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Furniture That Learns to Move by Itself
A novel strategy for displacing large objects by attaching relatively small vibration sources. After learning how several random bursts of vibration affect an object's pose, an optimization algorithm discovers the optimal sequence of vibration patterns required to (slowly but surely) move the object to a specified position. Displacements of large objects induced by vibration are a common occurrence, but generally result in unpredictable motion. Think, for instance, of an unbalanced front-loading washing machine. For controlled movement, wheels or legs are usually preferred.
Professor Daniel Saakes of the Department of Industrial Design and his team explored a strategy for moving everyday objects by harvesting external vibration rather than using a mechanical system with wheels. This principle may be useful for displacing large objects in situations where attaching wheels or complete lifting is impossible – assuming the speed of the process is not a concern.
His team designed vibration modules that can be easily attached to furniture and objects, and this could be a welcomed creation for people with limited mobility, including the elderly. Embedding these vibration modules as part of mass-produced objects may provide a low-cost way to make almost any object mobile.
Vibration as a principle for directed locomotion has been previously applied in micro-robots. For instance, the three-legged Kilobots move thanks to centrifugal forces alternatively generated by a pair of vibrations on two of its legs. The unbalanced weight transforms the robot into a ratchet and the resulting motion is deterministic with respect to the input vibration. To the best of our knowledge, we are the first to add vibratory actuators to deterministically steer large objects regardless of their structural properties.
The perturbation resulting from a particular pattern of vibration depends on a myriad of parameters, including but not limited to the microscopic properties of the contact surfaces. The key challenge is to empirically discover and select the sequence of vibration patterns to bring the object to the target pose.
Their approach is as follows. In the first step we systematically explore the object’s response by manipulating the amplitudes of the motors. This generates a pool of available moves (translations and rotations). We then calculate from this pool the most efficient way (either in terms of length or number of moves) to go from pose A to pose B using optimization strategies, such as genetic algorithms. The learning process may be repeated from time to time to account for changes in the mechanical response, at least for the patterns of vibration that contribute more to the change.
Prototype modules are made with eccentric rotating motors (type 345-002 Precision Microdrive) with a nominal force of 115g, which proved sufficient to shake (and eventually locomote) four-legged IKEA chairs and small furniture such as tables and stools. The motors are powered by NiMH batteries and communicate wirelessly with a low-cost ESP8266 WiFi module. The team designed modules that are externally attached using straps as well as motors embedded in furniture.
To study the general method, the team employed an overhead camera to track the chair and generate the pool of available moves. The team demonstrated that the system discovered pivot-like gaits and others. However, as one can imagine, using a pre-computed sequence to move to a target pose does not end up providing perfect matches. This is because the contact properties vary with location. Although this can be considered a secondary disturbance, it may in certain cases be mandatory to recompute the matrix of moves every now and then. The chair could, for instance, move into a wet area, over plastic carpet, etc.
The principle and application in furniture is called “ratchair” as a portmanteau combining “Ratchet” and “Chair”. Ratchair was demonstrated at the 2016 ACM Siggraph Emerging Technologies and won the DC-EXPO award jointly organized by the Japanese Ministry of Economy, Trade and Industry (METI) and the Digital Content Association of Japan (DCAJ). At the DCEXPO Exhibition, Fall 2016, the work was one of 20 Innovative Technologies and the only non-Japanese contribution.
*This article is from the KAIST Breakthroughs, research newsletter from the College of Engineering.
For more stories of the KAIST Breakthroughs, please visit http://breakthroughs.kaist.ac.kr
http://mid.kaist.ac.kr/projects/ratchair/
http://s2016.siggraph.org/content/emerging-technologies
https://www.dcexpo.jp/ko/15184
Figure 1. The vibration modules embedded and attached to furniture.
Figure 2. A close-up of the vibration module.
Figure 3. A close-up of the embedded modules.
Figure 4. A close-up of the vibration motor.
2017.03.23 View 9542 -
A Transport Technology for Nanowires Thermally Treated at 700 Celsius Degrees
Professor Jun-Bo Yoon and his research team of the Department of Electrical Engineering at KAIST developed a technology for transporting thermally treated nanowires to a flexible substrate and created a high performance device for collecting flexible energy by using the new technology.
