tiny things like viruses, organelles, and macromolecules while the latter are used just to separate blood into white blood cell/platelet, red blood cell, and plasma layers. These cells are orders of magnitude larger than anything you'd use an ultracentrifuge for and short of deliberatly shaking the sample, it won't mix quickly after the centrifuge.

If the diameter of the tube is small, the effect of changing direction is neglegtible compared to the centrifugal force.

Sometimes the most advanced technology in the world is the simplest most childish thing around.

"Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away."

Seems a propos! :)

I remember doing this with big coat buttons and string when I was a kid.

yup. Amazing application..

Beautiful, beautiful, just beautiful. Reminds me of primitivetechnology on YouTube.

I'd love to see how far one can go with 'simple' physics.

15 mins of human labor per test doesn't sound cheap but I guess you can get the patient to do it themselves.

A bit curious, why is a cheap centrifuge hard to build? It seems like a pretty simple device and motors are pretty cheap.

think remote villages where it's difficult to bring equipment in, places without electricity, etc.

[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.

In the environments this would be used Labor is cheaper than and probably more available than electric power. This could also be built on site rather than trucked in, all you need is the knowledge of how to build it. In some instances, this kind of tool may be the only way to meaningfully accomplish testing.

It's not: https://diybio.org/2012/06/11/dremelfuge-classic/

But presumably this could be for regions in which even those materials are difficult to obtain.

I use the dremelfuge. It's not particularly safe, but it does get the job done for very basic spin-downs. You don't have really precise RPM control, as well as many other things.

I wonder if you could use a laser tachometer to help dial in the RPM? e.g.


While they're not that hard to build, the lab ones tend to be very heavy and not able to survive being carried around and dropped. The centrifuge they describe can be easily transported, is durable, and easy to fix. It's a great idea to be able to provide field medics with a tool like this in difficult environments where a lab grade device would be impractical.

Motors need power, not having (much) power at hand is often one of the first problems helpers in such situation have, so something which doesn't need power is a huge boon.

Exactly. One of the reasons the recent ebola epidemic hit where it did is because there are still many areas where clean water and bleach (which would have prevented much of the outbreak) are difficult to obtain.

Don't forget the cultural practice of kissing dead people.

This is for areas where humans lives are cheap. 15 minutes of human labor cost very little there.

Cheap for us. But maybe not for other people living there.

Why is this on the front page?

This is Hacker News, and this seems like an excellent hack.

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

whats next? a fake life size cut out image of a doctor with a smartphone attached to it for a speaker?

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...

I'm not really sure what you are trying to say here. If you have a better solution to centrifuge availability than a 20c one made out of paper, please enlighten us.

yes i have a better solution - kill one of those multibillion military projects and redirect the money to buy lifesaving medical equipment to the places that need it. equip research facilities with equipment and provide local training.

paper centrifuge? its like a slap on the face.

Those expensive medical machines require a lot of infrastructure to operate properly. You could get a machine there, but you likely couldn't provide it clean and reliable power without additional equipment and technicians to maintain it. Bootstrapping infrastructure is stupendously hard and expensive (and is a huge measure of a country's wealth - a lot of the US wealth is tied up in structural infrastructure like power lines, roads, plants, etc). It's a generational process taking decades to bootstrap.

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.

Exactly. One of the things the OLPC (One Laptop Per Child) project initially ignored was the infrastructure needed, such as electricity and internet access.

> initially ignored

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 not sure, but I think pg314 is making reference to the hand crank that could be used to power the laptop. I don't think it was initially included in the design (I may be wrong on that). I also heard rumor it wasn't a smashing success as a power supply, but it was so long ago that I don't remember the details terribly well.

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'm no longer really following what OLPC does, but as far as I know that hasn't changed. Other loosely associated organisations like e.g. OLE Nepal (olenepal.org) are addressing that, though.

I did not meet any Negroponte fans out in the field.

> kill one of those multibillion military projects and redirect the money

And how are the inventors supposed to do that?

we, the citizens who vote are supposed to do that.

So you're criticizing the situation that makes this invention such an improvement, not the invention itself? I certainly understand that, but your comments on first reading to me (and probably to other readers) appear to be criticizing the invention itself, which I and other readers vehemently disagree with.

And what happens if the people I vote for, who are supposed to fix this situation, don't win the election? Should I just sit around for a couple more election cycles and do nothing?

> yes i have a better solution

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.

Justify what actions?

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.

What actions? We keep voting for the government that chooses to fund programs that kill people instead of saving lives.

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.

> technology that's not that expensive

"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.

Walk into any modern hospital central lab today, look at the life saving technology thats available to us and ask yourself why we still have not figured out how to give other people access to this?

paper centrifuge? come on...

You mean why haven't we achieved world peace and provided the entire world with stable electricity and sufficient capital to build labs and expensive medical equipment to fill them?

