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The research team believes the sensors could bring ‘new levels of sensitivity’ to wearable technology that measures medical patients’ vital signs. They could also monitor the structural integrity of buildings and bridges.
The sensor, developed by the university’s Materials Physics Group, can stretch up to 80-times higher strain than strain gauges currently on the market and shows resistance changes 100-times higher than most sensitive materials in research and development.
“We believe these sensors are a big step forward,” said researcher Marcus O’Mara. “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.”
The “promising” technology could be especially useful in established fields including healthcare, sports performance monitoring and rapidly growing fields such as soft robotics, said Professor Alan Dalton.
“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 live, mobile health diagnostics at a fraction of the current cost.”
A new paper on the sensor, published in Advanced Functional Materials, detailed the process for incorporating large quantities of graphene nanosheets into a PDMS matrix in a structured, controllable fashion that results in excellent electromechanical properties.
The method could be extended to a wide range of two-dimensional layered materials and polymer matrices, the researchers said. The sensors reportedly deliver greatly enhanced conductivity at all measured loading levels, with no apparent percolation threshold.
The team said that commercial gauge devices suffer from relatively low sensitivity and strain range, with gauge factors ranging from two to five and maximum strains of 5% or less, resulting in the resistance increasing by less than 25% and preventing high-strain sensing required for bodily motion monitoring.
The new sensors are able to detect strains less than 0.1% due to their higher gauge factor of roughly 20, and up to 80% strain, where the exponential response leads to the resistance changing by a factor of more than one million. This allows both high-sensitivity low-strain sensing for pulse monitoring, and high-strain measurement of chest motion and joint bending.
“Commercial strain sensors, typically based on metal foil gauges, favour accuracy and reliability over sensitivity and strain range,” said research fellow Dr Sean Ogilvie. “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 read-outs 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.”
US rubber company Alliance supported the work. “We are thrilled to see the products that could potentially come out of our partnership,” said Jason Risner from Alliance. “Graphene is an astonishing material that can revolutionise our lives. Our company is proud to be on the cutting-edge of something so new.”
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.