Mr. Min-Ho Seo, a Ph.D. candidate, participated in this study as the first author. The results were published online on January 30th in ACS Nano, an international journal in the field of nanoscience and engineering. (“Versatile Transfer of an Ultralong and Seamless Nanowire Array Crystallized at High Temperature for Use in High-performance Flexible Devices,” DOI: 10.1021/acsnano.6b06842)
Nanowires are one of the most representative nanomaterials. They have wire structures with dimensions in nanometers. The nanowires are widely used in the scientific and engineering fields due to their prominent physical and chemical properties that depend on a one-dimensional structure, and their high applicability.
Nanowires have much higher performance if their structure has unique features such as an excellent arrangement and a longer-than-average length. Many researchers are thus actively participating in the research for making nanowires without much difficulty, analyzing them, and developing them for high performance application devices.
Scientists have recently favored a research topic on making nanowires chemically and physically on a flexible substrate and applies the nanowires to a flexible electric device such as a high performance wearable sensor.
The existing technology, however, mixed nanowires from a chemical synthesis with a solution and spread the mixture on a flexible substrate. The resultant distribution was random, and it was difficult to produce a high performance device based on the structural advantages of nanowires. In addition, the technology used a cutting edge nano-process and flexible materials, but this was not economically beneficial. The production of stable materials at a temperature of 700 Celsius degrees or higher is unattainable, a great challenge for the application.
To solve this problem, the research team developed a new nano-transfer technology that combines a silicon nano-grating board with a large surface area and a nano-sacrificial layer process. A nano-sacrificial layer exists between nanowires and a nano-grating board, which acts as the mold for the nano-transfer. The new technology allows the device undergo thermal treatment. After this, the layer disappears when the nanowires are transported to a flexible substrate.
This technology also permits the stable production of nanowires with secured properties at an extremely high temperature. In this case, the nanowires are neatly organized on a flexible substrate. The research team used the technology to manufacture barium carbonate nanowires on top of the flexible substrate. The wires secured their properties at a temperature of 700℃ or above. The team employed the collection of wearable energy to obtain much higher electrical energy than that of an energy collecting device designed based on regular barium titanate nanowires.
The researchers said that their technology is built upon a semiconductor process, known as Physical Vapor Deposition that allows various materials such as ceramics and semiconductors to be used for flexible substrates of nanowires. They expected that high performance flexible electric devices such as flexible transistors and thermoelectric elements can be produced with this method.
Mr. Seo said, “In this study, we transported nanowire materials with developed properties on a flexible substrate and showed an increase in device performance. Our technology will be fundamental to the production of various nanowires on a flexible substrate as well as the feasibility of making high performance wearable electric devices.”
This research was supported by the Leap Research Support Program of the National Research Foundation of Korea.
Fig. 1. Transcription process of new, developed nanowires (a) and a fundamental mimetic diagram of a nano-sacrificial layer (b)
Fig. 2. Transcription results from using gold (AU) nanowires. The categories of the results were (a) optical images, (b) physical signals, (c) cross-sectional images from a scanning electron microscope (SEM), and (d-f) an electric verification of whether the perfectly arranged nanowires were made on a large surface.
Fig. 3. Transcription from using barium titanate (BaTiO3) nanowires. The results were (a) optical images, (b-e) top images taken from an SEM in various locations, and (f, g) property analysis.
Fig. 4. Mimetic diagram of the energy collecting device from using a BaTiO3 nanowire substrate and an optical image of the experiment for the miniature energy collecting device attached to an index finger.
2017.03.22 View 9535 -
Professor Jae Kyoung Kim Receives the 2017 HSFP Award
The Human Frontier Science Program (HSFP), one of the most competitive research grants in life sciences, has funded researchers worldwide across and beyond the field since 1990. Each year, the program selects a handful of recipients who push the envelope of basic research in biology to bring breakthroughs from novel approaches. Among its 7,000 recipients thus far, 26 scientists have received the Nobel Prize. For that reason, HSFP grants are often referred to as “Nobel Prize Grants.”
Professor Jae Kyoung Kim of the Mathematical Sciences Department at KAIST and his international collaborators, Professor Robert Havekes from the University of Groningen, the Netherlands, Professor Sara Aton from the University of Michigan in Ann Arbor, the United States, and Professor Matias Zurbriggen from the University of Düsseldorf, Germany, won the Young Investigator Grants of the 2017 HSFP.
The 30 winning teams of the 2017 competition (in 9 Young Investigator Grants and 21 Program Grants) went through a rigorous year-long review process from a total of 1,073 applications submitted from more than 60 countries around the world. Each winning team will receive financial support averaging 110,000-125,000 USD per year for three years.
Although Professor Kim was trained as a mathematician, he has extended his research focus into biological sciences and attempted to solve some of the most difficult problems in biology by employing mathematical theories and applications including nonlinear dynamics, stochastic process, singular perturbation, and parameter estimation.
