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First Korean Member of OceanObs' Organizing Committee
Professor Sung Yong Kim from the Department of Mechanical Engineering became the first Korean to be elected as an organizing committee member of the international conference OceanObs’19’, specializing in the ocean observing field.
Professor Kim has been actively engaged in advisory panels, technical committees, and working groups for the North Pacific Marine Science Organization (PICES). Through numerous activities, he was recognized for his professionalism and academic achievements, which led him to be appointed as a member of the organizing committee.
The organizing committee is comprised of leading scholars and researchers from 20 countries, and Professor Kim will be the first Korean scientist to participate on the committee.
Since 1999, the conference has been held every decade. Global experts specializing in oceanic observation gather to discuss research directions for the next ten years by monitoring physical, biological, and chemical variables in regional, national, and global oceans and applying marine engineering.
This year, approximately 20 institutes including NASA’s Jet Propulsion Laboratory (JPL), the National Science Foundation, the National Oceanic and Atmospheric Administration, and the European Space Agency will support funds as well as high-tech equipment to the conference.
This year’s conference theme is the governance of global ocean observing systems such as underwater gliders, unmanned vehicles, remote sensing, and observatories. The conference will hold discussions on monitoring technology and information systems to ensure human safety as well as to develop and preserve food resources. Additionally, participants will explore ways to expand observational infrastructures and carry out multidisciplinary approaches.
There will also be collaborations with the Global Ocean Observing System (GOOS) and the Partnership for Observation of the Global Oceans (POGO) to organize ocean observing programs and discuss priorities.
Finally, they will set a long-term plan for solving major scientific issues, such as climate change, ocean acidification, energy, and marine pollution.
Professor Kim said, “Based on the outcomes drawn from the conference, I will carry out research on natural disasters and climate change monitoring by using unmanned observing systems. I will also encourage more multidisciplinary research in this field.”
2019.01.25 View 13221 -
Enhanced Video Quality despite Poor Network Conditions
(from left: Jaehong Kim, Youngmok Jung, Hyunho Yeo, Professor Dongsu Han and Professor Jinwoo Shin)
Professor Jinwoo Shin and Professor Dongsu Han from the School of Electrical Engineering developed neural adaptive content-aware internet video delivery. This technology is a novel method that combines adaptive streaming over HTTP, the video transmission system adopted by YouTube and Netflix, with a deep learning model.
This technology is expected to create an internet environment where users can enjoy watching 4K and AV/VR videos with high-quality and high-definition (HD) videos even with weak internet connections.
Thanks to video streaming services, internet video has experienced remarkable growth; nevertheless, users often suffer from low video quality due to unfavorable network conditions. Currently, existing adaptive streaming systems adjust the quality of the video in real time, accommodating the continuously changing internet bandwidth. Various algorithms are being researched for adaptive streaming systems, but there is an inherent limitation; that is, high-quality videos cannot be streamed in poor network environments regardless of which algorithm is used.
By incorporating super-resolution in adaptive streaming, the team overcame the limit of existing content distribution networks, of which their quality relies too much on the bandwidth. In the conventional method, the server that provides the video splits a video into certain lengths of time in advance. But the novel system introduced by the team allows the downloading of neural network segments. To facilitate this method, the video server needs to provide deep neural networks for each video segment as well as sizes of Deep Neural Networks (DNN) according to the specifications of the user’s computing capacity.
The largest neural network size is two megabytes, which is considerably smaller than video. When downloading the neural network from the user’s video player, it is split into several segments. Even its partial download is sufficient for a slightly comprised super-resolution.
While playing the video, the system converts the low quality video to a high-quality version by employing super-resolution based on deep convolution neural networks (CNN). The entire process is done in real time, and users can enjoy the high-definition video.
Even with a 17% smaller bandwidth, the system can provide the Quality of Experience equivalent to the latest adaptive streaming service. At a given internet bandwidth, it can provide 43% higher average QoE than the latest service.
Using a deep learning method allows this system to achieve a higher level of compression than the existing video compression methods. Their technology was recognized as a next-generation internet video system that applies super-resolution based on a deep convolution neural network to online videos.
