본문 바로가기
대메뉴 바로가기
KAIST
Newsletter Vol.23
Receive KAIST news by email!
View
Subscribe
Close
Type your e-mail address here.
Subscribe
Close
KAIST
NEWS
유틸열기
홈페이지 통합검색
-
검색
KOREAN
메뉴 열기
Micro
by recently order
by view order
KAIST Made Great Improvements of Nanogenerator Power Efficiency
The energy efficiency of a piezoelectric nanogenerator developed by KAIST has increased by almost 40 times, one step closer toward the commercialization of flexible energy harvesters that can supply power infinitely to wearable, implantable electronic devices. NANOGENERATORS are innovative self-powered energy harvesters that convert kinetic energy created from vibrational and mechanical sources into electrical power, removing the need of external circuits or batteries for electronic devices. This innovation is vital in realizing sustainable energy generation in isolated, inaccessible, or indoor environments and even in the human body. Nanogenerators, a flexible and lightweight energy harvester on a plastic substrate, can scavenge energy from the extremely tiny movements of natural resources and human body such as wind, water flow, heartbeats, and diaphragm and respiration activities to generate electrical signals. The generators are not only self-powered, flexible devices but also can provide permanent power sources to implantable biomedical devices, including cardiac pacemakers and deep brain stimulators. However, poor energy efficiency and a complex fabrication process have posed challenges to the commercialization of nanogenerators. Keon Jae Lee, Associate Professor of Materials Science and Engineering at KAIST, and his colleagues have recently proposed a solution by developing a robust technique to transfer a high-quality piezoelectric thin film from bulk sapphire substrates to plastic substrates using laser lift-off (LLO). Applying the inorganic-based laser lift-off (LLO) process, the research team produced a large-area PZT thin film nanogenerators on flexible substrates (2cm x 2cm). “We were able to convert a high-output performance of ~250 V from the slight mechanical deformation of a single thin plastic substrate. Such output power is just enough to turn on 100 LED lights,” Keon Jae Lee explained. The self-powered nanogenerators can also work with finger and foot motions. For example, under the irregular and slight bending motions of a human finger, the measured current signals had a high electric power of ~8.7 μA. In addition, the piezoelectric nanogenerator has world-record power conversion efficiency, almost 40 times higher than previously reported similar research results, solving the drawbacks related to the fabrication complexity and low energy efficiency. Lee further commented, “Building on this concept, it is highly expected that tiny mechanical motions, including human body movements of muscle contraction and relaxation, can be readily converted into electrical energy and, furthermore, acted as eternal power sources.” The research team is currently studying a method to build three-dimensional stacking of flexible piezoelectric thin films to enhance output power, as well as conducting a clinical experiment with a flexible nanogenerator. This research result, entitled “Highly-efficient, Flexible Piezoelectric PZT Thin Film Nanogenerator on Plastic Substrates,” was published as the cover article of the April issue of Advanced Materials. (http://onlinelibrary.wiley.com/doi/10.1002/adma.201305659/abstract) YouTube Link: http://www.youtube.com/watch?v=G_Fny7Xb9ig Over 100 LEDs operated by self-powered flexible piezoelectric thin film nanogenerator Flexible PZT thin film nanogenerator using inorganic-based laser lift-off process Photograph of large-area PZT thin film nanogenerator (3.5cm × 3.5cm) on a curved glass tube and 105 commercial LEDs operated by self-powered flexible piezoelectric energy harvester
2014.05.19
View 12124
Immune Evasion Mechanism of Hepatitis C Virus Revealed
Professor Ui-Cheol Shin Inhibiting major histocompatibility complex [MHC] class I protein expression, T cell immune response is evaded. The research will be a great help to the development of C hepatitis vaccine. Roughly 1-2% of the population in Korea is known to be infected with Hepatitis C. Most Hepatitis C Virus (HCV) infections progress to a chronic disease and can cause liver cirrhosis or liver cancer, which may lead to death. Unlike Hepatitis type A or B, there is no vaccine for Hepatitis C Virus and therefore avoiding exposure to the virus is the best known method of prevention. However, a team of researchers at KAIST has produced research results, which may contribute significantly to the vaccine development. KAIST Graduate School of Medical Sciences & Engineering’ Professor Ui-Cheol Shin and his team have successfully identified why Hepatitis C Virus does not cause an immune response within the human body. The research results were published in the May edition of The Journal of Gastroenterology, a world-renowned journal in the field of gastroenterology. The immune response occurs to eliminate the virus