A mesh that copies tangled seaweed catches plastic from a millimetre down to nanometres
Sargassum rafts and seagrass Neptune balls already trap plastic in the ocean. Engineers at North Carolina State built a biopolymer version and showed it captures a range of particle sizes that has defeated most filters.
By Timothy Li
Filters have a size problem. A mesh coarse enough to pass water quickly lets small particles through; a mesh fine enough to catch nanoplastics clogs. A paper in Science Advances from Orlin Velev's group at North Carolina State University, published in August 2026, takes its answer from two things the ocean already does: floating mats of Sargassum seaweed, and the fibrous balls that seagrass forms and rolls onto beaches, which are known to collect plastic as they go.
What they built
The material is made from two biopolymers, alginate from seaweed and chitosan from crustacean shells. The chitosan is processed into what the group calls soft dendritic colloids, structures that branch repeatedly and end in tufts of nanofibres. Woven into a mesh, the result is what Velev calls a fluffy net. The open structure traps particles at the millimetre scale physically, while the nanofibre coating on every strand grabs micro- and nanoscale particles by van der Waals and electrostatic adhesion.
What they found
- In proof-of-concept tests the mesh captured particles from roughly a millimetre down to tens of nanometres, in both fresh and salt water.
- It worked on lab-made model nanoparticles and on real-world microplastics.
- The materials are widely available and biodegradable, and the authors propose collecting loaded mesh and digesting both plastic and mesh microbially.
What it cannot show
The university's release gives no removal-efficiency figures, so the size range is demonstrated but the fraction captured at each size is not public in summary form. It is a laboratory proof of concept. Scaling depends, in Velev's words, on how much anyone wants to invest in scaling up cleanup, and the disposal route is proposed rather than demonstrated. Cleanup also competes with prevention: a mesh in the water does nothing about the tire or the washing machine upstream.
Why it matters here
My own research borrows from fish gill rakers rather than seaweed, but the lesson is the same. Organisms that strain particles for a living solved the clogging problem long ago, usually with hierarchy: coarse structure for flow, fine structure for capture. Copying the hierarchy, not just the pore size, is what makes these designs work.
Read the NC State summary · Hong et al., Science Advances, 2026