Researchers add graphene to silly putty to create sensors and medical devices

Researchers have used graphene to make the children’s toy Silly Putty conduct electricity, a development that could lead to extremely sensitive sensors.

The research, led by Prof Jonathan Coleman, Trinity College Dublin and in collaboration with Prof Robert Young of Manchester University, potentially offers applications in new, inexpensive devices and diagnostics in medicine and other sectors. The team’s findings have been published in the journal Science.

Prof Coleman from Trinity’s School of Physics along with postdoctoral researcher Conor Boland, discovered that the electrical resistance of putty (polysilicone) infused with graphene was extremely sensitive slight deformation or impact.

They mounted the so-called G-putty onto the chest and neck of human subjects and used it to measure breathing, pulse and blood pressure. According to Manchester University, it showed unprecedented sensitivity as a sensor for strain and pressure, hundreds of times more sensitive than current sensors.

The G-putty also works as a very sensitive impact sensor, able to detect the footsteps of small spiders. It is believed that this material will find applications in a range of medical devices.

Prof Young, Professor of Polymer Science and Technology said: “We have now developed a new high-performance sensing material, ‘G-putty’, that can monitor deformation, pressure and impact at a level of sensitivity that is so precise that it allows even the footsteps of small spiders to be monitored.

“It will have many future applications in sensors, particularly in the field of healthcare.”

The material was developed at Trinity College Dublin. The NGI contributed to the work through analysing the structure of the material. Manchester-based scientists were then able to develop a mathematical model of the deformation of the material to explain the effect of its structure upon its mechanical and electrical properties.

Prof Coleman said: “What we are excited about is the unexpected behaviour we found when we added graphene to the polymer, boric acid-treated polysilicone. This material is well known as the children’s toy Silly Putty. It is different from familiar materials in that it flows like a viscous liquid when deformed slowly but bounces like an elastic solid when thrown against a surface.

“When we added the graphene to the silly putty, it caused it to conduct electricity, but in a very unusual way. The electrical resistance of the G-putty was very sensitive to deformation with the resistance increasing sharply on even the slightest strain or impact. Unusually, the resistance slowly returned close to its original value as the putty self-healed over time. “

He continued, “While a common application has been to add graphene to plastics in order to improve the electrical, mechanical, thermal or barrier properties, the resultant composites have generally performed as expected without any great surprises.

“The behaviour we found with G-putty has not been found in any other composite material. This unique discovery will open up major possibilities in sensor manufacturing worldwide.”

Graphene is a two-dimensional material that was first isolated in 2004 at Manchester University. Graphene is 100 times stronger than steel, it can withstand 20 per cent strain, it is a million more times electrically conductive than copper and it is 98 per cent optically transparent, plus it’s harder than diamond and virtually impermeable.