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A team of Ajou scientists has developed a near infrared ray (NIR) photodetector capable of detecting deterioration and damage in human muscle structures. The new device is expected to have many applications, including medical imaging equipment that requires highly sensitive and efficient sensors.The team, led by (Dept. of Materials Science and Engineering / Graduate Dept. of Energy Systems, pictured), has developed a new image sensing device using alternating current photovoltaic effects, which offer high detectivity and rapid rise/decay time. The development was introduced in an article entitled, “Broadband alternating current photovoltaic effect: An application for high-performance sensing and imaging body aches” in the August 29 online issue of Nano Energy (IF = 16.602). The team includes Prof. Park Ji-yong yong (Dept. of Physics / Graduate Dept. of Energy Systems Research), Prof. Kim Sang-wan (Dept. of Electrical and Computer Engineering), and Dr. Mohit Kumar (first author).Photodetectors, which convert light into electric signals, have so far been associated with solar energy cells. But these devices have much broader application, as they are essential not only in new and renewable energy, but also smartphones, the Internet of Things (IoT), and optical communications. Lately, there has also been growing interest in developing medical applications as well, as photodetectors can help make diagnosis and ongoing monitoring of patients far easier. Industries and academia alike have been particularly interested in photodetector technology that can facilitate the imaging of damage to muscles inside the human body. Photodetectors are already being used in assessing patients with advanced-degree burns.Photodetector researchers, in turn, have been paying attention to NIRs, as they are expected to minimize further damage to the body by light and enable the detector to sense at greater depths of internal tissues and organs. As a result, there has been great demand for high-performance photodetectors capable of detecting even the slightest changes in NIR signals. Such photodetectors would also have to be highly energy-efficient to be installed on portable medical diagnostic devices.Compound semiconductors have been the typical choice for NIR-based photodetectors so far. These compound semiconductors, including gallium-arsenic, however, are quite expensive, have low levels of detectivity in the NIR range, and have not performed well thus far. Most critically, they fail to have the high level of detectivity necessary for medical devices to identify and image damage inside the human body.Prof. Seo’s team has sought to overcome this by laying a quality titanium oxide (TiO2) nanofilm onto a silicone (Si) substrate and controlling the surface characteristics. The researchers have also succeeded in developing a photodetector structure that maximizes optical responsivity using silver nanorays. As a result, the team was able to create a high-performance photodetector promising a much higher switching ratio (≈1E4), detectivity (≈1E11 Jones), and response time (~ 120 μs) than available today. The resulting photodetector is superior in all areas of performance over the NIR photodetectors available today.The alternating photovoltaic current enables the photodetector to generate energy from the rapidly flickering incident rays on its own, eliminating the need to connect it to an outside power source. The photodetector, moreover, generates photovoltaic currents that are nearly 39,000 times greater than direct photovoltaic currents typical of solar cells, making it very well-suited to medical imaging.Prof. Seo’s team has also identified the operating mechanism of the photodetector using Kelvin probe force and electrostatic force microscopy. The alternating incident rays generate inhomogeneous absorption-induced imbalanced carriers inside the semiconductor. The resulting quasi-Fermi level splitting and realignment, the researchers demonstrated, ensures fast response and high detectivity by the photodetector.Prof. Seo: “We successfully imaged internal changes in the muscular tissues of the fingers by scan-imaging them with our photodetector.” He explained, “With this device, we will be able to detect [the locations of] body aches and pain and image them at ultra-high speed. We expect the photodetector will be applied to scanning and diagnosing various other types of changes occurring not just in muscles, but in other parts of the body as well, particularly for pediatric patients.”The team’s research project was made possible in part thanks to the Program for the Future New Material and Original Technology Development Program and the Basic Research Support Program for Experienced Researchers, both from the Ministry of Science and ICT and the National Research Foundation of Korea. A patent application on the invention is now pending.