The project that won the Young Investigator Grants was a study on how a molecular circadian clock may affect sleep-regulated neurophysiology in mammals. Physiological and metabolic processes such as sleep, blood pressure, and hormone secretion exhibit circadian rhythms in mammals. Professor Kim used mathematical modeling and analysis to explain that the mammalian circadian clock is a hierarchical system, in which the master clock in the superchiasmatic nucleus, a tiny region in the brain that controls circadian rhythms, functions as a pacemaker and synchronizer of peripheral clocks to generate coherent systematic rhythms throughout the body.
Professor Kim said, “The mechanisms of our neuronal and hormonal activities regulating many of our bodily functions over a 24-hour cycle are not yet fully known. We go to sleep every night, but do not really know how it affects our brain functions. I hope my experience in mathematics, along with insights from biologists, can find meaningful answers to some of today’s puzzling problems in biological sciences, for example, revealing the complexities of our brains and showing how they work.”
“In the meantime, I hope collaborations between the fields of mathematics and biology, as yet a rare phenomenon in the Korean scientific community, will become more popular in the near future.”
Professor Kim received his doctoral degree in Applied and Interdisciplinary Mathematics in 2013 from the University of Michigan and joined KAIST in 2015. He has published numerous articles in reputable science journals such as Science, Molecular Cell, Proceedings of the National Academy of Sciences, and Nature Communications.
Both the Program Grants and Young Investigator Grants support international teams with members from at least two countries for innovative and creative research. This year, the Program Grants were awarded to research topics ranging from the evolution of counting and the role of extracellular vesicles in breast cancer bone metastasis to the examination of obesity from a mechanobiological point of view.
The Young Investigator Grants are limited to teams that established their independent research within the last five years and received their doctoral degrees within the last decade. Besides Professor Kim’s study, such topics as the use of infrasound for navigation by seabirds and protein formation in photochemistry and photophysics were awarded in 2017.
Full lists of the 2017 HFSP winners are available at: http://www.hfsp.org/awardees/newly-awarded.
About the Human Frontier Science Program (HFSP):
The HFSP is a research funding program implemented by the International Human Frontier Science Program (HFSPO) based in Strasbourg, France. It promotes intercontinental collaboration and training in cutting-edge, interdisciplinary research specializing in life sciences. Founded in 1989, the HFSPO consists of the European Union and 14 other countries including the G7 nations and South Korea.
2017.03.21 View 10822 -
Professor Kwangjo Kim Named as Fellow of IACR
Professor Kwangjo Kim of the Graduate School of Information Security has been selected as a fellow of the International Association for Cryptologic Research (IACR).
The IACR has honored outstanding scholars who have achieved academic excellence in cryptologic research since 2004. He is the first Korean scholar to receive an IACR fellowship.
The IACR, established in 1981, is responsible for organizing international cryptologic conferences every year including the three major cryptologic academic conferences Eurocrypt, Crypto, and Asiacript. The IACR also sponsors workshop series such as the Theory of Cryptography Conference (TCC), the Workshop on Fast Software Encryption (FSE), the Public Key Cryptography Workshop (PKC), and Cryptographic Hardware and Embedded Systems (CHES).
Professor Kim, an internationally acclaimed scholar in the fields of cryptology and information security theory and its applications, was recognized for his outstanding academic achievements and leadership. He has made significant contributions to cryptology in Korea by hosting Asiacript in 1996 and 2001 as well as CHES in 2014. During his 34 years of academic activities, he has published more than 80 SCI journal papers and garnered more than 20,000 citations.
Professor Kim served on the board of the directors of the IACR from 2000 to 2004 and was the chairperson of the Asiacript Steering Committee from 2005 to 2008. He is on the editorial board of the online journal Cryptography.
Professor Kim said, “I am so humbled and honored to be named as a fellow of such a prestigious academic association. I will continue to strive to assist highly educated information security personnel with further research in cryptology.”
2017.03.16 View 8682 -
Dr.Sung-Chul Shin Inaugurated as the 16th President of KAIST
(President Shin delivers his inaugural address at the inauguration ceremony on March 15.)
Professor Sung-Chul Shin was officially inaugurated as its 16th president of KAIST on March 15 in a ceremony at the KAIST Auditorium.
