New plastic material spontaneously oscillates in sunlight

A new material developed by researchers at the Eindhoven University of Technology is the first to move spontaneously in the presence of sunlight.
 
Previously, researchers have created materials that move when exposed to ultraviolet light. Constant exposure to ultraviolet light, however, often damages the material and isn't useful for all applications.
 
The new material responds to unfiltered sunlight. Researchers say it could offer self-cleaning capabilities to solar cells and other surfaces. It's difficult for sand or dust to settle and accumulate on a material that's constantly oscillating.
 
Scientists at Eindhoven created the material by embedding a thin polymer film with light-sensitive molecules called azo compounds, or azo-dyes. When exposed to light, the film begins to waver irregularly.
 
The researchers aren't yet sure what causes the material to behave this way. "It seems to be a combination of factors," researcher Michael Debije said in a news release. "The light-sensitive molecules bend and stretch under the influence of visible light."
 
"Since these molecules are bound within the polymer network of crystal, this results in the material oscillating as if cramped," Debije explained. "Of course, there's more to it than that -- this is what we are investigating now."
 
While Debije and his fellow researchers continue to explore the phenomenon's chemical and mechanical underpinnings, they hope other scientists will explore the material's applications.

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