A modern medical breakthrough allows people to create their own centrifuge for spinning down blood, for twenty cents.
The device is a simple cardboard disk that produces incredible results. By poking two holes near the center and running two threads through them, you can pull the strings to tighten and wildly spin the disk. As the strings relax, it spins frenetically in the other direction.
For millennia, it has been used as a children's toy. Now, it has medical applications in places that do not have access to electrified, heavy or expensive centrifuges.
The result, developed by Manu Prakash and his colleagues at Stanford University, spins at over 300 revolutions per second and generates a centrifugal force 10,000 times that of gravity. The power is used to remove debris from blood when cleaning it for testing.