Plastic That Changes Shape In Light

JLavezzo writes "Picture a flower that opens when facing the sunlight. In work that mimics that sensitivity to light, MIT Engineer Robert Langer and his German colleagues have created the first plastics that can be deformed and temporarily fixed into shape by light. This material 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. Additional commentary available at The Science Blog"

Comments

Heat and Artificial Muscles?

[Greg Wright]

They, the scientists, have been able to do this for some time with
heat. The link below is to an article that shows a 30 gram weight
being lifted and lowered by a type of polymer know as nematic
elastomers.

http://www.sciam.com/article.cfm?articleID=0007C 55 D-FA8F-1C5F-B882809EC588ED9F

they also say in the above article(link) that, "..light can also induce
shape changes anywhere from 10 to 400 percent [in the polymer]."
However, it takes a hours for it to return to the original shape.

One of the best applications,in my opinion, for any fast-acting shape
changing polymer would be as artificial muscles. Not sure how
practical or easy that might be. You would have to get the temperature
range, where the shape changing takes place, down pretty low and find
a way to control it outside of the body's heat influence. I am sure
there are other problems as well.

clarfication

[morcheeba]

Just to clarify... this plastic changes shape in response to various wavelengths of light... not the quantity, as has been previously done. (Note - the older technology has been adapted for cell phones, too)

Other related work

[karvind]

Another field where MIT work can be useful is space antennae. Here an optical signal would initiate a sequence of changes in the shape, causing the antenna to refocus on a different point in space.

OSU had developed light-tunable plastic magnets. Here the plastic material becomes 1.5 times more magnetic when blue light shines on it. Green light partially reverses that effect.

Another interesting work is from PSU on PLZT, this new material shows a large piezoelectric effect in response to near-ultraviolet light. Piezoelectric materials convert electricity into mechanical energy -- movement. When an electric current is run through piezoelectric ceramic, the ceramic changes size -- it shrinks or expands. Certain ferroelectric materials exhibit stronger photovoltaic (light into electricity) effects. Combining these ferroelectrics with piezoelectrics (electricity into motion), researchers created a single material that would convert light directly into motion.