Monday, August 18, 2025

Researchers send a wireless curveball to deliver massive amounts of data

Princeton University, Engineering School

UH Beams 1 — image:
From left, researchers Haoze Chen, Yasaman Ghasempour, and Atsutse Kludze, have developed a system to curve ultrahigh frequency transmissions through a complex and dynamic environment.
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Credit: Aaron Nathans/Princeton University

High frequency radio waves can wirelessly carry the vast amount of data demanded by emerging technology like virtual reality, but as engineers push into the upper reaches of the radio spectrum, they are hitting walls. Literally.

Ultrahigh frequency bandwidths are easily blocked by objects, so users can lose transmissions walking between rooms or even passing a bookcase. Now, researchers at Princeton engineering have developed a machine-learning system that could allow ultrahigh frequency transmissions to dodge those obstacles. In an August 18 article in Nature Communications, the researchers unveiled a system that shapes transmissions to avoid obstacles coupled with a neural network that can rapidly adjust to a complex and dynamic environment.

Lead researcher Yasaman Ghasempour, an assistant professor of electrical and computer engineering at Princeton, said the work is an important step toward deploying data transmission in the sub-terahertz band, which is at the upper end of the microwave spectrum.

Transmissions in the sub-terahertz band have the potential to handle 10 times the data of current wireless systems. This kind of fast transmission would be important for uses such as virtual reality systems or fully autonomous vehicles.

“As our world becomes more connected and data-hungry, the demand for wireless bandwidth is soaring. Sub-terahertz frequencies open the door to far greater speeds and capacity,” Ghasempour said.

Sub-Terahertz beams are easily blocked, but can bend with special transmitters

Ultra-high frequency signals like those in the sub-terahertz band are transmitted in defined beams, unlike lower frequency radio waves, which can span over wider areas. This makes the signals easy to block, particularly indoors and in areas with lots of moving people and objects.

Engineers have successfully tested systems using reflectors to bounce signals around obstacles. But these systems rely on reflectors that may not be available or practical in many situations.

Ghasempour’s team proposed using a special transmission technique to dodge obstacles. The researchers were able to bend transmission beams by transmitting a signal that curves around the obstruction. In doing this, they used an idea first proposed in 1979 for a kind of radio wave called Airy beams that allow engineers to shape transmissions like a curveball. When correctly controlled, the beams can maneuver through a complex and moving field of objects.

“This is for complex indoor scenarios where you don’t have line of sight,” said Haoze Chen, a graduate student at Princeton and the paper’s lead author. “You want the link to adapt to that.”

Unlike static systems, the new system allows the transmitters to adapt to changes in real time. By adjusting the exact curvature properties on the fly, the transmitter can steer signals around new obstacles as they appear, maintaining a strong connection even in crowded, constantly changing environments.

Chen said that most work with Airy beams has focused on creating the beams and exploring their underlying physics.

“What we are doing is not only generating the beams but finding which beams work best in the situation,” he said. “People have shown that these beams can be created, but they have not shown how the beams can be optimized.”

The system learns to dodge obstacles by training like an NBA All-star

Finding the best curved beam is a difficult problem, particularly in a cluttered and shifting environment. The standard method of aiming beams —scanning a room for the best transmission path — does not work for bendable transmissions.

“For Airy beams, this is impractical,” Chen said. “There are infinite ways of curving depending on the degree of the curve and where the curve happens. There is no way a transmitter can scan through.”

To solve the problem, the researchers took a cue from human athletes. Basketball players don’t pull out a calculator every time they take a shot. They rely on past experience to learn what force and direction works for different situations. To generate that type of response, the researchers designed a neural net, a computer system that mimics the brain.

Like basketball players, neural nets require a lot of training before they can perform. But Chen said training the system by transmitting actual beams was very time-consuming. Instead, coauthor Atsutse Kludze designed a simulator that allowed the net to train virtually for different obstacles and different environments. The math behind Airy beams is difficult, and Kludze, a doctoral student in Ghasempour’s lab, had to create a system that applied the underlying physics to almost any scenario.

Neural net calibrates curves with perfect precision

Throwing a lot of data at the neural net is not effective. Instead, the researchers use principles from physics to create and train the neural net. Once the system was trained, the neural net was able to adapt incredibly quickly.

The researchers said they tested their scheme with experiments, which were focused on understanding the technology and developing ways to control the transmissions.

