![\"bacterial-rotor\"](\"http:\/\/arxivblog.com\/wp-content\/uploads\/2008\/12\/bacterial-rotor-150x150.jpg\" "\\"bacterial-rotor\\"")
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E coli<\/em> bacteria use motors called flagella to generate a force that pushes them along at a rate of up to 10 body lengths per second. That’s a fair rate of knots and in recent years several groups have used this force to turn microrotors. Their approach is to bond the bacteria to a rotor like carthorses to a millstone. That certainly works, but it’s time consuming and fiddly, especially when the workforce dies on you.<\/p>\n But there is a cleverer way, say Luca Angelani and pals from the University of Rome in Italy. Simply place an asymmetric cog in a bath of moving bacteria and they will start it spinning for you.<\/p>\n That sounds a bit like extracting kinetic energy from the random motion of particles, which we know to be impossible because the motion is symmetric in time.<\/p>\n But Angelani and co say there is in important difference between this and bacterial motion: the former is in equilibrium but the latter is an open system with a net income of energy provided by nutrients. This breaks the time symmetry allowing energy to be extracted in the form of directed motion.<\/p>\n Angelani and co calculate that their bacterial bath could turn an asymmetric gear at a rate of a few rpm, which is an interesting result.<\/p>\n “Our findings can open the way to new and fascinating applications in the field of hybrid bio-microdevices engineering, and also provide new insight in the more fundamental aspects of nonequilibrium dynamics of active matter.<\/em> “<\/p><\/blockquote>\n That sounds exciting and the effect doesn’t look hard to confirm experimentally. Which begs the question: what are they waiting for?<\/p>\n