Squids and Other Cephalopods Inspired This Color-Shifting Smart Synthetic Skin

Researchers from the University of Nebraska-Lincoln have peered beneath the waves for inspiration in making a novel soft skin for future robots — giving them similar color-shifting abilities to squid and other cephalopods.

"We are working in an emergent area sometimes called autonomous materials," explains corresponding author Stephen Morin, associate professor of chemistry at the university, of the team's focus. "Autonomous materials have the ability to interact, sense, and react with their environment in the absence of user input. It unlocks a lot of very interesting opportunities in soft robotics, new types of human machine interfaces."

The paper focuses on a synthetic skin designed to mimic the color-changing capabilities of cephalopods, achieved in nature with tiny organs dubbed chromatophores and in the lab using a manufactured equivalent constructed from hydrogel. By layering the synthetic chromatophors, the researchers found, it's possible to create soft skins that can morph colors and patterns — using tricks including halftone absorption, optical interference, and microlensing.

"These types of devices are very versatile," claims first author Brennan Watts. "We can finely tune the chemistry of the individual components […] and have materials that respond to very specific stimuli. You could have a wearable technology that simultaneously reports the temperature, pH, humidity, all sorts of different parameters in a given environment. Doing that with traditional technologies, it would be challenging to measure all of those at the same time."

The use of entirely soft and liquid components in the skin's design means, the researchers say, that it's "inherently stretchable" — and thus could be easily applied to both robotics and wearables. The fundamental materials used in the production of the prototype are fully biocompatible, though the researchers admit that there are more biocompatible dyes available than the ones used during testing. "These capabilities," the team concludes, "coupled with the intrinsic actuation capabilities of microgel arrays on a stretchable support, will allow the fabrication of programmable, autonomous color-morphing and locomotive components in soft robotics and machine-human applications."

The full paper has been published in the journal Advanced Materials under open-access terms.