Centrifuging a blood sample without electricity is child’s play to a team of Stanford engineers. The researchers were inspired by a toy and developed paperfuge, a low-cost and low-tech centrifuge that could help diagnose diseases such as malaria and HIV in developing countries.
The centrifuge is an essential biomedical tool. When test tubes containing blood samples are placed in its rotating drum, the machine’s centrifugal force separates blood components into layers (red cells, plasma, and in some cases parasites). This is a crucial first step to test for diseases such as malaria, tuberculosis and HIV. However, in addition to being extremely expensive, centrifuges are bulky and require electricity to function. In some low-income countries, medical staff may lack the funds to acquire these devices or the reliable electrical grid required to power them.
A team of Stanford bioengineers found a way to turn 20 cents worth of craft supplies into a functioning centrifuge. In a recently published article, Manu Prakash and his team describe the simple device which they named ‘the paperfuge’. It only weighs two grams and consists of a paper disk, a string and handles. The paperfuge is powered by hand by pulling the looped string back and forth, as has been done for millennia by children using a toy known as ‘whirligig’.
The central component of the paperfuge actually consists of two separate paper disks. Tiny tubes of blood can be inserted between these disks, and pulling the strings makes the samples spin at up to 125 000 revolutions per minute, which allows the blood sample to separate.
“The simplicity of manufacturing our proposed device will enable immediate mass distribution of a solution urgently needed in the field. Ultimately, our present work serves as an example of frugal science: leveraging the complex physics of a simple toy for global health applications.”
The current paperfuge prototype has been proven effective to identify malaria in blood samples. The team is working to optimise the tool for other diseases. The paperfuge is cheap, requires no electricity and is easy to use and transport. This should facilitate its distribution and use in the areas that need it the most.