World's tiniest wind farm: bacteria could create power sources for microscopic devices

How’s this for a new source of power? Scientists have shown that the movement of bacteria could be harnessed to create microscopic ‘wind farms’ to power tiny devices.

Oxford University researchers used computer modelling to show that the chaotic swarming effect of dense active matter such as bacteria can be used to turn cylindrical rotors and provide a steady power source. These microscopic power plants could become miniscule engines for tiny, man-made devices that are self-assembled and self-powered.

“Many of society’s energy challenges are on the gigawatt scale, but some are downright microscopic. One potential way to generate tiny amounts of power for micromachines might be to harvest it directly from biological systems such as bacteria suspensions,” said Dr Tyler Shendruk from Oxford University’s Department of Physics. Dr Shendruk is the co-author of a paper on the study, which was published in the journal Science Advances.

Dense bacterial suspensions are the quintessential example of active fluids that flow spontaneously. While swimming bacteria are capable of swarming and driving disorganised living flows, they are normally too disordered to extract any useful power from.

But when the Oxford team immersed a lattice of 64 symmetric microrotors into this active fluid, the scientists found that the bacteria spontaneously organised itself in such a way that neighbouring rotors began to spin in opposite directions — a simple structural organisation reminiscent of a wind farm.

“The amazing thing is that we didn’t have to predesign microscopic gear-shaped turbines. The rotors just self-assembled into a sort of bacterial wind farm,” said Dr Shendruk.

“When we did the simulation with a single rotor in the bacterial turbulence, it just got kicked around randomly. But when we put an array of rotors in the living fluid, they suddenly formed a regular pattern, with neighbouring rotors spinning in opposite directions.”

“The ability to get even a tiny amount of mechanical work from these biological systems is valuable because they do not need an input power and use internal biochemical processes to move around,” said co-author Dr Amin Doostmohammadi.

“At micro scales, our simulations show that the flow generated by biological assemblies is capable of reorganising itself in such a way as to generate a persistent mechanical power for rotating an array of microrotors.”