The Paperfuge, like the piece of lab equipment it’s named for, the centrifuge, can spin biological samples at thousands of revolutions per minute. That’s a critical step in the diagnosis of infections like malaria and HIV. But unlike a centrifuge, the Paperfuge doesn’t need electricity, complicated machinery, expensive replacement parts, or even much money to operate.
The breakthrough came at the beginning of 2016, when Saad Bhamla (a postdoc in Prakash’s lab, and by his own admission a lousy yo-yoer) decided to analyze the spin of a toy from his childhood in India, called a whirligig. The design dates back thousands of years: Suspend a button or disc on a loop of string, and pull the looped ends to set the button spinning. Successive rounds of pulling cause the string to wind and unwind and the button to spin quickly in one direction and then another. (Turns out that even though lab-grade centrifuges spin up, whirl in the same direction, and then spin down, you can get the same results with something that spins one way, stops, and then spins back.)
“It’s a simple design, so one night, I made one myself. My girlfriend lent me a thread from her sewing kit and I strung it through a button,” Bhamla says. He positioned the toy in front of a high speed camera and started spinning. “Later, when I analyzed the footage, I realized that the button was spinning between 10,000 and 15,000 rpms. I remember feeling that this was it, this was what we’d been looking for.”
Manu Prakash is no stranger to innovative paper technology. In 2012 he unveiled the Foldscope, a folding paper microscope, inspired by origami, that costs less than dollar to produce and is powerful enough to see microorganisms.