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Extremely Stable Perovskite Nanoparticles Films for Next-Generation Displays
Researchers have reported an extremely stable cross-linked perovskite nanoparticle that maintains a high photoluminescence quantum yield (PLQY) for 1.5 years in air and harsh liquid environments. This stable material’s design strategies, which addressed one of the most critical problems limiting their practical application, provide a breakthrough for the commercialization of perovskite nanoparticles in next-generation displays and bio-related applications. According to the research team led by Professor Byeong-Soo Bae, their development can survive in severe environments such as water, various polar solvents, and high temperature with high humidity without additional encapsulation. This development is expected to enable perovskite nanoparticles to be applied to high color purity display applications as a practical color converting material. This result was published as the inside front cover article in Advanced Materials. Perovskites, which consist of organics, metals, and halogen elements, have emerged as key elements in various optoelectronic applications. The power conversion efficiency of photovoltaic cells based on perovskites light absorbers has been rapidly increased. Perovskites are also great promise as a light emitter in display applications because of their low material cost, facile wavelength tunability, high (PLQY), very narrow emission band width, and wider color gamut than inorganic semiconducting nanocrystals and organic emitters. Thanks to these advantages, perovskites have been identified as a key color-converting material for next-generation high color-purity displays. In particular, perovskites are the only luminescence material that meets Rec. 2020 which is a new color standard in display industry. However, perovskites are very unstable against heat, moisture, and light, which makes them almost impossible to use in practical applications. To solve these problems, many researchers have attempted to physically prevent perovskites from coming into contact with water molecules by passivating the perovskite grain and nanoparticle surfaces with organic ligands or inorganic shell materials, or by fabricating perovskite-polymer nanocomposites. These methods require complex processes and have limited stability in ambient air and water. Furthermore, stable perovskite nanoparticles in the various chemical environments and high temperatures with high humidity have not been reported yet. The research team in collaboration with Seoul National University develops siloxane-encapsulated perovskite nanoparticle composite films. Here, perovskite nanoparticles are chemically crosslinked with thermally stable siloxane molecules, thereby significantly improving the stability of the perovskite nanoparticles without the need for any additional protecting layer. Siloxane-encapsulated perovskite nanoparticle composite films exhibited a high PLQY (> 70%) value, which can be maintained over 600 days in water, various chemicals (alcohol, strong acidic and basic solutions), and high temperatures with high humidity (85℃/85%). The research team investigated the mechanisms impacting the chemical crosslinking and water molecule-induced stabilization of perovskite nanoparticles through various photo-physical analysis and density-functional theory calculation. The research team confirmed that displays based on their siloxane-perovskite nanoparticle composite films exhibited higher PLQY and a wider color gamut than those of Cd-based quantum dots and demonstrated perfect color converting properties on commercial mobile phone screens. Unlike what was commonly believed in the halide perovskite field, the composite films showed excellent bio-compatibility because the siloxane matrix prevents the toxicity of Pb in perovskite nanoparticle. By using this technology, the instability of perovskite materials, which is the biggest challenge for practical applications, is greatly improved through simple encapsulation method. “Perovskite nanoparticle is the only photoluminescent material that can meet the next generation display color standard. Nevertheless, there has been reluctant to commercialize it due to its moisture vulnerability. The newly developed siloxane encapsulation technology will trigger more research on perovskite nanoparticles as color conversion materials and will accelerate early commercialization,” Professor Bae said. This work was supported by the Wearable Platform Materials Technology Center (WMC) of the Engineering Research Center (ERC) Project, and the Leadership Research Program funded by the National Research Foundation of Korea. -Publication: Junho Jang, Young-Hoon Kim, Sunjoon Park, Dongsuk Yoo, Hyunjin Cho, Jinhyeong Jang, Han Beom Jeong, Hyunhwan Lee, Jong Min Yuk, Chan Beum Park, Duk Young Jeon, Yong-Hyun Kim, Byeong-Soo Bae, and Tae-Woo Lee. “Extremely Stable Luminescent Crosslinked Perovskite Nanoparticles under Harsh Environments over 1.5 Years” Advanced Materials, 2020, 2005255. https://doi.org/10.1002/adma.202005255. Link to download the full-text paper: https://onlinelibrary.wiley.com/doi/10.1002/adma.202005255 -Profile: Prof. Byeong-Soo Bae (Corresponding author) email@example.com Lab. of Optical Materials & Coating Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST)
