‘Magic’ lenses make infrared light visible

Researchers have developed an ultra-thin lense that can transform infrared light into visible light.

Lenses are the most widely used optical devices. Camera lens or objectives, for example, produce a sharp photo or video by directing light at a focal point.

The speed of evolution made in the field of optics in recent decades is exemplified by the transformation of conventional bulky cameras into today’s compact smartphone cameras.

Even high-performance smartphone cameras still require a stack of lenses that often account for the thickest part of the phone. This size constraint is an inherent feature of classic lens design—a thick lens is crucial for bending light to capture a sharp image on the camera sensor.

Major strides in the field of optics over the past ten years have sought to overcome this limitation and have come up with a solution in the form of metalenses. They are flat, perform in the same way as normal lenses, and are not only 40 times thinner than an average human hair but also lightweight as they do not need to be made of glass.

A special metasurface composed of structures a mere hundred nanometers in width and height (one nanometer is one billionth of a meter) modifies the direction of light. Using such nanostructures researchers can radically reduce the size of a lens and make it more compact.

When combined with special materials, these nanostructures can be used to explore other unusual properties of light. One example is nonlinear optics, where light is converted from one color into another. A green laser pen works according to this principle: infrared light goes through a high-quality crystalline material and generates light of half the wavelength—in this case green light. One well-known material that produces such effects is lithium niobate. This is used in the telecommunications industry to create components that interface electronics with optical fibres.

Rachel Grange, a professor at the Institute for Quantum Electronics at ETH Zurich, conducts research into the fabrication of nanostructures with such materials. She and her team have developed a new process that allows lithium niobate to be used to create metalenses. The study appears in the journal Advanced Materials.

For her new method, the physicist combines chemical synthesis with precision nanoengineering.

“The solution containing the precursors for lithium niobate crystals can be stamped while still in a liquid state. It works in a similar way to Gutenberg’s printing press,” co-first author Ülle-Linda Talts, a doctoral student working with Grange, explains. Once the material is heated to 600°C (1112°F), it takes on crystalline properties that enable the conversion of light as in the case of the green laser pen.

The process has several advantages. Producing lithium niobate nanostructures is difficult using conventional methods as it is exceptionally stable and hard. According to the researchers, this technique is suitable for mass production as an inverse mould can be used multiple times, allowing the printing of as many metalenses as needed. It is also much more cost-effective and faster to fabricate than other lithium niobate miniaturized optical devices.

Using this technique, the researchers in Grange’s group succeeded in creating the first lithium niobate metalenses with precisely engineered nanostructures. While functioning as normal light focusing lenses, these devices can simultaneously change the wavelength of laser light. When infrared light with a wavelength of 800 nanometers is sent through the metalens, visible radiation with a wavelength of 400 nanometers emerges on the other side and is directed at a designated point.

This magic of light conversion, as Grange calls it, is only made possible by the special structure of the ultra-thin metalens and its composition of a material that allows the occurrence of what is known as the nonlinear optical effect. This effect is not limited to a defined laser wavelength, making the process highly versatile in a broad range of applications.

Metalenses and similar hologram-generating nanostructures could be used as security features to render banknotes and securities counterfeit-proof and to guarantee the authenticity of artworks. Their exact structures are too small to be seen using visible light, while their nonlinear material properties allow highly reliable authentication.

Researchers can also use simple camera detectors to convert and steer the emission of laser light to make infrared light—in sensors, for example—visible. Or for reducing the equipment needed for deep-UV light patterning in state-of-the-art electronics fabrication.

The field of such ultra-thin optical elements—known as metasurfaces—is a relatively young branch of research at the interface between physics, materials science and chemistry.

“We have only scratched the surface so far and are very excited to see how much of an impact this type of new cost-effective technology will have in the future,” emphasizes Grange.

The study was funded in part by an SNFS Consolidator Grant to Rachel Grange.

Source: ETH Zurich

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Is the plastic in your kitchen dangerous for your health?

Plastic containers and utensils are staples in many kitchens—but could they be affecting your health?

Plastics, often seen as a single material, are actually made from many different polymers, each with a unique chemical makeup. They contain different chemical additives like dyes, plasticizers, and flame retardants. As these plastics interact with microbes and environmental chemicals, the risk to human health becomes more complex.

