News Column

Getting a charge from changes in humidity

February 12, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- The prototype generators work by harnessing the movement of a sheet of rubber coated on one side with spores. The sheet bends when it dries out, much as a pine cone opens as it dries or a freshly fallen leaf curls, and then straightens when humidity rises. Such bending back and forth means that spore-coated sheets or tiny planks can act as actuators that drive movement, and that movement can be harvested to generate electricity.

"If this technology is developed fully, it has a very promising endgame," said Ozgur Sahin, who led the study, first at Harvard'sRowland Institute, later at the Wyss Institute, and most recently at Columbia University, where he's now an associate professor of biological sciences and physics. Sahin collaborated with Wyss Institute Core Faculty member L. Mahadevan, who is also the Lola England de Valpine professor of applied mathematics, organismic and evolutionary biology, and physics at the School of Engineering and Applied Sciences at Harvard University, and Adam Driks, a professor of microbiology and immunology at Loyola University Chicago Stritch School of Medicine. The researchers reported their work yesterday in Nature Nanotechnology.

Water evaporation is the largest power source in nature, Sahin said. "Sunlight hits the ocean, heats it up, and energy has to leave the ocean through evaporation," he explained. "If you think about all the ice on top of Mt. Everest - who took this huge amount of material up there? There's energy in evaporation, but it's so subtle we don't see it."

But until now no one has tapped that energy to generate electricity.

As Sahin pursued the idea of a new humidity-driven generator, he realized that Mahadevan had been investigating similar problems from a physical perspective. Specifically, he had characterized how moisture deforms materials, including biological materials such as pine cones, leaves and flowers, as well as man-made materials such as a sheet of tissue paper lying in a dish of water.

Keywords for this news article include: Wyss Institute for Biologically Inspired Engineering at Harvard.

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Source: Journal of Engineering


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