Ultrathin but Fully Packaged High-Resolution Camera
- Biologically inspired ultrathin arrayed camera captures super-resolution images. - The unique structures of biological vision systems in nature inspired scientists to design ultracompact imaging systems. A research group led by Professor Ki-Hun Jeong have made an ultracompact camera that captures high-contrast and high-resolution images. Fully packaged with micro-optical elements such as inverted micro-lenses, multilayered pinhole arrays, and gap spacers on the image sensor, the camera boasts a total track length of 740 μm and a field of view of 73°. Inspired by the eye structures of the paper wasp species Xenos peckii, the research team completely suppressed optical noise between micro-lenses while reducing camera thickness. The camera has successfully demonstrated high-contrast clear array images acquired from tiny micro lenses. To further enhance the image quality of the captured image, the team combined the arrayed images into one image through super-resolution imaging. An insect’s compound eye has superior visual characteristics, such as a wide viewing angle, high motion sensitivity, and a large depth of field while maintaining a small volume of visual structure with a small focal length. Among them, the eyes of Xenos peckii and an endoparasite found on paper wasps have hundreds of photoreceptors in a single lens unlike conventional compound eyes. In particular, the eye structures of an adult Xenos peckii exhibit hundreds of photoreceptors on an individual eyelet and offer engineering inspiration for ultrathin cameras or imaging applications because they have higher visual acuity than other compound eyes. For instance, Xenos peckii’s eye-inspired cameras provide a 50 times higher spatial resolution than those based on arthropod eyes. In addition, the effective image resolution of the Xenos peckii’s eye can be further improved using the image overlaps between neighboring eyelets. This unique structure offers higher visual resolution than other insect eyes. The team achieved high-contrast and super-resolution imaging through a novel arrayed design of micro-optical elements comprising multilayered aperture arrays and inverted micro-lens arrays directly stacked over an image sensor. This optical component was integrated with a complementary metal oxide semiconductor image sensor. This is first demonstration of super-resolution imaging which acquires a single integrated image with high contrast and high resolving power reconstructed from high-contrast array images. It is expected that this ultrathin arrayed camera can be applied for further developing mobile devices, advanced surveillance vehicles, and endoscopes. Professor Jeong said, “This research has led to technological advances in imaging technology. We will continue to strive to make significant impacts on multidisciplinary research projects in the fields of microtechnology and nanotechnology, seeking inspiration from natural photonic structures.” This work was featured in Light Science & Applications last month and was supported by the National Research Foundation (NRF) of and the Ministry of Health and Welfare (MOHW) of Korea. Image credit: Professor Ki-Hun Jeong, KAIST Image usage restrictions: News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only. Publication: Kisoo Kim, Kyung-Won Jang, Jae-Kwan Ryu, and Ki-Hun Jeong. (2020) “Biologically inspired ultrathin arrayed camera for high-contrast and high-resolution imaging”. Light Science & Applications. Volume 9. Article 28. Available online at https://doi.org/10.1038/s41377-020-0261-8 Profile: Ki-Hun Jeong Professor firstname.lastname@example.org http://biophotonics.kaist.ac.kr/ Department of Bio and Brain Engineering KAIST Profile: Kisoo Kim Ph.D. Candidate email@example.com http://biophotonics.kaist.ac.kr/ Department of Bio and Brain Engineering KAIST (END)
Wearable Strain Sensor Using Light Transmittance Helps Measure Physical Signals Better
