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New Catalyst for Synthesizing Chiral Molecules Selectively
(from left: Dr. Yoonsu Park and Professor Sukbok Chang from the Department of Chemistry)
Molecules in nature often have “twin” molecules that look identical. In particular, the twin molecules that look like mirror images to each other are called enantiomers. However, even though they have the same type and number of elements, these twin molecules exhibit completely different properties.
Professor Sukbok Chang and Dr. Yoonsu Park from the Department of Chemistry developed a new catalyst capable of selectively synthesizing only one of the two enantiomers. Using this catalyst, the have succeeded in manufacturing the chiral lactam, an essential ingredient in pharmaceuticals, from a hydrocarbon compound.
Enantiomerism or chirality is considered very important for drug development. Biomaterials, such as DNAs and proteins also have chiral properties, but they exhibit different physiological activities depending on the types of drugs. One type of the enantiomer could be useful while the other is toxic. Hence, the technology for selective synthesizing (i.e. asymmetric synthesis) is required, but it is still regarded as a great challenge faced by modern chemistry to date.
The researchers solved this problem by developing a new catalyst. Earlier they presented their research on developing an iridium catalyst that converts hydrocarbons into high value γ-lactam compounds, and published it in Science in March 2018. However, the developed catalyst still had a limitation that both types of enantiomers are obtained without selectivity.
In this study, they found that among dozens of other catalyst candidates, iridium catalysts with chiral diamine scaffolds were able to select the correct enantiomer with a selectivity of 99% or more. This novel catalyst can be used to synthesize the various chiral γ-lactam as required. A left-handed γ-lactam and a right-handed γ-lactam can be produced using a left-handed iridium catalyst and a right-handed iridium catalyst, respectively.
They analyzed the reason for the high selectivity through computational chemistry simulations. They identified that temporal hydrogen bonding occurred between the chiral diamine catalysts and the hydrocarbon compound during the reaction. As a result of the hydrogen bonding, the formation of the left-handed lactam was boosted.
With their new catalyst, they also succeeded in synthesizing chiral lactam compounds with different structures. By using inexpensive and readily available feedstock hydrocarbons, the researchers produced a group of chiral lactams in different shapes. As their chirality and diverse structures enable lactams to function as an active compound in the body for antibiotic, anti-inflammatory, or anti-tumoral functions, this study may facilitate the development of potential drugs in a more efficient and cheaper way.
Professor Chang said, “We hope that our research on selectively producing core units of effective drugs will lead to developing new drugs that demonstrate fewer side-effects and higher efficacy. There are also economic advantages of this research because it uses hydrocarbon compounds, which can be abundantly found in nature, to produce high-value raw materials.
This research was published in Nature Catalysis(10.1038/s41929-019-0230-x) on February 19, 2019.
Figure 1. Asymmetric formation of chiral γ-lactam
Figure 2. Outline of research outcome
2019.03.05 View 6765 -
KAIST Develops Analog Memristive Synapses for Neuromorphic Chips
(Professor Sung-Yool Choi from the School of Electrical Engineering)
A KAIST research team developed a technology that makes a transition of the operation mode of flexible memristors to synaptic analog switching by reducing the size of the formed filament. Through this technology, memristors can extend their role to memristive synapses for neuromorphic chips, which will lead to developing soft neuromorphic intelligent systems.
Brain-inspired neuromorphic chips have been gaining a great deal of attention for reducing the power consumption and integrating data processing, compared to conventional semiconductor chips. Similarly, memristors are known to be the most suitable candidate for making a crossbar array which is the most efficient architecture for realizing hardware-based artificial neural network (ANN) inside a neuromorphic chip.
A hardware-based ANN consists of a neuron circuit and synapse elements, the connecting pieces. In the neuromorphic system, the synaptic weight, which represents the connection strength between neurons, should be stored and updated as the type of analog data at each synapse.
However, most memristors have digital characteristics suitable for nonvolatile memory. These characteristics put a limitation on the analog operation of the memristors, which makes it difficult to apply them to synaptic devices.
