Science
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Extreme Materials for Fusion with Metal Cocktail
The research team under Professor Ryu Ho-jin of the Department of Nuclear and Quantum Engineering has developed a new material for facing fusion plasma environments using metal powder mixing technology. This technology is expected to extend the range of materials that can be designed for use in extreme environments such as in fusion power generators.
The durability of the tokamak vessel, which holds high-temperature plasma, is very important to create fusion power reactors, which are expected to be a future energy source. Currently, high-melting-point metals, such as tungsten, are considered plasma-facing materials to protect the tokamak vessel. However, high-energy thermal shocks, plasma ions, and neutrons are fatal to the plasma-facing material during high temperature fusion plasma operation. Therefore, it is necessary to develop new high-performance materials.
The ITER project, in which seven countries including the United States, the EU, and Korea participate jointly, is constructing a nuclear fusion experimental reactor in France with the goal of achieving the first plasma in 2025 and deuterium-tritium fusion operation in 2035. In Korea, the KSTAR tokamak at the National Fusion Research Institute has succeeded in maintaining high-performance plasma for 70 seconds.
Researchers in Europe, the United States, and China, who are leading the research on fusion plasma-facing materials, are studying the improvement of physical properties by adding a small amount of metal elements to tungsten. However, Professor Ryu’s team reported that by mixing various metals’ powders, including tungsten, they have succeeded in producing a new material that has twice the hardness and strength of tungsten. The difference in the atomic sizes of the well-mixed elements in the alloy is very significant because it makes it difficult to deform the alloy.
The team will continue its research to find alloying compositions that optimize mechanical properties as well as thermal conductivity, plasma interactions, neutron irradiation embrittlement, tritium absorption, and high-temperature oxidation properties.
Professor Ryu said, "Fusion plasma-facing materials are exposed to extreme environments and no metal is capable of withstanding thermal shock, plasma, and neutron damage simultaneously. As a result of this research, attempts to develop complex metallic materials for nuclear fusion and nuclear power are expected to become more active around the world. "
Ph.D. candidate Owais Ahmed Waseem is the first author of this project. The research is supported by the Ministry of Science, ICT and Future Planning, the Korea Research Foundation's Fusion Basic Research project, and the Engineering Research Center. The results were published in 'Scientific Report' on May 16.
Figure 1. Tungsten-based high strengh alloy sample
Figure 2. Fusion plasma facing material development by powder processing of refractory elements
2017.05.26 View 8585 -
Total Synthesis of Flueggenine C via an Accelerated Intermolecular Rauhut-Currier Reaction
The first total synthesis of dimeric securinega alkaloid (-)-flueggenine C was completed via an accelerated intermolecular Rauhut–Currier (RC) reaction. The research team led by Professor Sunkyu Han in the Department of Chemistry succeeded in synthesizing the natural product by reinventing the conventional RC reaction.
The total synthesis of natural products refers to the process of synthesizing secondary metabolites isolated from living organisms in the laboratory through a series of chemical reactions. Each stage of chemical reaction needs to be successful to produce the final target molecule, and thus the process requires high levels of patience and creativity. For that reason, the researchers working on natural products total synthesis are often called “molecular artists”.
Despite numerous reports on the total synthesis of monomeric securinegas, the synthesis of dimeric securinegas, whose monomeric units are connected by a putative enzymatic RC reaction, has not been reported to date.
The team used a Rauhut-Currier (RC) reaction, a carboncarbon bond forming a reaction between two Michael acceptors first reported by Rauhut and Currier in 1963, to successfully synthesize a dimeric natural product, flueggenine C. This new work featured the first application of an intermolecular RC reaction in total synthesis.
The conventional intermolecular RC reaction was driven non-selectively by a toxic nucleophilic catalyst at a high temperature of over 150°C and a highly concentrated reaction mixture, and thus has never been applied to natural products total synthesis. To overcome this long-standing problem, the research team placed a nucleophilic moiety at the γ-position of the enone derivative. As a result, the RC reaction could be induced by the simple addition of a base at ambient temperature and dilute solution, without the need of a nucleophilic catalyst. Using this newly discovered reactivity, the team successfully synthesized the natural product (-)-flueggenine C from commercially available amino acid derivative in 12 steps.
