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Bacteria-sized robots take on microplastics and win by breaking them down

Bacteria-sized robots take on microplastics and win by breaking them down
Science
Small pieces of plastic are everywhere, stretching from urban environments to pristine wilderness. Left to their own devices, it can take hundreds of years for them to degrade completely. Catalysts activated by sunlight could speed up the process, but getting these compounds to interact with microplastics is difficult. In a proof-of-concept study, researchers reporting in ACS Applied Materials & Interfaces developed self-propelled microrobots that can swim, attach to plastics and break them down.

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While plastic products are omnipresent indoors, plastic waste and broken bits now litter the outdoors, too. The smallest of these -- microplastics less than 5 mm in size -- are hard to pick up and remove. In addition, they can adsorb heavy metals and pollutants, potentially harming humans or animals if accidentally consumed. So, previous researchers proposed a low-energy way to get rid of plastics in the environment by using catalysts that use sunlight to produce highly reactive compounds that break down these types of polymers. However, getting the catalysts and tiny plastic pieces in contact with each other is challenging and usually requires pretreatments or bulky mechanical stirrers, which aren t easily scaled-up. Martin Pumera and colleagues wanted to create a sunlight-propelled catalyst that moves toward and latches onto microparticles and dismantles them.

To transform a catalytic material into light-driven microrobots, the researchers made star-shaped particles of bismuth vanadate and then evenly coated the 4-8 ?m-wide structures with magnetic iron oxide. The microrobots could swim down a maze of channels and interact with microplastic pieces along their entire lengths. The researchers found that under visible light, microrobots strongly glommed on to four common types of plastics. The team then illuminated pieces of the four plastics covered with the microrobot catalyst for seven days in a dilute hydrogen peroxide solution. They observed that the plastic lost 3% of its weight and that the surface texture for all types changed from smooth to pitted, and small molecules and components of the plastics were found in the left-over solution. The researchers say the self-propelled microrobot catalysts pave the way toward systems that can capture and degrade microplastics in hard-to-reach-locations.

Materials provided by American Chemical Society . Note: Content may be edited for style and length.

American Chemical Society. "Bacteria-sized robots take on microplastics and win by breaking them down." ScienceDaily. ScienceDaily, 10 June 2021. .

American Chemical Society. "Bacteria-sized robots take on microplastics and win by breaking them down." ScienceDaily. www.sciencedaily.com/releases/2021/06/210610135744.htm (accessed June 10, 2021).

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Apr. 21, 2021 — Scientists have designed an enzyme-activated compostable plastic that could diminish microplastics pollution. Household tap water or soil composts break the hybrid plastic material down to reusable ...

June 11, 2020 — Watershed researchers estimate more than 1000 tons of microplastics (equal to more than 123 million plastic water bottles) are deposited in national parks and wilderness areas each year. Researchers ...

Nov. 7, 2019 — A new study helps to solve the mystery of missing plastic fragments at sea. Scientists selected microplastics prevalently found on the ocean surface and irradiated them with a solar simulator system. ...

June 26, 2017 — Billions of pieces of plastic are floating in the oceans. Their effects are also sufficiently well-known: marine animals swallow them or get tangled up in them, which can cause them to die in agony. ...
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