Silicone-based robots can control their appearance

Soft robots developed at Harvard University have been given the ability to camouflage themselves or to stand out from their environment.

A team of researchers led by George Whitesides, the Woodford L and Ann A Flowers university professor, took inspiration from starfish and squid to develop silicone-based robots that were unveiled last December in PNAS.

The researchers have now developed a biomimetic system that allows the soft robots to either camouflage themselves against a background or to make colour displays.

Such a ‘dynamic coloration’ system could one day have a host of uses, ranging from helping doctors plan complex surgeries to acting as a visual marker to help search crews following a disaster, said Stephen Morin, a post-doctoral fellow in chemistry and chemical biology and first author of a paper describing the work in Science.

‘When we began working on soft robots, we were inspired by soft organisms, including octopi and squid,’ he said in a statement. ‘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 colouration.

‘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 micro-channels — you can achieve a great deal in terms of your ability to camouflage an object or to display where an object is.’

Whitesides said: ‘One of the most interesting questions in science is: why do animals have the shape, and colour, and capabilities that they do? Evolution might lead to a particular form, but why? One function of our work on robotics is to give us, and others interested in this kind of question, systems that we can use to test ideas. Here the question might be: how does a small crawling organism most efficiently disguise [or advertise] itself in leaves? These robots are test beds for ideas about form and colour and movement.’

As with the soft robots, the ‘colour layers’ used in the camouflage start as moulds created using 3D printers.

Silicone is then poured into the melds to create micro-channels, which are topped with another layer of silicone.

The layers can be created as a separate sheet that sits atop the soft robots or incorporated directly into their structure.

Once created, researchers can pump coloured liquids into the channels, causing the robot to mimic the colours and patterns of its environment.

The system’s camouflage capabilities are not, however, limited to visible colours.

By pumping heated or cooled liquids into the channels, researchers can camouflage the robots thermally. Other tests described in the Science paper used fluorescent liquids that allowed the colour layers to glow.

But the uses for the layer-layer technology do not end at camouflage.

Animals use colour change to communicate and Morin envisions robots using the system as a way to signal their position to other robots and the public.

Soft machines could be used, for example, during search-and-rescue operations following a disaster. Morin said that, in dimly lit conditions, a robot that stands out from its surroundings (or even glows in the dark) could be useful in leading rescue crews trying to locate survivors.

‘What we hope is that this work can inspire other researchers to think about these problems and approach them from different angles,’ he said. ‘There are many biologists who are studying animal behaviour as it relates to camouflage, and they use different models to do that. We think something like this might enable them to explore new questions, and that will be valuable.’