Stealing a trick from a tiny, pickle-shaped creature that dwells in the depths of the ocean, scientists have designed a new polymer that, when exposed to water, can instantly change its rigidity and strength.
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Christoph Weder, an associate professor in the same department at Case, says he and Rowan thought of copying the sea cucumber’s adaptation more than five years ago. Working with marine biologists, they determined that the deep-sea animal accomplished its transformation thanks to fibers made of a protein known as collagen. The tightness of the connections between those fibers determines how stiff the cucumber’s skin is, and is controlled by the animal’s nervous system.

To get their polymer to do the same thing, the Case scientists used fibers found in another deep sea dweller, sea squirts, and also in cotton. When they mixed those fibers - known as cellulose nanofibers - with the rubbery polymer ethylene oxide–epichlorohydrin, they formed a stiff network, “almost glued to each other,” says Weder. Due to the nature of the bonds between the polymer and the fibers, however, water gets between the two substances, weakening the fibers’ adhesion. The material then becomes soft.