Professor Sung-Yool Choi from the School of Electrical Engineering and his team fabricated a flexible polymer memristor on a plastic substrate, and found that changing the size of the conductive metal filaments formed inside the device on the scale of metal atoms can make a transition of the memristor behavior from digital to analog.
Using this phenomenon, the team developed flexible memristor-based electronic synapses, which can continuously and linearly update synaptic weight, and operate under mechanical deformations such as bending.
The team confirmed that the ANN based on these memristor synapses can effectively classify person’s facial images even when they were damaged. This research demonstrated the possibility of a neuromorphic chip that can efficiently recognize faces, numbers, and objects.
Professor Choi said, “We found the principles underlying the transition from digital to analog operation of the memristors. I believe that this research paves the way for applying various memristors to either digital memory or electronic synapses, and will accelerate the development of a high-performing neuromorphic chip.”
In a joint research project with Professor Sung Gap Im (KAIST) and Professor V. P. Dravid (Northwestern University), this study was led by Dr. Byung Chul Jang (Samsung Electronics), Dr. Sungkyu Kim (Northwestern University) and Dr. Sang Yoon Yang (KAIST), and was published online in Nano Letters (10.1021/acs.nanolett.8b04023) on January 4, 2019.
Figure 1. a) Schematic illustration of a flexible pV3D3 memristor-based electronic synapse array. b) Cross-sectional TEM image of the flexible pV3D3 memristor
2019.02.28 View 7863 -
Novel Material Properties of Hybrid Perovskite Nanostructures for Next-generation Non-linear Electronic Devices
(from left: Juho Lee, Dr. Muhammad Ejaz Khan and Professor Yong-Hoon Kim)
A KAIST research team reported a novel non-linear device with the founding property coming from perovskite nanowires. They showed that hybrid perovskite-derived, inorganic-framework nanowires can acquire semi-metallicity, and proposed negative differential resistance (NDR) devices with excellent NDR characteristics that resulted from a novel quantum-hybridization NDR mechanism, implying the potential of perovskite nanowires to be realized in next-generation electronic devices.
Organic-inorganic hybrid halide perovskites have recently emerged as prominent candidates for photonic applications due to their excellent optoelectronic properties as well as their low cost and facile synthesis processes. Prominent progresses have been already made for devices including solar cells, light-emitting diodes, lasers and photodetectors.
However, research on electronic devices based on hybrid halide perovskites has not been actively pursued compared with their photonic device counterparts.
Professor Yong-Hoon Kim from the School of Electrical Engineering and his team took a closer look at low-dimensional organic-inorganic halide perovskite materials, which have enhanced quantum confinement effects, and particularly focused on the recently synthesized trimethylsulfonium (TMS) lead triiodide (CH3)3SPbI3.
Using supercomputer simulations, the team first showed that stripping the (CH3)3S or TMS organic ligands from the TMS PbI3 perovskite nanowires results in semi-metallic PbI3 columns, which contradicts the conventional assumption of the semiconducting or insulating characteristics of the inorganic perovskite framework.
Utilizing the semi-metallic PbI3 inorganic framework as the electrode, the team designed a tunneling junction device from perovskite nanowires and found that they exhibit excellent nonlinear negative differential resistance (NDR) behavior. The NDR property is a key to realizing next-generation, ultra-low-power, and multivalued non-linear devices. Furthermore, the team found that this NDR originates from a novel mechanism that involves the quantum-mechanical hybridization between channel and electrode states.
Professor Kim said, “This research demonstrates the potential of quantum mechanics-based computer simulations to lead developments in advanced nanomaterials and nanodevices. In particular, this research proposes a new direction in the development of a quantum mechanical tunneling device, which was the topic for which the Nobel Laureate in Physics in 1973 was awarded to Dr. Leo Esaki.
This research, led by Dr. Muhammad Ejaz Khan and PhD candidate Juho Lee, was published online in Advanced Functional Materials (10.1002/adfm.201807620) on January 7, 2019.
