Researchers Invent Silly Putty Pressure Sensor

Posted in Medical Materials - Raw Materials by Nancy Crotti on December 14, 2016

A cross between graphene and flexible silicone, the material has implications for medical devices.

Nancy Crotti

What do you get when you embed sheets of graphene in lightly cross-linked polysilicone? Italian and British researchers came up with supercharged Silly Putty--a highly flexible substance with sensitive electromechanical sensors that can measure pulse, blood pressure, and even the footsteps of a small spider.

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The sensors have gauge factors of >500, which enable them to detect such bodily functions and yield implications for medical devices, according to a report in Science. The researchers, based at Cambridge University’s Cambridge Graphene Centre and the University of Trieste in Italy, believe their work could one day lead to the development of implantable graphene-based electrodes that might restore sensory function to amputees, people with paralysis, and also help people with movement disorders such as Parkinson’s disease.

Graphene has been touted as the next wonder material that could eventually replace silicon in electronic devices. With its one-atom thick lattice of carbon atoms, the material was thought to be an ideal upgradeon silicon given its ability to allow for the rapid movement of electrodes through its two-dimensional form. It’s also strong, extremely flexible and conducts electricity with remarkable efficiency.

The researchers in this study assembled tiny sheets of graphene that were one nanometer thick inserted the into the silicone polymer. There, the graphene nanosheets created a microscopic network of electrical conductors, according to the report in Science. Then they measured how difficult t was to pass electricity through the conductors in the putty, connected the putty to electrodes and the electrodes to a computer.

When the G-putty (the name the researchers gave the substance) was held against the skin near someone’s carotid artery, the person’s pulse was able to disrupt the electrical current flowing through the graphene, yielding an electrical resistance measurement, Science reported.

With the G-putty acting as a pressure sensor, the researchers can calibrate it to convert electrical resistance into vital measurements, such as blood pressure. Plus, the material is 250 time more sensitive than the least expensive metal-based sensor on the market, and it’s inexpensive, Science reports. The researchers are working on commercializing G-putty, because it can be reproduced easily and inexpensively.

Although graphene is widely used in nanocomposites, its effects while embedded in highly viscoelastic polymer matrices is not well understood, according to the researchers.  The G-putty displayed “unusual electromechanical behavior, such as postdeformation temporal relaxation of electrical resistance and nonmonotonic changes in resistivity with strain” associated with the nanosheets’ mobility within the putty.

“By considering both the connectivity and mobility of the nanosheets, we developed a quantitative model that completely describes the electromechanical properties, they wrote. “These nanocomposites are sensitive electromechanical sensors with gauge factors >500 that can measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider.”

Italian and British researchers have shown that it is possible to interface graphene with neurons or nerve cells, maintaining the integrity of the cells.

Recently other materials have emerged, like black phosphorus, to give graphene a run for its money.

Graphene is not easy to make on a large scale. Based on research at Trinity College, Dublin,Thomas Swan & Co. Ltd (Consett, County Durham, UK) in 2014 successfully scaled upa pilot manufacturing line able to produce up to a kilogram of high quality, few-layer graphene nanoplatelets.

Nancy Crotti is a contributor to Qmed

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[image courtesy of AMBER CENTER, TRINITY COLLEGE DUBLIN]