- High-performance sensor devices for short- and mid-range LiDAR applications - Expected to localize LiDAR sensor devices by developing based on a semiconductor mass production process LiDAR sensors are indispensable for the realization of advanced technologies such as advanced driver assistance systems (ADAS), autonomous driving, and AR/VR. In particular, short- and mid-range LiDAR used in AR/VR devices and smartphones requires better distance (depth) resolution to detect the shape of a person or object more accurately, and so a single-photon detector with better timing jitter performance is required. LiDAR measures distance and creates a 3D image by calculating the time it takes for a photon emitted by the transmitter to strike an object, reflect, and arrive back at the receiver. The slight difference in detection time that occurs when the single-photon detector at the receiver converts the light signal into an electrical signal is called "timing jitter," and the smaller the value of this jitter, the more accurately the object can be recognized. The Korea Institute of Science and Technology (KIST) announced that a team led by Dr. Myung-Jae Lee at the Post-Silicon Semiconductor Institute has developed a "single-photon avalanche diode (SPAD)" that can identify objects at the mm level based on a 40nm back-illuminated CMOS image sensor process. SPADs, which are ultra-high-performance sensor devices that can detect single photons, are extremely difficult to develop, and to date, only Sony of Japan has successfully commercialized SPAD-based LiDAR based on its 90nm back-illuminated CMOS image sensor process and supplied it to Apple products. Sony's SPAD shows better efficiency than back-illuminated SPADs reported in the literature, but its timing-jitter performance of about 137~222ps is insufficient to realize user discrimination, gesture recognition, and accurate shape recognition of objects required in short- and mid-range LiDAR applications. The single-photon sensor element developed by KIST has significantly improved the timing-jitter performance by more than two times to 56 ps, and the distance resolution has also been improved to about 8 mm, which has great potential for utilization as a short and mid-range LiDAR sensor element. In particular, since the SPAD was developed based on the 40nm back-illuminated CMOS image sensor process, a semiconductor process for mass production, through joint research with SK hynix, it is expected to be immediately localized and commercialized. "If commercialized as a core source technology for semiconductor LiDAR and 3D image sensors, it will greatly enhance our competitiveness in next-generation system semiconductors, which are Korea's strategic industries," said Myung-Jae Lee, principal investigator at KIST. [Fig 1] Simplified cross-section of a single-photon avalanche diode KIST single-photon avalanche diode developed in SK hynix's 40 nm back-illuminated CMOS image sensor technology [Fig 2] Semiconductor chip with ultra-high-performance sensor elements developed by Dr. Myung-Jae Lee's research team at KIST's Advanced Semiconductor Devices and Systems Laboratory (ADS Lab) [Fig 3] Dr. Myung-Jae Lee’s research team, Post-Silicon Semiconductor Institute, KIST (ADS Lab) ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, supported by the Korea Institute of Science and Technology (KIST) Institution Program (Grant No. 2E32242) and the National Research Foundation of Korea (NRF) (Grant No. 2021M3D1A2046731), was presented on December 12 at the International Electron Devices Meeting 2023 (IEDM 2023), held from December 9 to 13 in San Francisco, USA. IEDM is one of the most prestigious conferences for semiconductor industry and research experts, including major global semiconductor companies such as SK hynix, Samsung Electronics, and Intel.

