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

Dec 9, 2016
Originally published on December 12, 2016 3:01 pm

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.

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RACHEL MARTIN, HOST:

Scientists in Ireland have found a new use for a very familiar material.

(SOUNDBITE OF ADVERTISEMENT)

UNIDENTIFIED SINGERS: (Singing) Silly Putty. Silly Putty is fun for most everyone. Silly Putty is fun for most everyone.

MARTIN: It is fun - Silly Putty. I loved Silly Putty when I was a kid. I remember it came that little plastic egg. Apparently, if you mix silly putty with a special form of carbon, you can make an impressive kind of scientific instrument. NPR's Joe Palca explains how this big idea came about.

JOE PALCA, BYLINE: Silly Putty has some extraordinary properties. Jonathan Coleman is a physicist at Trinity College Dublin. He says, if you roll Silly Putty into a tight ball and throw it on the ground, it'll bounce.

JONATHAN COLEMAN: But if you pull it very, very slowly, it will flow as if it's a liquid, as if it's a viscous liquid.

PALCA: Industrial scientists first made Silly Putty about 70 years ago, but apart from selling it as a toy, nobody could really figure out what to do with it.

COLEMAN: It's got these strange properties, but it never really found an application. So we thought, you know, if we could make it do something, that'd be pretty cool.

PALCA: Coleman mainly works with another unusual material - a form of carbon called graphene. Graphene comes in sheets barely an atom thick, and it's an extremely good conductor of electricity. One of Coleman's students had the idea of mixing graphene with its electrical properties with Silly Putty and its strange bouncy, runny properties.

COLEMAN: And I thought, well, this might not go anywhere, but at the very least it'll be a good sort of tool to use for outreach - like, for talking to kids and getting them interested in science. So I said, great idea; let's do it.

PALCA: Turns out adding graphene turns Silly Putty into an electrical conductor that's extremely sensitive to pressure. Press on it just the tiniest amount, and you get a big and easy-to-measure change in its electrical resistance. To prove just how sensitive their pressure sensor was, Coleman says they decided to see if they could detect a spider walking across it.

COLEMAN: That turned out to be much easier said than done because spiders don't tend to want to do what you want them to do, so that took a lot of work.

PALCA: Ultimately, they were able to detect the spider's steps. The results appear in the journal Science. Besides detecting spiders, Coleman thinks the new sensor will have more practical uses. He's already shown it can be used to measure blood pressure just by placing it on someone's skin. And that's just the start.

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UNIDENTIFIED SINGERS: (Singing) So many silly things to do.

PALCA: Joe Palca, NPR News.

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UNIDENTIFIED SINGERS: (Singing) Silly Putty is fun for most everyone. Transcript provided by NPR, Copyright NPR.