A piece of paper, some twine and plastic could make testing for certain diseases more accessible even in the poorest areas of developing nations. Manu Prakash, an assistant professor of bioengineering at Stanford University, used those materials to create a simple centrifuge alternative that he calls the "paperfuge." Centrifuges are rapidly rotating machines in the lab that scientists use to separate the different components of a liquid by density. If you want to test for diseases like African sleeping sickness, malaria, tuberculosis or even HIV, that liquid is blood. Heavy red blood cells settle at the bottom, plasma floats to the top, while parasites and pathogens occupy the middle part. The machine is effective, but it's also expensive and needs electricity to work.