And it costs 20 cents apiece to make more of them.
Nearly 1.3 billion people don't have access to electricity. The lack of sockets in neglected parts of the world, including swaths of India and sub-Saharan Africa, is a frustration to medical aid workers, as many basic lab tools require electricity.
This is one reason why researchers at Stanford University recently developed a portable, cheap and hand-powered centrifuge. The devices use a whirling acceleration motion to separate the elements of blood or urine samples by density to get them microscope-ready to detect pathogens. The Stanford tool, developed by a team lead by assistant professor of bioengineering Manu Prakash, is made of mostly paper and takes the basic form of a spinning button whirligig, an ancient and simple toy made of thread looped through two holes in a button. The user pulls at the loop ends, coiling and uncoiling the thread to make the button spin.
"Some call it a whirligig," Prakash says. "Some call it a buzzer or a run-run." The mechanism "is found in artifacts that are 5,000 years old," he adds. "The motion creates inertia that acts as an isolator."
By adding a chamber for a substance sample, Prakash and his team created a human-powered centrifuge. Their "paperfuges" cost about 20 cents to produce and separate blood components as efficiently as electric ones costing hundreds or thousands of dollars, according to a study they published in Nature Biomedical Engineering.
Prakash says he tried devices modeled after egg beaters and salad spinners but the whirligig creates the fastest, easiest acceleration. It only takes 90 seconds to get blood separated into individual components: red cells, plasma and possibly parasites. The device can be used to help detect malaria, African sleeping sickness, HIV, and tuberculosis.
He said it could be part of a low-cost toolkit for aid workers, one that could be provided easily by cash-strapped nonprofits and aid missions and schlepped across the deserts, mountains, and vast cityscapes where some of the most in-need people are cloistered. Prakash's lab has also produced the foldscope, a paper microscope that costs less than $1, as well as a $5 chemistry set.
M. Saad Bhamla, a postdoctoral researcher at Stanford who worked on the project, says the paperfuge was inspired by recent fieldwork he and Prakash completed in Madagascar.
"We took a bus ride on dirt roads to hike six hours to get to a village," Bhamla recalls. It would have been impossible to cart typical medical resources to such a place. He noted this was not strictly a third-world problem; there are inhabited areas of Alaska just as remote. "We had to ask ourselves," Bhamla adds, "what tools could go that last mile in healthcare diagnostics."