She began work on an underwater device that uses infrared light to detect harmful microplastics in the ocean.
Her invention is now gaining national attention as a finalist in the challenge.
As a finalist, Du will get a chance to work with one of 3M's scientists to take her invention from detecting plastic in her backyard, to detecting it in the world's oceans.
"Science has always been a big part of my life," Du said. "I'm super excited to make something that can actually help the world."
Du wants to go to the Massachusetts Institute of Technology to study marine-related science.
She and the other nine finalists will take part in the final competition in October at the 3M Innovation Center in Saint Paul.