- Implementing the 'neuron-synapse-neuron' basic unit structure in hardware for high-performance, low-power neuromorphic computing - Same material, same structure for processability and network scalability With the emergence of new industries such as artificial intelligence, the Internet of Things, and machine learning, the world's leading companies are focusing on developing next-generation artificial intelligence semiconductors that can process vast amounts of data while consuming energy efficiently. Neuromorphic computing, inspired by the human brain, is one of them. As a result, devices that mimic biological neurons and synapses are being developed one after another based on emerging materials and structures, but research on integrating individual devices into a system to verify and optimize them is still lacking. In order for large-scale artificial neural network hardware to become practical in the future, it is essential to integrate artificial neuron and synaptic devices, and it is necessary to reduce mass production costs and energy usage by fabricating devices with the same materials and structures. A team led by Dr. Joon Young Kwak of the Center for Neuromorphic Engineering at the Korea Institute of Science and Technology (KIST) announced that they have implemented an integrated element technology for artificial neuromorphic devices that can connect neurons and synapses like "Lego blocks" to construct large-scale artificial neural network hardware. The team fabricated vertically stacked memristor devices using hBN, a two-dimensional material that is advantageous for high integration and ultra-low power implementation, to demonstrate biological neurons and synapses characteristics. Since the team designed artificial neuron and synaptic devices with the same material and the same structure, unlike conventional silicon CMOS-based artificial neural imitation devices with complex structures using multiple devices, the devices developed by the team have secured ease of process and network scalability, paving the way for the development of large-scale artificial neural network hardware. By integrating and connecting the developed devices, the team also successfully implemented the "neuron-synapse-neuron" structure, the basic unit block of an artificial neural network, in hardware to demonstrate spike signal-based information transmission, which is how the human brain works. By experimentally verifying that the modulation of spike signal information between two neurons can be adjusted according to the synaptic weights of the artificial synaptic device, the researchers showed the potential of using hBN-based emerging devices for low-power, large-scale AI hardware systems. "Artificial neural network hardware systems can be used to efficiently process vast amounts of data generated in real-life applications such as smart cities, healthcare, next-generation communications, weather forecasting, and autonomous vehicles," said KIST's Dr. Joon Young Kwak, explaining the significance of the research achievement. "It will help improve environmental issues such as carbon emissions by significantly reducing energy usage while exceeding the scaling limits of existing silicon CMOS-based devices." [Fig 1] Experimental results of modulating the connection strength of front and back neurons by synaptic weights. (a) Schematic diagram of a biological neural network and (b) circuit schematic of an artificial neural network implemented in hardware using an artificial neuromorphic device. (c) Experimental results of the change in connection strength between two neurons as the synaptic weight changes. It is observed that the degree of firing of the downstream neuron decreases as the synaptic weight decreases. [Fig 2] Two-dimensional material-based volatile and nonvolatile memory devices (a) Schematic representation of two-dimensional material-based volatile and non-volatile memory devices (top) and measured electrical properties of fabricated devices (bottom); (b) Electron micrographs (top) and transmission electron micrographs (bottom) of fabricated devices. Utilizing fabricated devices to emulate biological neuron and synapse properties. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research was funded by the Ministry of Science and ICT (Minister Jong-Ho Lee)'s Next Generation Intelligent Semiconductor Technology Development (Device) Project (2021M3F3A2A01037738) and KIST's Institutional Program and was published in the international journal Advanced Functional Materials (IF: 19.0, JCR(%): 4.2) online on November 5. Journal : Advanced Functional Materials Title : Hardware Implementation of Network Connectivity Relationships Using 2D hBN-Based Artificial Neuron and Synaptic Devices Publication Date : 2023.11.05. DOI : https://doi.org/10.1002/adfm.202309058

- Novel approach for real-time detection of ultra-low levels of hydrogen gas leakageusing palladium materials embedded in Terahertz Metamaterials. - Successfully elucidation of underlying mechanism of metal-light interaction during a genesis of nano-water film Hydrogen gas is the smallest and lightest of all known molecules, and its colorless and odorless nature makes it easy to leak. Also when concentrated above 4% in a confined space, it poses a risk of ignition or explosion. In order for hydrogen to become a major player in the future energy industry, it is essential to ensure the safety issues via ultra-sensitive gas detection technology over the entire gas-dealing processes such as gas production, storage, and transportation. However, conventional gas-leakage sensors using electric signals are prone to yield electrical sparks, which can cause an explosion of leaked hydrogen gas. In addition, the mainstream electrode-based contact sensors affect the effective signal stability depending on the device's contact state showing weak signal fidelity. Thus, it is desirable for achieving stable, non-explosive via non-contact mode detection for removing any possible dangers have been spiring to develop a secure device that