Saving lives with a salad spinner

Saving lives with a salad spinner
Rice University students Lauren Theis, left, and Lila Kerr with their Sally Centrifuge constructed from a salad spinner
Rice University students Lauren Theis, left, and Lila Kerr with their Sally Centrifuge constructed from a salad spinner
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The Sally Centrifuge
The Sally Centrifuge
Rice University students Lauren Theis, left, and Lila Kerr with their Sally Centrifuge constructed from a salad spinner
Rice University students Lauren Theis, left, and Lila Kerr with their Sally Centrifuge constructed from a salad spinner

Like test tubes and Bunsen burners, the centrifuge is a standard piece of equipment in scientific and medical labs the world over. But what happens when there’s no lab to speak of? In developing and third world countries access to centrifuges, not to mention the power to drive them, can make separating blood to diagnose a range of diseases a difficult task. Now a pair of university students have come up with the ingenious idea of turning the humble salad spinner into a rudimentary centrifuge that could be used in medical clinics in developing countries around the world.

As part of a global health initiative at Rice University to bring new ideas and technologies to underdeveloped countries, Rice sophomore Lila Kerr and freshman Lauren Theis were asked to find a way to low cost, portable way to diagnose anemia without power. They found that a salad spinner met those criteria. Using plastic lids, cut-up combs, yogurt containers and a hot-glue gun they were able to construct a centrifuge that costs about US$30 in parts, including the spinner.

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," said Maria Oden, professor in the practice of engineering education and director of Rice’s Oshman Engineering Design Kitchen (OEDK).

Kerr says the push-pump spinner rotates tubes at up to 950 rpm, which compares 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, named in honor of a landmark known as the Sallyport on the Rice campus, has other advantages:

  • It requires no electricity - just a bit of muscle. "We've pumped it for 20 minutes with no problem," Theis said. "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 said. "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."

To put the device to the test Kerr and Theis will take their Sally Centrifuge abroad for nearly two months this summer as part of Rice’s Beyond Traditional Borders (BTB) initiative. Kerr will take a spinner to Ecuador in late May, while Theis will take one to Swaziland in early June and a third BTB team will take one to Malawi, also in June. The students expect to continue work on the device after their summer treks.

Obviously batteries are a limited solution in areas with no infrastructure.
I\'d guess improved gearing might yield higher RPM.
See the Vortex Hand Crank Blender
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Now that\'s \'thinking outside the box\'. This is in the same vein as that cheap wheelchair built from inexpensive metal conduit, bicycle wheels and a plastic chair.
It\'s more of a 19th Century approach, \"What can I build to do the job, starting with items already available that if modified just so...\"
Almost steampunk style, but without all the brass, copper, leather and cast iron. ;)
I do this quite often, take some item that close to what I need, saw this off, mill a slot here, turn another bit on one of my lathes. Saves tons of time when some factory has produced and item that already has some parts close to what I need.
I can\'t imagine how the spinner \"compares favorably\" with the battery-powered unit. It runs at less than 1/10 of the RPMs, and since centrifugal force varies by the square of the speed, that means it generates less than 1/100 of the G-force.
I\'m thinking something pedal-powered would be better. A lot more force available from the legs than the arms. Probably something similar to the human-powered washing machine reported here a little while back. Pedal a bicycle out to wherever you need to do your tests, prop the bike up on an axle-mounted centerstand (a simple, bent strip of steel), drop a spinner onto the rear tire and pedal hard. Rough mental calculations tell me such a setup could produce over 700 Gs of force. Still only about 1/6th of what the ZIPocrit produces, but it has to be better than this spinner.
John Graven
You go girls I think they need to be in the good thinking category
This idea fails to appreciate physician resistance to depending upon a school project by a couple of ninny undergraduates for anemia diagnosis. They will continue to guess from the paleness of the underside of the eye membranes. Outfit an IPhone as a pulse oximeter, spectograph, electrostethoscope, intelligent EKG, otoscope/rhinoscope--all just as easy to do, put it in nice leather cases, and you\'ll have a sale.
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Nothing new here. Salad spinners were being used as cheap laboratory centrifuges as far back as the 1980\'s during the early years of DNA research and the Human Genome Project.