20-cent paper pinwheel helps diagnose diseases in developing countries

Researchers have used the technology behind a 5,000-year-old toy to create a cheap paper device that can separate blood and could could change how some diseases are diagnosed in the developing world. The device, called the paperfuge, mimics the workings of traditional centrifuges that are routinely used for diagnosing infections like HIV and malaria.

Centrifuges — machines that spin super fast and separate biological materials — can cost thousands of dollars and need electricity to function. That makes it hard for developing countries to afford them or operate them. And that’s why researchers led by Stanford University bioengineer Manu Prakash were looking for a cheap alternative.

They found inspiration in an ancient toy called the whirligig, or buzzer, which is made of a central disk and strings that wind and unwind. After analyzing how exactly the whirligig works and how fast it spins, Prakash created a similar device that could hold blood sample and works as a centrifuge.

The paperfuge is made of two paper disks holding tiny tubes of blood; strings run through the center of the disks and attach to wooden handles. The repeated winding and unwinding of the strings spins the disks super fast, allowing to separate blood from plasma in a short period of time. In fact, the paperfuge can spin blood at about 20,000 revolutions per minute — a speed comparable to that of traditional centrifuges. Because it costs only 20 cents to make and needs no electricity, the paperfuge could easily be used in developing countries. The invention was described in a study published today in Nature Biomedical Engineering.

The researchers tested the device and used it to isolate malaria parasites from blood in 15 minutes. Now, it needs to be tested in the field, where it could be a game changer for diagnostics in developing countries.