“This work tackles a long-standing problem that has prevented the adoption of such high frequencies in dynamic wireless communications to date,” Ghasempour said. “With further advances, we envision transmitters that can intelligently navigate even the most complex environments, bringing ultra-fast, reliable wireless connectivity to applications that today seem out of reach — from immersive virtual reality to fully autonomous transportation.”

The article, A Physics-Informed Airy Beam Learning Framework for Blockage Avoidance in sub-Terahertz Wireless Network, was published August 18 in the journal Nature Communications. The research was supported in part by the National Science Foundation, the Air Force Office of Scientific Research and the Qualcomm Innovation Fellowship.

The researchers used a specially designed metasurface to direct the transmissions

Credit

Aaron Nathans/Princeton University

Journal

Nature Communications

DOI

10.1038/s41467-025-62443-0

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

A Physics-Informed Airy Beam Learning Framework for Blockage Avoidance in sub-Terahertz Wireless Network

Article Publication Date

18-Aug-2025

Reusable ‘jelly ice’ keeps things cold — without meltwater

American Chemical Society

WASHINGTON, Aug. 18, 2025 — No matter whether it’s crushed or cubed, ice eventually melts into a puddle — but an alternative called jelly ice doesn’t. Researchers Jiahan Zou and Gang Sun developed a one-step process to create the reusable, compostable material from gelatin, the same ingredient in jiggly desserts. Because frozen jelly ice doesn’t leak as it thaws, it’s ideal for food supply chains and medication transport. The team is also exploring protein-based structures for food-safe coatings and lab-grown meat scaffolds.

Zou will present her results at the fall meeting of the American Chemical Society (ACS). ACS Fall 2025 is being held Aug. 17-21; it features about 9,000 presentations on a range of science topics.

The jelly ice project started with a question posed to Zou and Sun by Luxin Wang, a food scientist at the University of California, Davis. Wang saw ice melting in grocery store seafood display cases and worried about meltwater spreading pathogens and contaminating the entire case. She asked whether the researchers could create a reusable material that functions like regular ice but doesn’t produce a potentially contaminated puddle.

The inspiration for the new material came from freezing tofu. Sun, a materials scientist also at UC Davis who advised Zou’s graduate research, explains that “frozen tofu keeps its water inside, but when you thaw it, it releases the water. So, we tried to solve that issue with another material: gelatin.”

Gelatin proteins have two properties that the researchers wanted: They are food safe, and their long strands link together, forming hydrogels with tiny pores that hold water, unlike tofu. Early tests of the hydrogels made with this natural polymer (also called a biopolymer) were a success. The water stayed inside the pores as it went through phase changes, from liquid to ice and back again, without damaging the structures or leaking out the hydrogel.

Through the years, Zou has optimized the gelatin-based hydrogels’ formula and production methods. Now, she has a practical, one-step process to create jelly ice that’s 90% water and can be repeatedly washed with water or diluted bleach, frozen and thawed. The cooling material jiggles and squishes at room temperature. But when cooled below the freezing point of water, 32 degrees Fahrenheit (0 degrees Celsius), it transitions to a firmer, more solid state.

“Compared to regular ice of the same shape and size, jelly ice has up to 80% of the cooling efficiency — the amount of heat the gel can absorb through phase change,” says Zou, who will talk more about this when she presents the newest version of jelly ice at ACS Fall 2025. “And we can reuse the material and maintain the heat absorbance across multiple freeze-thaw cycles, so that’s an advantage compared to regular ice.”

The team can produce jelly ice in 1-pound (0.45-kilogram) slabs, similar to the cold gel packs currently for sale that have bulky plastic sleeves. However, the new cooling material has advantages over cooling packs or dry ice: It’s customizable for any shape or design, and it’s compostable. In one set of experiments, the composted gel improved tomato plant growth when applied to the potting soil. And because the cooling material doesn’t contain synthetic polymers, it shouldn’t generate microplastics.

Zou and Sun say that jelly ice, while initially developed for food preservation applications, shows promise for medical shipping, biotechnology, and use in areas with limited water available for forming ice.

Currently, there are licenses for the jelly ice technology. Zou hopes that this means the cooling material will be available to consumers as a meltwater-free, food contact-safe, compostable alternative to ice. Though, she acknowledges there are still some steps in market analysis, product design and large-scale production tests before it can be commercialized.

But as the gelatin-based jelly ice makes its way toward the market, Zou has also become interested in other natural biopolymers. She expanded her research into plant proteins that are agricultural by-products, such as soy proteins, to make more sustainable materials. Her focus is shifting toward developing soy proteins for removable countertop coatings and cellular scaffolds for cultivated meat. She’ll present more about that work at ACS Fall 2025.