Figure. The draft version of the cover page of 'Advanced Functional Materials'
2019.02.22 View 6592 -
Brain-inspired Artificial Intelligence in Robots
(from left: PhD candidate Su Jin An, Dr. Jee Hang Lee and Professor Sang Wan Lee)
Research groups in KAIST, the University of Cambridge, Japan’s National Institute for Information and Communications Technology, and Google DeepMind argue that our understanding of how humans make intelligent decisions has now reached a critical point in which robot intelligence can be significantly enhanced by mimicking strategies that the human brain uses when we make decisions in our everyday lives.
In our rapidly changing world, both humans and autonomous robots constantly need to learn and adapt to new environments. But the difference is that humans are capable of making decisions according to the unique situations, whereas robots still rely on predetermined data to make decisions.
Despite the rapid progress being made in strengthening the physical capability of robots, their central control systems, which govern how robots decide what to do at any one time, are still inferior to those of humans. In particular, they often rely on pre-programmed instructions to direct their behavior, and lack the hallmark of human behavior, that is, the flexibility and capacity to quickly learn and adapt.
Applying neuroscience in robotics, Professor Sang Wan Lee from the Department of Bio and Brain Engineering, KAIST and Professor Ben Seymour from the University of Cambridge and Japan’s National Institute for Information and Communications Technology proposed a case in which robots should be designed based on the principles of the human brain. They argue that robot intelligence can be significantly enhanced by mimicking strategies that the human brain uses during decision-making processes in everyday life.
The problem with importing human-like intelligence into robots has always been a difficult task without knowing the computational principles for how the human brain makes decisions –in other words, how to translate brain activity into computer code for the robots’ ‘brains’.
However, researchers now argue that, following a series of recent discoveries in the field of computational neuroscience, there is enough of this code to effectively write it into robots. One of the examples discovered is the human brain’s ‘meta-controller’, a mechanism by which the brain decides how to switch between different subsystems to carry out complex tasks. Another example is the human pain system, which allows them to protect themselves in potentially hazardous environments. “Copying the brain’s code for these could greatly enhance the flexibility, efficiency, and safety of robots,” Professor Lee said.
The team argued that this inter-disciplinary approach will provide just as many benefits to neuroscience as to robotics. The recent explosion of interest in what lies behind psychiatric disorders such as anxiety, depression, and addiction has given rise to a set of sophisticated theories that are complex and difficult to test without some sort of advanced situation platform.
Professor Seymour explained, “We need a way of modelling the human brain to find how it interacts with the world in real-life to test whether and how different abnormalities in these models give rise to certain disorders. For instance, if we could reproduce anxiety behavior or obsessive-compulsive disorder in a robot, we could then predict what we need to do to treat it in humans.”
The team expects that producing robot models of different psychiatric disorders, in a similar way to how researchers use animal models now, will become a key future technology in clinical research.
The team also stated that there may also be other benefits to humans and intelligent robots learning, acting, and behaving in the same way. In future societies in which humans and robots live and work amongst each other, the ability to cooperate and empathize with robots might be much greater if we feel they think like us.
Professor Seymour said, “We might think that having robots with the human traits of being a bit impulsive or overcautious would be a detriment, but these traits are an unavoidable by-product of human-like intelligence. And it turns out that this is helping us to understand human behavior as human.”
The framework for achieving this brain-inspired artificial intelligence was published in two journals, Science Robotics (10.1126/scirobotics.aav2975) on January 16 and Current Opinion in Behavioral Sciences (10.1016/j.cobeha.2018.12.012) on February 6, 2019.
Figure 1. Overview of neuroscience - robotics approach for decision-making. The figure details key areas for interdisciplinary study (Current Opinion in Behavioral Sciences)
Figure 2. Brain-inspired solutions to robot learning. Neuroscientific views on various aspects of learning and cognition converge and create a new idea called prefrontal metacontrol, which can inspire researchers to design learning agents that can address various key challenges in robotics such as performance-efficiency-speed, cooperation-competition, and exploration-exploitation trade-offs (Science Robotics)
2019.02.20 View 5488 -
Kimchi Toolkit by Costa Rican Summa Cum Laude Helps Make the Best Flavor
(Maria Jose Reyes Castro with her kimchi toolkit application)
Every graduate feels a special attachment to their school, but for Maria Jose Reyes Castro who graduated summa cum laude in the Department of Industrial Design this year, KAIST will be remembered for more than just academics. She appreciates KAIST for not only giving her great professional opportunities, but also helping her find the love of her life.
