A robot that can change colour to either blend in with or stand out from its surroundings has been created by scientists.
The machine, designed by researchers at Harvard University, was inspired by the camouflage skills of sea creatures such as octopuses, cuttlefish and squid.
Like these cephalopods, the robot has a soft, rubbery body and can move with flexibility.
Professor George Whitesides, an author of the paper, said: "Conventional robotics is a pretty highly developed area, and if you look at various robots you find that most are basically built on the body plan of a mammal.
"Our question is: Why do you have to do that? Why not think about organisms that are soft, that might have quite different structures and ways of moving and strategies for camouflage. And the obvious place to look is underwater."
In 2011, the research team published a paper in the Proceedings of the National Academy of Sciences (PNAS) that outlined details of a "soft robot" that could crawl and bend under obstacles.
The machine was made from silicon-based polymers, and its movement was driven by air pumping through tiny cylinders in its four "legs".
Now the scientists have added another layer of complexity to these robots by giving them the ability to disguise themselves.
The camouflage-bots are covered in a network of tiny channels. As different dyes are pumped in, the robots can quickly change their appearance.
As well as changing colour, hot or cold fluids can be pumped into robots, enabling them to be thermally camouflaged, and fluorescent liquids allow them to glow in the dark.
Currently, the fluid is pulled in from a reservoir, but in the future it could be incorporated into the robot's body.
Search and rescue
The team thinks the devices could have a variety of different uses.
Lead author Stephen Morin said the soft machines had similarities with organs or tissues and could have medical applications.
He explained: "The idea is that if you have a system that can simulate muscle motion very well and a system that can transport fluid, by combining those you can fabricate that device to fit a specific surgical problem.
"And in planning for surgery or training, you can use something like this in guilt-free way."
The team also said the machines could have a future in search and rescue.
Prof Whitesides said: "For that kind of application, having it be able to advertise itself, for example, in a way that stood out against the dark would be a good thing."
He said the fact that the robots were lightweight, flexible and also relatively inexpensive was advantageous.
He explained: "The nice thing about these systems is that their properties are very different from conventional robots. You get pretty complicated motions from pretty simple systems.
"For a mission like search and rescue, these kind of robots could in principle be throwaway. So if you took a $25,000 robot and sent it in and the building falls down, then that is a real issue. If you send one in which is $100 and the roof falls in, you really don't care."