Scientists have long been fascinated with the ability of certain octopus and squid species to adapt to their surroundings by changing the texture and color of their skin. This trait allows the creatures to effectively use a natural form of three-dimensional morphing to camouflage themselves against would be attackers.
In a study featured in the journal Science, graduate students at Cornell University in New York describe how they were able to use the concept of glowing octopus skin to develop an artificial version that can stretch several times its original size and even emit light.
To create the new glowing skin technology, the researchers made use of a device known as a hyper-elastic light-emitting capacitor (HLEC) that was developed using a pair of ionic, hydrogel electrodes that have been embedded in a silicone matrix. The HLEC has better stretchability compared to other light emitters made from organic semiconductors.
The color-changing feature of the electroluminescent skin comes from the matrix, which contains zinc sulfide and different kinds of transition metals. These metals can emit various wavelengths whenever they are exposed to electric currents, such as magnesium for yellow light and copper for blue light.
The plate-like design of the capacitors' layout allows them to serve as some form of actuation sensors capable of detecting deformations on the artificial skin caused by stretching or pressure.
The Cornell researchers tested their new electroluminescent skin by placing it on a simple three-chamber soft robot. They also added inflatable layers to the bottom of the robot to allow it to move. With each linear expansion of the robot's chambers, it causes the device to wiggle forward much like how a worm would move.
Robert Shepherd, a mechanical and aerospace engineering professor at Cornell and lead author of the study, said that they were able to develop two things: a soft robot capable of changing colors and information display, and a display capable of changing shapes.
Shepherd and his colleagues view the creation of the color-changing skin as a significant development that could have a number of uses, especially in the field of robotics.
Researchers can use the technology's changing colors as a way for robots to express moods, allowing them to establish a better emotional connection with people.
Shepherd added that the artificial skin can also be used to create wearable electronic devices. It makes it an ideal base for gadgets, such as Fitbit and the Apple Watch, because its stretchability allows it to conform to the wearer's shape well.
"You could have a rubber band that goes around your arm that also displays information," study co-author Chris Larson pointed out.
"You could be in a meeting and have a rubber band-like device on your arm and could be checking your email. That's obviously in the future, but that's the direction we're looking in."
Shepherd also envisions using the stretchable technology to develop devices that display buttons, such as a volume control knob, only when users need them and then goes away once they are finished adjusting it.