does not lead to disaster situations. The Korea Institute of Science and Technology (KIST) announced that a team led by Dr. Minah Seo of the Sensor Systems Research Center & KU-KIST Graduate School and Prof. Yong-Sang Ryu of School of Biomedical Engineering, College of Health Sciences, Korea University, has developed a non-contact terahertz light sensor. This can detect hydrogen gas leaks as small as 0.25% in real-world environments at room temperature and pressure, which is the world-top level of limit-of-detection performance via optical detection methods. Spectroscopy is the non-contact observation method measuring changes in the value of optical constants of an analytic sample. In this method, changes in the reacting substance are observed non-invasively, by measuring variations in the optical properties when the reacting substance encounters hydrogen gas. Terahertz electromagnetic waves have a very wide frequency band, which makes them sensitive to the natural vibrations of gas molecules, and can be utilized in spectroscopy to resolve minute unique information and differences in molecules such as various gases, DNA, and amino acids. However, due to the low probability of interaction with trace amounts of hydrogen gas and the lack of technology to amplify the signal of terahertz waves, it has been difficult to utilize in practice. The research team focused on the property of hydrogen permeating into palladium metal, and devised a research strategy to address this through the interaction of light and matter. The researchers developed a gas-detection sensing platform that can sensitively measure changes in terahertz optical signals caused by trace amounts of gas using metamaterials that have the ability to amplify signals in specific bands of electromagnetic waves. The team first developed a terahertz metamaterial that can amplify signals in the gas-sensitive terahertz band, and then uniformly applied palladium to the metamaterial to create an extremely narrow 14 nm space to maximize the sensitivity of the terahertz signal. The palladium plays bifunctional roles in not only the catalytic reaction of adsorbed hydrogen and oxygen to produce water molecules on the surface, but also in the hydrogen storage. For mimicry of real-world environments (80 % of Nitrogen, 20 % of Oxygen), Hydrogen and oxygen gases were then injected into the developed sensing chamber and exposed to the terahertz sensing platform. The results showed great responsibility with respect to exposed hydrogen gas via significant optical signal variation, and these were scientifically analyzed in a real-time fashion. The usage of ultra-thin palladium together with ultra-sensitive optical band width (the terahertz) provided synergetic performance enabling to detect under 1% of hydrogen gas leakage to the real-time detection level. Not only for the superior detection performance, but also the reusability of the detection platforms was considered during platform designing process. In general, metal hydrides such as palladium are difficult to reuse because they are irreversible, meaning they cannot return to their original state after a phase change, but the KIST-Korea University research team secured the reusability of the sample through special processing technology. They also succeeded in developing a technology to contactlessly track the mechanism of hydrogen desorption at the nanometer scale in real time through optical signals. "Existing light sensors have very limited reliability in normal temperature, pressure, and humidity environments, but this is a promising technology that can detect and screen not only gases but also various biochemical substances in extremely small amounts by dramatically increasing sensitivity," said Dr. Minah Seo, lead author of the study. "It is expected to be used to develop a system that can immediately respond to various harmful factors, gases, and diseases through mobile, on-site, and real-time inspections." "In addition to the terahertz measurement technology, it has opened up the possibility of visually checking various gas adsorption and desorption processes and molecular-level chemical reaction mechanisms occurring on metal surfaces," said Professor Ryu Yong-sang of Korea University, lead author of the study. [Fig 1] Observe the metastructure and optical constants of the palladium-catalyzed reaction as a function of the concentration ratio of hydrogen and oxygen, the thickness of the resulting water layer, and the resulting terahertz signal changes. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research was supported by the KIST Major Project, the National Research Foundation of Korea (No. 2023R1A2C2003898 , and 2021R1A2C2009236) from the Ministry of Science and ICT (Minister Lee Jong-ho), the KIST Major Project, the KU-KIST School Program of Korea University, and the Korea University Intramural Project, and the results were published online on November 23 in the international journal Advanced Materials (IF 29.4, JCR 2.2%). Journal : Advanced Materials Title : Advancements in intense terahertz field focusing over metallic nanoarchitectures for monitoring hidden interatomic gas-matter interactions Publication Date : 2023.11.23. DOI : https://doi.org/10.1002/adma.202308975

