The 20-cent medical device

Inspired by an old toy, the Paperfuge is a low-cost take on a critical medical device.

A typical blood centrifuge is essential to any healthcare centre that aims to test for diseases such as malaria, African sleeping sickness, HIV and tuberculosis. But in developing areas where these diseases are most prolific, healthcare centres do not always have the infrastructure or money to run and maintain the bulky, electricity-dependent device. Enter, Stanford University researchers Manu Prakash and Saad Bhamla. Inspired by a whirligig toy, the bioengineers created a low-cost, hand-powered blood centrifuge.

The whirligig toy is built by threading a loop of twine through two holes in a button. When the loop ends are rhythmically pulled, the twine coils and uncoils, spinning the button at a dizzying speed. Using the same principles, the researchers used 20 cents worth of paper, twine and plastic to create centrifuge that separates blood into its individual components in only 1.5 minutes.

Dubbed the “Paperfuge”, it can spin at speeds of 125,000 rpm and exert centrifugal forces of 30,000 Gs.

“There are more than a billion people around the world who have no infrastructure, no roads, no electricity. I realised that if we wanted to solve a critical problem like malaria diagnosis, we needed to design a human-powered centrifuge that costs less than a cup of coffee,” said Prakash.

The diagnostic tool was also created with the help of complex mathematics. According to Bhamla, a team of undergraduate engineering students from MIT created a mathematical model for how the whirligig toy works, which led to the creation of a computer simulation. The students were able to help create a working prototype.

“There are some beautiful mathematics hidden inside this object,” Prakash said. “From a technical spec point of view, we can match centrifuges that cost from $1000 to $5000.”

Prakash is also behind the Foldscope, a fully functional, under-a-dollar paper microscope, and $5 programmable kid’s chemistry set. His lab is driven by a frugal design philosophy, where engineers rethink traditional medical tools to lower costs.

“Frugal science is about democratising scientific tools to get them out to people around the world,” Prakash added.