During her master’s course, she completed an electronic kimchi toolkit, which optimizes kimchi’s flavor. Her kit uses a mobile application and smart sensor to find the fermentation level of kimchi by measuring its pH level, which is closely related to its fermentation. A user can set a desired fermentation level or salinity on the mobile application, and it provides the best date to serve it.
Under the guidance of Professor Daniel Saakes, she conducted research on developing a kimchi toolkit for beginners (Qualified Kimchi: Improving the experience of inexperienced kimchi makers by developing a monitoring toolkit for kimchi).
“I’ve seen many foreigners saying it’s quite difficult to make kimchi. So I chose to study kimchi to help people, especially those who are first-experienced making kimchi more easily,” she said. She got recipes from YouTube and studied fermentation through academic journals. She also asked kimchi experts to have a more profound understanding of it.
Extending her studies, she now works for a startup specializing in smart farms after starting last month. She conducts research on biology and applies it to designs that can be used practically in daily life.
Her tie with KAIST goes back to 2011 when she attended an international science camp in Germany. She met Sunghan Ro (’19 PhD in Nanoscience and Technology), a student from KAIST and now her husband. He recommended for her to enroll at KAIST because the school offers an outstanding education and research infrastructure along with support for foreign students.
At that time, Castro had just begun her first semester in electrical engineering at the University of Costa Rica, but she decided to apply to KAIST and seek a better opportunity in a new environment. One year later, she began her fresh start at KAIST in the fall semester of 2012.
Instead of choosing her original major, electrical engineering, she decided to pursue her studies in the Department of Industrial Design, because it is an interdisciplinary field where students get to study design while learning business models and making prototypes.
She said, “I felt encouraged by my professors and colleagues in my department to be creative and follow my passion. I never regret entering this major.”
When Castro was pursuing her master’s program in the same department, she became interested in interaction designs with food and biological designs by Professor Saakes, who is her advisor specializing in these areas.
After years of following her passion in design, she now graduates with academic honors in her department.
It is a bittersweet moment to close her journey at KAIST, but “I want to thank KAIST for the opportunity to change my life for the better. I also thank my parents for being supportive and encouraging me. I really appreciate the professors from the Department of Industrial Design who guided and shaped who I am,” she said.
Figure 1. The concept of the kimchi toolkit
Figure 2. The scenario of the kimchi toolkit
2019.02.19 View 4532 -
KAIST 2019 Commencement at a Glance
(KAIST 2019 Commencement Ceremony)
This year, KAIST awarded a total of 2,705 degrees: 654 PhD degrees, 1,255 master’s degrees, and 796 bachelor’s degrees. Including this year’s numbers, KAIST has conferred a total of 63,830 degrees since its foundation in 1971.
Parents, family, and friends came to campus to congratulate the graduates with big smiles and hugs. Faculty and staff members also attended the ceremony to celebrate their graduation. This year, distinguished guests including National Assembly Member Kyung-Jin Kim and Vice Minister for Science, Technology and Innovation Dae-sik came to celebrate the day with the KAIST community.
During the commencement, KAIST also announced the recipients of its undergraduate academic awards. The Minister of Science and ICT Award was won by Do-Yoon Kim from the Department of Aerospace Engineering, the KAIST Board of Trustee Chairperson Award went to Se-rin Lee from the Department of Materials Science and Engineering, the KAIST Presidential Award was won by Hee-Ju Kim from the Department of Physics, the KAIST Alumni Association President Award went to Hyeon-Seong Park from the School of Electrical Engineering, and finally the KAIST Development Foundation Chairperson Award was won by Gyeong-Hoon Lee from the Department of Mathematical Sciences.
This year’s valedictorian Eun-Seok Jeong from the School of Computing said, “I believe that we are able to stand here today because we challenged ourselves to confront our shortcomings and our uncertainty. If we continue to develop, we will become a better person than we were yesterday.”
