Did you ever wish you could change your skin color like a squid, to blend in with your surroundings? It would be a useful talent, no doubt, for napping during boring meetings.
Squid and octopi are some of the only animals on Earth with this unique skill, which they can use to hide from predators on the ocean floor. Using their muscles, they expand or expose pigment sacks in their skin to achieve a specific color or pattern. They can also texturize their skin at will, going from smooth to wrinkled or rippled.
Now, a team of scientists at the University of Connecticut has figured out a way to replicate this color- and texture-changing process. It might not help you blend into your desk chair, but it could help create new technologies, such as anti-glare screens, embedded encryption, privacy windows and even color-change clothing.
The team, led by materials scientist Luyi Sun and his colleague Songshan Zeng, as well as their collaborator Dianyun Zhang, has created materials that can change color, texture and transparency. The materials take advantage of the property called ‘mechanochromism,’ or color change due to the application of mechanical force.
“We learned that some squid, they can change their skin muscle to disclose or reveal some of the pigments embedded in their skin layer,” says Sun. “We said ‘oh, that’s something we could probably mimic.'”
The team created a two-layer material—a rigid film of polyvinyl alcohol and clay composite on top of a more elastic bottom layer of polydimethylsiloxane (PDMS) embedded with dye. The top layer develops tiny cracks and ridges when stretched; the material then reveals what’s below. This set up can be used to create materials that go from transparent to opaque, become more luminescent, or change color entirely.
They also created a material with a rigid top film of polyvinyl alcohol, without the clay composite, on a bottom layer of PDMS. When exposed to moisture, the material wrinkles, much like human fingers after a long swim. This wrinkling can be engineered to be reversible or non-reversible.
These technologies have several potential applications, says Zeng. The mechanochromic technology could be used to create smart windows that look clear in their resting state, but can be made opaque when stretched, creating instant privacy. They could also be used to create a new generation of color-change display optics, toys or even clothing. The moisture responsive wrinkle technology could be useful for making anti-glare computer, tablet and smartphone screens as well. The irreversible wrinkling technology could also be used for encryption—a message is embedded in the material that can only be seen when moistened, and can be made to disappear instantly after it’s read, James Bond style.
The base materials are all quite low-cost, and the process of creating the color- and texture-change technology is quite simple, Sun says. He plans to partner with industries to come up with more real world applications for the material in the near future. The next steps will be to improve and expand the technology. Right now the color change needs to be activated by UV light; the team would like to develop it so it can be used in any kind of light. They’re also interested in using different stimuli besides mechanical force to make the color and texture changes happen, perhaps creating a material that could be altered by temperature change, for example.
“We are working really hard right now to further improve and make advances, and we’ve achieved some real nice progress,” Sun says.
The team presented their research at the 252nd National Meeting and Exposition of the American Chemical Society, held last week in Philadelphia.