Octopi have some pretty impressive skills. They use tools. They hatch daring escapes. They play games. They use trial-and-error. But perhaps their coolest (and certainly most YouTube-worthy) skill is their ability to camouflage themselves. They can change not only their color, but also their texture, using projections called papillae on their skins to create bumps and ridges to blend in with rocks, coral, seagrass, sand and pretty much whatever else is nearby.
A useful skill to have, right? Now, we humans may be getting closer to harnessing this master-of-disguise ability. Researchers at Cornell University, University of Pennsylvania and the Marine Biological Laboratory at Woods Hole have created a 2D material that can transform into a complexly textured 3D structure when inflated, paving the way for a number of potential uses.
The material is silicone rubber embedded with fiber mesh. The mesh is layered in rings, acting in a similar way to octopus muscles, pulling the rubber skin into various shapes. In testing, the researchers configured the mesh in a way that, when inflated, the material took on the appearance of a series of round stones. They also designed a mesh to look like a type of succulent plant.
James Pikul, a mechanical engineering professor at the University of Pennsylvania who helped lead the research, was inspired by cephalopods like squid and octopi while working on building better soft-textured robots.
“These creatures are incredibly fascinating because they’re entirely soft,” he says. “They can run on the sea floor, they can swim, but they have no skeletal system. They’re the perfect design goal for someone who’s creating a soft robot.”
One of the challenges of working with soft materials like rubber in robotics is that they can be hard to control, as they stretch in multiple ways. Pikul realized that imitating the muscle structure of a cephalopod by adding relatively un-stretchy fabric rings to a soft material was a way to gain more control over the shape.
Pikul and his team decided to test their material by making it look like rocks because “rocks are actually quite challenging to camouflage into,” Pikul says.
A person standing in front of a bunch of boulders in a boulder-colored suit just looks like a human-shaped rock, especially when the sun shines and casts a human-shaped shadow. But by adding texture, you’ve changed the equation.
The succulent plant was chosen as a test subject because of its bulbous leaves. Right now the prototype materials don’t have the kind of stretch to transform into very thin structures like oak leaves or paper. But the round leaves of succulent plants were within reach. Pikul and his team hope to ultimately develop structures that can be pulled very thin.
The research, which was sponsored by the Army Research Office, appears this week in the journal Science.
"The results are impressive," writes Cecilia Laschi, a robotics professor at the Sant'Anna School of Advanced Studies in Pisa, Italy, commenting on Pikul's work in Science.
Although the textures created in the prototype materials are fairly simple, Laschi says, they represent an important first step towards multiple potential military, scientific and architectural uses. They could help scientists study animals in the wild by allowing camera robots to successfully blend in with their surroundings. Inflatable 3D buildings made of the materials could change shape based on need, turning their surfaces from smooth to pebbled to add shade during sunny periods, or moving to shift solar panels into better positions as the sun moves across the sky.
Inspired by the moving Marauder’s Map in Harry Potter, Pikul imagines a smooth car dashboard that, at the touch of a button, transforms into a topographical map of its surroundings. Or a joystick that emerges from a flat surface and disappears when you no longer need it.
Pikul also plans to work on developing materials that can transform into more than one shape. In that respect, the octopus is still well ahead of humans. As Laschi notes, we still don't understand how cephalopods detect the color and texture of their surroundings. If further research were to crack this mystery, it could lead to the development of automatically self-camouflaging robots.
Other researchers working on soft robots have taken inspiration from octopi and other cephalopods. Last year, Harvard researchers debuted a 3D printed autonomous "octobot" that propels itself by chemical reaction. Earlier this year, a German robotics company came out with a robot octopus tentacle of soft silicone, which can pick up and put down objects. Laschi helped launch a multinational project to create octopus robots, with an aim towards understanding and harnessing the creature's abilities to camouflage, manipulate objects, move and sense their environments.
But could they fool a real octopus?