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Pharmacy Prof. KIM, IN SU
Research team led by Professor In-Su Kim at School of Pharmacy, Sungkyunkwan University proposes signals for developing
A research team led by Professor In-Su Kim at the School of Pharmacy of Sungkyunkwan University (President: Dong-Ryeol Shin) has developed a synthetic methodology to selectively transform nucleoside analogs, known as the core structure of antiviral drugs. The findings were published in the September issue of the online edition of Angewandte Chemie (IF = 12.959), a world-renowned journal in the field of chemistry. A nucleoside analog is a compound that is designed with an aim to resemble a structural unit of DNA or RNA by modifying the sugar or base which are the basic units of DNA and RNA. Nucleoside analogs because of their inherent characteristics could be absorbed into viral cells and control genomic synthesis and so could be used as an antiviral drug. So far, more than 20 nucleoside analogs have been used to treat various viral infections such as Herpes (HSV), AIDS (HIV), and hepatitis B/C (HBV/HCV). In particular, Remdesivir, which is in the spotlight as new COVID-19 treatment, is also known to contain a nucleoside analog. In this study, Professor In-Su Kim's research team developed the first synthetic method for selective alkylation of a nucleobase in nucleoside analogue by utilizing easily available sulfur ylide. Previously reported alkylation methods of nucleobase require organic solvents and complex processes involving multiple steps with low chemical reactivity, in turn, resulting in additional production costs and limitations for application in the pharmaceutical industry. Sulfur ylide is a reagent developed in 1960 by Nobel Prize-winning professor E. J. Corey, which has been used only in the manufacture of trigonal cyclic compounds. Professor In-Su Kim's research team has created an opportunity to showcase the importance of sulfur ylide as an effective reagent to alkylate nucleoside analogs. In this developed synthetic method water or alcohol is used as a reaction solvent that is considered as environmentally green and also largely reduce the production cost. Professor In-Su Kim said, "The results are new discovery of the reactivity of sulfur ylides for direct functionalization of carbon-hydrogen bonds. In particular, this study has presented a new signal to aid the development of antiviral drugs for human suffering from the new viral infection, and can drastically improve the manufacturing method for nucleoside alkylation compared to the existing multi-stage synthetic process." This research was conducted with financial support from the National Research Foundation of Korea and the Ministry of Science and ICT (MSIT). < Picture Description > Graphic above the green line: A reaction scheme indicating the reaction of nucleoside with sulfur ylide and carbon-hydrogen bond in nucleoside analog to be replaced with an alkyl. Graphic below green: The reaction of Pyrazinones and Azaracils with sulfur ylide in water or alcohol as solvent does not result in the known cyclic trigonal compounds, but rather brings about alkylation of C˗H bond. Reaction mechanism by path a is suggested by Nobel Prize-winner Professor Corey, and reaction mechanism by path b is the result of the current research. External environmental factors such as substrates, reagents, solvent and temperature are very important to control the reaction pathways a and b. The description in front of the four bullet points summarizes the originality and excellence of the current research work. < Term Description > Nucleoside analogues: organic compounds that transforms the phosphoric acid, sugar, and base of DNA and RNA to make it structurally similar to DNA or RNA. Nucleobase: nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids. The five nucleobases of adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) are called primary or canonical. Sulfur ylides: organic compounds containing negatively charged atoms (carbon anions) within molecules, and negatively charged carbon elements are directly coupled with heterocarbons (sulfur, phosphorus, or nitrogen) that have positive transmission. Alkylation: organic synthesis that introduces alkyl groups through substitution or addition reactions to organic compounds.