One of the most common ways people are exposed to plastics is in the kitchen:

• Black plastic spatulas and other utensils may contain harmful chemicals picked up when recycled from electronic waste.
• Plastic cutting boards shed tiny fragments of varying shapes and sizes that can be ingested.
• Plastic containers can leach chemicals when heated in the microwave.
• Plastic food containers

Black plastic & your health

Black plastic is commonly used in kitchen utensils, takeout containers, food trays, and children’s toys. But many of these products are made from recycled electronic waste, which can contain harmful chemicals like brominated flame retardants and heavy metals. These chemicals have been linked to a variety of health concerns, including:

• cancer
• endocrine disruption
• neurotoxicity
• infertility

A recent study found flame retardants in 85% of 203 tested consumer products, including banned chemicals, suggesting they were made from old electronic waste.

Are plastics a risk for kids?

Children are more vulnerable to environmental chemicals because their bodies and brains are still developing.

“Flame retardants have been detected in breast milk samples across the US. Children can also be exposed through contaminated food and house dust,” says Jane van Dis, assistant professor of obstetrics and gynecology at University of Rochester Medical Center.

Some plastic toys contain flame retardants that may leach out when children chew on them, exposing children to chemicals that can affect brain and reproductive system development.

Plastic cutting boards

A recent study tried to mimic everyday exposure by feeding mice microplastics made by chopping on real plastic cutting boards. The results showed that different plastics caused different health effects: one type led to gut inflammation, while another changed the gut bacteria. This suggests that real-life plastic exposure is more complicated than lab studies conducted on single types of standard particles might suggest.

In an invited commentary on the study, the co-directors of the Lake Ontario MicroPlastics Center (LOMP), Katrina Korfmacher, professor of environmental medicine at the University of Rochester Medical Center, and Christy Tyler, professor at RIT, reflected on how much plastic we might be adding to our food just by preparing meals at home using plastic tools and containers.

They emphasize that while microplastic exposure is a growing concern, we still don’t fully understand how it affects human health. For instance, although lab studies link microplastics to gut inflammation, only a small percentage of people have such symptoms.

How can you limit exposure?

“The ways that flame retardants and other harmful chemicals end up in plastics we use on a daily basis are complex, as are the solutions,” says Korfmacher.

Still, there are simple ways to reduce exposure:

• Choose wood or stainless steel utensils over black plastic.
• Avoid microwaving food in plastic containers.
• Wash hands and wipe down surfaces after handling plastic packaging.
• Don’t let young children chew on plastic toys.

“These substances are known endocrine disruptors, meaning they can interfere with hormonal systems and potentially lead to various health issues,” says van Dis.

In the long run, they argue that better testing, safer alternatives, and preventing electronic waste from entering the production of consumer products—especially those that come in contact with food—need to occur to reduce sources of exposure.

Source: University of Rochester

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Listen: Are we training AI to think too much like humans?

James Evans believes we’re training AI to think too much like humans—and it’s holding science back.

In this episode of the Big Brains podcast, Evans, a University of Chicago sociologist and data scientist, shares how our current models risk narrowing scientific exploration rather than expanding it.

He also digs into why he’s pushing for AIs that think differently from us—what he calls “cognitive aliens.”

Could these “alien minds” help us unlock hidden breakthroughs? And what would it take to build them?

Read the transcript of this episode.

Source: University of Chicago

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‘Smart’ dental implants could feel more like the real thing

Researchers are developing “smart” dental implants that would provide a more natural feel while chewing or talking.

Each year, millions of people in the US get dental implants as a long-term, natural-looking fix for missing teeth. But traditional implants don’t fully mimic real teeth.

Researchers recently described a new approach to dental implants that that could better replicate how natural teeth feel and function.

Their study in Scientific Reports shows early success with both a “smart” implant and a new gentler surgical technique in rodents.

“Natural teeth connect to the jawbone through soft tissue rich in nerves, which help sense pressure and texture and guide how we chew and speak. Implants lack that sensory feedback,” says Jake Jinkun Chen, a professor of periodontology and director of the Division of Oral Biology at the Tufts University School of Dental Medicine and the senior author on the study.

Traditional dental implants use a titanium post that fuses directly to the jawbone to support a ceramic crown, and the surgery often cuts or damages nearby nerves. To tie these inert pieces of metal into the body’s sensory system, the researchers developed an implant wrapped in an innovative biodegradable coating.

This coating contains stem cells and a special protein that helps them multiply and turn into nerve tissue. As the coating dissolves during the healing process, it releases the stem cells and protein, fueling the growth of new nerve tissue around the implant.

The coating also contains tiny, rubbery particles that act like memory foam. Compressed so that the implant is smaller than the missing tooth when it’s first inserted, these nanofibers gently expand once in place until the implant snugly fits the socket. This allows for a new minimally invasive procedure that preserves existing nerve endings in the tissue around the implant.

