Aurelia Butler

Gene therapies have the potential to treat neurological disorders like Alzheimer’s and Parkinson’s diseases, but they face a common barrier — the blood-brain barrier. Now, researchers at the University of Wisconsin-Madison have developed a way to move therapies across the brain’s protective membrane to deliver brain-wide therapy with a range of biological medications and treatments.
“There is no cure yet for many devastating brain disorders,” says Shaoqin “Sarah” Gong, UW-Madison professor of ophthalmology and visual sciences and biomedical engineering and researcher at the Wisconsin Institute for Discovery. “Innovative brain-targeted delivery strategies may change that by enabling noninvasive, safe and efficient delivery of CRISPR genome editors that could, in turn, lead to genome-editing therapies for these diseases.”
CRISPR is a molecular toolkit for editing genes (for example, to correct mutations that may cause disease), but the toolkit is only useful if it can get through security to the job site. The blood-brain barrier is a membrane that selectively controls access to the brain, screening out toxins and pathogens that may be present in the bloodstream. Unfortunately, the barrier bars some beneficial treatments, like certain vaccines and gene therapy packages, from reaching their targets because in lumps them in with hostile invaders.
Injecting treatments directly into the brain is one way to get around the blood-brain barrier, but it’s an invasive procedure that provides access only to nearby brain tissue.
“The promise of brain gene therapy and genome-editing therapy relies on the safe and efficient delivery of nucleic acids and genome editors to the whole brain,” Gong says.
In a study recently published in the journal Advanced Materials, Gong and her lab members, including postdoctoral researcher and first author of the study Yuyuan Wang, describe a new family of nano-scale capsules made of silica that can carry genome-editing tools into many organs around the body and then harmlessly dissolve.
By modifying the surfaces of the silica nanocapsules with glucose and an amino acid fragment derived from the rabies virus, the researchers found the nanocapsules could efficiently pass through the blood-brain barrier to achieve brain-wide gene editing in mice. In their study, the researchers demonstrated the capability of the silica nanocapsule’s CRISPR cargo to successfully edit genes in the brains of mice, such as one related to Alzheimer’s disease called amyloid precursor protein gene.
Because the nanocapsules can be administered repeatedly and intravenously, they can achieve higher therapeutic efficacy without risking more localized and invasive methods.
The researchers plan to further optimize the silica nanocapsules’ brain-targeting capabilities and evaluate their usefulness for the treatment of various brain disorders. This unique technology is also being investigated for the delivery of biologics to the eyes, liver and lungs, which can lead to new gene therapies for other types of disorders. More

Synthetic populations are computer-generated groups of people that are designed to look like real populations. They are built using public census information about people’s characteristics, such as their age, gender, and job, alongside statistical algorithms that help put it all together. Their main application is for conducting so-called social simulations to assess different possible solutions to social problems, such as transportation, health issues, and housing. During the COVID-19 pandemic, for example, scientists in many places around the world conducted social simulations to estimate the number of cases in each country.
In Japan, researchers have been carrying out such simulations using supercomputers under the COVID-19 AI & Simulation Project led by the Cabinet Secretariat of the Japanese government since 2020. They were given significant consideration when deciding various political measures, such as PCR testing policies, immigration limits, domestic tourism support, vaccination programs, and so on. These simulations were possible thanks to a synthetic population which was prepared and updated under the Joint Usage/Research Center for Interdisciplinary Large-scale Information Infrastructures (JHPCN) project, since 2017.
However, this Japanese synthetic population had a significant limitation — even though a home address was one of the attributes assigned to each individual, their workplace location was not. As a result, this synthetic population was more accurate at representing the night-time distribution of people, but not their day-time distribution, or the relationship between both.
To tackle this problem, a trio of Japanese researchers including Assistant Professor Takuya Harada of Shibaura Institute of Technology, as well as Dr. Tadahiko Murata and Mr. Daiki Iwase of the Faculty of Informatics at Kansai University, recently devised a method to assign a workplace attribute to each worker in synthetic populations. Their study was published in IEEE Transactions on Computational Social Systems and was supported by both JHPCN and the Japan Science and Technology Agency (JST).
The main challenge the researchers had to overcome was the lack of statistical information linking home and workplace locations for people. In Japan, only local governments whose area has over 200,000 residents release complete origin-destination-industry (ODI) statistics, which provide details about the movement of workers as well as their industry type (like retail, construction, or manufacturing). For cities, towns, or villages with less than 200,000 residents, the available ODI data is less specific, and only tells whether the person works in the same city, in another city within the same prefecture, or in another city in a different prefecture. Unfortunately, approximately 48% of workers in Japan reside in cities with less than 200,000 residents.
Thus, the research team combined available ODI data with origin-destination (OD) data and developed an innovative workplace assignment method that works for all cities, towns, and villages in Japan. To test whether their method was designed properly, they used it to assign workplaces to people in cities with more than 200,000 residents and compared the results with the available complete ODI data. For the city of Takatsuki in the Osaka prefecture, which the researchers showcased as an example in their paper, the proposed method could assign the correct cities as workplaces for 88.2% of workers.
The possible applications for detailed social simulations using synthetic populations are manyfold, as Professor Murata of Kansai University remarks: “Real-scale social simulations can be used for estimating the efficiency of urban developments, including housing and transportation projects, as well as the influence of social programs conducted by national or local governments. They can also be employed for rescue and relief programs when facing disasters such as earthquakes, tsunamis, floods, typhoons, and pandemics.” Put simply, social simulations can help decisionmakers accurately image various possible futures.
Another important aspect of synthetic populations is that they are free from data privacy concerns. “Synthetic populations are a secure technology because no private information is used,” explains Assistant Professor Harada, “Because we synthesize multiple sets of populations that have the same statistical characteristics, third parties cannot identify whether real information is included or not.” Worth noting, this study marks the world’s first synthetic populations with workplace information that are publicly released for engineers and researchers.
The research team is already working on using their newfound workplace assignment method to estimate the day-time population distribution throughout all of Japan. More

