As the fossil fuel era draws to a close, it has become necessary to look for more subtle sources of energy. Researchers at MIT have developed a new polymer film that can generate electricity by drawing on something easily found in nature or created in artificial environments: water vapor.
When exposed to water vapor, this new material changes its shape, repeatedly curling up and down as moisture is absorbed. Treehugger reports that harnessing this continuous motion could drive robotic limbs or generate enough electricity to power micro- and nanoelectronic devices, such as environmental sensors.
According to MIT, the new film is made from an interlocking network of two different polymers. One of the polymers, polypyrrole, forms a hard but flexible matrix that provides structural support. The other polymer, polyol-borate, is a soft gel that swells when it absorbs water.
When even a tiny amount of water is introduced, the bottom layer absorbs it, forcing the film to curl away from the surface. This reaction then exposes the bottom of the film to air, inducing the polymer to release the moisture. As this cycle is repeated, the continuous motion converts the chemical energy of the water gradient into mechanical energy. The contraction and release motion is similar to what our muscle tissues do every day, which is why scientists feel that the material could one day be used to create artificial muscles.
By linking the polymer film with a piezoelectric material, which converts mechanical stress to an electric charge, it could generate an average power of 5.6 nanowatts, which can then be stored in capacitors to power ultra-low-power microelectronic devices