Scientists have developed a user- interactive colour changing electronic skin inspired by chameleons that could be used in robotics, prosthetics and wearables.

While science has been able to replicate the ability of animals such as chameleons, octopus and squids to change colour with artificial skin, the colour changes are often only visible to the naked eye when the material is put under huge mechanical strain.

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Now, researchers from Tsinghua University in China have developed a new type of user-interactive electronic skin, with a colour change perceptible to the human eye, and achieved it with a much-reduced level of strain.

The team employed flexible electronics made from graphene, in the form of a highly-sensitive resistive strain sensor, combined with a stretchable organic electrochromic device.

Researchers explored the substrate (underlying) effect on the electromechanical behaviour of graphene.

To obtain good performance with a simple process and reduced cost, they designed a structure to use graphene as both the highly sensitive strain-sensing element and the insensitive stretchable electrode of the electric current density (ECD) layer.

“We found subtle strain – between zero and 10 per cent – was enough to cause an obvious colour change, and the RGB (red green blue) value of the colour quantified the magnitude of the applied strain,” said Tingting Yang from Tsinghua University.

“Graphene, with its high transparency, rapid carrier transport, flexibility and large specific surface area, shows application potential for flexible electronics, including stretchable electrodes, super capacitor, sensors, and optical devices,” said Hongwei Zhu, professor at Tsinghua University.

However, our results also show that the mechanical property of the substrate was strongly relevant to the performance of the strain sensing materials, Zhu said.

“It's important to note that the capability we found for interactive colour changes with such a small strain range has been rarely reported before. This user-interactive e-skin should be promising for applications in wearable devices, robots and prosthetics in the future,” Yang added.