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TECHFIND - ENERGY
Bacteria Powered Micromachines
According to the finding of a group of scientists, miniature asymmetrically shaped cog wheels rotate continuously in one direction when exposed to swimming bacteria, The scientists built ratchets just a few hundredths of a millimeter across and filmed their motion when immersed in solutions containing E. coli. They took advantage of the fact that a collection of bacteria immersed in a liquid represents a non-equilibrium thermodynamic system by virtue of the self-propulsion of the bacteria. This non-equilibrium system, they say, should bestow ordered motion on an asymmetrically shaped object. Using electron-beam lithography they etched out 10,000 saw-tooth gear wheels from the polymer SU8. They then dispersed the gear wheels in a suspension of E. coli, and hung a droplet of this liquid from the underside of a glass slide. This allowed the gear wheels to accumulate on the liquid-air interface, where they were held by capillary forces and free from the strong adhesion they would experience next to a solid surface. The researchers observed that bacteria would strike the long-edge of each tooth and either bounce off or have their movement blocked by the next short-edge. Given that bacteria do not stop swimming when they meet an obstacle or blockage, this caused them to push continuously against the short edge, with the combined motion of many such bacteria causing he gear wheel to rotate in one specific direction.
Media Spiders®
According to the finding of a group of scientists, miniature asymmetrically shaped cog wheels rotate continuously in one direction when exposed to swimming bacteria, The scientists built ratchets just a few hundredths of a millimeter across and filmed their motion when immersed in solutions containing E. coli. They took advantage of the fact that a collection of bacteria immersed in a liquid represents a non-equilibrium thermodynamic system by virtue of the self-propulsion of the bacteria. This non-equilibrium system, they say, should bestow ordered motion on an asymmetrically shaped object. Using electron-beam lithography they etched out 10,000 saw-tooth gear wheels from the polymer SU8. They then dispersed the gear wheels in a suspension of E. coli, and hung a droplet of this liquid from the underside of a glass slide. This allowed the gear wheels to accumulate on the liquid-air interface, where they were held by capillary forces and free from the strong adhesion they would experience next to a solid surface. The researchers observed that bacteria would strike the long-edge of each tooth and either bounce off or have their movement blocked by the next short-edge. Given that bacteria do not stop swimming when they meet an obstacle or blockage, this caused them to push continuously against the short edge, with the combined motion of many such bacteria causing he gear wheel to rotate in one specific direction.