Professor Han said, “So far, it has only been implemented on desktops, but we will further develop applications that work in mobile devices as well. This technology has been applied to the same video transmission systems used by streaming channels such as YouTube and Netflix, and thus shows good signs for practicability.”
This research, led by Hyunho Yeo, Youngmok Jung and Jaehong Kim, was presented at the 13th UNSENIX OSDI conference on October 10 2018 and completed for filing international patent application.
For further information, please click here.
Figure 1. Image quality before (left) and after (right) the technology application
Figure 2. The technology Concept
Figure 3. A transition from low-quality to high quality video after video transmission from the video server
2019.01.22 View 7495 -
KAIST Presents Innovations at CES 2019
Ten of the most innovative technologies spun off from KAIST made a debut at the Consumer Electronics Show (CES) 2019, the world’s largest consumer electronics and IT exhibition being held in Las Vegas from January 8 to 11. The KAIST booth at the CES featured technologies made by KAIST research teams and five startup companies including LiBEST, Memslux, and Green Power. In particular, the KAIST Alumni Association invited 33 aspiring alumni entrepreneurs selected from the KAIST Startup Competition to the show.
At the exhibition, KAIST is presenting innovations in the fields of AI and Bio-IT convergence for the Fourth Industrial Revolution. These include real-time upscaling from Full HD to 4K UHD using AI deep learning-based convolutional neural networks (Professor Munchurl Kim, School of Electrical Engineering) and an AI conversation agent that responds to user’s emotions (Professor Soo-Young Lee, School of Electrical Engineering).
Other technologies include optimal drug target identification by cancer cell type through drug response prediction to be used in personalized cancer treatments (Professor Kwang-Hyun Cho, Department of Bio and Brain Engineering), a nanofiber-based color changing gas sensor with greater sensitivity than conventional paper-based color changing sensors (Professor Il-Doo Kim, Department of Materials Science and Engineering), and functional near-infrared spectroscopy (fNIRS) for brain imaging and muscle fatigue measurement (Professor Hyeonmin Bae, School of Electrical Engineering).
The KAIST booth also features startups founded by KAIST alumni including LiBEST with a flexible lithium polymer secondary cell optimized for smart wearable devices and Rempus with a high-performance lithium ion cell packaging technology for outstanding safety, high capacity, long life, and fast charging.
Green Power and Smart Radar Systems are also joining the booth with a highly efficient and eco-friendly wireless charging system for electrical cars, and a 4D image radar sensor that detects 3D images and speed in real time for applications in self-driving cars, drones, and security systems respectively.
Faculty-founded startup Memslux (CEO Jun-Bo Yoon, School of Electrical Engineering) is presenting a transparent surface light source solution for next-generation display devices.
Associate Vice President of Office of University-Industry Cooperation Kyung Cheol Choi said, “I believe that universities should play a role in connecting technological innovations to business startups for creating value at a global level. In that sense, it is a great opportunity to present innovative technologies from KAIST and promote outstanding KAIST startups at CES 2019. Hopefully, this experience will lead to joint R&D, investment, cooperation, and international technology transfer contracts with leading companies from around the world.”
Here are the five key technologies presented by KAIST at CES 2019.
2019.01.10 View 9289 -
Fabrication of Shape-conformable Batteries with 3D-Printing
(from left: Dr. Bok Yeop Ahn, Dr. Chanhoon Kim, Professor Il-Doo Kim and Professor Jennifer A. Lewis)
Flexible, wireless electronic devices are rapidly emerging and have reached the level of commercialization; nevertheless, most of battery shapes are limited to either spherical and/or rectangular structures, which results in inefficient space use. Professor Il-Doo Kim’s team from the Department of Materials Science at KAIST has successfully developed technology to significantly enhance the variability of battery design through collaboration research with Professor Jennifer A. Lewis and her team from the School of Engineering and Applied Sciences at Harvard University.
Most of the battery shapes today are optimized for coin cell and/or pouch cells. Since the battery as an energy storage device occupies most of the space in microelectronic devices with different designs, new technology to freely change the shape of the battery is required.
