Category: material science

Leading the Way for Quantum Research

From table-top experiments to theories about the universe, Berkeley Physics guides diverse efforts in quantum information science

A century ago, science went quantum. In recognition of the progress made since this initial development of quantum mechanics, 2025 is being celebrated as the International Year of Quantum Science and Technology.

According to the quantum view of nature, matter absorbs energy in tiny discrete packets. And seemingly disconnected objects can be entangled, their properties correlated by intangible links—even if they are light years apart.

Initially, quantum mechanics was something specialized physicists thought about, including posing philosophical questions like whether Schrödinger’s quantum cat is simultaneously dead and alive. Beginning in the 1970s, however, these theories were tested by experiments that proved entanglement is real and fundamental to nature. The first definitive proof of quantum spookiness took place experimentally in Birge Hall and was recognized by the 2022 Nobel Prize in Physics. Since the 1990s, lots of quantum research focuses on how to develop quantum technologies.

“Quantum mechanics has transformed from a philosophy to an engineered product—that’s a very big deal,” says Irfan Siddiqi, Berkeley Physics professor and chair. “Bringing these technologies to the market to change our everyday world requires people from industry, academia, and venture capital to come together. Berkeley is at the center of this convening effort, because it offers a unique entrepreneurial ecosystem with broad and diverse efforts in quantum information science.”

Cutting-edge researchers at Berkeley Physics lead investigations of all competing technologies for creating and manipulating qubits, the basic unit of information in quantum computing—including research on cold atom arrays by Professor Dan Stamper-Kurn, superconducting circuits by Siddiqi, trapped ions by Professor Hartmut Haeffner, and advanced quantum materials by various faculty. Berkeley also has world-leading theoretical physicists such as Professor Raphael Bousso, mathematicians, and computer scientists exploring fundamental aspects of quantum information. We highlight only a few of these efforts here.

Table-Top Experiments with Ultracold Atoms

Although quantum research has made amazing progress over the last 100 years, we’re still really far from building a quantum computer that you could use at home, according to Stamper-Kurn.

“We also still don’t know if a quantum computer is good for much. We know they can factorize large integers and simulate quantum mechanical systems, which classical computers will never be able to do at the same scale,” he explains. “We take it on faith that this is just the tip of an enormous ice berg, but that isn’t proven yet.”

However, needing to tackle these big challenges means Berkeley physicists have tons of interesting research ahead, including work led by Stamper-Kurn at the NSF Challenge Institute for Quantum Computation (CIQC).

“We use the term institute because we’re trying to do something more curiosity-driven and longer-term than a single research project with a specific deliverable. I think academia’s role should be to know where the road is taking us, but to also be willing to look at the side roads—find technology breakthroughs by stumbling around and bring them to the fore,” say Stamper-Kurn.

At CIQC, his multidisciplinary team of physicists, computer scientists, mathematicians, chemists, and engineers pursue three overarching goals. The first is to engineer large-scale coherent quantum systems, which is where Stamper-Kurn and Siddiqi overlap a lot. The second goal is to realize the quantum computer and figure out what it can do, which leads CIQC researchers to interact with a wide range of physicists and computer science theorists. The third goal is to use concepts of quantum information science to understand the natural world, and that’s where Stamper-Kurn learns from Bousso.

More specifically, Stamper-Kurn’s group performs table-top experiments using light and ultracold atomic gases—perhaps the coldest matter in the universe. At temperatures below one nano-kelvin, noise is “ironed out” and the quantum mechanical properties of these atoms are uniquely accessible and visible. Their goal is to image, with high resolution, individual cold atoms to provide extremely sensitive quantum measurements.

In the E6 ultracold atoms lab, his team studies how a single or array of ultracold atoms interact within the optical field of a high-finesse optical cavity, where light shined into the cavity bounces back and forth thousands of times between two end mirrors. Since light is trapped in the cavity for so long, it interacts very strongly with any atoms inside.

Optical tweezers, consisting of highly focused laser beams sent through a high-resolution lens, are used to control the atoms. They precisely trap atoms in different locations of the cavity or manipulate the state of an individual atom. The team also uses the high-resolution lens to collect light from the atoms as it comes out of the cavity, which then passes through an imaging system and is focused onto a camera.

“We use arrays of optical tweezer traps to position arrays of neutral atoms within a cavity, achieving unprecedented control of the position, internal state, and optical response of each individual atom,” says Stamper-Kurn. 

“This setup has allowed us to realize breakthroughs in quantum computing, including our recent rapid mid-circuit measurement of atom tweezer arrays,” he explains. “We use the very strong interaction between atoms and light to read out the state of an atom very rapidly—about 1000 times faster than previous experiments using optical tweezers. But real applications require measuring part of a quantum processor while the rest of it keeps computing. Our technique is also very selective, where only the atom we measured was disturbed.”

Additionally, CIQC supports the entire campus in its development of quantum science, including funding and organizing “Quantum Gatherings” attended by students, postdocs, and faculty from various departments. Held every other Friday, someone from the broader Berkeley quantum community gives a provocative 20-minute spark talk followed by an hour-long discussion.

A Berkeley undergraduate student who attended the gatherings sent Stamper-Kurn a note saying, “Thank you for sparking my interest in quantum science. I came for the pizza, and I stayed for the science.”