(KAIST President Sung-Chul Shin and Woo-Seok Jeong, '19 PhD in Aerospace Engineering)
As a KAIST alumnus and fellow scientist, President Sung-Chul Shin offered his congratulations and emphasized that graduates should continue to pursue the C³ spirit. “In this age of great transformation, embrace challenges and exercise creativity as you have learnt through your education and research at KAIST. And keep in mind the importance of caring for others. Please remember that challenge and creativity will have more meaning if rendered with a caring spirit,” he said.
2019.02.15 View 8602 -
The First Award for Concept Cars, Future Mobility of the Year
KAIST will host an award to recognize the most visionary and inspiring concept cars of the year.
The ‘Future Mobility of the Year (FMOTY)’ Awards recognize concept cars that have made outstanding contributions to future mobility. The first awards ceremony will take place in Korea in March 2019.
The awards will be given to concept cars that exhibit innovative services and practical transportation technology in three categories: private mobility, public and commercial mobility, and personal mobility.
To ensure a fair judging process, the contest invited influential and eminent journalists in the automotive field. They will evaluate the social values and innovative contributions of the concept cars that will pave the way for next-generation transportation.
Concept cars have been neglected in existing automobile awards, such as the ‘Car of the Year’ because they have been considered experimental prototypes only built for showcasing a new vision for the quite far future.
The FMOTY Awards will brings concept cars back into the spotlight and showcase the best ideas and social values of mind-blowing concept cars.
Among 45 concept cars, fifteen candidates were selected as finalists after the initial screening that took place over the last three months: including models from Audi, BMW, Mercedes-Benz, Peugeot, Porsche, Renault, Toyota, Volkswagen, and Volvo. The winners will be announced and awarded in Seoul on March 28th.
Kyung-soo Kim, Dean of the Cho Chun Shik Graduate School of Green Transportation which organizes the award said, “As the automobile industry undergoes an era of transformation, it is crucial to recognize the efforts of automobile companies who are making attempts to create novel forms of mobility. That is why we launched the FMOTY Awards, hoping to add a future-oriented spirit to the existing awards that consider finished vehicles only. By selecting the best concept car, the FMOTY Awards will expand public attention from the present to the future.”
Details can be found on the official website of FMOTY ( www.fmoty.org), where photos of the finalists are also available for download ( http://bitly.kr/JTUUp).
Figure 1. Finalists for the 'Future Mobility of the Year'
2019.02.13 View 6222 -
Kenya-KAIST Kicks off with a 95-Million USD Funding from the Korean Government
KAIST, founded through a six-million USD loan from USAID in 1971, to provide turnkey-based education consultancy for Kenya’s first advanced science and technology institute.
KAIST and the Konza Technopolis Development Authority (KoTDA) announced the official establishment of Kenya-KAIST by 2021 during a kickoff ceremony on February 12 in Kenya. The KAIST delegation headed by President Sung-Chul Shin and Kenyan cabinet members and dignitaries including Minister of Education Amina Mohamed, the Chairman of the KoTDA Reuben Mutiso, and the CEO of KoTDA John Tanui attended the ceremony.
With this kickoff held at Konza Technopolis Malili, KAIST, the first and top science and technology university in Korea, will participate in Kenya’s strategic economic development plan with the provision of a turnkey-based science and technology education consultancy for the establishment of Kenya’s first advanced institute of science and technology. KAIST, which won preferred bidder status in consortium with Samwoo and Sunjin architecture and engineering companies, signed the contract with the KoTDA last November.
Korea Eximbank will offer a 95-million USD economic development cooperation fund loan to the Kenyan government. The campus will be constructed in the Konza Techno City located near Nairobi by 2021, with the first batch of 200 graduate students starting classes in 2022.
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 groundwork for engineering research and education in Kenya to meet emerging socioeconomic demands. In addition, KAIST will provide education in the basic science areas of math, physics, chemistry, and biology for students.
