All products featured on WIRED are independently selected by our editors. However, we may receive compensation from retailers and/or from purchases of products through these links.
The amazing properties of jellyfish and squid skin have inspired scientists to invent new materials that change colour or texture in response to changes in their surroundings.
The materials could one day be used by spies to hide and reveal secret messages, as well as in smart windows and in phones, to cut screen glare.
"Our experimental materials use cracks, folds or wrinkles to mimic the surface engineering of skin," said Luyi Sun, associate professor in the Department of Chemical and Biomolecular Engineering at the University of Connecticut. "These new materials are unique because they change colour or transparency when they're stretched or exposed to moisture."
The team was inspired by jellyfish skin, which changes hue when it contracts. "When they're scared, some types of jellyfish form a wrinkled surface that is opaque and warns off predators," Songshan Zeng, a researcher on the study, explained, adding: “That same surface is transparent when it’s flat.”
The engineers replicated the wrinkled surfaces by placing a rigid thin film of polyvinyl alcohol on a soft, stretchy rubbery base, according to the study, published in the journal Nature Communications.
"Like finger skin, whenever part of the film is exposed to moisture, it swells slightly, generating wrinkles," Dr Sun said.
Because the wrinkled part of the film is opaque, it can be used to form patterns, such as letters, which appear when the film is moistened. These patterns can be permanent, or reversible, depending on the crosslinking between polymer chains in the film.
For example, if the film is formulated without crosslinking, wrinkles can be generated by moisture and subsequently smoothed out, but they cannot form again. This would be useful for displaying a message and then permanently erasing it once it's read - a feature spies such as James Bond would appreciate, Zeng noted.
One type of crosslinking allows wrinkles to be generated by moisture and never erased. This could be put to use in smartphones to help manufacturers know when warranties have been voided. A water activated label within a smartphone could form the letters H2O if it ever came into contact with water, for example.
Because the wrinkles scatter light rays in multiple directions rather than reflecting them directly back at a viewer, the material could also be used to make a cheap and effective anti-glare screen for phones, the researchers said.
The researchers were also inspired by squid, which contract muscles in their skin when startled, exposing coloured pigments that help them blend in with their surroundings. They mimicked squid skin by creating a rubbery base layer containing a small amount of fluorescent dye and coating it with a thin film partly made of clay, which makes the layer prone to developing a multitude of tiny cracks and folds.
Stretching the material opens the folds and cracks on the originally smooth surface, altering its topography and appearance. Depending on the formulation, the film can temporarily change colour or go from clear to opaque. This means it could one day be used to make a smart window that could switch between clear and opaque modes.
Zeng explained: "To get privacy for windows, all you would need to do is just stretch the material a little bit to obtain opacity. We are very excited for all these applications."
The researchers presented their work at the 252nd National Meeting & Exposition of the American Chemical Society (ACS).
This article was originally published by WIRED UK
