Stretchable, glow-in-the dark 'skin' could give robots a sense of touch

Researchers created a thin, flexible electronic 'skin' that glows in the dark – and gives a robot a sense of touch. Here's how the material works, and how could it be used in bendable electronics and mood-sensitive robots.

Robots don’t have to be made of metal – at least not on the outside. A group of researchers at Cornell University and the Italian Institute of Technology created a robot without a rigid skeleton and covered it in stretchy, luminescent “skin” that gives the robot a sense of touch. In addition to making robots softer and less intimidating, the material could also equip robots with the senses of touch and proprioception, or knowing where their bodies are without looking.

If you close your eyes and touch your finger to your nose, your sense of proprioception is at work helping you keep track of where your limbs are and making sure you don’t poke yourself in the eye. For robots, that same sense could be judged through electrical capacitance. An electric field runs through the robot skin, which changes as the skin is stretched, rolled, and flattened. By measuring the changes in that electric field a robot could judge pressure and position, giving it sensitivity to light touches and hard impacts.

The electric field also causes the skin to glow, creating different colors depending on whether elements such as magnesium or copper are present in the material.

“This skin could allow soft robots to make themselves more or less visible in their environment, or colorize themselves to appear more friendly or aggressive,” Rob Shepherd, director of the Organic Robotics Lab at Cornell, told Popular Mechanics. That could mean soft robots that change color as their own status changes – getting redder as their batteries near depletion, for example – or in response to perceived changes in their environment. 

The skin itself, composed of three layers of silicon, is able to stretch to almost five times its starting length. The inner layer of glowing silicon is sandwiched between a conductive gel material and a tougher outer layer of silicone, which makes the whole layer sensitive to touch and able to continue glowing while it’s being rolled up or stretched in one or more directions.

Right now, the researchers are able to put a few dozen different-colored patches together in a single sheet of this skin, but they hope that as their research advances they'll be able to shrink those patches down to the size of pixels and cluster them together more densely. If the glowing colors could be changed rapidly and independently, the skin could then start to act like a stretchable screen, paving the way for future devices such as a smartphone that can be stretched to tablet size or rolled up and put in a pocket when not in use.