Researchers from Stanford University have developed a hand-spun centrifuge mainly made out of paper. The Centrifuge is extremely light and costs just 20 cents. The simple device inspired by an ancient children's toy is named “paperfuge”. This low cost and power free centrifuge can detect malaria in blood in a mere 15 minutes.
How does a centrifuge work?
A centrifuge is a device used in clinics, hospitals and laboratories across the globe. It separates fluids, such as blood, into different components by spinning the specimen. With the impact of the high-speed spin, centrifugal forces push denser material outwards. The centrifuge is used to separate cell, subcellular organelles, proteins, viruses, and nucleic acids.
Centrifuges are vital in poor regions where tropical diseases are common. However, they are not always available due to their high cost, weight and electricity needs. This makes it difficult for point-of-care practitioners to help their patients.
In order to overcome this problem, a team of researchers led by Manu Prakash from Stanford University has developed a hand-spun paper centrifuge. The initial designs consisted of salad spinners and manual egg beaters however both were unable to produce the necessary speeds. The final design, published in Nature Biomedical Engineering, was based on a buzzer toy (whirligig) which dates back to 3,300 BC. Slightly different devices were used in the colonial US, Indigenous North America, medieval Europe and ancient China.
A children's toy inspires a revolutionary device
The Paperfuge is operated by pulling a string that passes through the center and evidently spinning the circular disc. It operates according to the principles of “nonlinear oscillator”. The central disc rotates when a force is applied to the handle causing the strings to unwind. When the string is completely unwound, it begins to rewind; thus forming a super-coiled structure.
How effective is Paperfuge?
The Paperfuge is capable of reaching spinning speeds of 125,000 revolutions per minute (RPM). It exerts centrifugal forces equivalent to 30,000 g. Furthermore, its speed is considered the fastest rotational speed recorded in a human-powered device.
The capability of the device was tested on blood which needs to be separated into its different components when checking for diseases. The Paperfuge was able to centrifuge blood at approximately 20,000 RPM; a similar speed to conventional benchtop centrifuges. It was able to separate pure plasma from blood in under 90 seconds. But more importantly, it succeeded to isolate the malaria parasite in blood within approximately 15 minutes.
The Paperfuge's materials may vary. Researchers were able to construct the device from paper, wood and fishing wire. Another version was made out of polydimethylsiloxane (a common silicon-based organic polymer), plastic, and 3D-printed materials. This enables the device to be manufactured in bulk.
“The simplicity of manufacturing our proposed device will enable immediate mass distribution of a solution urgently needed in the field,” the authors concluded in their study. “Ultimately, our present work serves as an example of frugal science: leveraging the complex physics of a simple toy for global health applications.”
The Paperfuge was tried in Madagascar where the field test was conducted to determine the device's ease of use. The test prooved that the Paperfuge could be used by basically anyone, thus solving the centrifuge problem in rural areas.
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Written by Terry Berman