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Expert sommeliers can take a whiff of a glass of wine and tell you a lot about what’s in your pinot noir or cabernet sauvignon.

A team of physicists at CU Boulder and the (NIST) have achieved a similar feat of sensing, only for a much wider range of substances.

The group has developed a new laser-based device that can take any sample of gas and identify a huge variety of the molecules within it. It is sensitive enough to detect those molecules at minute concentrations all the way down to parts per trillion. Its design is also simple enough that researchers could employ the method quickly and at a low cost in a range of settings, from diagnosing illnesses in human patients to tracking greenhouse gas emissions from factories.

The study was led by scientists at between CU Boulder and NIST. The team in the journal Nature.

“Even today I still find it unbelievable that the most capable sensing tool can in fact be built with such simplicity, using only mature technical ingredients but tied together with a clever computation algorithm,” said Qizhong Liang, lead author of the research and a doctoral student at JILA.

To show what the tool is capable of, Liang and his colleagues drilled down on an important question in medicine: What’s in the air you breathe out?

The researchers analyzed breath samples from real human subjects and showed that they could, for example, identify the types of bacteria living in peoples’ mouths. The technique could one day help doctors diagnose lung cancer, diabetes, chronic obstructive pulmonary disease (COPD) and much more.

Physicist Jun Ye, senior author of the study, said the new work builds on nearly three decades of research into quantum physics at CU Boulder and NIST—especially around a type of specialized device known as a frequency comb laser.

“The Frequency comb laser was originally invented for optical atomic clocks, but very early on, we identified its powerful application for molecular sensing,” said Ye, a fellow of JILA and NIST and professor adjoint of physics at CU Boulder. “Still, it took us 20 years to mature this technique, finally allowing universal applicability for molecular sensing.”

A shaking cavity

To understand how the team’s technology works, it helps to understand that all gases, from pure carbon dioxide to your stinky breath after you eat garlic, carry a fingerprint of sorts.

If you probe those gases with a laser that spans multiple “optical frequencies,” or colors, the molecules in the gas samples will absorb that light at different frequencies. It’s almost like a burglar leaving behind a thumbprint at a crime scene. In a previous study, for example, Liang and his colleagues used this laser absorption detection principle to screen human breath samples for signs of SARS-CoV-2 infections.

Frequency combs are well suited to that technique because, unlike traditional lasers, they emit pulses of light in thousands to millions of colors at the same time. (JILA’s Jan Hall pioneered these lasers, winning the for his work in 2005).

But to detect molecules at low concentrations, those lasers must also pass through the gas sample over distances of miles or more so that the molecules can absorb enough light.

To be practical, scientists must realize that distance within containers for gases that are measured on the scale of a foot.

“We enclose the gas sample with a pair of high-reflectivity mirrors, forming an ‘optical cavity,’” Liang said. “The comb light can now bounce between those mirrors several thousand times to effectively increase its absorption path length with the molecules.”

Or that’s the goal. In practice, optical cavities are tricky to work with and eject laser beams if they aren’t properly matched to the resonant modes of the cavity. As a result, scientists previously could only use a narrow range of comb light, and detect a narrow range of molecules, in a single test.

In previous research, Ye, Liang and their colleagues used specialized lasers to detect signs of COVID-19 infections in human breath. (Credit: NIST)

In the new study, Liang and his colleagues overcame this longstanding challenge. They presented a new technique they named Modulated Ringdown Comb Interferometry, or MRCI (pronounced “mercy”). Rather than keep its optical cavity steady, the team periodically changed its size. This jiggling, in turn, allowed the cavity to accept a much wider spectrum of light. The team then deciphered the complicated laser intensity patterns emerging from the cavity with computational algorithms to determine the samples’ chemical contents.

“We can now use mirrors with even larger reflectivity and send in comb light with even broader spectral coverage,” Liang said. “But this is just the beginning. Even better sensing performance can be established using MRCI.”

A sensor for breath

The team is now turning its new gas sniffer on human breath.

“Exhaled breath is one of the most challenging gas samples to be measured, but characterizing its molecular compositions is highly important for its powerful potential for medical diagnostics,” said Apoorva Bisht, co-author of the research and a doctoral student in Ye’s lab.

Bisht, Liang and Ye are now collaborating with researchers at CU Anschutz Medical Campus and Children’s Hospital babyֱ��app to use MRCI to analyze a range of breath samples. They are examining whether MRCI can distinguish samples taken from children with pneumonia from those taken from children with asthma. The group is also analyzing the breath of lung cancer patients before and after tumor removal surgery and is exploring whether the technology can diagnose people in early stages of chronic obstructive pulmonary disease (COPD).

