A 20-micrometer-thick plastic film flips when exposed to water vapor, creating the potential for its use in medical applications such as an artificial muscle.
One of the materials used in the copolymer film, polypyrrole, forms a hard, flexible structure and the other polymer, polyol-borate, is a soft gel that swells when it absorbs water.
"We are very excited about this new material, and we expect as we achieve higher efficiency in converting mechanical energy into electricity, this material will find even broader applications," says Robert Langer, the David H. Koch Institute Professor at MIT and senior author of the paper.
"With a sensor powered by a battery, you have to replace it periodically. If you have this device, you can harvest energy from the environment so you don't have to replace it very often," says Mingming Ma, a postdoc at MIT's David H. Koch Institute for Integrative Cancer Research and lead author of a paper describing the new material in the Jan. 11 issue of Science....