How bacteria can power micro-machines

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 Mr 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.