As buzz grows ever louder over the future of quantum, researchers everywhere are working overtime to discover how best to unlock the promise of super-positioned, entangled, tunneling or otherwise ready-for-primetime quantum particles, the ability of which to occur in two states at once could vastly expand power and efficiency in many applications.
Developmentally, however, quantum devices today are “about where the computer was in the 1950s,” which it is to say, the very beginning. That’s according to Kamyar Parto, a sixth-year Ph.D. student in the UC Santa Barbara lab of Galan Moody, an expert in quantum photonics and an assistant professor of electrical and computer engineering. Parto is co-lead author of a paper published in the journal Nano Letters, describing a key advance: the development of a kind of on-chip “factory” for producing a steady, fast stream of single photons, essential to enabling photonic-based quantum technologies.
In the early stages of computer development, Parto explained, “Researchers had just made the transistor, and they had ideas for how to make a digital switch, but the platform was kind of weak. Different groups developed different platforms, and eventually, everyone converged on CMOS (complementary metal-oxide semiconductor). Then, we had the huge explosion around semiconductors.
“Quantum technology is in a similar place — we have the idea and a sense of what we could do with it, and there are many competing platforms, but no clear winner yet,” he continued. “You have superconducting qubits, spin qubits in silicon, electrostatic spin qubits and ion-trap-based quantum computers. Microsoft is trying to do topologically protected qubits, and in the Moody Lab, we’re working on quantum photonics.”
Parto predicts that the winning platform will be a combination of different platforms, given that each is powerful but also has limitations. “For instance, it’s very easy to transfer information using quantum photonics, because light likes to move,” he said. “A spin qubit, however, makes it easier to store information and do some local ‘stuff’ on it, but you can’t move that data around. So, why don’t we try to use photonics to transfer the data from the platform that stores it better, and then transform it again to another format once it’s there?”
Qubits, those strangely behaving drivers of quantum technologies, are, of course, different from classical bits, which can exist in only a single state of zero or one. Qubits can be both one and zero simultaneously. In the realm of photonics, Parto said, a single photon can be made both to exist (state one) and not to exist (state zero).

That is because a single photon constitutes what is called a two-level system, meaning that it can exist in a zero state, a one state, or any combination, such as 50% one and 50% zero, or maybe 80% one and 20% zero. This can be done routinely in the Moody group. The challenge is to generate and collect single photons with very high efficiency, such as by routing them on a chip using waveguides. Waveguides do exactly what their name suggests, guiding the light where it needs to go, much as wires guide electricity.
Parto explained: “If we put these single photons into many different waveguides — a thousand single photons on each waveguide — and we sort of choreograph how the photons travel along the waveguides on the chip, we can do a quantum computation.”
While it is relatively simple to use waveguides to route photons on chip, isolating a single photon is not easy, and setting up a system that produces billions of them rapidly and efficiently is much harder. The new paper describes a technique that employs a peculiar phenomenon to generate single photons with an efficiency that is much greater than has been achieved previously.
“The work is about amplifying the generation of these single photons so that they become useful to actual applications,” Parto said. “The breakthrough described in this paper is that we can now generate the single photons reliably at room temperature in a way that lends itself to (the mass-production process of) CMOS.”
There are various ways to go about generating single photons, but Parto and his colleagues are doing it by using defects in certain two-dimensional (2D) semiconductor materials, which are only one atom thick, essentially removing a bit of the material to create a defect.

