¡°Plastics¡± return to original meaning, but with light
( 01 Dec 2005 )
The word ¡°plastic¡±originally characterized only the material¡¯s qualities: It is malleable, pliable, and deformable.
Now, researchers at theMassachusetts Institute of Technology have developed plastics that change shape when the researchers exposed them to specific wavelengths and return to their original shape when the researchers exposed them to other wavelengths. Although materials that deform and return to original shape in response to temperature have been available for many years, such thermoplastics are not sensitive to light. The new class of plastics could find use in light-driven medical devices that change to their final shape after implantation into a bodyand then become active using light and an optical fiber.
The light-sensitive plastic uses photosensitive polymer switches in a film, which the researchers stretched with external stress and then exposed to UV light. The light causes the switches to cross-link, or bind, to each other. The cross links remain when a user turns off the light and change their structure when light energizes the links. For more information, go to http://web.mit.edu/newsoffice/2005/print/smart-plastics-print.html
