Aurelia Butler

A University of Minnesota Twin Cities-led team of scientists and engineers has developed a new method for making thin films of perovskite oxide semiconductors, a class of “smart” materials with unique properties that can change in response to stimuli like light, magnetic fields, or electric fields.
The discovery will allow researchers to harness these properties and even combine them with other emerging nano-scale materials to make better devices such as sensors, smart textiles, and flexible electronics.
The paper is published in Science Advances.
Producing materials in thin-film form makes them easier to integrate into smaller components for electronic devices. Many thin films are made using a technique called epitaxy, which consists of placing atoms of a material on a substrate, or a template of sorts, to create a thin sheet of material, one atomic layer at a time. However, most thin films created via epitaxy are “stuck” on their host substrate, limiting their uses. If the thin film is detached from the substrate to become a freestanding membrane, it becomes much more functional.
The University of Minnesota-led team has found a new way to successfully create a membrane of a particular metal oxide — strontium titanate — and their method circumvents several issues that have plagued the synthesis of freestanding metal oxide films in the past.
“We have created a process where we can make a freestanding membrane of virtually any oxide material, exfoliate it, and then transfer it onto any subject of interest we want,” said Bharat Jalan, a senior author on the paper and a professor and Shell Chair in the University of Minnesota Department of Chemical Engineering and Materials Science. “Now, we can benefit from the functionality of these materials by combining them with other nano-scale materials, which would enable a wide range of highly functional, highly efficient devices.”
Making freestanding membranes of “smart” oxide materials is challenging because the atoms are bonded in all three dimensions, unlike in a two-dimensional material, such as graphene. One method of making membranes in oxide materials is using a technique called remote epitaxy, which uses a layer of graphene as an intermediary between the substrate and the thin-film material.

This approach allows the thin-film oxide material to form a thin film and be peeled off, like a piece of tape, from the substrate, creating a freestanding membrane. However, the biggest barrier to using this method with metal oxides is that the oxygen in the material oxidizes the graphene on contact, ruining the sample.
Using hybrid molecular beam epitaxy, a technique pioneered by Jalan’s lab at the University of Minnesota, the researchers were able to get around this issue by using titanium that was already bonded to oxygen. Plus, their method allows for automatic stoichiometric control, meaning they can automatically control the composition.
“We showed for the first time, and conclusively by doing several experiments, that we have a new method which allows us to make complex oxide while ensuring that graphene is not oxidized. That’s a major milestone in synthesis science,” Jalan said. “And, we now have a way to make these complex oxide membranes with an automatic stoichiometric control. No one has been able to do that.”
The materials scientists on Jalan’s team worked closely with engineering researchers in University of Minnesota Department of Electrical and Computer Engineering Professor Steven Koester’s lab, which focuses on making 2D materials.
“These complex oxides are a broad class of materials that have a lot of really important innate functions to them,” said Koester, also a senior author of the study and the director of the Minnesota Nano Center at the University of Minnesota Twin Cities. “Now, we can think about using them to make extremely small transistors for electronic devices, and in a wide array of other applications including flexible sensors, smart textiles, and non-volatile memories.”
The research was funded by the U.S. Department of Energy, the Air Force Office of Scientific Research, and the National Science Foundation.
In addition to Jalan and Koester, the research team included University of Minnesota Department of Chemical Engineering and Materials Science researchers Hyojin Yoon, Tristan Truttmann, Fengdeng Liu, and Sooho Choo; University of Minnesota Department of Electrical and Computer Engineering researcher Qun Su; Pacific Northwest National Laboratory researchers Bethany Matthews, Mark Bowden, Steven Spurgeon, and Scott Chambers; and University of Wisconsin-Madison researchers Vivek Saraswat, Sebastian Manzo, Michael Arnold, and Jason Kawasaki. More

A team of engineers and neuroscientists has demonstrated for the first time that human brain organoids implanted in mice have established functional connectivity to the animals’ cortex and responded to external sensory stimuli. The implanted organoids reacted to visual stimuli in the same way as surrounding tissues, an observation that researchers were able to make in real time over several months thanks to an innovative experimental setup that combines transparent graphene microelectrode arrays and two-photon imaging.
The team, led by Duygu Kuzum, a faculty member in the University of California San Diego Department of Electrical and Computer Engineering, details their findings in the Dec. 26 issue of the journal Nature Communications. Kuzum’s team collaborated with researchers from Anna Devor’s lab at Boston University; Alysson R. Muotri’s lab at UC San Diego; and Fred H. Gage’s lab at the Salk Institute.
Human cortical organoids are derived from human induced pluripotent stem cells, which are usually derived themselves from skin cells. These brain organoids have recently emerged as promising models to study the development of the human brain, as well as a range of neurological conditions.
But until now, no research team had been able to demonstrate that human brain organoids implanted in the mouse cortex were able to share the same functional properties and react to stimuli in the same way. This is because the technologies used to record brain function are limited, and are generally unable to record activity that lasts just a few milliseconds.
The UC San Diego-led team was able to solve this problem by developing experiments that combine microelectrode arrays made from transparent graphene, and two-photon imaging, a microscopy technique that can image living tissue up to one millimeter in thickness.
“No other study has been able to record optically and electrically at the same time,” said Madison Wilson, the paper’s first author and a Ph.D. student in Kuzum’s research group at UC San Diego. “Our experiments reveal that visual stimuli evoke electrophysiological responses in the organoids, matching the responses from the surrounding cortex.”
The researchers hope that this combination of innovative neural recording technologies to study organoids will serve as a unique platform to comprehensively evaluate organoids as models for brain development and disease, and investigate their use as neural prosthetics to restore function to lost, degenerated or damaged brain regions. More

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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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