The celebration began with a procession by dignitaries including the KAIST Board of Trustees Chairman Jang-Moo Lee, the National Academy of Sciences of Korea President Sook-Il Kwun, Daejeon City Mayor Sun-Taik Kwon, National Assemblyman Sangmin Lee, KAIST Alumni Association President Jungsik Koh. Academic leaders, foreign envoys, faculty, students, and staff members of KAIST joined the ceremony.
In his inaugural speech, President Shin presented a new vision for KAIST to become a global value creator in the Fourth Industrial Revolution. He said that KAIST has played a pivotal role in the nation’s industrialization and information revolution over the past half century and, with the advent of the new industry paradigm, KAIST should be now responsible for being a new value creator, not only serving the nation but pursuing global betterment. “KAIST should be a global hub of new knowledge and technology creation,” he emphasized.
Envisioning a “Global Value-Creative World-Leading University,” President Shin aims for KAIST to be an institution which can create global value as an innovative global leading research university. To realize this vision, he pledged to continue innovation in five areas of education, research & development, technology commercialization, globalization of the campus, and future strategy for the university and the nation.
In the educational innovation, he emphasized multidisciplinary studies, team work, and leadership training for students. To this end, KAIST will expand the non-departmental courses toward entire 4-year course while concurrently operating the existing system of declaring a major in students’ second year. KAIST will offer mandatory courses in humanities, social sciences, and arts and most classes will be run by team-based learning and group research activities. “KAIST Global Leadership Center” will support students to develop the qualities required for collaboration and the global leaderships.
With respect to the research innovation, President Shin said KAIST will establish “Convergence Research Matrix” system to foster strategic research groups for interdisciplinary and convergence collaboration across a wide range of divisions and departments. “Based on the CRMS, we will identify 10 flagship future-oriented convergence research areas for KAIST to truly claim its reputation as a world-leading research university,” he said. He added he will also introduce the “Collaborative Research Lab” system to better retain the academic successes without interruption, and to improve the continuity of research. “We will strive to organize teams of professors in diverse age groups to work together in mutually complementary fields,” he added.
In terms of technological commercialization, he hopes that KAIST to be a role model. He said he will make every effort to establish a resilient R&DB environment with ideas, technologies, and entrepreneurship. KAIST will rev up a new university-industry cooperation, fully sponsoring the creation of “Technology in-Kind Investment Companies.”
KAIST will continue to take initiative for globalization. He said KAIST will create an ‘English-Only Zone’ at the campus, saying that his ultimate goal is to create Korean-English bilingual campus. He also asked the foreign community to make their effort to learn Korean and Korean culture while staying at KAIST, in an effort to embrace diversity at the campus. He plans to increase the ratio of foreign faculty from nine percent to 15 percent, while doubling the current foreign student enrollment ratio of five percent.
As for the future strategy for the university and the nation, he will soon finalize the long-term strategic plan of “Vision 2031” that will lay out a roadmap for KAIST future direction toward its 60th anniversary. KAIST will also play a fundamental role in shaping national policies and strategies for science and technology by operating think-tank groups that consist of KAIST beyond disciplines. These think-tanks will design detailed development plans for KAIST as well as for national strategies for the advancement of science and technology.
He said that such institutional innovation will not be completed without the support, dedication, and passion of all KAIST members, adding that he will strive to serve them with 3Cs (Change, Communication, and Care).
For the full text of President Shin’s inaugural address, please click.
2017.03.15 View 11223 -
Highly-Efficient Photoelectrochemical CO2 Reduction
Direct CO2 conversion has continuously attracted a great deal of attention as a technology to produce fuels and chemical building blocks from renewable energy resources. Specifically, substances such as carbon feedstocks and fuels can be produced by utilizing sunlight, water, and CO2 as semiconductors and a water interface through photoelectrochemical CO2 reduction.
A KAIST research team demonstrated a novel photoelectrode structure for highly-selective and efficient photoelectrochemical CO2 reduction reactions. The research team led by Professor Jihun Oh of the Graduate School of EEWS (Energy, Environment, Water and Sustainability) presented a Si photoelectrode with a nanoporous Au thin film that is capable of reducing CO2 to CO with 90 percent selectivity in aqueous solution. The research team’s technology will provide a basic framework for designing the semiconductor photoelectrode structure necessary for photoelectrochemical conversion.
In order to achieve steady conversion of CO2, it is necessary to use a high-performance catalyst to lower overpotential. Among the metal catalysts, Au is known to be an electrocatalyst that converts CO2 to CO.
Conventionally, bare Au, as a catalyst, produces a lot of hydrogen gas due to its low CO selectivity. In addition, the high cost of Au remains a challenge in using the catalyst. Professor Oh’s research team addressed the issue by creating a nanoporous Au thin film formed by the electrochemical reduction of an anodized Au thin film.
