The Powerful Mechanics of an Old Toy for Medical Diagnostics to Help Underdeveloped Countries

Reaching out for medical diagnostics, a group of researchers at Stanford  found a way to innovate the current medical machine called a blood centrifuge in a low-cost yet powerful hand-powered device to accurately make a diagnosis for patients. Most especially made to improve medical diagnosis in underdeveloped countries, the team focused on its ability to be cost-effective, portable, human-powered, and also high-speed spinning. In contrast to the bulky medical instruments that needs electricity to operate, the “paperfuge” weighs about 2 grams, costs 20 cents, does not need electricity, and spins up to a speed of 125,000 rounds per minute to accurately diagnose a blood test.

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The paper centrifuge, also known as “paperfuge”, is an inspiration from an old toy called whirligig. Whirligig is a spinning toy in which strands of strings need to be expanded and contracted to enable the spinning mechanism. The user will only have to manipulate the braided strings on both ends in order for the button at the center to spin in rapid speed. The simple pull and release mechanical principle is what made the whirligig a potential alternative for a centrifuge. And this is the idea that pushed the Stanford bioengineers to develop it as a blood centrifuge. This same technology has been used widely in various projector technology by companies like Elitescreens. 

Like most researchers, at first, the proponents didn’t know how the mechanical toy works. With that, they devoted a lot of time and effort in learning the mathematical part of the whirligig. In this case, a normal whirligig runs at a speed of 10,000 – 15,000 rounds per minute. With its improved physical aspects, they had discovered that it is the fastest mechanical tool without the use of electricity or power, which can spin at 125,000 rounds per minute and has an  inertial force at the rotational axis of 30,000Gs.The said speed is exactly what they need for the development of a low-cost centrifuge, but is accurately functional for the diagnosis of blood samples.

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To conduct experiments, the researchers attach the blood samples at a sealed straw and strap them at the centrifuge or paper disk. With this, they were able to prove a complete separation of plasma from the red blood cells, which only took 1.5 minutes to complete. The reading for the red blood cells is helpful in giving hematocrit value for anemia diagnosing. Not only this, but they were able to identify disease-causing malaria and the African trypanosomiasis for just 15 minutes of using the “paperfuge”.

Following the objectives that they have to consider, the researchers made a centrifuge with the use of only paper and plastic. With the use of 2 paper discs, strong fishing lines, wood, plastic straws, and Velcro straps, the researchers were able to make a prototype for their testing phase. In addition, they also considered the wear-and–tear property of the paperdisc, which is why they placed acrylic ovals that were taped on the holes of each disc.

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However, the possibility of blood exposure is high, especially with these materials. That is why the researchers made it a point to use only a shatterproof plastic and seal the straws perfectly to avoid leakage.

This research is useful in underdeveloped countries where medical attention is hard to give. With that, the researchers included a test with health workers in Madagascar for clinical validation.

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