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Color-changing strip enables affordable nanoplastic analysis using ordinary microscope

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Color-changing strip enables affordable nanoplastic analysis using ordinary microscope


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

A joint team from the University of Stuttgart in Germany and the University of Melbourne in Australia has developed a new method for the straightforward analysis of tiny nanoplastic particles in environmental samples. One needs only an ordinary optical microscope and a newly developed test strip—the optical sieve. The research results have now been published in Nature Photonics.

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

Plastic waste is one of the central and acute global problems of the 21st century. It not only pollutes oceans, rivers, and beaches but has also been detected in living organisms in the form of microplastics. Until now, environmental scientists have focused their attention on larger plastic residues.

However, it has been known for some time that an even greater danger may be on the horizon: nanoplastic particles. These are much smaller than a human hair and are created through the breakdown of larger plastic particles. They cannot be seen with the naked eye. These particles in the sub-micrometer range can also easily cross organic barriers such as the skin or the blood-brain barrier.

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.

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.

“Compared with conventional and widely used methods such as scanning , the new method is considerably less expensive, does not require trained personnel to operate, and reduces the time required for detailed analysis,” explains Dr. Mario Hentschel, Head of the Microstructure Laboratory at the 4th Physics Institute.

The “optical sieve” 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 edged into a semiconductor substrate.

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 with 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.

“The test strip works like a classic sieve,” explains Dominik Ludescher, Ph.D. student and first author of the publication. Particles ranging from 0.2 to 1 µm can thus be examined without difficulty. The 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 by the resulting color change can be detected. This allows us to determine whether the voids are filled or empty.”

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. “If a particle is too large, it won’t fit into the void and will simply be flushed away during the cleaning process,” says Ludescher.

“If a particle is too small, it will adhere poorly to the well and will be washed away during cleaning.” 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.

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

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 µg/ml. The number and size distribution of the nanoplastic particles could also be determined for this sample using the optical sieve.

“In the long term, the optical sieve will be used as a simple analysis tool in environmental and . The technology could serve as a mobile that would provide information on the content of nanoplastics in water or soil directly on site,” explains Hentschel.

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.

More information:
D. Ludescher et al, Optical sieve for nanoplastic detection, sizing and counting. Nature Photonics (2025). DOI: 10.1038/s41566-025-01733-x. www.nature.com/articles/s41566-025-01733-x

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Color-changing strip enables affordable nanoplastic analysis using ordinary microscope (2025, September 13)
retrieved 13 September 2025
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How Trump’s Plot to Grab Iran’s Nuclear Fuel Would Actually Work

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How Trump’s Plot to Grab Iran’s Nuclear Fuel Would Actually Work


President Donald Trump and top defense officials are reportedly weighing whether to send ground troops to Iran in order to retrieve the country’s highly enriched uranium. However, the administration has shared little information about which troops would be deployed, how they would retrieve the nuclear material, or where the material would go next.

“People are going to have to go and get it,” secretary of state Marco Rubio said at a congressional briefing earlier this month, referring to the possible operation.

There are some indications that an operation is close on the horizon. On Tuesday, The Wall Street Journal reported that the Pentagon has imminent plans to deploy 3,000 brigade combat troops to the Middle East. (At the time of writing, the order has not been made.) The troops would come from the Army’s 82nd Airborne Division, which specializes in “joint forcible entry operations.” On Wednesday, Iran’s government rejected Trump’s 15-point plan to end the war, and White House press secretary Karoline Leavitt said that the president “is prepared to unleash hell” in Iran if a peace deal is not reached—a plan some lawmakers have reportedly expressed concern about.

Drawing from publicly available intelligence and their own experience, two experts outlined the likely contours of a ground operation targeting nuclear sites. They tell WIRED that any version of a ground operation would be incredibly complicated and pose a huge risk to the lives of American troops.

“I personally think a ground operation using special forces supported by a larger force is extremely, extremely risky and ultimately infeasible,” Spencer Faragasso, a senior research fellow at the Institute for Science and International Security, tells WIRED.

Nuclear Ambitions

Any version of the operation would likely take several weeks and involve simultaneous actions at multiple target locations that aren’t in close proximity to each other, the experts say. Jonathan Hackett, a former operations specialist for the Marines and the Defense Intelligence Agency, tells WIRED that as many as 10 locations could be targeted: the Isfahan, Arak, and Darkhovin research reactors; the Natanz, Fordow, and Parchin enrichment facilities; the Saghand, Chine, and Yazd mines; and the Bushehr power plant.