These gatherings are the “sweet place” where Stamper-Kurn, Siddiqi, Bousso, and their groups interact. “We can be seen chewing pizza and talking about physics every two weeks outside of Campbell Hall. We understand this is a long-term and necessarily multidisciplinary effort to create an ecosystem for quantum information science,” Stamper-Kurn says.

Full-stack Applications with Superconducting Systems

While Stamper-Kurn performs table-top cold atom experiments, Siddiqi’s Quantum Nanoelectronics Lab (QNL) works on a larger scale with full-stack quantum computers using superconducting devices. This comprehensive program includes developing materials and processors and integrating them into platforms with controls and applications layers.

QNL has its own clean room and cryogenics for building and operating large superconducting systems on campus. Siddiqi is also the director of the Advanced Quantum Testbed at Berkeley Lab, which offers white-box access to superconducting quantum computers through a user program.

“My large team has fingers in many pots. We have many quantum computers running based on a range of superconducting hardware,” says Siddiqi. “We’re still at a stage where we haven’t figured out what the right qubit is, how to use it, and how to connect it—before scaling up.”

Siddiqi focuses on superconducting platforms because they are open quantum systems that naturally exchange information with the environment. These systems already have many “knobs,” so the challenge is figuring out how to interface with them properly, he says.

“This is a new chapter in quantum mechanics, originally a theory of closed quantum systems. We’re now looking at how to measure and engineer open quantum systems, both for computation but also to explore the most fundamental questions,” says Siddiqi.

One technology QNL is developing is a quantum information processor that uses entangled three-level quantum systems, or qutrits.

In a classical computer, a bit is a 0 or 1, represented by on-off switches in hardware. But what if the switch could exist as a coherent superposition of 0, 1, and the states in between simultaneously—think, the Schrödinger cat is both alive, dead, and a zombie? And what if the switches in a computer could consult each other before outputting a calculation?

For example, a quantum computer with an entangled array of N two-level qubits can represent 2N possible states—far more than the N states of a classical computer—enabling it to perform calculations on many possibilities in parallel. And that’s just a binary system.

A three-level qutrit system offers an even larger and more connected computational space that increases with 3N. But as you add levels, it becomes more challenging to control and entangle them while making them robust against undesired noise, crosstalk, and errors.

Siddiqi’s team tackled these challenges, experimentally implementing faster, flexible, and tunable microwave-activated entanglement with three or more levels.

Using their new approach for entanglement, Siddiqi’s team developed two types of high-quality two-qutrit gates, a controlled-Z gate and a controlled-Z inverse gate—decreasing the gate’s error rate by a factor of four over previous efforts, leading to higher computational performance.

“In a static case, when the qutrits are not driven by electromagnetic fields, they’re not coupled. But if we periodically drive the qutrits, like a pendulum back and forth, we can create entanglement on demand—and that’s a powerful tool,” says Siddiqi. “That obeys different rules, so we’re able to create this N-body entanglement.”

This significant step forward for operating multi-qutrit devices will help pave the way for a deeper understanding of ternary quantum logic, which can encode more information in quantum processors than qubits.

More generally, Siddiqi is also leading efforts to create a horizontal ecosystem for quantum technologies at Berkeley and beyond, including founding the consortium Berkeley Quantum Works, which fosters partnerships between the device fabrication and measurement facilities housed on the Berkeley campus and startup-stage companies who make quantum processors, components, and software.

Theories on Quantum Information in the Universe

Berkeley’s quantum efforts go beyond developing and using advanced technologies for quantum computation. Colleagues like Bousso are investigating quantum on the scale of the universe.

“Raphael is thinking about the universality of quantum information as a currency to describe the physical world—both in the celestial, gravitational, and cosmology sense and in the computing sense,” describes Siddiqi.

The Bousso group uses diverse tools and techniques to investigate the increasingly important intersection of quantum information and quantum gravity.

The field of quantum gravity seeks a unified theory of our universe that includes both quantum mechanics and general relativity. It generally focuses on the interplay between spacetime geometry, quantum information theory, and relativistic field theory. However, according to Bousso, this theoretical challenge is really about how quantum information and gravity are intertwined.

“It’s about hunting the thrill of quantum gravity. Once we really understand it, there’s every reason to believe it’s going to revolutionize how we think about the world,” says Bousso, who is the Chancellor’s Chair in Physics.

Much of Bousso’s research focuses on black holes, which are massive deformations of the shape of space and time.

“Black holes are where we can sharpen what we don’t understand about quantum gravity—where we can turn vague confusions into a sharp paradox,” says Bousso. “For example, in the black hole information paradox, either black holes destroy quantum information in which case quantum mechanics is terribly wrong or you can’t cross a black hole’s horizon in which case general relatively is terribly wrong. These paradoxes force us to make stark choices, like which principle to give up, and that blossoms progress.”

Another fundamental question concerns a black hole’s singularity, the point of infinite density and gravity within its event horizon where all concepts of time and space break down. Can you evade that singularity with quantum corrections?  

Some theoretical models of quantum gravity suggest that the singularity inside a black hole is not a true point of infinite density, but instead a region where spacetime undergoes a bounce, potentially transitioning to a white hole. This could resolve the information paradox. Other theorists suggest that the universe is infinitely cyclically bouncing between contraction and expansion, replacing the “big bang” with a “big bounce” theory.

