Sandrine Ceurstemont, editor, New Scientist TV
A new super-slippery material is no one-trick pony. Not only capable of repelling just about any liquid, it can just as easily make a sliding drop stop in its tracks. For an encore, it can change colour.
Developed by Xi Yao from Harvard University and colleagues, the adaptive material morphs when deformed thanks to its two-layer structure. An elastic sheet is covered with a liquid film: when stretched, the pores of the underlying material get larger, causing the surface to roughen as the coating changes shape. Pulling the sheet immobilises a sliding drop while also affecting the material's transparency, making it more opaque (see video above).
According to Yao, the dynamic nature of the material makes it more versatile than similar ones that can only be switched from one state to another. The "fabric" could be used to create surfaces that would clean themselves when triggered to flatten, or tents that repel water on rainy days while becoming transparent in the sun. In addition to having tunable wettability and colour, the material could also respond to a variety of other factors, such as temperature, light, chemical signals or magnetic and electric fields.
The system takes inspiration from the way tears in our eyes combine to form a multi-functional film that remains transparent while keeping our eyes moist and clearing out intruding particles.
The material evolved from a previous super-slippery material developed by the team. That rigid surface, which copies the slickness of a carnivorous plant, proved to be even more water-repellent than the leaf that inspired it.
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