When thinking of leading-edge wearable technology, silly putty probably isn’t something that comes to mind. Made from silicone polymers, silly putty interests bioengineers for the same reason it fascinates kids; it’s highly responsive to pressure and stretches all directions without breaking. A research team in Ireland has added thermoelectric conductive graphene to silly putty, then used it to screen print a highly sensitive and flexible wearable sensor.

Of course, it wasn’t really that simple for the team of engineers from AMBER, the SFI Centre for Advanced Materials and BioEngineering Research, and the School of Physics at Trinity College Dublin. It took years to perfect “G-putty,” a polymer-graphene nanocomposite that functions well as a strain sensor. Strain sensors — typically made of foil — measure the electrical resistance of their material when strained by an external force. 

Unlike foil, G-putty withstands strain without losing its shape or breaking. The same quality makes it highly sensitive to very slight pressure, such as the motion of skin caused by a pulse. That means G-putty encompasses the two magic words in emerging sensor technology: flexibility and sensitivity.

The team describes how they formulated a sprayable ink from G-putty in a paper published in the journal Small. According to the researchers, the new sensors have a 50-fold increase in sensitivity over industry-standard wearables. Existing strain sensor technology made of foils also has limitations when it comes to long-term reliability.

G-putty accurately detects respiration, pulse, and blood pressure, making it ideal for both clinical and consumer applications. In addition, the researchers designed inks of different viscosities, suggesting that screen printed G-putty has potential as a versatile, low-cost, flexible sensor.