Computers Math

Professor Lee Jong-won’s team of the Department of Energy Science and Engineering at DGIST (President: Kuk Yang), together with Professor Moon Jang-hyeok’s team from the Chung-Ang University, announced the development of solid electrolytes with enhanced atmospheric stability on Wednesday, December 7.
Lithium ion batteries are widely used as energy storage systems for electronic products and electric vehicles. However, since it is vulnerable to ignition as it is manufactured mainly with flammable organic liquid electrolytes, safety issues have been continuously raised as of late.
On the other hand, oxide-based solid electrolytes have the advantage of having high thermal stability and physically preventing the growth of lithium dendrites. Among them, Li7La3Zr2O12 (hereinafter, “LLZO”) electrolyte is considered as a next-generation electrolyte due to its excellent lithium ion conductivity.
Despite these advantages, LLZO electrolyte has a problem — Lithium carbonate forms on the surface due to reaction with moisture and carbon dioxide when exposed to the atmosphere. Lithium carbonate is formed on the surface and then grows along the grain boundaries penetrating into the solid electrolyte and disturb the transfer of lithium ions, which lowers the lithium ion conductivity of the LLZO solid electrolyte.
The research team improved the atmospheric stability of the LLZO electrolyte through the hetero-elemental doping of gallium and tantalum, i.e. by adding gallium and tantalum to pure LLZO electrolytes. In particular, it was verified that ‘LiGaO2,’ a third material formed through the addition of gallium, suppresses the surface adsorption of moisture and carbon dioxide, and promotes the growth of particles during thermal treatment, thus preventing growth of lithium carbonate through grain boundaries and maintaining the lithium ion conduction properties of LLZO electrolytes.
As a result, it was empirically verified that lithium ion conductivity is maintained even when stored for a long time in the air, and stable performance was maintained even after repeated lithium electrodeposition/desorption.
DGIST Department of Energy Science and Engineering Professor Jong-Won Lee said, “I expect the solid electrolyte design concept presented by this research team to be helpful in developing high-performance/high-safety all-solid-state batteries incorporating solid electrolytes, which are stable in the atmosphere and have high lithium ion conductivity.”
Meanwhile, Jung Woo-young in the DGIST Master-Doctor Combined Program participated in this research as the lead author, and the research results were published online on November 2 in Energy Storage Materials, an international journal specializing in energy. In addition, it was carried out with support from the National Research Foundation of Korea’s ‘Nano and Materials Technology Development Project’ and ‘Engineering Research Center Project.’
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Materials provided by DGIST (Daegu Gyeongbuk Institute of Science and Technology). Note: Content may be edited for style and length. More

DGIST (President: Kuk Yang) Department of Electrical Engineering and Computer Science Professor Hwang Jae-yoon’s team developed a ‘deep learning-based ultrasound hologram generation framework’ technology that can freely configure the form of focused ultrasound in real time based on holograms. It is expected to be used as a basic technology in the field of brain stimulation and treatment that requires precision in the future.
Ultrasound is a safe technology even used for prenatal examination. Since it can stimulate deep areas without surgery, ultrasound methods for brain stimulation and treatment have recently been studied, and results that ultrasound brain stimulation have actually improved diseases, such as Alzheimer’s disease, depression, and pain, have been published.
However, the problem is that it is difficult to selectively stimulate related areas of the brain in which several areas interact with each other at the same time because the current technology focuses ultrasound into a single small point or a large circle for stimulation. To solve this problem, a technology capable of freely focusing ultrasound on a desired area using the hologram principle had been proposed, but has limitations, such as low accuracy and long calculation time to generate a hologram.
DGIST Professor Hwang Jae-yoon’s team proposed a deep learning-based learning framework that can embody free and accurate ultrasound focusing in real time by learning to generate ultrasound holograms to overcome the limitations. As a result, Professor Hwang’s team demonstrated that it was possible to focus ultrasound into the desired form more accurately in a hologram creation time close to real time, and maximum 400 times faster than the existing ultrasound hologram generation algorithm method.
The deep learning-based learning framework proposed by the research team learns to generate ultrasonic holograms through self-supervised learning. Self-supervised learning is a method of learning to find the answer by finding a rule on its own for data with no answer. The research team proposed a methodology for learning to generate ultrasonic hologram, a deep learning network optimized for ultrasonic hologram generation, and a new loss function, while proving the validity and excellence of each component through simulations and actual experiments.