“If you shine light (generated by a laser) onto the right kind of defect, the material will respond by emitting single photons,” Parto said, adding, “The defect in the material acts as what is called a rate-limiting state, which allows it to behave like a factory for pushing out single photons, one at a time.” One photon might be produced as often as every three to five nanoseconds, but the researchers aren’t yet sure of the rate, and Parto, who earned his Ph.D. on the topic of engineering such defects, says that the current rate could be much slower.
A big advantage of 2D materials is that they lend themselves to having defects engineered into them at specific locations. Further, Parto said, “The materials are so thin that you can pick them up and put them on any other material without being constrained by the lattice geometry of a 3D crystal material. That makes the 2D material very easy to integrate, a capability we show in this paper.”
To make a useful device, the defect on the 2D material must be placed in the waveguides with extreme precision. “There is one point on the material that produces light from a defect,” Parto noted, “and we need to get that single photon into a waveguide.”
Researchers try to do that in a couple of ways, for instance, by putting the material on the waveguide and then looking for an existing single defect, but even if the defect is precisely aligned and in exactly the right position, the extraction efficiency will be only 20% to 30%. That is because the single defect can emit only at one specific rate, and some of the light is emitted at oblique angles, rather than directly along the path to the waveguide. The theoretical upper limit of that design is only 40%, but making a useful device for quantum-information applications requires 99.99% extraction efficiency.
“The light from a defect inherently shines everywhere, but we prefer that it shine into these waveguides,” Parto explained. “We have two choices. If you put waveguides on top of the defect, maybe ten to fifteen percent of the light would go into the waveguides. That’s not enough. But there is a physics phenomenon, called the Purcell effect, that we can utilize to boost this efficiency and direct more of the light into the waveguide. You do that by placing the defect inside an optical cavity — in our case it’s in the shape of a micro-ring resonator, which is one of the only cavities that allows you to couple light into and out of a waveguide.
“If the cavity is small enough,” he added, “it will squeeze out the vacuum fluctuations of the electromagnetic field, and those fluctuations are what cause the spontaneous emission of photons from the defect into a mode of light. By squeezing that quantum fluctuation into a cavity of finite volume, the fluctuation over the defect is increased, causing it to emit light preferentially into the ring, where it accelerates and becomes brighter, thus increasing the extraction efficiency.”
In experiments using the micro-ring resonator that were done for this paper, the team achieved extraction efficiency of 46%, which is an order-of-magnitude increase over prior reports.
“We’re really encouraged by these results, because single-photon emitters in 2D materials address some of the outstanding challenges facing other materials in terms of scalability and manufacturability,” said Moody. “In the near term, we’ll explore using them for a few different applications in quantum communications, but in the long term, our goal is to continue to develop this platform for quantum computing and networking.”
To do that, the group needs to improve their efficiency to better than 99%, and achieving that will require higher-quality nitride resonator rings. “To enhance efficiency, you need to smooth out the ring when you carve it out of the silicon nitride film,” Parto explained. “However, if the material itself is not fully crystalline, even if you try to smooth it at the atomic level, the surfaces could still look rough and sponge-like, causing the light to scatter off of them.”
While some groups achieve the highest-quality nitride by purchasing it from companies that grow it perfectly, Parto explained, “We have to grow it ourselves, because we have to put the defect under the material, and also, we’re using a special type of silicon nitride that minimizes the background light for single-photon applications, and the companies don’t do that.”
Parto can grow his nitrides in a plasma-enhanced chemical vapor deposition oven in the cleanroom at UCSB, but because it is a heavily used shared facility, he is not able to customize some settings that would allow him to grow material of sufficient quality. The, plan, he says, is to use these results to apply for new grants that would make it possible “to get our own tools and hire students to do this work.” More

