Mini ‘wind farm’ could capture energy from microbes in motion
Chaotic swirling becomes synchronized swimming to rotate turbines, simulation shows
PINT-SIZED POWER Computer
simulations show how the motion of swimming bacteria could be harnessed
to generate power using a device like the wind farm shown above — but
on a microscopic scale.
Fluid filled with lively, churning bacteria could one day become a small-scale power source.
New computer simulations indicate that a miniature wind farm‒like device could harvest the energy of chaotically swirling bacteria. That energy could be used to power micromachines or pump fluids through tiny channels. In the simulations, bacteria tended to spontaneously swim in an orderly fashion around an array of cylindrical turbines. These turbines then rotated steadily like windmills in a breeze, scientists report July 8 in Science Advances.
Previous research has harnessed the energy of the motion in such chaotic fluids using tiny, asymmetric gears, which spin as bacteria bump into their teeth. But the new result shows that a very simple system can serve the same purpose — a result that could make such devices easier to construct. “You don’t have to muck around with getting the teeth right; you just have a nice smooth cylinder,” says biophysicist and study coauthor Tyler Shendruk of the University of Oxford. The technique would sidestep the need to manufacture complicated microscopic gears.
“I think it’s quite surprising because previous work showed that you need to have a certain nonsymmetry in the system” to generate rotation, says physicist Igor Aronson of Argonne National Laboratory in Illinois, who was not involved with the new work.
TINY TURBINES
Nine rotors in a computer simulation spin in response to the flowing
bacteria-filled liquid surrounding them. Blue rotors spin clockwise, and
red rotate counterclockwise. Green lines indicate the orientation of
the bacteria, and black arrows indicate the flow of the fluid.
The
researchers studied simulations of a liquid filled with many
self-propelled particles, called a dense active fluid. These fluids can
be made up of swimming bacteria or biological motors found inside cells —
for instance, the proteins myosin and actin, which cause muscles to
contract. Such fluids are normally turbulent, with swarms of particles
generating rapidly and unpredictably changing flows. That makes it a
challenge to harvest energy from the fluid. “It’s chaotic, so you can’t
use it to do anything useful because it’s a random flow,” Shendruk says.
New computer simulations indicate that a miniature wind farm‒like device could harvest the energy of chaotically swirling bacteria. That energy could be used to power micromachines or pump fluids through tiny channels. In the simulations, bacteria tended to spontaneously swim in an orderly fashion around an array of cylindrical turbines. These turbines then rotated steadily like windmills in a breeze, scientists report July 8 in Science Advances.
Previous research has harnessed the energy of the motion in such chaotic fluids using tiny, asymmetric gears, which spin as bacteria bump into their teeth. But the new result shows that a very simple system can serve the same purpose — a result that could make such devices easier to construct. “You don’t have to muck around with getting the teeth right; you just have a nice smooth cylinder,” says biophysicist and study coauthor Tyler Shendruk of the University of Oxford. The technique would sidestep the need to manufacture complicated microscopic gears.
“I think it’s quite surprising because previous work showed that you need to have a certain nonsymmetry in the system” to generate rotation, says physicist Igor Aronson of Argonne National Laboratory in Illinois, who was not involved with the new work.
But
when Shendruk and colleagues added a grid of cylindrical rotors, each a
few hundredths of a millimeter in diameter, into their simulated fluid,
they found that bacteria would spontaneously organize, like sailors all
rowing in the same direction. The swimming bacteria produced a circular
fluid flow that spun the rotors. That rotation could be used to
generate electrical power in the same manner as windmills do, but in
much smaller amounts that might be used to power tiny electronics.
Each rotor might produce around a quadrillionth of a watt of electrical power, Shendruk estimates.
A single rotor on its own didn’t work as well: Its spin changed direction periodically as the chaotic fluid swirled around it. But with an array of rotors close together, the bacteria became steady synchronized swimmers squeezing through gaps between the rotors — and making each rotor consistently spin in the direction opposite to that of its neighbors.
The system should translate well from simulation to the real world, says Shendruk, and the researchers are already discussing the possibilities for constructing it. But, says applied mathematician Jörn Dunkel of MIT, the details of the real world are important. Whether the rotors would behave the same way in a real-life system where the rotors experience friction is uncertain. “The effect is there — I don’t doubt that. The question is how strong.”
Each rotor might produce around a quadrillionth of a watt of electrical power, Shendruk estimates.
A single rotor on its own didn’t work as well: Its spin changed direction periodically as the chaotic fluid swirled around it. But with an array of rotors close together, the bacteria became steady synchronized swimmers squeezing through gaps between the rotors — and making each rotor consistently spin in the direction opposite to that of its neighbors.
The system should translate well from simulation to the real world, says Shendruk, and the researchers are already discussing the possibilities for constructing it. But, says applied mathematician Jörn Dunkel of MIT, the details of the real world are important. Whether the rotors would behave the same way in a real-life system where the rotors experience friction is uncertain. “The effect is there — I don’t doubt that. The question is how strong.”
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