Two-color glowing molecule could make wind tunnel tests more accurate

University of Manchester

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A two colour glowing molecule which can sense both pressure and temperature

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Credit: The University of Manchester

Key findings

• Researchers have developed a single molecule capable of measuring both air pressure and temperature at the same time, overcoming a longstanding challenge in sensor technology.
• By emitting two different light signals, one affected by both pressure and temperature and another affected only by temperature, the molecule can automatically correct for temperature effects and provide more accurate pressure readings.
• Designed for use in specialist sensor paints, the breakthrough could help engineers capture more reliable pressure measurements from aircraft models in wind tunnels, even when temperatures fluctuate.

 

Most sensors can only measure one thing at a time: like a thermometer for temperature, or a pressure gauge for pressure. Measuring two properties accurately from the same surface, at the same moment, usually means using two separate instruments – adding cost and complexity to the process.

Now, chemists and aerospace engineers at The University of Manchester, working with colleagues at the University of Eastern Finland, have designed a molecule that can help us to do both simultaneously. It emits two distinct colours of light at once: one that responds to both air pressure and temperature, and one that only responds to temperature. By comparing these two signals it’s possible to take a corrected pressure reading from the molecule itself, rather than having to use a separate temperature sensor alongside a pressure sensor.

The molecule has been designed to be an active ingredient in the specialist paints that measure pressure on aircraft models in wind tunnels, solving a major challenge in the aerospace industry. When engineers test a new aircraft design in a wind tunnel, they need to know exactly how air pressure is distributed across every surface. One of the best ways of doing this is by using a pressure-sensitive paint that glows in proportion to the air pressure pushing against it. The problem is that the light these paints currently emit is sensitive not only to pressure, but also to temperature. As a scale model heats and cools during a wind tunnel test, the glowing shifts in ways that have nothing to do with pressure, introducing errors that engineers then have to correct.

Dr Alexander Romanov, Senior Research Fellow in the Department of Chemistry, The University of Manchester, said: “Our new Manchester material emits red light, what we call phosphorescence, which is sensitive to changes in both pressure and temperature. At the very same time, this material emits blue light as a fluorescence – responding only to temperature. By measuring blue and red light at once, we’ve got everything we need to separate the pressure signal from the temperature interference. That kind of built-in self-correction is simply not possible with a standard light-emitting molecule.”

The team’s work, published in the journal Advanced Optical Materials, explains how the molecule is built around a gold atom bonded to a ring-shaped compound called acridine. The position of that bond within the structure determines which type of light the molecule produces. Gold was chosen because even subtle changes to where it sits within the molecule produce reliably different light-emitting behaviours, giving chemists precise control over the sensing properties. When the gold atom bonds to one position on the molecule, it triggers the pressure-sensitive red emission, whereas a bond at a different position triggers the temperature-only blue emission.

Calculations carried out by their colleagues in Finland, helped the team to understand and predict these differences before the molecule was built in the laboratory. Then in use, the molecule is embedded in a paint applied to test models in the standard way. A camera captures both emission colours simultaneously, and the ratio between the two signals automatically corrects for temperature, without any separate temperature sensor.

Dr Mark Quinn, Reader in the Department of Mechanical and Aerospace Engineering at The University of Manchester, said: “In wind tunnel testing, temperature correction is currently one of the main challenges to making pressure-sensitive paints reliable. Having both pressure and temperature measurements come from the same molecule simultaneously is a more elegant solution, and potentially a more practical one for real test conditions, where adding extra instruments creates its own complications.”

The team’s work sits within a broader programme of research at Manchester into improving pressure-sensitive paint for aerospace applications. A related study, recently published in ACS Applied Engineering Materials, addresses the temperature problem from a different direction, by designing a platinum-based paint with inherently low temperature sensitivity. Together, the two studies represent complementary approaches to one of the industry’s most persistent challenges.
 

This research has been published in the journal Advanced Optical Materials.

Full title: Temperature Correction in a Single Luminophore Pressure-Sensitive Paint Using a Dual-Emitting Gold Acridine Complex

DOI: 10.1002/adom.71493

URL: https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.71493?af=R

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Journal

Advanced Optical Materials

DOI

10.1002/adom.71493

Article Title

Temperature Correction in a Single Luminophore Pressure-Sensitive Paint Using a Dual-Emitting Gold Acridine Complex

Glowing paint that maps air pressure could improve the design of future aircraft

University of Manchester

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Aerodynamic performance data on a truncated cone model at supersonic flow collected using low temperature sensitivity PSP.