- No. 147
- 2020-11-25
- 113
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Education Prof. LEE, DONGHUN
Trauma, Disaster Psychological Support, and The Influence of Coronavirus Disease 19(COVID-19) Pademic on Public's Psych
There is always a danger of potential disaster in our lives. Natural disasters such as earthquakes, typhoons, and tsunami, as well as social disasters increasing as human civilization develops, are threatening our lives. Recently, we even have experienced a virus pandemic that we never imagined before. These disasters can cause material and economic damage such as loss of life, property, and job, as well as social and psychological dysfunction for the disaster victims by remaining as threatening events that shake up one’s life. Since the research team led by Professor Dong Hun Lee of the Department of Education had conducted the R&D of the Ministry of Security and Public Administration from 2014 to 2016, the team has continuously made efforts to study the psychological and social effects of large-scale disasters on people and to establish national-level psychological support measures. [1] ‘OMEGA - Journal of Death and Dying‘(SSCI), August 9, 2020 “A Longitudinal Perspective on Bereaved Parent’s Changes in Life Experience” (Yewon Kim, DongHun Lee, HongJin Jeon) • Individuals who experienced traumatic events may experience extreme psychological pain and fear, with losing their prediction and control of their own lives, especially a feeling of changes in themselves. • According to the study, parents who lost their child to disasters not only experience more powerful and continuous grief and mental health difficulties than other kinds of loss experiences, but also may not recover from the negative effects of grief for a long time. The study suggests that psychological supports for victims of disasters need to be continued to the years beyond the early stages of the incidents. [2] The Influence of Public's Fear, and Psycho-social Experiences during Coronavirus Disease 19(COVID-19) Pandemic on Depression, Anxiety in South Korea, The Korean Journal of Counseling and Psychotherapy 2020, 32(4), In Press, (Lee, DongHun, Kim, YeJin, Lee, DeokHee, Hwang HeeHun, Nam, Seulji, Kim, Ji Yun) • The research team led by Prof. Lee, who published a paper titled <‘The Emotional Distress and Fear of Contagion Related to Middle East Respiratory Syndrome(MERS) on General Public in Korea’ (Dong Hun Lee, Ji-Yun Kim, Hyun-Suk Kang)> (in Korean Journal of Psychology: General in 2016), tried to examine the psychological and social effects of infectious social disasters such as coronavirus on the general public and find out the various causes of new infectious diseases affecting the public's negative psychological experiences. • In this study, infectious diseases such as MERS, SARS, and Influenza A (H1N1) have continuously occurred in South Korea, but it is revealed that "technical disease control" and "emotional guard" should be combined to reduce fear, anxiety and depression of the general public. In addition, since it is impossible to prevent the influx of new infectious diseases and these diseases can occur again at any time, it is important to establish a national-level psychological support plan to cope with future infectious social disasters. ※ Reference - Study on COVID-19 1. Donga https://www.donga.com/news/It/article/all/20200908/102839839/1 2. Yonhapnewstv https://www.yonhapnewstv.co.kr/news/MYH20200906003600038 https://www.yna.co.kr/view/AKR20200905044100004 3. Maeil Business Newspaper https://www.mk.co.kr/news/society/view/2020/09/918328/ - Study on MERS 1. https://news.joins.com/article/23720342 [Original Article: JoongAng Daily] suffering from panic due to stress of coronavirus ... ‘mental prevention’ desperately needed in Daegu 2. http://biz.heraldcorp.com/view.php?ud=20160714000138 The Korea Herald
- No. 146
- 2020-11-17
- 258
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Biomedical Engineering Prof. PARK, CHUN GWON
Prof. Chun Gwon Park (GBME) develops treatment for severe coronavirus infection-19 and sepsis using nanotechnology
A research team led by Prof. Chun Gwon Park (Department of Biomedical Engineering at Sungkyunkwan University), together with the research teams of Dr. Wonhwa Lee (Korea Research Institute of Biomedical Engineering), Prof. Jun hong Ahn (Yeongnam University Hospital), Prof. Hee ho Park (Kangwon University), and Prof. Woo ram Park (Catholic University) discovered a biomarker that can determine the severity of COVID19 and sepsis patient, and developed a nanomaterial-based general-purpose therapeutic candidate using the found biomarker. In 2020, the global COVID19 epidemic including Korea has caused more than 32 million infections and over 1 million deaths to date. Corona 19 infection causes an over-inflammatory reaction, leading to local and systemic tissue damage, as well as complications such as severe progressive pneumonia, acute respiratory syndrome and sepsis in mild respiratory diseases. Currently, there is no vaccine or clear treatment against the coronavirus, and there is no biomarker to predict patients who are seriously deteriorating or dying by severe diseases. Prof. Park and his colleagues found that NETosis - a process in which cells are killed due to an over-inflammatory reaction caused by abnormally activated neutrophils and causes several complications such as sepsis - related factors in the blood of patients with severe coronavirus was expressed significantly higher than those of normal and mild COVID-19 patients. It was confirmed that the concentration of DNase-I in the body that can inhibit NETosis was very low. Prof. Park’s research team focused