The KAIST-Harvard research collaboration team has successfully manufactured various kinds of battery shapes, such as ring-type, H, and U shape, using 3D printing technology. And through the research collaboration with Dr. Youngmin Choi at the Korea Research Institute of Chemical Technology (KRICT), 3D-printed batteries were applied to small-scale wearable electronic devices (wearable light sensor rings).
The research group has adopted environmentally friendly aqueous Zn-ion batteries to make customized battery packs. This system, which uses Zn2+ instead of Li+ as charge carriers, is much safer compared with the conventional lithium rechargeable batteries that use highly inflammable organic electrolytes. Moreover, the processing conditions of lithium-ion batteries are very complicated because organic solvents can ignite upon exposure to moisture and oxygen.
As the aqueous Zn-ion batteries adopted by the research team are stable upon contact with atmospheric moisture and oxygen, they can be fabricated in the ambient air condition, and have advantages in packaging since packaged plastic does not dissolve in water even when plastic packaging is applied using a 3D printer.
To fabricate a stable cathode that can be modulated in various forms and allows high charge-discharge, the research team fabricated a carbon fiber current collector using electrospinning process and uniformly coated electrochemically active polyaniline conductive polymer on the surface of carbon fiber for a current collector-active layer integrated cathode. The cathode, based on conductive polyaniline consisting of a 3D structure, exhibits very fast charging speeds (50% of the charge in two minutes) and can be fabricated without the detachment of active cathode materials, so various battery forms with high mechanical stability can be manufactured.
Prof. Kim said, “Zn-ion batteries employing aqueous electrolytes have the advantage of fabrication under ambient conditions, so it is easy to fabricate the customized battery packs using 3D printing.”
“3D-printed batteries can be easily applied for niche applications such as wearable, personalized, miniaturized micro-robots, and implantable medical devices or microelectronic storage devices with unique designs,” added Professor Lewis.
With Dr. Chanhoon Kim in the Department of Materials Science and Engineering at KAIST and Dr. Bok Yeop Ahn School of Engineering and Applied Sciences at Harvard University participating as equally contributing first authors, this work was published in the December issue of ACS Nano.
This work was financially supported by the Global Research Laboratory (NRF-2015K1A1A2029679) and Wearable Platform Materials Technology Center (2016R1A5A1009926).
Figure 1.Fabrication of shape-conformable batteries based on 3D-printing technology and the application of polyaniline carbon nanofiber cathodes and wearable electronic devices
Figure 2.Fabricated shape-conformable batteries based on a 3D-printing method
Meanwhile, Professor Il-Doo Kim was recently appointed as an Associate Editor of ACS Nano, a highly renowned journal in the field of nanoscience.
Professor Kim said, “It is my great honor to be an Associate Editor of the highly renowned journal ACS Nano, which has an impact factor reaching 13.709 with 134,596 citations as of 2017. Through the editorial activities in the fields of energy, I will dedicate myself to improving the prominence of KAIST and expanding the scope of Korea’s science and technology. I will also contribute to carrying out more international collaborations with world-leading research groups.”
(Associate Editor of ACS Nano Professor Il-Doo Kim)
2018.12.20 View 11690 -
Reducing the Drag Force of a Moving Body Underwater
(from left: Professor Yeunwoo Cho and PhD Jaeho Chung)
Professor Yeunwoo Cho and his team from the Department of Mechanical Engineering developed new technology that reduces the drag force of a moving body in a still fluid by using the supercavitation phenomenon.
When a body moves in air, the frictional drag is lower than that of the same body moving in water. Therefore, the body that moves in water can reduce the drag significantly when it is completely enveloped in a gaseous cavity.
The team used compressed air to create so-called supercavitation, which is a phenomenon created by completely enveloping a body in a single large gaseous cavity. The drag force exerted on the body is then measured.
As a result, the team confirmed that the drag force for a moving body enveloped in air is about 25% of the drag force for a moving body without envelopment.
These results can be applied for developing high-speed underwater vehicles and the development of air-lubricated, high-speed vessels.
