
Paper Centrifuge - mhb
http://gizmodo.com/this-human-powered-paper-centrifuge-is-pure-genius-1790996940
======
nneonneo
As usual, what you really want to do is read the paper:
[http://www.nature.com/articles/s41551-016-0009](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.

~~~
tbabb
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.

~~~
hguant
Quick math and google says no:

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...](http://hyperphysics.phy-
astr.gsu.edu/hbase/Relativ/rellim.html)

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.

~~~
andrepd
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.

~~~
sobani
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....](http://www.astronomy.ohio-
state.edu/~pogge/Ast162/Unit5/gps.html) [2]
[https://en.wikipedia.org/wiki/Global_Positioning_System#Hist...](https://en.wikipedia.org/wiki/Global_Positioning_System#History)

------
onchance
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/](https://www.macfound.org/fellows/965/)

[2]:
[https://en.wikipedia.org/wiki/Foldscope](https://en.wikipedia.org/wiki/Foldscope)

[3]:
[https://www.ted.com/talks/manu_prakash_a_50_cent_microscope_...](https://www.ted.com/talks/manu_prakash_a_50_cent_microscope_that_folds_like_origami)

~~~
agumonkey
Heh, not surprising. I must follow this Man.

------
okreallywtf
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.

~~~
tdaltonc
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.

[http://extreme.stanford.edu/projects/embrace](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.

~~~
okreallywtf
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.

------
erikcw
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/](http://heritageradionetwork.org/series/cooking-issues/)

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

~~~
Chris2048
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...](http://www.ginandluck.com/clarified-citrus-centrifuge-process/)

Also, do you have to clean this one each time (as opposed to using different
bottles placed inside?

~~~
erikcw
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...

~~~
Chris2048
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...

------
titzer
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).

------
JohnJamesRambo
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.

~~~
tejtm
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)?

~~~
JohnJamesRambo
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.

~~~
Florin_Andrei
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.

~~~
JohnJamesRambo
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.

~~~
akiselev
_Ultra_ centrifuges 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.

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

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

Seems _a propos_! :)

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

~~~
feiss
yup. Amazing application..

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

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

------
rawnlq
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.

~~~
mhb
It's not: [https://diybio.org/2012/06/11/dremelfuge-
classic/](https://diybio.org/2012/06/11/dremelfuge-classic/)

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

~~~
dekhn
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.

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

[https://www.amazon.com/Digital-Photo-Laser-Tachometer-
Contac...](https://www.amazon.com/Digital-Photo-Laser-Tachometer-
Contact/dp/B001N4QY66)

------
ahoka
Why is this on the front page?

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

From
[http://catb.org/jargon/html/H/hack.html](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](http://catb.org/jargon/html/meaning-of-hack.html) and
[https://stallman.org/articles/on-
hacking.html](https://stallman.org/articles/on-hacking.html)

------
readhn
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...

~~~
hxegon
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.

~~~
readhn
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.

~~~
HCIdivision17
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.

~~~
pg314
Exactly. One of the things the OLPC (One Laptop Per Child) project initially
ignored was the infrastructure needed, such as electricity and internet
access.

~~~
dm3730
> 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.

[http://www.pcmag.com/article2/0,2817,2395763,00.asp](http://www.pcmag.com/article2/0,2817,2395763,00.asp)

~~~
HCIdivision17
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.

------
readhn
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...

~~~
DasIch
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?

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

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

~~~
lightedman
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.

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

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

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

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

~~~
jrockway
Is posting to Hacker News part of your work?

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

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

~~~
lightedman
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.

~~~
oh_sigh
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.

------
grymoire1
Re-inventing a 5000-year-old toy is genius? H'okay......

~~~
SamBam
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.

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

------
williamle8300
This is awesome! Hopefully no one decides "epi-pen" this idea

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

~~~
Declanomous
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.

~~~
lb1lf
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...

~~~
fryguy
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.

~~~
lb1lf
Depends. If your employer happens to be named Schilling, we may need to get
together for a beer. :)

------
readhn
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?

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

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

~~~
readhn
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?

~~~
the_watcher
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.