on the excellent biocompatibility and adhesion properties of 'melanin', the main component of squid ink, and produced nanoparticles that can circulate in the blood for a long time. The biomolecule DNase-I that degraded DNA, the main component of NETosis, was coated on the surface of melanin nanoparticles to inhibit NETosis and to produce biocompatible melanin nanoparticles coated with DNase-I, which can exert therapeutic effects for a long time. Prof. Park’s research team confirmed that DNase-I-coated biocompatible melanin nanoparticles maintained their drug efficacy for a long time in the blood. Administration of DNase-I-coated biocompatible melanin nanoparticles in blood samples of severe coronavirus patients and sepsis animal models showed a meaningful difference compared to the administration of DNase-I alone, and it was confirmed that by suppressing NETosis, the hyperinflammatory response was lowered to alleviate systemic inflammation and lower mortality. Through this, the biocompatible melanin nanoparticles coated with DNase-I can help prevent the progression of acute respiratory syndrome, pneumonia, and sepsis by inhibiting NETosis in severe coronavirus patients, and can have a great effect on coronavirus treatment. Prof. Park’s research team revealed that it is a future plan to develop and apply the developed DNase-I-coated biocompatible melanin nano-therapeutic drug into a new nanoparticle-based drug that can potentially treat the symptoms of coronavirus infection. Published article: Park, H. H., Park, W., Lee, Y. Y., Kim, H., Seo, H. S., Choi, D. W., Kwon, H.-K., Na, D. H., Kim, T.-H., Choy, Y. B., Ahn, J. H.,* Lee, W.,* Park, C. G.*, Bioinspired DNase-I-coated melanin-like nanospheres for modulation of infection-associated NETosis dysregulation, Advanced Science, accepted, 2020 [Image] Diagram of bio-applied and melanin nanoparticles coated with DNase-I production
- No. 145
- 2020-11-05
- 247
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Medicine Prof. LEE, KYU SUNG ·Prof. Munjae Lee (Department of Medical Device Management and Research)
Established the Occurrence Causes of Unmet Medical Care in Patients with Benign Prostatic Hyperplasia
- Need to induce early treatment and prevention of benign prostatic hyperplasia centered on primary medical cares - Suggested that the unmet medical care could be resolved by using ICT-based medical devices and caring robots through the convergence research A paper on the unmet medical care in patients with benign prostatic hyperplasia was published online in the world-renowned academic journal, the "Journal of Clinical Medicine", on March 25 (Wed), which has been jointly studied by Professor Lee Munjae’s research team in the Department of Medical Device Management and Research, SAIHST (Samsung Advanced Institute for Health Sciences & Technology); Professor Lee Kyu-Sung’s research team in the Department of Urology, Samsung Seoul Hospital; and Professor Choi Mankyu's research team at Korea University. Even though not a life-threatening disease, benign prostatic hyperplasia is one of the diseases that may lower the quality of life by bringing about discomfort in daily life due to symptoms, such as urination disorder, etc. In terms of benign prostatic hyperplasia, one of the geriatric diseases, its prevalence has been increasing due to the recently increased patients with metabolic syndrome, such as obesity, diabetes, and hypertension. However, considering this as a process of aging or as a temporary symptom, the unmet medical experience of the patients with benign prostatic hyperplasia tends to increase now because they cannot receive medical services in time. The research team used Andersen's Behavioral Model to analyze the factors of the unmet medical care of patients with benign prostatic hyperplasia. The Andersen's Behavioral Model has been also used in the unmet medical research as it can analyze the predictive factors in using medical services and measure factors influencing medical use. The Andersen's Behavioral Model is categorizing the factors related to the use of medical care services into predisposing factors, possible factors, and necessary factors. Although multiple studies have been conducted on the unmet medical care, there has been no research to establish the fundamental causes inducing the unmet medical care in patients with benign prostatic hyperplasia. Accordingly, the research team investigated and revealed the causes of unmet medical care in patients with benign prostatic hyperplasia, then conducting a study on the measures to effectively manage the patient. According to research findings, in the Andersen's Behavioral Model, age and education level influenced the unmet medical care in predisposing factors, and the medical security type affected it in possible factors. In addition, as for necessary factors, it was found that the sick-in-bed experience had an impact on the unmet medical care of patients with benign prostatic hyperplasia. In other words, it could be seen that relatively younger patients had more unmet medical care experience and patients with the higher the educational level had less unmet medical care experience. Furthermore, for the patients who had benefits from the health insurance, the experience of unmet medical care decreased; the patients lying in bed had more unmet medical care experience. Based on these findings, in order to reduce the unmet medical care experience of patients with benign prostatic hyperplasia, the research team identified that it is necessary to lead the patients to be treated in early stages when symptoms are detected, by providing accurate information about the disease in advance. In