Scientists have created polymer rods that, even after being grossly deformed, will revert toward their original shape when exposed to ultraviolet (UV) light.
Andreas Lendlein at GKSS Research Center in Teltow, Germany, and his colleagues bestowed this shape-memory property on a polymer blend by adding photosensitive molecules. When exposed to UV light of a certain wavelength, these molecules link, cinching the polymer's own constituent chains in place. A dose of UV light of a different wavelength cleaves the bonds.
In a demonstration of the new material's capabilities, the researchers twisted a rod-shaped sample into a spiral and exposed it to UV light, fixing the shape.