If you’re worried about the coming robot apocalypse, then worry some more because soft, squishy robots just got camouflage. Scientists at Harvard University working under a Defense Advanced Research Projects Agency (DARPA) contract have developed a way of turning soft robots into “chameleons” capable of blending in with their backgrounds and even hiding from infrared sensors. That’s pretty impressive (or scary) for robots that can be made for less than US$100 apiece.

Led by Drs. George Whitesides and Stephen Morin at Harvard University’s Department of Chemistry and Chemical Biology and the Wyss Institute for Biologically Inspired Engineering, the Harvard team took nature as their inspiration, modelling the robots on invertebrates that expand and contract their bodies in order to move or change their appearance. Such soft robots have been gaining a lot of attention lately, but the Harvard soft-bots took another page from nature’s notebook.

“When we began working on soft robots, we were inspired by soft organisms, including octopi and squid,” says Morin. “One of the fascinating characteristics of these animals is their ability to control their appearance, and that inspired us to take this idea further and explore dynamic coloration. I think the important thing we’ve shown in this paper is that even when using simple systems - in this case we have simple, open-ended microchannels - you can achieve a great deal in terms of your ability to camouflage an object, or to display where an object is.”

Many invertebrates, such as squids and cuttlefish, can change their appearances dramatically in a matter of seconds in order to blend into their surroundings or to communicate with or warn off other animals. They do this by means of chromatophores. These are basically little reserves of colored dye under the skin. When they want to change appearance, the animal squeezes these reserves and the dyes are pushed to the to just under the surface of the skin in the right combination to produce the desired color. It’s much the same as the color elements in a television where three primary colors can produce hundreds of hues. Combine red, blue and green in the right proportions and you have all the colors of the rainbow and more.

In the Harvard soft-bots, this isn’t quite so sophisticated. The robots are constructed using a 3D printer to create the molds used in their manufacture. These molds have networks of microchannels impressed in them. One set of channels carry the air that makes the robot squirm about in a frighteningly lifelike manner and the other carries colored fluid. When the robot walks over a surface, the appropriate pre-selected fluid is pumped in to match the surface and break up the pattern of the robot, making it less visible. The whole process takes less than 30 seconds and the silicone molds make the cost of each soft-bot only about US$100.

But the soft-bots’ camouflage isn’t confined to color. The fluid can be heated or cooled to match whatever surface the robot is walking on, making it all but invisible to infrared detectors. In addition, the robot can aid search and rescue missions by making itself more visible rather than less by filling itself with brightly colored, fluorescent or even bioluminescent fluids.

Needless to say, such abilities makes camouflaged soft-bots very attractive to DARPA, which sees important defense applications for a cheap, soft robot that is resilient, able to squeeze into small spaces and hide like a chameleon. However, it also envisions medical applications for the technology, such as artificial muscles or prosthetics.

The soft-bot technology is still very much at the test bench stage. The current examples are operated by tethers, which supply them with air and fluids as well as giving them commands. In later versions, all the support systems will be carried internally. The soft-bots also don’t go very fast, with a speed of about 40 meters per hour (0.024 mph). However, the team aren’t looking so much for speed as making them move more smoothly.

“There are a number of directions this technology could go in," says Morin. "Some of them are similar to the course we have taken thus far, but I think there are other aspects to explore - such as how the robots interact with their environment - that are related to what soft robots may be doing in the future.”

The results of the team’s work was published in the August 16 issue of Nature.

The video below shows a soft robot in action.

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