A cardboard centrifuge separates blood cells from plasma

TAKE a cardboard disc and punch two holes in it, close to, and on either side of, its centre. Thread a piece of string through each hole. Now, pull on each end of the strings and the disc will spin frenetically—first in one direction as the strings wind around each other, and then in the other, as they unwind.

Versions of this simple children’s whirligig have been found in archaeological digs on sites across the world, from the Indus Valley to the Americas, with the oldest examples dating back to 3,300BC. Now Manu Prakash and his colleagues at Stanford University have, with a few nifty modifications, turned the toy into a cheap, lightweight medical centrifuge. They report their work this week in Nature Biomedical Engineering.

Centrifuges’ many uses include the separation of medical samples (of blood, urine, sputum and stool) for analysis. Tests to spot HIV, malaria and tuberculosis, in particular, require samples to be spun to clear them of cellular debris. Commercial centrifuges, however, are heavy and require power to run. That makes them impractical…Continue reading
Source: Economist