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To solve a big environmental problem, chemists have been thinking small. Really small: a new mini robot with the purpose of helping clean up tiny plastic that pollutes water across the world.

The new microrobots, each of which is no bigger than the tip of a pencil, are magnetic(有磁性的)and shaped like four-pointed stars. When the sunlight shines on them, they can swim in a direction; when the sunlight disappears, they stop moving. Finding a piece of plastic, they hold onto it, produce chemical reactions and start to break it down.

The project is led by chemist Martin Pumera, a researcher who also studies ways to build microrobots at the Czech University of Chemistry and Technology in Prague. About ten years ago, he noticed the microplastic was everywhere, from the bottom of the ocean to the ice on the top of mountains. It even turned up in drinking water, both bottled and tap water. Just think about how much plastic you meet every day. It doesn’t easily degrade ( 降 解 ) which is a big problem. Therefore, Pumera chose to focus on the problem of water pollution caused by microplastic.

The researchers tested the microrobots on four types of plastic in the lab. After a week, all four began degrading, losing around 3 percent of their weight, which showed the microrobots were breaking the plastic down. The robots also turned the plastic’s smooth surface into the rough one. Finally, the scientists showed that magnets could attract the microrobots at the end of the test - along with the plastic waste.

In fact, Pumera says they still have a long way to go. These microrobots are unlikely to succeed in degrading all types of plastic. They’ll also need a lot of testing to show that they’re safe in open waterways, such as at sea. But he thinks that these challenges can be overcome. Someday, the microrobots will play a big role in a worldwide cleanup effort.