'Morphing skin' of octopus inspires robotic camouflage

Engineers working in a field called soft robotics have taken inspiration from the shape-shifting ways of the octopus to develop a programmable 3D material that can change its appearance.

Their invention, reported Thursday in the journal Science, could have far-reaching applications ranging from high-tech military camouflage to smart devices that change their interfaces to suit users' needs.   

With projects engineers are working on today, we could one day see robots with soft, human-like skin, or capabilities that allow them to change their shape, said Pikul. "This is an active field of robotics that's still developing. There's nothing really that's fully been commercialized yet." 

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One of the challenges in this field is controlling the soft materials, which Pikul likens to trying to compress an inflated balloon into the shape of a cube using only your 10 fingers.

So, as engineers often do, he said, they looked to nature for some inspiration. This time they found it on the ocean floor.

'They can do all these amazing things'

Marine animals called cephalopods — a group that includes the octopus and the cuttlefish — have no skeletal system, yet they're able to swim, crawl, change the texture and colour of their skin and even run along the bottom of the ocean. 

"We were looking at these creatures because they have very similar characteristics as the materials we're looking at but they can do all these amazing things," said Pikul, now an assistant professor of mechanical engineering at the University of Pennsylvania.

The two studied the work of leading cephalopod expert Roger Hanlon, a biologist at the Marine Biological Laboratory in Massachusetts, and then reached out to him as a collaborator. 

Pikul said Hanlon helped them understand the unique surface of the octopus and the cuttlefish, which is dotted with bumps called papillae — tiny little muscle groups that protrude and retract to help the animals alter their shape to blend in with their surroundings.

"These are soft-bodied molluscs without a shell," said Hanlon in a written statement about the paper, for which he is a co-author. "Their primary defence is their morphing skin."

The animals can mottle the surface of their bodies to help them hide in sea vegetation, then smooth themselves back out again so they can move swiftly through the water.

Now you see it, now you don't

So using a balloon-like silicone material — "kind of like those Silpats that people bake with" — and non-woven fabric usually used for embroidery, the two engineers came up with something that would equally impress your home-ec and shop teachers.

That silicone material, also known as an elastomer, was layered with rings of the embroidery fabric, which would constrain it as it inflates.

A computer algorithm then calculated the slope of the desired shape the engineers wished to achieve, and controlled the inflation of the elastomer using the correct amount of air pressure.

While this area of research is still new, potential future applications are numerous.

"One of the things that we're really interested is this idea of vanishing interfaces," said Pikul. 

Consider the dashboard on your vehicle as one example: "It's flat, it almost looks like leather and there's not much there," he said.

"You'd have this cool interface — and when you don't need it anymore, it disappears and looks like a dashboard again." 

The research was supported by the U.S. Army Research Office, which was interested in both the camouflaging capabilities of the material and the potential behind soft robotics in general, said Pikul.

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