- Single-pixel imaging successfully achieved for the first time using an organic-based photoelectric photodetector - Energy-efficient imaging in low-light conditions, facilitating human-computer interaction, shows promise for application in smart indoor environments Organic-based optoelectronic technology is increasingly recognized as an energy-efficient solution for low-power indoor electronics and wireless IoT sensors. This is largely due to its superior flexibility and light weight compared to conventional silicon-based devices. Notably, organic photovoltaic cells (OPVs) and organic photodetectors (OPDs) are leading examples in this field. OPVs have the remarkable ability to absorb energy and generate electricity even under very low light condition, while OPDs are capable of capturing images. However, despite their potential, the development of these devices has been conducted independently thus far. As a result, they have not yet reached the level of efficiency necessary to be considered practical for next-generation, miniaturized devices. The Korea Institute of Science and Technology (KIST), led by Dr. Min-Chul Park and Dr. Do Kyung Hwang of the Center for Opto-Electronic Materials and Devices, Prof. Jae Won Shim and Prof. Tae Geun Kim of the School of Electrical Engineering at Korea University, Prof. JaeHong Park of the Department of Chemistry and Nanoscience at Ewha Womans University, have developed an organic-based optoelcectronic device. This innovative device not only integrates the functionalities of organic photovoltaic cells (OPVs) and organic photodetectors (OPDs) but also pioneers in visualizing images in applications requiring low-light conditions, thereby enhancing energy efficiency in indoor environments. By advancing the organic semiconductor layer into a multicomponent structure, the research team has enhanced the device's performance. In door environments, it achieves an impressive photoelectric conversion efficiency exceeding 32%, along with a linear dynamic range surpassing 130 dB. This significant improvement in contrast ratio, especially in low-light conditions, allows for a much clearer image than conventional silicon devices, which typically offer a linear dynamic range of 100 dB. The collaborative research team made further strides by successfully applying single-pixel image sensing. This image sensing system capture ambient light, transforms into electrical energy, and utilize this energy to acquire images. In contrast to the previous need for specialized cameras in low-light of standard lighting conditions, the newly developed photodetector, featuring a multi-component semiconductor layer, offers a versatile application. It can function not only as a conventional camera but also as a decorative element on windows or walls, providing sufficient resolution to discern shapes and movements of objects. Dr. Min-chul Park from KIST highlighted the versatility of this technology, noting, "While primarily functioning as an energy harvester, it can also be applied to detect movement and recognize motion patterns in environments without light." He further expressed optimism about its potential applications, stating, "This holds great promise not only for human-computer interaction (HCI) research but also in various industrial sectors, including smart indoor environments." [Fig 1] Dual-function integrated image sensor Organics-based optoelectronic technology is gaining attention as an energy-efficient and environmentally friendly electronic device for Internet of Things (IoT)-based wireless sensors and low-power indoor electronics. Among them, organic photovoltaic (OPV) and organic photodetector (OPD) efficiently utilize ambient unutilized or low-light to generate electricity and detect light to implement images. Organic photovoltaics (OPVs) can be used to harvest indoor energy, while organic photodetectors (OPDs) can be used like cameras, utilizing indoor light for imaging as needed. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ This research was supported by the Ministry of Science and ICT (Minister Lee Jong-ho) as a KIST Institutional Program, a mid-career research support project of the Korea Research Foundation, and a Leader Research Project, and the results have been published in the international journal Advanced Materials (IF: 29.4, JCR(%): 2.312) and published online on November 2023. Journal : Advanced Materials Title : Self-Powering Sensory Device with Multi-Spectrum Image Realization for Smart Indoor Environments Publication Date : 2023.11.16. DOI : https://doi.org/10.1002/adma.202307523

- Virus elimination effect along with a wide range of colors achieved with a low coating amount of 1g/m2 - Expected to be utilized in various industries such as medical materials, home appliances, building materials, etc. Since the onset of COVID-19, we've become accustomed to seeing antiviral films attached to elevator buttons and public transportation handles. However, conventional antiviral films are made by mixing antiviral metal particles with polymers. Due to the manufacturing process, only a very small fraction of these metal particles is exposed on the surface. As a result, contrary to the belief that these films will protect us from viruses, the actual antiviral effect upon contact with the film surface is not significant. The Korea Institute of Science and Technology (KIST) has announced that a collaborative research team led by Dr. So-Hye Cho from the Materials Architecturing Research Center and Dr. Seung Eun Lee of the Research Animal Resources Center has developed a nanocoating technology that not only maximizes the antiviral activity of the surface, but also enables the realization of various colors. The research team has developed an effective antiviral and antibacterial surface by using the sol-gel method to form a silica coating layer on various surfaces, followed by coating the silica layer with silver (Ag) nanoparticles using an aqueous solution containing silver. In turn, silver nanoparticles limit the infectivity of viruses by binding to the proteins on the virus surface, disrupting the structure and function of the virus, and making it difficult for the virus to penetrate cells. In conventional antiviral films, antiviral functional metal particles are embedded within the thin film, making it difficult for silver to come in contact with viruses. However, the technology developed by the KIST research team showcased remarkable activity with a small amount of silver nanoparticles positioned on the thin film's surface. Experiments involving lentiviruses, developed as analogs to coronaviruses, demonstrated a virus elimination rate more than twice as fast compared to commercial films. In addition, antibacterial tests against E. coli bacteria resulted in complete eradication of the bacteria within 24 hours. The