“This new implant and minimally invasive technique should help reconnect nerves, allowing the implant to ‘talk’ to the brain much like a real tooth,” explains Chen.

“This breakthrough also could transform other types of bone implants, like those used in hip replacements or fracture repair.”

Six weeks after surgery, the implants stayed firmly in place in rats, with no signs of inflammation or rejection.

“Imaging revealed a distinct space between the implant and the bone, suggesting that the implant had been integrated through soft tissue rather than the traditional fusion with the bone,” says Chen. This may restore the nerves around it.

These initial results are promising, but it will take more studies and time—for example, research in larger animal models to look at outcomes, including safety and efficacy—before trials can begin in human volunteers.

The researchers’ next step will be a preclinical study to see if brain activity confirms that the new nerves surrounding the prototype implant indeed relay sensory information.

Source: Tufts University

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Why don’t bats get cancer?

A study to look at why long-lived bats do not get cancer has broken new ground about the biological defenses that resist the disease.

Reported in the journal Nature Communications, researchers found that four common species of bats have superpowers allowing them to live up to 35 years, which is equal to about 180 human years, without cancer.

Vera Gorbunova and Andrei Seluanov, members of the University of Rochester biology department and Wilmot Cancer Institute, led the work.

Key discoveries

• Bats and humans have a gene called p53, a tumor-suppressor that can shut down cancer. (Mutations in p53, limiting its ability act properly, occur in about half of all human cancers.) A species known as the “little brown” bat—found in Rochester and upstate New York—contain two copies of p53 and have elevated p53 activity compared to humans. High levels of p53 in the body can kill cancer cells before they become harmful in a process known as apoptosis. If levels of p53 are too high, however, this is bad because it eliminates too many cells. But bats have an enhanced system that balances apoptosis effectively.
• An enzyme, telomerase, is inherently active in bats, which allows their cells to proliferate indefinitely. This is an advantage in aging because it supports tissue regeneration during aging and injury. If cells divide uncontrollably, though, the higher p53 activity in bats compensates and can remove cancerous cells that may arise.
• Bats have an extremely efficient immune system, knocking out multiple deadly pathogens. This also contributes to bats’ anti-cancer abilities by recognizing and wiping out cancer cells, Gorbunova says. As humans age, the immune system slows, and people tend to get more inflammation (in joints and other organs), but bats are good at controlling inflammation, too. This intricate system allows them to stave off viruses and age-related diseases.

How does the research apply to humans?

Cancer is a multistage process and requires many “hits” as normal cells transform into malignant cells. Thus, the longer a person or animal lives, the more likely cell mutations occur in combination with external factors (exposures to pollution and poor lifestyle habits, for instance) to promote cancer.

One surprising thing about the bat study, the researchers say, is that bats do not have a natural barrier to cancer. Their cells can transform into cancer with only two “hits”—and yet because bats possess the other robust tumor-suppressor mechanisms, described above, they survive.

Importantly, the authors say, they confirmed that increased activity of the p53 gene is a good defense against cancer by eliminating cancer or slowing its growth. Several anti-cancer drugs already target p53 activity and more are being studied.

Safely increasing the telomerase enzyme might also be a way to apply their findings to humans with cancer, Seluanov adds, but this was not part of the current study.

The National Institute on Aging supported the research.

Source: University of Rochester

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Bed bugs may be the first human pest

Bed bugs are most likely the first human pest, new research shows.

Ever since a few enterprising bed bugs hopped off a bat and attached themselves to a Neanderthal walking out of a cave 60,000 years ago, bed bugs have enjoyed a thriving relationship with their human hosts.

Not so for the unadventurous bed bugs that stayed with the bats—their populations have continued to decline since the Last Glacial Maximum, also known as the ice age, which was about 20,000 years ago.

A team led by two Virginia Tech researchers recently compared the whole genome sequence of these two genetically distinct lineages of bed bugs.

Published in Biology Letters, their findings indicate the human-associated lineage followed a similar demographic pattern as humans and may well be the first true urban pest.

“We wanted to look at changes in effective population size, which is the number of breeding individuals that are contributing to the next generation, because that can tell you what’s been happening in their past,” says Lindsay Miles, lead author and postdoctoral fellow in the entomology department at Virginia Tech.

According to the researchers, the historical and evolutionary symbiotic relationship between humans and bed bugs will inform models that predict the spread of pests and diseases under urban population expansion.

By directly tying human global expansion to the emergence and evolution of urban pests like bed bugs, researchers may identify the traits that co-evolved in both humans and pests during urban expansion.