“It will be tremendously important to validate our approach on real world human subjects,” Ye said. “Through close collaboration with our medical colleagues at CU Anschutz, we are committed to developing the full potential of this technique for medical diagnosis.”

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In CUriosity, experts across the CU Boulder campus answer pressing questions about humans, our planet and the universe beyond.

Previously, astrophysicist Jeremy Darling tackled: “What is the biggest thing in the universe?” This week, Ethan Neil, associate professor in the Department of Physics, answers: “What is the smallest thing in the universe?”

As with everything in physics, the answer may melt your brain—just a little. It also hinges on how you define “small,” said Ethan Neil, a theoretical physicist who studies incredibly small things.

Does smallest mean, for example, the object with the least mass? Or is it more about size, how much space an object takes up?

  Previously in CUriosity

What is the biggest thing in the universe?

Or read more CUriosity stories here

As Neil put it: “The question is more complicated than it seems on the surface, partly just due to the weirdness of quantum physics. The world is unintuitive when we get to very short distance scales.”

Let’s start with mass. Neil explained that the universe, at least as we know it, is made up of elementary particles like electrons and quarks, small things that can’t be broken down into even smaller stuff. Think of them as the basic ingredients for making everything in the cosmos.

Physicists capture the family tree of these particles in a theory that dates back to the 1960s known as the Standard Model. Within that tree, the electron is superbly petite. Writing out its mass in kilograms, you’d get 0.000000000000000000000000000000911 (that’s 30 zeros). Another elementary particle, the electron neutrino, has an even smaller mass—although no one knows exactly how small. The sun ejects neutrinos constantly and, at this moment, trillions are moving through your body.

The question of size, however, is where things really get weird.

“In the Standard Model, things like the electron don’t have any size,” Neil said.

In other words, you could zoom in and in on them and never see anything. But how sure are scientists that electrons are truly infinitely small?

Using facilities like the at CERN in Switzerland, scientists have probed the universe down to really small scales. So far, they’ve been able to observe the universe down to about 20 zeptometers.

Or, as Neil put it: “If a single atom was the size of a human being, 20 zeptometers would be the size of an atom.”

If an electron has size, it has to be smaller than that. But theoretical physicists like Neil have also thought about what could exist at even smaller scales. That includes at the Planck length, a distance that, in meters, would take a decimal point followed by 34 zeros to write out.

At that scale, Neil explained, the inherent randomness and uncertainty of the universe dominates so much that concepts like size and distance become more or less meaningless. In fact, physicist John Baez predicted that if you tried to measure something that small, you’d concentrate enough energy to form a black hole.

That doesn’t, however, mean that there’s nothing there. One popular theory suggests that the elementary particles themselves are made up of vibrating strings that are about the size of the Planck length—meaning that everything you know could be the product of a concerto played by an orchestra of impossibly tiny violins. 

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A team of physicists and engineers at the CU Boulder has discovered a new way to measure the orientation of magnetic fields using what may be the tiniest compasses around—atoms. 

The group’s findings could one day lead to a host of new quantum sensors, from devices that map out the activity of the human brain to others that could help airplanes navigate the globe. The new study, , stems from a collaboration between physicist Cindy Regal and quantum engineer Svenja Knappe.

It reveals the versatility of atoms trapped as vapors, said Regal, professor of physics and fellow at between CU Boulder and the National Institute of Standards and Technology (NIST).

“Atoms can tell you a lot,” she said. “We’re data mining them to glean simultaneously whether magnetic fields are changing by extremely small amounts and what direction those fields point.” 

These fields are all around us, even if you never see them. Earth’s iron-rich core, for example, generates a powerful magnetic field that surrounds the planet. Your own brain also emits tiny pulses of magnetic energy every time a neuron fires.

But measuring what direction those fields are pointing, for precise atomic sensors in particular, can get tricky. In the current study, Regal and her colleagues set out to do just that—with the aid of a small chamber containing about a hundred billion rubidium atoms in vapor form. The researchers hit the chamber with a magnetic field, causing the atoms inside to experience shifts in energy. They then used a laser to precisely measure those shifts.

“You can think of each atom as a compass needle,” said Dawson Hewatt, a graduate student in Regal’s lab at JILA. “And we have a billion compass needles, which could make for really precise measurement devices.”

Magnetic world

The research emerges, in part, from Knappe’s long-running goal to explore the magnetic environment surrounding us.

“What magnetic imaging allows us to do is measure sources that are buried in dense and optically opaque structures,” said Knappe, research professor in the Paul M. Rady Department of Mechanical Engineering. “They’re underwater. They’re buried under concrete. They’re inside your head, behind your skull.”

In 2017, for example, Knappe co-founded the company that manufactures atomic vapor magnetic sensors, also called optically pumped magnetometers (OPMs). The company builds integrated sensors the size of a sugar cube and fits them into helmets that can map out the activity of human brains.