Bousso recently ruled out these sorts of cyclic cosmologies with his Robust Singularity Theorem, showing that you cannot get through such bounces.

“People have tried playing with many ideas like this, formulated at various levels of rigor and with varying levels of plausibility. What’s nice is that my theorem rules them out regardless of the details,” he says.

His Robust Singularity Theorem expanded the validity of the Penrose-Wall singularity theorem, which showed singularities really exist and they arise in many situations in general relativity when spacetime contains a trapped surface and specific conditions are met. Whereas the Penrose-Wall theorem applied to a mathematically idealized case, Bousso’s more general theorem represents a big advance.

Bousso’s work largely focuses on black holes and gravity, but he’s ultimately exploring fundamental questions of entanglement and quantum information. And he’s using ideas from other fields, including quantum information theory and quantum communication protocols, that were motivated by seemingly entirely different problems.

 And what he learns about these fundamental questions has the attention of his experimental colleagues. In addition to working with Berkeley Physics experimentalists, he is part of the GeoFlow consortium that includes experimentalists at Stanford and Duke universities.

 “The depth at which really sophisticated concepts in quantum information theory are baked into gravity has led us to have something to say to people who are interested in benchmarking their quantum computing platforms,” explains Bousso. “It’s a whole new ecosystem we’re developing, connecting people like me studying quantum gravity to condensed matter theorists and even atomic, molecular, and optical physics experimentalists. It’s fun and has been the best part of my career.”

Irfan concludes, “At first the people from different fields working on quantum spoke different languages, but now they are all very fluent.”

This is a reposting of my magazine feature, courtesy of UC Berkeley’s 2025 Berkeley Physics Magazine.

Revitalizing batteries by bringing ‘dead’ lithium back to life


An animation shows how charging and discharging a lithium battery test cell causes an island of “dead,” or detached, lithium metal to creep back and forth between the electrodes. The movement of lithium ions back and forth through the electrolyte creates areas of negative (blue) and positive (red) charge at the ends of the island, which swap places as the battery charges and discharges. Lithium metal accumulates at the negative end of the island and dissolves at the positive end; this continual growth and dissolution causes the back-and-forth movement seen here. SLAC and Stanford researchers discovered that adding a brief, high-current discharging step right after charging the battery nudges the island to grow in the direction of the anode, or negative electrode. Reconnecting with the anode brings the island’s dead lithium back to life and increases the battery’s lifetime by nearly 30%. (Greg Stewart/SLAC National Accelerator Laboratory.)

Menlo Park, Calif. — Researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University may have found a way to revitalize rechargeable lithium batteries, potentially boosting the range of electric vehicles and battery life in next-gen electronic devices.

As lithium batteries cycle, they accumulate little islands of inactive lithium that are cut off from the electrodes, decreasing the battery’s capacity to store charge. But the research team discovered that they could make this “dead” lithium creep like a worm toward one of the electrodes until it reconnects, partially reversing the unwanted process.

Adding this extra step slowed the degradation of their test battery and increased its lifetime by nearly 30%.

“We are now exploring the potential recovery of lost capacity in lithium-ion batteries using an extremely fast discharging step,” said Stanford postdoctoral fellow Fang Liu, the lead author of a study published Dec. 22 in Nature.

Lost connection

A great deal of research is looking for ways to make rechargeable batteries with lighter weight, longer lifetimes, improved safety, and faster charging speeds than the lithium-ion technology currently used in cellphones, laptops and electric vehicles. A particular focus is on developing lithium-metal batteries, which could store more energy per volume or weight. For example, in electric cars, these next-generation batteries could increase the mileage per charge and possibly take up less trunk space.

Both battery types use positively charged lithium ions that shuttle back and forth between the electrodes. Over time, some of the metallic lithium becomes electrochemically inactive, forming isolated islands of lithium that no longer connect with the electrodes. This results in a loss of capacity and is a particular problem for lithium-metal technology and for the fast charging of lithium-ion batteries.

However, in the new study, the researchers demonstrated that they could mobilize and recover the isolated lithium to extend battery life.

“I always thought of isolated lithium as bad, since it causes batteries to decay and even catch on fire,” said Yi Cui, a professor at Stanford and SLAC and investigator with the Stanford Institute for Materials and Energy Research (SIMES) who led the research. “But we have discovered how to electrically reconnect this ‘dead’ lithium with the negative electrode to reactivate it.”

Creeping, not dead

The idea for the study was born when Cui speculated that applying a voltage to a battery’s cathode and anode could make an isolated island of lithium physically move between the electrodes – a process his team has now confirmed with their experiments.

The scientists fabricated an optical cell with a lithium-nickel-manganese-cobalt-oxide (NMC) cathode, a lithium anode and an isolated lithium island in between. This test device allowed them to track in real time what happens inside a battery when in use.

They discovered that the isolated lithium island wasn’t “dead” at all but responded to battery operations. When charging the cell, the island slowly moved towards the cathode; when discharging, it crept in the opposite direction.

“It’s like a very slow worm that inches its head forward and pulls its tail in to move nanometer by nanometer,” Cui said. “In this case, it transports by dissolving away on one end and depositing material to the other end. If we can keep the lithium worm moving, it will eventually touch the anode and reestablish the electrical connection.”