addition, they stressed that efforts in the policy to emphasize the importance of prevention and early diagnosis are needed for the disease, like benign prostatic hyperplasia, related to which there are many cases that patients themselves may ignore their own health problems. Particularly, the research team tried to resolve the unmet medical care from a new perspective – through the convergence research of clinic, health sciences, etc. Research Professor Lee Munjae, the lead author of this paper, remarked, “For education on prevention and early diagnosis, the use of primary care is necessary, and it is expected that continuous management of diseases will be conducted through a community care project centered on the primary medical care”, and then stated “Especially in the case of patients with benign prostatic hyperplasia giving a restriction on their physical activity, if medical care services would be provided by utilizing ICT-based medical devices, caring robots, and so on, the unmet medical care could be resolved.” This work was supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea (NRF-2019S1A5A2A03040304). ※ Paper title: Unmet Medical Needs of Patients with Benign Prostate Enlargement ※ Paper source: https://www.mdpi.com/673294
- No. 144
- 2020-10-08
- 377
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Electronic and Electrical Engineering Prof. SON, DONG HEE
Development of a Sticker-like Stretchable Artificial Neural Electronic Epineurium for Peripheral Neuroprosthetics
Conventional Cuff-type peripheral nerve interfacing devices have been applied to neuroprosthetic systems to measure neural signals and deliver the programmed electric pulses to the nerves. However, when implanted to the nerve chronically, mechanical mismatch between neural device and tissue induces the formation of an abnormal amount of fibrous tissue on the peripheral nerve, resulting in nerve compression. The long-term compression leads to lethal nerve necrosis. Micro-neurosurgery is also the time-consuming task. These issues remain challenging. To overcome the limitation, Prof. Donghee Son played a major role in leading SKKU-KIST research team gave an idea for realizing mechanically adaptive peripheral neural interfaces using intrinsically stretchable and autonomously self-healing materials. In continuing effort to optimize their individual performances, SKKU-KIST research team developed “Adaptive Self-healing Electronic Epineurium” as a promising candidate for clinic-grade chronic neural interfaces (Figure 1). SKKU-KIST research team addressed that the self-healing property of electronic epineurium allows surgeons to implant the neural interfaces efficiently while reducing operation time even without causing sequela (Figure 2). Additionally, dynamic stress relaxation of electronic epineurium prevents nerve compression chronically, resulting in reliable neural recording and stimulation. After implanting electronic epineurium into sciatic nerve of a rat, SKKU-KIST research team successfully recorded sensory neural signals for 14 weeks while applying mechanical stimuli to rat’s sole. In addition to monitoring of neural signals, electrical stimulation was reliably delivered to rat’s sciatic nerve without causing nerve fatigue. Using electronic epineurium, the team demonstrated a nerve-to-nerve interface to bypass the damaged spinal cord. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1C1C1005567). This work was also supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) (No.S-2020-1443-000, Development of low power/low delay/self-power suppliable RF simultaneous information and power transfer system and stretchable electronic epineurium for wireless nerve bypass implementation). This research was also supported by KIST intramural grants (2E30341, 2E29680, 2E29300). This research was also supported by the National Research Council of Science & Technology grant by the Korea government (MSIT) (No. CAP-18-01-KIST). This research is published on world-renowned International journal, Nature Communications, on August 21, 2020. * Title: Adaptive self-healing electronic epineurium for chronic bidirectional neural interfaces Professor Son Dong-hee explained the significance of the research, saying, "This research result has developed a new paradigm that can overcome the limitations of the existing neuroprosthetics field, and has opened the possibility of implementing smart electronic medicine for the rehabilitation of the human nervous system. It is also expected to be the foundation of robot or artificial neural networking technology for prothetic in the future.” Figure 1 Electronic epineurium implanted to sciatic nerve of a rat Figure 2 Mechanical adaptability of self-healing electronic epineurium Figure 3 Long-term neural recording and stimulation
- No. 143
- 2020-09-17
- 731
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Pharmacy Prof. SHIN, JU-YOUNG ·Researcher Han Eol Jeong, Researcher Hyesung Lee
Use of Nonsteroidal Anti-inflammatory Drug Worsens Clinical Outcomes for the COVID-19 Patients