The team expects that the results can be applied for developing high-speed underwater vehicles and the development of air lubrication for a ship’s hull.
This research, led by PhD Jaeho Chung, was published in the Journal of Fluid Mechanics as a cover article on November 10, 2018.
Figure 1. The cover article of the Journal of Fluid Mechanics Vol. 854
2018.12.04 View 4797 -
KAIST Seals the Deal for Kenya KAIST Project
KAIST will participate in Kenya’s strategic economic development plan under the provision of a turnkey-based science and technology education consultancy for the establishment of the Kenya Advanced Institute of Science and Technology (Kenya KAIST).KAIST signed the contract on November 30 with the Konza Technopolis Development Authority to establish Kenya KAIST. Korea Eximbank will offer a 95 million USD loan to the Kenyan government for this project. The project will include the educational and architectural design and construction of Kenya KAIST. The campus will be constructed in the Konza Techno City nearby Nairobi by 2021, with the first batch of 200 graduate students starting classes in 2022. KAIST, in consortium with Samwoo and Sunjin architecture and engineering companies, will take the lead of the three-year project, with the kick-off ceremony planned at the end of next January in Nairobi. The Kenyan government plans to transform Kenya into a middle-income country under Vision 2030 through promoting science, technology, and innovation for national economic growth. Nicknamed Africa’s Silicon Savannah, Konza Techno City is a strategic science and technology hub to realize this vision. To this end, the medium-term plan set a goal to provide specialized research and training in various leading-edge engineering and advanced science fields.In the two-phase evaluation of the consultancy bidding, KAIST won preferred bidder status in the technical proposal evaluation, outbidding three other Korean consortia. Invited to the financial proposal bidding, the KAIST consortium successfully completed month-long contract negotiations with Kenya last week.KAIST will develop academic curricula for six initial departments (Mechanical Engineering, Electrical/Electronic Engineering, ICT Engineering, Chemical Engineering, Civil Engineering, and Agricultural Biotechnology), which will lay the ground work for engineering research and education in Kenya to meet emerging socioeconomic demands. In addition, KAIST will provide the education of basic sciences of math, physics, chemistry, and biology for students.It is also notable that the Kenyan government asked to develop an industry-academy cooperation program in Konza Techno City. It reflects the growing industrial needs of Kenya KAIST, which will be located in the center of the Konza Technopolis. It is anticipated that the technopolis will create 16,675 jobs in the medium term and over 200,000 after completion, positioning Kenya as an ICT hub within the region.KAIST also shares a similar history of establishment with Kenya KAIST, as it will be built with a foreign loan. KAIST, created by the Korean government in 1971 to drive the economic engine through advancement of science and technology with a six-million USD loan from USAID, has now become a donor institution that hands down science and technology education systems including the construction of campuses to underdeveloped countries.The successful case of KAIST has been benchmarked by many countries for years. For instance, KAIST set up the curriculum of the nuclear engineering program at the Khalifa University of Science and Technology in UAE in 2010. In China, Chongqing University of Technology is running its electrical engineering and computer science programs based on the educational systems and curricula offered by KAIST from 2015. In October, KAIST also signed an MOU with the Prince Mohammad Bin Salman College of Cyber Security, AI, and Advanced Technologies in Saudi Arabia to provide the undergraduate program for robotics.Among all these programs benchmarking KAIST, Kenya KAIST clearly stands out, for it is carrying out a turnkey-based project that encompasses every aspect of institution building ranging from educational curriculum development to campus construction and supervision.President Sung-Chul Shin is extremely excited about finalizing the deal, remarking, “It is of great significance that KAIST’s successful development model has carved out a unique path to becoming a global leading university that will benefit other countries. In only a half century, we have transitioned from a receiver to a donor institution, as the country itself has done.”“KAIST will spare no effort for Kenya KAIST to become a successful science and technology university that will play a crucial role in Kenya’s national development. I believe Kenya KAIST will be an exemplary case of an ODA (Official Development Assistance) project based on the development of science and technology to benefit underdeveloped countries,” he added.
