A new paper centrifuge costs less than 15 rubles

Julia Korowski, XX2 century

Scientists at Stanford University have turned a children's toy buzzer into a centrifuge that can be used in the laboratory for blood tests. This device does not need electricity, costs only 20 cents and can replace expensive equipment in the poorest African countries. The results of the work are published in the journal Nature Biomedical Engineering (Bhamla et al., Hand-powered ultralow-cost paper centrifuge).

Manu Prakash was born in India. As a child, he loved to play with a buzzer – a simple device that can be made from ordinary thread and buttons. If you stretch the thread in such a way that loops form, take hold of them and twist the knot, and then spread your hands, the toy will begin to unwind, making a characteristic sound. It is unlikely that he could have imagined then that one day he would write an article in a scientific journal about how to use a buzzer in the laboratory.

Prakash took up this project after he went on a research trip to Uganda in 2013. Visiting hospitals, he noticed that in most of them there were no working centrifuges or electricity, and therefore doctors could not separate the blood into components and make even the simplest tests. "In one clinic, a door was propped up with a broken centrifuge," Prakash says. – When we returned from Africa, we asked ourselves: is it possible to carry out centrifugation without electricity, on human traction?"

Other scientists have already asked the same question. They developed inexpensive centrifuges based on salad drying devices and egg churning machines, but these devices accelerated only to 1200 revolutions per minute and processed samples for too long. Prakash and his colleagues approached the issue very seriously and in an organized manner: they went to the store, bought a dozen rotating toys of various shapes and sizes – from yo-yo to wrist expanders – and filmed them with a high-speed camera to find out who is the fastest in the world. The yo-yos turned out to be too slow, but the buzzer rotated at a speed of up to 10,000 rpm, which is comparable to the performance of a real centrifuge.

Scientists have studied the mechanics of the toy's movement and described it mathematically. It turned out that the high speed of rotation can be achieved mainly by twisting the ropes into tight spirals. "Twisting and unwinding, these threads demonstrate an interesting principle of over–spiralization," explains Prakash. Having understood the mechanism of the "buzzer", scientists were able to increase the speed of rotation of the disk to 125,000 rpm. Then they constructed a device called "paperfuge" (literally, "paperfuge"), consisting of two cardboard discs, fishing line, drinking straws sealed on one side and wooden handles. The principle of operation is very simple: test tubes with blood are inserted into the straw holders on one of the disks, covered with another disk, the buttons are snapped and the device is set in motion. During the experiments, scientists managed to isolate blood plasma in less than a minute and a half, and it took 15 minutes to isolate malaria parasites from samples. Loaded with samples, the device developed a speed of up to 20,000 rpm.

"These are promising results," says Muhammad Zaman, a biomedical engineer at Boston University, who was not involved in the study. "They impressed me very much because they are based on strong theory and simulation... and besides, they have wide application." Zaman notes that now the paper centrifuge will have to be tested in the field. Prakash cooperates with the non-profit organization PIVOT Works, Inc., which provides qualified medical care to residents of Madagascar. Together they will conduct clinical studies and find out how easy the devices are to handle, durable and reliable compared to conventional centrifuges. The price of medical devices sometimes reaches up to $ 6,000, and a paper "toy" costs only 20 cents (about 12 rubles), so we can hope that poor countries will still be interested in the development.

Portal "Eternal youth" http://vechnayamolodost.ru  12.01.2017