Robotic skin that senses touch

A recipe for a soft robotic skin that is sensitive to touch and deformation, and has the ability to change colour like an octopus, has been developed by engineers in the US.

Soft-skinned robots that can sense their environment and interact safely with humans are a major engineering goal.

But the technology is currently limited by a lack of suitable electronics that can stretch continuously over the body of the robot, as well as acting as a sensor or a display.

Now, a team at Cornell University led by researcher Rob Shepherd have found a way to nail all three problems at once with the development of a rubber-based skin that can both "feel" and also change colour.

The technology is presented in the current edition of the journal Science. It's multilayered and resembles a rubber sandwich.

The "bread" consists of a supporting flexible layer. Enclosed within, from the bottom up, are a pneumatic strip that can change the shape of each piece of skin, a layer of rubber containing a conductive liquid, an insulating layer and then another conductive rubber layer.

Applying a small voltage to the two conducting layers of rubber turns them into a capacitor. Deforming the skin - either by touching it, or making it move, changes the capacitance in a detectable and measurable way providing feedback about the level of force being applied.

The team also realised that if they embedded tiny light-emitting particles into the insulating rubber layer, they could also make the skin glow when the power is applied.

And varying the composition of the light-producing chemicals means that a range of colours can be emitted.

"So we now have a soft robotic skin that can display information - or even make a robot blush - as well as 'feel' a surface by registering how much it's being deformed," says Shepherd.

So far the team have made an 64-pixel piece of their skin that measures about 5 centimetres by 5 centimetres, is 5 millimetes thick and can stretch elastically in any dimension by almost 500%.

"We're now working to scale this up so we could cover an entire robot with it," explains Shepherd.

"And we have a project with NASA to investigate how this could be used to make exploratory rovers that can probe bodies of water and light their way as they go along."