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Stanford bioengineers develop a 20-cent, hand-powered blood centrifuge

Inspired by a whirligig toy, Stanford bioengineering professor Manu Prakash, PhD, and his students have designed a centrifuge from paper, twine and plastic that can separate blood plasma from red cells in 1.5 minutes, no electricity required. Called a “paperfuge,” it spins at 125,000 revolutions per minute and exerts centrifugal forces of 30,000 Gs.

The head-spinning physics behind this clever device were just published in Nature Biomedical Engineering. You can watch the device in action above or read more in this Stanford release.

A little over a year ago, Prakash began brainstorming with postdoctoral scholar Saad Bhamla, PhD, on ideas for an ultra-low cost centrifuge that could be used for disease diagnostics in poor, off-the-electrical-grid regions. (Centrifugation and concentration of blood-borne pathogens is a critical first step for the detection of diseases such as malaria, African sleeping sickness and tuberculosis.)

After weeks of exploring ways to convert human energy into spinning forces, they began focusing on toys invented before the industrial age — yo-yos, tops and whirligigs.

“One night I was playing with a button and string, and out of curiosity, I set up a high-speed camera to see how fast a button whirligig would spin. I couldn’t believe my eyes,” said Bhamla, when he discovered that the whirring button was rotating at 10,000 to 15,000 rpms.

Next, Prakash and Bhamla assembled a team of undergraduate students to build computer models, optimize prototypes and improve device safety. Before long they clocked one of their prototypes at 125,000 revolutions per minute. Prakash believes that this may be the fastest spinning object driven by human power, and he has submitted the design to the Guinness World Records organization.

“From a technical spec point-of-view, we can match centrifuges that cost from $1,000 to $5,000,” said Prakash.

The paperfuge is the third invention from the Prakash lab driven by a frugal design philosophy, where engineers rethink traditional medical tools to lower costs and bring scientific capabilities out of the lab, and into hands of health-care workers in resource-poor areas.

The first was the Foldscope, a fully functional, under-a-dollar paper microscope that can be used for diagnosing blood-borne diseases. (To date there are 50,000 foldscopes in the hands of people around the world, and a spinoff company recently launched a Kickstarter campaign to ship 1 million more.) The second was a $5 programmable kid’s chemistry set, inspired by hand-crank music boxes, which enables the execution of precise chemical assays in the field.

Prakash’s dream is that these tools will enable health workers, field ecologists and children in the most remote areas of the world to carry a complete laboratory in a backpack.

Previously: Stanford bioengineer Manu Prakash named a MacArthur Fellow, Music box inspires a chemistry set for kids and scientists in developing countries, Free DIY microscope kits to citizen scientists with inspiring project ideas and Stanford bioengineer develops a 50-cent paper microscope
Photo in thumbnail by Kurt Hickman

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