As a result, the team could demonstrate an efficient, selective photoelectrochemical reduction reaction of CO2 to CO using electrochemically-treated Au thin films on a Si photoelectrode. The electrochemical reduction on anodized Au thin films forms a nanoporous thin layer exhibiting many grain boundaries of nanoparticles on the Au surface. This dramatically improves the selectivity of the reduction reaction with a maximum CO faradaic efficiency of over 90% at low overpotential and durability.
The research team also used an Au thin film of about 200 nanometers, 50,000 times thinner than previously reported nanostructured Au catalysts, resulting in a cost-effective catalyst. When depositing the catalyst on the semiconductor surface in the type of nanoparticles, the substrate of the thin film will be affected in the course of electrochemical reduction.
Thus, the research team designed a new Si photoelectrode with mesh-type co-catalysts that are independently wired at the front and back of the photoelectrode without influencing the photoelectrode, and made it possible for electrochemical reduction.
Due to the superior CO2 reduction reaction activity of the nanoporous Au mesh and high photovoltage from Si, the Si photoelectrode with the nanoporous Au thin film mesh shows conversion of CO2 to CO with 91% Faradaic efficiency at positive potential than CO equilibrium potential.
Professor Oh explained, “This technology will serve as a platform for diverse semiconductors and catalysts. Researchers can further improve the solar-to-CO2 conversion efficiency using this technology.
Dr. Jun Tae Song, the first author continued, “This new approach made it possible to develop a simple but very important type of electrode structure. It is the first time to achieve CO2 conversion at the potential lower than equilibrium potential. We believe that our research will contribute to efficient CO2 conversion.”
This research was published in the inside front cover of Advanced Energy Materials on February 8, 2017. The research was funded and supported by the Korea Carbon Capture & Sequestration R&D Center. Professor Sung-Yoon Chung of the EEWS also participated in this research.
(Figure: Schematic diagram of a Si photoelectrode that patterns with mesh-type nanoporous Au)
2017.03.08 View 10068 -
13 KAIST Faculty Named as Inaugural Members of Y-KAST
The Korean Academy of Science and Technology (KAST) launched the Young Korean Academy of Science and Technology (Y-KAST) and selected 73 scientists as its inaugural members on February 24. Among them, 13 KAIST faculty were recognized as the inaugural members of Y-KAST.
Y-KAIST, made up of distinguished mid-career scientists under the age of 45, will take the leading role in international collaboration as well as innovative agenda-making in science and technology.
The inaugural members include Professor Hyotcherl Ihee of the Department of Chemistry and Dr. Sung-Jin Oh of the Center for Mathematical Challenges at the Korea Institute for Advanced Study (KIAS), affiliated with KAIST. Professor Ihee is gaining wide acclaim in the fields of physics and chemistry, and in 2016, Dr. Oh was the youngest ever awardee of the Presidential Award of Young Scientist.
The other Y-KAIST members are as follows: Professors Haeshin Lee of the Department of Chemistry; Mi Young Kim, Byung-Kwan Cho, and Ji-Joon Song of the Department of Biological Sciences; Song-Yong Kim of the Department of Mechanical Engineering; Sang-il Oum of the Department of Mathematical Sciences; Jung Kyoon Choi of the Department of Bio and Brain Engineering; Seokwoo Jeon, Sang Ouk Kim, and Il-Doo Kim of the Department of Materials Science and Engineering; Jang Wook Choi of the Graduate School of EEWS (Energy, Environment, Water and Sustainability); and Jeong Ho Lee of the Graduate School of Medical Science and Engineering.
The leading countries of the Academy of Science, which include Germany, Sweden, Belgium, Canada, and Japan, have established the Young Academy of Science since 2010 in order to encourage the research activities of their young scientists and to establish a global platform for collaborative research projects through their active networking at home and abroad.
President Myung-Chul Lee of KAST said, “We will spare no effort to connect these outstanding mid-career researchers for their future collaboration. Their networking will make significant impacts toward their own research activities as well as the global stature of Korea’s science and technology R&D.
(Photo caption: Members of Y-KAST pose at the inaugural ceremony of Y-KAST on February 24.)
2017.03.02 View 18165 -
Semiconductor Photonic Nanocavities on Paper Substrates
Professor Yong-Hoon Cho of the Department of Physics and his team at KAIST have developed a semiconductor photonic nanocavity laser that can operate on a paper substrate.