According to the International Atomic Energy Agency, Isfahan likely has the majority of the country’s 60 percent highly enriched uranium, which may be able to support a self-sustaining nuclear chain reaction, though weapon-grade material generally consists of 90 percent enriched uranium. Hackett says that the other two enrichment facilities may also have 60 percent highly enriched uranium, and that the power plant and all three research reactors may have 20 percent enriched uranium. Faragasso emphasizes that any such supplies deserve careful attention.

Hackett says that eight of the 10 sites—with the exception of Isfahan, which is likely intact underground, and “Pickaxe Mountain,” a relatively new enrichment facility near Natanz—were mostly or partially buried after last June’s air raids. Just before the war, Faragasso says, Iran backfilled the tunnel entrances to the Isfahan facility with dirt.

The riskiest version of a ground operation would involve American troops physically retrieving nuclear material. Hackett says that this material would be stored in the form of uranium hexafluoride gas inside “large cement vats.” Faragasso adds that it’s unclear how many of these vats may have been broken or damaged. At damaged sites, troops would have to bring excavators and heavy equipment capable of moving immense amounts of dirt to retrieve them

A comparatively less risky version of the operation would still necessitate ground troops, according to Hackett. However, it would primarily use air strikes to entomb nuclear material inside of their facilities. Ensuring that nuclear material is inaccessible in the short to medium term, Faragasso says, would entail destroying the entrances to underground facilities and ideally collapsing the facilities’ underground roofs.

Softening the Area

Hackett tells WIRED that based on his experience and all publicly available information, Trump’s negotiations with Iran are “probably a ruse” that buys time to move troops into place.

Hackett says that an operation would most likely begin with aerial bombardments in the areas surrounding the target sites. These bombers, he says, would likely be from the 82nd Airborne Division or the 11th or 31st Marine Expeditionary Units (MEU). The 11th MEU, a “rapid-response” force, and the 31st MEU, the only Marine unit continuously deployed abroad in strategic areas, have reportedly both been deployed to the Middle East.



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Amazon’s Spring Sale Is So-So, but Cadence Capsules Are a Bright Spot

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Amazon’s Spring Sale Is So-So, but Cadence Capsules Are a Bright Spot


The WIRED Reviews Team has been covering Amazon’s Big Spring Sale since it began at on Wednesday, and the overall deals have been … not great, honestly. So far, we’ve found decent markdowns on vacuums, smart bird feeders, and even an air fryer we love, but I just saw that Cadence Capsules, those colorful magnetic containers you may have seen on your social media pages, are 20 percent off. (For reference, the last time I saw them on sale, they were a measly 9 percent off.)

If you’re not familiar, they allow you to decant your full-sized personal care products you use at home—from shampoo and sunscreen to serums and pills—into a labeled, modular system of hexagonal containers that are leak-proof, dishwasher safe, and stick together magnetically in your bag or on a countertop. No more jumbled, travel-sized toiletries and leaky, mismatched bottles and tubes.

Cadence Capsules have garnered some grumbling online for being overly heavy or leaking, but I’ve been using them regularly for about a year—I discuss decanting your daily-use products in my guide to How to Pack Your Beauty Routine for Travel—and haven’t experienced any leaks. They do add weight if you’re trying to travel super-light, and because they’re magnetic, they will also stick to other metal items in your toiletry bag, like bobby pins or other hair accessories. This can be annoying, especially if you’re already feeling chaotic or in a hurry.

Otherwise, Capsules are modular, convenient, and make you feel supremely organized—magnetic, interchangeable inserts for the lids come with permanent labels like “shampoo,” “conditioner,” “cleanser,” and “moisturizer.” Maybe you love this; maybe you don’t. But at least if you buy on Amazon, you can choose which label genre you get (Haircare, Bodycare, Skincare, Daily Routine). If this just isn’t your jam, the Cadence website offers a set of seven that allows you to customize the color and lid label of each Capsule, but that set is not currently on sale.



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Fellow Readers, Don’t Miss These E-Reader Sales

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Fellow Readers, Don’t Miss These E-Reader Sales


This is the older Kindle Scribe, but the price and features are the best you’ll get, especially when it’s on sale like this. I still reach for this model even though I have the newer third generation, and keep in mind the second generation will also get some of the newer software and experiences over time. With the sale, it’s half the price of the newer model.

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Kindle Colorsoft and Colorsoft Signature Edition

If you’re already a Kindle reader and looking to upgrade, it’s likely because you want a new feature like a color screen. While the Kobo above is the better buy, if you want to stay in the Kindle ecosystem but add some color to your books, both the Colorsoft and Colorsoft Signature are on sale.

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Kindle (2024, 11th Gen)

If you’re looking to spend as little as possible, the basic Kindle (11th generation) is still a great e-reader and is currently under $100. It can do almost everything the other Kindles can (except the Scribe) on a snappy black-and-white screen. It doesn’t have a warm front light either, but it’s still a great purchase for the price.


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