research
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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.
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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 11375 -
Paving the Way to Next Generation Display
A new type of LCD that does not require polymer orientation films has been developed by researchers within the country. This technology will enable the creation of thiner and higher definition display.
Prof. Hee Tae Jung form KAIST’s biochemical engineering department led the research and Hyun Soo Jung, Hwan Jin Jeon doctoral students (1st co-authors), Doctor Yun Ho Kim from Korea Chemistry Research Center, and Prof. Shin Woong Kang from Jeon Buk University ( co-author) have participated in this research. This research has been funded by the WCU program and middle-grade researcher support program. The results of the research has been published as the online update of ‘‘Nature Asia Materials(NPG Asia Materials)” which is a sister magazine of the world renowned academic magazine ‘Nature’.
The flat display industry is the core industry leading the 21st century’s IT industry. The LCD is the main area of research. Korea is the leader of this industry, holding more than 50% of the world market. Many technologies are combined to make the electro-optic devices of the LCD function. The most important technology, which determines the indicating element’s quality and function is the technology to align the liquid crystals in one direction.
Currently, all LCD products are created by mechanically cutting into the surface of the polymer film and orienting the liquid crystal material along these cuts. However, the creation of polymer orientation films cost much time and money, and the high temperature processes necessary to stabilize the polymers does not allow for the free selection of circuit boards, and thus does not allow for the use in flexible display.
Prof. Hee Tae Jung devised a method to orient liquid display without the use of a polymer film using ITOs. Prof. Jung’s base technology has been tested on ITOs to maintain the necessary transparency and conductivity after forming a pattern with high decomposition rates and slenderness ratios.
The technology developed by the research team can horizontally or vertically align the transparent conductors without the use of polymer orientation films. Thus, the manufacturing processes have become much shortened and the LCDs can be made in much thinner from a few micrometers to a few centimeters. Also, it has a lower functioning voltage and faster response speed, showing the prospects of a high definition ultra-fast screen display development. Furthermore, this technology can be used for any type of board, and can be adjusted to a nanometer scale. This enables for its use in LCD based flexible or multi-domain modes.
Also, the transparent conductor patterning technology devised by the research team can be used not only for displays, but also for touch panels with highly increased sensitivity.
Prof. Jung said, “It was a long desire of the industry and academia to find a way to replace the polymer orientation film. This new technology does not need any polymer orientation films, and we can still use the original boards used for LCDs. This mean a lot to the industry. Also, this technology will increase the sensitivity of the touch panels for tablet PCs and smart phones. It can be used in many areas of future electronics base technology.”
2012.04.04 View 9833 -
Inexpensive Separation Method of Graphene Developed
The problem with commercializing graphene that is synthesized onto metals over a wide area is that it can not be separated from the metal. However, a groundbreaking separation technology which is both cheap and environment friendly has been developed.
Prof. Taek soo Kim and Prof. Byung Jin Cho"s research teams have conducted this research under the support of the Global Frontier program and Researcher Support Program initiated by The Ministry of Education and Science and Korea Research Foundation. The research results have been posted on the online news flash of Nano Letters on februrary 29th. (Thesis title: Direct Measurement of Adhesion Energy of Monolayer Graphene As-Grown on Copper and Its Application to Renewable Transfer Process)
The research has generated exact results on the interfacial adhesive energy of graphene and its surface material for the first time. Through this, the catalyst metal are no longer to be used just once, but will be used for an infinite number of times, thereby being ecofriendly and efficient.
Wide area graphine synthesized onto the catalyst meatal are used in various ways such as for display and for solar cells. There has been much research going on in this field. However, in order to use this wide area graphene, the graphene must be removed from the catalyst metal without damage.
Until now, the metal had been melted away through the use of chemical substances in order to separate the graphene. However, this method has been very problematic. The metal can not be reused, the costs are very high, much harmful wastes were created in the process of melting the metals, and the process was very complicated.
The research teams of Professors Taek Su Kim and Byung Jin Cho measured the interfacial adhesive energy of the synthesized graphene and learned that it could be easily removed.
