Pieces of plastic ranging from nanometers to millimeters in size are amassing in oceans and fresh water. Removing the pollutants is challenging. Conventional methods such as filtration and centrifugation, in addition to being costly and impractical to use on large water bodies, can remove microplastic bits 1 µm to 5 mm in width; they can’t easily capture nanoplastics under 1 µm wide.
Now researchers have developed a porous mesh with a fuzzy surface that traps microplastics and nanoplastics from water (Sci. Adv. 2026, DOI: 10.1126/sciadv.aeg0819). Lab tests suggest that you can drop the meshes in an aquifer and then scoop them up along with the plastic bits, says Orlin D. Velev, a chemical engineer at North Carolina State University.
“In the real world, you can’t guarantee that all meshes will be captured,” he says. “So they have to be made of biodegradable, potentially inexpensive material. That’s why we use alginate and chitosan.” These biopolymers, derived from seaweed and shellfish skeletons, respectively, are widely available.
A researcher, blurry in the background, holds a square of white mesh in a gloved hand.
This biodegradable mesh, made of a porous fibrous material composed of the biopolymers alginate and chitosan, can trap nanometer-to-millimeter-sized plastic particles.
Credit:
Haeleen Hong, Byeunggon Kim, and Orlin D. Velev/North Carolina State University
Velev and colleagues took inspiration from tangled seaweed mats and fibrous balls of dead seagrass that have been found to snag plastic fibers and fragments.
The team used alginate to make materials they call soft dendritic colloids (SDCs). These are particles with hierarchical branches that give them a fuzzy appearance under a microscope and, much like gecko feet, create a large surface area that boosts van der Waals forces and makes the material really sticky. Velev says a single SDC particle can capture more than a thousand polymer particles from a suspension (Adv. Funct. Mater. 2025, DOI: 10.1002/adfm.202423494).
For practical use, the researchers have now fashioned a porous, strong mesh using the SDCs. They mold the SDCs into a mesh, which they freeze and thaw a few times. Ice crystals squeeze the SDCs, packing them tight, and when the ice melts, it leaves behind tiny pores in the packed material. Finally, the researchers attach a layer of chitosan SDCs on the surface of the mesh.
This design creates structures at several scales to capture particles spanning a wide size range. The small openings in the mesh capture larger microplastic particles, while nanoplastics and smaller microplastics stick to it via van der Waals and electrostatic interactions.
In lab tests, the researchers found that the fluffy nets captured lab-made plastic bits and those collected from a beach. The particles ranged in size from 300 nm to several millimeters, were of all shapes and sizes, including microfibers, and had varying surface charges. Most microplastics in natural aquifers have a negative surface charge. The mesh removed over 90% of all the negatively charged and neutral plastic and over 30% of the positively charged particles.
“The key advance is in the use of a hierarchical materials architecture,” says Bhuvnesh Bharti, a chemical engineer at Louisiana State University. The material’s performance in natural waters still needs to be evaluated, and fouling could be a concern in those settings, he says. But the biodegradability, use of inexpensive biopolymers, and simple fabrication are “favorable attributes. The work lays the foundation of future development of collector materials . . . for broad-spectrum microplastic capture and removal.”
Prachi Patel is a senior editor and physical sciences reporter at C&EN based in Pittsburgh.