Boosting lifetime

The results, which the scientists validated with other test batteries and through computer simulations, also demonstrate how isolated lithium could be recovered in a real battery by modifying the charging protocol.

“We found that we can move the detached lithium toward the anode during discharging, and these motions are faster under higher currents,” said Liu. “So we added a fast, high-current discharging step right after the battery charges, which moved the isolated lithium far enough to reconnect it with the anode. This reactivates the lithium so it can participate in the life of the battery.”

She added, “Our findings also have wide implications for the design and development of more robust lithium-metal batteries.”

This work was funded by the DOE Office of Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under the Battery Materials Research (BMR), Battery 500 Consortium and eXtreme Fast Charge Cell Evaluation of Li-ion batteries (XCEL) programs.

This is a reposting of a press release, courtesy of SLAC National Accelerator Laboratory.

SLAC’s Riti Sarangi wins 2021 Farrel W. Lytle Award

Ritimuka “Riti” Sarangi is this year’s Lytle Award recipient. (Jacqueline Ramseyer Orrell/SLAC National Accelerator Laboratory)

Ritimukta “Riti” Sarangi, a senior scientist at the Department of Energy’s SLAC National Accelerator Laboratory, is the latest recipient of the Farrel W. Lytle Award, which recognizes important contributions to synchrotron science and efforts to support users at the Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science user facility.  

Since its inception in 1998, the Farrel W. Lytle Award has been given annually to SSRL staff members and users from around the world.

“Farrel is a legend in X-ray spectroscopy science. He has made contributions to every aspect of X-ray instrumentation, measurement and analysis,” Sarangi said. “I was completely unaware of my nomination and was thrilled when I received the email” notifying her of the award.

Sarangi started running experiments at SSRL in 2001, when she was a graduate research assistant at Stanford University. After earning her PhD in chemistry, she joined the SSRL staff in 2007. She is currently a senior member of the Structural Molecular Biology group at SSRL and a hard X-ray spectroscopist.

In a nomination letter for the award, Graham George, the Canada research chair in X-ray absorption spectroscopy at the University of Saskatchewan, praised Sarangi’s contributions in research, user support, outreach and leadership. “While SSRL scientific staff includes many outstanding individuals, even among this strong competition Riti stands out,” he wrote. “I have heard Riti described by senior SSRL management as an ‘anchor at SSRL,’ and I think that this description is an accurate one.”

Catalyzing discoveries

Sarangi uses X-ray spectroscopy techniques to study the fundamental properties of enzymes, molecules produced by a living organism that act as a catalyst to bring about specific biochemical reactions. Much of her research focuses on metalloenzymes, a broad group of enzymes with one or more metal ions in their active site, where other molecules bind and undergo a chemical reaction.

“Metalloenzymes perform a wide range of chemical transformations from electron transfer to small molecule activation to more complex molecular transformations,” explained Sarangi. “My goal is to apply X-ray methods towards understanding the structural and electronic details of these metal-containing active sites to shed light on the functional details of metalloenzymes and related systems.”

She is particularly interested in understanding methyl coenzyme M reductase (MCR), a unique nickel-containing enzyme responsible for the generation of 1 billion metric tons of methane annually.

Methane is the main component of natural gas and accounts for almost a quarter of U.S. energy consumption, but it is also a potent greenhouse gas. Understanding the mechanistic aspects of methane activation and synthesis is, therefore, imperative from fundamental, applied-energy, economic and environmental perspectives, Sarangi said.

Sarangi investigates metalloenzymes like MCR using modern X-ray spectroscopic tools and advanced computer simulations that model the quantum physics underlying chemical reactions.

“While spectroscopy provides an experimental window into specific properties about your system, quantum simulation methods provide additional information about structure, bonding and reactivity properties,” she said. “Experiments answer the what and theory answers the why given this specific what.”

Her nominators noted the powerful and unusual nature of her combined methodology. Stephen Ragsdale, professor of Biological Chemistry at the University of Michigan, wrote, “Riti’s approach is continuing to close the gap between experimental and computational aspects of X-ray spectroscopy. It is also absolutely crucial in understanding the complex biological systems that we and others are studying.”

In one recent study, Sarangi and colleagues combined a variety of experimental and theoretical techniques to uncover how enzymes help synthesize methane, revealing a surprising way the enzyme binds to the chemical it converts to methane. Ragsdale called the research “an extraordinary feat.”

Supporting users

Sarangi does a lot more than groundbreaking research, spending much of her time supporting the SSRL user community. “Riti is engaged at every level with user support and is someone who is not afraid to get her hands dirty,” George wrote.

For example, she developed a computer cluster for implementing various theoretical packages that simulate, interpret or augment experimental X-ray spectroscopy data.

“When I started at SSRL in a user support role, I realized these theoretical tools were rarely leveraged by our biological user community and therefore the full potential of their X-ray datasets was often not realized,” said Sarangi. “While I have continued to apply theoretical tools to my own research program, I have also established and made available a high-speed computational cluster to the entire bio-spectroscopy and bio-inspired catalysis user community.”

She has also been crucial to keeping SSRL running during the COVID-19 pandemic, her nominators said.