The researchers hope that this novel method, which involves transferring nano-sized photonic crystal particles onto a paper substrate with high absorptiveness, will enable the diagnoses of various diseases by using high-tech semiconductor sensors at low cost.
The results of this research were published in the November 17th, 2016, issue of Advanced Materials.
Photonic crystals, which utilize light as a medium to provide high bandwidths, can transfer large amounts of information. Compared with their electronic counterparts, photonic crystals also consume less energy to operate.
Normally, semiconductor photonic particles require substrates, which play only a passive role in the assembly and endurance of individual, functional photonic components. These substrates, however, are bulky and environmentally hazardous as they are made up of non-biodegradable materials.
The research team overcame these two shortcomings by replacing a semiconductor substrate with standard paper. The substrate’s mass was reduced considerably, and because paper is made from trees, it degrades. Paper can be easily and cheaply acquired from our surroundings, which drastically reduces the unit cost of semiconductors.
In addition, paper possesses superior mechanical characteristics. It is flexible and can be repeatedly folded and unfolded without being torn. These are traits that have long been sought by researchers for existing flexible substrates.
The research team used a micro-sized stamp to detach photonic crystal nanobeam cavities selectively from their original substrate and transfer them onto a new paper substrate. Using this technique, the team removed nanophotonic crystals that had been patterned (using a process of selectively etching circuits onto a substrate) onto a semiconductor substrate with a high degree of integration, and realigned them as desired on a paper substrate.
The nanophotonic crystals that the team combined with paper in this research were 0.5 micrometers in width, 6 micrometers in length, and 0.3 micrometers in height—about one-hundredth of the width of a single hair (0.1 millimeter).
The team also transferred their photonic crystals onto paper with a fluid channel, which proved that it could be used as a refractive index sensor. As can be seen in current commercial pregnancy diagnosis kits, paper has high absorptiveness. Since photonic crystal particles have high sensitivity, they are highly suitable for applications such as sensors.
Professor Cho stated that “by using paper substrates, this technology can greatly contribute to the rising field of producing environmentally-friendly photonic particles” and “by combining inexpensive paper and high-performance photonic crystal sensors, we can obtain low prices as well as designing appropriate technologies with high performance.”
Dr. Sejeong Kim of the Department of Physics participated in this study as the first author, and Professor Kwanwoo Shin of Sogang University and Professor Yong-Hee Lee of KAIST also took part in this research. The research was supported by the National Research Foundation’s Mid-Career Researcher Program, and the Climate Change Research Hub of KAIST.
Figure 1. Illustration of photonic crystal lasers on paper substrates
Figure 2. Photonic crystal resonator laser and refractive index sensor operating on paper substrates
2017.03.01 View 7728 -
Quantum Dot Film Can Withstand High Temperatures and Humidity
The joint KAIST research team of Professor Byeong-Soo Bae of the Department of Materials Science and Engineering and Professor Doh Chang Lee of the Department of Chemical and Biomolecular Engineering was able to fabricate a siloxane-encapsulated quantum dot film, which exhibits stable emission intensity over one month even at high temperatures and humidity.
The results of this study were published in the Journal of the American Chemical Society (JACS) on November 29, 2016. The research article is entitled “Quantum Dot/Siloxane Composite Film Exceptionally Stable against Oxidation under Heat and Moisture.” (DOI: 10.1021/jacs.6b10681)
Quantum dots (QDs), light-emitting diodes (LEDs) for next-generation displays, are tiny particles or nanocrystals of semiconducting materials. Their emission wavelength can easily be adjusted by changing their sizes, which are just a few nanometers. A wide spectrum of their colors can also achieve ultra-high definition displays.
Due to these characteristics, QDs are coated on a film as a polymer resin in dispersed form, or they are spread on an LED light source. They are thus considered to be crucial for next generation displays.
Despite their exceptional optical properties, however, QDs are easily oxidized in a high temperature and high humidity environment, and, as a result, this greatly deteriorates their luminescence quality (quantum efficiency). Therefore, they are encapsulated in an extra thin layer to block oxygen and moisture.
QD displays in the current market have a film inserted to separate them from LEDs, which create heat. The high unit cost of this protective layer, however, increases the overall cost of displays, lowering their price competitiveness in the market.
For a solution, the research team applied the sol-gel condensation reaction of silane precursors with QDs. This technology uses the reactions of chemical substances to synthesize ceramics or glass at a low temperature.
The team applied QDs in a heat resistant siloxane polymer by employing this technology. The siloxane resin acted as a cup holding the QDs and also blocked heat and moisture. Thus, their performance can be maintained without an extra protective film.
