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A first-of-its-kind method that's cheap, portable and powerful in detecting harmful nanoplastics particles has been developed by an international consortium of researchers, with far-reaching implications for global health and environmental science.

While the dangers of microplastics are widely recognized, smaller nanoplastics are more insidious, infiltrating food, water, and even human organs, and detecting them has been difficult and expensive.

Described in a paper today in Nature Photonics, researchers at the University of Melbourne and the University of Stuttgart in Germany have developed a novel "optical sieve" to cost-effectively detect, classify and count nanoplastic particles in real-world environments.

Dr. Lukas Wesemann, who led the Australian arm of the research at the University of Melbourne, said the innovation is able to expose the extent of nanoplastics pollution that can persist for centuries, and provides hope for scalable monitoring of this global environmental and health crisis.

"Until now, detecting and sizing plastic particles with diameters below a micrometer—one millionth of a meter—has relied on costly tools such as scanning electron microscopes, and been nearly impossible outside advanced laboratories, leaving us blind to their true impact," Dr. Wesemann said.

"Our novel optical sieve is an array of tiny cavities of varying sizes in a gallium arsenide microchip."

When a liquid containing nanoplastics is poured over the sieve, each plastic particle is captured in a void of matching size, sorting them into categories down to a diameter of 200 nanometers.

"Crucially, it requires only an optical microscope and a basic camera to observe distinct color changes to light reflecting off the sieve, which allows us to detect and count the sorted particles," Dr. Wesemann said.

University of Melbourne Associate Professor Brad Clarke and co-author said the invention could make pollution monitoring far more affordable, accessible and mobile.

"Understanding the numbers and size distribution of nanoplastics is crucial to assess their impact on global health, and aquatic and soil ecosystems," he said.

"Unlike microplastics, smaller nanoplastics can cross biological barriers—including the blood-brain barrier—and accumulate in body tissues, raising profound health concerns of toxic exposure."

The researchers validated the technique using lake water mixed with nanoplastics, with future testing potentially including identifying nanoplastics in blood samples.

"In contrast to existing methods like dynamic light scattering, our new method does not require separating the plastics from biological matter," Dr. Wesemann said.

The researchers are exploring scaling the innovation into a commercially available environmental testing solution.

The team included scientists from the Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems and Australian Laboratory for Emerging Contaminants in the School of Chemistry.