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Paper Centrifuge

gizmodo.com

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Re: Paper Centrifuge

#81

Post by hguant »

tbabb wrote: post #77
nneonneo wrote: post #41

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 th…

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:

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.

Re: Paper Centrifuge

#82

Post by hackuser »

nneonneo wrote: post #41

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 th…

> 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.

Re: Paper Centrifuge

#83

Post by fryguy »

lb1lf wrote: post #78
Declanomous wrote: post #13

Earlier quoted context omitted.

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…

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…

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.

Re: Paper Centrifuge

#84

Post by pvg »

tbabb wrote: post #77
nneonneo wrote: post #41

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 th…

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.

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)

Re: Paper Centrifuge

#85

Post by wosos »

hguant wrote: post #81
tbabb wrote: post #77

Earlier quoted context omitted.

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: 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 p…

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

Re: Paper Centrifuge

#86

Post by jessriedel »

tbabb wrote: post #77
nneonneo wrote: post #41

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 th…

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.

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.

https://www.amazon.com/s/ref=s9_dnav_bw_ct02_s?node=31798501...

Re: Paper Centrifuge

#87

Post by okreallywtf »

tdaltonc wrote: post #70
okreallywtf wrote: post #67

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…

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 The problem statement for that would be something like, "n…

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.

Re: Paper Centrifuge

#88

Post by Nition »

pvg wrote: post #84
tbabb wrote: post #77

Earlier quoted context omitted.

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.

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)

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

Re: Paper Centrifuge

#89

Post by pvg »

Nition wrote: post #88
pvg wrote: post #84

Earlier quoted context omitted.

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)

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.

Re: Paper Centrifuge

#90

Post by nneonneo »

pvg wrote: post #84
tbabb wrote: post #77

Earlier quoted context omitted.

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.

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.
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