A new type of polysulfate compound that can form thin, flexible films has properties that could make it a material of choice for many high-performance electrical components, according to a study from chemists and materials scientists at Scripps Research and the Lawrence Berkeley National Laboratory (LBNL).
In the study, published January 18 in Joule, the scientists found that the new polysulfates can be used to make polymer film capacitors that store and discharge high density of electrical energy while tolerating heat and electric fields beyond the limits of existing polymer film capacitors.
“Our findings suggest that energy-storing capacitors and other devices based on these new polysulfates could see wide application, including in electric vehicle power systems,” says study co-senior author Peng Wu, PhD, a professor in the Department of Molecular Medicine at Scripps Research.
The other co-senior authors were K. Barry Sharpless, PhD, W.M. Keck Professor of Chemistry at Scripps Research, and Yi Liu, PhD, Facility Director for Organic and Macromolecular Synthesis at LBNL’s Molecular Foundry, a multidisciplinary facility for the scientific and technical investigation of new materials.
The Sharpless and Wu labs recently synthesized many previously inaccessible polysulfates using the sulfur fluoride exchange (SuFEx) reaction, which was discovered in the Sharpless lab. SuFEx is part of a growing set of molecule-building methods known as click chemistry for their high efficiency and easy reaction requirements. Sharpless was awarded a share of the 2022 Nobel Prize in Chemistry for his pioneering work on click chemistry methods.
In investigations at Liu’s lab at LBNL’s Molecular Foundry, the researchers discovered that some of the new polysulfates have superior “dielectric” properties. Dielectric materials are electrical insulators in which positive and negative charges separate — storing energy, in effect — when the materials are exposed to electric fields. They are used in capacitors, transistors and other ubiquitous components of modern electronic circuits.

Many of the dielectric materials in contemporary use are lightweight, flexible, plastic-like materials called polymers. The new polysulfates also are polymers, but have greatly improved properties compared to commercial dielectric polymers. The team found that capacitors made from one of the new polysulfates, when enhanced with a thin film of aluminum oxide, could discharge a high density of energy, while withstanding electric fields (more than 700 million volts per meter) and temperatures (150 degrees C) that would destroy the most widely used polymer film capacitors.
The researchers noted that the heat sensitivity of standard polymer capacitors often necessitates expensive and cumbersome cooling measures in systems that use them — for example, in some electric car models. Thus, adoption of the new polysulfate dielectrics could lead to cheaper, simpler, more durable power systems in electric cars and many other applications, they say.
“I was very surprised at first, and still am — I think we all are. How can a classic force from the domain of physics, like the electric field force, be modulated by a thin chemical-polymer film in its path? The results speak for themselves though, and now seems a good time to share this puzzle,” says Sharpless.
The researchers continue to synthesize and investigate new polysulfates to find some that have even better properties.
“The polysulfate polymers we examined in this study can do very well at 150 degrees C, but we think we can find related polysulfates that can handle 200 to 250 degrees C with little or no loss of function,” Liu says.
“High performing polysulfate dielectrics for electrostatic energy storage under harsh conditions” was co-authored by He Li, Boyce Chang, Antoine Laine, Le Ma, Chongqing Yang, Junpyo Kwon, Steve Shelton, Liana Klivansky, Virginia Altoe, Adam Schwartzberg, Robert Ritchie, Ting Xu, Miquel Salmeron, Ricardo Ruiz, and Yi Liu, all of LBNL; Zongliang Xie, Tianlei Xu and Zongren Peng of Xi’an Jiaotong University; and by Hunseok Kim, Bing Gao, K. Barry Sharpless, and Peng Wu of Scripps Research.
The research was funded in part by the Department of Energy (DE-AC02-05CH11231,), the National Science Foundation (CHE-1610987), and the National Institutes of Health (R35GM1139643). More

