Old Microplastics Meet Smart Surfaces

Microplastic pieces that have lived in the environment for years are hard to clean up. Scientists want to know how these tiny particles stick or slip off engineered materials. They studied polystyrene microplastics that had aged in water and tested how they interact with surfaces coated with special chemical layers. The team used a tiny force sensor called an atomic force microscope. They also measured weight changes with a quartz crystal device. Both tools let them see how strong the pull is between the plastic and the surface when water is present. They found that salt levels and acidity in the water change how the particles cling. On surfaces ending with a benzene ring, the pull comes mainly from π‑π stacking—overlap of electron clouds. On surfaces ending with an amine group, the pull is mostly due to electrostatic and cation‑π forces. These tiny forces match what happens on a larger scale, so knowing the micro‑level helps predict how much plastic will stick.Using this knowledge, they created a new cleaning material. It is made from chitosan, a natural polymer, and tannic acid. The mix includes both benzene and amine parts so it can grab plastic in many water types. In tests, the material removed more than 92 % of aged microplastics from water that had a realistic amount of plastic (1 mg per litre). This shows the design works in real conditions. The study links the small‑scale chemistry with big‑picture performance. It gives a clear path for designing future materials that can clean up old microplastics from water.