The Kenyan government plans to transform Kenya into a middle-income country under Vision 2030 through the promotion of science, technology, and innovation for national economic growth. Nicknamed Africa’s Silicon Savannah, Konza Techno City is a strategic science and technology hub constructed to realize this vision. To this end, the medium-term plan set a goal to provide specialized research and training in various cutting-edge engineering and advanced science fields.
It is also notable that the Kenyan government asked to develop an industry-academy cooperation program in the Konza Techno City. This reflects the high expectations for Kenya-KAIST and its role as a growth engine 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 upon completion, positioning Kenya as an ICT hub within the region.
Saying that the partnership through Kenya-KAIST will bring a new future to Kenya as well as KAIST at the ceremony, President Shin reflected that the project will be a significant milestone for KAIST’s history and global competitiveness. He added, “With this Kenya project, we come to share the past, present, and future of KAIST. And I am very pleased to celebrate our shared vision: the empowerment of science, technology, and education.”
In particular, President Shin was accompanied by Dr. Kun-Mo Chung, a founding provost who served as the Minister of Science and Technology in Korea twice. He now serves as an advisor to Kenyan President Uhuru Kenyatta.
Dr. Chung had played a crucial role in securing a six-million USD loan from US AID to the Korean government to establish KAIST in 1971. He proposed the idea to establish an advanced science and technology institute in Korea to Dr. John Hannah, then the director of US AID.
The seed that was sowed five decades ago in Korea by Dr. Chung has now fully bloomed in Kenya. In only a half century, KAIST has become a donor institution that passes on science and technology education systems including the construction of campuses to developing countries.
KAIST has been acclaimed as US AID’s most successful foreign aid project. A report from the National Academy of Sciences in the US described KAIST as an exemplary case in which a former recipient of international aid has grown to become a science, technology and innovation leader.
The kickoff of Kenya-KAIST drew the attention of both media and local universities in Kenya, attesting to their strong interest to drive economic growth through advanced science and technology.
The University of Nairobi also hosted a special lecture by President Shin, asking him to share the recipe for the success of KAIST in Korea. In a lecture titled “A Crucial Engine for Rapid National Development,” President Shin presented the vision, innovation, and passion of the Korean people that led to the phenomenal results we can see today.
The successful case of KAIST has been benchmarked by many countries for years. For instance, KAIST set up the curriculum for the nuclear engineering program at the Khalifa University of Science and Technology in UAE in 2010. Since 2015, Chongquing University of Technology in China has been running its electrical engineering and computer science programs based on the educational systems and curricula offered by KAIST.
Last 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, as it carries out a turnkey-based project that encompasses every aspect of institution building, ranging from educational curricular development to campus construction and supervision.
Figure 1. KAIST President Sung-Chul Shin and Principal Secretary of Ministry of Education Collette A. Suda
Figure 2. Kickoff Ceremony of Kenya-KAIST
Figure 3. Conceptual image of Kenya KAIST
2019.02.13 View 6867 -
New LSB with Theoretical Capacity over 90%
(Professor Hee-Tak Kim and Hyunwon Chu)
A KAIST research team has developed a lithium sulfur battery (LSB) that realizes 92% of the theoretical capacity and an areal capacity of 4mAh/cm2.
LSBs are gaining a great deal of attention as an alternative for lithium ion batteries (LIBs) because they have a theoretical energy density up to six to seven times higher than that of LIBs, and can be manufactured in a more cost-effective way.
However, LSBs face the obstacle of having a capacity reaching its theoretical maximum because they are prone to uncontrolled growth of lithium sulfide on the electrodes, which leads to blocking electron transfer.
To address the problem of electrode passivation, researchers introduced additional conductive agent into the electrode; however, it drastically lowered the energy density of LSBs, making it difficult to exceed 70% of the theoretical capacity.
Professor Hee-Tak Kim from the Department of Chemical and Biomolecular Engineering and his team replaced the lithium salt anions used in conventional LSB electrolytes with anions with a high donor number. The team successfully induced the three-dimensional growth of lithium sulfide on electrode surfaces and efficiently delayed the electrode passivation.