Biomedical engineers at the University of California, Davis, have created semi-living “cyborg cells.” Retaining the capabilities of living cells, but unable to replicate, the cyborg cells could have a wide range of applications, from producing therapeutic drugs to cleaning up pollution. The work was published Jan. 11 in Advanced Science.
Synthetic biology aims to engineer cells that can carry out novel functions. There are essentially two approaches in use, said Cheemeng Tan, associate professor of biomedical engineering at UC Davis and senior author on the paper. One is to take a living bacterial cell and remodel its DNA with new genes that give it new functions. The other is to create an artificial cell from scratch, with a synthetic membrane and biomolecules.
The first approach, an engineered living cell, has great flexibility but is also able to reproduce itself, which may not be desirable. A completely artificial cell cannot reproduce but is less complex and only capable of a limited range of tasks.
Infused with artificial polymer
Tan and the UC Davis team came up with a third approach. They infused living bacterial cells with the basic units of an artificial polymer. Once inside the cell, polymer was cross-linked into a hydrogel matrix by exposure to ultraviolet light. The cells could maintain their biological activity but could not reproduce.
“The cyborg cells are programmable, do not divide, preserve essential cellular activities, and gain nonnative abilities,” Tan said.
The cyborg cells were more resistant to stressors that would kill normal cells, such as exposure to hydrogen peroxide, antibiotics or high pH, the researchers found.
Finally, they were able to engineer the cells so that they could invade cancer cells grown in the lab.
The group is carrying out further research on how to create and control cyborg cells and on the effects of different matrix materials. They also hope to explore their use in a wide range of applications, from meeting environmental challenges to diagnosing and treating diseases.
“Finally, we are interested in the bioethics of applying cyborg cells as they are cell-derived biomaterials that are neither cells nor materials,” Tan said.
Additional co-authors on the paper are: Luis Contreras-Llano, Conary Meyer, Ofelya Baghdasaryan, Shahid Khan, and Aijun Wang, UC Davis Department of Biomedical Engineering; Tanner Henson, UC Davis Department of Surgery; Yu-Han Liu, Chi-Long Lin, Che-Ming J. Hu, Academia Sinica, Taiwan.
An application has been submitted for a provisional patent on the process. The work was supported in part by grants from the National Institutes of Health. More

A new computational system uses satellite data to identify sites on land where people dispose of waste, providing a new tool to monitor waste and revealing sites that may leak plastic into waterways. Caleb Kruse of Earthrise Media in Berkeley, California, Dr. Fabien Laurier from the Minderoo Foundation in Washington DC, and colleagues present this method in the open-access journal PLOS ONE on January 18, 2022.
Every year, millions of metric tons of plastic waste end up in oceans, harming hundreds of species and their ecosystems. Most of this waste comes from land-based sources that leak into watersheds. Efforts to address this issue require better understanding of where people dispose of waste on land, but resources to detect and monitor such sites — both official sites and informal or illegal ones — are lacking.
In recent years, the use of computational tools known as neural networks to analyze satellite data has shown great value in the field of remote sensing. Building on that work, Kruse and colleagues developed a new system of neural networks to analyze data from the European Space Agency’s Sentinel-2 satellites and demonstrated its potential for use in monitoring waste sites on land.
To evaluate the performance of the new system, the researchers first applied it to Indonesia, where it detected 374 waste sites — more than twice the number of sites reported in public records. Broadening to all countries across Southeast Asia, the system identified a total of 966 waste sites — nearly three times the number of publicly recorded sites — that were subsequently confirmed to exist via other methods.
The researchers demonstrated that their new system can be used to monitor waste sites over time. In addition, they showed that nearly 20 percent of the waste sites they detected are found within 200 meters of a waterway, with some visibly spilling into rivers that eventually reach the ocean.
These findings, as well as future findings using this system, could help inform waste-management policies and decision-making. The data are publicly available, so stakeholders can use it to advocate for action within their communities. Looking ahead, the researchers plan to refine and expand their new waste site-monitoring system globally.
The authors add: “For the first time, Global Plastic Watch arms governments and researchers around the world with data that can guide better waste management interventions, ensuring land-based waste doesn’t end up in our oceans.” More

First, they walked. Then, they saw the light. Now, miniature biological robots have gained a new trick: remote control.
The hybrid “eBiobots” are the first to combine soft materials, living muscle and microelectronics, said researchers at the University of Illinois Urbana-Champaign, Northwestern University and collaborating institutions. They described their centimeter-scale biological machines in the journal Science Robotics.
“Integrating microelectronics allows the merger of the biological world and the electronics world, both with many advantages of their own, to now produce these electronic biobots and machines that could be useful for many medical, sensing and environmental applications in the future,” said study co-leader Rashid Bashir, an Illinois professor of bioengineering and dean of the Grainger College of Engineering.
Bashir’s group has pioneered the development of biobots, small biological robots powered by mouse muscle tissue grown on a soft 3D-printed polymer skeleton. They demonstrated walking biobots in 2012 and light-activated biobots in 2016. The light activation gave the researchers some control, but practical applications were limited by the question of how to deliver the light pulses to the biobots outside of a lab setting.
The answer to that question came from Northwestern University professor John A. Rogers, a pioneer in flexible bioelectronics, whose team helped integrate tiny wireless microelectronics and battery-free micro-LEDs. This allowed the researchers to remotely control the eBiobots.
“This unusual combination of technology and biology opens up vast opportunities in creating self-healing, learning, evolving, communicating and self-organizing engineered systems. We feel that it’s a very fertile ground for future research with specific potential applications in biomedicine and environmental monitoring,” said Rogers, a professor of materials science and engineering, biomedical engineering and neurological surgery at Northwestern University and director of the Querrey Simpson Institute for Bioelectronics.