“She played a pivotal role in generating online access programs and coordinating communication and timeline details so users could continue to accomplish our science during the time when SSRL was closed for visitors,” Timothy Stemmler, assistance vice president for research and professor of pharmaceutical sciences at Wayne State University, wrote in a letter. “Her efforts to allow online access will surely transform how data is collected at the entire lab moving forward, and will lead to many future discoveries, he wrote.

The nominators also applauded Sarangi’s mentoring, training and recruitment of the next generation of scientists. “She has clear skills in organizing and delivering training content and this sets her apart as not just an amazing colleague, but an amazing educator,” wrote Stemmler.

Envisioning the future

Looking forward, Sarangi thinks the lessons learned during the pandemic suggest that more researchers could work remotely – something she said accelerated her scientific and operational engagement with staff, users and collaborators. In 20 years, she expects SSRL X-ray science to become an automated and high-throughput experience that integrates multiple complementary X-ray and non-X-ray measurements.   

She is also leading efforts to plan the future of structural science at lightsources, based on a series of workshops whose reports will develop a robust case for investing in X-ray science.

“This is no easy task and has required mastering the details of techniques adjacent to her expertise, diplomacy in bringing diverse ideas in different disciplines together, and hard work,” wrote Edward Snell, chief executive officer of the Hauptman-Woodward Medical Research Institute, in a nominating letter.

George also praised Sarangi’s leadership and vision. “I have had the distinctive privilege of knowing Farrel quite well, and I am certain that he would approve of this nomination,” he wrote. “The SSRL Users’ executive committee would be hard pressed to find a better candidate.”

The award will be presented to Sarangi at the 2021 SSRL/LCLS Annual Users’ Meeting during the plenary session on September 24. 

For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.

This is a reposting of my news story, courtesy of SLAC National Accelerator Laboratory.

Stanford graduate student Aisulu Aitbekova wins 2021 Melvin P. Klein Award

Aisulu Aitbekova

Aisulu Aitbekova, a 2021 doctoral graduate from Stanford University, discovered her passion for research when she traveled from Kazakhstan to the U.S. for a summer internship as a chemical engineering undergraduate. She said that experience inspired her to go to graduate school.

After earning a master’s in chemical engineering at the Massachusetts Institute of Technology, she continued her studies at Stanford University under the supervision of Matteo Cargnello, an assistant professor of chemical engineering and Aitbekova’s doctoral advisor. Much of her thesis work involved beamline studies at the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy’s SLAC National Accelerator Laboratory.  

Now, Aitbekova has been selected to receive the 2021 Melvin P. Klein Scientific Development Award, which recognizes outstanding research accomplishments by undergraduates, graduate students and postdoctoral fellows within three years of completing their doctoral degrees.

In a nomination letter for the award, SLAC Distinguished Staff Scientist Simon Bare praised Aitbekova’s initiative. “She has quickly become proficient in the application of X-ray techniques available at the synchrotron at SLAC. This proficiency and mastery include everything from operating the beamline to analyzing and interpreting the data,” he wrote.

Aitbekova said she felt “absolutely thrilled and grateful” to all of her mentors when she found out about winning the award.

“I’m so thankful for my PhD advisor Matteo Cargnello. My success would not have been possible without his mentorship,” Aitbekova said. “I’m also particularly grateful to Simon Bare, who I consider to be my second advisor. His continuous excitement about X-ray absorption spectroscopy has been the driving force for my work at SSRL.” 

Catalyzing change

Aitbekova said she is passionate about finding solutions to combat climate change. She designs materials to convert harmful pollutant gases into useful fuels and chemicals. To perform these chemical transformations, she develops catalysts and studies their properties using X-ray absorption spectroscopy (XAS). Catalysts are substances that increase rates of chemical reactions without being consumed themselves.

“I have identified that a catalyst’s size, shape and composition profoundly affect its performance in eliminating these gases,” but exactly how those properties affect performance remains unknown, she said. “This problem is further complicated by the dynamic nature of catalytic materials. As a catalyst performs chemical transformations, its structure changes, making it challenging to precisely map a catalyst’s properties to its performance.”

To overcome these barriers, she engineers materials the size of one ten-thousandth the diameter of a human hair and then tracks how they change during reactions using XAS.

In one study, Aitbekova and her colleagues engineered a catalyst using a combination of ruthenium and iron oxide nanoparticles, which they think act in a tag-team fashion to improve the synthesis of fuels from carbon dioxide and hydrogen. Using a prototype in the lab, they achieved much higher yields of ethane, propane and butane than previous catalysts.

Switching gears

While engineering catalysts that convert carbon dioxide into chemicals, she developed a new approach for preparing materials, where small particles are encapsulated inside porous oxide materials – for example, encapsulating ruthenium within a sheath of iron.

However, Aitbekova recognized a completely different application for this new approach: creating a palladium-platinum catalyst that works inside a car’s emission control system.

To eliminate the discharge of noxious emission gases, cars are equipped with a catalytic converter. Exhaust gases pass into the catalytic converter, where they are turned into less harmful gases. The catalysts inside these units are platinum and palladium metals, but these metals gradually lose their efficiency due to their extreme working conditions, she said.

“My platinum and palladium catalysts show excellent stability and performance after being subjected to air and steam at 1,100 degrees Celsius, the harshest operating environment automotive exhaust emission control catalysts could be subjected to,” explained Aitbekova. “Further improvements in these materials and successful testing under true exhaust conditions have a potential to revolutionize the field of automotive exhaust emission control.”

