Portable Centrifuge

Sometimes the solution to a problem comes not from “new tech” but from “old toys” that are repurposed in new ways. Here’s one great example.

Envision a cardboard disk with two holes — one on either side of the center point. Thread a piece of string through each hole, pull on the ends, and voila! You have a whirligig, versions of which have been found in archaeological digs dating as early as 3000 BC. But it turns out that, with a few modifications, this simple child’s toy can be turned into an inexpensive, portable medical centrifuge that can be used by healthcare workers in underdeveloped areas to carry out diagnostic tests.

Short lengths of drinking straw are used as receptacles for the blood to be centrifuged, two of which are glued to opposing radii and sandwiched between two cardboard disks. The string is replaced with fishing line attached to two wooden or plastic handles. The resulting device (dubbed a “paperfuge”) spins at more than 300 revolutions per second, generating a centrifugal force 10,000 times that of gravity. That’s enough to separate plasma from corpuscles in less than two minutes. Spinning for longer periods (about 15 minutes) will even separate red corpuscles from white corpuscles to enable testing for diseases like malaria.

In 2014, the same inventor unveiled a microscope made from a piece of paper and a small spherical lens. Known as the “foldscope,” more than 50,000 have already been distributed in 135 countries, and he plans to ship a million more by the end of the year. In combination, the two devices will make it possible to separate biological samples and analyze them under a microscope for less than a couple of dollars.