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Credit: The University of Manchester

Key findings

• Scientists have developed a new pressure-sensitive paint that delivers more accurate pressure measurements by minimising the effects of temperature fluctuations.
• The material combines a platinum-based light-emitting compound with a specially engineered polymer, allowing it to respond more reliably during wind tunnel testing.
• Trials showed a 25% reduction in temperature sensitivity compared with the current industry standard.
• The improvement comes from chemically locking the active molecules into the polymer structure, preventing molecular clustering that can distort measurements.
• The advance could help aerospace engineers make better-informed design decisions using cleaner aerodynamic data.

When engineers design a new aircraft, they need to know exactly how air flows over every surface. The pressure distribution must be controlled or the fuel efficiency, handing, or even structural safety can be affected.

A promising new technique for measuring this is by applying a special paint to scale models tested in wind tunnels, which glows in proportion to the air pressure pushing against it. However, these paints have one main flaw – they’re sensitive to temperature as well as pressure. As a model heats up during testing, the paint output can shift and introduce errors that engineers then have to unpick.

Now, a team from The University of Manchester’s Departments of Mechanical and Aerospace Engineering, and Chemistry, have created a paint that substantially reduces the problem. This new material uses a light-emitting, platinum-based compound, locked into a specially engineered plastic. The results of trials using the paint, published in ACS Applied Engineering Materials, show a drop in temperature sensitivity to just 0.3% per degree Celsius – 25% less than the current industry benchmark.  

Dr Elliott Nunn, first author based in the Department of Chemistry, The University of Manchester, said: “When you’re testing a vehicle at high speed it can heat and cool dramatically based on its aerodynamic design. By creating a pressure-sensitive paint which doesn’t respond as strongly to this heat, we’ve got something that’s much closer to measuring exactly what we want to measure. Our hope is that this will really help the engineers designing the next generation of high-performance and more sustainable aircraft and spacecraft, to make better-informed decisions through cleaner data.”

Their breakthrough comes down to how the active ingredient sits within the material. In many existing paints, the molecules responsible for glowing can cluster together, and this clustering makes the paint more sensitive to heat. The Manchester team fixed this by anchoring this ingredient, from the same family of molecules that give blood its red colour, or make leaves green, directly into a tough, Teflon-like plastic. When held in place at the chemical level, the molecules are far less likely to cluster and the paint’s temperature sensitivity drops.

Dr Louise Natrajan, Reader in the Inorganic Chemistry Group, The University of Manchester, said: “Getting this chemistry right was thanks to a creative collaboration between our chemistry group and the aerospace engineering team – basically, they knew what the paint needed to do in a wind tunnel, and we knew how to create something that could do it.”

To test their paint under realistic conditions, the team applied it to a cone-shaped model designed to produce complex airflows, then ran this model through a supersonic wind tunnel where airflows can exceed Mach 5 – 5x the speed of sound. At these conditions the model’s temperature varies drastically across its surface. However, the new paint measured pressure accurately throughout the test, with results aligning closely with the values predicted by computer simulations.

This paint was also able to help the researchers visualise the corkscrew-shaped swirls of air that develop along concave curved surfaces – known as Görtler vortices – which are important for understanding how the thin layer of air next to a surface behaves at speed.

More accurate pressure measurements at high speeds and temperatures, could translate directly into helping the aerospace industry to develop safer, more efficient transport. The team are now planning to test their paint across a wider range of conditions, to build confidence in how reliably it can perform.
 

This research has been published in the journal ACS Applied Engineering Materials

Full title: Low-Temperature Dependency Pressure-Sensitive Paints for Wind Tunnel Testing Based on Luminescent Polymer-Bound Porphyrins

DOI: 10.1021/acsaenm.6c00751

URL: https://doi.org/10.1021/acsaenm.6c00751

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Journal

ACS Applied Engineering Materials

DOI

10.1021/acsaenm.6c00751

Article Title

Low-Temperature Dependency Pressure-Sensitive Paints for Wind Tunnel Testing Based on Luminescent Polymer-Bound Porphyrins

 

Pressurized experiments could help wind farms generate more power

A new way of simulating wind turbines in the field shows how tweaking turbine operation could unlock tens of thousands of dollars per turbine every year

Massachusetts Institute of Technology

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• 
  

• By pressurizing wind tunnels, researchers were able to simulate field conditions at wind farms and identify ways to get more power from existing wind farms.
• With this approach, the researchers determined how the alignment of the turbine and its tip speed relative to the wind influence the power it generates, offering new insights into how to increase power generation at existing wind farms.
• The researchers estimate that optimizing the turbine alignment relative to wind, the blade pitch angles, which control the airfoil’s angle of attack, and the tip speed relative to the wind could potentially result in tens of thousands of dollars per turbine every year in additional revenue.

https://news.mit.edu/2026/pressurized-experiments-could-help-wind-farms-generate-more-power-0928

Cambridge, Mass. -- The world needs more wind energy. But anyone designing new wind turbines or trying to squeeze more power out of existing ones faces a stiff challenge testing new approaches. That’s because the atmosphere is a tough place for a controlled experiment.