Also, the mechanically removed graphene was successfully used in creating molecular electronic devices directly. This has thus innovatively shortened the graphene manufacturing process. Also, it has been confirmed that the metalic board can be reused multiple times after the graphene is removed. A new, ecofriendly and cost friendly method of graphene manufacturing has been paved.
Through this discovery, it is expected that graphene will become easier to manufacture and that the period til the commercialization date of graphene will therefore be greatly reduced
Prof. Cho stated " This reserach has much academical meaning significance in that it has successfully defined the surfacial adhesive energy between the graphene and its catalyst material and it should receive much attention in that it solved the largest technical problem involved in the production of graphene.
2012.04.04 View 12587
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New Era for Measuring Ultra Fast Phenomena: Atto Science Era
Domestic researchers successfully measured the exact status of the rapidly changing Helium atom using an atto second pulse. Thanks to this discovery, many ultrafast phenomena in nature can now be precisely measured. This will lead to an opening of a new "Atto Science" era.
Prof. Nam Chang Hee led this research team and Ph.d Kim Kyung Taek and Prof. Choi Nak Ryul also participated in this research. They have conducted the research under the support of the Researcher Support Program initiated by The Ministry of Education and Science and Korea Research Foundation. The research result was published in the prestigious journal "Physical Review Letters" on March 2nd. (Title: Amplitude and Phase Reconstruction of Electron Wave Packets for Probing Ultrafast Photoionization Dynamics)
Prof. Nam Chang Hee"s research team used atto second pulse to measure the ultrafast photoionization.
His team used atto second X-ray pulse and femto second laser pulse to photoionize Helium atoms, and measure the wave speed of the produced electron to closely investigate the ultrafast photoionization process.
Atom"s photoionization measurement using an atto second pulse was possible using the research team"s high-energy femto second laser and high-performance photo ion measurement device. This research team succeeded in producing the shortest 60 atto second pulse in the world using high-harmonic waves.
The research team used high-power femto second laser to produce atto second high-harmonic pulse from argon gas, used this to photoionize Helium atoms, and measured the ultrafast photoionization of the atoms.
Prof. Nam Chang Hee said, "This research precisely measured the exact status of rapidly changing Helium atoms. I am planning to research on measuring the ultrafast phenomena inside atoms and molecules and controlling the status of the atoms and molecules based on the research result."
2012.04.04 View 9582
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Creation of Synthetic Antibodies: Professor Hak Seong Kim
Synthetics antibodies which can replace antibodies from humans used as ingredients of medicines have been developed. It can increase the costs to 1/100 of the current costs and is much easier to develop. It is expected that the development period will be shortened from 10 years to 5.
Prof. Hak Seong Kim from the Biology department of KAIST conducted a joint research with Prof. Dong Seob Kim to reconstruct proteins and has succeeded.
The synthetic antibody displays much strength in terms of its productivity, structural formation, and bonding capability, and is thus regarded as an ideal protein. It can replace the antigens that are currently in use. It is expected that Korea will therefore be able to lead the world market for protein medicines which is a 192trillion won industry.
The original antibody has been used for not only treating diseases, but also for various other applications in the fields of medical sciences and biology. However, it is produced through a very complex process involving the incubation of animal cells, and is therefore very expensive. Also, most antibodies are already patented by more developed countries, so a high royalty fee must be paid.
Because of this, many countries including Korea has been concentrating on developing biosimilars copying the antibody medicines for which the patents have already expired. This causes Korea to be behind in the development of antibody protein pharmaceuticals.
Prof. Kim’s research team has focused on the face that the protein existing in some eels are not antibodies but functions as one, and has been successful in developing a synthetic antibody.
The synthetic antibody can be mass produced from the colon bacillus, which allows it to be produced at 1/100 the original cost. It is in a module structure which allows the structuring of the antibody into the desired structure, enabling it to be developed into a protein-based medicine within 5 years.
Together with this, the coherence with the important antigens can be easily controlled, thus allowing for highly effective treatments, less side-effects, high security regarding heat and pH, and the immunogen levels being negligeable. This suggests a very high rate of the antibody being converted into a protein based medication.
