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Polymer film uses water vapor to create energy – M.I.T.

A new polymer film developed at Massachusetts Institute of Technology enables the generation of power from a novel source – water vapor.

The film changes its shape after absorbing small amounts of evaporated water curling up and down in a repetitive motion, which could be harnessed and used to generate power.

The new film is made from an interlocking network of two different polymers. One is polypyrrole, which forms a hard but flexible matrix for structural support, while the other is polyol-borate, a soft gel that swells when it absorbs water.

When the film lies on a surface that contains even a little amount of water, the bottom layer absorbs it and the film curls up away from the surface. When the bottom is exposed to air, it releases moisture and curls back down only to curl up again. This continuous motion converts the chemical energy of the water gradient into mechanical energy.

The movement of the film is surprisingly strong, according to the researchers. They have used the film to lift a load of glass slides or silver wires, even these loads are hundreds of times the film’s own weight. The movement could be harnessed to run a motor or generator.

Power can be generated directly from the material by combining the polymer film with a piezoelectric material which can convert the mechanical stress or pressure created by the materials movement into an electric charge. The researchers found that an average power of 5.6 nanowatts can be created this way.

On a small scale, the material could be used to power microelectrical mechanical systems such as environmental sensors or nanoelectrics. But the researchers hope to further improve the efficiency of the material in able to provide a continuous source of power for larger devices.

The research was led by Mingming Ma, a postdoc at M.I.T.’s David H. Koch Institute for Integrative Cancer Research and Robert Langer and a professor at the same institute. It was funded by the National Heart, Lung, and Blood Institute Program of Excellence in Nanotechnology, the National Cancer Institute, and the Armed Forces Institute of Regenerative Medicine. – EcoSeed Staff

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