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Team builds centrifuge for $30

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A simple salad spinner is the basis for a centrifuge that can be used to separate blood in resource-poor settings without access to electricity. When tiny capillary tubes that contain about 15 microliters of blood are spun in the device for 10 minutes, the blood separates into heavier red blood cells and lighter plasma. The hematocrit, measured with a gauge held up to the tube, can tell clinicians if a patient is anemic. (Credit: Jeff Fitlow)

RICE (US)—A group of college students has turned a salad spinner into a rudimentary centrifuge that medical clinics in developing countries could use to manually separate blood without electricity. They built it for about $30—including the spinner—using plastic lids, cut-up combs, yogurt containers, and a hot-glue gun.

This summer Rice University sophomore Lila Kerr will take one to Ecuador and freshman Lauren Theis will take one to Swaziland. Another team member will take one to Malawi to field test the device, named the Sally Centrifuge. The students expect to continue work on it after their summer treks.

The centrifuge was designed as a project for a global health class. The students were asked to develop an inexpensive, portable tool that could diagnose anemia without access to electricity.

They found that a salad spinner met those criteria. When tiny capillary tubes that contain about 15 microliters of blood are spun in the device for 10 minutes, the blood separates into heavier red blood cells and lighter plasma. The hematocrit, or ratio of red blood cells to the total volume, measured with a gauge held up to the tube, can tell clinicians if a patient is anemic. That detail is critical for diagnosing malnutrition, tuberculosis, HIV/AIDS, and malaria.

“Many of the patients seen in developing world clinics are anemic, and it’s a severe health problem. Being able to diagnose it with no power, with a device that’s extremely lightweight, is very valuable,” says Rice University engineering education professor Maria Oden.

Kerr says the device spins tubes at up to 950 rpm. Results with the push-pump spinner compare favorably to those obtained with the ZIPocrit, a miniature, battery-powered centrifuge used as part of Rice’s Lab-in-a-Backpack project. The ZIPocrit spins up to 10,000 rpm and completes its task in four to five minutes.

But the manual Sally Centrifuge has other advantages:

  • It requires no electricity—just a bit of muscle. “We’ve pumped it for 20 minutes with no problem,” Theis says. “Ten minutes is a breeze.”
  • It can spin up to 30 tubes at a time versus the ZIPocrit’s maximum of four.
  • It has proven to be fairly robust. “It’s all plastic and pretty durable,” Kerr says. “We haven’t brought it overseas yet, of course, but we’ve trekked it back and forth across campus in our backpacks and grocery bags and it’s held up fine.”

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