Professor Han said, “Our key finding regarding the remarkably improved reactivity and selectivity of the intermolecular RC reaction will serve as a significant stepping stone in allowing this reaction to be considered a practical and reliable chemical tool with broad applicability in natural products, pharmaceuticals, and materials syntheses. ”
This research was led by Ph.D. candidate Sangbin Jeon and was published in The Journal of the American Chemical Society (JACS) on May 10. This research was funded by KAIST start-up funds, HRHR (High-Risk High-Return), RED&B (Research, Education, Development & Business) projects, the National Research Foundation of Korea, and the Institute for Basic Science.
(Figure 1: Representative dimeric/oligomeric securinega alkaloids)
(Figure 2: Our reinvented Rauhut-Currier reaction)
(Figure 3: Total Synthesis of (-)-flueggenine C)
2017.05.23 View 8391 -
Distinguished Professor Lee Elected to the NAS
Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering was elected as a foreign associate to the US National Academy of Sciences (NAS) on May 2. The National Academy of Sciences elected 84 new members and 21 foreign associates in recognition of their distinguished and continuing achievements in their original research. Election to the Academy is widely regarded as one of the highest honors that a scientist can receive.
Professor Lee was also elected in 2010 as a member of the US National Academy of Engineering (NAE) for his leadership in microbial biotechnology and metabolic engineering, including the development of fermentation processes for biodegradable polymers and organic acids. Until 2016, there are only 12 people worldwide who are foreign associates of both NAS and NAE.
He is the first Korean elected to both prestigious academies, the NAS and the NAE in the US. Professor Lee is currently the dean of KAIST Institutes, the world leading institute for multi-and interdisciplinary research. He is also serving as co-chair of the Global Council on Biotechnology and member of the Global Future Council on the Fourth Industrial Revolution, the World Economic Forum.
2017.05.16 View 7933 -
Study Identifies the Novel Molecular Signal for Triggering Septic Shock
Professor Seyun Kim’s team at the Department of Biological Sciences reported the mechanism by which cellular signaling transduction networks are precisely controlled in mediating innate immune responses, such as sepsis, by the enzyme IPMK (Inositol polyphosphate multikinase) which is essential for inositol biosynthesis metabolism.
In collaboration with Professor Hyun Seong Roh at Seoul National University, the study’s first author, Eunha Kim, a Ph.D. candidate in Department of Biological Sciences, performed a series of cellular, biochemical, and physiological experiments searching for the new function of IPMK enzymes in macrophages. The research findings were published in Science Advances on April 21.
Professor Kim’s team has been investigating various inositol metabolites and their biosynthesis metabolism for several years and has multilaterally identified the signaling actions of IPMK for controlling cellular growth and energy homeostasis.
This research showed that the specific deletion of IPMK enzymes in macrophages could significantly reduce levels of inflammation and increase survival rates in mice when they were challenged by microbial septic shock and endotoxins. This suggests a role for IPMK enzymes in mediating innate inflammatory responses that are directly related to a host’s defense against pathogenic bacterial infection.
The team further discovered that IPMK enzymes directly bind to TRAF6 proteins, a key player in immune signaling, thus protecting TRAF6 proteins from ubiquitination reactions that are involved in protein degradation. In addition, Kim and his colleagues successfully verified this IPMK-dependent immune control by employing short peptides which can specifically interfere with the binding between IPMK enzymes and TRAF6 proteins in macrophage cells.
This research revealed a novel function of IPMK enzymes in the fine tuning of innate immune signaling networks, suggesting a new direction for developing therapeutics targeting serious medical conditions such as neuroinflammation, type 2 diabetes, as well as polymicrobial sepsis that are developed from uncontrolled host immune responses. This research was funded by the Ministry of Science, ICT and Future Planning.
(Figure: Deletion of IPMK (inositol polyphosphate multikinase) in macrophages reduces the stability of TRAF6 protein which is the key to innate immune signaling, thereby blocking excessive inflammation in response to pathological bacterial infection.)
2017.05.11 View 8197 -
Professor Jinah Park Received the Prime Minister's Award
Professor Jinah Park of the School of Computing received the Prime Minister’s Citation Ribbon on April 21 at a ceremony celebrating the Day of Science and ICT. The awardee was selected by the Ministry of Science, ICT and Future Planning and Korea Communications Commission.
Professor Park was recognized for her convergence R&D of a VR simulator for dental treatment with haptic feedback, in addition to her research on understanding 3D interaction behavior in VR environments. Her major academic contributions are in the field of medical imaging, where she developed a computational technique to analyze cardiac motion from tagging data.
Professor Park said she was very pleased to see her twenty-plus years of research on ways to converge computing into medical areas finally bear fruit. She also thanked her colleagues and students in her Computer Graphics and CGV Research Lab for working together to make this achievement possible.
2017.04.26 View 7938 -
Tactile Sensor for Robot Skin Advanced by KAIST Team
The joint research team of Professors Jung Kim and Inkyu Park from the Department of Mechanical Engineering developed a tactile sensor that can act as skin for robots using silicon and carbon materials. This technology produced a sensor that can absorb shock and distinguish various forms of touch, and it is hoped to be used as robot skin in the future.
Skin serves an important role as the largest organ of the human body. As well as protecting major organs from external shock, skin also measures and distinguishes delicate tactile information and transfer it to the nervous system.
Current robotic sensory technology allows robots to have visual and auditory systems at nearly similar levels to human capacity, but there are limitations in tactile sensors that can detect changes in the environment throughout the body. To apply skin with similar functions as humans to robots, it is essential to develop skin sensor technology with high flexibility and high shock absorption. Another limitation for developing robot skin was connecting numerous sensors all over the body using electric wiring.
To overcome this problem, the research team combined silicon and carbon nanotubes (CNT) to produce a composite, which was then used in combination with a medical imaging technique called electrical impedance tomography (EIT). This led to technology that can distinguish various forms of force over a large area without electrical wiring.
The sensing material can distinguish the location and the size of various forms by touch, and thus can be applied to robot skin that can absorb shock as well as serves as a 3D computer interface and tactile sensor. It can withstand strong force such as a hammer strike, and can be re-used even after partial damage to the sensor by filling and hardening the damaged region with composite. Further, the sensor can be made by filling a 3D shape frame with silicon-nanotube composite. Using this technology, new forms of computer interaces can be developed with both curbed and flat surfaces.
This research was conducted through a collaboration between Professor Park, an expert in nanostructures and sensors, and Professor Kim, an expert in bio-robotics. Hence, the technology is likely to be applied in real products.
Professor Kim said, “Flexible tactile sensors can not only be directly adhered to the body, but they also provides information on modified states in multiple dimensions”. He continued, “This technology will contribute to the soft robot industry in the areas of robot skin and the field of wearable medical appliances.”
Professor Park said, “This technology implemented a next-generation user interface through the integration of functional nano-composite material and computer tomography.”
This research was published in Scientific Reports, a sister journal of Nature, online on January 25. This research was conducted as joint research by first author Hyo-Sang Lee, as well as Donguk Kwon and Ji-seung Cho, and was funded by the Ministry of Science, ICT and Future Planning.
(Fiigrue 1: Robotic hand responding to resistance via a connection with the developed tactile sensor)
(Figure 2: Manufacturing process for pressure-resistant composite using silicon rubber and carbon nanotubes)
(Figure 3: Computer interface using pressure-resistant composite)
2017.04.17 View 10853 -
Professor Won Do Heo Receives 'Scientist of the Month Award'
Professor Won Do Heo of the Department of Biological Sciences was selected as the “Scientist of the Month” for April 2017 by the Ministry of Science, ICT and Future Planning and the National Research Foundation of Korea.
Professor Heo was recognized for his suggestion of a new biological research method developing various optogenetics technology which controls cell function by using light. He developed the technology using lasers or LED light, without the need for surgery or drug administration, to identify the cause of diseases related to calcium ions such as Alzheimer’s disease and cancer.
The general technique used in optogenetics, that control cells in the body with light, is the simple activation and deactivation of neurons.
Professor Heo developed a calcium ion channel activation technique (OptoSTIM1) to activate calcium ions in the body using light. He also succeeded in increasing calcium concentrations with light to enhance the memory capacity of mice two-fold.
Using this technology, the desired amount and residing time of calcium ion influx can be controlled by changing light intensity and exposure periods, enabling the function of a single cell or various cells in animal tissue to be controlled remotely.
The experimental results showed that calcium ion influx can be activated in cells that are affected by calcium ions, such as normal cells, cancer cells, and human embryonic stem cells. By controlling calcium concentrations with light, it is possible to control biological phenomena, such as cellular growth, neurotransmitter transmission, muscle contraction, and hormone control.
Professor Heo said, “Until now, it was standard to use optogenetics to activate neurons using channelrhodopsin. The development of this new optogenetic technique using calcium ion channel activation can be applied to various biological studies, as well as become an essential research technique in neurobiology.
The “Scientist of the Month Award” is given every month to one researcher who made significant contributions to the advancement of science and technology with their outstanding research achievement. The awardee will receive prize money of ten million won.
2017.04.07 View 7323 -
Expanding the Genetic Code of Mus Musculus
Professor Hee-Sung Park of the Department of Chemistry, who garnered attention for his novel strategy of installing authentic post-translational modifications into recombinant proteins, expanded his research portfolio to another level. Professor Park’s team was the first to report the generation of a mouse strain with an expanded genetic code, allowing site-specific incorporation of unnatural amino acids.
Professor Park published the research on the new chemical biology method for achieving selective chemical modifications in proteins in Science last September. The research team, this time in collaboration with Professor Chan Bae Park of the Department of Physiology at the Ajou University School of Medicine, demonstrated temporal and spatial control of protein acetylation in various organs of the transgenic mouse using a recombinant green fluorescent protein as a model protein. This research was published in the online edition of Nature Communications on February 21.
This approach enables the rapid onset of position-specific acetylation of a target protein at any developmental stage, facilitating temporal and spatial control of protein acetylation in various organs of the transgenic mouse. Such temporal and spatial control of protein acetylation will be of prime importance for investigating many essential biological processes and human diseases at the tissue and organism level.
Almost all human proteins, the products of about 25,000 genes, are known to undergo various post-translational modifications during and after synthesis. Post-translation modifications regulate the function of cellular proteins, playing a key role in many essential processes such as delivering signals and body growth. However, the unusual protein modifications, aroused from genetic and/or environmental factors, trigger severe diseases including cancer, dementia, and diabetes.
The team inserted transgenes into the mouse genome to allocate the site-specific addition of unnatural amino acids. The researchers inserted a modified version of lysine into the house mice, which allowed for the control of the acetylation. They used recombinant green fluorescent proteins from transgenic house mice as models for control of the acetylation.
The team was also able to regulate the acetylation of specific temporal and spatial frames in the mice, restraining the abnormality in proteins to certain organs such as the liver and kidneys. The research team said the strategy will provide a powerful tool for systematic in vivo study of cellular proteins in the most commonly used mammalian model organisms for human physiology and disease. Professor Park said, “This method can be easily extended to generate a wide range of custom-made transgenic mouse strains for further investigating diverse proteins of interest.” He added, “This method can be further extended to generate a wide range of custom-made transgenic mouse strains, opening a new paradigm for investigating anti-cancer and cerebral disease treatments.
This work was supported by grants from KAIST Systems Healthcare and the Medicinal Bioconvergence Research Center and the Intelligent Synthetic Biology Center of the Global Frontier Project funded by the Ministry of Science, ICT & Future Planning and the Ministry of Food and Drug Safety.
(Figure:Temporal and spatial control of in vivo protein acetylation)
(a) Temporal expression of acetylated GFPuv in the AcK-GFPamber mouse. The expression of GFPuv in skeletal muscle, liver, and lung tissues was detected only in the AcK-injected mouse. Scale bar, 200 µm. (b) Western blotting of anti-FLAG-immunoprecipitated proteins from tissues of the AcK-GFPamber mouse. Acetylated GFPuv was produced after AcK injection. (c) Spatial expression of acetylated GFPuv in the AcK-GFPamber mouse. Acetylated GFPuv was observed only in skeletal muscle when AcK was directly delivered to the tissues. Sacle bar, 200 µm.
2017.03.27 View 8454 -
Professor Jae Kyoung Kim Receives the 2017 HSFP Award
The Human Frontier Science Program (HSFP), one of the most competitive research grants in life sciences, has funded researchers worldwide across and beyond the field since 1990. Each year, the program selects a handful of recipients who push the envelope of basic research in biology to bring breakthroughs from novel approaches. Among its 7,000 recipients thus far, 26 scientists have received the Nobel Prize. For that reason, HSFP grants are often referred to as “Nobel Prize Grants.”
Professor Jae Kyoung Kim of the Mathematical Sciences Department at KAIST and his international collaborators, Professor Robert Havekes from the University of Groningen, the Netherlands, Professor Sara Aton from the University of Michigan in Ann Arbor, the United States, and Professor Matias Zurbriggen from the University of Düsseldorf, Germany, won the Young Investigator Grants of the 2017 HSFP.
The 30 winning teams of the 2017 competition (in 9 Young Investigator Grants and 21 Program Grants) went through a rigorous year-long review process from a total of 1,073 applications submitted from more than 60 countries around the world. Each winning team will receive financial support averaging 110,000-125,000 USD per year for three years.
Although Professor Kim was trained as a mathematician, he has extended his research focus into biological sciences and attempted to solve some of the most difficult problems in biology by employing mathematical theories and applications including nonlinear dynamics, stochastic process, singular perturbation, and parameter estimation.
The project that won the Young Investigator Grants was a study on how a molecular circadian clock may affect sleep-regulated neurophysiology in mammals. Physiological and metabolic processes such as sleep, blood pressure, and hormone secretion exhibit circadian rhythms in mammals. Professor Kim used mathematical modeling and analysis to explain that the mammalian circadian clock is a hierarchical system, in which the master clock in the superchiasmatic nucleus, a tiny region in the brain that controls circadian rhythms, functions as a pacemaker and synchronizer of peripheral clocks to generate coherent systematic rhythms throughout the body.
Professor Kim said, “The mechanisms of our neuronal and hormonal activities regulating many of our bodily functions over a 24-hour cycle are not yet fully known. We go to sleep every night, but do not really know how it affects our brain functions. I hope my experience in mathematics, along with insights from biologists, can find meaningful answers to some of today’s puzzling problems in biological sciences, for example, revealing the complexities of our brains and showing how they work.”
“In the meantime, I hope collaborations between the fields of mathematics and biology, as yet a rare phenomenon in the Korean scientific community, will become more popular in the near future.”
Professor Kim received his doctoral degree in Applied and Interdisciplinary Mathematics in 2013 from the University of Michigan and joined KAIST in 2015. He has published numerous articles in reputable science journals such as Science, Molecular Cell, Proceedings of the National Academy of Sciences, and Nature Communications.
Both the Program Grants and Young Investigator Grants support international teams with members from at least two countries for innovative and creative research. This year, the Program Grants were awarded to research topics ranging from the evolution of counting and the role of extracellular vesicles in breast cancer bone metastasis to the examination of obesity from a mechanobiological point of view.
The Young Investigator Grants are limited to teams that established their independent research within the last five years and received their doctoral degrees within the last decade. Besides Professor Kim’s study, such topics as the use of infrasound for navigation by seabirds and protein formation in photochemistry and photophysics were awarded in 2017.
Full lists of the 2017 HFSP winners are available at: http://www.hfsp.org/awardees/newly-awarded.
About the Human Frontier Science Program (HFSP):
The HFSP is a research funding program implemented by the International Human Frontier Science Program (HFSPO) based in Strasbourg, France. It promotes intercontinental collaboration and training in cutting-edge, interdisciplinary research specializing in life sciences. Founded in 1989, the HFSPO consists of the European Union and 14 other countries including the G7 nations and South Korea.
2017.03.21 View 9046 -
13 KAIST Faculty Named as Inaugural Members of Y-KAST
The Korean Academy of Science and Technology (KAST) launched the Young Korean Academy of Science and Technology (Y-KAST) and selected 73 scientists as its inaugural members on February 24. Among them, 13 KAIST faculty were recognized as the inaugural members of Y-KAST.
Y-KAIST, made up of distinguished mid-career scientists under the age of 45, will take the leading role in international collaboration as well as innovative agenda-making in science and technology.
The inaugural members include Professor Hyotcherl Ihee of the Department of Chemistry and Dr. Sung-Jin Oh of the Center for Mathematical Challenges at the Korea Institute for Advanced Study (KIAS), affiliated with KAIST. Professor Ihee is gaining wide acclaim in the fields of physics and chemistry, and in 2016, Dr. Oh was the youngest ever awardee of the Presidential Award of Young Scientist.
The other Y-KAIST members are as follows: Professors Haeshin Lee of the Department of Chemistry; Mi Young Kim, Byung-Kwan Cho, and Ji-Joon Song of the Department of Biological Sciences; Song-Yong Kim of the Department of Mechanical Engineering; Sang-il Oum of the Department of Mathematical Sciences; Jung Kyoon Choi of the Department of Bio and Brain Engineering; Seokwoo Jeon, Sang Ouk Kim, and Il-Doo Kim of the Department of Materials Science and Engineering; Jang Wook Choi of the Graduate School of EEWS (Energy, Environment, Water and Sustainability); and Jeong Ho Lee of the Graduate School of Medical Science and Engineering.
The leading countries of the Academy of Science, which include Germany, Sweden, Belgium, Canada, and Japan, have established the Young Academy of Science since 2010 in order to encourage the research activities of their young scientists and to establish a global platform for collaborative research projects through their active networking at home and abroad.
President Myung-Chul Lee of KAST said, “We will spare no effort to connect these outstanding mid-career researchers for their future collaboration. Their networking will make significant impacts toward their own research activities as well as the global stature of Korea’s science and technology R&D.
(Photo caption: Members of Y-KAST pose at the inaugural ceremony of Y-KAST on February 24.)
2017.03.02 View 15377 -
Dr. Sung-Chul Shin Selected 16th President of KAIST
(President Sung-Chul Shin)
The KAIST Board of Trustees elected Professor Sung-Chul Shin of the Department of Physics the 16th president of KAIST on February 21. Professor Shin succeeds President Sung-Mo Kang whose four-year term will end on February 23. He is the first KAIST alumnus to serve as its president.
The Board of Trustees announced, “We believe that Professor Shin’s scientific achievement, outstanding leadership, and clear vision will serve KAIST faculty, students, and staff very well. He will be the best person to help KAIST leap forward in the four years ahead.”
The newly-elected president said, “I am humbled and honored to have been elected to lead such a prestigious institute of Korea. Aiming to be one of the top ten global universities, KAIST will continue to innovate its systems.” Previously, Dr. Shin led the Daegu Gyeongbuk Institute of Science and Technology (DGIST) for six years as president since 2011.
Professor Shin joined the KAIST faculty in 1989. He graduated from Seoul National University and then earned his MS degree in condensed matter physics at KAIST in 1977. After earning his Ph.D. in material physics at Northwestern University in 1984, he worked at Eastman Kodak Research Labs as a senior research scientist for five years.
Before heading to DGIST, President Shin held key administrative positions at KAIST from the early 1990s including dean of planning, dean of the international office, and vice-dean of student affairs. During President Robert Laughlin’s tenure, the first foreign president at KAIST, he served as vice-president for two years from 2004. He also served on the Presidential Advisory Council on Science and Technology of the Korean government as vice chairperson from 2015 to 2016.
A renowned scholar in the field of nanoscience, President Shin’s research focuses on the artificial synthesis and characterization of nonmagnetic materials, magnetic anisotropy, and magneto-optical phenomena. He leads the Laboratory for Nanospinics of Spintronic Materials at KAIST and has published in 290 journals while holding 37 patents.
A fellow in the American Physical Society (APS) since 2008, he was the president of the Korean Physical Society from 2011 to 2012. He has been on the editorial board of J. Magnetism and Magnetic Materials from 2009 and was the first Korean recipient of the Asian Union of Magnetics Societies (AUMS) Award, which recognizes outstanding scientists in the field of magnetics.
President Shin envisions making KAIST’s research and education more competitive through continuing innovation. His innovation efforts will extend to the five key areas of education, research, technology commercialization, globalization, and future planning.
Among his priorities, he emphasizes multidisciplinary studies and leadership training for students. He plans to focus on undeclared major courses for undergraduates to help them expand their experience and exposure to diverse disciplines. This approach will help create well-rounded engineers, scientists, and entrepreneurs by enabling them to develop skills while leveraging a strong connection to the arts, humanities, and social sciences.
To better respond to Industry 4.0, which calls for convergence studies and collaborative work, he proposed establishing a ‘Convergence Innovation System’ by strategically selecting 10 flagship convergence research groups. In order to accelerate the technology commercialization and ecosystem of start-ups, he will strengthen entrepreneurship education, making it a prerequisite requirement for students. President Shin said he will spare no effort to incubate and spin-off ventures in which KAIST technology is being transferred. For globalization efforts, he plans to increase the ratio of foreign faculty from 9 percent to 15 percent, while doubling the current foreign student enrollment ratio of 5 percent. For future strategic innovation, he will implement a long-term innovation strategic plan dubbed ‘Vision 2031.’
2017.02.22 View 9354 -
An Improved Carbon Nanotube Semiconductor
Professor Yang-Kyu Choi and his research team of the School of Electrical Engineering at KAIST collaborated with Professor Sung-Jin Choi of Kookmin University to develop a large-scale carbon nanotube semiconductor by using a 3-D fin-gate structure with carbon nanotubes on its top.
Dong Il Lee, a postdoctoral researcher at KAIST’s Electrical Engineering School, participated in this study as the first author. It was published in ACS Nano on November 10, 2016, and was entitled “Three-Dimensional Fin-Structured Semiconducting Carbon Nanotube Network Transistor.”
A semiconductor made with carbon nanotubes operates faster than a silicon semiconductor and requires less energy, yielding higher performance.
Most electronic equipment and devices, however, use silicon semiconductors because it is difficult to fabricate highly purified and densely packed semiconductors with carbon nanotubes (CNTs).
To date, the performance of CNTs was limited due to their low density. Their purity was also low, so it was impossible to make products that had a constant yield on a large-surface wafer or substrate. These characteristics made the mass production of semiconducting CNTs difficult.
To solve these difficulties, the research team used a 3-D fin-gate to vapor-deposit carbon nanotubes on its top. They developed a semiconductor that had a high current density with a width less than 50 nm.
The three-dimensional fin structure was able to vapor-deposit 600 carbon nanotubes per micrometer. This structure could have 20 times more nanotubes than the two dimensional structure, which could only vapor-deposit thirty in the same 1 micrometer width.
In addition, the research team used semi-conductive carbon nanotubes having a purity rating higher than 99.9% from a previous study to obtain a high yield semiconductor.
The semiconductor from the research group has a high current density even with a width less than 50 μm. The new semiconductor is expected to be five times faster than a silicon-based semiconductor and will require five times less electricity during operation.
Furthermore, the new semiconductor can be made by or will be compatible with the equipment for producing silicon-based semiconductors, so there will be no additional costs.
Researcher Lee said, “As a next generation semiconductor, the carbon nanotube semiconductor will have better performance, and its effectiveness will be higher.” He also added, “Hopefully, the new semiconductor will replace the silicon-based semiconductors in ten years.”
This study received support from the Center for Integrated Smart Sensors funded by the Ministry of Science, ICT & Future Planning of Korea as the Global Frontier Project, and from the CMOS (Complementary Metal-Oxide-Semiconductor) THz Technology Convergence Center of the Pioneer Research Center Program sponsored by the National Research Foundation of Korea.
Picture 1: 3D Diagram of the Carbon Nanotube Electronic Device and Its Scanning Electron Microscope (SEM) Image
Picture 2: 3D Transistor Device on an 8-inch Base and the SEM Image of Its Cross Section
2017.02.16 View 9620