Some researchers use wind tunnels to conduct tests, but scaled-down wind turbines in traditional wind tunnels can differ widely from conditions in the field. (Wind turbines are the largest rotating machines ever made.) The problem hampers not only development of better wind turbines, but also our understanding of basic questions like how much power to expect from a turbine when winds change direction.

In a new open access paper published in PNAS Nexus, researchers closed the gap between experiments in the field and the lab by using a wind tunnel that features high pressurization to simulate the flow physics in the atmosphere. With this approach, the researchers determined how the alignment of the turbine and its tip speed relative to the wind influence the power it generates, offering new insights into how to get more power from existing wind farms.

They also used the approach to validate a computationally lightweight model that engineers can use to test different turbine designs and wind farm control strategies.

Together, the researchers estimate that optimizing the turbine alignment relative to wind, the blade pitch angles, which control the airfoil’s angle of attack, and the tip speed relative to the wind could potentially result in tens of thousands of dollars per turbine every year in additional revenue.

“The immediate impact of this study is that we’ve now both improved and validated models that go into wind turbine control protocols for existing farms,” says Michael Howland, MIT’s Jeffrey Cheah Career Development Professor. “The bigger, medium-term impact, with a much larger upside, is this new experimental paradigm to rapidly prototype, validate simulation models, and test hypotheses about better designs and control strategies much faster than has been possible before.”

Joining Howland on the paper are first author John Kurelek, an assistant professor at Queen’s University; MIT PhD candidates Ilan Upfal and Kirby Heck; Queen’s University postdoc Supun Pieris; Penn State University researcher Alexander Piqué; and Princeton University Professor Marcus Hultmark.

Answers in the wind

Howland has spent years developing models to simulate wind farm performance and developing new techniques to increase their power output. In 2022, he showed that accounting for the wake of individual turbines when controlling the entire wind farm could significantly increase power output.

But that work required his research team to first conduct a lengthy field experiment that temporarily resulted in lowering a real wind farm’s power output by intentionally misaligning turbines from the wind for months to better understand their performance in misalignment.

“Wind energy is a uniquely challenging problem to study experimentally,” Howland says. “We want to test the effect of a certain change in isolation, but wind farms operate in chaotic, turbulent environments where the weather is constantly evolving. Wind turbines have to react to weather conditions that we have no control over, and that introduces complexities in identifying the impact of the imposed change we are studying. The field sits at this unique intersection between environmental flow, mechanics, aerodynamics, and meteorology.”

The difficulty of running experiments at real wind farms has left researchers and engineers unsure of how changes in the alignment between the wind and turbine or factors like the turbine’s tip speed relative to the wind change power output.

In fact, the researchers say many predictive models people use are built on the assumption that turbines are always perfectly perpendicular to the wind. That’s rarely the case in the real world, even with modern turbines that gradually adjust their angle in response to the wind’s rapid directional changes.

“People have been debating which models are best for understanding the output from these wind farms, but if you have nothing to compare them against, it’s very difficult to advance the field,” Hultmark says. “This paper tries to do both of those things.”

Hultmark’s research lab at Princeton has pioneered the study of scaled-down wind turbines in pressurized wind tunnels, which, as previous studies have shown, better reproduce large-scale turbines in the atmosphere because pressure makes air more dense, resulting in more inertia within the scaled laboratory environment. For the new study, the researchers used a turbine measuring 15 centimeters in diameter at varying pressures of up to 240 atmospheres.

“By pressurizing the chamber, we’re testing a turbine that is, all else being equal, 15 to 20 meters in diameter, with the ability to go up to 35 meters in diameter,” lead-author Kurelek explains. “That’s because we’re increasing the density by a factor of 100 to 220 times,” 

Kurelek sent the dimensions of the wind tunnel and wind turbine setup to Howland, who used them to calculate the aerodynamics, forces, and power production using a newly developed unified wind turbine model, which builds on previous work that developed a more general aerodynamic theory for wind turbines. The new model enables the researchers to simulate wind turbine performance across operating conditions without relying on empirical corrections that have historically been used in wind power models.

The researchers then ran a series of experiments in the tunnel over the course of several weeks, testing the turbine’s performance at different wind alignments and with different control strategies, to isolate how each factor affects performance.