DGIST Department of Electrical Engineering and Computer Science Professor Hwang Jae-yoon said, “We applied deep learning technology to ultrasound holograms proposed relatively recently. As a result, we developed a technology that can freely, quickly and accurately generate and change the form of ultrasound beams,” and added, “We hope that the results of this research are used in patient-specific precision brain stimulation technology and general ultrasound fields (ultrasound imaging, thermal therapy, etc.).”
Meanwhile, this research was carried out with the Ministry of Science and ICT’s Four Major Institutes of Science and Technology Support Program. Researcher Lee Moon-hwan of DGIST Information and Communication Engineering Research Center, Ph.D. students Ryu Ha-min and Yoon Sang-yeon of the Department of Electrical Engineering and Computer Science, and GIST Professor Kim Tae’s team. The research results were published as a cover paper in the December edition of IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, an international academic journal in the related field. More

Biofilms form when microorganisms such as certain types of bacteria adhere to the surface of objects in a moist environment and begin to reproduce resulting in the excretion of a slimy glue-like substance.
These biofilms aren’t just unpleasant and unappealing however, they can be seriously troublesome. For example, in the medical field, the formation of biofilm can reduce the effectiveness of antibiotic treatments. The key to understanding biomass formation lies in understanding how bacteria behave en masse.
A new paper in EPJE by Heinrich-Heine-Universität, Düsseldorf, Germany, researcher Davide Breoni and his co-authors presents a mathematical model for the motion of bacteria that includes cell division and death, the basic ingredients of the cell cycle.
The team developed a mathematical model of bacterial movement in process creating a link between statistical physics and biophysics.
“Our new model belongs to a class of models for ‘active matter’ that currently encounter a lot of interest in statistical physics,” Breoni says. “This field studies the collective properties of particle systems that have their own energy source — bacteria are an exemplary case.”
The model devised by the team delivered a surprise by suggesting that when it comes to movement bacteria can act as a unit.
“In the course of our investigation, we found out that the model predicts that the formation of bacterial colonies can occur through the build-up of travelling waves, concentrated ‘packages’ of bacteria,” Breoni adds. “We did not expect this to arise from such a simple model as ours.”
He believes that the results should be interesting to the general public who may be aware of bacterial colonies, but not know how they move in a collective way.
Breoni concludes by pointing out this is a very simple model suggesting how the research could proceed from here. “We could try to make the model more realistic and confront the results to experiment to test its predictions,” he says. “On the other hand, this research is very much curiosity-driven and results from intense discussions among the researchers — an approach we’d like to maintain so we can continue to surprise ourselves with our findings.”
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Marvel at the tiny nanoscale structures emerging from research labs at Duke University and Arizona State University, and it’s easy to imagine you’re browsing a catalog of the world’s smallest pottery.
A new paper reveals some of the teams’ creations: itty-bitty vases, bowls, and hollow spheres, one hidden inside the other, like housewares for a Russian nesting doll.
But instead of making them from wood or clay, the researchers designed these objects out of threadlike molecules of DNA, bent and folded into complex three-dimensional objects with nanometer precision.
These creations demonstrate the possibilities of a new open-source software program developed by Duke Ph.D. student Dan Fu with his adviser John Reif. Described December 23 in the journal Science Advances, the software lets users take drawings or digital models of rounded shapes and turn them into 3D structures made of DNA.
The DNA nanostructures were assembled and imaged by co-authors Raghu Pradeep Narayanan and Abhay Prasad in professor Hao Yan’s lab at Arizona State. Each tiny hollow object is no more than two millionths of an inch across. More than 50,000 of them could fit on the head of a pin.
But the researchers say these are more than mere nano-sculptures. The software could allow researchers to create tiny containers to deliver drugs, or molds for casting metal nanoparticles with specific shapes for solar cells, medical imaging and other applications. More

A magical display that projects holographic images that change when in contact with water has been developed. This new technology increases the possibility of commercialization as it can infinitely imprint holographic images.
A POSTECH research team led by Professor Junsuk Rho (Department of Mechanical Engineering and Department of Chemical Engineering) and Ph.D. candidates Byoungsu Ko, Younghwan Yang, Jaekyung Kim, and Dr. Trevon Badloe has developed a technology for a humidity-responsive display that changes in brightness and color depending on the degree of humidity.
