Swarms of bacteria could be used to power smartphones, say experts

A team of Oxford University researchers have found that natural movement of bugs could be harnessed to accumulate and activate tiny “windfarms” in smartphones.

The researchers explained in the journal Science Advances how they used computer simulations to demonstrate that the random swarming effect of dense active matter such as bacteria could be organised to rotate cylindrical rotors and provide a stable and reliable source of electrical power.

Co-author Dr Tyler Shendruk, an EMBO long-term fellow in the Rudolf Peierls Centre for Theoretical Physics at the University of Oxford, and colleagues say that these biologically-driven microscopic power plants could ultimately become the ultra-minute engines for minuscule, man-made devices that are self-assembled and self-powered – everything from optical switches to smartphone microphones.

“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 Shendruk.

Bacterial growth or bloom is usually too disorganised on its own to generate any kind of meaningful power. Hence, when a single rotor was introduced during the experiments, it was ineffective and simply ‘got kicked around’ by the bacteria.

However, the researchers developed a special lattice of 64 micro-rotors and, as the bacteria ‘swarmed’ around, it spontaneously organised itself in such a way that neighbouring rotors began to spin in opposite directions – a simple structural organisation suggestive of a windfarm.

Dr Shendruk added: “The amazing thing is that we didn’t have to pre-design microscopic gear-shaped turbines. The rotors just self-assembled into a sort of bacterial windfarm.

“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.”

Co-author Dr Amin Doostmohammadi, from Oxford University’s Department of Physics, said: “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.

“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.”

Senior author Professor Julia Yeomans, from Oxford University’s Department of Physics, added: ‘Nature is brilliant at creating tiny engines, and there is enormous potential if we can understand how to exploit similar designs.”

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