Um Ponto De Fuga

quinta-feira, 5 de maio de 2005

Intelligent Plastics

Picture a flower that opens when facing the sunlight. In work that mimics that sensitivity to light, an MIT engineer and his German colleagues have created the first plastics that can be deformed and temporarily fixed into shape by light.
These programmed materials change shape when struck by light at certain wavelengths and return to their original shapes when exposed to light of specific different wavelengths.The discovery, to be reported in the April 14 issue of Nature, could have potential applications in a variety of fields, including minimally invasive surgery. Imagine, for example, a "string" of plastic that a doctor could thread into the body through a tiny incision. When activated by light via a fiber-optic probe, that slender string might change into a corkscrew-shaped stent for keeping blood vessels open.What about staples that open at a flash, or paper clips that relax when you don't need them anymore? Again, light could do the job."This is really a new family of materials that can change from one shape to another by having light shined on them," said Institute Professor Robert Langer of MIT.Langer co-authored the paper with Andreas Lendlein, Hongyan Jiang and Oliver Jünger. Lendlein, a former MIT visiting scientist, is institute director at the GKSS Research Center in Teltow, Germany. With Jiang and Jünger, he is also affiliated with the Institute for Technology and Development of Medical Devices at Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen University in Germany.
Shape memory
Plastics with "shape-memory"--ones that change shape in response to a temperature increase--are well known. In 2001, Langer and Lendlein were the first to report biodegradable versions of these materials in the Proceedings of the National Academy of Sciences.

A sample of "smart" plastic (a) is elongated and irradiated on the right-hand side with ultraviolet light, forming a temporary shape (b). Photos (c) and (d) show the plastic recovering its original shape after exposure to UV light of a different wavelength. Scale is in centimeters. (Photo Credit: GKSS Research Center)
Importa ver sciencedaily


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