To give the biobots the freedom of movement required for practical applications, the researchers set out to eliminate bulky batteries and tethering wires. The eBiobots use a receiver coil to harvest power and provide a regulated output voltage to power the micro-LEDs, said co-first author Zhengwei Li, an assistant professor of biomedical engineering at the University of Houston.
The researchers can send a wireless signal to the eBiobots that prompts the LEDs to pulse. The LEDs stimulate the light-sensitive engineered muscle to contract, moving the polymer legs so that the machines “walk.” The micro-LEDs are so targeted that they can activate specific portions of muscle, making the eBiobot turn in a desired direction.
The researchers used computational modeling to optimize the eBiobot design and component integration for robustness, speed and maneuverability. Illinois professor of mechanical sciences and engineering Mattia Gazzola led the simulation and design of the eBiobots. The iterative design and additive 3D printing of the scaffolds allowed for rapid cycles of experiments and performance improvement, said Gazzola and co-first author Xiaotian Zhang, a postdoctoral researcher in Gazzola’s lab.
The design allows for possible future integration of additional microelectronics, such as chemical and biological sensors, or 3D-printed scaffold parts for functions like pushing or transporting things that the biobots encounter, said co-first author Youngdeok Kim, who completed the work as a graduate student at Illinois.
The integration of electronic sensors or biological neurons would allow the eBiobots to sense and respond to toxins in the environment, biomarkers for disease and more possibilities, the researchers said.
“In developing a first-ever hybrid bioelectronic robot, we are opening the door for a new paradigm of applications for health care innovation, such as in-situ biopsies and analysis, minimum invasive surgery or even cancer detection within the human body,” Li said.
The National Science Foundation and the National Institutes of Health supported this work.
Video: https://youtu.be/MI__Nm6EzvA More

Researchers have been looking to replace silicon in electronics with materials that provide a higher performance and lower power consumption while also having scalability. An international team is addressing that need by developing a promising process to develop high-quality 2D materials that could power next-generation electronics.
Sang-Hoon Bae, an assistant professor of mechanical engineering and materials science at the McKelvey School of Engineering at Washington University in St. Louis, is one of three researchers leading the multi-institutional work published Jan. 18 in Nature, together with his doctoral student Justin S. Kim and postdoctoral research associate Yuan Meng.
The work, which includes two technical breakthroughs, is the first to report that their method to grow semiconductor materials, known as transition metal dichalcogenides (TMD), would make devices faster and use less power.
The team, co-led by Jeehwan Kim, an associate professor of mechanical engineering and of materials science and engineering at the Massachusetts Institute of Technology, and Jin-Hong Park, a professor of information and communication engineering and of electronic and electrical engineering at Sungkyunkwan University, had to overcome three extremely difficult challenges to create the new materials: securing single crystallinity at wafer-scale; preventing irregular thickness during growth at wafer-scale; and vertical heterostructures at wafer-scale.
Bae said 3D materials go through a process of roughening and smoothing to become an even-surfaced material. However, 2D materials don’t allow this process, resulting in an uneven surface that makes it difficult to have a large-scale, high-quality, uniform 2D material.
“We designed a geometric-confined structure that facilitates kinetic control of 2D materials so that all grand challenges in high-quality 2D material growth are resolved,” Bae said. “Thanks to the facilitated kinetic control, we only needed to grow self-defined seeding for a shorter growing time.”
The team made another technical breakthrough by demonstrating single-domain heterojunction TMDs at the wafer scale, or a large scale, by layer-by-layer growth. To confine the growth of the nuclei, they used various substrates made from chemical compounds. These substrates formed a physical barrier that prevented lateral-epitaxy formation and forced vertical growth.
“We believe that our confined growth technique can bring all the great findings in physics of 2D materials to the level of commercialization by allowing the construction of single domain layer-by-layer heterojunctions at the wafer-scale,” Bae said.
Bae said other researchers are studying this material at very small sizes of tens to hundreds of micrometers.
“We scaled up because we can solve the issue by producing the high-quality material at large scale,” Bae said. “Our achievement will lay a strong foundation for 2D materials to fit into industrial settings.”
This research was supported by funding from Intel; DARPA (029584-00001 and 2018-JU-2776); and Institute for Basic Science (IBS-R034-D1). More