that has invaded our body. During this process, a major histocompatibility complex [MHC] class I plays a key role in inducing T cell response, which is needed for the elimination of virus-infected cells. When a cell is infected by a virus, a substance called interferon causes the increased expression of major histocompatibility complex class I. T cell recognizes the increased MHC class I and therefore finds the virus-infected cells. However, the effect that Hepatitis C Virus has on major histocompatibility complex class I has not been clearly identified until now. The research team has revealed, using a cell culture for infection systems, that the Hepatitis C Virus suppresses the expression of major histocompatibility complex class I. Also, the mechanism to prove that HCV activates a protein called PKR within the cell to inhibit MHC class I protein expression was identified at a molecular level. In this study, researchers established the hypothesis that regulating PKR protein in the cell can enhance the T cell immune response, which was then proved through experiments. Professor Ui-Cheol Shin said, “There are a lot of new drugs to treat Hepatitis C Virus, while its vaccine has not been developed yet. Revealing the HCV immune evasion mechanism will help stimulate momentum for the HCV vaccine development.” The first author of the journal, Dr. Won-Seok Kang is a graduate from Yonsei College of Medicine. After earning his medical degree, he has continued his training as a ‘doctor-scientist’ at KAIST Graduate School of Medical Sciences & Engineering to study Hepatitis C Virus immune evasion mechanism in this research. Hepatitis C Virus activates PKR-eIF2a pathway, which inhibits the major histocompatibility complex class I, and therefore weakens the T cell activation to the viral activity.
2014.05.19
View 9584
Mechanism in regulation of cancer-related key enzyme, ATM, for DNA damage and repair revealed
Professor Kwang-Wook Choi A research team led by Professor Kwang-Wook Choi and Dr. Seong-Tae Hong from the Department of Biological Sciences at KAIST has successfully investigated the operational mechanism of the protein Ataxia Telangiectasia Mutated (ATM), an essential protein to the function of a crucial key enzyme that repairs the damaged DNA which stores biometric information. The results were published on December 19th Nature Communications online edition. All organisms, including humans, constantly strive to protect the information within their DNA from damages posed by a number of factors, such as carbonized materials in our daily food intake, radioactive materials such as radon emitting from the cement of buildings or ultraviolet of the sunlight, which could be a trigger for cancer. In order to keep the DNA information safe, the organisms are always carrying out complex and sophisticated DNA repair work, which involves the crucial DNA damage repair protein ATM. Consequently, a faulty ATM leads to higher risks of cancer. Until now, academia predicted that the Translationally Controlled Tumor Protein (TCTP) will play an important role in regulating the function of ATM. However, since most of main research regarding TCTP has only been conducted in cultured cells, it was unable to identify exactly what mechanisms TCTP employs to control ATM. The KAIST research team identified that TCTP can combine with ATM or increase the enzymatic activity of ATM. In addition, Drosophilia, one of the most widely used model organisms for molecular genetics, has been used to identify that TCTP and ATM play a very important role in repairing the DNA damaged by radiation. This information has allowed the researchers to establish TCTP’s essential function in maintaining the DNA information in cell cultures and even in higher organisms, and to provide specific and important clues to the regulation of ATM by TCTP. Professor Kwang-Wook Choi said, “Our research is a good example that basic research using Drosophilia can make important contributions to understanding the process of diseases, such as cancer, and to developing adequate treatment.” The research has been funded by the Ministry of Science, ICT and Future Planning, Republic of Korea, and the National Research Foundation of Korea. Figure 1. When the amount of TCTP protein is reduced, cells of the Drosophila's eye are abnormally deformed by radiation. Scale bars = 200mm Figure 2. When the amount of TCTP protein is reduced, the chromosomes of Drosophilia are easily broken by radiation. Scale bars = 10 mm. Figure 3. When gene expressions of TCTP and ATM are reduced, large defects occur in the normal development of the eye. (Left: normal Drosophilia's eye, right: development-deficient eye) Figure 4. ATM marks the position of the broken DNA, with TCTP helping to facilitate this reaction. DNA (blue line) within the cell nucleus is coiled around the histone protein (green cylinder). When DNA is broken, ATM protein attaches a phosphate group (P). Multiple DNA repair protein recognizes the phosphate as a signal that requires repair and gathers at the site.