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- 작성자OI***
- 작성일2020-12-18
- 3497
- 동영상동영상
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A team of researchers including Ajou’s own Prof. Hwang Jon-kook (Department of Chemical Engineering) has developed a new original technology for controlling the shapes of porous nanomaterials. The team’s discovery is expected to help solve current roadblocks to innovation in various fields, including secondary cells and energy storage systems, as well as energy, catalysts, environmental engineering, and medicine.The article, listing Prof. Hwang as the principal author, was published in the August 12 online issue of Science Advances (IF = 13.116, JCR 4.93%), a sister publication of Science. Dr. Kim Seong-seop and Prof. Lee Jin-woo of the Korea Advanced Institute of Science and Technology (KAIST) were also on the team.The title of the article reads: “Polymer blend directed anisotropic self-assembly toward mesoporous inorganic bowls and nanosheets.”The team has developed a new mechanism which can easily control the shapes of molecules and nanostructures by simply combining and heating an organic polymer blend and an inorganic metal oxide precursor. Furthermore, the team demonstrated that the dish-shaped niobium oxide created by applying their method offers the highest-possible levels of performance and safety when used as an anode for a potassium ion battery, which garners attention as a potential material for next-generation secondary batteries.Researchers worldwide have so far sought to control the shapes of porous materials through complex and often expensive methods. These methods, however, failed to ensure precise and efficient control of porous nanostructures and particles. Accordingly, there has been growing demand for a new technique that is simpler, less expensive, and more capable of controlling all relevant factors, including size, structure and shape of pores.Prof. Hwang’s team found a solution in the self-assembly effect of multicomponent polymer blends. Multicomponent polymer blends can assemble themselves into complex and sophisticated nanostructures when certain conditions are met. Although this mechanism has long been known in polymer physics, few actual applications have been made out of it.Prof. Hwang’s team established a design guideline that brings together the self-assembly mechanism of multicomponent polymer blends with inorganic material chemistry, and the result—the anisotropically self-assembled particle (ASAP)—was thus born, promising simple and easy ways to control nanostructure, chemical composition and shape of porous materials.Prof. Hwang explains: “Our work is significant in that it demonstrates, for the first time, that self-assembling polymer blends can be used to solve the problem with synthesizing porous inorganic materials.” He adds, “This means that we can now pioneer new fields of interdisciplinary research that connect polymer physics and inorganic material chemistry.”As a nanoenergy and material specialist, Prof. Hwang has long been researching ways to control the structures and shapes of porous nanomaterials. His future research plans include finding simple methods for synthesizing inorganic porous materials and producing customized designs for electrodes of next-generation secondary batteries.*Pictured: A diagram of ASAP, a porous inorganic material using the self-assembly of a multicomponent polymer blend.
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- 작성자OI***
- 작성일2020-12-18
- 3129
- 동영상동영상
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A team of researchers with the participation of Ajou Professor Park Dae-chan (Department of Biological Sciences) has found a new clue to preventing disruptions to the placenta, vital to fetal growth and nutrition. The team’s discovery of a new factor critical to placental development is expected to catalyze development of new solutions to ensure early fetal health.The team’s article, published in the July 31 online issue of Nucleic Acids Research (Impact factor: 11.501, IF% = 4.882), was entitled, “The chromatin-binding protein PHF6 functions as an E3 ubiquitin ligase of H2BK120 via H2BK12Ac recognition for activation of tophectoderman genes.” The team also included Prof. Baek Sung-hee of Seoul National University and Prof. Lee Ji-min of Kangwon National University.The team discovered the importance of an epigenetic factor known as PHF6 in the trophectoderm of the blastocyst in placental formation. Blastocysts are sphere-shaped bundles of cells that contain embryonic stem cells, surrounded by trophectoderms. Trophectoderms form the embryo and the placenta, and how epigenetic factors regulate trophectodermal differentiation has not been understood until now.Based on an mRNA-sequencing genomic analysis, an emerging method for analyzing nucleic sequences, Prof. Park’s team discovered that embryonic stem cells from which PHF6 was removed led to disruptions in the formation of blastocysts and the placenta.PHF6 is an epigenetic factor protein that recognizes histone modifications. The team found that PHF6, by recognizing the chemical modifications (acetyl group) to histone proteins surrounding DNA, additionally binds ubiquitin to the histone. In other words, the researchers confirmed that histone modifications by PHF6 is what regulates the expression of trophectodermal genes in blastocysts.The team explained: “We have demonstrated that it is possible to modify the placental developmental process epigenetically using histone proteins that are dissolved and resynthesized in just days, instead of modifying the DNA nucleic sequences transmitted down the generations.”The research was made possible with the help of the Ministry of Science and ICT (MSIT) and the National Research Foundation of Korea (NRF)’s Leading Research Support, Individual Basic Science and Engineering Research, and New Researcher Support Programs.
