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MIT makes plastic that changes shape in light

Material could one day lead to cartilage replacements that build inside a patient's body or door latches that open with flashlights.

Scientists at the Massachusetts Institute of Technology have come up with a polymer that will change shape and return to its original form when hit with a blast of ultraviolet light.

The material, similar in concept to plastic coatings produced by start-up Ecology Coatings, could one day lead to medical devices that build themselves inside a patient's body, or door latches that can be opened with a flashlight.

"This is really a new family of materials that can change from one shape to another by having light shined on them," MIT professor Robert Langer, one of the inventors, said in a statement. The discovery was detailed in an article published in the magazine Nature this week.

The shape-changing ability is accomplished by attaching photosensitive molecules to a polymer. When exposed to ultraviolet light, the photosensitive particles become active and link to one another, changing the shape of the plastic. Exposing it to light of a slightly different frequency reverses the first reaction, allowing the plastic to return to its original shape.

Spirals can also be created by exposing one area of a polymer film to UV light while leaving another unexposed.

Rather than plastics that re-form, Ecology Coatings is using UV-active materials to create paints that dry in a few seconds. UV light knocks electrons loose and causes a chemical reaction, similar to how free radicals operate in the body, company founder Sally Ramsey said.

Langer and Andreas Lendlein, two of the principal authors of the paper on photosensitive plastics, also published a paper in 2001 on plastics that change, and regain, their shape after being exposed to heat.