2018.12.03 View 11257 -
KAIST Shows Strong Performance in Crypto Contest Korea 2018
(Awardees at the ceremony for Crypto Contest Korea 2018)
A paper titled “Indifferentiability of Truncated Random Permutations” by PhD candidate Wonseok Choi and MS candidate Byeonghak Lee (under Professor Jooyoung Lee) from the KAIST Graduate School of Information Security (GSIS) won first place in Crypto Contest Korea 2018. Byeonghak Lee became a repeat winner since his paper titled “Tweakable Block Ciphers Secure Beyond the Birthday Bound in the Ideal Cipher Model” also received an award at Crypto Contest Korea 2017.
The contest, hosted by the Korea Cryptography Forum, the Korea Institute of Information Security & Cryptology, and the National Security Research Institute and sponsored by the National Intelligence Service, was held for promoting cryptography in Korea. The total prize money is fifty million won with ten million won going to the first place winners.
The contest was divided into three divisions: paper, problem solving, and idea. Among the three divisions, first place came from the paper division only.
Besides first place, KAIST students showed outstanding performance in the contest. PhD candidate Seongkwang Kim received participation prize while he also received special prizes with MS candidate Yeongmin Lee. The hacking club GoN (under Professor Sang Kil Cha), comprised of undergraduate students from the GSIS was awarded the grand prize in the division of problem solving.
The award ceremony was held during the Future Crypto Workshop 2018 on November 15. The awards ceremony for Crypto Expert Korea 2018 were also held there, and PhD candidate Ji-Eun Lee from the School of Computing and Byeonghak Lee received awards, the grand prize and runner-up prize respectively.
2018.11.27 View 9969 -
Faster and More Powerful Aqueous Hybrid Capacitor
(Professor Jeung Ku Kang from the Graduate School of EEWS)
A KAIST research team made it one step closer to realizing safe energy storage with high energy density, high power density, and a longer cycle life. This hybrid storage alternative shows power density 100 times faster than conventional batteries, allowing it to be charged within a few seconds. Hence, it is suitable for small portable electronic devices.
Conventional electrochemical energy storage systems, including lithium-ion batteries (LIBs), have a high voltage range and energy density, but are subject to safety issues raised by flammable organic electrolytes, which are used to ensure the beneficial properties. Additionally, they suffer from slow electrochemical reaction rates, which lead to a poor charging rate and low power density with a capacity that fades quickly, resulting in a short cycle life.
On the other hand, capacitors based on aqueous electrolytes are receiving a great deal of attention because they are considered to be safe and environmentally friendly alternatives. However, aqueous electrolytes lag behind energy storage systems based on organic electrolytes in terms of energy density due to their limited voltage range and low capacitance.
Hence, developing aqueous energy storage with high energy density and a long cycle life in addition to the high power density that enables fast charging is the most challenging task for advancing next-generation electrochemical energy storage devices.
Here, Professor Jeung Ku Kang from the Graduate School of Energy, Environment, Water and Sustainability and his team developed an aqueous hybrid capacitor (AHC) that boasts high energy density, high power, and excellent cycle stability by synthesizing two types of porous metal oxide nanoclusters on graphene to create positive and negative electrodes for AHCs.
The porous metal oxide nanoparticles are composed of nanoclusters as small as two to three nanometers and have mesopores that are smaller than five nanometers. In these porous structures, ions can be rapidly transferred to the material surfaces and a large number of ions can be stored inside the metal oxide particles very quickly due to their small particle size and large surface area.
The team applied porous manganese oxide on graphene for positive electrodes and porous iron oxide on graphene for negative electrodes to design an aqueous hybrid capacitor that can operate at an extended voltage range of 2V.
Professor Kang said, “This newly developed AHC with high capacity and power density driven from porous metal oxide electrodes will contribute to commercializing a new type of energy storage system. This technology allows ultra-fast charging within several seconds, making it suitable as a power source for mobile devices or electric vehicles where solar energy is directly stored as electricity.”
This research, co-led by Professor Hyung Mo Jeong from Kangwon National University, was published in Advanced Functional Materials on August 15, 2018.
