New rubber lights up with deformation

Materials World magazine
15 Mar 2016

A 'robot skin' has been developed by researchers at Cornell University, USA, that can emit light when stretched to 480% of its original size, with the team claiming it can endure more than twice the strain of previously tested stretchable displays.

The ability of some octopi to change their skin colour has inspired the effort to develop the skin, an electroluminescent rubber-hydrogel composite.

Rob Shepherd, Assistant Professor of Mechanical and Aerospace Engineering, led the team. He said, 'When robots become more and more a part of our lives the ability for them to have emotional connection with us will be important. So to be able to change their colour in response to mood, or the tone of the room we believe is going to be important for human-robot interactions.’

The researchers sandwiched a ZnS phosphor-doped dielectric elastomer between layers of transparent hydrogel electrodes. The layered sheets have individually controllable pixels that can change illuminance and capacitance under deformation. The sheets, fabricated using replica moudling, were stretched, rolled and folded to demonstrate their ability to work under stress and then integrated into the 'skin' of a soft robot

Three six-layer panels panels were bound together to make the robot, with the top four layers making up the light-up skin and the bottom two pneumatic actuators to facilitate movement. The robot had 'dynamic coloration and sensory feedback from external and internal stimuli', according to the paper Highly Stretchable Electroluminescent Skin for Optical Signaling and Tactile Sensing, which was published in Science on 3 March.