Researchers Develop Highly Stretchable Electroluminescent ‘Skin’

A team of scientists led by Dr. Rob Shepherd from Cornell University, Ithaca, has developed an artificial octopus-like skin that can stretch, sense internal and external pressure, and emit light.

Researchers Develop Highly Stretchable Electroluminescent ‘Skin’

Multi-pixel electroluminescent displays fabricated via replica molding; the device measures 5 mm thick, with each of the 64 pixels measuring 4 mm; it can be deformed and stretched in various ways. Image credit: Organic Robotics Lab at Cornell University.
“Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise,” Dr. Shepherd and co-authors said.
“We present an electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light.”
The discovery could lead to significant advances in health care, transportation, electronic communication and other areas.
“This material can stretch with the body of a soft robot, and that’s what our group does,” Dr. Shepherd explained.
“The material has two key properties: it allows robots to change their color, and it also allows displays to change their shape.”
The development that made the skin’s creation possible is a hyperelastic, light-emitting capacitor (HLEC), which the scientists designed using two ionic, hydrogel electrodes embedded in a matrix of silicone.
The HLEC device is many times more elastic than existing stretchable light emitters based on organic semiconductors.
To allow displays of different colors, the matrix in the team’s design contains zinc sulfide that is doped with various transition metals that emit different wavelengths as electricity passes through.
For example, blue light can be created with the presence of copper, or yellow light with magnesium.
“We can take these pixels that change color and put them on these robots, and now we have the ability to change their color,” said Dr. Shepherd, who is senior author of a paper in the journal Science .
“Why is that important? For one thing, 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 color in response to mood or the tone of the room we believe is going to be important for human-robot interactions.”
Tests of the material’s elasticity reveal that its surface area can expand by roughly 500% before the external wires lose contact with the hydrogel electrodes.
Because the capacitors are laid out in a plate-like formation, they also act as actuation sensors that can detect deformations from pressure and stretching.
Dr. Shepherd and his colleagues also created a three-chamber robot from the material, with the newly developed ‘skin’ layers on top, and inflatable layers below that allow movement.
As the chambers expand linearly, the robot moves forward with a worm-like wiggle.