developed antiviral coating technology also has the additional advantage of providing various colors by controlling light interference through different coating layer thickness. "This metal nanoparticle coating technology demonstrates superior antiviral and antibacterial effects compared to commercial products, even with a small coating of less than 1 g/m2, so its industrialization potential is very high," said Dr. So-Hye Cho of KIST. "It can be used in various industries such as medical materials, home appliances, and building materials to help manage microorganisms and prevent infections by implementing antiviral and antibacterial effects." [Fig 1] SEM/TEM analysis of the silica layer showing well-defined silver nanoparticles on the surface. [Fig 2] Comparison of antiviral effectiveness of commercial silver nanofilms versus self-developed surfaces [Fig 3] Comparison of antibacterial effectiveness of commercial silver nanofilms versus device developed surfaces ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, which was supported by the Ministry of Science and ICT (Minister Lee Jong-ho) through the Korea Research Foundation-Nano and Materials Technology Development Project (2020M3H4A3106354), KIST Future Source Research Project (2E32511), and K-DARPA Innovative Technology Development Project, was published online in the international journal ACS Applied Materials and Interfaces (IF: 9.5, JCR(%): 7.956) on November 9, 2023. Journal : ACS Applied Materials and Interfaces Title : In Situ Metal Deposition on Perhydropolysilazane-Derived Silica for Structural Color Surfaces with Antiviral Activity Publication Date : 2023.11.09. DOI : https://doi.org/10.1021/acsami.3c12622

- East Asian and North American cold snap anomalies are caused by mid-latitude ocean fronts, not sea ice - Important predictor fornear-term climate change on a decadal time scale If the world is warming, why are our winters getting colder? Indeed, East Asia and North America have experienced frequent extreme weather events since the 2000s that defy average climate change projections. Many experts have blamed Arctic warming and a weakening jet stream due to declining Arctic sea ice, but climate model experiments have not adequately demonstrated their validity. The massive power outage in Texas in February 2021 was caused by an unusual cold snap, and climate models are needed to accurately predict the risk of extreme weather events in order to prevent massive socioeconomic damage. In particular, climate technology leaders have recently set the ability to predict the climate of the next decade or so as an important goal. The Korea Institute of Science and Technology (KIST) announced that senior researcher Mi-Kyung Sung of the Sustainable Environment Research Center and professor Soon-Il An of the Center for Irreversible Climate Change at Yonsei University (President Seung-hwan Seo) have jointly discovered the role of mid-latitude oceans as a source of anomalous waves that are particularly frequent in East Asia and North America, paving the way for a mid- to long-term response to winter climate change. Ocean currents have a major impact on the weather and climate of neighboring countries as they transport not only suspended and dissolved matter but also heat energy. In particular, regions where temperatures change rapidly in a narrow latitudinal band, such as the Gulf Stream in the Atlantic Ocean and the downstream region of the Kuroshio Current in the Pacific Ocean, are called "ocean fronts," and the KIST-Yonsei joint research team attributes the atmospheric wave response to the excessive accumulation of heat in these ocean fronts as the cause of the increase in extreme cold waves. From the early 2000s until recently, anomalous cold trend in East Asia coincided with the accumulation of heat near the Gulf Stream in the North Atlantic, and that in North America coincided with the intensification of heat accumulation near the Kuroshio Current. The oceanic frontal region acts as a thermostat to control the frequency of winter cold waves and anomalous high temperatures. The process of heat accumulation in oceanic frontal regions lasts from years to decades. During this time, a warming hiatus can occur in the continental regions that bucks the global warming trend. Conversely, during decades of ocean frontal cooling, continental regions appear to experience a sharp acceleration of warming. This suggests that the recent decadal cooling trend is essentially reinforced by temporary natural variability in the global climate system, and that we can expect unseasonably warm winter weather to become more prevalent as the heat buildup in the ocean front is relieved. These results are also evident in climate model experiments that vary the amount of heat accumulation near ocean fronts, showing that observations and climate model experiments are consistent in their conclusions, in contrast to conventional sea ice theory. This highlights the importance of accurately simulating ocean front variability in climate models to improve our ability to predict medium- and long-term climate change over the next decade. As global warming intensifies in the future and changes the structure of the ocean, these regional climate variations could change dramatically. Climate model experiments with increased greenhouse gases have shown that North America is likely to experience shorter and fewer warming hiatus, while East Asia is likely to experience more frequent intersections between warming hiatus and acceleration. These different continental responses are driven by the different oceanic responses of the Kuroshio Current and the Gulf Stream to global warming. "Applying the effects of ocean fronts revealed in this research to global warming climate models can improve climate change forecasts for the near future," said Dr. Mi-Kyung Sung of KIST. "It will provide important references for long-term forecasts of winter energy demand and the construction of climate change response infrastructure to prevent climate disasters