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With artificial ‘octopus skin,’ robots can bend and stretch while changing color

Researchers developed artificial skin technology to make better robots. (Video: American Association for the Advancement of Science)

Imagine a wearable smartphone that could bend and stretch with your body, all while displaying a glittering array of colors. That's the eventual goal of this new octopus-inspired robotic "skin" from researchers at Cornell. It can stretch to six times its original size while still emitting light. Described in a study published Thursday in Science, this super-stretchy skin is designed to give soft robots the ability to change color and display information based on input from their sensors.

Soft robots have been gaining popularity among engineers over the past few years. They're exactly what they sound like: robots made from squishy materials. Made without the stiff mechanical components of a traditional robot, they're much better at bending and squeezing into tight spaces. They're also less likely to hurt the animals, people and objects they interact with, because they lack hard edges. Because of this, engineers have suggested that soft robots could be used to crawl into collapsed buildings in search-and-rescue missions, or even be used as a safer alternative to current robotic surgical tools.

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But for now, most soft robot prototypes have a lot of hard robot baggage. Engineers have to come up with new ways to build basic components such as batteries, circuit boards and displays using flexible materials.

"The clock radio in your car works in the same way [as the new octopus skin], but isn’t made with material that stretches," lead study author Robert Shepherd, assistant professor of mechanical and aerospace engineering at Cornell, told The Washington Post. The idea for the skin came about when Shepherd challenged his graduate students to design devices that overcame the rigidity of traditional components.

The students were inspired by cephalopods, which are able to change their skin color and also have a degree of squishiness that any soft robotics engineer would covet. But mimicking the mechanism that octopods use would have been too complicated: Those animals change color by absorbing and reflecting light, and the team decided it would be easier to design light emitting components that could handle stretching.

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The skin is formed with two layers of transparent hydrogel that conduct electricity. Between those layers is an array of capacitors that light up as electricity passes through them.

By layering the skin on top of inflatable chambers, they were able to create a robot that can crawl and wiggle around, albeit pretty clumsily for now:

Shepherd sees the technology going in two different directions. "We actually made two things here," he said, "we made soft robots that can change their color and display information, and we made a display that can change its shape."

The former could give us robots that change color when touched — "mood" robots, if you will — to make them seem friendlier to humans. Robots also could use simple color changes (or more complicated displays) to respond to environmental stimuli, making them better at sharing information with their human users. A robot in a hospital could display a patient's vitals or change colors to signal an emergency.

The shape-changing displays could get pretty crazy: Shepherd would like to see interfaces that create buttons only when the user needs them.

"Imagine having a volume control knob that pops up when you need it and then goes away," he said.

There's one big hurdle to get over before this stretchy skin can cover all of our devices: The conductive rubber used by Shepherd and his colleagues can evaporate when conditions get too hot or dry. They'll need to find or develop a similar rubber that can handle any temperature a human might find himself in.

But it's apparent that the age of squishy, bendy electronics will soon be upon us.

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