Figure 1. Image that shows properties of porous metal oxide nanoparticles formed on graphene in the aqueous hybrid capacitor
2018.11.09 View 8292 -
Team KAT Wins the Autonomous Car Challenge
(Team KAT receiving the Presidential Award)
A KAIST team won the 2018 International Autonomous Car Challenge for University Students held in Daegu on November 2.
Professor Seung-Hyun Kong from the ChoChunShik Graduate School of Green Transportation and his team participated in this contest with the team named KAT (KAIST Autonomous Technologies). The team received the Presidential Award with a fifty million won cash prize and an opportunity for a field trip abroad.
The competition was conducted on actual roads with Connected Autonomous Vehicles (CAV), which incorporate autonomous driving technologies and vehicle-to-everything (V2X) communication system.
In this contest, the autonomous vehicles were given a mission to pick up passengers or parcels. Through the V2X communication, the contest gave current location of the passengers or parcels, their destination, and service profitability according to distance and level of service difficulty.
The participating vehicles had to be equipped very accurate and robust navigation system since they had to drive on narrow roads as well as go through tunnels where GPS was not available. Moreover, they had to use camera-based recognition technology that was invulnerable to backlight as the contest was in the late afternoon.
The contest scored the mission in the following way: the vehicles get points if they pick up passengers and safely drop them off at their destination; on the other hand, points are deducted when they violate lanes or traffic lights. It will be a major black mark if a participant sitting in the driver’s seat needs to get involved in driving due to a technical issue.
Youngbo Shim of KAT said, “We believe that we got major points for technical superiority in autonomous driving and our algorithm for passenger selection.”
This contest, hosted by Ministry of Trade, Industry and Energy, was the first international competition for autonomous driving on actual roads. A total of nine teams participated in the final contest, four domestic teams and five teams allied with overseas universities such as Tsinghua University, Waseda University, and Nanyang Technological University.
Professor Kong said, “There is still a long way to go for fully autonomous vehicles that drive flexibly under congested traffic conditions. However, we will continue to our research in order to achieve high-quality autonomous driving technology.”
(Team KAT getting ready for the challenge)
2018.11.06 View 13914 -
KAIST Launches Woorisae II
Professor Sejin Kwon from the Department of Aerospace Engineering and his team succeeded in launching a science rocket, named ‘Woorisae II’ at Saemanguem reclamation. This rocket was developed in collaboration with the Satellite Technology Research Lab (SaRTec).
The test-firing was conducted at 10:43 am on Sunday October 28, 2018 (35°N 42’ 06” 126°E 33’ 36”, Radius of 0.6NM). This launch was the follow-up to the previous launch that was cancelled due to not gaining approval for using the airspace.
Professor Kwon’s team put a great deal of effort into securing the land for the rocket launch. As a result, they got approval from the Saemangeum Development and Investment Agency for the land and the Ministry of Land, Infrastructure and Transport for the use of the airspace. The Republic of Korea Air Force and United States Air Force also approved the use of the airspace for the launch of the science rocket for research purposes.
Woorisae II is 2.2 meters long with a diameter of 20cm, and weighs 13kg without a payload. The rocket is powered by a hybrid rocket with hydrogen peroxide oxidizer producing 100 kg of force. The Woorisae II sounding rocket was designed to burn for five seconds and then continue inertial flight for 20 seconds. The target altitude of Woorisae II was set at 3,300 feet to comply with the airspace approval.
The team developed the core components, including a hybrid rocket propulsion system, flight computer and parachute recovery system, as well as a ground control station. The flight data was transmitted to the ground station and recorded to onboard computer memory.
When a malfunction occurs during the flight, Woorisae II was designed to terminate the power flight for safety by shutting the propellant valve and deploying the recovery parachute. All the rocket subsystems and components were developed and supplied by domestic startup companies such as INOCOM and NARA SPACE TEHCNOLOGY.