The team first successfully realized holographic images with tunable brightness using polyvinyl alcohol (PVA). This material is so flexible that it is usually used for liquid glue or slime and one of its distinctive properties is that it swells as humidity increases. A holographic image that is clear at a low degree of humidity gradually becomes unclear as humidity increases.
The team additionally developed a display on which structural colors can be discretionally tuned. A blue image at low humidity turns red as humidity increases. If humidity is fine-tuned, all RGB colors may be expressed, in addition to the two colors.
This study also draws attention to the team’s success in using the single-step nanoimprinting technique to print the images. It is notable that images can be vividly expressed even on a flexible substrate. In addition, as a single pixel of this display — which reaches 700 nm (1nm = 1/1 billion m) — is smaller than those of currently commercialized displays, it is anticipated to become the core technology for nanostructured displays.
The findings from the study have received significant attention as the newly developed technology may be employed to security labels for authentication against counterfeits, including food items like whisky, currency bills, or passports. The team has been working with Korea Minting and Security Printing Corporation (KOMSCO) to apply the optics-based future security technology to actual products. Subsequently, this technology is expected to be applied to the development of a hydrogel macromolecule-based display that responds to external stimuli such as heat, acidity (pH), and fine-dust pollution.
These findings on the brightness and color tunability of holographic images were published in the international journals Nature Communications and Advanced Science, respectively.
This research was supported by the Samsung Science & Technology Foundation, the Pioneer Program of Future Technology of the National Research Foundation under the Ministry of Science and ICT and POSCO-POSTECH-RIST Convergence Research Center program funded by POSCO.
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Ensuring manufactured goods and components have not been copied and replaced illegally by counterfeited goods is a high-priority concern of the manufacturing and defense industries in the U.S. and around the world.
A potential solution would hold wide-reaching impacts and implications in various areas ranging from enhancing biomedical implants to protecting national defense assets.
Texas A&M University researchers have developed a method of imprinting a hidden magnetic tag, encoded with authentication information, within manufactured hardware during the part fabrication process. The revolutionary process holds the potential to expose counterfeit goods more easily by replacing physical tags — such as barcodes or quick response (QR) codes — with these hidden magnetic tags, which serve as permanent and unique identifiers.
The project, titled “Embedded Information in Additively Manufactured Metals via Composition Gradients for Anti-Counterfeiting and Supply Chain Traceability,” is a faculty partner project supported by the SecureAmerica Institute. It includes researchers from the Department of Materials Science and Engineering and the J. Mike Walker ’66 Department of Mechanical Engineering at Texas A&M. The team recently published its research in the journal Additive Manufacturing.
The faculty investigators on the project include Ibrahim Karaman, Chevron Professor I and department head of the materials science and engineering department; Raymundo Arroyave, professor of materials science and engineering and Segers Family Dean’s Excellence Professor; and Richard Malak, associate professor of mechanical engineering and Gulf Oil/Thomas A. Dietz Career Development Professor. In addition to the faculty, Daniel Salas Mula, a researcher with the Texas A&M Engineering Experiment Station, and doctoral student Deniz Ebeperi — both members of Karaman’s research group — have worked on the project. The team has also collaborated with Jitesh Panchal, professor of mechanical engineering at Purdue University.
Ensuring security and reliable authentication in manufacturing is a critical national concern, with the U.S. investing billions of dollars in manufacturing. Without such a method readily available, it can be nearly impossible to differentiate an authentic part or component from its counterfeit copy.”The issue is that when I come up with an idea, device or part, it is very easy for others to copy and even fabricate it much more cheaply — though maybe at a lower quality,” Karaman said. “Sometimes they even put the same brand name, so how do you make sure that item isn’t yours? [The embedded magnetic tag] gives us an opportunity and a new tool to make sure that we can protect our defense and manufacturing industries.”
The team is implementing metal additive manufacturing techniques to accomplish its goal of successfully embedding readable magnetic tags into metal parts without compromising on performance or longevity. Researchers used 3D printing to embed these magnetic tags below the surface into nonmagnetic steel hardware. More

Much of modern electronic and computing technology is based on one idea: add chemical impurities, or defects, to semiconductors to change their ability to conduct electricity. These altered materials are then combined in different ways to produce the devices that form the basis for digital computing, transistors, and diodes. Indeed, some quantum information technologies are based on a similar principle: adding defects and specific atoms within materials can produce qubits, the fundamental information storage units of quantum computing.