Her nominators agreed, citing it as the highlight of her graduate career.

“This work, currently under review for publication, is truly the remarkable result of Aisulu’s hard work and experience in pivoting from one area to another to make an impact and of her ability to connect multiple fields and solve important problems,” Cargnello wrote.

Amplifying impact

Despite this success, Aitbekova is already focused on how to make an even greater impact through mentoring and future research.

Her nominators all applauded her passion and commitment to mentor the next generation of STEM scholars, as demonstrated by mentoring “a countless number of undergraduates” according to Cargnello and by exchanging letters with middle school students from underrepresented groups.

Part of this passion, Cargnello and others wrote, stems from her experiences growing up in a highly conservative environment with the understanding that homemaking would be her eventual job. Aitbekova’s nominators wrote that they admired the fact that she made her way to Stanford and has acted as an ambassador for the values and principles of diversity and inclusion.

Aitbekova said she embraces the role. “Since my first summer research experience in the USA, I’ve wanted to serve as a bridge to science and graduate school to those who, like me, didn’t have access to such knowledge and resources.”

She will continue to act as a bridge in her next endeavor as a Kavli Nanoscience Institute Prize Postdoctoral Fellow at Caltech, where she plans to expand her work of converting carbon dioxide into fuels by running the chemical transformations with solar energy. That will “bring society one step closer to sustainable energy sources,” she said.

Bare and others praised her drive to make an everyday impact. “She has a natural passion for wanting to understand the physical principles behind the phenomena that she has observed in her research. But this passion for understanding is nicely balanced by her desire to discover something new, and to make a real difference — the practicality that is often missing in someone early in their career,” wrote Bare.

The award will be presented to Aitbekova at the 2021 SSRL/LCLS Annual Users’ Meeting during the plenary session on September 24. 

This is a reposting of my news story, courtesy of SLAC National Accelerator Laboratory.

Nerve interface provides intuitive and precise control of prosthetic hand

Current state-of-the-art designs for a multifunctional prosthetic hand are restricted in functionality by the signals used to control it. A promising source for prosthetic motor control is the peripheral nerves that run from the spinal column down the arm, since they still function after an upper limb amputation. But building a direct interface to the peripheral nervous system is challenging, because these nerves and their electrical signals are incredibly small. Current interface techniques are hindered by signal amplitude and stability issues, so they provide amputees with only a limited number of independent movements. 

Now, researchers from the University of Michigan have developed a novel regenerative peripheral nerve interface (RPNI) that relies on tiny muscle grafts to amplify the peripheral nerve signals, which are then translated into motor control signals for the prosthesis using standard machine learning algorithms. The research team has demonstrated real-time, intuitive, finger-level control of a robotic hand for amputees, as reported in a recent issue of Science Translational Medicine.

“We take a small graft from one of the patient’s quadricep muscles, or from the amputated limb if they are doing the amputation right then, and wrap just the right amount of muscle around the nerve. The nerve then regrows into the muscle to form new neuromuscular junctions,” says Cindy Chestek, an associate professor of biomedical engineering at the University of Michigan and a senior author on the study. “This creates multiple innervated muscle fibers that are controlled by the small nerve and that all fire at the same time to create a much larger electrical signal—10 or 100 times bigger than you would record from inside or around a nerve. And we do this for several of the nerves in the arm.”

This surgical technique was initially developed by co-researcher Paul Cederna, a plastic surgeon at the University of Michigan, to treat phantom limb pain caused by neuromas. A neuroma is a painful growth of nerve cells that forms at the site of the amputation injury. Over 200 patients have undergone the surgery to treat neuroma pain.

“The impetus for these surgeries was to give nerve fibers a target, or a muscle, to latch on to so neuromas didn’t develop,” says Gregory Clark, an associate professor in biomedical engineering from the University of Utah who was not involved in the study. “Paul Cederna was insightful enough to realize these reinnervated mini-muscles also provided a wonderful opportunity to serve as signal sources for dexterous, intuitive control. That means there’s a ready population that could benefit from this approach.”

The Michigan team validated their technique with studies involving four participants with upper extremity amputations who had previously undergone RPNI surgery to treat neuroma pain. Each participant had a total of 3 to 9 muscle grafts implanted on nerves. Initially, the researchers measured the signals from these RPNIs using fine-wire, nickel-alloy electrodes, which were inserted through the skin into the grafts using ultrasound guidance. They measured high-amplitude electromyography signals, representing the electrical activity of the mini-muscles, when the participants imagined they were moving the fingers of their phantom hand. The ultrasound images showed the participants’ thoughts caused the associated specific mini-muscles to contract. These proof-of-concept measurements, however, were limited by the discomfort and movement of the percutaneous electrodes that pierced the skin.

Next, the team surgically implanted permanent electrodes into the RPNIs of two of the participants. They used a type of electrode commonly used for battery-powered diaphragm pacing systems, which electrically stimulate the diaphragm muscles and nerves of patients with chronic respiratory insufficiency to help regulate their breathing. These implanted electrodes allowed the researchers to measure even larger electrical signals—week after week from the same participant—by just plugging into the connector. After taking 5 to 15 minutes of calibration data, the electrical signals were translated into movement intent using machine learning algorithms and then passed on to a prosthetic hand. Both subjects were able to intuitively complete tasks like stacking physical blocks without any training—it worked on the first try just by thinking about it, says Chestek. Another key result is that the algorithm kept working even 300 days later.