These OPMs also have a major limitation: They only perform well enough to measure minute changes in magnetic fields in environments shielded from outside magnetic forces. A different set of OPMs can be used outside these rooms, but they are only adept at measuring how strong magnetic fields are. They can’t, on their own, record what direction those fields are pointing. That’s important information for understanding changes brains may undergo due to various neurological conditions.

To extract that kind of information, engineers typically calibrate their sensors using reference magnetic fields, which have a known direction, as guides of a sort. They compare data from sensors with and without the reference magnetic fields applied to gauge how those sensors are responding. In most cases, those references are small metal coils, which, Knappe said, can warp or degrade over time.

Regal and her team had a different idea: They would use a microwave antenna as a reference, which would allow them to rely on the behavior of atoms themselves to correct for any changes of the reference over time.

Study co-authors included Christopher Kiehl, a former graduate student at JILA; Tobias Thiele, a former postdoctoral researcher at JILA; and Thanmay Menon, a graduate student at JILA.

Atoms guide the way

Regal explained that atoms behave a bit like tiny magnets. If you zap one of the team’s atoms with a microwave signal, its internal structure will wiggle—a sort of atomic dance that can tell physicists a lot.

“Ultimately, we can read out those wiggles, which tell us about the strength of the energy transitions the atoms are undergoing, which then tells us about the direction of the magnetic field,” Regal said. 

In the current study, the team was able to use that atomic dancing to pinpoint the orientation of a magnetic field to an accuracy of nearly one-hundredth of a degree. Some other kinds of sensors can also reach this level with careful calibration, but the researchers see atoms as having significant potential with further development.  

Unlike mechanical devices with internal parts that can morph, “atoms are always the same,” Regal said.

The team still has to improve the precision of its tiny compasses before bringing them out into the real world. But the researchers hope that, one day, airplane pilots could use atoms to fly around the globe, following local changes in Earth’s magnetic field, much like migratory birds using their own biological magnetic sensors.

“It’s now a question of: ‘How far can we push these atomic systems?’” Knappe said.

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  Beyond the Story

Our research impact by the numbers:

• 45 U.S. patents issued for CU inventions through Venture Partners in 2023–24
• 35 startups launched based on university innovations in 2023–24
• $1.2 billion raised by companies built on CU Boulder innovations in 2022–24

When it comes to putting science into action, last year was one for the 

record books. From July 2023 to June 2024, CU Boulder helped to launch 35 new companies based on research at the university—a big tick up from the previous record of 20 companies in fiscal year 2021.

The new businesses are embracing technologies from the worlds of healthcare, agriculture, clean energy and more—including sensors that could one day help farmers improve their crop yields and breathalyzers that can detect signs of infection in the air you breathe out.

Here’s a look at how scientists, with the help of the university’s commercialization arm Venture Partners at CU Boulder, seek to use discoveries from the lab to make a difference in peoples’ lives.

Mana Battery: Cheaper, longer lasting batteries for clean energy

This company is set to spark a renewable energy revolution. Founded by Chunmei Ban, associate professor in the Paul M. Rady Department of Mechanical Engineering, along with CU alumni Nick Singstock and Tyler Evans, Mana Battery is developing a cheaper, safer and longer lasting alternative to the traditional lithium-ion battery.

Lithium-ion batteries are the most common type of rechargeable battery on the planet, powering everything from TV remotes to cell phones and even electric vehicles. But the materials used in these batteries, such as lithium and cobalt, are rare and expensive. In contrast, Mana’s batteries run on sodium, an abundant mineral, offering a more affordable and sustainable alternative.

Currently, sodium-ion batteries come with a host of technological challenges. For example, they typically store less energy than lithium-ion batteries of the same size. 

Ban and her team are working on improving sodium-ion battery designs to increase the amount of energy they can store. Their goal is to develop sodium-ion batteries with the same energy density as lithium-ion batteries at just 35% to 75% of the cost. 

The renewable energy industry could reap the benefits. Sodium-ion batteries could store excess clean energy generated by solar panels or wind turbines, providing power even during cloudy or windless days.  

“The use of batteries has significantly supported, and will continue to promote, the widespread use of electric vehicles and low-cost energy storage solutions for the power grid,” Ban said. 

Flari Tech: Laser-based nose to sniff out disease

Imagine a day when, instead of giving blood, saliva or other bodily fluids, you simply exhaled to get a read on what was happening with your health.

That’s the idea behind a new laser-based technology designed to harness human breath for faster, cheaper and less invasive medical diagnostics.

