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Putty to Wear: Scientists 'Silly' Idea

Mixing graphene—a material made of single-atom-thick layers of carbon—with homemade “Silly Putty” produces a sensor so sensitive that it can detect the tiny footsteps of spiders, according to new research.

The enhanced putty, dubbed G-putty, can also detect some human vital signs, like pulse and breathing, suggesting it could one day be used for building wearable health trackers, according to the study. “We’re interested in the monitoring of human vital signs,” said Jonathan Coleman, a chemical physicist at the Advanced Materials and Bioengineering Research Center in Ireland who leads the work. “It’s looking pretty good as we start.”

Researchers are stretching the possibilities of polymers, breaking new ground in the field of composites with a combination of homemade "Silly Putty" and graphene that yields an extremely sensitive sensor. Photo: AMBER, Trinity College Dublin

Graphene is an especially appealing substance for building electronics because it is lightweight and flexible; it is hundreds of times as strong as steel; and it conducts electricity extremely well. In recent years, scientists at universities and in the private sector have shown interest in using it for commercial applications, like gas sensors, tennis rackets and microprocessors. International Business Machines Inc., Apple Inc., Saab AB and Lockheed Martin Corp. have sought or received graphene-related patents in the past.

The researchers have filed a patent for the G-putty technology and said they were in discussions with several companies interested in commercializing it, according to Dr. Coleman. He declined to name the potential partners.

The new composite material, described in a paper published Thursday in the journal Science, consists of a network of graphene flakes in silly putty made from a recipe found online. The addition of graphene makes the putty a good electrical conductor.

Dr. Coleman’s lab has a long tradition of incorporating household products into nanotechnology research. For instance, they have made graphene using a kitchen blender. The idea of mixing graphene with silly putty came from one of Dr. Coleman’s students. He greenlit the project, thinking it would be a good outreach tool. The material turned out to have unusual and interesting properties.

Silly Putty manufacturer Crayola didn’t respond to a request for comment.

To do their tests, the scientists hooked up their G-putty using wires to a recording device. When pressure is applied—by a spider’s walking or a heart’s pulsing—they showed G-putty’s resistance, or ability to conduct electricity, changed in a measurable way, giving scientists the “basis of a sensor,” according to Dr. Coleman. G-putty, he says, is about 10 times as sensitive as other similar technologies. (In a wearable, it would be connected to some sort of battery, he said.)

Robin Dolleman, a graphene researcher at Delft University of Technology in the Netherlands who wasn’t involved in the study, said the approach was simple and cost-effective, which “makes a strong case for real applications.”

Those might include activity trackers embedded in clothing or athletic equipment; pressure detectors for sealing kits, or systems that detect intruders, according to Peter Steeneken, a Delft University of Technology nanoscientist who also wasn’t involved in the creation of G-putty.

Before the material is ready for prime time, experiments are needed to determine whether G-putty’s sensitivity survives stressors like temperature changes over long periods of time, he added. It is possible that the graphene flakes could move inside the liquid-like putty in such a way that they stick together, reducing their electrical conductivity.