such as the 2021 Texas power outage." [Fig 1] Winter temperature trend - Observed temperature trends during the winters (Dec-Feb) of 1995/96-2021/22. [Fig 2] Atlantic & Pacific ocean fronts - Ocean fronts near the Gulf Stream and Kuroshio Currents that represent narrow regions where sea surface temperature sharply decreases northward. [Fig 3(Attachment notes)] Gulf stream & East Asia covariability - Decadal cooling in East Asia accompanied by Gulf Stream warming (climate model simulation) ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, which was funded by the Ministry of Science and ICT (Minister Jong-ho Lee) through the Mid-Career Researcher Support Project (2021R1A2C1003934), the Leading Research Center Support Project (2018R1A5A1024958), and the Ultra-High Performance Computing Utilization Advancement Project (2022M3K3A1094114), was published on November 27 in the international journal Nature Communications Journal : Nature Communications Title : Ocean fronts as decadal thermostats modulating continental warming hiatus Publication Date : 2023.11.27. DOI : https://doi.org/10.1038/s41467-023-43686-1

The global consumption of pharmaceuticals is growing rapidly every year, reaching 4 billion doses in 2020. As more and more pharmaceuticals are metabolized by the human body and enter sewage and wastewater treatment plants, the amount and types of trace substances found in them are also increasing. When these trace substances enter rivers and oceans and are used as water sources, they can have harmful effects on the environment and human health, including carcinogenesis and endocrine disruption. Therefore, technologies are needed to quickly and accurately predict the properties and behavior of these trace substances, but analyzing unknown trace substances requires expensive equipment, skilled experts, and a long time. The Korea Institute of Science and Technology (KIST) announced that a team led by Hong Seok-won, head of the Water Resources and Cycle Research Center, and Son Moon, a senior researcher, has developed a technology to classify emerging trace substances according to their physicochemical properties and predict their concentrations using clustering and prediction-based artificial intelligence technology. The researchers used self-organizing maps, an AI technique that clusters data into maps based on their similarities, to classify 29 known trace substances, including medicinal compounds and caffeine, based on information such as physicochemical properties, functional groups, and biological reaction mechanisms. Random forests, a machine learning technique that classifies data into subsets, were then further built to predict the properties and concentration changes of new trace substances. If a new trace substance belongs to a cluster in the self-organizing map, the properties of other substances in that cluster can be used to predict how the properties and concentration of the new trace substance will change. As a result of applying this clustering and prediction AI model (self-organizing map and random forest) to 13 new trace substances, the prediction accuracy of about 0.75 was excellent, far exceeding the prediction accuracy of 0.40 of existing AI techniques using biological information. Compared to traditional prediction methods based on formulas, the KIST research team's data-driven analysis model has the advantage of only inputting the physicochemical properties of trace substances and efficiently identifying how the concentration of new trace substances will change in the sewage treatment process through clustering with substances with similar data. In addition, the data-driven AI model can be used in the future to predict the concentration of new substances such as drugs that are of social concern. "It can be applied not only to actual wastewater treatment plants, but also to most water treatment-related facilities where new trace substances exist, and can provide quick and accurate data in the policy-making process for related regulations," said Dr. Seokwon Hong and Dr. Moon Son (co-corresponding authors) of KIST. “Since it utilizes machine learning technology, the accuracy of the prediction will improve as relevant data is accumulated.” [Fig 1] Machine learning approaches for predicting the behavior of new trace substances ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ This study was supported by the Korea Environment Industry & Technology Institute through the "Project for developing innovative drinking water and wastewater technologies," funded by the Korea Ministry of Environment [Grant No. 2019002710010], and the National Research Foundation of Korea (NRF) grant, funded by the Korean government (MSIT) [No. 2021R1C1C2005643]. The results were published in the October issue of the npj Clean Water (IF: 11.4, top 1.5% in JCR Water Resources). Journal : npj Clean water Title : Clustering micropollutants and estimating rate constants of sorption and biodegradation using machine learning approaches Publication Date : 2023.10.28. DOI : https://doi.org/10.1038/s41545-023-00282-6

- Developing a hybrid energy harvester that goes beyond simple coupling of thermoelectric and piezoelectric devices to generate higher power - Commercial GPS positioning sensor runs successfully, showing promise for real-world applications Harvesting energy sources such as heat, vibration, light, and electromagnetic waves from everyday environments such as industrial sites and automobiles and converting them into electrical energy is known as energy harvesting. Energy harvesting makes it easier to power today's popular IoT sensors and wireless devices that are located in environments where battery replacement is difficult. Dr. Hyun-Cheol Song and Dr. Sunghoon Hur of Electronic Materials Research Center at the Korea Institute of Science and Technology (KIST) have developed a hybrid energy harvesting system that increases power production by more than 50% by combining thermoelectric and piezoelectric effects. The thermoelectric effect, which converts thermal