“The ability to use the determined relationship between electrical activity and intended movement for a very long period of time has important practical consequences for the user of a prosthesis, because the last thing they want is to rely on a hand that is not reliable,” Clark says.

Although this clinical trial is ongoing, the Michigan team is now investigating how to replace the connector and computer card with an implantable device that communicates wirelessly, so patients can walk around in the real world. The researchers are also working to incorporate sensory feedback through the regenerative peripheral nerve interface. Their ultimate goal is for patients to feel like their prosthetic hand is alive, taking over the space in the brain where their natural hand used to be.

“People are excited because this is a novel approach that will provide high quality, intuitive, and very specific signals that can be used in a very straightforward, natural way to provide high degrees of dexterous control that are also very stable and last a long time,” Clark says.

Read the article in Science Translational Medicine.

Illustration of multiple regenerative peripheral nerve interfaces (RPNIs) created for each available nerve of an amputee. Fine-wire electrodes were embedded into his RPNI muscles during the readout session. Credit: Philip Vu/University of Michigan; Science Translational Medicine doi: 10.1126/scitranslmed.aay2857

This is a reposting of my news brief, courtesy of Materials Research Society.

Hydrogel elicits switchable, reversible, and controllable self-trapping light beams

The next generation of optoelectronic and photonic systems — with wide-ranging potential applications in image transmission, light-guiding-light signal processing, logic gates for computing, and medicine — may be realized through the invention of circuitry-free, rapidly reconfigurable systems powered by solitons. Optical spatial solitons are self-trapped optical beams of finite spatial cross section that travel without diverging like freely diffracting beams. These nonlinear waves propagate in photoresponsive materials through self-inscribed waveguides, which are generated when the materials locally change their refractive index in response to light intensity. In conventional nonlinear materials, self-trapping requires high-powered lasers or external electric fields.

Now, a team of researchers from the University of Pittsburgh, Harvard University, and McMaster University have developed a pH-responsive poly(acrylamide-co-acrylic acid) hydrogel, a hydrophilic three-dimensionally connected polymer network, in which light self-trapping can be turned rapidly on and off many times in a controllable and reversible way using a low-intensity visible laser. They reported their work in a recent issue of Proceedings of the National Academy of Sciences.

Developed by Joanna Aizenberg’s group at Harvard University, the hydrogel contains critical covalently-tethered chromophores that absorb specific wavelengths of visible light and thereby transform their structure. In the absence of light, the gel is relaxed and the chromophores are predominantly in a ring-open merocyanine form. When the hydrogel is irradiated with visible light, the isomerization of merocyanine to its closed-ring spiropyran form triggers a local expulsion of water, a contraction of the hydrogel, and ultimately an increase in the refractive index along the irradiated path.

The novelty of this work is that this isomerization process is reversible. In the absence of light, the hydrogel reverts back to its original state.

The researchers demonstrated the reversible self-trapping process with experiments led by Kalaichelvi Saravanamuttu’s team at McMaster University—measuring the diameter and peak intensity of the beam over time using a 532 nm laser, optical lenses, neutral density filters, and a CCD camera. They also performed a series of control experiments, such as testing the hydrogel matrix without chromophores, to determine which parameters are critical for self-trapping.

“We determined it was important to have a hydrogel matrix that became more hydrophobic in the presence of light. It was important to have the chromophores covalently-tethered to the three-dimensional matrix to localize the refractive index change. And photoisomerization was critical in triggering this sequence of events,” says Saravanamuttu, an associate professor of chemistry and chemical biology and a senior author on the paper.

More surprising, when the researchers irradiated the hydrogel with two parallel lasers, the self-trapping beams interacted with each other when separated by distances up to 10 times the beam width. “They modulated each other, reducing their self-trapping efficiency, at remote distances through the interconnected and flexible network of the hydrogel,” Saravanamuttu says.

Being able to reversibly, predictably, and remotely control one self-trapped beam with another opens up the possibility of applications like all-optical computing using beams of ambient light. Traditional computations are performed using hard materials such as wires, semiconductors and photodiodes to couple electronics to light. Instead, the team hopes to control light with light. So far, they have already used the interactions of self-trapped beams to do basic binary arithmetic, says Saravanuamuttu.

These experimental results were confirmed by numerical simulations developed by senior authors Aizenberg, a professor of materials science and of chemistry and chemical biology at Harvard University, and Anna Balazs, a professor of chemical and petroleum engineering at the University of Pittsburgh, and their groups. Their model dynamically calculated the spatial and temporal evolution of the optical field as it propagated through the hydrogel, whose index of refraction was changing. Consistent with experiments, the model accurately captured the self-trapping dynamics and efficiency when using the single or double laser beams.

“This paper marks an interesting step forward that is indicative of the potential of one disruptive technology,” says John Sheridan, a professor of electrical and electronic engineering at the University College of Dublin, who was not involved in the research. “Technologies like this will provide core hardware components enabling the three-dimensional, all-optical connection and switching hardware needed for ‘Internet of things’ data integration and the 5G/6G telecommunications systems of the future.”

