An 18-year-old high school student has developed a promising new water filter that removes over 95% of microplastics from drinking water. Mia Heller, a senior at Kettle Run High School in Virginia, became frustrated after learning that her local tap water contained microplastics and that government agencies were not taking strong action to address the issue. Tired of the expensive, high-maintenance membrane filters her family used at home, she decided to build a better solution in her garage. After months of experimentation, Heller created a prototype filtration system that eliminates 95.52% of microplastics — a performance that rivals or exceeds many conventional technologies, but with far less waste and maintenance. The compact device is roughly the size of a standard home appliance and is designed for easy under-sink use. At the heart of her invention is ferrofluid — a magnetic liquid (based on canola oil in her prototype) that binds to microplastic particles ranging from 1 nanometer to 5 millimeters. As contaminated water flows through the system, a magnetic field pulls the ferrofluid-bound plastics out, producing cleaner water while allowing most of the ferrofluid (about 87%) to be recovered and recycled for repeated use. Heller was a finalist at the 2025 Regeneron International Science and Engineering Fair, where she received a special $500 award from the Patent and Trademark Office Society for her innovative, low-cost, and sustainable approach. She hopes her self-recycling system will eventually reach the consumer market, giving families an affordable and effective tool to reduce their exposure to microplastics, which have been linked to various health concerns.