How bacteria can power micro-machines explained

Swarms of bacteria may soon power smartphones as Oxford researchers have found that natural movement of bugs could be harnessed to assemble and activate tiny 'windfarms' in mobile phones.
The study uses computer simulations to demonstrate that the chaotic swarming effect of dense active matter such as bacteria can be organised to turn cylindrical rotors and provide a steady power source.
Researchers say these biologically driven power plants could someday be the microscopic engines for tiny, 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," said Tyler Shendruk from Oxford University in the UK.

"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 Shendruk.
Dense bacterial suspensions are the examples 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, researchers said.

But when scientists immersed a lattice of 64 symmetric microrotors into this active fluid, they 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 windfarm.

"The amazing thing is that we did not have to pre-design microscopic gear-shaped turbines. The rotors just self-assembled into a sort of bacterial windfarm," said 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," he 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, researchers said.

"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," said Amin Doostmohammadi from Oxford University.
"Nature is brilliant at creating tiny engines, and there is enormous potential if we can understand how to exploit similar designs," added Julia Yeomans from Oxford.
The findings were published in the journal Science Advances.