“In my research, I realized how powerful Mother Nature is in designing biopolymers and the vast possibilities they offer,” says Zou. “I believe there will be amazing products derived from biopolymers as the materials themselves are teaching us how to work with them.”

The research was funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture, a Henry A. Jastro Graduate Research Award from UC Davis, and a Food Systems Innovation Award from the Innovation Institute for Food and Health at UC Davis.

A Headline Science YouTube Short about this topic will be posted on Monday, Aug. 18. Visit the ACS Fall 2025 program to learn more about this presentation, “Sustainable bio-derived polymeric materials improving food security, food safety, and circular bioeconomy,” Zou’s additional presentation “Dextrose-conjugated plant-protein 2D scaffolds for improved cultivated meat applications,” and other science presentations.

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The American Chemical Society (ACS) is a nonprofit organization founded in 1876 and chartered by the U.S. Congress. ACS is committed to improving all lives through the transforming power of chemistry. Its mission is to advance scientific knowledge, empower a global community and champion scientific integrity, and its vision is a world built on science. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, e-books and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

To automatically receive press releases from the American Chemical Society, contact newsroom@acs.org.

Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society. ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.

Title
Sustainable bio-derived polymeric materials improving food security, food safety, and circular bioeconomy

Abstract
Functional polymeric materials play a critical role in food systems, supporting processes such as post-harvest handling, processing, shipping, and retail. The development of bio-based sustainable functional materials has become a long-term goal in materials research, driven by growing concerns over global warming and plastic pollution. Agricultural byproducts, rich in biomacromolecules such as proteins and carbohydrates, represent a significant yet underutilized resource, particularly for high-value applications. Motivated by these challenges, this research focused on (1) improving the processability of natural biomacromolecules and (2) exploring their potential applications as functional materials to enhance sustainability, food security, and food safety while advancing the circular bioeconomy. Soy proteins were studied as a model biomacromolecule requiring improved processability, using physical (e.g., ultrasound and high-speed shearing) and chemical (e.g., pH adjustments and plasticizer incorporation) treatments. Synergistic effects from combined approaches demonstrated potential for broader biomacromolecule processing. Three proof-of-concept sustainable materials were developed, showcasing the potential of bio-based functional polymeric materials to benefit food and agricultural systems: 1) a type of novel reusable cooling media (“Jelly Ice Cubes”) designed from gelatin hydrogels, offering customizable cooling, elimination of meltwater, reusability, microbial resistance, and compostability; 2) a removable coating was developed to combat bacterial contamination and prevent biofilm formation on hydrophobic food-contact surfaces; and 3) the scaffolding materials for the future sustainable food developed via cellular agriculture. These innovations highlight the transformative role of bio-based functional materials in addressing critical challenges within food systems by promoting sustainability, reducing waste, and enhancing food security and safety.

Elegant theory predicts the chaos created by bubbles

Scientists uncover classic turbulence in swarms of rising gas swarms

Helmholtz-Zentrum Dresden-Rossendorf

image:
High-speed cameras capture swarms of bubbles rising through an LED-illuminated water column, revealing the chaotic flow patterns of bubble-induced turbulence.
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Credit: B. Schröder/HZDR

A team of international researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Johns Hopkins University and Duke University has discovered that a century-old theory describing turbulence in fluids also applies to a very bubbly problem: how rising bubbles stir the water around them. Their experiments, which tracked individual bubbles and fluid particles in 3D, provide the first direct experimental evidence that so-called ”Kolmogorov scaling“ can emerge in bubble-induced turbulence. The results were published in Physical Review Letters (DOI: 10.1103/v9mh-7pw1).

Bubble-induced turbulence happens in many places: from carbonated drinks to industrial mixing processes to the crashing ocean waves. When enough bubbles rise through a fluid, their wakes stir the surrounding liquid into a complex, turbulent motion. Understanding the rules behind this chaos is essential for improving industrial designs, climate models, and more. Yet, a central question has long puzzled researchers: Can the mathematical theory of turbulence derived by Russian mathematician Andrey Kolmogorov in 1941 – known as ”K41 scaling“ – apply to flows where bubbles drive the motion? Until now, conflicting experimental and computer simulation results made the answer unclear.