Currently, the speed of the waveguide formation and switching happens in seconds, though, rather than the nanoseconds typical of optoelectronic switches. So the researchers plan to investigate what parameters are slowing down the process and how to change them. For example, they will explore making the hydrogel more flexible to give the chromophores greater freedom to undergo isomerization in hopes of eliciting a faster response. They will also look at different types of isomerizable chromophores.

However, Saravanamuttu emphasizes they are not trying to replace digital computers that use conventional electronics, so speed may not be critical. Other potential applications include autonomous stimuli-responsive soft robotic systems for drug delivery or dynamic optics.

“This is particularly exciting because we see it as a material that can reciprocally interact with an environmental stimulus. It isn’t just turned on and off, but it actually changes its behavior in a dynamic way,” she says.

Read the article in Proceedings of the National Academy of Sciences

Figure caption: (a) Schematic illustration of the experimental setup used to probe laser self-trapping due to photoinduced local contraction of the hydrogel. A 532 nm laser beam is focused onto the entrance face of the hydrogel, propagated through the material, and imaged onto a CCD camera. (b) Illustration of beam-induced contraction of the hydrogel when continuously irradiated with a 532 nm laser beam. Credit: Saravanamuttu group, McMaster University, Aizenberg Group, Harvard University, Balazs Group, University of Pittsburgh; PNAS doi.org/10.1073/pnas.1902872117

This is a reposting of my MRS news brief, courtesy of the Materials Research Society.

Floppy vibration modes explain negative thermal expansion in solids

Animation showing how solid crystals of ScF3 shrink upon heating. While the bonds between scandium (green) and fluorine (blue) remain relatively rigid, the fluorine atoms along the sides of the cubic crystals oscillate independently, resulting in a wide range of distances between neighboring fluorine atoms. The higher the temperature, the greater the buckling in the sides of the crystals leading to the overall contraction (negative thermal expansion) effect. Credit: Brookhaven National Laboratory

Matching the thermal expansion values of materials in contact is essential when manufacturing precision tools, engines, and medical devices. For example, a dental filling would cause a toothache if it expanded a different amount than the surrounding tooth when drinking a hot beverage. Fillings are therefore comprised of a composite of materials with positive and negative thermal expansion, creating an overall expansion tailored to the tooth enamel.

The underlying mechanisms of why crystalline materials with negative thermal expansion (NTE) shrink when heated have been a matter of scientific debate. Now, a multi-institutional research team led by Igor Zaliznyak, a physicist at Brookhaven National Laboratory, believes it has the answer.

As recently reported in Science Advances, the scientists measured the distance between atoms in scandium trifluoride powder, a cubic NTE material—at temperatures ranging from 2 K to 1099 K—using total neutron diffraction. The research team determined the probability that two particular atomic species would be found at a given distance. They studied scandium trifluoride because it has a simple atomic structure in which each scandium atom is surrounded by an octahedron of fluorine atoms. According to the prevailing rigid-unit-mode (RUM) theory, each fluorine octahedron should vibrate and move as a rigid unit when heated — but that is not what they observed.

“We found that the distances between scandium and fluorine were pretty rigidly-defined until a temperature of about 700 K, but the distances between the nearest-neighbor fluorines became ill-defined at temperatures above 300 K,” says Zaliznyak. “Their probability distributions became very broad, which is basically a direct manifestation of the fact that the shape of the octahedron is not preserved. If the fluorine octahedral had been rigid, the fluorine-fluorine distance would have been as well defined as scandium-fluorine.”

With the help of high school researcher David Wendt and condensed matter theorist Alexei Tkachenko, Zaliznyak developed a simple model to explain these experimental results. The team went back to the basics—the fundamental laws of physics.

“When we removed the ill-controlled constraint that there must be these rigid units, then we could explain the fundamental interactions that govern the atomic positions in the [ScF3] solid using just Coulomb interactions.”

The team developed a negative thermal expansion model that treats each Sc-F bond as a rigid monomer link and the entire ScF3 crystal structure as a floppy, under-constrained network of freely jointed monomers. Each scandium ion is constrained by rigid bonds in all three directions, whereas each fluorine ion is free to vibrate and displace orthogonally to its Sc-F bonds. This is a direct three-dimensional analogy of the well-established behavior of chainlike polymers. And their simple theory agreed remarkably well with their experiments, accurately predicting the distribution of distances between the nearest-neighbor fluorine pairs for all temperatures where NTE was observed.   

“Basically we figured out how these ceramic materials contract on warming and how to make a simple calculation that describes this phenomenon,” Zaliznyak says.

Angus Wilkinson, an expert on negative thermal expansion materials at the Georgia Institute of Technology who is not involved in the project, agrees that Zaliznyak’s work will change the way people think about negative thermal expansion in solids.

“While the RUM picture of NTE has been questioned for some time, the experimental data in this paper, along with the floppy network (FN) analysis, provide a compelling alternative view,” says Wilkinson. “I very much like the way the FN approach is applicable to both soft matter systems and crystalline materials. The floppy network analysis is novel and gives gratifyingly good agreement with a wide variety of experimental data.”

According to Zaliznyak, the next major step of their work will be to study more complex materials that exhibit NTE behavior now that they know what to look for.

Read the article in Science Advances.

This is a reposting of my news brief, courtesy of MRS Bulletin.