Generally, sounding rockets reach an altitude beyond 30km and are widely used for testing rocket engines and reentry materials as well as for conducting microgravity experiments. Instruments for atmospheric science can also be installed to measure fine dust and high altitude atmosphere. Besides these science and technology purposes, most advanced spacefaring countries have sounding rocket programs to train and educate young people in the field of space science.
Professor Kwon said, “We will plan to launch upgraded rockets on November 4 and December 6 because we already received approval from the related agencies for using this land and airspace. Based on the experiment, we are planning to develop a cost-efficient small launch vehicle that is capable of delivering a cube satellite into Earth’s orbit.”
(Photos of preparing the rocket launch)
2018.10.29 View 12226 -
Lens-free OLEDs with Efficiency comparable to that of Inorganic LEDs
(from left: Professor Seunghyup Yoo and PhD candidate Jinouk Song)
The use of organic light-emitting diodes (OLEDs) has extended to various applications, but their efficiency is still lagging behind inorganic light-emitting diodes. In this research, a KAIST team provided a systematic way to yield OLEDs with an external quantum efficiency (EQE) greater than 50% with an external scattering medium.
Having properties suitable for thin and flexible devices, OLEDs are popular light sources for displays, such as mobile devices and high quality TVs. In recent years, numerous efforts have been made to apply OLEDs in lighting as well as light sources for vehicles.
For such applications, high efficiency is of the upmost importance for the successful deployment of light sources. Thanks to continuous research and the development of OLEDs, their efficiency is steadily on the rise, and a level equivalent to inorganic LEDs has been demonstrated in some reports.
However, these highly efficient OLEDs were often achieved with a macroscopic lens or complex internal nanostructures, which undermines the key advantages of OLEDs as an affordable planar light sources and tends to hinder their stable operation, thus putting a limitation to their commercialization.
Among various methods proven effective for OLED light extraction, a team led by Professor Seunghyup Yoo at the School of Electrical Engineering focused on the external scattering-based approach, as it can maintain planar geometry and compatibility with flexibility. It is also able to be fabricated on a large scale at a low cost and causes no interference with electrical properties of OLEDs.
Conventionally, research on enhancing OLED light extraction using light scattering has been conducted empirically in many cases. This time, the team developed comprehensive and analytical methodology to theoretically predict structures that maximize efficiency.
Considering OLEDs with the external scattering layers as a whole rather than two separate entities, the researchers combined the mathematical description of the scattering phenomena with the optical model for light emission within an OLED to rapidly predict the characteristics of many devices with various structures. Based on this approach, the team theoretically predicted the optimal combination of scattering layers and OLED architectures that can lead to the maximum efficiency.
Following this theoretical prediction, the team experimentally produced the optimal light scattering film and incorporated it to OLEDs with orange emitters having a high degree of horizontal dipole orientation. As a result, the team successfully realized OLEDs exhibiting EQE of 56% and power efficiency of 221 lm/W. This is one of the highest efficiencies ever realized for an OLED unit device without the help of a macroscopic lens or internal light extraction structures.
Professor Yoo said, “There are various technologies developed for improving OLED light extraction efficiency; nevertheless, most of them have not reached a level of practical use. This research mainly provides a systematic way to attain an EQE of 50% or higher in OLEDs while keeping in mind the constraints for commercialization. The approach shown here can readily be applied to lighting devices or sensors of wearable devices.”.
This research, co-led by Professor Jang-Joo Kim from Seoul National University and Professor Yun-Hi Kim from Gyeongsang National University, was published in Nature Communications on August 10, 2018. (J. Song et al. Nature Communications, 9, 3207. DOI: 10.1038/s41467-018-05671-x)
Figure 1.Photographs of OLEDs with SiO₂ -embedded scattering layers according to scatterance
2018.10.26 View 9734 -
A Novel Biosensor to Advance Diverse High-Level Production of Microbial Cell Factories
A research group at KAIST presented a novel biosensor which can produce diverse, high-level microbial cell factories. The biosensor monitors the concentration of products and even intermediates when new strains are being developed. This strategy provides a new platform for manufacturing diverse natural products from renewable resources. The team succeeded in creating four natural products of high-level pharmaceutical importance with this strategy.
