06/04/2026
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"It was up to people to provide their own filtration," says Mia Heller, who was a high school junior in Warrenton, Virginia when she discovered that her family's tap water was contaminated with microplastics and PFAS.
That's at least the case for now since there are no federal regulations requiring water systems to test for or filter microplastics, and municipal treatment plants -- which were never designed to catch them -- let the smallest particles pass right through. So Mia went to her garage and, over five iterations, built a filtration system that removes 95.52% of microplastics from drinking water, using magnetic oil, a homemade sensor, and no membranes to replace.
Mia, now 18, attends Kettle Run High School and spends part of her week taking math, science, and technology classes at Mountain Vista Governor's School. She got the idea in the spring of 2024 after reading a local newspaper article about contamination in her neighborhood's water supply.
Her parents invested in a home filtration system, but Mia watched her mother replace the membrane filters over and over -- expensive, tedious, and never-ending. "It inspired me to design a filter without the use of membranes," she says, "to decrease the costs and maintenance needs associated with water filtration."
She started building in her garage early last year. Her first prototype was simple -- "essentially just a container," she says, with what she called a "spinning magnified vial" inside it. The system used ferrofluid, a reusable magnetic oil, to bind to microplastic particles as water passed through. It worked -- but the ferrofluid couldn't be recovered automatically, which meant constant maintenance. "But if I could create a system that was able to basically clean itself and reuse material," she explains, "the maintenance needs could go down by a lot."
About five iterations later, she found the solution. Her current prototype, about the size of a bag of flour, consists of three modules: one holds the contaminated water, one stores the ferrofluid, and in the smaller third module, a magnetic field pulls the microplastics out of the water while the ferrofluid is recovered and reused in a closed loop.
To test it, she built her own turbidity sensor to measure the microplastics remaining in the filtered water. Her results: 95.52% of microplastics removed, 87.15% of the ferrofluid recovered. Traditional municipal treatment plants -- the ones not designed to filter microplastics -- may incidentally catch some, but the smallest and most concerning particles pass right through.
The scope of the problem her device addresses is staggering. Microplastics have been found in human brain tissue, in bone marrow, in human placenta, and in more than 1,300 species. Their concentration in human brain tissue has increased 50% in less than a decade. They show up in 94% of U.S. tap water samples.
Last year, 175 environmental groups and seven state governors petitioned the EPA to begin monitoring microplastics in drinking water. The agency was supposed to propose a monitoring rule by mid-2025 -- a timeline set under the previous administration. It missed the deadline, and as of now, the rule has yet to be issued.
Mia was a finalist at the 2025 Regeneron International Science and Engineering Fair, the world's largest pre-college science competition, where she received a special award from the Patent and Trademark Office Society for her low-cost, efficient design. She envisions the system as an under-the-sink home filter -- small enough to fit in a kitchen, affordable enough for ordinary families. "I would love to eventually bring it out to market," she says. "I think that would be something that would be really interesting."
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To urge the EPA to begin monitoring microplastics in drinking water, sign the Food & Water Watch petition at https://act.foodandwaterwatch.org/page/76300/action/1?locale=en-US
To watch Mia's presentation of her project at the 2025 Regeneron International Science and Engineering Fair, visit https://www.youtube.com/watch?v=pgb7otEucJ4
To read the People magazine feature on Mia's invention, visit bit.ly/4v3T1Ji
To read more about Mia's filtration system in Smithsonian Magazine, visit https://www.smithsonianmag.com/innovation/this-high-school-student-invented-a-filter-that-eliminates-96-percent-of-microplastics-from-drinking-water-180988363/
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For an inspiring book for tween girls who love to invent and tinker, which includes a variety of hands-on STEM projects, we highly recommend "Gutsy Girls Go for Science: Engineers" for ages 8 to 11 at https://www.amightygirl.com/gutsy-girls-engineers
For two fun picture books about Mighty Girls who love to invent, both for ages 4 to 8, we recommend "Interstellar Cinderella" (https://www.amightygirl.com/interstellar-cinderella) and "Mazie's Amazing Machines" (https://www.amightygirl.com/mazie-s-amazing-machines)
For an inspiring picture book about protecting drinking, we recommend "The Water Princess" for agest 5 to 8 at https://www.amightygirl.com/the-water-princess
For more books about science-loving girls and women, visit our blog post "Ignite Her Curiosity: 60 Children's Books to Inspire Science-Loving Mighty Girls" at https://www.amightygirl.com/blog?p=13914
For more books about girls taking action for the environment, visit our blog post "Mighty Girls Go Green: 30 Girl-Empowering Books for Earth Month" at https://www.amightygirl.com/blog?p=11850
Thanks to People for sharing this image!
