Beyond wearable devices and tactile displays, colour-changing devices could be used in camouflage, smart home furnishings and communicating emotions. They could also help convey information about robotics and prosthetics.
Inspired by the ability of animals like the chameleon to change colour, scientists in China have developed a ‘user interactive electronic skin’ that changes colour when placed under strain.
The thin-film detector combines graphene fabric, a stretchable polymer substrate and an electrochromic layer to provide an instantaneous and colourful readout. For example, a sensor attached to a glove shifts from green to blue as the wearer flexes their hand, putting the device under strain.
The sensor returns to green when the hand relaxes. Beyond wearable devices and tactile displays, colour-changing devices could be used in camouflage, smart home furnishings and communicating emotions. They could also help convey information about robotics and prosthetics.
The team, which includes scientists from Tsinghua University, Peking University and the China Academy of Engineering Physics, is working to identify the best combination of materials for such varied applications. One of the toughest challenges is providing the capability to detect small mechanical deformations, in other words matching the colour change to strains of 10% and below.
Today, a number of so-called mechanochromic compounds and composite materials change their optical appearance when stretched, but usually under relatively large strains of 100% to 500%. To achieve greater sensitivity, the group has engineered a graphene fabric woven from highly flexible, two-dimensional layers of carbon. Stretching the graphene fabric changes its electrical resistance, which in turn helps modulate the colour of the device’s electrochromic chemical layer.
When a voltage is applied, the sensor exhibits colour switching in response to strains over a range of 0% to 10%. The sensor is not only highly responsive, but also compact because the conductive graphene fabric serves as both the sensing element and the electrodes for the colour-changing circuit.
A popular polymer material, PDMS, provides an elastic substrate to complete the sensor’s mechanical design. The scientists refer to the package as a ‘smart functional biomimetic system’, noting that its ability to change colour in response to strain imitates the behaviour of certain animal skins.
Further information
Professor Hongwei Zhu
E-mail: [email protected]
School of Materials Science and Engineering
Tsinghua University, China
Simon Davies
Email [email protected]
Senior Public Relations Officer
Institute of Physics
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