The sensor, developed by the University of Sussex ‘s Materials Physics Group, can stretch up to 80-fold higher strain than strain gauges currently on the market and show 100-fold higher resistance changes than the most sensitive research materials.
The research team believes that the sensors could bring new sensitivity levels to the wearable tech measuring vital signs of patients and to the structural integrity of buildings and bridges monitoring systems.
Marcus O’Mara, from the School of Mathematical and Physical Sciences at the University of Sussex, said: “The next wave of strain sensing technology uses elastic materials like rubber imbued with conductive materials such as graphene or silver nanoparticles, and has been in development for over a decade now.
“We believe these sensors are a big step forward. When compared to both linear and non-linear strain sensors referenced in the scientific literature, our sensors exhibit the largest absolute change in resistance ever reported.”
Alan Dalton, Professor of Experimental Physics at the University of Sussex, said: “This promising technology may prove especially useful in established fields such as healthcare, sports performance monitoring and rapidly growing fields such as soft robotics.
“Our research has developed cheap, scalable health monitoring devices that can be calibrated to measure everything from human joint motion to vitals monitoring. Multiple devices could be used across the body of a patient, connected wirelessly and communicating together to provide a live, mobile health diagnostics at a fraction of the current cost.”
The new paper , published in the Advanced Functional Materials journal, details the process of incorporating large quantities of graphene nanosheets in a structured, controllable fashion into a PDMS matrix that results in excellent electromechanical properties.
The authors state that the approach has the ability to apply to a broad variety of two-dimensional structured materials and matrices of polymers. The sensors provide much enhanced conductivity with no apparent percolation threshold at all measured loading levels.
Commercial gage devices suffer from relatively low sensitivity and strain range, with gage factors ranging from 2-5 and maximum strains of 5 percent or less strain, resulting in an increase in resistance of less than 25 percent and preventing high-strain sensing required for body motion control.
Due to their higher gage factor of ~20, and up to 80 percent strain, the new sensors are able to detect strains of less than 0.1 percent, where the exponential response leads to resistance changing by a factor of more than one million.
As a consequence of the improvement in record resistance, this enables both high-sensitivity low-strain sensing for pulse control and high-strain calculation of chest motion and joint bending.
Dr. Sean Ogilvie, Research Fellow in Materials Physics said: “Commercial strain sensors, typically based on metal foil gauges, favor accuracy and reliability over sensitivity and strain range. Nanocomposites are attractive candidates for next generation strain sensors due to their elasticity, but widespread adoption by industry has been hampered by non-linear effects such as hysteresis and creep due to the liquid like nature of polymers at the nanoscale which makes accurate, repeatable strain readouts an ongoing challenge.
“Our sensors settle into a repeated, predictable pattern which means that we can still extract an accurate read-out of strain despite these effects.”
The work was made possible with support from Alliance, a US-based rubber firm.
Jason Risner, V.P. of Sales & Marketing at Alliance, said: “Alliance has a long history of innovation and it is vital for us to play an active role in leading edge rubber technology that uses a disruptive nanomaterial like graphene. It is critical that we partner with scientific leaders like Professor Alan Dalton at the University of Sussex.
“We are thrilled to see the products that could potentially come out of our partnership. Graphene is an astonishing material that can revolutionize our lives. Our company is proud to be on the cutting edge of something so new.”