KAIST researchers have developed a novel wearable strain sensor based on the modulation of optical transmittance of a carbon nanotube (CNT)-embedded elastomer. The sensor is capable of sensitive, stable, and continuous measurement of physical signals. This technology, featured in the March 4th issue of ACS Applied Materials & Interfaces as a front cover article, shows great potential for the detection of subtle human motions and the real-time monitoring of body postures for healthcare applications. A wearable strain sensor must have high sensitivity, flexibility, and stretchability, as well as low cost. Those used especially for health monitoring should also be tied to long-term solid performance, and be environmentally stable. Various stretchable strain sensors based on piezo-resistive and capacitive principles have been developed to meet all these requirements. Conventional piezo-resistive strain sensors using functional nanomaterials, including CNTs as the most common example, have shown high sensitivity and great sensing performance. However, they suffer from poor long-term stability and linearity, as well as considerable signal hysteresis. As an alternative, piezo-capacitive strain sensors with better stability, lower hysteresis, and higher stretchability have been suggested. But due to the fact that piezo-capacitive strain sensors exhibit limited sensitivity and strong electromagnetic interference caused by the conductive objects in the surrounding environment, these conventional stretchable strain sensors are still facing limitations that are yet to be resolved. A KAIST research team led by Professor Inkyu Park from the Department of Mechanical Engineering suggested that an optical-type stretchable strain sensor can be a good alternative to resolve the limitations of conventional piezo-resistive and piezo-capacitive strain sensors, because they have high stability and are less affected by environmental disturbances. The team then introduced an optical wearable strain sensor based on the light transmittance changes of a CNT-embedded elastomer, which further addresses the low sensitivity problem of conventional optical stretchable strain sensors. In order to achieve a large dynamic range for the sensor, Professor Park and his researchers chose Ecoflex as an elastomeric substrate with good mechanical durability, flexibility, and attachability on human skin, and the new optical wearable strain sensor developed by the research group actually shows a wide dynamic range of 0 to 400%. In addition, the researchers propagated the microcracks under tensile strain within the film of multi-walled CNTs embedded in the Ecoflex substrate, changing the optical transmittance of the film. By doing so, it was possible for them to develop a wearable strain sensor having a sensitivity 10 times higher than conventional optical stretchable strain sensors. The proposed sensor has also passed the durability test with excellent results. The sensor’s response after 13,000 sets of cyclic loading was stable without any noticeable drift. This suggests that the sensor response can be used without degradation, even if the sensor is repeatedly used for a long time and in various environmental conditions. Using the developed sensor, the research team could measure the finger bending motion and used it for robot control. They also developed a three-axes sensor array for body posture monitoring. The sensor was able to monitor human motions with small strains such as a pulse near the carotid artery and muscle movement around the mouth during pronunciation. Professor Park said, “In this study, our group developed a new wearable strain sensor platform that overcomes many limitations of previously developed resistive, capacitive, and optical-type stretchable strain sensors. Our sensor could be widely used in a variety of fields including soft robotics, wearable electronics, electronic skin, healthcare, and even entertainment.” This work was supported by the National Research Foundation (NRF) of Korea. Publication: Jimin Gu, Donguk Kwon, Junseong Ahn, and Inkyu Park. (2020) “Wearable Strain sensors Using Light Transmittance Change of Carbon Nanotube-Embedded Elastomers with Microcracks” ACS Applied Materials & Interfaces. Volume 12. Issue 9. Available online at https://doi.org/10.1021/acsami.9b18069 Profile: Inkyu Park Professor firstname.lastname@example.org http://mintlab1.kaist.ac.kr Micro/Nano Transducers Laboratory (MINT Lab) Department of Mechanical Engineering (ME)Korea Advanced Institute of Science and Technology (KAIST) Profile: Jimin Gu Ph.D. Candidate email@example.com http://mintlab1.kaist.ac.kr MINT Lab KAIST ME (END)
Transformative Electronics Systems to Broaden Wearable Applications
