With mighty bursts of rehydration, bacterial spores offer a new source of renewable energy.
Bacillus spores quickly shrivel in dry times and bloat with a blast of humidity. The transitions, which take about half a second, pack a powerful punch that biophysicist Ozgur Sahin at Columbia University realized could translate to usable energy. By smearing spores onto a flat piece of rubber about the length of a human hand, Sahin and his colleagues developed a spore-powered generator. In arid conditions, parched spores pull the rubber into a curve, while wafts of wet air plump up spores and spring it flat again.
The team linked the rubber to an electromagnetic generator, so that every flex produced an electric current. By weight, spore power rivaled the juice in a car battery, Sahin and colleagues report January 26 in Nature Nanotechnology. Since the spores tote such a high energy potential—more than 1,000 times that of mammalian muscle—Sahin and colleagues say energy-harvesting devices based on the dormant dynamos could be linked into municipal grids to contribute a power boost to homes and cities.
EXPAND AND FLEX Energy can be captured from bacterial spores with an absorbent cortex layer (left) that swells when wet. Researchers spread spores on pieces of latex (above) and harnessed energy from the motion created as spores shriveled and expanded.">