Monday, January 23, 2017

Gee-haw, Spinner, Whirlygig, Whirlijig, Whirlyjig, Whirly = Centrifuge

Environmental and Science Education
by Edward Hessler

Have you ever made a whirligig from a button and string/yarn?

If not, you should, if only to feel the surging energy as you pull it back and forth. I still play with a couple I made several years ago. One is a single button model and the other is a two button model. I also have a much more more contemporary and dot-decorated model given to me by a friend who appreciated (indulged perhaps?) my interest in spinners of various kinds.

Whirligig [Wikimedia Commons]

It takes a person with an eye for how this toy might be adapted to solve a real life need. This is where Stanford University professor of bioengineering Manu Prakash stepped in. Prakash, a recent MacArthur Fellow, specializes in what he calls "frugal science."  And his inventions are known for their cleverness as well as their real use in daily life.

I've previously posted on a simple microscope Prakash and his group of frugal scientists/engineers invented.

While on a field trip to Uganda Prakash noticed a centrifuge not on a bench but on the floor. It was being used as a doorstop. There was no electricity to operate it. However, there was a need for one, a centrifuge that could be used anywhere—in hospital, in field, at the bench. Cheap. Simple. Repairable. Easily replaceable, if necessary.

Upon his return Prakash began by investigating spinning toys. One of these was the traditional button and string whirligig which led to the development of the "Paperfuge".  It was reported on by Madeline K. Sofia for NPR.

In this Stanford University press release you may learn more about how it is used. One might say that it is informed by a new "string theory." It includes a video of Professor Prakash at the controls as does Sofia's essay.

A few particulars about the paperfuge:

—Cost: 20 cents (American)
—rotational speeds of up to 125,000 rpm
—30,000 Gs
—1.5 minutes to separate blood into its components

If you are interested in the physics of rotation, this book published by Scientific American (SA) is wonderful. It consists of columns from the Everyday Scientist series published by SA.  Alas, there is nothing on the whirligig which I suspect has some interesting physics. It also shows the kinds of things that scientists become interested in, e.g., the one on tops is by a mathematical scientist.

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