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- 작성자OI***
- 작성일2020-12-18
- 3061
- 동영상동영상
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A cover image of Chemical Reviews. ©ACS Publications.An article by a team of international researchers, which included Professor Kwak Won-jin (Department of Chemistry/Department of Energy System Research (Graduate)), was published as the cover article for the July 22 online issue of Chemical Reviews.The article, for which Prof. Kwak is a principal author, concerns lithium-oxygen batteries, a next-generation secondary battery system garnering attention worldwide. The team of researchers included Prof. Sun Yang-kook of Hanyang University, Korea; Prof. Doron Aurbach of Bar-Ilan University, Israel; Prof. Peter Bruce of the University of Oxford; and Prof. Linda Nazar of Waterloo University, Canada. Chemical Reviews, published by the American Chemical Society (ACS), is the top-ranked journal in the entire field of chemistry.In the article entitled “Lithium-Oxygen Batteries and Related Systems: Potential, Status, and Future,” Prof. Kwak and his colleagues introduce the findings of their years-long research into the structure of the lithium-oxygen battery, its working mechanism, and related derivative systems. The researchers also discuss the core issues and recent trends in research on the lithium-oxygen battery, and needed practical improvements.A next-generation secondary battery system capable of utilizing oxygen in the air as fuel, the lithium-oxygen battery holds the potential to surpass the theoretical energy density limit of the lithium ion battery used in electric vehicles. Research has abounded on the topic as a result, but there are also considerable obstacles that compromise its commercial viability, such as its short lifecycle as a side effect of reacting with oxygen, its low energy efficiency due to the inevitable creation and dissolution of byproducts. Innovative solutions to these problems are needed.Prof. Kwak explains: “It is exceedingly difficult to improve the lithium oxygen battery’s energy efficiency and reversibility to a viable level, as there are a number of complex factors involved,” adding, “But, insofar as the demand for high-energy-density battery systems continues to grow, we should continue rising to the challenge.”Prof. Kwak will continue his research on the lithium oxygen battery in his new faculty position in the Department of Chemistry at Ajou University, where he was appointed in the spring semester. He has published a number of articles in this year, addressing issues with the lithium oxygen battery and possible solutions.