energy from both ends of the device into electrical energy, has a low energy conversion efficiency, and the piezoelectric effect, which converts mechanical vibration into electrical energy, has a high impedance, so energy cannot be reliably harvested. To overcome the limitations of single-mode energy harvesters, hybrid energy harvesters have been proposed in the past, but they are mainly based on simply combining the energy generated by each mechanism. In response, the KIST research team developed a thermoelectric-piezoelectric hybrid energy harvester that complements the shortcomings of thermoelectric and piezoelectric devices to create a synergistic effect in environments with heat sources and vibrations. First, instead of a heat sink, which is a static shape with a large cross-sectional area that is bulky and in contact with air, a cantilever was fabricated to improve the heat dissipation effect in a vibration environment, resulting in a thermoelectric device output that was improved by more than 25%. The researchers also proposed a hybrid energy harvesting structure in which a polymer-type piezoelectric device (MFC) was attached to the cantilever to generate additional power by generating tensile and compressive deformation of the piezoelectric device as the cantilever shakes. The research team successfully applied this hybrid energy harvester to stably drive a commercial IoT sensor (GPS positioning sensor, 3 V, 20 mW), demonstrating the potential for future IoT sensors to run continuously without battery power supply. "This study confirms that the hybrid energy harvesting system can be reliably applied to our real life," said Dr. Sunghoon Hur of KIST, who led the research. "We have confirmed its effectiveness in places where heat and vibration exist together, such as automobile engines, and are currently planning to build a system that can be applied to factory facilities or construction machinery engines that are difficult to supply power and diagnose their condition wirelessly." [Fig 1] Thermoelectric-voltaic hybrid harvester utilizing a cantilevered dynamic heat sink developed by KIST researchers [Fig 2] Graph showing the characteristics of a thermoelectric-voltaic hybrid harvester utilizing a cantilevered dynamic heat sink. [Fig 3] Illustration and graph showing that the output of a thermoelectric-piezoelectric hybrid harvester can be used to reduce IoT sensor drive time, increasing hybrid power due to the synergy of the thermoelectric-piezoelectric mechanism. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research was supported by the Ministry of Science and ICT (Minister Jong-ho Lee) as Institutional Program of KIST and was published in the latest issue of Energy Conversion and Management (IF: 10.4, top 1.8% in JCR), an international journal in the energy field. Journal : Energy Conversion and Management Title : A synergetic effect of piezoelectric energy harvester to enhance thermoelectric Power: An effective hybrid energy harvesting method Publication Date : 2023.10.30. DOI : https://doi.org/10.1016/j.enconman.2023.117774

- First development of spintronic device consisting of two-dimensional ferromagnetic-ferroelectric material heterostructure, observation of low-power voltage-driven device operation - Developed next-generation spin memory technology to secure technological advantage in the domestic semiconductor industry As artificial intelligence technologies such as Chat-GPT are utilized in various industries, the role of high-performance semiconductor devices for processing large amounts of information is becoming increasingly important. Among them, spin memory is attracting attention as a next-generation electronics technology because it is suitable for processing large amounts of information with lower power than silicon semiconductors that are currently mass-produced. Utilizing recently discovered quantum materials in spin memory is expected to dramatically improve performance by improving signal ratio and reducing power, but to achieve this, it is necessary to develop technologies to control the properties of quantum materials through electrical methods such as current and voltage. Dr. Jun Woo Choi of the Center for Spintroncs Research at the Korea Institute of Science and Technology (KIST) and Professor Se-Young Park of the Department of Physics at Soongsil University (President Beom-Sik Jang) have announced the results of a collaborative study showing that ultra-low-power memory can be fabricated from quantum materials. By applying a voltage to a quantum material spintronic device consisting of two-dimensional material heterostructure, it is possible to read and write information at ultra-low power by effectively controlling the spin information of electrons. Two-dimensional materials, which are representative quantum materials, can be easily separated into planar layers of single atoms, unlike ordinary materials that have a three-dimensional structure, and thus exhibit special quantum mechanical properties. In this study, we developed a two-dimensional heterostructure device that combines quantum materials with two different properties for the first time. By applying voltage as low as 5 V to a device consisting of a two-dimensional ferromagnetic material (Fe3-xGeTe2) and a two-dimensional ferroelectric material (In2Se3) stacked on top of each other, the magnetic field required to change the spin direction of the ferromagnet, i.e., the coercivity, can be reduced by more than 70%. The researchers also found that the structural changes in the two-dimensional ferroelectric that occur when a voltage is applied lead to changes in the spin properties of neighboring two-dimensional ferromagnets. The lattice of the two-dimensional ferroelectric expands with voltage, changing the magnetic anisotropy of the adjacent ferromagnet and greatly reducing the coercivity required to reorient the spin. This means that by applying a very small voltage to a quantum material heterostructure device, it is possible to control the spin information of electrons