A 3D printer is usually associated with making objects, not cleaning water. But researchers have now used one to create a filter that can remove up to 90% of microplastics from flowing water.
The challenge with microplastics is their size. These plastic fragments are smaller than 5 millimetres, and some are only a few micrometres across. Simply forcing water through a conventional filter does not always capture them efficiently.
Researchers at the University of Waterloo designed a different kind of filter: a stack of thin, 3D-printed discs. The discs are made from polylactic acid (PLA), a biodegradable polymer, but the material is modified during manufacturing to give the filter a much more useful surface.
The trick begins with something called a sacrificial additive. The researchers mix polyethylene glycol into the PLA before printing. After the filter is printed, hot water washes this additive away, leaving behind tiny pores across the surface. Instead of water passing over a relatively smooth piece of plastic, it now encounters a much more complex, porous surface.
The researchers then added pressure-sensitive adhesives to the surface. These make it easier for microplastic particles to remain attached rather than simply being carried away with the water.
They tested columns containing between eight and 20 filter discs. With 20 discs, the system removed about 90% of the microplastics in the experiments. Larger particles were captured particularly well, while particles smaller than 10 micrometres were harder to remove. That remaining fraction is important.