They found power output could be significantly increased by adjusting the turbine’s tip speed based on its misalignment angle with the wind — a control strategy that is rarely employed in wind farms today but could offer a way to boost performance with minimal added costs.

“The big output of the experiments was clearly showing that new power maximums can be achieved when the turbine becomes misaligned with the wind through only changes to the tip speed,” Kurelek says.

Scaling the approach

The study served as validation for Howland’s model, which is fast enough to be run by engineers designing and operating wind turbines around the world using regular laptop computers.

“What we really want to know is if the turbines are always operating in some degree of misalignment with the wind, how should we control the turbine to get the maximum achievable power production?” Howland explains. “Our unified momentum model was able to make predictions of how to do this control a few years ago, and this is the first time we’e able to experimentally validate that model.”

Howland says validating models is only one part of the paper’s potential impact.

“This study also shows the huge opportunity to perform these high-throughput, controlled experiments in the pressurized facilities that Marcus and John work with, enabling us to achieve the right physics but in a time efficient and low-cost manner,” Howland says. “Right now, there's a massive gap between idealized theoretical and simulation models and full-scale testing in extremely complicated field environments. Nothing is filling that gap except for these pressurized experiments. I hope this can be an enabler to investigate a huge range of unanswered wind energy questions in controlled environments.”

The work was supported in part by the Natural Sciences and Engineering Research Council of Canada; the National Science Foundation; and the MIT-GE Vernova Alliance.

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Written by Zach Winn, MIT News

Paper: “Full dynamic similarity experiments and predictive modeling of wind turbine aerodynamics across control strategies”
https://academic.oup.com/pnasnexus/advance-article/doi/10.1093/pnasnexus/pgag303/8786541

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Journal

PNAS Nexus

DOI

10.1093/pnasnexus/pgag303

Article Title

“Full dynamic similarity experiments and predictive modeling of wind turbine aerodynamics across control strategies”

 

University of Central Florida researcher discovers experimental evidence of new type of magnetism

Professor Madhab Neupane and collaborators have demonstrated experimental evidence of altermagnetism in a layered material, opening a promising pathway toward future quantum and spintronic technologies

University of Central Florida

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From left, UCF Professor Madhab Neupane, doctoral candidates Milo Sprague, Arun K. Kumay, and Mazharul Islam Mondal conducted research on altermagnetic materials. Their work is helping reveal new electronic properties that could advance future technologies. 

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Credit: Antoine Hart/ UCF

To build the ultrafast computers of the future, scientists are looking beyond the electrical charge of electrons to another property: their spin. While conventional hardware relies entirely on the movement of charge to process data, the ability to tap into this intrinsic quantum property could enable researchers to completely reinvent how information travels through a circuit.

Now, a team led by UCF Professor of Physics Madhab Neupane has identified a promising candidate. Neupane and his collaborators found evidence of altermagnetism, an emerging form of magnetism that combines useful characteristics of the two more familiar types of magnetism: ferromagnetism and antiferromagnetism.

Ferromagnetism produces the behavior most people associate with everyday magnets. In these materials, magnetic moments align in the same direction, creating a magnetic field. That property can be useful in electronics, but the resulting stray magnetic fields can interfere with nearby components.

Antiferromagnets behave differently. Their magnetic moments point in opposing directions and cancel one another out, largely avoiding the stray fields. However, they lack some of the useful electronic properties found in ferromagnets.

Altermagnets offer another possibility by combining desirable characteristics of both.

Like antiferromagnets, they can avoid producing unwanted stray magnetic fields. But they can also generate and detect spin currents — the movement of electron spins through a material — that researchers hope to use for future electronics.

Neupane and his collaborators experimentally identified signatures of this unusual magnetic state in Co₁/₄TaSe₂, a layered material containing magnetic cobalt atoms. The discovery gives researchers a promising, versatile platform for studying altermagnetism and could help advance future electronic and spintronic technologies.

“These materials are distinguished from more conventional antiferromagnets by their ability to generate and detect spin currents without the negative effect of producing stray fields,” Neupane says. “This new property makes them very well positioned for use in many different applications — including spintronics, ultrafast memory devices, terahertz networks and energy-efficient electronics.”

Tracking the Signs of Altermagnetism

To determine whether Co₁/₄TaSe₂ exhibited altermagnetism, the researchers needed to examine how its electrons behaved.

They used a technique called angle-resolved photoemission spectroscopy, or ARPES, which allows scientists to measure the energy and movement of electrons and map a material’s electronic structure.

