This 12-year-old girl built a robot that can find microplastics in the ocean Anna Du was one of 30 Broadcom Masters finalists. (Rachael Lallensack/Broadcom Masters)
This 12-year-old girl built a robot that can find microplastics in the ocean
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Anna Du noticed plastic scattered on the shoreline. She was walking along Castle Island’s beach in South Boston. She reached down to pick it up and quickly realized there were many more tiny pieces than she could handle.

“When I realized how many pieces there were. It seemed impossible,” says Du. She was in sixth grade at the time.

Du approached the problem like any good scientist. First, she did a little research. That’s how she learned that 8 million metric tons of plastic end up in the oceans every year and that there's an additional 150 million metric tons that are already there.

Then she got to work building something that could help solve the issue. She built a remote-operated vehicle-also referred to as an ROV. Her ROV could move through water and spot plastics on the ocean floor.

Du submitted her ROV to the Broadcom Masters competition. It is one of the top science, technology, engineering and math (STEM)contests for young students around the world. 

The competition is organized by the Broadcom Foundation and Society for Science and the Public and has been running for eight years. This year, nearly 5,000 sixth, seventh and eighth graders were nominated after competing in regional science fairs. Of those, 2,500 applied online for consideration. That pool was narrowed down to 300 projects dubbed “Broadcom Masters.” The top 30 finalists gathered in Washington, D.C. to showcase their projects. The top prize was $25,000 with additional other cash prizes as well. 

Du’s ROV is made with PVC pipes and is inspired by ROVs of all sorts. For instance, it is like the Curiosity lander that spies on the surface of Mars. It is also like the deep sea arctic Nereid ROV at Woods Hole Oceanographic Institution (WHOI). Du’s ROV has two separate systems-a navigation system and a detection system. The navigation system is pretty simple. It uses propellers to move through the water and a novel combination of fishing weights and foam pool floats that allow it to move up and down.

“The real invention here is the sensing,” said Dana Yoerger. He is a roboticist and engineer who works with WHOI’s Nereid. It is a ROV that travels great distances in the arctic. It hosts a suite of acoustic, chemical and biological sensors on board. In awe of Nereid, Du nicknamed her ROV Nereid Jr. But her vehicle has a different skill set than its namesake. “The ROV is nicely done for a 12-year-old and hers is quite clever,” Yoerger adds.

The detection system, Du agrees, is the “actually cool part.” She uses a high resolution infrared camera along with three different kinds of light to spot the plastic. Du’s detection methods are comprised of two different wavelengths of infrared light. They illuminate the absorption spectra in microplastics and make them stand out from the sand and plant life. 

She also uses visible light to spot unnatural colors that might make the plastics stand out. (Du was also one of ten finalists in the Discovery Education 3M Young Scientist Challenge this year. You can see a demo in her application video.) The apparatus doesn’t actually collect the microplastics, but it does identify where they are accumulating. She has applied for a patent on the functional elements of the ROV.

“She has an impressive basic kind of engineering instinct to break down a problem like this and then go after it,” says Casey Machado, who is also a WHOI engineer who works with Nereid. “She was able to follow that up with the technical work, construction and design to make a working prototype, which is very cool. It’s sounds simple, but it’s a level of thinking that’s really impressive.”

When Du first read about the challenge of locating ocean microplastics that, unlike the Great Pacific Garbage Patch, are not floating on the surface, she knew that an ROV would be the most efficient tool for the task. Taking buckets and buckets of water samples and analyzing them in a lab could never be done to the scale needed. She needed a mobile lab that could find the plastics in-situ.

Du has been attending public events and workshops at MIT since she was five years old. She has picked up the engineering skills necessary to build her ROV from these sessions, maker labs at local libraries and YouTube. She says actually getting her device to move through water well was tricky—even down to choosing the right kind of glue to use to hold the PVC pipes together. Before she added fishing weights, for example, the ROV would flip over when she tried to move it up and down. There was a lot of trial and error as she tested her ROV in Boston Harbor.

When asked about future plans, she mentions wanting to somehow address the effects of climate change.

“Especially with climate change happening all around the world, I think there’s a lot of problems that could be solved with new inventions,” says Du. “Right now, I’m mainly just focusing on plastics because there’s still a long way to go.”

Du credits her parents, who for years have been taking her to MIT’s student outreach activities on weekends, for fostering and supporting her interest in STEM. She says she has been able to meet students and scientists there, and, as a result, has her sights set on attending the university and becoming an engineer.

“I know I want to be an engineer because I like building things to help solve world problems,” says Du. “But I’m not sure what kind of engineer I want to be yet.”

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