Paper Toy Can Save Lives

Although there is a lot of discussion about health care problems in big countries like the United States, we often don’t realize that this is a “first world” problem. In many places, obtaining health care of any kind can be a major problem. In places where water and electricity are scarce, a lot of modern medical technology is virtually unobtainable. A team from Standford recently developed a cheap, easily made centrifuge using little more than paper, scrap material like wood or PVC pipe, and string.

A centrifuge is a device that spins samples to separate them and–to be effective–they need to spin pretty fast. Go to any medical lab in a developed country and you’ll find at least one. It will be large, heavy, expensive, and it will require electricity. Some have tried using hand-operated centrifuges using mechanisms like an egg beater or a salad spinner, but these don’t really move fast enough to work well. At the least, it takes a very long time to get results with a slow centrifuge.

[M. Saad Bhamla] and his colleagues at Stanford started brainstorming on this problem. They thought about toys that rotate, including a yo-yo. Turns out, those don’t spin all that fast, either. Then they considered a whirligig. We had forgotten what those are, but it is the real name for a toy that has a spinning disk and (usually) a string. When you pull on the string, the disk spins and the more you pull, the faster the disk spins. These actually have an ancient origin appearing in medieval tapestries and almost 2,500 years ago in China.

[Bhamla] found that how the toy worked was poorly understood (from a scientific standpoint)  and took pictures of one in operation with a high-speed camera. The team was able to create the “paperfuge”, a human-powered centrifuge that would spin at 125,000 RPM, enough to separate plasma from blood in under two minutes and isolate malaria parasites in 15. Some versions of the device could cost as little as twenty cents and don’t require anything more exotic than paper and string. You can see a video about the paperfuge, below.

Of course, there’s nothing to keep you from building a centrifuge like this yourself. It is cheap enough. The team made some versions using 3D printing, too. If you have a home lab and occasionally need a centrifuge, this might be your answer. It could be very helpful in a school setting, too, where students don’t have to share a single instrument.

Incidentally, [Manu Prakash] is a coauthor of this paper. He’s one of the Standford guys that brought us the $1 folding paper microscope a while back.

If you want something more involved (and less strenuous to operate), you can go open source but it won’t cost under a buck. Or you could get rid of that VCR you are hoarding under the bed.

Thanks [Rud] for the tip.

68 thoughts on “Paper Toy Can Save Lives

    1. It sits still in the AV rack. But it is not connected anywhere. The TV is long gone and connecting composite video to a FullHD beamer and viewing it on a 3m screen is nothing to enjoy. Therefore it is also not allowed to waste any standby power.

    1. Me too! It is literally inches/centimeters away from the face of the technician.
      I’m assuming that future versions spin the “paperfuge” inside of an enclosure of sorts, really don’t want to spray blood everywhere…

        1. I wonder how such an simple contraption was not used as mechanism of a weapon (some sort of super-sling or a catapult) prior to firearms invention.

          That aside, I really like it when advanced science and technology knowledge is back-ported into low-tech, low-energy (or human muscle energy), cheap solutions. Of course in this case, there still needs to be a supply of tiny, thin glass tubes, which are product of sophisticated industry process, but still …

          1. In fact there isn’t that much rotational energy stored in the device if it is operated by pulling strings apart by one man. And then I can imagine that fast rotation makes it difficult to control and as dangerous to the attacker as to the potential target.

            On the other hands two ropes in helix configuration were frequently used to power ballistae. However for siege weapons they relied on elasticity of ropes rather than on changing length of helix.

  1. In places where water and electricity are scarce…

    Aren’t well trained medical professionals also scarce?

    An even better invention, with far more reaching benefits to the health of society is…

    plumbing for waste.

    1. Then you know what you have to do, what are you waiting for? Their skillset matched with their priorities and they developed an ingenious method for a problem surly not everyone needs a device for, but everyone could benefit from the right people at the right place with that device. It’s a building block of humanity and development help.
      The downside I could think of is that such a simple and cheap alternative to lab equipment that could have been developed in their country takes the chance from that people there to build a business in branch.

      1. There’s no lack of thinking – poor people can do amazing things with scrap due to good thinking. What is lacking is coordination, co-operating on larger scales and resources (time and material). If you spend 16 hours a day just to survive it is hard to spend time and effort on making plumbing equipment from mud…

      2. Lack of thinking is the proximate cause of most problems in most places – no one in the Developed World can look down their noses (especially these days) at anywhere else in this regard.

          1. But so often you arrive to conditions in the field where a simple, basic tool is lacking. I honestly can’t tell you the number of hospitals I’ve visited where the lab has essentially stopped working due to the lack of a working centrifuge (To put it in perspective, I’ve hijacked 6 bikes in my life to use to spin down blood for essential lab tests).
            It’s a stupid problem, but it is a massive problem. There is a major portion of the human population that relies on handed down tech, without any means to support it. I’ve never tried to fix a centrifuge, but I have seen one fail (it’s exciting, and why I won’t try to fix them).
            Walking in to a “lab”, and seeing a $20,000 microscope, a $100k+ serum analyzer (with supplies), electricity, running water, and refrigeration is amazing. It’s only tempered by that horrible feeling in your gut when you see the centrifuge sitting in the corner, with an illegible sign, and miles of sealing tape… Everything comes to a stop because one piece of equipment doesn’t work.

            Yeah, the bike trick works. There aren’t always bikes.
            Yes, there’s a pretty hideous failure mode here… But field hospitals are pretty desperate places. This is a risk I can easily see people taking.

  2. In the 80s my aunt, in lab tech school, brought a hand powered centrifuge gadget home, not sure if it was a DIY or produced in a big factory with FDA approval. It was a plastic test tube holder/protector on some cord, she demonstrated a typical butterfly and vacutainer(test tube) adapter blood draw and separation into cells and plasma. The concern with both is breakage and the centripedal spewing blood-borne pathogens around.

    1. Maybe you don’t understand the use of comma as a separator in numbers (which isn’t imperial BTW – it is used also in metric countries) but it is relatively easy to learn.

      Prefixed: 125k RPM
      Improperly prefixed (decimal point): 0.125M RPM
      Improperly prefixed (decimal comma): 0,125M RPM
      Point separator: 125.000 RPM
      Space separator: 125 000 RPM
      No separator: 120000 RPM
      Angular velocity: 750k degrees/second
      In binary: 11110100001001000

      1. Thanks! But, in my opinion, 125000 rpm is enormous. By example an angle grinder have maximum 12000 rm, a car turbine have maximum 250000. Can really that toy have 125000 rpm? I don’t think so. Is just my humble opinion.

          1. sure
            just found the first place that described it, i admit the source isnt the best and that it is a pop-sci fact that is often repeated but apparently surprisingly hard to check.

            closer examination and half an hour of reading leads me to suspect that it is false, in the paper i found the temperature never exceeded 400 degrees and that would also be a lot closer to the instant nucleation temperature of water.


        1. It is rather unbelievably high, I put a stack of cardboard disks on a dremel type tool, 1″ diameter intending to see if they were any good for polishing, and they basically exploded off the shaft at around 30,000 RPM…. Cardboard being what many versions of this were made of as a kids toy back in the day….

          The imprecision lies in the “some”, maybe if you get real small buttons.

          1. Derp, reading that wrong, was thinking diameter was at center of disk, the big splodgy data “points” are where the diameter is, with the disk image horizontally aligned with them… sizes given as.. 5, 12.5, 25, 50 and 85 mm

    1. Good luck getting FDA certification, ACA approval, HIPAA compliance, and acceptance from Medicare and Medicaid.

      Regulation is the main reason healthcare costs so much. Lack of regulation is why knock-off drugs from third-world countries are so much cheaper.

        1. I have some insider perspective at a major hospital.

          Little paper cups for carrying pills cost $40/each because they are required to be “medical grade”, meaning from a certified vendor with certified supply chains. Their IT department spends millions every year to stay on the latest software as demanded by HIPAA. Their IT staff are worked to a breaking point to the point that several staff have been removed by security after mental breakdowns. Because of Medicare and Medicaid regulations, the hospital cannot turn anyone anyway if they have no insurance and cannot pay for their care. They must still receive the exact same care as any other patient, but the hospital must eat the cost. Medications are often extremely expensive because bringing a drug to market involves decades of research and development and billions in funding, and most never even get FDA approval. Then there’s the manufacturing cost of drugs, where every chemical, lab process, transport phase, and even packaging have to comply with extremely strict FDA requirement regarding everything down to what materials lab workers are allowed to wear (uniforms from certified suppliers).

          Granted, there’s a couple surgeons and executives paid to the tune of $10mil/year, but I’m pretty sure the above factors are pretty significant.

          1. Everywhere in the world the basic problem is that we are trying to deliver Twenty-first century health care with institutions designed in the Nineteenth century.

  3. I also wondered if this could be used as a circular saw, in a stationary version. Talk about paper cuts!

    A stationary version with a shield or something would also make it safer to use. And more expensive of course.

    1. You power it by linear motion. For powering a saw the conversion from linear to rotational motion is not necessary. The traditional pull saw does quite a good job as a manually powered saw. The principle of the circular saw is only superior, if you happen to have a rotary drive (motor) – and bearings of some sort.

      1. The way they were doing it would spray their coworker instead. But it would be easy enough to enclose that in a cardboard box or something, with just a hole for the string to come out.

    1. “Reminds me of ”

      gee I wonder why

      “Incidentally, [Manu Prakash] is a coauthor of this paper. He’s one of the Standford guys that brought us the $1 folding paper microscope a while back.”

      “Now, if I could just find that link. ..”

      Scroll up….

  4. Think of a mechanism that looks like letter H, but the vertical bars are articulated, and the horizontal one is fixed. Connect the string ends to the top ends of the vertical bars. Moving the bottom ends of the H (using cams on a shaft), will provide the hands like motion needed to operate the device. With a long enough shaft, you can power several devices. The shaft can be rotated by foot or connected to a bike, engine, wind powered turbine, etc.

  5. “Although there is a lot of discussion about health care problems in big countries like the United States, we often don’t realize that this is a “first world” problem. In many places, obtaining health care of any kind can be a major problem.”

    No. I’m pretty sure that almost all of us are quite aware that in the developed world we have it better than people elsewhere. You don’t have to tell us that. This statement actually demonstrates exactly why I hate the term ‘first world problem’. It implies that things aren’t really problems. Sure.. if you are talking about some suburban teenager feeling all angsty about the tags on his/her clothing while somewhere else people can’t even get clean water you have a point.

    Healthcare however is something that I think anyone who isn’t some kind of monster should want everyone everywhere to have access to the best that is humanly possible. While we certainly have health care that is world’s better from what people get in the third world our healthcare system is still a broken beaurocracy that is costing people their health and even lives right now as we type. We should demand and strive for better both for people in ‘developing countries’ AND for ourselves!

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