The paperfuge alternative to the centrifuge


The centrifuge is a vital tool in medical diagnostics because it enables laboratories to separate different components that are mixed in a sample. It works by spinning the sample around at very high rotational frequencies and the differential centrifugal forces on the different masses results in the separation. But centrifuges are bulky and expensive and require electricity to operate and that makes them not easily available to medical personnel in remote areas.

But a team of researchers at Stanford University has come up with a cheap alternative based on a common spinning toy that uses paper and string and costs about 20 cents. A paper in the journal Nature describes how it works and this more general article explains how the researchers arrived at their solution to the problem.

Inspired by the design of a millennia-old toy, the Paperfuge is a hand-powered centrifuge made of paper, string, and plastic that can whip biological samples in circles at up to 125,000 rpm. That’s enough oomph to separate plasma from a blood sample (a standard diagnostic procedure) in 90 seconds. For reference, a StatSpin MP centrifuge—the kind of commercial centrifuge that you’ll find in diagnostic and research labs around the world—tops out at 15,800 rpm and can take up to two minutes to perform a plasma separation.

The StatSpin also weighs 5.5 pounds, requires electricity, and costs thousands of dollars. The Paperfuge weighs about 2 grams and costs less than a quarter to make. That is—and this is the scientific term—freaking ridiculous.

As the team leader Manu Prakash says:

“There are a billion people on this planet who live with no electricity, no infrastructure, no roads, and they have the same kind of health care needs that you and I have,” Prakash says. His lab developed the Paperfuge with these people in mind.

Now people are just starting to get access to Paperfuges. “This is a great example of how extremely creative people can originate important new ideas by relaxing and observing the world around them,” says Ray Baughman, Director of the NanoTech Institute at the University of Texas in Dallas, who was unaffiliated with the research. (His lab figured out that you can build artificial muscles by supercoiling fishing line like the strings on the Paperfuge.) “And the application of the described technology for resource-limited parts of the world might provide enormous human health benefits.”

Prakash and Bhamla think so, too. The pair recently returned from a trip to Madagascar, where they’ve been coordinating with local healthcare workers on testing the Paperfuge in the field. “The first people we met with, I thought they would laugh at me when I showed it to them,” Bhamla says. He was wrong. He remembers one woman, in particular, a diagnostic technician of fifteen years, who specializes in malaria. “She told us: You think you know. You think you understand the need for this tool. But you don’t understand it like I do. I’ve been looking for something like this for years.”

In the past, she told him, transporting centrifuges to remote villages required Jeeps to haul them there and generators to power them. Now all she needed were her pockets.

As I’ve said before, you’ve got to hand it to engineers. Their ability to come up with ingenious solutions to important practical problems is amazing.

Comments

  1. OverlappingMagisteria says

    You also gotta hand it to marketers! They figure out how to sell, basically, an electric motor with a place to put test tubes for thousands of dollars! I’d say half that cost went into coming up with the name “StatSpin MP”.

    (I admit my ignorance when it comes to medical technology. If anyone can set me straight on why a machine that just spins things costs thousands, I would be very interested!)

  2. Dave X says

    The paper has the details: two R=50mm disks stuck together with velcro, sandwiching 2 epoxy-capped soda-straw chambers, with 2x 3mm holes spaced 2.5mm apart on an acrylic button, and braided fishing line with two PVC or wood handles.

  3. DonDueed says

    What a terrific invention!

    Thanks for the hat tip to engineers, too, Mano. It seems we get a good bit of grief around here sometimes, thanks to a (I hope) small fraction of us who hold, shall we say, unusual opinions about human origins and other such subjects.

  4. Brian English says

    DonDueed, unfortunately, engineers suffer from the common human failing that because they are expert in one small field, their ideas are exper in others.

    There’s a Senator in Australia who’s an engineer and he thinks Global warming is bunk. Hilariously (well it would be hilarious), his argument against global warming is an argument for (a type of) global warming. He just doesn’t follow the argument through. (Basically, he says there can’t be global warming because the atmosphere cools of the planet. And stops there. Unless he thinks the warmer atmosphere sheds that heat it obtained by calling the planet, then he must admit the atmosphere is warmer, and so, global warming. It’s not how I understand global warming, CO2 and other gases trapping reflected infra-red energy, but my gloss is probably wrong too.