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Adding A Funny Form Of Carbon To Silly Putty Creates A Heart Monitor

Jonathan Coleman and his son compare graphene-infused Silly Putty (left) with the unadulterated kids stuff.
Naoise Culhane
Amber Center, Trinity College Dublin
Jonathan Coleman and his son compare graphene-infused Silly Putty (left) with the unadulterated kids stuff.

Scientists in Ireland are using a rather unexpected material to make an extremely sensitive pressure detector: Silly Putty.

The Irish researchers combined the kids' plaything with a special form of carbon, and came up with a remarkable new material — one they think could someday be useful in making medical devices.

Physicist Jonathan Coleman, at Trinity College, Dublin, says Silly Putty has some extraordinary properties. If you roll the stuff into a tight ball and throw it on the ground, it'll bounce. "But if you pull it very, very slowly, it will flow as if it's a liquid, a viscous liquid," he says.

That's why you have to put Silly Putty back in its plastic egg when you're done playing with it. If you don't, it'll flow into the carpet and you'll never get it out, as many frustrated parents have discovered.

Industrial scientists came up with the formula for Silly Putty about 70 years ago. They were looking for synthetic substitutes for rubber. It's basically a mixture of boric acid and silicone oil. But apart from turning it into a toy, nobody could really figure out what to do with it.

"It's got these strange properties but it never really found an application. So we thought, if we could make it do something, that would be cool," says Coleman.

Coleman mainly works with another unusual material, a remarkable form of carbon called graphene. Graphene comes in sheets barely an atom thick and is extremely good at conducting electricity.

One of his students had this funny idea: What if we mix graphene, with its electrical properties, with the Silly Putty and its strange bouncy, runny properties.

Turns out making a composite material using graphene and Silly Putty gives you a new material that is still runny and bouncy, but now conducts electricity and is extremely sensitive to pressure. Press on it just the tiniest amount, and you change its electrical resistance.

Coleman thinks there will be many applications for his new material. For example, he has shown that if you press a small blob of it against someone's carotid artery, you can measure not only the pulse but also blood pressure.

The research findings were published online Thursday by the journal Science.

Copyright 2020 NPR. To see more, visit https://www.npr.org.

Joe Palca
Joe Palca is a science correspondent for NPR. Since joining NPR in 1992, Palca has covered a range of science topics — everything from biomedical research to astronomy. He is currently focused on the eponymous series, "Joe's Big Idea." Stories in the series explore the minds and motivations of scientists and inventors. Palca is also the founder of NPR Scicommers – A science communication collective.