Really? Didnt anyone used to do this when you were a kid? http://www.makeandtakes.com/diy-paper-spinner

I can't remember using it to centrifuge blood samples, but maybe your childhood was different from mine.

We used it to demonstrate centrifugal forces in elementary school by spinning one and putting drops of food coloring in the center. They were made of lightly-waxed parchment paper so you could see a trail it left behind as it got flung off.

I'm just surprised it took this long. That particular lesson was... 26 years ago for me.

Well why didn't you tell the world about this 26 years ago. Heck, why didn't you tell the world 2 days ago?

Then, much like now, I'm too busy with minerals and the inordinate amounts of money people will pay for them.

It must be tough having no free time over 26 years. Hope retirement goes well for you!

Retirement? That doesn't happen to workaholics like myself.

Is posting to Hacker News part of your work?

It's what I do while I'm waiting for 4-ton boulders to get moved out of the way with heavy explosives.

You should have used that time to invent the technology that you knew about for 20+ years.

Why me instead of someone else? Someone else needs to have success in life. I'm too busy getting you guys the lithium you need for your portable devices because you can't be bothered to do proper recycling.

That's quite noble of you. I just hope you aren't also sitting on the cure for cancer, so you don't hog all the glory for humanity.

> Inspired by an ancient toy...

First words of the article.

Re-inventing a 5000-year-old toy is genius? H'okay......

Putting an ancient toy to a new and brilliant use is genius.

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.

And still a better product than whatever Thanos was working on.

This is awesome! Hopefully no one decides "epi-pen" this idea

Cool idea but it can't possibly be safe to spin infected blood on a device such as this.

I don't know why it would be any more dangerous than a typical centrifuge. Samples are in a vial, and that vial is what is responsible for containing the sample while you spin the samples. Having been around conventional centrifuges that have been destroyed due to improper balance, I assure you that any way you can imagine infected blood being distributed by the paper model would be 10x worse with a normal centrifuge. At least with this method, the motor has a brain and will stop as soon as things start going south.

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.

True story: The company I work for make some pretty hefty winches for offshore use. Think ROVs, subsea oil installation, salvage &c.

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...

There are some videos on youtube of anchors dropping too fast:




It's pretty scary.

(Someone else posted one of these links originally, I'll try to find it)

I work at a company that makes ROVs, and your story sounds very similar to a story I heard a few years back. I wonder if it was one of ours that got dropped.

Depends. If your employer happens to be named Schilling, we may need to get together for a beer. :)

That story makes exploding $100k centrifuges sound like a bargin.

Eh, both of you are right.

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.

You are comparing when things go wrong with a centrifuge to every single use of this device. How would you contain the microscopic airborne particles?

I suspect for most diseases break the centrifuge (and vial) would not drastically raise the risk for the bystanders -- we have plenty of microscopic airborne particles with all sorts of bacteria around us already, especially in cities. And I think malaria would not be contagious at all this way.

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.

>> Samples are in a vial

In re-reading my comment, I realized it isn't clear that normal centrifuges use vials to contain the sample as well.

Regardless, having spent thousands of hours in a lab, I think the traditional lab centrifuge is probably more dangerous.

Read the paper - it describes three safety features of the device which are explicitly designed to contain infected blood.

Why not? The videos show the devices being operated with one handle fixed against a wall/door. In that situation, nothing flying off the disc will go towards the operator. You could also enclosing it in a box or operate it inside a hole in the ground.

The cost of the system goes up with the centripital force, which goes up with the RPMs.

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.

"nothing flying off the disk will go towards the operator". What about other people? As you say, you can enclose it in a box, but that means making a glovebox, which increases cost significantly.

> What about other people?

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.

"Single person to be present"- so you can afford a dedicated room to spin samples? That increases cost.

You need a glovebox so you can load your samples... although technically I guess that outboarding the strings works too.

Or just a big cardboard box and a glove+sleeve.

Plastic bag around the disc?

its a nice toy, for kids to learn science.

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?

Don't underestimate the power of a simple(r) solution. A cheap and reliable solution, readily accesible, is powerful when access to so many luxuries we would consider basic necessities don't exist. These scientists have done a lot of work to show that a simple, effective solution can help people now. Not some time later when the next generation has enough to be able to use it.

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.

> Its year 2017, there is no reason why those people should not have access to the advanced technology we enjoy today in the west.

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.

Currently, there is absolutely no realistic way to set up the infrastructure required to operate such labs in third world countries. The costs would be astronomical.

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.

That's because borders stop them from accessing much greater wages.

Even if you find the situation bad, these researchers helped improve the situation.

i understand that they do what they have to do.

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?

If you lived somewhere in which neither were available, you'd want the one that could actually be delivered in time to make an impact.

> How would most of us feel if we came into an office for a blood draw and saw this toy?

"I might be dying of malaria; I don't care"

> How would most of us feel if we came into an office for a blood draw and saw this toy?

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

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact