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A team of researchers including Ajou University’s Prof. Seo Hyung-tak has successfully developed an integrated optoelectronic diode capable of adapting, in a fashion similar to human visual perception, to various environments. The team’s discovery is expected to help develop visual devices with artificial nerves, intelligent photosensors, data processors, and innovations in robotics.Prof. Seo (Dept. of Materials Science and Engineering / Graduate Dept. of Energy Systems, pictured) has announced that his team has developed a photosensor diode capable of differentiating information processing depending on angles of perception. The team’s invention is discussed in detail in “Environment-Adaptable Photonic-Electronic Coupled Angular Perception System,” published in the October issue of ACS Nano (IF = 14.588). The team included two other members from Ajou: Prof. Kim Sang-wan (Dept. of Electrical and Computer Engineering) and Dr. Mohit Kumar (lead author).The human vision system is capable of adapting on its own to changes in its surroundings, including differences in lighting, by detecting changes in optic signals in real time. It is also capable of differentiating between visual signals from different angles of vision (up or down, left or right) and processing the obtained data accordingly. Human vision captures optical data and converts it into photoelectronic signals, which are then encoded into electric spikes of appropriate sizes. Information thus processed is then transmitted to the visual cortex and stored on the synaptic network.Numerous attempts have been made so far to develop artificial sight by simulating the complex and intricate workings of human visual perception. Success has been elusive so far, however, in developing artificial vision with a sufficiently simple structure and a rational energy demand.Much of the research on artificial sight circuits to date has focused on understanding and visualizing information under general lighting. Effective artificial sight, however, crucially requires a technology capable of recognizing objects from wide viewing angles. Only on the basis of angular perception can researchers proceed to develop an effective and simple humanoid photoelectronic circuit capable of replacing the excessively complex circuits that exist today. Moreover, simplifying these complex circuits requires memory storage capable of adapting automatically to diverse environments.Prof. Seo’s team has created a photosensitive semiconductor capable of adapting to changing environments and simulating the human nervous system by first creating a quality titanium dioxide (TiOs) nanofilm and then evenly arranging a silver nanowire on it. The silver nanowire (NW) maximizes the photoelectronic effect on angular visual perception, enabling the semiconductor to perceive and process visual data across a wide angle (± 70º). The Schottky-style combination of the silver nanowire and titanium dioxide also ensures the effective collection of photoelectrons to enhance sensitivity to photonic (ultraviolet) signals. This diode structure is simple, yet effectively simulates human visual perception.Using a 3x3 array, Prof. Seo’s team has created a visual perception diode whose circuit can itself recognize objects in diverse environments. The team has thus discovered that, even for the same given patterns of optic signals, the intensity and duration of memory of those signals vary depending on the given visual angles, the intensity of given light, and the duration and intervals of optic signals. The team, in other words, has demonstrated that their semiconductor is capable of working in much the same manner as the human visual nerves and cortex, and that the mechanism of their neuromorphic optic signal storage is based on the accumulation and loss of electric charges, due to photoelectric combination, on their Schottky diode.This means that the time it takes for memory stored in the titanium dioxide semiconductor to disappear varies depending on differences in the amounts of light absorbed by the semiconductor because those differences in lighting mean the creation of different amounts of light-induced charges (electron-hole pairs). With this invention, the same in-vivo memory-oblivion system can be added to the memory used to sense and store images on devices such as smartphones.Prof. Seo commented, “Artificial sight diodes require many component technologies. Our recent study is significant in that it demonstrates how a transparent semiconductor, capable of adapting to changes in environments and detecting and processing optic signals with relatively little energy, can be created.”He also expects the new diode to “have a wide variety of applications, including intelligent photosensors, data processing, and robotics.”The study has been made possible thanks to support from the Future New Material and Original Technology Development Program and the Basic Research Support Program for Experienced Basic Researchers, co-organized by the Ministry of Science and ICT and the National Research Foundation of Korea.
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19
- 작성자OI***
- 작성일2020-12-28
- 5306
- 동영상동영상
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Professor Lee Jae-hyun of Ajou University has developed a new graphene exfoliation technique for graphite, a next-generation electron material.A joint research team involving professor Lee Jae-hyun (Department of Materials Science and Engineering, photo), Son Seok-kyun of Mokpo National University, and Cho Sung-ho, director of Samsung Display, announced that the team had developed a new technique of layer-engineered large-area exfoliation of graphene. The study was published in Science Advances on October 28th and titled, “Layer-engineered large-area exfoliation of graphene”. PhD student Moon ji-Yoon and Doctor Kim Min-soo from the University of Manchester participated as lead authors. Graphene, a transparent material with rubber-like flexibility, has received a lot of attention as a “dream material” for its outstanding electrical conductivity. These characteristics make graphene perfect for rollable TVs and smartphone screens. Graphene is a compound integration of carbon atoms that form a beehive shape. This monolayer material is so thin that 100,000 layers are equal to the diameter of a human hair.The conventional method of obtaining graphene sheets from graphite flakes required workers to repeatedly peel off layers of graphite crystals using cellophane tape. This was immensely dependent on worker skill and made it almost impossible to control monolayer graphene area, number of layers and yield.Professor Lee’s team succeeded in controlling, at the atom level, the crack propagation, especially size and direction, produced when peeling off layers using cellophane tape and obtaining the desired area and number of layers. According to Lee’s new method, a specific metal film is attached to graphite to selectively, rather than randomly, control the depth and direction of cracks. The research team’s finding enables production of layer-controlled graphene: from mm2-monolayer to double layer and up to 40 layers. The average area of monolayer graphene exfoliated using the new method is up to approximately 4200 times that of monolayer graphene exfoliated by the standard method. In addition, the density per unit area of monolayer graphene increased by a maximum of 6000 times, which enables higher yield. The recent study is expected to be an alternative method for preparing graphene, as obtaining fine quality exfoliated graphene is essential for commercialization. Research was sponsored by a grant from the Korean Ministry of Science and ICT and the National Research Foundation of Korea as part of their Basic Science and Engineering Lab Program and Beginning Researcher Program. 금필름Gold Film자연 흑연으로부터 무결점 그래핀 박리Exfoliation of top graphene from bulk crystal원하는 기판으로의 전사 공정Transfer to target substrate(Top) The exfoliation process of selective monolayer graphene from natural graphite flakes through attachment of gold film. (Bottom) Graphs comparing the size and density of monolayer graphene exfoliated using the conventional method and using the new method with gold film. The average area of monolayer graphene obtained using gold film is up to 4200 times the standard exfoliation method and up to 6000 times the density.
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17
- 작성자OI***
- 작성일2020-12-18
- 6531
- 동영상동영상
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A team led by Ajou University Professor Jeon Sang-min has found that a specific gene formerly considered helpful in prevention and treatment of cancer, in fact, stimulates its development and progression. Professor Jeon Sang-min (College of Pharmacy, photo) discovered that, contrary to traditional understanding, Nuclear factor E2-related factor 2 (NRF2) is a gene that stimulates cancer development and is also related to poor clinical outcomes, not at all a tumor suppressor gene. His study was published in Clinical Cancer Research on October 19th and entitled, “NRF2 activation promotes aggressive lung cancer and associates with poor clinical outcomes”. Professor Jeon Sang-min, PhD student Choi Eun-ji, US company Genentech, and a research team from Johns Hopkins Medical Institutions participated in the recent study, which was sponsored with a grant from the Korea National R&D Program for Cancer Control (Ministry of Health and Welfare) and the Basic Science Research Program (Individual Basic Science & Engineering Research Program) under the Ministry of Science, ICT and Future Planning.NRF2 has long been considered helpful in preventing and treating cancer as it was believed to reduce reactive oxygen species (ROS) once it is processed into a transcription factor that activates anti-oxidation pathways. However, several recent findings have suggested that NRF2 may actually contribute to tumor development, because in many cases of cancer, including cancer of the lung, NRF2 was activated.Another study also found that, in lung cancer cases, NRF2 activation occurred along with the mutation of STK11/LKB1, which are other tumor suppressor genes. Accordingly, the joint research team conducted experiments based on a genetically modified lung cancer mouse model (Kras/Keap1/Stk11-KO) and analyzed the results of the latest large-scale lung cancer clinical trials (OAK, IMpower131). The research team identified that, in the genetically modified mouse model, the activation of NRF2 stimulated lung cancer development and lowered survival rates. The team also found that the STK11 gene mutation increased ROS and stimulated the progression of lung cancer development. When STK11 mutation and NRF1 activation were both taking place, they suppressed ROS, further promoted lung cancer development and significantly lowered survival rates. The research team discovered that the reason NRF2 activation and STK11 mutation happen simultaneously in lung cancer cases is because NRF2 activation reduces oxidative stress incurred by STK11 mutation leading to cancer cell survival and growth. In conclusion, the study produced meaningful findings proving that NRF2 is a tumor oncogene, not a tumor suppressor gene. The team also analyzed recent clinical trials and found that lung cancer patients with active NRFs were highly likely to have poorer chemotherapy and immunotherapy outcomes than those who didn’t have active NRFs, and had significantly lower survival rates.Professor Jeon Sang-min stated “The study suggests a paradigm shift in the role of NRF2 in cancer. […] Many attempts have been made to develop an NRF2 stimulant for cancer prevention and treatment. However, our research has set the record straight and contributed to increasing interest on the development of an NRF2 inhibitor.”Professor Jeon’s research team is continuing efforts to be the first in developing such an NRF2 inhibitor drug. Professor Jeon participated in joint creation of SCL Therapeutics, a bio start-up, for clinical development of the self-discovered NRF2 inhibitor candidate. Currently, the lab is conducting pre-clinical trials.
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15
- 작성자OI***
- 작성일2020-12-18
- 5676
- 동영상동영상
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모션 센서 적용Motion detector applied샘플구조Sample structure저항변화Change in resistance치유Healing손상Damage자가치유Self-healing수소결합Hydrogen bondingA team of researchers led by Prof. Seo Hyung-tak (Departments of Materials Science and Engineering and Energy Systems Research) has successfully developed a new self-healing composite material and a sensor based on that material. Highly conductive and elastic, the new material is expected to have wide-ranging applications, including wearable electronics, soft robotics, and artificial skin.The composite invented by Prof. Seo’s team is made of a supramolecular polymer and copper microparticles, and the team developed an electronic wearable strain sensor capable of self-healing. The researchers’ work was published as the featured article in the September 7 online issue of Advanced Electronic Materials and entitled, “Intrinsically stretchable and self-healing electroconductive composite based on supramolecular organic polymer embedded with copper microparticles.” Rubaya Yeasmin, a doctoral candidate at Ajou, was listed as first author.The human skin is structured so that it detects damage quickly and activates self-restoring mechanisms to prevent the damage from worsening and facilitate healing. Inspired by this natural self-healing mechanism of organisms, researchers worldwide are searching for new materials capable of self-healing and restoration, and possessing electroconductivity and elasticity (stretchability). It takes significant skill and resources to develop new electronic materials capable of restoring themselves after damage without external intervention or processes. Once invented, such materials can exert far-reaching ripple effects on industry and society.In this project, the research team combined a supramolecular organic polymer and copper microparticles (1 μm = 1E-6m; for comparison, the average width of a hair strand is 100 μm). The resulting composite can be manufactured on a mass scale in aerosol and gel form. The copper concentration can also be adjusted to control electroconductivity of the final product. Supramolecular polymers support elastic and self-healing hydrogen bonding. The copper concentration can also be used to control the electric properties of semiconductors and conductors. The team has optimized the electrical properties of their composite so that it can continue to restore itself, notwithstanding multiple cuts. The most remarkable characteristic about the team’s product is its highly stretchable and self-healing structure, which renders it very similar to real skin. This material is resistant to tearing and can be stretched to 120 percent of its original length. Its electric and mechanical properties are also restored even after it has been cut. The team, in fact, demonstrated that the material recovered 90 percent of its mechanical properties and 100 percent of its electrical properties in just five minutes in the given environment.The team used the new material to develop a new wearable strain sensor capable of self-healing, whose workings it successfully demonstrated by attaching it to the fingers of human subjects. By deliberately cutting and damaging the sensor and gauging its reaction, the team also confirmed its ability to restore itself.Prof. Seo explained: “The self-healing material we’ve developed was made with affordable components and processes, without the need for great cost. A wide range of applications are possible beyond only wearable sensors, and include elastic IoT sensors, soft robotics, and industrial equipment.”The project was conducted in part thanks to the Research Support Program for New Researchers with Advanced Overseas Accomplishments, the Basic Research Support Program, and the BK21 Four Program from the Ministry of Science and ICT and the National Research Foundation of Korea.
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13
- 작성자OI***
- 작성일2020-12-18
- 4722
- 동영상동영상
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A team of researchers led by Prof. Ahn Yeong-hwan (Departments of Physics and Energy Systems Research, pictured) has succeeded in creating a new quantum energy level using a material that is expected to become central to next-generation solar cells.The team’s work was published in the September issue of Nano Letters (IF = 12.344) with the title, “Phonon-Polaritons in Lead Halide Perovskite Film Hybridized with THz Metamaterials.” The team included other Ajou faculty members, including professors Ha Na-young, Park Ji-yong and Lee Soon-il, all with the Department of Physics, as well as Prof. Kim Dai-sik of the Ulsan National Institute of Science and Technology (UNIST). Kim Hwan-sik, doctoral candidate in physics at Ajou, also participated as first author.The team created a hybrid of the perovskite film and the metamaterial used to create invisibility cloaks and tested how light in the terahertz range, between infrared rays and microwaves, behaved on it. The perovskite used for this particular experiment was a lead halide type, widely expected to become the central material of much more efficient solar cells in the future.The perovskite hybrid, in its oscillating mode, reacted strongly with the electronic waves concentrated in the meta-structure, giving rise to a new phonon-polariton energy level. An energy level is the value of energy at its atomic and molecular levels. It refers to the level of energy that electrons absorb or release.The team also demonstrated that the new energy level varies depending on numerous conditions or variables. The most important of these variables is crystallinity of the perovskite film. The team discovered, for the first time in the world, that the dynamics of the phonon-polariton energy level vary by the nanocrystal growth dimensionality (one-, two-, or three-dimensional). The team also succeeded in introducing a new model for explaining the interaction between nanocrystals that grow over time and light. Prof. Ahn explained: “Our latest discovery can be applied to assessment of the crystal structure of next-generation solar cell films as well as optimization of their efficiency. Through follow-up research on the perovskite-metamaterial hybrid, we were also able to find lighting sources for future quantum optics.”The project was made possible in part thanks to the Mid-career Researcher Program, co-managed by the Ministry of Science and ICT and the National Research Foundation of Korea, and Korea Energy Technology Evaluation and Planning (KETEP)’s Energy Workforce Development Program.THz 파THz raysMAPbl3 페로브스카이트MAPbl3 perovskite메타물질Metamaterial강한 상호작용Strong reaction페로브스카이트PerovskiteMechanism of the new energy level based on the perovskite film-metamaterial hybrid
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11
- 작성자OI***
- 작성일2020-12-18
- 4665
- 동영상동영상
