{"id":39007,"date":"2025-09-23T15:30:08","date_gmt":"2025-09-23T15:30:08","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/39007\/"},"modified":"2025-09-23T15:30:08","modified_gmt":"2025-09-23T15:30:08","slug":"a-simple-test-strip-that-reveals-the-invisible-nanoplastic-threat","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/39007\/","title":{"rendered":"A Simple Test Strip That Reveals the Invisible Nanoplastic Threat"},"content":{"rendered":"

\t\t\"Nanoplastic<\/a>Nanoplastic particles made visible: the newly developed test strip from the University of Stuttgart allows dangerous nanoplastic particles to be detected under a light microscope. Credit: University of Stuttgart \/ 4th Physics Institute<\/p>\n

Researchers at the University of Stuttgart have created an \u201coptical sieve\u201d capable of detecting minute nanoplastic particles. Functioning much like a test strip, this innovation is designed to provide a new analytical tool for environmental and health research.<\/p>\n

Researchers from the University of Stuttgart in Germany and the University of Melbourne in Australia have introduced a simple way to analyze very small nanoplastic particles in environmental samples. The approach relies on a standard optical microscope and a newly designed test strip called the optical sieve. The findings are reported in Nature Photonics.<\/p>\n

\u201cThe test strip can serve as a simple analysis tool in environmental and health research,\u201d explains Prof. Harald Giessen, Head of the 4th Physics Institute of the University of Stuttgart. \u201cIn the near future, we will be working toward analyzing nanoplastic concentrations directly on site. But our new method could also be used to test blood or tissue for nanoplastic particles.\u201d<\/p>\n

Nanoplastics as a danger to humans and the environment<\/p>\n

Plastic waste ranks among the most urgent global challenges of the 21st century. It contaminates oceans, rivers, and beaches, and microplastics have been found in living organisms. Until recently, researchers have mainly examined larger fragments of plastic. Evidence now points to an even more concerning threat: nanoplastic particles.<\/p>\n

These particles are far smaller than the width of a human hair, form as bigger pieces of plastic break down, and cannot be seen with the naked eye. At sub-micrometer sizes, they can also pass through biological barriers, including the skin and the blood-brain barrier.<\/p>\n

Color changes make tiny particles visible<\/p>\n

Because of the small particle size, their detection poses a particular challenge. As a result, there are not only gaps in our understanding of how particles affect organisms but also a lack of rapid and reliable detection methods.<\/p>\n

In collaboration with a research group from Melbourne in Australia, researchers at the University of Stuttgart have now developed a novel method that can quickly and affordably detect such small particles. Color changes on a special test strip make nanoplastics visible in an optical microscope and allow researchers to count the number of particles and determine their size.<\/p>\n

\"Optical<\/a>The optical sieve nanoplastic particles fall into holes of the appropriate size in the test strip. The color of the holes changes. The new color provides information about the size and number of particles. Credit: University of Stuttgart \/ 4th Physics Institute<\/p>\n

\u201cCompared with conventional and widely used methods such as scanning electron microscopy, the new method is considerably less expensive, does not require trained personnel to operate, and reduces the time required for detailed analysis,\u201d explains Dr. Mario Hentschel, Head of the Microstructure Laboratory at the 4th Physics Institute.<\/p>\n

Optical sieve instead of expensive electron microscope<\/p>\n

The \u201coptical sieve\u201d uses resonance effects in small holes to make the nanoplastic particles visible. A study on optical effects in such holes was first published by the research group at the University of Stuttgart in 2023. The process is based on tiny depressions, known as Mie voids, which are etched into a semiconductor substrate.<\/p>\n

Depending on their diameter and depth, the holes interact characteristically with the incident light. This results in a bright color reflection that can be seen in an optical microscope. If a particle falls into one of the indentations, its color changes noticeably. One can therefore infer from the changing color whether a particle is present in the void.<\/p>\n

\u201cThe test strip works like a classic sieve,\u201d explains Dominik Ludescher, PhD student and first author of the publication in \u201cNature Photonics\u201d. Particles ranging from 0.2 to 1 \u00b5m can thus be examined without difficulty. \u201cThe particles are filtered out of the liquid using the sieve in which the size and depth of the holes can be adapted to the nanoplastic particles, and subsequently, the resulting color change can be detected. This allows us to determine whether the voids are filled or empty.\u201d<\/p>\n

Number, size, and size distribution of particles can be determined<\/p>\n

The novel detection method used can do even more. If the sieve is provided with voids of different sizes, only one particle of a suitable size will collect in each hole.<\/p>\n

\u201cIf a particle is too large, it won\u2019t fit into the void and will be simply flushed away during the cleaning process,\u201d says Ludescher. \u201cIf a particle is too small, it will adhere poorly to the well and will be washed away during cleaning.\u201d In this way, the test strips can be adapted so that the size and number of particles in each individual hole can be determined from the reflected color.<\/p>\n

Synthesized environmental samples examined<\/p>\n

For their measurements, the researchers used spherical particles of various diameters. These are available in aqueous solutions with specific nanoparticles. Because real samples from bodies of water with known nanoparticle concentrations are not yet available, the team produced a suitable sample themselves.<\/p>\n

The researchers used a water sample from a lake that contained a mixture of sand and other organic components and added spherical particles in known quantities. The concentration of plastic particles was 150 \u00b5g\/ml. The number and size distribution of the nanoplastic particles were also determined for this sample using the \u201coptical sieve.\u201d<\/p>\n

Can be used like a test strip<\/p>\n

\u201cIn the long term, the optical sieve will be used as a simple analysis tool in environmental and health research. The technology could serve as a mobile test strip that would provide information on the content of nanoplastics in water or soil directly on site,\u201d explains Hentschel.<\/p>\n

The team is now planning experiments with nanoplastic particles that are not spherical. The researchers also plan to investigate whether the process can be used to distinguish between particles of different plastics. They are also particularly interested in collaborating with research groups that have specific expertise in processing real samples from bodies of water.<\/p>\n

Reference: \u201cOptical sieve for nanoplastic detection, sizing and counting\u201d by D. Ludescher, L. Wesemann, J. Schwab, J. Karst, S. B. Sulejman, M. Ubl, B. O. Clarke, A. Roberts, H. Giessen and M. Hentschel, 8 September 2025, Nature Photonics.
DOI: 10.1038\/s41566-025-01733-x<\/a><\/p>\n

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