“Initially with both populations, we saw a general decline that is consistent with the Last Glacial Maximum; the bat-associated lineage never bounced back, and it is still decreasing in size,” says Miles, an affiliate with the Fralin Life Sciences Institute. “The really exciting part is that the human-associated lineage did recover and their effective population increased.”

Miles points to the early establishment of large human settlements that expanded into cities such as Mesopotamia about 12,000 years ago.

“That makes sense because modern humans moved out of caves about 60,000 years ago,” says Warren Booth, an associate professor of urban entomology. “There were bed bugs living in the caves with these humans, and when they moved out they took a subset of the population with them so there’s less genetic diversity in that human-associated lineage.”

As humans increased their population size and continued living in communities and cities expanded, the human-associated lineage of the bed bugs saw an exponential growth in their effective population size.

By using the whole genome data, the researchers now have a foundation for further study of this 245,000 year old lineage split. Since the two lineages have genetic differences yet not enough to have evolved into two distinct species, the researchers are interested in focusing on the evolutionary alterations of the human-associated lineage compared with the bat-associated lineage that have taken place more recently.

“What will be interesting is to look at what’s happening in the last 100 to 120 years,” says Booth. “Bed bugs were pretty common in the old world, but once DDT [dichloro-diphenyl-trichloroethane] was introduced for pest control, populations crashed. They were thought to have been essentially eradicated, but within five years they started reappearing and were resisting the pesticide.”

Booth, Miles, and graduate student Camille Block have already discovered a gene mutation that could contribute to that insecticide resistance in a previous study, and they are looking further into the genomic evolution of the bed bugs and relevance to the pest’s insecticide resistance.

Additional collaborators on this research are from Virginia Commonwealth University, University of Arkansas, University of Texas at Arlington, Harvard University and Broad Institute of MIT and Harvard, and the Czech University of Life Sciences.

Source: Virginia Tech

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Team maps Neanderthal travels across Europe and Eurasia

Anthropologists have mapped Neanderthals’ long and winding roads across Europe and Eurasia.

Recent scholarship has concluded that Neanderthals made a second major migration from Eastern Europe to Central and Eastern Eurasia between 120,000 and 60,000 years ago.

But the routes they took have long been a mystery—primarily because there are few archaeological sites connecting the two regions.

In a new analysis, a team of anthropologists—using computer simulations—has offered a map of possible pathways, which concludes Neanderthals likely used river valleys as natural highways and traveled during warmer periods to move approximately 2,000 miles (3,250 km) in less than 2,000 years.

“Our findings show that, despite obstacles like mountains and large rivers, Neanderthals could have crossed northern Eurasia surprisingly quickly,” explains Emily Coco, who began the study as a New York University doctoral student and is now a postdoctoral researcher at Portugal’s University of Algarve.

The research, which appears in the journal PLOS One, was conducted with Radu Iovita, an associate professor at NYU’s Center for the Study of Human Origins.

“These findings provide important insights into the paths of ancient migrations that cannot currently be studied from the archaeological record and reveal how computer simulations can help uncover new clues about ancient migrations that shaped human history,” observes Coco.

In building their simulation of Neanderthals’ two-millennia journey, Coco and Iovita considered the elevation of the terrain, reconstructed ancient rivers, glacial barriers, and temperature to model movement decisions of individuals—an approach similar to that used to model both modern human and animal movement, but not previously applied to Neanderthals.

The authors find possible migration routes in two ancient periods—Marine Isotope Stage 5e [MIS 5e] (beginning approximately 125,000 years ago) and Marine Isotope Stage 3 [MIS 3] (beginning approximately 60,000 years ago)—marked by warmer temperatures and therefore more suitable for movement.

Computer simulations, conducted on the NYU Greene Supercomputer Cluster, indicated that Neanderthals could have reached Eurasia’s Siberian Altai Mountains within 2,000 years during either MIS 5e or MIS 3 using multiple possible routes that all follow the same basic northern path through the Ural Mountains and southern Siberia, often intersecting with known archaeological sites from the same time periods.

The authors add that the study sheds light on Neanderthal interactions with other ancient human groups. Specifically, their routes would have taken them into areas already occupied by Denisovans—consistent with existing evidence of interbreeding between the two species.

“Neanderthals could have migrated thousands of kilometers from the Caucasus Mountains to Siberia in just 2,000 years by following river corridors,” says Iovita.

“Others have speculated on the possibility of this kind of fast, long-distance migration based on genetic data, but this has been difficult to substantiate due to limited archaeological evidence in the region. Based on detailed computer simulations, it appears this migration was a near-inevitable outcome of landscape conditions during past warm climatic periods.”

Source: NYU

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