The synthetic antibody technology has been tested as a sample for the cure for lung diseases and rheumatism and has been proven to be appropriate. Animal testing will be conducted soon.
Prof Kim said “The original antibodies had a small area allowing the bonding with antibodies, creating barriers for raising bonding strength and structuring. The newly created antibody carries only the strengths and will become a new protein based medicine purely created by Korean technology to replace the antibodies currently used in medications.”
Furthermore, he added that, “The synthesized antibody structuring and designing technology will be widely used in the areas of detecting, diagnosing, and analyzing diseases.”
At the same time, this research result has been published in the Feb 10th issue of the PNAS, and has been supported by the future promising pioneer business program held by the Ministry of Education and Technology.
2012.04.04 View 10218
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A Step Closer to Ultra Slim Mobile Phone
Professor Baek Kyung Wook (department of Material Science and Engineering) succeeded in developing an ultra-thin conjugation technique that can perfectly replace the modular contact in electronic devices.
The research team developed a compound material using ultra-fine solder-adhesive film and developed the vertical ultrasonic conjugation process thereby making a reliable utra-thin conjugation.
The developed technique allowed for very thin and reliable conjugation and will be able to replace the socket type connector and is expected to revolutionize the electronic device industry.
In mobile electronic devices like the smartphone, the trend is to incorporate various functional modules like camera, display, touchscreens, etc. in addition to striving for miniaturization of the device.
Recently the problem was the fact that the number of modules within the device was increasing due to the incorporation of various functions, and consequently the volume that these modules took up increased as well, which made miniaturization almost impossible.
Professor Baek‘s team succeeded in improving upon this problem by creating a compound material that has ultra-fine solder particles that can melt to form alloy fusion with the electrode and thermosetting adhesive film that can wrap around the electrode and provide mechanical protection.
The use of this material made it possible to reduce the thickness of the connector by hundredth fold which improved electrical, mechanical properties and highly reliable.
From a processing standpoint the conventional conjugation process involved heating the mechanical block and was therefore hard to manage its production and also consumed 1000W and took up to 15 seconds.
By contrast, Professor Baek’s team’s new process uses only ultrasound to locally heat and melt the conjugation point itself thereby reducing power consumption to 100W and conjugation time to 1~5 seconds.
The technique developed by Professor Baek and Lee Ki Won Doctorate student was awarded Excellent Dissertation Award by world famous journals like the Electronic Components and Technology Conference and is being recognized worldwide.
2012.01.31 View 8816
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Seeing Inside Cells with Fiber Optics
Professor Jiho Park’s research team was successful in receiving minute optical signals from inside the cell using optical nano fibers.
Through the invention of this technology, we can now look inside cells in high resolution without the use of equipment such as endoscopes that damage cells. We will be able to study the biological phenomena within cells, and thus cure diseases more effectively.
Recently, ultra high resolution microscopes have been used to analyze incubated cells. However, because of the need for a very complex and large system, it had been impossible to monitor cells in the less transparent areas of the body in real time.
The research team created the wire with a semiconductor created with tin oxides to be only 100 nanometers in diameter (1nanometer= 1/1billion meters).
The nanowire is connected to the end of the optical fiber, and the light that comes through the optical fiber is transmitted to particular spots in the cell, and the optical signals from the cell are retrieved back from the cell as well
Together with this, based on the fact that nanowires do not damage cells, the research team covered the end of the wire with a photo reactive material and entered this into the cell. They were able to check that the material reacted to light and entered the cell when they transmitted light
Accordingly, this showed the possibilities of the use of this technology as a method of treatment to effectively transfer the medication into the cells.
Prof. Jiho Park stated that “in this research, we only used cells incubated outside the human body, but soon we will use this technology to stimulate and control cells within the body in a minute scale” as well as that “soon, we will be able to study the biological phenomena inside a cell to study diseases and apply this to cure them more effectively”.
This research result has been published in the online publication of ‘Nature Nanotechnology’ on December 18.