The research team led by professor Ju-Young Shin, together with researchers Han Eol Jeong and Hyesung Lee, from the School of Pharmacy, Sungkyunkwan University, South Korea found that use of nonsteroidal anti-inflammatory drugs (NSAIDs) resulted in worsened clinical outcomes among adults hospitalized with coronavirus 2019 (COVID-19) by using South Korea’s nationwide healthcare data. These results were concluded by including 18 kinds of NSAIDs which is widely used in South Korea, for example ibuprofen. COVID-19, which was first identified in late 2019, is an ongoing pandemic and respiratory disease that is caused by the infection from the Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2). As of August 25, 2020, there are a total of 214 countries affected worldwide, with more than 24 million confirmed cases and 82 thousand deaths. With the main symptoms of COVID-19 being high fever, cough, shortness of breath, NSAIDs are widely used to in these patients to manage their symptoms of fever and muscle pain. In March, 2020, the French Health Minister raised concerns regarding the potential harms NSAIDs may have when used in patients with COVID-19. This was based on case reports of four COVID-19 patients who developed worsened clinical outcomes following NSAIDs use. In addition, findings from previous studies reported lower incidence of adverse outcomes associated with acetaminophen than NSAIDs. Thus, the French Health Minister recommended acetaminophen be used as first-line agents to alleviate fever symptoms, which was also supported by the World Health Organization (WHO). These claims were based on one animal study, which increased angiotensin-converting enzyme 2 (ACE2) expressions with NSAIDs in various organs, where, ACE2 upregulation induced by NSAIDs could theoretically heighten the infectivity of SARS-CoV-2 to worsen clinical outcomes. Other mechanisms have also been suggested of which, NSAIDs could aggravate infections by upregulating COX-2 in activated B lymphocytes to interfere with antibody productions, or by selectively inhibiting interferon-γ productions that are vital for immunity against foreign pathogens. However, with no conclusive clinical evidence on this topic available, regulatory bodies such as the United States (US) Food and Drug Administration and the European Medicines Agency have released statements that there is insufficient evidence to draw conclusions regarding this safety concern and the WHO revised their initial statement accordingly. For such reasons, current clinical practice should not be changed until further evidence becomes available. Despite the widespread use of NSAIDs, to our knowledge, there is currently no published observational study that specifically assessed the association between NSAIDs use and clinical outcomes among COVID-19 patients. To investigate such concerns, professor Ju-Young Shin assembled an international collaborative research team comprised of a world renown clinical researcher from Harvard University, US, and an esteemed pharmacoepidemiologist from McGill University, Canada, and used the Health Insurance Review and Assessment Service (HIRA) database of South Korea, provided as part of the #OpenData4Covid19 project on March 27, 2020, by the Ministry of Health and Welfare and HIRA. Briefly, this data provided through this platform is real-world data (RWD) of all COVID19 patients in South Korea that contains healthcare utilization information based on a fee-for-service reimbursement system. Study participants were adults (aged ≥19 years) hospitalized with COVID-19 as of April 8, 2020. Based on the history of NSAIDs use in the 7 days before and including the date of hospitalization, patients were classified as either NSAIDs users or nonusers. Moreover, we balanced any differences in sociodemographic or clinical characteristics between NSAIDs users and nonusers by applying the propensity score as weights, which was estimated based on age, sex, health insurance type, history of comorbidities and use of co-medications, to evaluate the risk of adverse clinical outcomes. This study found that there were 1,824 adults hospitalized with COVID-19, of which, there were 354 NSAIDs users and 1,470 nonusers. NSAIDs users, as compared with nonusers, had a 54% increased risk of in-hospital death, intensive care unit admission, mechanical ventilation use, or sepsis. In addition, the study findings suggest the possibility of an elevated risk of cardiovascular complications, comprised of heart failure, myocardial infarction, and stroke, and acute renal failure associated with NSAIDs users. Professor Ju-Young Shin, corresponding author of the study, stated that, “I am excited that our study findings could serve as important scientific and real-world evidence to help clinicians in the decision to use NSAIDs for the treatment of fever or pain among patients with COVID-19 as the harms associated with their use may outweigh their benefits”. Moreover, researchers Han Eol Jeong and Hyesung Lee, joint co-authors of the study, noted that, “We are highly pleased by being able to provide meaningful real-world evidence to clinicians during such difficult times due to the COVID-19 pandemic, and further inform the world of the greatness of South Korea’s healthcare data”. This research was published in Clinical Infectious Diseases (IF=8.313, JCR Ranking 3.2%), a leading journal in the field of infectious disease with a broad international readership, on Monday, July 27, 2020. ※ Research Title: Association Between Nonsteroidal Anti-inflammatory Drug Use and Adverse Clinical Outcomes Among Adults Hospitalized With Coronavirus 2019 in South Korea: A Nationwide Study ※ Research Web Site: https://academic.oup.com/cid/article/doi/10.1093/cid/ciaa1056/5876905?searchresult=1 ※ Relevant News Articles: Yonhapnews: https://www.yna.co.kr/view/AKR20200805147700017 ChosunMedia: https://biz.chosun.com/site/data/html_dir/2020/08/06/2020080601112.html Korea Economic Daily: https://www.hankyung.com/it/article/202008067897Y
- No. 142
- 2020-09-02
- 768
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Center for Integrated Nanostructure Physics Prof. LEE, YOUNGHEE ·Researcher Van Luan Nguyen, Researcher Dinh Loc Duong, Researcher Sang Hyub Lee
How to Stack Graphene up to Four Layers