QDs are evenly dispersed into the resin from a chemical process to fabricate a QD embedded film and retained the high quality luminescence not only at a high temperature of 85°C and in a high humidity of 85%, but also in a high acid and high base environment. Remarkably though, the luminescence actually increased in the high humidity environment.
If this technology is used, the overall price of displays will decrease by producing a stable QD film without an extra protective barrier. In the future, the QD film can be directly applied to a blue LED light source. As a result, it will be possible to develop a QD display that can reduce the amount of QDs needed and improve its performance.
Professor Bae said, “We have proposed a way to make quantum dots overcome their limitations and have wide applications as they are being developed for next-generation displays. Our technology will make significant contributions to the display industry in the country.”
He also added, “In the future, we plan to cooperate with companies both in and out of the country to improve the performance of quantum dots and concentrate on their commercialization.”
The research team is currently applying for related patents both in and out of the country. The team is also plan ning to transfer the patents to Sol Ip Technology Inc., a company founded at KAIST, to start the commercialization.
Picture 1:
Siloxane-encapsulated quantum dot (QD) films showing performance stability in boiling water
Picture 2 and 3:
So-gel condensation reaction in silane precursors between Methacryloxypropyltrimethoxysilane (MPTS) and diphenylsilanediol (DPSD). The inset shows photographs of a QD-oligosiloxane resin under room light (left) and a UV lamp (λ = 365 nm) (right).
Free radical addition reactions among carbon double bonds of methacryl functional groups and oleic acids. The inset shows photographs of a QD-silox film under room light (left) and a UV lamp (λ = 365 nm) (right).
2017.02.24 View 10547 -
Prof. Woo Chang Kim Is Appointed as Managing Editor of Quantitative Finance
Professor Woo Chang Kim of the Industrial and Systems Engineering Department has been elected as the Managing Editor of Quantitative Finance.
Founded in 2001, Quantitative Finance has been an internationally-acclaimed peer-reviewed journal in the field of financial engineering, along with Mathematical Finance.
This is the first time for a Korean researcher to be named for the editorial board, which consists of eminent scholars from around the world, including four Nobel laureates.
Professor Kim’s expertise lies in financial optimization, portfolio management, and asset liability management. In recent years, he has focused his research on robo-advisors in the area of FinTech, and for this contribution, he was appointed as managing editor.
Professor Kim also served as an editor, deputy editor, and a member of the editorial boards for various journals, including the Journal of Portfolio Management and Optimization and Engineering. Currently, he serves as a member of the Korean National Pension Fund’s Electoral Commission, an adviser to Samsung Asset Management Co., Ltd., and the director of the KAIST Asset Management for Future Technology Research Center that was opened in October 2016.
2017.02.23 View 8444 -
Dr. Sung-Chul Shin Selected 16th President of KAIST
(President Sung-Chul Shin)
The KAIST Board of Trustees elected Professor Sung-Chul Shin of the Department of Physics the 16th president of KAIST on February 21. Professor Shin succeeds President Sung-Mo Kang whose four-year term will end on February 23. He is the first KAIST alumnus to serve as its president.
The Board of Trustees announced, “We believe that Professor Shin’s scientific achievement, outstanding leadership, and clear vision will serve KAIST faculty, students, and staff very well. He will be the best person to help KAIST leap forward in the four years ahead.”
The newly-elected president said, “I am humbled and honored to have been elected to lead such a prestigious institute of Korea. Aiming to be one of the top ten global universities, KAIST will continue to innovate its systems.” Previously, Dr. Shin led the Daegu Gyeongbuk Institute of Science and Technology (DGIST) for six years as president since 2011.
Professor Shin joined the KAIST faculty in 1989. He graduated from Seoul National University and then earned his MS degree in condensed matter physics at KAIST in 1977. After earning his Ph.D. in material physics at Northwestern University in 1984, he worked at Eastman Kodak Research Labs as a senior research scientist for five years.
Before heading to DGIST, President Shin held key administrative positions at KAIST from the early 1990s including dean of planning, dean of the international office, and vice-dean of student affairs. During President Robert Laughlin’s tenure, the first foreign president at KAIST, he served as vice-president for two years from 2004. He also served on the Presidential Advisory Council on Science and Technology of the Korean government as vice chairperson from 2015 to 2016.
