Ferrofluid's magnetic properties enable improved water filtration technologies // Photo: insidewater.com.au .
The idea to create an efficient and affordable water filtration system came to Heller, then a high school student, in early 2024. She worked hard on the project during the summer of the same year, and in January 2025 she created a working prototype.
The prototype is a container with a filtration system, which the girl called a “rotating magnifying vial”. This kind of container with an airtight lid and gasket is used for experiments in the laboratory.
Experimentation and perseverance helped her achieve her goal
In her experiments, Heller used a reusable magnetic fluid (ferrofluid) that selectively binds to microplastic particles passing through the filtration system. Although the developed model successfully purified water from microplastics in two stages, the system required constant maintenance. This was due to its inability to recycle the ferrofluid on its own. “If I could create a system that could purify itself and reuse the material, the need for maintenance would be greatly reduced,” recalls the girl, whose words are reported by the resource “Smithsonian Magazine”.
In order to achieve the goal, she continued to experiment. One of the main difficulties was the correct placement of blocks with ferrofluid so that this substance, which is a thick liquid, does not interfere with the passage of water. The solution of this problem was also not to negatively affect the process of magnetic separation with subsequent extraction of ferrofluid. As it is supposed in experiments, for the necessary result the whole process should be debugged, all its components should not interfere with each other.
Mia Heller found the ideal solution after about five iterations (repetitions of the same action – author’s note), after which the working prototype took its final form. The container began to consist of three blocks, the first of which holds the incoming water, the second holds the oil-based ferrofluid, and the third has a magnetic field that allows the ferrofluid to pull the microplastic out of the water. The ferrofluid itself is extracted and reused in a closed loop.
To test the accuracy of the device, the girl developed a sensor that measures several parameters at once – the amount of suspended solids in the liquid, the amount of ferrofluid and microplastic in the filtered water, thanks to which it is possible to calculate the percentage of removed microplastic. Tests showed that the prototype successfully removed 95.52% of the microplastics and recycled 87.15% of the ferrofluid. At the same time, standard wastewater treatment plants and devices do not remove more than 90% of microplastics.
Recognized
Mia Heller’s achievement in 2025 was recognized at the Regeneron International Science and Technology Fair, which is the world’s largest innovation competition for high school students. The U.S. Patent and Trademark Office singled her out, awarding her a special $500 prize and recognizing the innovation, accessibility and efficiency of the new technology.
Prospects for the technology
Toxicologist Matthew Kampen from the University of New Mexico (USA) called the Heller filtration system “a really great idea”. The researcher noted that with a small investment in engineering, much more impressive results could be achieved.
However, there are still some concerns about the safety of this method, because in order to scale up, “you have to make sure that the cleaning process doesn’t leave any sludge of contaminants that would have to be dealt with”.
The toxicologist still has some valid concerns. “We need to be aware that the way it extracts this microplastic captures it in a way that we can then discard or destroy it completely,” he emphasizes. The system, he adds, should not “leave any other sludge of contaminants that we have to deal with.” Assuming that it does remove microplastic components without leaving residue, the next question, he says, is how scalable it is.
The inventor herself considers her system suitable for home use and sees no prospect of producing it on an industrial scale due to the high cost of ferrofluid.
Already a college student, Mia Heller intends to continue working on the project and validate her results on a professional level.