This study was done through the cooperation of various schools. Besides Prof. Jiho Park, Prof. Seungman Yang from the Biochemistry department, and Doctor Chuljoon Huh from KAIST, Prof. Yeonho Choi from Biomedical Science department of Korea University, Professor Peidon Yang and Doctor Ruoxue Yan from UC Berkeley’s chemistry department, and Luke Lee from UC Berkeley’s bioengineering department participated in the project.
2012.01.31 View 9080
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Quantum Mechanical Calculation Theory Developed
An Electron Density Functional Calculation Theory, based on the widely used quantum mechanical principles and yet accurate and with shortened calculation period, was developed by Korean research team.
*Electron Density Functional Calculation Theory: Theory that proves that it is possible to calculate energy and properties with only simple wave equations and electron densities.
The research was conducted by Professor Jeong Yoo Sung (Graduate School of EEWS) and Professor William Goddard with support from WCU Foster Project initiated by Ministry of Education, Science and Technology and Korea Research Foundation. The result was published in the Proceedings of the National Academy of Sciences Journal.
The research team corrected the error when performing quantum calculations that arises from the length of calculation time and incorrect assumptions and developed a theory and algorithm that is more accurate and faster. The use of wave equations in quantum mechanical calculations results in high accuracy but there is a rapid increase in calculation time and is therefore difficult to implement in large molecules with hundreds, or thousands of atoms. By implementing a low electron density variable with relatively less calculation work, the size of calculable molecule increases but the accuracy decreases.
The team focused on the interaction between electrons with different spins to improve upon the speed of calculation in the conventional accurate calculation. The team used the fact that the interaction between electrons with different spins increases as it comes closer together in accordance with the Pauli’s Exclusion Principle.
In addition the interaction between electrons are local and therefore can ignore the interactions between far away electrons and still get the total energy value. The team also took advantage of this fact and developed the algorithm that decreased calculation time hundredth fold.
Professor Jeong commented that, “So far most of the domestic achievements were made by focusing on integrative researches by calculation science and material design communities but these involved short time frames. In areas that required lengthy time frames like fundamentals and software development, there was no competitive advantage. However this research is significant in that a superior solution was developed domestically”.
2012.01.31 View 10257
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New LEDs: Large Spectrum of Colors
Professor Yonghun Cho has discovered that LEDs with hexagonal pyramid structures can emit various colors of light.
LEDs, which have been leading the light revolution is a light emitting element that uses the characteristics of semiconductors to emit light upon passing a current, and is being used for lighting, TV, and various signaling devices.
In general, the white LED used for lighting has to be constructed by spraying yellow fluorescent material on a blue LED or by creating a complicated circuit where various LED chips function together.
Prof.Cho’s research team discovered the fact that when a small hexagonal pyramid structure is formed on the semiconductor composing the LED and a current is passed through this, then each side, edge, and point on the pyramid assumes different energies.
Due to the energy differences, lights of bluegreen, yellow, and orange were emitted from the side, edge, and points of the pyramid, respectively. This shows the prospect of displaying white light as well as that of many other colors.
Thus, applying the nanopyramidal structure to LEDs will allow the emission of light with a large spectrum with just the flow of the current, enabling a new type of LED light emitting particles that would display various colors from a single LED chip without the use of a fluorescent material.
Also, originally, LEDs have had limitations to its efficiency because of its structural characteristics where fluorescent materials had to be sprayed on, but the nanopyramidal structures will overcome this structural barrier to create brighter light
2012.01.31 View 7429
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Closer to the Dream: Graphene
A technique that allows easy and larger observation area of graphene’s crystal face was developed by Korean Research Team.
The research team, led by Professor Jeong Hui Tae (KAIST), consists of Doctorate candidate Kim Dae Woo, Dr. Kim Yoon Ho (primary author), Doctorate candidate Jeong Hyun Soo. The research is supported by WCU (World Class Research University) Development Plan, Mid-Aged Researcher Support Business and was published in the online edition of Nature Nanotechnology.