2014.01.07
View 10239
Nanowire Made of Diverse Materials May Become Marketable
- Technology to commercialize nanowire developed after 2 years of industrial-academic joint research - - 2 million strands of 50nm-width, 20 cm-length nanowire mass producible in 2 hours – A South Korean joint industrial-academic research team has developed the technology to put forward the commercialization of nanowire that is only a few nanometers wide. It is expected to be applied in various fields such as semiconductors, high performance sensors, and biodevices. In cooperation with LG Innotek and the National Nanofab center, Professor Jun-Bo Yoon, from KAIST Department of Electrical Engineering, developed the technology to mass produce nanowire at any length with various materials. The research results are published on the online edition of Nano Letters on July 30th. Nanowire has a long linear structure with its width at 100 nanometers at maximum. It is a multifunctional material that has yet undiscovered thermal, electric, and mechanical properties. Nanowire is highly acclaimed as a cutting-edge material with unique nano-level properties that can be applied in semiconductors, energy, biodevices, and optic devices. Previously, nanowires had an extremely low synthesis rate that required three or four days to grow few millimeters. It was therefore difficult to produce the desired products using nanowires. Moreover, nanowires needed to be evenly arranged for practical application, but the traditional technology required complex post-treatment, not to mention the arrangement was not immaculate. The research team applied semiconductor process instead of chemical synthesis to resolve these issues. The team first formed a pattern greater that of the target frequency by using a photo-engraving process on a silicon wafer board whose diameter was 20 centimeters, then repeatedly reduced the frequency to produce 100 nm ultrafine linear grid pattern. Based on this pattern, the research team applied the sputtering process to mass-produce nanowires in perfect shapes of 50 nm width and 20 cm maximum length. The new technology requires neither a lengthy synthesis process nor post-cleaning to attain a perfectly aligned state. Thus, academic and industrial circles consider the technology has high possibilities for commercialization. “The significance is in resolving the issues in traditional technology, such as low productivity, long manufacturing time, restrictions in material synthesis, and nanowire alignment,” commented Professor Yoon on this research. “Nanowires have not been widely applied in the industry, but this technology will bring forward the commercialization of high performance semiconductors, optic devices, and biodevices that make use of nanowires.”
2013.10.18
View 7447
A KAIST research team developed in vivo flexible large scale integrated circuits
Daejeon, Republic of Korea, May 6th, 2013–-A team led by Professor Keon Jae Lee from the Department of Materials Science and Engineering at KAIST has developed in vivo silicon-based flexible large scale integrated circuits (LSI) for bio-medical wireless communication. Silicon-based semiconductors have played significant roles in signal processing, nerve stimulation, memory storage, and wireless communication in implantable electronics. However, the rigid and bulky LSI chips have limited uses in in vivo devices due to incongruent contact with the curvilinear surfaces of human organs. Especially, artificial retinas recently approved by the Food and Drug Administration (refer to the press release of FDA"s artificial retina approval) require extremely flexible and slim LSI to incorporate it within the cramped area of the human eye. Although several research teams have fabricated flexible integrated circuits (ICs, tens of interconnected transistors) on plastics, their inaccurate nano-scale alignment on plastics has restricted the demonstration of flexible nano-transistors and their large scale interconnection for in vivo LSI applications such as main process unit (MPU), high density memory and wireless communication. Professor Lee"s team previously demonstrated fully functional flexible memory using ultrathin silicon membranes (Nano Letters, Flexible Memristive Memory Array on Plastic Substrates), however, its integration level and transistor size (over micron scale) have limited functional applications for flexible consumer electronics. Professor Keon Jae Lee"s team fabricated radio frequency integrated circuits (RFICs) interconnected with thousand nano-transistors on silicon wafer by state-of-the-art CMOS process, and then they removed the entire bottom substrate except top 100 nm active circuit layer by wet chemical etching. The flexible RF switches for wireless communication were monolithically encapsulated with biocompatible liquid crystal polymers (LCPs) for in vivo bio-medical applications. Finally, they implanted the LCP encapsulated RFICs into live rats to demonstrate the stable operation of flexible devices under in vivo circumstances. Professor Lee said, "This work could provide an approach to flexible LSI for an ideal artificial retina system and other bio-medical devices. Moreover, the result represents an exciting technology with the strong potential to realize fully flexible consumer electronics such as application processor (AP) for mobile operating system, high-capacity memory, and wireless communication in the near future." This result was published in the May online issue of the American Chemical Society"s journal, ACS Nano (In vivo Flexible RFICs Monolithically Encapsulated with LCP). They are currently engaged in commercializing efforts of roll-to-roll printing of flexible LSI on large area plastic substrates. Movie at Youtube Link: Fabrication process for flexible LSI for flexible display, wearable computer and artificial retina for in vivo biomedical application http://www.youtube.com/watch?v=5PpbM7m2PPs&feature=youtu.be Applications of in Vivo Flexible Large Scale Integrated Circuits Top: In vivo flexible large scale integrated circuits (LSI); Bottom: Schematic of roll-to-roll printing of flexible LSI on large area plastics.