Based on this electrolyte design, the research team achieved 92% of the theoretical capacity with their high-capacity sulfur electrode (4mAh/cm2), which is equivalent to that of conventional LIB cathode. Furthermore, they were able to form a stable passivation film on the surface of the lithium anode and exhibited stable operation over 100 cycles.
This technology, which can be flexibly used with various types of sulfur electrodes, can mark a new milestone in the battery industry.
Professor Kim said, “We proposed a new physiochemical principle to overcome the limitations of conventional LSBs. I believe our achievement of obtaining 90% of the LBSs’ theoretical capacity without any capacity loss after 100 cycles will become a new milestone.”
This research, first-authored by Hyunwon Chu and Hyungjun Noh, was published in Nature Communications on January 14, 2019. It was also selected in the editor’s highlight for its outstanding achievements.
Figure 1. Lithium sulfur growth and its deposition mechanism for different sulfide growth behaviors
Figure 2. Capacity and cycle life characteristics of the LSBs
2019.02.11 View 7184 -
KAIST Develops Core Technology for Ultra-small 3D Image Sensor
(from left: Dr. Jong-Bum Yo, PhD candidate Seong-Hwan Kimand Professor Hyo-Hoon Park)
A KAIST research team developed a silicon optical phased array (OPA) chip, which can be a core component for three-dimensional image sensors. This research was co-led by PhD candidate Seong-Hwan Kim and Dr. Jong-Bum You from the National Nanofab Center (NNFC).
A 3D image sensor adds distance information to a two-dimensional image, such as a photo, to recognize it as a 3D image. It plays a vital role in various electronics including autonomous vehicles, drones, robots, and facial recognition systems, which require accurate measurement of the distance from objects.
Many automobile and drone companies are focusing on developing 3D image sensor systems, based on mechanical light detection and ranging (LiDAR) systems. However, it can only get as small as the size of a fist and has a high possibility of malfunctioning because it employs a mechanical method for laser beam-steering.
OPAs have gained a great attention as a key component to implement solid-state LiDAR because it can control the light direction electronically without moving parts. Silicon-based OPAs are small, durable, and can be mass-produced through conventional Si-CMOS processes.
However, in the development of OPAs, a big issue has been raised about how to achieve wide beam-steering in transversal and longitudinal directions. In the transversal direction, a wide beam-steering has been implemented, relatively easily, through a thermo-optic or electro-optic control of the phase shifters integrated with a 1D array. But the longitudinal beam-steering has been remaining as a technical challenge since only a narrow steering was possible with the same 1D array by changing the wavelengths of light, which is hard to implement in semiconductor processes.
If a light wavelength is changed, characteristics of element devices consisting the OPA can vary, which makes it difficult to control the light direction with reliability as well as to integrate a wavelength-tunable laser on a silicon-based chip. Therefore, it is essential to devise a new structure that can easily adjust the radiated light in both transversal and longitudinal directions.
By integrating tunable radiator, instead of tunable laser in a conventional OPA, Professor Hyo-Hoon Park from the School of Electrical Engineering and his team developed an ultra-small, low-power OPA chip that facilitates a wide 2D beam-steering with a monochromatic light source.
This OPA structure allows the minimizing of the 3D image sensors, as small as a dragonfly’s eye.
According to the team, the OPA can function as a 3D image sensor and also as a wireless transmitter sending the image data to a desired direction, enabling high-quality image data to be freely communicated between electronic devices.
Kim said, “It’s not an easy task to integrate a tunable light source in the OPA structures of previous works. We hope our research proposing a tunable radiator makes a big step towards commercializing OPAs.”
Dr. You added, “We will be able to support application researches of 3D image sensors, especially for facial recognition with smartphones and augmented reality services. We will try to prepare a processing platform in NNFC that provides core technologies of the 3D image sensor fabrication.”
This research was published in Optics Letters on January 15.