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- 작성자OI***
- 작성일2020-12-18
- 3121
- 동영상동영상
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Scientists develop a novel photoelectronic device that can sense and map muscle strain remotely within microseconds, with no harmful effectsScientists from Ajou University in Korea have developed a novel highly sensitive photoelectric device that can generate noticeably different alternating currents upon illumination with even slightly varied wavelengths of near-infrared light. Since near-infrared light can deeply penetrate muscles and tissues with no adverse effects, this device could be used to remotely and harmlessly pinpoint body aches and muscle strain real time, replacing standard X-ray imaging techniques that could be harmful. The new near-infrared light–based device can help in real-time identification of body aches and muscle strainPicture credit: Hyungtak Seo, Ajou UniversityThe photovoltaic effect, in which a material generates an electric current upon exposure to light (photons), is one of the cornerstones of optoelectronics, and the principle of operation of important technological advances such as solar cells. Optoelectronic devices have found a wide range of applications in fields such as energy harvesting, communication, and imaging, but their impact in the medical field has been limited. A major roadblock has been the poor performance of affordable optoelectronic devices under light at near-infrared frequencies. The utility of near-infrared light in medicine was discovered amid efforts to find alternatives to x-ray imaging techniques, which increase the risk of cancer. Near-infrared light penetrates deep into tissues with no harmful consequences and minimal absorption, making it potentially useful in sensing and imaging. Now, a team of scientists at Ajou University, Korea, led by Professor Hyungtak Seo, has developed a novel device that can make near-infrared-based tissue imaging a commercial reality. Their study is published in Elsevier’s Nano Energy. Through a scalable and customizable fabrication process, Prof Seo and team grew a titanium oxide (TiO2) thin film on a silicon substrate. Because of its structure, the device generates an easily detectable alternating current (AC) upon illumination with periodically pulsed light. After an array of varied experiments, the team gained deeper insight into the mechanism underlying this AC photovoltaic effect. Prof Seo explains: “This phenomenon is caused by quasi-Fermi level splitting and rearrangement, which is essentially a perturbation in the equilibrium of charge carriers in the conduction and valence bands due to incident light.” The absorption coefficient of human bio-architecture (bones, muscle, skin, body fluid, etc.) in the NIR range is trivial and, thus, can provide beneficial information. Because transmitted NIR intensity depends on bio-architecture density, it can be expected to change after passing through damaged, strained, or irregular bio-architecture, which could be reflected in the device response.Picture credit: Hyungtak Seo, Ajou UniversityIn their paper, the scientists present a proof-of-concept demonstration of the applicability of their device to mapping body aches and muscle damage. When pulsed near-infrared radiation is passed through first a normal and then a strained muscle, the change in muscle shape causes a change in the light emitted by the muscle, which was then detected by the device. The device responds to these changes by generating different currents for each wavelength within microseconds. Excited about the results, Prof Seo remarks: “Considering that body aches are a common symptom of COVID-19 and other diseases, pinpointing them using optoelectronic devices could be essential in clinical settings, especially for kids, who often cannot express their pain.”Schematic representation of the novel photoelectric device Picture credit: Hyungtak Seo, Ajou UniversityMoreover, the device does not require an external voltage to operate, making it highly energy efficient, and its fabrication is possible with relatively simple existing techniques. To top it all, it functions not only in the near-infrared part of the spectrum but also in the visible and ultraviolet regions. Thus, Prof Seo and team believe that the commercialization of this technology should be straightforward, and it could easily find a home in the medical field, optical communication, digital displays, and sensing applications. Further research will certainly unlock its full potential, making our lives better!ReferenceAuthors:Mohit Kumar1, Hyobin Choi2, Jaeseong Lim2, Ji-Yong Park3, Sangwan Kim4*,Hyungtak Seo1,2*Title of original paper:Broadband alternating current photovoltaic effect: An application for high-performance sensing and imaging body achesJournal:Nano EnergyDOI:10.1016/j.nanoen.2020.105240Affiliations:1Department of Materials Science and Engineering, Ajou University 2Department of Energy Systems Research, Ajou University 3Department of Physics, Ajou University4Department of Electrical and Computer Engineering, Ajou University*Corresponding authors’ emails: hseo@ajou.ac.kr (H. Seo) About the authorProf. Hyungtak Seo received a Ph.D. in 2008 from North Carolina State University, USA, and worked at Lawrence Berkeley National Laboratory until September 2011. Since 2011, he has been a Professor at Ajou University, where he is the PI of the Advanced Electronic & Energy Materials (AEEM) Laboratory. His current interests are in (i) fabricating nano-materials for solar cells and photocatalysis applications; (ii) designing materials/devices for next-generation integrated circuit neuromorphic devices; (iii) tuning the electronic properties of nanoscale semiconductors for electrical and energy applications; (iv) and analyzing the properties of functional materials via UPS, XPS, ellipsometry, etc.
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- 작성자통합 관리자
- 작성일2020-11-10
- 4563
- 동영상동영상