Our approach was to use higher-resolution methods that were insensitive to the electron’s spin to measure the splitting in the energy levels,” Neupane says. “Then, we complemented this measurement with spin-resolved ARPES to conclusively tell if this looks like altermagnetism.”

The team first detected a characteristic splitting in the material’s electronic bands. They then used spin-resolved ARPES to take a closer look and found that those split states carried opposite spin polarizations, key evidence of altermagnetism.

Getting a clear look at that behavior presented another challenge. Photoemission measurements are extremely sensitive to a material’s surface, so researchers needed exceptionally clean samples to accurately observe what was happening.

While collaborators produced high-quality Co₁/₄TaSe₂ samples, Neupane’s team carefully screened them for ultra-clean surfaces before mapping the material’s electronic behavior.

“The significance became clear once the experimental measurements consistently matched our theoretical predictions,” Neupane says. “Seeing those independent pieces of evidence converge gave us confidence that we had identified a genuine layered altermagnet.”

Why Layered Materials Are Changing the Game

Finding evidence of altermagnetism was only part of what made Co₁/₄TaSe₂ interesting to researchers.

The material is built from extremely thin layers stacked on top of one another. Because those layers are weakly bound, scientists can separate and combine them into extremely thin structures, making layered materials promising for use in thin-film devices and other emerging technologies.

Scientists call this family of layered materials transition-metal dichalcogenides, or TMDs.

In Co₁/₄TaSe₂, magnetic cobalt atoms inserted between the layers help create the material’s unusual magnetic properties. Its layered structure also makes the material highly tunable, allowing researchers to modify it and study how those changes affect its electronic and magnetic behavior.

The team also wanted to understand where that unusual electronic behavior originated. Before the study, it was unclear whether the key signatures of altermagnetism in layered materials would come primarily from the surface or from deeper within the material.

Their measurements showed that the relevant electronic state originated primarily within the material itself and displayed clear signatures of altermagnetic order.

“Evidence for altermagnetism in a versatile materials platform opens a lot of new possibilities,” says Milo Sprague, the study’s lead graduate student researcher. “There’s currently a lot of debate in altermagnetic theory about how the spin-polarized electronic states interact with other magnetic phenomena. Now we have a material that we can easily modify to explore these new questions.”

Building the Foundation for Future Technologies

Most conventional electronics rely on the electrical charge of electrons to transmit and process information. But electrons possess another property, their spin, that researchers are exploring as another way to carry information.

This emerging field is known as spintronics.

Altermagnets could be particularly useful for spintronics because they can generate and detect spin currents without producing the stray magnetic fields that can interfere with densely packed electronic components.

“As electronic devices continue to shrink, researchers need new materials that can operate faster while consuming less energy,” Neupane says.

Layered materials are already being investigated for use in extremely small transistors, optical technologies and other electronic devices. At the same time, researchers are exploring whether spin currents can provide new ways to transmit digital information.

Layered altermagnets could bring those two areas of research together, providing extremely thin, adaptable materials capable of controlling electron spin without producing the same unwanted magnetic interference as conventional magnets.

“If this approach proves viable, then layered altermagnets will be at the forefront of electronics development,” Neupane says.

What Researchers Still Don’t Know

The study gives researchers something particularly valuable: a material they can use to investigate the many unanswered questions surrounding altermagnetism in Co₁/₄TaSe₂.

Scientists still don’t fully understand why this unusual magnetic state forms or why it can become favored over other possible magnetic structures — including ferromagnetism and other forms of antiferromagnetism — and how it behaves.

Theoretical studies suggest that competition among different interactions between electrons may help determine which magnetic state forms, but researchers are still working to determine how completely those theories describe the behavior of real materials.

“There are many details to the theory of how altermagnets work that haven’t been explored or verified yet,” Neupane says. “Now that we have identified several platforms for answering these questions, more advanced studies into these materials are underway.”

Because scientists can modify Co₁/₄TaSe₂ and observe how its properties change, the material provides researchers with a new experimental platform for investigating unanswered questions and exploring how altermagnetism interacts with other magnetic and electronic phenomena.

 

This material is based upon work supported by the U.S. Department of Energy, Office of Science under Award Number DE-SC0024304.

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Journal

Nature Communications

DOI

10.1038/s41467-026-76784-x

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Observation of Altermagnetic Spin-Splitting in an Intercalated Transition Metal Dichalcogenide

Madhab Neupane’s UCF lab includes molecular beam epitaxy (MBE), angle-resolved photoemission spectroscopy (ARPES) and time-resolved ARPES systems. The Neupane group also conducts measurements at national synchrotron facilities. Measurements for this project were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory and the Stanford Synchrotron Radiation Lightsource.

Credit

Madhab Neupane