even with an approximately 70% reduced magnetic field, which is a key technology for the development of ultra-low-power spin memory based on quantum materials. "By securing ultra-low-power next-generation memory core element technology using quantum materials, we will be able to maintain our technological edge and competitiveness in the recently faltering semiconductor industry," said Dr. Jun Woo Choi of KIST. [Fig 1] Schematics and optical image of the two-dimensional(2D) material heterostructure device (a) Device schematics of two-dimensional(2D) ferromagnet-ferroelectric heterostructure device. (b) Optical image of the fabricated device. [Fig 2] Operation of the two-dimensional(2D) ferromagnet-ferroelectric heterostructure device (a) Operation scheme of the heterostructure device. Voltage-induced lattice expansion modulates the magnetic properties of the ferromagnet. (b) Voltage-dependent measurement of the magnetic properties. (c) The coercivity as a function of applied voltage. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ KIST Institutional Program (2E32251, 2E32252), Mid-Career Research Support Project (NRF-2021R1A2C2011007), Leading Research Center Support Project (NRF- 2020R1A5A1016518), and Nanomaterial Technology Development Project (NRF-2021M3H4A1A03054856) from the Ministry of Science and ICT (Minister Lee Jong-ho), (NRF-2021R1C1C1009494), and the National Research Foundation for Young Researchers (NRF-2021R1A6A1A03043957), this research was published in the international journal 「Nature Communications」. Journal : Nature Communications Title : Voltage control of magnetism in Fe3-xGeTe2/In2Se3 van der Waals ferromagnetic/ferroelectric heterostructures Publication Date : 2023.09.12. DOI : https://doi.org/10.1038/s41467-023-41382-8

- Elderly man wears robot to climb Bukhansan Mountain in wearable robotics challenge - Wearable robots are leaving the hospital and entering our lives. As people age, they gradually lose muscle strength in their arms and legs, making it difficult for them to participate in leisure activities such as hiking and traveling, and they often need to rely on assistive devices such as canes and wheelchairs for mobility. However, these assistive devices do not improve muscle strength, so wearable robots that can compensate for the lack of muscle strength with the help of robots are attracting attention as an innovative technology to improve the health and quality of life of the elderly. Dr. Lee Jongwon of the Intelligent Robotics Research Center at the Korea Institute of Science and Technology(KIST) has developed a wearable robot, MOONWALK-Omni, which means 'to actively support leg strength in any direction(omnidirection) to help walk like walking on the moon', has announced that a senior citizen wearing it successfully completed a wearable robot challenge to climb to the top of Mount Yeongbong (604 meters above sea level) in Korea. The challenge raised the possibility of commercializing wearable robots in outdoor complex environments by successfully climbing with the help of the robot's muscle strength without changing batteries or intervention from developers. Various types of wearable robots have been developed in the past, but due to their heavy weight and large volume, they have been limited to the rehabilitation process of patients in hospitals with simple indoor environments. However, MOONWALK-Omni is an ultra-lightweight wearable strength-assistance robot that predicts the user's movements and supports insufficient leg strength to help the elderly rehabilitate and assist with daily activities. The 2-kilogram device can be easily donned by an older adult in less than 10 seconds without assistance, and its four ultra-lightweight, high-powered actuators on either side of the pelvis help balance the user while walking and boost the wearer's leg strength by up to 30 percent to increase propulsion. The robot's artificial intelligence (AI) analyzes the wearer's gait in real time and provides safe and effective muscle support in a variety of walking environments, including gentle slopes, rough rocky paths, steep wooden stairs, and uneven stone steps. Through the Bukhansan Mountain Wearable Robot Challenge, the research team succeeded in verifying the performance and reliability of muscle support using wearable robots in everyday environments that are more complex than hospitals. An elderly participant in the challenge said, "I thought I would have to give up mountain climbing, which I have enjoyed since I was young, but I feel 10 to 20 years younger after climbing the mountain comfortably with the wearable robot," and shared his impressions of climbing the mountain with the wearable robot. Dr. Lee Jong-won of KIST said, "Through this challenge, we have obtained experimental data that shows that safe and effective strength support is possible in a variety of walking environments." "Through the convergence of ultra-lightweight, high-power wearable robot drive technology and personalized artificial intelligence strength support technology, it is expected to be widely used in the fields of daily assistance, rehabilitation, and exercise for the elderly who lack muscle strength due to aging." As a follow-up to MOONWALK-Omni, the research team is developing MOONWALK-Support, which not only strengthens leg muscles but also supports the complex joints of the lower extremities such as hip and knee. In addition, the team has achieved achievements in various fields by transferring core technologies and components such as motors, reducers, and computing circuits for wearable robots to company in Korea. [Figure 1] (Bukhansan Challenge)An elderly man walks up a complex stone staircase environment while wearing a robot during a wearable challenge in Korea. [Figure 2] (Bukhansan Challenge)A 65-year-old man successfully climbs to the top of Mount Yongbong in Bukhansan Mountain using a wearable robot and muscle support. [Figure 3] Image of the wearable robot MOONWALK-Omni ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://kist.re.kr/eng