2013.06.09
View 10935
Professor Lee Jeong Yong Receives 2012 'KAISTian of the Year' Award
Professor Lee Jeong Yong (Department of Material Science and Engineering) received the 2012 ‘KAISTian of the Year’ Award. Professor Lee had successfully developed a technique that allowed the observation and analysis of liquid in atomic scale. The technique is expected to have great impact on nano-material synthesis in solution, explaining electrode and electrolyte reaction, liquid and catalysis reaction research, and etc. and was therefore named as the best experimental accomplishment in KAIST in 2012. Professor Lee and his team’s finding has been published in the April edition of Science magazine and has had attracted the attention of the world. In addition, BBC News, and Science & Environment reported on the findings as their respective top articles. The optical microscope is incapable of atomic scale observation and the electron microscopes are capable but because of the vacuum state all liquids undergo evaporation making it impossible to observe liquids in an atomic scale. Professor Lee’s team wrapped the liquid with a layer of grapheme to prevent evaporation and successfully observed real time the platinum growth process in solution. Professor Lee’s findings were introduced as an example of exemplar research case in the Presidential address for ‘Science Day’ in April.
2013.01.22
View 7357
Professor Cho Young-ho wins 'E2 Star' award
Professor Cho Young-ho from the Department of Bio and Brain Engineering at KAIST was chosen as the ‘E2 Star’ at the ‘2012 Engineering Education Festa’ in academics. The ‘2012 Engineering Education Festa’ hosted by the Ministry of Education, Science and Technology was held to display outstanding research results and to conceptualize the future of science education. The ‘E2 star’ award is given to renowned figures in industry, academia and society. A total of 35 candidates were recommended for the 3 fields and Professor Cho received the first place in the online voting. Professor Cho received high marks for his work in engineering education, research development and increasing the communication between academia and industry, as well as the commercialization of science and technology. Professor Cho was especially praised for the specialization of engineering education in integrated fields and the joint research with US and Swiss universities. Professor Cho Young-ho(Department of Bio and Brain Engineering, KAIST)
2012.12.26
View 8331
Flexible Nanogenerator Technology
KAIST research team successfully developed the foundation technology that will enable to fabrication of low cost, large area nanogenerator. Professor Lee Gun Jae’s team (Department of Materials Science and Engineering) published a dissertation on a nanogenerator using nanocomplexes as the cover dissertation of the June edition of Advanced Materials. The developed technology is receiving rave reviews for having overcome the complex and size limitations of the nanogenerator fabrication process. A nanogenerator is an electricity generator that uses materials in the nanoscale and uses piezoelectricity that creates electricity with the application of physical force. The generation technology using piezoelectricity was appointed as one of top 10 promising technologies by MIT in 2009 and was included in the 45 innovative technologies that will shake the world by Popular Science Magazine in 2010. The only nanogenerator thus far was the ZnO model suggested by Georgia Tech’s Professor Zhong Lin Wang in 2005. Professor Lee’s team used ceramic thin film material BaTiO3 which has 15~20 times greater piezoelectric capacity than ZnO and thus improved the overall performance of the device. The use of a nanocomplex allows large scale production and the simplification of the fabrication process itself. The team created a mixture of PDMS (polydimethylsiloxane) with BaTiO3 and either of CNT (Carbon Nanotube) or RGO (Reduced Graphene Oxide) which has high electrical conductivity and applied this mixture to create a large scale nanogenerator.
