Tiny Robots Could Clean Up Microplastic Pollution
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Tiny Robots Could Clean Up Microplastic Pollution
In a proof-of-concept study, microscopic self-propelled devices found and broke down microplastic particles
Microplastics—minuscule,
hard-to-degrade fragments of clothing fibers, water bottles and other
synthetic items—have made their way into air, water and soil around the world.
Now new research published in ACS Applied Materials & Interfaces shows a way to promote their deterioration, at least in water, with
technology on an even smaller scale: microrobots. When added to water
along with a bit of hydrogen peroxide, the bacterium-sized devices glom
onto microplastic particles and begin breaking them down.
The metallic microrobots are shaped like four-pointed stars and
coated with magnetic particles. Exposure to visible light causes
electrons in the devices to absorb energy from and react with the
surrounding water and hydrogen peroxide (a process called
photocatalysis), making the bots move. “They can sweep a much larger
area than you would be able to touch with stationary technology,” says
study co-author Martin Pumera, a researcher at the University of
Chemistry and Technology, Prague. As the microrobots adhere to plastic,
photocatalysis also produces charged molecules. These break chemical
bonds in the plastic's molecules, like a jeweler snipping bracelet
links.
The researchers tested the microrobots on four types of plastic.
After a week, all four had begun degrading, losing between 0.5 and 3
percent of their weight. In another test, the microrobots propelled
themselves through a small channel and were collected by a magnet,
bringing up to 70 percent of microplastic particles along for the ride.
Pumera envisions releasing future iterations of the bots into the sea
to latch onto microplastics, then collecting the bots for reuse. But
Win Cowger, who studies plastic pollution at the University of
California, Riverside, and was not involved in the study, says any
microrobots' potential usefulness is likely limited to closed systems
such as those used to treat drinking water or wastewater.
Cowger notes that the current bots can also adhere to substances
other than plastic and might not be safe if left in the water in large
numbers. Pumera's team is now testing microrobots made from different
materials that could address both concerns and could operate without
hydrogen peroxide.
“The work is indeed highly interesting, but it needs further
investigation to make this approach a really viable and potentially
attractive technology to deal with the huge scale of microplastics,”
University of Oxford chemists Peter Edwards and Sergio Gonzalez-Cortes
wrote in an e-mail. The two researchers, who were not involved in the
study, have proposed using microwave radiation to break down plastic
waste.
For now, Cowger says, “the best way to remove microplastics from the
environment is to stop them from getting there in the first place.”
This article was originally published with the title "Tiny Trash" in Scientific American 325, 3, 21 (September 2021)
doi:10.1038/scientificamerican0921-21b
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