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Could evaporating water be the newest renewable energy source? Columbia researchers harnesses the power of bacterial spores

A biophysicist at Columbia University has discovered how to tap evaporating water as an electrical energy source using a simple device made from bacterial spores, glue, and LEGO bricks. Ozgur Sahin’s findings operate at the cellular level, based around his research on the Bacillus bacteria, a microorganism commonly found in soil—and its implications could potentially be far reaching. In high humidity, the spores absorb moisture from the air, expanding up to 40 percent in volume. In dry conditions, the reverse occurs. “Changing size this much is highly unusual for a material that is as rigid as wood or plastic, said Sahin, associate professor of Biological Sciences and Physics at Columbia University. “We figured that expanding and contracting spores can act like a muscle, pushing and pulling other objects. We noticed that we could harness the motion of spores and convert it to electrical energy.” Sahin’s prototype generator is modeled after a wind turbine, which captures kinetic energy and converts it into electricity. Attached to the generator is a flexible, elastic rubber sheet coated in a thin layer of spores. Using a fan and a small container of water, Sahin’s team showed that dry laboratory air and the evaporating moisture from the surface of the water can cause the entire sheet to curl up and straighten, rotating the turbine back and forth to yield electricity. “The biggest form of energy transfer in nature is evaporation. Our climate is powered by evaporating water from oceans and we have no direct way of accessing this energy,” Sahin pointed out. In a paper published in Nature Nanotechnology earlier this year, Sahin and his team, ExtremeBio, consisting of collaborators from Harvard University and the Loyola University Medical Center, showed that these spores produced a thousand times more force than human muscles, and that even a little moisture from evaporation could trigger movement strong enough to be harvested. “The subtle phenomenon of evaporation has big potential. This may be an opening for a completely new energy platform,” said Sahin, whose findings also bode the possibility of developing environmentally benign batteries and engineering stronger materials that mimic muscular movement in robots and prosthetic devices. Pound for pound, the spores pack more energy than other materials used in engineering for moving objects, according to Sahin’s paper. The ramifications are simply enormous in terms of energy savings for the construction and other industries, as well as possibly circumventing the depletion of fossil fuels. In an online issue of Nature Communications, Columbia University scientists reported the development of two novel devices powered entirely by evaporation – a floating, piston-driven engine dubbed the Moisture Mill, which generates electricity and causes a light to flash, and a rotary engine that drives a miniature car. Both devices contain a thin layer of spores. When the evaporation energy is scaled up, researchers predict that it could one day produce electricity from giant floating generators on bays or reservoirs, or from huge rotating machines like wind turbines that sit above water.