When you submerge your hand in water for a while, your fingers begin to wrinkle. Why? It's not an entirely settled question, but the current thinking is that it gives humans a better grip on wet objects.
Jellyfish skin also wrinkles, but not in the presence of water (or they'd be wrinkled their entire lives). "When they're scared, some types of jellyfish form a wrinkled surface that is opaque and warns off predators," says Songshan Zeng, who's working on developing new, wrinkled materials inspired by nature. "That same surface is transparent when it's flat."
It's hoped these new materials could come with totally new properties. "Our experimental materials use cracks, folds or wrinkles to mimic the surface engineering of skin," says Luyi Sun, heading the research.
"These new materials are unique because they change color or transparency when they're stretched or exposed to moisture."
In tests, the team simulated skin wrinkles by placing a rigid thin film of polyvinyl alcohol on a rubbery base. "Like finger skin, whenever part of the film is exposed to moisture, it swells slightly, generating wrinkles," Sun says. The wrinkled part can be used to form patterns that only appear when the film is moistened.
The wrinkles can also help improve the anti-glare properties of screens. Wrinkles scatter light in all directions, rather than reflecting them back at the viewer, making a coating with micro-wrinkles a cheap and effective anti-glare treatment for screens.
As well as the wrinkles, the team is also experimenting with the pigments found in squid skin, allowing a material to change topography and appearance reversibly when stretched.
Zeng and Sun are presenting their research this week at the 252nd National Meeting & Exposition of the American Chemical Society.