A renowned scholar in the field of nanoscience, President Shin’s research focuses on the artificial synthesis and characterization of nonmagnetic materials, magnetic anisotropy, and magneto-optical phenomena. He leads the Laboratory for Nanospinics of Spintronic Materials at KAIST and has published in 290 journals while holding 37 patents.
A fellow in the American Physical Society (APS) since 2008, he was the president of the Korean Physical Society from 2011 to 2012. He has been on the editorial board of J. Magnetism and Magnetic Materials from 2009 and was the first Korean recipient of the Asian Union of Magnetics Societies (AUMS) Award, which recognizes outstanding scientists in the field of magnetics.
President Shin envisions making KAIST’s research and education more competitive through continuing innovation. His innovation efforts will extend to the five key areas of education, research, technology commercialization, globalization, and future planning.
Among his priorities, he emphasizes multidisciplinary studies and leadership training for students. He plans to focus on undeclared major courses for undergraduates to help them expand their experience and exposure to diverse disciplines. This approach will help create well-rounded engineers, scientists, and entrepreneurs by enabling them to develop skills while leveraging a strong connection to the arts, humanities, and social sciences.
To better respond to Industry 4.0, which calls for convergence studies and collaborative work, he proposed establishing a ‘Convergence Innovation System’ by strategically selecting 10 flagship convergence research groups. In order to accelerate the technology commercialization and ecosystem of start-ups, he will strengthen entrepreneurship education, making it a prerequisite requirement for students. President Shin said he will spare no effort to incubate and spin-off ventures in which KAIST technology is being transferred. For globalization efforts, he plans to increase the ratio of foreign faculty from 9 percent to 15 percent, while doubling the current foreign student enrollment ratio of 5 percent. For future strategic innovation, he will implement a long-term innovation strategic plan dubbed ‘Vision 2031.’
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Professor Shin Honored Posthumously for Iridescent Microparticles
(The Late Professor Joong-Hoon Shin (left) and Professor Shin-Hyun Kim)
A research team co-led by Professor Shin-Hyun Kim from the Department of Chemical and Biomolecular Engineering and Professor Jong-Ryul Jeong from the Department of Materials Science and Engineering at Chungnam National University developed iridescent microparticles with a structural color gradient. The research team posthumously dedicated their research to a renowned professor in the field of nanophotonics, the late Professor Joong-Hoon Shin of the Graduate School of Nanoscience and Technology at KAIST. He passed away suddenly in a car accident last September.
The iridescent microparticles, which allow on-demand control over structural color, will be key components for next-generation reflection-mode displays with clear color realization even in direct sunlight.
Materials such as opals, Morpho butterfly wings, and peacock feathers all display beautiful colors without pigment, using regularly-spaced nanostructures. Regularly-spaced nanostructures render color, by selectively reflecting the light of a particular wave through light interference. As such, materials that possess periodic modulation of refractive index at subwavelength scale are referred to as photonic crystals.
In general, photonic crystals are only able to display a single color, so limitations exist when attempting to apply them to reflection-mode displays which call for multiple structural colors. The research team addressed the issue using inspiration from snowflakes stacking in the winter. When snow falls on the surface of a round-shaped structure, the thickness of the snow stacking differs depending on the orientation. Based on this observation, the research team created photonic microparticles with a structural color gradient by depositing two different materials on spherical microparticles.
When some material is deposited on the surface of a sphere, the material on the top is thickest and becomes thinner on the sides. The team alternately deposited titania and silica on the spherical microparticles to form periodic modulation of the refractive index. The thickness of the alternating photonic layers is reduced along the angle from the top, which yields a structural color gradient.
Consequently, the microparticles reflect long-wavelength red light from the top of the sphere and short-wavelength blue light from the side of the sphere. Any color of the visible spectrum can be selected in between the top and side depending on the orientation of the microparticles.
The research team used an external magnetic field as a way to control the orientation of the photonic microparticles and the structural colors. As magnetic iron layer was deposited underneath the alternating photonic layer, it was possible to freely control the orientation of the microparticles using a magnet, thereby allowing control of the color seen by the users.
KAIST doctoral candidate Seung Yeol Lee of the Department of Chemical and Biomolecular Engineering is the first author of this research, with support from the Midcareer Researcher Program of the National Research Foundation and funded by the Ministry of Science, ICT, and Future Planning (MSIP). This research was published in the online edition of Advanced Materials on February 6, 2017.
Figure1: Sets of an OM image of photonic Janus microspheres and an SEM image showing a cross-section of the photonic layers.
Figure 2: A series of schematics and OM images showing the color change depending on the orientation angle of the photonic Janus microsphere.
2017.02.17 View 8948