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Researchers Bend Plastic With Light

An MIT engineer and German colleagues have created plastics that can be reshaped by illuminating them with ultraviolet light.
MANHASSET, N.Y. — A U.S. engineer and German colleagues have created plastics that can be reshaped by illuminating them with ultraviolet light. The programmed materials switch back to their original shape when exposed to light of different, specific wavelengths.

While it is well known that plastics can change shape when heated, the latest work is the first to show that light alone can change its shape.

"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 Massachusetts Institute of Technology.

In the experiments, photosensitive groups were grafted onto a permanent polymer network. The resulting photosensitive polymer film was stretched and illuminated with UV light of a specific wavelength. This prompted molecular switches to bind to one another.

When the light was switched off and the external stress released, the binding remained in place, maintaining an elongated structure. Exposure to light of another wavelength cleaved the new bonds, allowing the material to spring back to its original shape.

Langer co-authored the paper with scientists from the GKSS Research Center (Teltow, Germany) and from RWTH (Aachen, Germany).

The work, to be reported in the April 14 issue of the journal Nature, could have medical applications in fields such minimally-invasive surgery.

The researchers said the work was funded by a BioFuture Award from the Bundesministerium fur Bildung und Forschung in Germany and a fellowship from the Alexander von Humboldt Foundation.