New material could serve as robotic skin

Technology does change quickly, sometimes in leaps and bounds, but in this well-connected age, you don’t have to be prescient to predict the advances that are pushing us into a new reality resembling science fiction.

Earlier this month, one of these discoveries was made by a team of Cornell University graduate students led by Assistant Professor Rob Shepherd of the Organic Robotics Lab. The new material described in Science as “highly stretchable electroluminescent skin for optical signaling and tactile sensing” could have far-reaching effects.

This new, soft material can give off light even under severe deformation, akin to the skin of an octopus. Octupuses possess skin that can deform liberally, while changing color in order to camouflage the animals or communicate their mood and intent. Many organisms in the wild use these color changes to communicate as we do every day through our technologies, from traffic lights to biofeedback monitors. Many of these objects are hard and inflexible once they are cast into their permanent shapes. The ability to have a pliable material that can produce light is key in the development of more organic, “futuristic” technologies such as curved displays and even “electronic skins” for robots. Essentially, this type of material might one day allow you to comfortably give a robot a hug.

Following the paradigm of “bio-inspired design,” which traces as far back as the development of Velcro, the study of the skins of natural organisms inspired the new material’s creation. Similar materials had been designed in the past few years but all of them were more limited in the amount of strain that the materials could withstand. Soft, synthetic materials like silicones were a benchmark of elasticity that the inventors at Cornell hoped their materials could match.

A silicone can be stretched from 400 to 700 percent along its plane before breakage. Other ordinary materials don’t exceed a stretch of more than 120 percent.

But this new light-producing material can withstand more than twice that strain and is capable of resisting up to an ultimate strain of 480 percent. That means that you can pull it out to six times its size and still have it emit light successfully.

The secret is in its layers. The material is composed of layers of clear hydrogel electrodes around an insulating elastomer sheet. The elastomer is a pressure-sensitive material that changes its luminescence and its ability to store charge upon deformation. It can be also dynamic in its lighting, changing with response to touch.

One potential application that the researchers cited was the ability of this material to eventually enable humans to connect emotionally with robots by making them mood-sensitive and thereby more responsive to human interaction. As an early proof-of-concept, Shepherd’s team designed a soft robot that can crawl, with a skin made of this flexible material fashioned into grids of individual pixels to allow dynamic coloration and sensory feedback. Given that living organisms are defined partly by their ability to react to others, this invention could be a first step toward developing more life-like synthetics.