(Dissertation: Direct visualization of large0area graphene domains and boundaries by optical birefringency)
Professor Jeong’s team used the optical property of the liquid display used in LCD to visualize the size and shape of the single crystals along a flat surface. The visualization of the single crystal allowed the measurement of a near theoretical value of electrical conductivity of graphene.
Graphene has great electrical conductivity, transparent, mechanically stable, flexible, and is therefore regarded as the next generation electrical material. However the polycrystalinity of graphene meant that the actual electrical, mechanical properties were lower than the theoretical values. The reason was thought to be because of the size of the crystal faces and boundary structures.
Therefore, in order to create graphene that has good properties, observing the domain and boundary of graphene crystal faces is essential.
The new technique developed by the research team is another step towards commercializing transparent electrodes, flexible display, and electric materials like solar cells.
2012.01.31 View 9548
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Cancer detection from an implantable, flexible LED
Professor Keon Jae Lee
A KAIST research team has developed a new type of biocompatible and bendable GaN LED biosensor.
Daejeon, the Republic of Korea, August 8, 2011—Can a flexible LED conformably placed on the human heart, situated on the corrugated surface of the human brain, or rolled upon the blood vessels, diagnose or even treat various diseases? These things might be a reality in the near future.
The team of Professor Keon Jae Lee (Department of Materials Science and Engineering, KAIST) has developed a new concept: a biocompatible, flexible Gallium Nitride (GaN) LED that can detect prostate cancer.
GaN LED, a highly efficient light emitting device, has been commercialized in LED TVs and in the lighting industry. Until now, it has been difficult to use this semiconductor material to fabricate flexible electronic systems due to its brittleness. The research team, however, has succeeded in developing a highly efficient, flexible GaN LED and in detecting cancer using a flexible LED biosensor.
Prof. Lee was involved in the first co-invention of "High Performance Flexible Single Crystal GaN" during his PhD course at the University of Illinois at Urbana-Champaign (UIUC). This flexible GaN LED biosensor utilized a similar protocol to transfer thin GaN LED films onto flexible substrates, followed by a biocompatible packaging process; the system’s overall potential for use in implantable biomedical applications was demonstrated.
Professor John Roger (Department of Materials Science and Engineering, UIUC) said,
“Bio-integrated LEDs represent an exciting, new technology with strong potential to address important challenges in human health. This present work represents a very nice contribution to this emerging field.”
This paper was published in the online issue of Nano Energy Elsevier Journal (Editor, Prof. Zhong Lin Wang) dated September 16, 2011.
Flexible GaN LED produces blue light.
2011.09.20 View 10543 -
Review of organophosphonate nerve agent remediation and sensing chemistry
Professor David Churchill, Dept. of Chemistry, KAIST
Scientists in Daejeon, South Korea and Lexington, Kentucky (USA) have recently published a review on the subject of nerve agent remediation and probing chemistry (Chemical Reviews, DOI:10.1021/cr100193y). This article endeavored to pursue organophosphonate nerve agent chemistry deeply and comprehensively and to reflect that decontamination / sensing and nerve agents / pesticides are quite inextricable: when one tries to degrade nerve agents one also needs to detect what components are still present “downstream,” etc. Nerve agents and many pesticides also share a common generalized organophosphate / -phosphonate structure.
Also, the use of simulant molecules (mimics) and a consideration of the closely related organophosphonate pesticides were also treated comprehensively in the Review. The authors reached back into the literature when developing some sections to make important connections to the contemporary topics of interest. The review also includes industrial insights.
Kibong Kim, Olga G. Tsay and David G. Churchill of the Department of Chemistry at KAIST and David A. Atwood of the Department of Chemistry of the University of Kentucky endeavored to "make a variety of connections in research strategies and (sub-) fields to present what is still possible, fruitful, practical, and necessary and to facilitate a current comprehensive molecular level understanding of organophosphonate degradation and sensing," Churchill says.
The authors feel that for the time being, researchers in varying research areas “can use this manuscript effectively when considering future research directions.”
2011.09.19 View 8370