2012.06.18
View 10833
High-resolution Atomic Imaging of Specimens in Liquid Observed by Transmission Electron Microscopes Using Graphene Liquid Cells
Looking into specimens in liquid at the atomic level to understand nanoscale processes so far regarded as impossible to witnessThe Korea Advanced Institute of Science and Technology (KAIST) announced that a research team from the Department of Materials Science and Engineering has developed a technology that enables scientists and engineers to observe processes occurring in liquid media on the smallest possible scale which is less than a nanometer. Professor Jeong Yong Lee and Researcher Jong Min Yuk, in collaboration with Professors Paul Alivisatos’s and Alex Zettl’s groups at the University of California, Berkeley, succeeded in making a graphene liquid cell or capsule, confining an ultra-thin liquid film between layers of graphene, for real-time and in situ imagining of nanoscale processes in fluids with atomic-level resolution by a transmission electron microscope (TEM). Their research was published in the April 6, 2012 issue of Science. (http://www.sciencemag.org/content/336/6077/61.abstract) The graphene liquid cell (GLC) is composed of two sheets of graphene sandwiched to create a sealed chamber where a platinum growth solution is encapsulated in the form of a thin slice. Each graphene layer has a thickness of one carbon atom, the thinnest membrane that has ever been used to fabricate a liquid cell required for TEM. The research team peered inside the GLC to observe the growth and dynamics of platinum nanocrystals in solution as they coalesced into a larger size, during which the graphene membrane with the encapsulated liquid remained intact. The researchers from KAIST and the UC Berkeley identified important features in the ongoing process of the nanocrystals’ coalescence and their expansion through coalescence to form certain shapes by imaging the phenomena with atomic-level resolution. Professor Lee said, “It has now become possible for scientists to observe what is happening in liquids on an atomic level under transmission electron microscopes.” Researcher Yuk, one of the first authors of the paper, explained his research work. “This research will promote other fields of study related to materials in a fluid stage including physical, chemical, and biological phenomena at the atomic level and promises numerous applications in the future. Pending further studies on liquid microscopy, the full application of a graphene-liquid-cell (GLC) TEM to biological samples is yet to be confirmed. Nonetheless, the GLC is the most effective technique developed today to sustain the natural state of fluid samples or species suspended in the liquid for a TEM imaging.” The transmission electron microscope (TEM), first introduced in the 1930s, produces images at a significantly higher resolution than light microscopes, allowing users to examine the smallest level of physical, chemical, and biological phenomena. Observations by TEM with atomic resolution, however, have been limited to solid and/or frozen samples, and thus it has previously been impossible to study the real time fluid dynamics of liquid phases. TEM imaging is performed in a high vacuum chamber in which a thin slice of the imaged sample is situated, and an electron beam passes through the slice to create an image. In this process, a liquid medium, unlike solid or frozen samples, evaporates, making it difficult to observe under TEM. Attempts to produce a liquid capsule have thus far been made with electron-transparent membranes of such materials as silicon nitride or silicon oxide; such liquid capsules are relatively thick (tens to one hundred nanometers), however, resulting in poor electron transmittance with a reduced resolution of only a few nanometers. Silicon nitride is 25 nanometers thick, whereas graphene is only 0.34 nanometers. Graphene, most commonly found in bulk graphite, is the thinnest material made out of carbon atoms. It has unique properties such as mechanical tensile strength, high flexibility, impermeability to small molecules, and high electrical conductivity. Graphene is an excellent material to hold micro- and nanoscopic objects for observation in a transmission electron microscope by minimizing scattering of the electron beam that irradiates a liquid sample while reducing charging and heating effects. ### Figure 1. Schematic illustration of graphene liquid cells. Sandwiched two sheets of graphene encapsulate a platinum growth solution. Figure 2. In-situ TEM observation of nanocrystal growth and shape evolution. TEM images of platinum nanocrystal coalescence and their faceting in the growth solution.
2012.04.23
View 10310
Prof. Park to Receive HP's Annual Innovation Research Award
Prof. In-Kyu Park of the Department of Mechanical Engineering, KAIST, has been will receive an award from Hewlett-Packard"s second annual Labs Innovation Research Program, university authorities said on Wednesday (July 8). Prof. Park was chosen as the winner of the research award for his paper entitled "Eco-friendly nanomanufacturing for intelligent environment sensing applications." Sixty projects from 46 universities in 12 countries were selected as the recipients of the awards from HP Labs, the company"s central research arm. The program is designed to create opportunities for colleges, universities and research institutes to conduct collaborative research with HP. HP Labs Innovation Research Awards provide project funding of up to $100,000 for one year to each of the chosen academic institutions, which is renewable for up to three years based on research progress and HP business requirements. Prof. Park has conducted joint researches on nanoimprinting, nanosensors, and nanoelectronics with HP"s Information and Quantum Systems Lab since 2005. Starting from the later half of 2009, he is to receive research grants under the industry-academia cooperation program of the world"s information technology giant firm.
2009.07.09
View 11275
<<
첫번째페이지
<
이전 페이지
1
2
>
다음 페이지
>>
마지막 페이지 2