Graphene, an atomically thin hexagonal structure of carbon atoms is a potential candidate for electronic and optoelectrical applications such as transparent electrodes and interconnect for integrated circuits. Yet, it is one thing to possess such useful properties and to induce an intended characteristic from this “wonder material” is another. In the face of the end of the “Moore’s Law”, chip makers have set their sight on multi-layered graphene for its scaling ability of integrated circuits to smaller physical dimensions and the electric-field induced bandgap, which is not affordable in monolayer graphene. Furthermore, owning to exotic physical properties controlled by its stacking orders (the arrangement of graphene layer along vertical direction) such as superconductivity and quantum Hall effect to name a few, multilayer graphene is an interesting material for condensed matter physicists. for its extreme conductivity and stability. Still, the unknown growth method for uniform single-crystalline multilayer graphene growth in a wafer scale presents a challenge. Led by professor LEE Young Hee at the Center for Integrated Nanostructure Physics, the Institute for Basic Science (IBS) in Sungkyunkwan University, South Korea, an IBS research team reports a novel method to grow multi-layered, single-crystalline graphene with a selected stacking order in a wafer scale. Moreover, the research team could arrange a full multilayer graphene film along the right vertical direction without no sticking points, meaning that they can feature ***** . They obtained four-layered graphene using chemical vapor deposition (CVD) via Cu-Si alloy formation. There have been several approaches to control the number of graphene layers. Conventionally, the monolayer graphene, which is easily grown on Cu-substrate, can be detached from the Cu-substrate and transferred onto insulator substrates such as SiO2/Si. Therefore, the simplest method to make multilayer graphene is to stack them layer-by-layer via the transfer process. However, this transfer process may cause tearing, wrinkles, and/or polymer residues. Though such issues can be avoided via a direct method, i.e. CVD on Cu substrate, the low solubility of carbon (C) in copper (Cu) hampers the controlling of the number of graphene layers with high uniformity in a large area. By depositing Ni or Co to form Cu-Ni/ Cu-Co alloys or employing oxygen-rich Cu substrate, C solubility in Cu is boosted and thus stacks more layers of graphene. Nevertheless, a small portion of inhomogeneous multilayers occurs. Controlling the crystallographic stacking sequence of graphene films thicker than two layers with high uniformity has not been demonstrated to date. Figure 1. Schematic of growth process. Step I: Si atoms were uniformly distributed in the monocrystalline Cu(111) film; step II: SiC formation at 900 ℃ in a H2-rich environment; step III: multilayer graphene islands were grown at 1075 ℃; step IV: a full multilayer graphene film was obtained. Dr. Van Luan Nguyen, the first author of the study (now at Samsung Advanced Institute Technology) proposed to use silicon carbide (SiC) on the surface of Cu substrate alloy, via the sublimation of Si atoms at a high temperature. They controlled the C solubility in the Cu film by introducing Si content on Cu surface by heat treatment of Cu substrate with a constant H2 gas flow inside the quartz tube of CVD chamber. “The formation of a homogeneous Cu-Si alloy, as a role of catalyst, was critical to control the number layers of graphene film in a wafer scale with methane gas. With the presence of Cu-Si alloy, SiC can be formed when methane gas is injected and the following sublimation process of Si atoms leaves C atoms behind to form multilayer graphene. Si amount is fixed at 28.7 % for uniform multilayer graphene film. Depending the concentrations of argon (Ar)-diluted methane gas, the number of graphene layers varies,” says Dr. Van. Figure 2. Optical micrographs of mono-, bi-, tri-, and tetralayer graphene on the SiO2/Si substrate. The insets of show cross-sectional TEM images of the corresponding graphene films. Figure 3. Photograph of centimeter-scale mono-, bi-, tri-, and tetralayer graphene on the SiO2/Si substrate. “Growing in a large scale of this much-hyped graphene has seen much progress over a decade, but building multi-layered graphene is just in its early stages. Our study offers a novel approach to upgrade the conventional CVD method by introducing an intermediate process of in-situ formation of SiC film,” notes Dr. LEE Sang Hyub, coauthor of the study. Importantly, this study provides a new platform to synthesize graphene multilayer towards the uniform large-area single-crystalline layer-tunable multilayer graphene as well as graphite thin film. This is an initial step to incorporate multilayer graphene to display panels and integrated circuits such as via-holes and replacement of Cu electrodes as well as photo-electronic and photovoltaic devices. “Deposition of Si by conventional methods at low temperatures such as thermal evaporation or sputtering does not work for uniform multilayer graphene growth. The key in our new approach is to form uniform Cu-Si alloy on quartz tube chamber in which Si is sublimated at high temperature of 900 ℃ with H2 gas flow in a controllable manner,” explains Director LEE Young Hee, the corresponding author of the study. Although the substantial achievement has been demonstrated in our current work, Director Lee cautions that the method to deposit Si at high temperature during the growth process is not practical and can be harmful for the quart tube for long-term use. They are searching for a solution to replace the current one for mass product.