”We wanted to get a definitive answer by looking closely at the turbulence between and around bubbles, at very small scales,” says Dr. Tian Ma, lead author of the study and physicist at the Institute of Fluid Dynamics at HZDR. To achieve that, the researchers used advanced 3D simultaneous Lagrangian tracking of both phases – a technique that allows scientists to follow both bubbles and tiny tracer particles in the surrounding water with high precision and in real time. The experimental setup involved an 11.5 cm-wide column of water into which controlled swarms of bubbles were injected from the bottom. Four high-speed cameras recorded the action at 2500 frames per second.

They studied four different cases, varying the bubble size and the amount of gas, to replicate realistic bubbly flows. Importantly, the bubbles with three to five millimeter in diameter were large enough to wobble as they rose, creating strong turbulent wakes. In two of the four cases – those with moderate bubble size and density – the turbulence in the flow closely followed Kolmogorov’s predictions at small scales, that is, for eddies smaller than the size of the bubbles. This marks the first time such scaling has been confirmed experimentally in the midst of a bubble swarm.

Decoding turbulence: energy cascades from big to small

”Kolmogorov's theory is elegant. It predicts how the energy that cascades from big turbulent eddies down to smaller and smaller ones – until it’s eventually dissipated through viscous effects – controls the fluctuations of the turbulent fluid motion,” explains co-author Dr. Andrew Bragg from Duke University. ”Finding that this theory also describes bubble-driven turbulence so well is both surprising and exciting.”

The team also developed a new mathematical formula to estimate the rate at which turbulence loses energy due to viscous effects – known as the energy dissipation rate. Their formula, which only depends on two bubble-related parameters – its size and how densely packed the bubbles are – matched the experimental data remarkably well. Interestingly, they found that Kolmogorov scaling was stronger in regions outside the bubbles' direct wakes. In those wakes, the fluid is so strongly disturbed that the classic turbulent energy cascade is overpowered.

One crucial insight was that for the classic Kolmogorov ”inertial range“ – where his scaling laws work best – to appear clearly in bubble-induced turbulence, the bubbles would need to be significantly larger. But there's a catch: in reality, bubbles of such large sizes would break apart due to their own instability. This means there is a fundamental limit to how well the K41 theory can apply to bubbly flows. ”In a way, nature prevents us from getting perfect Kolmogorov turbulence with bubbles. But under the right conditions, we now know it gets close,” says Dr. Hendrik Hessenkemper, a co-author on the study who performed the experiments.

The findings not only settle an ongoing scientific debate but could also help engineers better design bubble-based systems, from chemical reactors to wastewater treatment. And for physicists, it adds another system – bubbly flows – to the growing list of chaotic phenomena where Kolmogorov’s 1941 theory proves surprisingly robust.

The researchers emphasize that their study is just the beginning. Future work could investigate how turbulence behaves with even more complex bubble shapes, bubble mixtures, or under different gravitational or fluid conditions. ”The more we understand the fundamental rules of turbulence in bubbly flows, the better we can harness them in real-world applications,” summarizes Ma. ”And it’s pretty amazing that a theory from over 80 years ago continues to hold up in such a bubbly environment.”

Publication:
T. Ma, S. Tan, R. Ni, H. Hessenkemper, A. D. Bragg, Kolmogorov scaling in bubble-induced turbulence, in Physical Review Letters, 2025 (DOI: 10.1103/v9mh-7pw1).

Further information:
Dr. Tian Ma | Head of HZDR junior research group "Bubbles go with turbulent flows"
Institute of Fluid Dynamics at HZDR
Phone: +49 351 260 3805 | Email: tian.ma@hzdr.de

Media contact:
Simon Schmitt | Head
Communications and Media Relations at HZDR
Phone: +49 351 260 3400 | Mob.: +49 175 874 2865 | Email: s.schmitt@hzdr.de

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs – as an independent German research center – research in the fields of energy, health, and matter. We focus on answering the following questions:

How can energy and resources be utilized in an efficient, safe, and sustainable way?
How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
How do matter and materials behave under the influence of strong fields and in smallest dimensions?

To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the Dresden High Magnetic Field Laboratory and the ELBE Center for High-Power Radiation Sources.
HZDR is a member of the Helmholtz Association and has six sites (Dresden, Freiberg, Görlitz, Grenoble, Leipzig, Schenefeld near Hamburg) with almost 1,500 members of staff, of whom about 680 are scientists, including 200 Ph.D. candidates.

High-speed cameras capture swarms of bubbles rising through an LED-illuminated water column, revealing the chaotic flow patterns of bubble-induced turbulence.