“There is a real, foreseeable future in which you could go to the doctor and have your breath measured along with your height and weight. … Or you could blow into a mouthpiece integrated into your phone and get information about your health in real time,” said Jun Ye, a JILA fellow and adjoint professor of physics who helped develop the technology along with physics doctoral candidate Qizhong Liang.

Humans exhale more than 1,000 distinct molecules with each breath, producing a unique chemical fingerprint or “breath print” filled with clues about what’s happening deep inside them. Scientists have long sought to harness that information, turning to dogs and other animals to sniff out cancer, diabetes and more.

Liang and Ye’s “frequency comb breathalyzer” could someday do the sniffing instead.

It uses frequency comb lasers, which feature narrow optical lines spread across a vast spectral window, to distinguish between different kinds of breath molecules, which are known to vary in concentration when people are sick. Paired with sophisticated algorithms for machine learning and data analysis, their laser-based nose has been shown to be able to detect whether someone has COVID-19 in a matter of seconds.

Research is underway, in close collaboration with medical doctors from the CU Anschutz Medical Campus, to see if breath can also be used to detect chronic obstructive pulmonary disease (COPD), pediatric respiratory issues and even lung cancer. The team also plans to miniaturize their technology.

In 2023, Flari Tech Inc.—named after the word ‘flari’ (“to smell”) in the Esperanto language—was formed to help move the technology from the lab to the bedside. Much more research is necessary, but ultimately the researchers believe their work could lead to earlier diagnoses for patients—and save lives.

Space Dust Research & Technologies: Tools for cleaning up dust on the moon

When future astronauts travel to the moon, they’ll face a little-known problem: The moon’s dust, or regolith, is made up of particles as sharp as glass that stick to everything.

“As we learned from the Apollo missions, lunar dust readily sticks to all surfaces of exploration systems, causing damage to spacesuits, degrading thermal radiators and solar panels and posing risks to crew health when inhaled,” said Xu Wang, a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder.

Wang and Mihály Horányi, professor of physics and a researcher at LASP, launched a company to help. will pioneer technology known as Electron-beam Lunar Dust Mitigation (ELDM). ELDM devices generate a beam of electrons that add electric charges to those sticky particles of dust—causing them to, literally, jump off of surfaces.

This technology is versatile enough that it could work in handheld devices or in larger “car washes” that could clean entire spacesuits or rovers.

Space Dust Research & Technologies will also develop a separate type of technology that can sort through dust on the moon and arrange grains by size—an important step in mining regolith to turn it into building materials and more. The company’s work emerged out of years of research in LASP’s NASA-funded Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) lab.

Biosensor Solutions: Biodegradable sensors for tracking soil microbes

Scientists have long known that healthy soils and crops depend on vibrant communities of bacteria and other microbes living in the dirt. There’s just one problem: These microbial communities can be difficult to keep track of.

Until now. Engineer Gregory Whiting and his team at CU Boulder recently invented a way to measure soil microbial communities using low-cost, printed sensors. The trick: tasty electronics. The sensors include biodegradable resistors that soil microbes eat and degrade over time.

“It’s like a bait for microbes,” said Whiting, associate professor in the Paul M. Rady Department of Mechanical Engineering. “As they eat the device, the signal changes.”

That, in turn, could allow farmers to get a sense of how many microbes are in their soil.

The Boulder-based company , led by co-founders David Beitz and Carl Kalin, licensed this technology in 2024. The group is currently piloting the sensors with an initial group of local companies, precision agriculture providers and growers. According to company officials, “Data and insights from these new sensors will help growers increase yields and save resources on water, fertilizer, pesticides and herbicides.”

Mesa Quantum: Navigation devices based on the behavior of atoms

One new startup could make it easier to navigate the globe, even when GPS satellites go out, such as during bad storms.

For decades, scientists at the National Institute of Standards and Technology (NIST) have pioneered the technology of atomic clocks. These devices keep track of time and can help to track your location by measuring the behavior of electrons whizzing around atoms.

Svenja Knappe, associate research professor in the Paul M. Rady Department of Mechanical Engineering at CU Boulder, recently helped to improve on those inventions. She discovered a way to make atomic clocks more reliable while also shrinking them down to the size of a computer chip.

Sristy Agrawal and Wale Lawal, who founded Mesa Quantum in 2024, have high hopes for these chips. They say the company's atomic clocks could one day become part of a suite of technologies that enable GPS-free navigation—allowing anyone, from farmers to airplane pilots, to pinpoint their locations on Earth more reliably and precisely than ever before.

“The agricultural sector in babyֱ��app relies heavily on GPS for the operation of tractors, irrigation systems and other modern equipment,” said Agrawal, who earned her doctorate in physics from CU Boulder in 2024. “As the industry moves toward greater automation, these systems will become even more dependent on precise and reliable positioning data.”

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