Figure 1.The manufactured OPA chip
Figure 2. Schematic feature showing an application of the OPA to a 3D image sensor
2019.02.08 View 6225 -
KAIST Earns AACSB Business School Accreditation
The KAIST College of Business re-earned business school accreditation from the Association to Advance Collegiate Schools of Business (AACSB) International. The school first earned the accreditation in 2003, and has continued to receive the accreditation four consecutive times. Currently only 5% of the 16,000 business schools around the world have earned AACSB accreditation. KAIST received a good evaluation for the competitive research of its faculty, its executive education programs based on strong industry-academia ties, and specialized MBA and master’s program, which includes programs such as social entrepreneurship and green business and policy.Alexander Triantis, dean of the Robert H. Smith School of Business at the University of Maryland and a judge for AACSB Accreditation said, “I was impressed to see students from KAIST have a high standard of knowledge. A number of its graduates continue to be appointed as professors of top universities abroad, which shows its strong global competence”. AACSB was founded in 1916 by deans of business colleges from prestigious universities such as Harvard University, Stanford University and Columbia University, to provide business and accounting accreditation to universities. Evaluation for AACSB accreditation takes place every five years. Schools are evaluated based on fifteen standards, including student admission and graduation requirements, student-faculty ratios, faculty’s intellectual contributions, research infrastructure, global cooperation, and industry-academia programs. They can be eligible for re-accreditation if they satisfy the conditions offered by AACSB International and are committed to continuous improvement every five years. KAIST also earned the accreditation from the European Foundation for Management Development Quality Improvement System (EQUIS) three consecutive times since 2010. In 2013, it earned membership into the Partnership in International Management (PIM). Membership is only possible for those who have AACSB and EQUIS accreditation and they can be listed as a candidate school through voting. The candidate schools can finally earn membership after one year of strict screening. As of January 2019, there are 65 prestigious graduate schools of business, including KAIST, listed as PIM members.
2019.02.01 View 4947 -
Stretchable Multi-functional Fiber for Energy Harvesting and Strain Sensing
(from left: Professor Steve Park, Jeongjae Ryu and Professor Seungbum Hong)
Fiber-based electronics are expected to play a vital role in next-generation wearable electronics. Woven into textiles, they can provide higher durability, comfort, and integrated multi-functionality. A KAIST team has developed a stretchable multi-functional fiber (SMF) that can harvest energy and detect strain, which can be applied to future wearable electronics.
With wearable electronics, health and physical conditions can be assessed by analyzing biological signals from the human body, such as pulse and muscle movements. Fibers are highly suitable for future wearable electronics because they can be easily integrated into textiles, which are designed to be conformable to curvilinear surfaces and comfortable to wear. Moreover, their weave structures offer support that makes them resistant to fatigue. Many research groups have developed fiber-based strain sensors to sense external biological signals. However, their sensitivities were relatively low.
The applicability of wearable devices is currently limited by their power source, as the size, weight, and lifetime of the battery lessens their versatility. Harvesting mechanical energy from the human body is a promising solution to overcome such limitations by utilizing various types of motions like bending, stretching, and pressing. However, previously reported, fiber-based energy harvesters were not stretchable and could not fully harvest the available mechanical energy.
Professor Seungbum Hong and Professor Steve Park from the Department of Materials Science and Engineering and their team fabricated a stretchable fiber by using a ferroelectric layer composed of P(VDF-TrFE)/PDMS sandwiched between stretchable electrodes composed of a composite of multi-walled carbon nanotubes (MWCNT) and poly 3,4-ethylenedioxythiophene polystyrenesulfonate (PEDOT:PSS).
Cracks formed in MWCNT/PEDOT:PSS layer help the fiber show high sensitivity compared to the previously reported fiber strain sensors. Furthermore, the new fiber can harvest mechanical energy under various mechanical stimuli such as stretching, tapping, and injecting water into the fiber using the piezoelectric effect of the P(VDF-TrFE)/PDMS layer.
Professor Hong said, “This new fiber has various functionalities and makes the device simple and compact. It is a core technology for developing wearable devices with energy harvesting and strain sensing capabilities.”
This article, led by PhD candidate Jeongjae Ryu, was published in the January 2019 issue of Nano Energy.
Figure 1.Schematic illustration of an SMF fiber and its piezoelectric voltage output and response to strain.
Figure 2. Photographs of a stretchable multi-functional fiber being stretched by 100%, bent, and twisted.
2019.01.31 View 7544