Graphene-Infused Silly Putty Can Detect Movements as Subtle as Spider Footsteps

Millions of children have played with Silly Putty, a toy made from viscous silicate polymers that can be moulded, stretched, and bounced off walls. But this common product also has a long history of moonlighting in a wide variety of scientific projects, from helping the Apollo 8 crew keep their tools in place in zero gravity, to polishing telescope mirrors at the University of Arizona's Steward Observatory.

Now, research published Thursday in the journal Science has identified yet another promising application for Silly Putty—this time, as a precision sensor nicknamed "G-putty." The "G" stands for graphene, a two-dimensional "wonder material" made from latticed carbon atoms that has extraordinary properties, including strength, conductivity, and flexibility.

State of the art sensors using graphene and silly putty. Video: AMBER Centre/YouTube

Led by Jonathan Coleman, a nanotechnology expert based at the Advanced Materials and BioEngineering Research (AMBER) center at Trinity College Dublin, the study's authors embedded flexible graphene nanosheets into Silly Putty to test out the combined composite's capabilities. They discovered that the G-putty showed "unprecedented sensitivity" to the slightest movements, and can "measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider," according to the paper.

"What we did was put graphene into this polymer and we found we got a composite with very unusual physical properties," Coleman said in a video explainer about the new study. "Electrically, the composite became conductive, but mechanically, it was still this squashy, squidgy material."

READ MORE: Inside Graphene City, Birthplace of a Wonder Material

When the deformability of putty and the conductivity of graphene join forces, the resulting material is around 250 times more sensitive than a standard strain gauge. (These devices detect and measure strain on an object, like this OMEGA-built commercial gauge.)

This composite may have implications for many fields, but the team highlights medical technology in particular. "The G-putty would probably be incorporated in a device which would be worn on the wrist," Coleman told me over email. "This would measure the resistance change in the G-putty in response to the pulse. It would send the data by Bluetooth to a smartphone where an app would do data processing and output heart rate and, importantly, blood pressure."

Given its ability to continuously keep tabs on these vitals, G-putty could be a helpful tool for monitoring a patient's condition over extended periods of time.

"It really shows the power of nanomaterials," Coleman said. "A small amount of nano can really turn the ordinary into something extraordinary."

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