Malonyl-CoA is a major building block for many value-added chemicals including diverse natural products with pharmaceutical importance. However, due to the low availability of malonyl-CoA in bacteria, many malonyl-CoA-derived natural products have been produced by chemical synthesis or extraction from natural resources that are harmful to the environment and are unsustainable. For the sustainable biological production of malonyl-CoA-derived natural products, increasing the intracellular malonyl-CoA pool is necessary. To this end, the development of a robust and efficient malonyl-CoA biosensor was required to monitor the concentration of intracellular malonyl-CoA abundance as new strains are developed.
Metabolic engineering researchers at KAIST addressed this issue. This research reports the development of a simple and robust malonyl-CoA biosensor by repurposing a type III polyketide synthase (also known as RppA), which produces flaviolin, a colorimetric indicator of malonyl-CoA. Subsequently, the RppA biosensor was used for the rapid and efficient colorimetric screening of gene manipulation targets enabling enhanced malonyl-CoA abundance. The screened beneficial gene targets were employed for the high-level production of four representative natural products derived from malonyl-CoA. Compared with the previous strategies, which were expensive and time-consuming, the new biosensor could be easily applied to industrially relevant bacteria including Escherichia coli, Pseudomonas putida, and Corynebacterium glutamicum to enable a one-step process.
The study employs synthetic small regulatory RNA (sRNA) technology to rapidly and efficiently reduce endogenous target gene expression for improved malonyl-CoA production. The researchers constructed an E. coli genome-scale synthetic sRNA library targeting 1,858 genes covering all major metabolic genes in E. coli. This library was employed with the RppA biosensor to screen for gene targets which are believed to be beneficial for enhancing malonyl-CoA accumulation upon their expression knockdown.
From this colorimetric screening, 14 gene targets were selected, all of which were successful at significantly increasing the production of four natural products (6-methylsalicylic acid, aloesone, resveratrol, and naringenin). Although specific examples are demonstrated in E. coli as a host, the researchers showed that the biosensor is also functional in P. putida and C. glutamicum, industrially important representative gram-negative and gram-positive bacteria, respectively. The malonyl-CoA biosensor developed in this research will serve as an efficient platform for the rapid development of strains capable of producing natural products crucial for the pharmaceutical, chemical, cosmetics, and food industries.
An important aspect of this work is that the high-performance strains constructed in this research were developed rapidly and easily by utilizing the simple approach of colorimetric screening, without involving extensive metabolic engineering approaches. 6-Methylsalicylic acid (an antibiotic) could be produced to the highest titer reported for E. coli, and the microbial production of aloesone (a precursor of aloesin, an anti-inflammatory agent/whitening agent) was achieved for the first time.
“A sustainable process for producing diverse natural products using renewable resources is of great interest. This study represents the development of a robust and efficient malonyl-CoA biosensor generally applicable to a wide range of industrially important bacteria. The capability of this biosensor for screening a large library was demonstrated to show that the rapid and efficient construction of high-performance strains is feasible. This research will be useful for further accelerating the development process of strains capable of producing valuable chemicals to industrially relevant levels,” said Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering, who led the research.
This study entitled “Repurposing type III polyketide synthase as a malonyl-CoA biosensor for metabolic engineering in bacteria,” was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) on October 02.
PhD students Dongsoo Yang and Won Jun Kim, MS student Shin Hee Ha, research staff Mun Hee Lee, Research Professor Seung Min Yoo, and Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering and Dr. Jong Hyun Choi of the Applied Microbiology Research Center at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) participated in this research.
Figure: Type III polyketide synthase (RppA) as a malonyl-CoA biosensor. RppA converts five molecules of malonyl-CoA into one molecule of red-colored flaviolin. This schematic diagram shows the overall conceptualization of the malonyl-CoA biosensor by indicating that higher malonyl-CoA abundance leads to higher production and secretion of flaviolin, resulting in a deeper red color of the culture. This system was employed for the enhanced production of four representative natural products (6-methylsalicylic acid, aloesone, resveratrol, and naringenin) from engineered E. coli strains.
2018.10.11 View 10780