To deal with a big environmental problem, chemists in the Czech Republic have been thinking small. They are making microrobots with special capabilities. Each new microrobot is no bigger than the tip of a sharpened pencil. When sunlight hits them, they produce chemical reactions that propel (推动) them through water in a specific direction. When they find a piece of plastic, they start to break it down. When the light goes out, they let go and are free to be used again.

Chemist Martin Pumera led the project. He studies ways to build microrobots. About a decade ago, scientists began developing tiny robots that could move in the water. Then they decided to make them do something useful. Pumera chose to focus on the problem posed by microplastics.

“We have a big plastic pollution problem now. Using less plastic is the most important step. After that, we should do some cleaning. This is where I see a role for Pumera’s robots. They’re a really interesting idea to help with cleanup efforts down the road,” says chemist Sherri Mason.

Pumera’s final goal is to make environmentally friendly robots that can be used anywhere in the world. He supposes that at first they might be the most useful in plants that treat wastewater. There they can remove the plastic before it reaches open water. His group is not there yet. But they are getting close. And they want to make the tiny garbage collectors reusable.

In fact, Pumera says they still have a long way to go. There are many types of plastics. And even these microrobots are unlikely to succeed in degrading (降解) them all. The researchers also have not yet shown how safe this system is for the environment. Blackiston, a biologist who did not work on the project, says, “They’ll need a lot of testing to show that they’re safe in open waterways.” But he thinks one day, microrobots can play a big role in a worldwide cleanup effort.

Children grow quickly, especially their feet, but many families cannot buy new shoes each time a child needs them. As a result, about 300 million children around the world go barefoot. Those children risk picking up diseases and parasites(寄生虫) from the soil.

An American man may have a solution for those barefoot kids—a shoe that grows with the child. Kenton Lee is the creator of The Shoe That Grows. He explains how the shoe works and how it is able to last so long.

“It grows in three places: the front; it can also grow on the side with Velcro; and on the back with our buckle. It can last up to five years. The bottom is compressed(压缩的) rubber like tire rubber. The top is just high-quality leather.” The shoe comes in two sizes: small that fits children aged 4 to 9 and large for children aged 9 to 14.

Lee says he got the idea for the shoe while working as a volunteer in an orphanage in Kenya.“...and there was a little girl in a white dress walking next to me. And I just remember looking down and seeing how small her shoes were. They were so small that she had to cut open the front of her shoes to let her toes stick out. And I just remember thinking, “Wouldn’t it be nice if there were a pair of shoes that could grow with her feet?”

However, Lee says it was not easy to turn his idea into a reality. “I kept writing down I should do this because of this or because of that.” Finally, in 2009 Lee founded a non-profit organization called Because International. In the office of Because International, Lee keeps a pair of his own shoes to help him remember his promise. “I told myself I would not get new shoes until the idea was done. So, those are the shoes that I wore for a little over five years.”

Plastic particles have made their way into air, water and soil around the world. Now a new research shows a way to help solve this problem, at least in water, with microrobots. When added to water, the tiny devices gather on plastic particles and begin breaking them down.

When there is light, these star-shaped devices begin to absorb energy from and react with the surrounding water. “Powered by light, the robots move to sweep a much larger area than you can touch with other technologies,” says study co-author Pumera, “As the micro-robots are attached to plastic, some chemicals are produced, breaking down the plastic particles.”

The researchers tested the micro-robots on four types of plastic. After a week, all four began breaking down, losing between 0.5 and 3 percent of their weight. In another test, the micro-robots drove themselves through a small channel and were collected by a magnet, bringing along up to 70 percent of plastic particles pieces for the ride.

Pumera foresees that these robots will be put into the sea to collect plastic particles for reuse. But Cowger, an expert in plastic pollution says micro-robots are probably limited to closed systems, like systems which are used to treat drinking water or wastewater.

Cowger notes that the micro-robots can be attached to substances besides plastic and might not be safe if left in the water in large numbers. For now, Cowger says, “the best way to remove plastic particles is to stop them from getting there in the first place.”

“The work is really interesting, but it needs further experiments to make this approach a really practical technology to deal with the huge numbers of plastic particles,” according to Peter Edwards, a chemist in Oxford.