- No. 141
- 2020-08-18
- 1444
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Semiconductor Systems Engineering Prof. CHOI, JAE HYUK ·Prof. Jung-Hoon Chun·Researcher Hyeong-Seok Seo
Development of the nation’s first CMOS LiDAR Sensor System-on-Chip
Prof. JaeHyuk Choi and Prof. Jung-Hoon Chun in the Department of Semiconductor Systems Engineering at SKKU have successfully developed the nation’s first CMOS Light Detection and Ranging (LiDAR) sensor for autonomous vehicles. The research paper was presented at the VLSI symposia, the top-tier conference on semiconductor circuits and technologies. Founded in 1981, VLSI symposia has a 40-year history this year and is one of the most prestigious conferences. It is also well known for selecting papers through a rigorous review process and for leading companies such as Intel and Samsung to present the latest technology competitively. A LiDAR sensor measuring a distance of objects as well as 2-dimensional shape is an essential component for object/environment detection and recognition in autonomous vehicles, robots, and drones. Even though several LiDAR sensors were already commercialized, these products have the large form factor and high price owing to the assembly of many discrete IC components. The SKKU’s LiDAR sensor that is a single semiconductor chip with 6 x 5 mm2 size offers mass production with low-cost semiconductor (CMOS) technology. Several CMOS LiDAR sensors were already presented by overseas companies and research institutes such as Toshiba, Toyota, and EPFL. SKKU developed the first CMOS LiDAR sensor in Korea. More importantly, SKKU addressed two critical problems of inter-LiDAR interference between multiple vehicles and performance degradation according to weather conditions. SKKU newly developed an interference filter and a multi-event histogramming time-to-digital converter to provide reliable detection up to 48m range in real road applications where many vehicles run simultaneously. In collaboration with domestic companies, SOS Lab and Samsung Electronics, our research team successfully developed prototype sensor chips and outperformed existing LiDAR sensors. SKKU presented the paper at the VLSI symposia's Image Sensor and Imaging Techniques session in June 2020. A total of 5 papers presented in the session are mainly published by the world's top companies such as Samsung and Toshiba. Additionally, SKKU is the only domestic university that presented one of the five papers. ※Paper: “A 36-channel SPAD-integrated scanning LiDAR sensor with multi-event histogramming TDC and embedded interference filter”, Symposia on VLSI Circuits, 2020. ※Authors: Hyeongseok Seo (1st author, dept. of electrical and computer engineering, SKKU), Jaehyuk Choi (corresponding author, dept. of semiconductor systems engineering, SKKU), Jung-Hoon Chun (co-author, dept. of semiconductor systems engineering, SKKU), Heesun Yoon·Dongkyu Kim (co-authors, SOS Lab), Jungwoo Kim (co-authors, Samsung Electronics), Seong-Jin Kim (co-authors, dept. of electrical and computer engineering, UNIST)
- No. 140
- 2020-08-05
- 1118
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Energy Science Prof. OH, SANG HO ·PhD. LEE, SU BIN
Nanoindentation processes in full view via in-situ TEM reveal the dislocation nucleation mechanism
The microelectronics revolution is one of the most influential drivers of current industrial developments. To probe the mechanical properties of ever shrinking materials and components, nanoindentation has come to be an omnipresent and indispensable method. In a recent combined experimental and computational approach, Prof. Sang Ho Oh was able to resolve the dynamic atomistic processes taking place at the elastic-plastic transition during nanoindentation for the first time. Further, Prof. Oh could determine the rate limiting processes governing the so-called pop-in event, as well as the origins for the observed transitions in dislocation mechanisms succeeding this event based on the dynamics of so-called prismatic dislocation loops. In the future, these fundamental insights will enable modifications of established nanoindentation models in order to better describe the most common small scale mechanical characterization technique. The research result was published on May 12 in Nature Communications (IF 11.880), an international science journal. Full details can be found in this open access article: In-situ observation of the initiation of plasticity by nucleation of prismatic dislocation loops S. Lee et al, Nature Communications, published 05/12/2020 https://doi.org/10.1038/s41467-020-15775-y [Fig. 1] Formation of shear loops during plastic deformation. From the real-time transmission electron microscopy nanoindentation transformation experiment of gold nanowires, the experimental results and atomic simulation results of observing the formation process of dislocation loops during the initial plastic deformation process
- No. 139
- 2020-07-20
- 973
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Energy Science Prof. YOON, WON SUB ·Researcher Eunkang Lee
Provides a new way to develop cathode materials for longer and safer vehicle batteries
Prof. Won-Sub Yoon’s research team successfully derives the key factors on the thermal instability of Ni-rich cathode material for lithium-ion batteries. This research work was published in the Advanced Science (IF: 15.804) on April 24 as a back cover, with the title "Tracking the Influence of Thermal Expansion and Oxygen Vacancies on the Thermal Stability of Ni‐Rich Layered Cathode Materials." The extensive demand for high energy storage in electric devices, electric vehicles and smart grid systems has led to the commercialization of rechargeable lithium ion batteries using Ni-rich layered cathode material. Simultaneously, the safety issue from the thermal instability of Ni-rich cathode materials has been introduced. Until now, the strategy to enhance its thermal stability has been approached based on fragmentary facts that the thermal instability is merely attributed to the thermally unstable Ni element. However, these approaches have limitations in providing a custom solution to the fundamental cause of thermal instability involving Ni element. Prof. Won-Sub Yoon's research team showed that the thermal expansion of Li slab become larger as the increase of Ni content in the cathode material before the onset temperature of layered to disordered spinel phase transition is reached. This thermal expansion of Li slab induces the elongation of intermediate tetrahedron in pathway