Imagine a handheld electronic gadget that can soften and deform when attached to our skin. This will be the future of electronics we all dreamed of. A research team at KAIST says their new platform called 'Transformative Electronics Systems' will open a new class of electronics, allowing reconfigurable electronic interfaces to be optimized for a variety of applications. A team working under Professor Jae-Woong Jeong from the School of Electrical Engineering at KAIST has invented a multifunctional electronic platform that can mechanically transform its shape, flexibility, and stretchability. This platform, which was reported in Science Advances, allows users to seamlessly and precisely tune its stiffness and shape. "This new class of electronics will not only offer robust, convenient interfaces for use in both tabletop or handheld setups, but also allow seamless integration with the skin when applied onto our bodies," said Professor Jeong. The transformative electronics consist of a special gallium metal structure, hermetically encapsulated and sealed within a soft silicone material, combined with electronics that are designed to be flexible and stretchable. The mechanical transformation of the electronic systems is specifically triggered by temperature change events controlled by the user. "Gallium is an interesting key material. It is biocompatible, has high rigidity in solid form, and melts at a temperature comparable to the skin's temperature," said lead author Sang-Hyuk Byun, a researcher at KAIST. Once the transformative electronic platform comes in contact with a human body, the gallium metal encapsulated inside the silicone changes to a liquid state and softens the whole electronic structure, making it stretchable, flexible, and wearable. The gallium metal then solidifies again once the structure is peeled off the skin, making the electronic circuits stiff and stable. When flexible electronic circuits were integrated onto these transformative platforms, it empowered them with the ability to become either flexible and stretchable or rigid. "This technology could not have been achieved without interdisciplinary efforts," said co-lead author Joo Yong Sim, who is a researcher with ETRI. "We worked together with electrical, mechanical, and biomedical engineers, as well as material scientists and neuroscientists to make this breakthrough." This universal electronics platform allowed researchers to demonstrate applications that were highly adaptable and customizable, such as a multi-purpose personal electronics with variable stiffness and stretchability, a pressure sensor with tuneable bandwidth and sensitivity, and a neural probe that softens upon implantation into brain tissue. Applicable for both traditional and emerging electronics technologies, this breakthrough can potentially reshape the consumer electronics industry, especially in the biomedical and robotic domains. The researchers believe that with further development, this novel electronics technology can significantly impact the way we use electronics in our daily life. < Transformative electronics in soft mode,which becomes wearable for outdoor applications.> Video Material: https://youtu.be/im0J18TfShk Publication: Sang-Hyuk Byun, Joo Yong Sim, Zhanan Zhou, Juhyun Lee, Raza Qazi, Marie C. Walicki, Kyle E. Parker, Matthew P. Haney, Su Hwan Choi, Ahnsei Shon, Graydon B. Gereau, John Bilbily, Shuo Li, Yuhao Liu, Woon-Hong Yeo, Jordan G. McCall, Jianliang Xiao, and Jae-Woong Jeong. 2019. Mechanically transformative electronics, sensors, and implantable devices. Science Advances. Volume 5. No. 11. 12 pages. https://doi.org/10.1126/sciadv.aay0418 Link to download the full-text paper: https://advances.sciencemag.org/content/advances/5/11/eaay0418.full.pdf Profile: Prof. Jae-Woong Jeong, PhD firstname.lastname@example.org https://www.jeongresearch.org/ Professor Bio-Integrated Electronics and Systems Laboratory School of Electrical Engineering Korea Advanced Institute of Science and Technology (KAIST) https://www.kaist.ac.kr Daejeon 34141, Korea Profile: Sang-Hyuk Byun, PhD Candidate email@example.com (END)
KAIST and Google Jointly Develop AI Curricula
KAIST selected the two professors who will develop AI curriculum under the auspices of the KAIST-Google Partnership for AI Education and Research. The Graduate School of AI announced the two authors among the 20 applicants who will develop the curriculum next year. They will be provided 7,500 USD per subject. Professor Changho Suh from the School of Electrical Engineering and Professor Yong-Jin Yoon from the Department of Mechanical Engineering will use Google technology such as TensorFlow, Google Cloud, and Android to create the curriculum. Professor Suh’s “TensorFlow for Information Theory and Convex Optimization “will be used for curriculum in the graduate courses and Professor Yoon’s “AI Convergence Project Based Learning (PBL)” will be used for online courses. Professor Yoon’s course will explore and define problems by utilizing AI and experiencing the process of developing products that use AI through design thinking, which involves product design, production, and verification. Professor Suh’s course will discus“information theory and convergence,” which uses basic sciences and engineering as well as AI, machine learning, and deep learning.
