Researchers from the University of Melbourne, working with colleagues from the University of Stuttgart in Germany, have developed a new method to detect nanoplastics that could transform monitoring of plastic pollution worldwide.
The technique, described in Nature Photonics, uses what the team calls an “optical sieve” to identify and categorise nanoplastic particles, which are smaller and more difficult to trace than microplastics.
The approach is designed to be portable, low-cost, and adaptable to a range of real-world environments, the University of Melbourne said in a news release.
Dr Lukas Wesemann, who led the Australian research at the University of Melbourne, said the breakthrough makes it possible to reveal the true extent of nanoplastic contamination.
“Until now, detecting and sizing plastic particles with diameters below a micrometre – one millionth of a metre – 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.
The optical sieve is a microchip made of gallium arsenide that contains an array of tiny cavities. When liquid containing nanoplastics is poured over it, the particles are trapped in cavities matching their size, allowing them to be sorted down to 200 nanometres in diameter.
“Crucially, it requires only an optical microscope and a basic camera to observe distinct colour changes to light reflecting off the sieve, which allows us to detect and count the sorted particles,” Dr Wesemann added.
Associate Professor Brad Clarke, a co-author from the University of Melbourne, said the method could make pollution tracking more accessible.
“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 team tested the method using lake water containing nanoplastics and say it may eventually be used to detect the particles in human 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.
Researchers at the University of Melbourne are now exploring how the technology could be scaled into commercial environmental testing solutions.
The work involved scientists from the Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems and the Australian Laboratory for Emerging Contaminants in the School of Chemistry.
The project received funding support from the Australian Research Council, the European Research Council, the Australia–Germany Joint Research Cooperation Scheme (Universities Australia-DAAD), the University of Stuttgart, and the University of Melbourne.