Gaurav Bahl, professor of mechanical science and engineering at the University of Illinois Urbana-Champaign and member of the Illinois Quantum Information Sciences and Technology Center, is exploring how special non-linear properties in engineered materials can achieve similar functionalities without the need to add intentional defects. As his research group reports in their article “Self-Induced Dirac Boundary State and Digitization in a Nonlinear Resonator Chain” published in Physical Review Letters, a metamaterial can change its functionality on its own depending on the power level of the input.
A metamaterial is an artificial system that replicates the behavior of real materials made of natural atoms. The researchers constructed a whose behavior is analogous to a special kind of semiconductor called a Dirac material. It consisted of a chain of magnetic-mechanical resonators, where the magnetic interactions acted like bonds between atoms in a one-dimensional crystal. When any of these “atoms” was mechanically excited, that is, was made to move periodically, the excitation spread to the rest of the crystal, just like electrons injected into a semiconductor.
After demonstrating that a completely uniform Dirac metamaterial does not allow mechanical excitations to pass through (just like electrons are forbidden from flowing through insulating semiconductor), the researchers introduced a specific set of nonlinearities into the system. This new property added sensitivity to the level of the mechanical excitation and could subtly change the resonance energy of the magneto-mechanical atoms. With the right choice of nonlinearity, the researchers observed a sharp transition from insulating to conducting behavior depending on how strong an input was provided.
This intriguing behavior resulted from the spontaneous appearance of a new boundary where the effective mass of the mechanical excitation, an invisible internal property of Dirac materials, underwent a change of sign depending on the level of the excitation. The researchers were surprised to find that this boundary was accompanied by a new state that “popped in” at the boundary and allowed input energy to transmit through the material. This effect was very similar to how a defect atom acts within a semiconductor
“In photonics and electronics,” Bahl said, “nonlinear properties like this could be engineered to form the foundation of new computational systems that don’t rely on the conventional semiconductor approach.”
Whenever we add defect states and special atoms, we interrupt the uniformity of the material, which can lead to other undesirable effects. However, materials in which a defect state can be formed on demand through an invisible property, such as the Dirac mass used in this work, has profound implications for quantum information systems where it promises qubits that can be produced dynamically where they are needed. The next challenge is finding or synthesizing real materials based on natural atoms that can replicate this effect.
The experiments were performed by Physics graduate student Gengming Liu in collaboration with postdoc Dr. Jiho Noh and MechSE graduate student Jianing Zhao
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Materials provided by University of Illinois Grainger College of Engineering. Original written by Michael O’Boyle. Note: Content may be edited for style and length. More

Carnegie Mellon University’s Yongxin (Leon) Zhao and the Chinese University of Hong Kong’s Shih-Chi Chen have a big idea for manufacturing nanodevices.
Zhao’s Biophotonics Lab develops novel techniques to study biological and pathological processes in cells and tissues. Through a process called expansion microscopy, the lab works to advance techniques to proportionally enlarge microscopic samples embedded in a hydrogel, allowing researchers to be able to view fine details without upgrading their microscopes.
In 2019, an inspiring conversation with Shih-Chi Chen, who was visiting Carnegie Mellon as an invited speaker and is a professor at the Chinese University of Hong Kong’s Department of Mechanical and Automation Engineering, sparked a collaboration between the two researchers. They thought they could use their combined expertise to find novel solutions for the long-standing challenge in microfabrication: developing ways to reduce the size of printable nanodevices to as small as 10s of nanometers or several atoms thick.
Their solution is the opposite of expansion microscopy: create the 3D pattern of a material in hydrogel and shrink it for nanoscale resolution.
“Shih-Chi is known for inventing the ultrafast two-photon lithography system,” said Zhao, the Eberly Family Career Development Associate Professor of Biological Sciences. “We met during his visit to Carnegie Mellon and decided to combine our techniques and expertise to pursue this radical idea.”
The results of the collaboration open new doors for designing sophisticated nanodevices and are published in the journal Science. More