Sangeun Oh Recognized as a 2017 Google Fellow
Sangeun Oh, a Ph.D. candidate in the School of Computing was selected as a Google PhD Fellow in 2017. He is one of 47 awardees of the Google PhD Fellowship in the world. The Google PhD Fellowship awards students showing outstanding performance in the field of computer science and related research. Since being established in 2009, the program has provided various benefits, including scholarships worth $10,000 USD and one-to-one research discussion with mentors from Google. His research work on a mobile system that allows interactions among various kinds of smart devices was recognized in the field of mobile computing. He developed a mobile platform that allows smart devices to share diverse functions, including logins, payments, and sensors. This technology provides numerous user experiences that existing mobile platforms could not offer. Through cross-device functionality sharing, users can utilize multiple smart devices in a more convenient manner. The research was presented at The Annual International Conference on Mobile Systems, Applications, and Services (MobiSys) of the Association for Computing Machinery in July, 2017. Oh said, “I would like to express my gratitude to my advisor, the professors in the School of Computing, and my lab colleagues. I will devote myself to carrying out more research in order to contribute to society.” His advisor, Insik Shin, a professor in the School of Computing said, “Being recognized as a Google PhD Fellow is an honor to both the student as well as KAIST. I strongly anticipate and believe that Oh will make the next step by carrying out good quality research.”
Professor Otfried Cheong Named as Distinguished Scientist by ACM
Professor Otfried Cheong (Schwarzkopf) of the School of Computing was named as a Distinguished Scientist of 2016 by the Association for Computing Machinery (ACM). The ACM recognized 45 Distinguished Members in the category of Distinguished Scientist, Educator, and Engineer for their individual contributions to the field of computing. Professor Cheong is the sole recipient from a Korean institution. The recipients were selected among the top 10 percent of ACM members with at least 15 years of professional experience and five years of continuous professional membership. He is known as one of the authors of the widely used computational geometry textbook Computational Geometry: Algorithms and Applications and as the developer of Ipe, a vector graphics editor. Professor Cheong joined KAIST in 2005, after earning his doctorate from the Free University of Berlin in 1992. He previously taught at Ultrecht University, Pohang University of Science and Technology, Hong Kong University of Science and Technology, and the Eindhoven University of Technology.
Nanoparticle Cluster Manufacturing Technique Using DNA Binding Protein Developed
Professor Hak-Sung Kim of the Department of Biological Sciences at KAIST and Yiseul Ryu, a doctoral candidate, used the Zinc Finger protein that specifically binds to target DNA sequence to develop a new manufacturing technique for size-controllable magnetic Nanoparticle Clusters (NPCs). Their research results were published in Angewandte Chemie International Edition online on 25 November 2014. NPCs are structures consisting of magnetic nanoparticles, gold nanoparticles, and quantum dots, each of which are smaller than 100 nm (10-9m). NPCs have a distinctive property of collectivity not seen in single nanoparticles. Specifically NPCS differ in physical and optical properties such as Plasmon coupling absorbance, energy transfers between particles, electron transfers, and conductivity. Therefore, NPCs can be employed in biological and medical research as well as the development of nanoelectric and nanoplasmon devices. To make use of these novel properties, the size and the composition of the cluster must be exquisitely controlled. However, previous techniques relied on chemical binding which required complex steps, making it difficult to control the size and composition of NPCs. Professor Kim’s team used Zinc Finger, a DNA binding protein, to develop a NPCs manufacturing technique to create clusters of the desired size easily. The Zinc Finger protein contains a zinc ion and specifically recognizes DNA sequence upon binding, which allows the exquisite control of the size and the cluster composition. The technique is also bio-friendly. Professor Kim’s team created linear structure of different sizes of NPCs using Zinc Finger proteins and three DNA sequences of different lengths. The NPCs they produced confirmed their ability to control the size and structure of the cluster by using different DNA lengths. The NPCs showed tripled T2 relaxation rates compared to the existing MRI contrast media (Feridex) and effectively transported to targeted cells. The research findings show the potential use of NPCs in biological and medical fields such as MRI contrast media, fluorescence imaging, and drug transport. The research used the specific binding property of protein and DNA to develop a new method to create an inorganic nanoparticle’s supramolecular assembly. The technique can be used and applied extensively in other nanoparticles for future research in diagnosis, imaging, and drug and gene delivery. Figure 1. A Mimetic Diagram of NPCs Manufacturing Technique Using DNA Binding Protein Zinc Finger Figure 2. Transmission Electron Microscopy Images showing different sizes of NPCs depending on the length of the DNA
