Water is among the most important compounds for life on Earth, if not the most important compound, so it is a good thing there is a lot of it on our planet. For that reason researchers have been attempting to create water-responsive films which react to the presence of water. Now researchers at MIT have successfully developed a water-responsive film that is reacts more strongly than previous efforts.
The material itself is made of two polymer films; one of polypyrrole and the other of polyol-borate. The polypyrrole creates a hard, flexible matrix to support the material while the polyol-borate is a softer gel which swells as it absorbs water. When the researchers placed this combination on a moist surface the water gradient between the dry air and the surface caused the material to absorb some water vapor. This then caused it to deform by rolling up, which exposes its bottom to the dry air, causing it to release the water vapor and return to its original shape.
The researchers weighted the 20 micron thick film to measure its strength and found it could lift glass slides 380 times its weight or transport silver wires 10 times its weight. As this powerful response was achieved with very little moisture, the researchers are interested in this material for artificial muscles in a variety of technologies and for generating electricity.