of cation migration, resulting in an expanded pathway with a low energy barrier for cation migration. In addition, the oxygen vacancies are formed and accumulate around only Ni ions before the onset temperature of phase transition is reached. In presence of oxygen vacancies, the cation migration pathway is energetically mitigated as Ni ion migrates through the face-shared oxygen plane that does not contain oxygen vacancies. Herein, the team proposed the thermal expansion and oxygen vacancies as new critical factors to affect thermal stability of charged Ni-rich cathode materials as shown in the figure below. [Figure 1] Occurrence of thermal expansion and oxygen vacancies in Ni-rich layered cathode materials due to increase of temperature and the process of change in the crystal structure and phase transition ※ Title: Tracking the Influence of Thermal Expansion and Oxygen Vacancies on the Thermal Stability of Ni‐Rich Layered Cathode Materials ※ Original Article URL: https://onlinelibrary.wiley.com/doi/full/10.1002/advs.201902413
- No. 138
- 2020-07-06
- 1540
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Mechanical Engineering Prof. KIM, JAEHOON ·Researcher Handi Setiadi Cahyadi
Revealing the Intercalation Mechanisms of Lithium, Sodium, and Potassium in Hard Carbon
Revealing the Intercalation Mechanisms of Lithium, Sodium, and Potassium in Hard Carbon Due to its high stability, widespread availability, low-cost, and excellent performance, hard carbon is considered as one of the most promising anode materials for sodium and potassium-ion batteries. To further develop a high-performance electrode, it requires a deep understanding of the carrier-ion storage mechanism. However, this has proven to be not such a trivial task because of the complex structure of hard carbon. Recent work by Prof. Kim and his team unveil that the sloping voltage region is caused by the adsorption of Li-ion, Na-ion, and K-ion on the surface of active sites such as defects, edges, and residual heteroatoms. Afterward, the carrier-ions penetrate into the graphitic layers, creating a low voltage plateau region. This finding also further proven by DFT simulation, which revealed the change in the inner molecular structure of the hard carbon during the discharge process. The “ripening” phenomenon, in which the edge of the hard carbon structure open up when the carrier ion approach to the edge of graphitic layer, is very prevalent for the Na-ion and K-ion because of their larger electronic radius. However, the same degree of ripening does not occur for the Li-ion, which leads to a smaller capacity as compared to the Na-ion and K-ion. This finding is a breakthrough that will help future researchers understand the ion-storage mechanism behind the hard carbon material. In addition, the underlying concept of “ripening” phenomenon can be used to develop a high-performance electrode material in the future. This research was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning (2017M1A2A2087635) and the Waste‐to‐Energy Technology Development Program of the Korea Environmental Industry & Technology Institute with financial resources provided by the Ministry of Environment, Republic of Korea (No. 2018001580001). This research was published in 'Advanced Energy Material' on April 15. ※ Title : Intercalation Mechanisms: Revealing the Intercalation Mechanisms of Lithium, Sodium, and Potassium in Hard Carbon ※ Source : https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202000283 This diagram demonstrates the electron radius of ions and hard carbon's layer and its transposition when Li, Na, and K ions are inserted into hard carbon. The K- ions with the largest electron radius show the broadest edge expansion in which subsequent K- ions can penetrate deeper into the inter layer spacing of hard carbons.
- No. 137
- 2020-06-19
- 1540
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Mechanical Engineering Prof. BAIK, SEUNGHYUN ·Prof. Hyungpil Moon, and Prof. Moon Ki Kim
Develops Highly Conductive Healable Nanocomposite Materials
Prof. Seunghyun Baik, Prof. Hyungpil Moon, and Prof. Moon Ki Kim from SKKU’s School of Mechanical Engineering made a research report about the highly conductive completely reversible electron tunneling-assisted percolation network of silver nanosatellite particles for putty-like moldable and healable nanocomposites. Prof. Daewoo Suh (School of Mechanicl Engineering) and Prof. K. P. Faseela (Dept. of Energy Science) are co-first authors on the report. □ Deformable and healable conductive materials have received considerable attention due to their use in emerging future electronics, such as artificial human skin, internet of things, and bioelectronics, owing to their ability to recover from mechanical/electrical damage. However, their practical applications have been impeded by low electrical conductivity and irreversible conductivity degradation after breaking/healing cycles. □ The research team’s report is about the development of a highly conductive completely reversible electron tunneling-assisted percolation network of silver nanosatellite particles for putty-like moldable and healable nanocomposites. The densely and uniformly distributed silver nanosatellite particles with a bimodal size distribution are generated by the radical and reactive oxygen species-mediated vigorous etching and reduction reaction of silver flakes using tetrahydrofuran peroxide in a silicon rubber matrix. The close work function match between silicone and silver enables electron tunneling between nanosatellite particles, achieving high electrical conductivity and ~100% electrical healing efficiency. □ As an application demonstration, the highly conductive putty-like nanocomposites are employed as random-shaped electrical interconnectors, stably operating light-emitting diodes. An emergency electronics repair demonstration was also performed by a robot using the team’s nanocomposites. □ The research was published in Nature Communications. Daewoo Suh, K. P. Faseela, Wonjoon Kim, Chanyong Park, Jang Gyun Lim, Sungwon Seo, Moon Ki Kim, Hyungpil Moon, Seunghyun Baik, Electron tunneling of hierarchically structured silver nanosatellite particles for highly conductive healable nanocomposites, Nature Communications, 11, 2252 (May 2020), https://doi.org/10.1038/s41467-020-15709-8 Hierarchically structured silver nanosatellite particles for the highly conductive, moldable, healable, and stable nanocomposites.
- No. 136
- 2020-06-01
- 1423
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