KAIST placed the 5th in top 50 global universities for international patent applications
New York Times released an article, dated March 19, 2012, on the statistics of international patent applications filed by global universities during 2011, and with 103 applications published, KAIST was listed the fifth among the top 50 universities, right behind four US universities: University of California (277), the Massachusetts Institute of Technology (179), the University of Texas System (127), and Johns Hopkins University (111). A total of seven Korean universities including KAIST made the top 50 list. For the article, please check the link below: New York Times, March 19, 2012 “U.S. Universities Retain Lead in Patent Applications” By Christopher F. Schuetze http://www.nytimes.com/2012/03/19/world/asia/us-universities-retain-lead-in-patent-applications.html In addition, for the press release by the World Intellectual Property Organization, the UN agency responsible for the Patent Cooperation Treaty, on international patent filings in 2011, please click the following link: “International Patent Filings Set new Record in 2011” http://www.wipo.int/pressroom/en/articles/2012/article_0001.html
Professor Choi Han Lim receives Automatica Applications Paper Price
Professor Choi Han Lim of the Department of Aerospace received ‘Automatica Applications Paper Prize’ for the first time ever for a Korean. Professor Choi published a paper in the Automatica magazine with the topic of ‘Continuous Trajectory Planning of Mobile Sensors for Informative Forecasting’. Professor Choi dealt with most efficient measuring methods for mobile sensor platforms thereby improving the performance of anticipating environmental changes and proposed key theories for problem solving and also an efficient algorithm. The research was conducted in cooperation with MIT Department of Aerospace Professor Jonathan How with the support of the National Science Foundation. Automatica Journal published by the International Federation of Automatic Control and has been awarding the Automatica Paper Prize every three years.
Professor Hwang Kyu Young Receives Outstanding Contributions Award from DASFAA
Professor Hwang Kyu Young received the 2011 Outstanding Contributions Award from the International Conference on Database Systems for Advanced Applications (DASFAA). Professor Hwang was the Chairman, Vice Chairman, Executive, etc. of the DASFAA Steering Committee for the past 12 years and has been leading the development in the field of database in the Asia/Pacific Region. He was also the editor in chief of The VLDB Journal which is the leading magazine in the field of database and the member of ACM SIGMOD Jim Gray Dissertation Award Committee, VLDB 10-year Best Paper Award Committee, and IEEE ICDE Influential Paper Awards Committee. He receives the Outstanding Contributions Award for ensuring high standards in world database research.
Prof. Cho Elected Editor-in-Chief of Systems Biology
Prof. Kwang-Hyun Cho of Department of Bio and Brain Engineering at KAIST has been recently elected editor-in-chief of the Systems Biology, an international journal published by the London-based Institution of Engineering and Technology (IET), the university authorities said on Wednesday (Sept. 23) By the year 2012, Cho will oversee the editorial process of the journal covering intra- and inter-cellular dynamics, using systems- and signal-oriented approaches. IET, one of the world"s leading professional societies for the engineering and technology community, has a worldwide membership of more than 150,000. Prof. Cho"s research interests cover the areas of systems science with bio-medical applications including systems biology and bio-inspired engineering based on molecular systems biology. He is currently an editorial board member of Systems and Synthetic Biology (Springer, Netherlands, from 2006), BMC Systems Biology (BMC, London, U.K., from 2007), Gene Regulation and Systems Biology (Libertas Academica, New Zealand, from 2007), and Bulletin of Mathematical Biology (Springer, New York, from 2008), and an editorial advisory board member of Molecular BioSystems (The Royal Society of Chemistry, U.K.).
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