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  • Resolving instability issues of perovskite solar cells and LEDs

    SKKU Advanced Institute of Nano Technology Prof. LEE, JIN WOOK

    Resolving instability issues of perovskite solar cells and LEDs

    Resolving instability issues of perovskite solar cells and LEDs Successful development of core technologies to impede ion migration pathways in perovskite solar cells and light-emitting diodes (LED) Prof. Jin-Wook Lee`s research team in the SKKU Advanced Nano Technology (SAINT) and Department of Nano Engineering have successfully developed core technologies to significantly improve the stability of perovskite solar cell and LED devices. The 3 research papers associated with it were published in Advanced Materials (impact factor=25.809), which is ranked within top 2% among the international SCI journals. Owing to the high efficiency comparable to silicon solar cells and organic LEDs, the perovskite solar cells and LEDs have been one of the strongest candidates for next-generation optoelectronic devices. However, operational stability of the devices was extremely poor compared to the commercialized devices. The high density of ionic defects in the low temperature solution processed perovskite thin films tends to easily migrate under built-in or applied electric field during the device operation, rupturing perovskite and adjacent charge transporting layers. This ion migration was a critical issue to improve the operational stability of the perovskite optoelectronic devices. Prof. Jin-Wook Lee`s research team developed core technologies to impede the ion migration pathways, resulting in significant improvement in operational stability of solar cell and LED devices. Using these techniques, the lifetime of the solar cell was improved more than 9-fold from 222 h to 2011 h (Advanced Materials, 2020, 1906995) while that of LED was improved more than 1000-fold from 12 min to over 200 h (Advanced Materials, 2020, 32, 1905674). Their technologies are expected to be a critical for commercialization of the perovskite optoelectronic properties by resolving the instability issue. Meanwhile, the research team also developed a new technology to improve the performance of perovskite quantum dot solar cells, which is regarded as a future technology to surpass the thermodynamic limit of the solar cell efficiency (Advanced Materials, 2019, 31, 1900111). ※ Related Journals 1) Steric Impediment of Ion Migration Contributes to Improved Operational Stability of Perovskite Solar Cells, Advanced Materials, 2020, 1906995. 2) Surface‐2D_Bulk‐3D Heterophased Perovskite Nanograins for Long‐Term‐Stable Light‐Emitting Diodes - Advanced Materials, 2020, 32, 1905674. - Wiley Online Library 3) A Small‐Molecule “Charge Driver” enables Perovskite Quantum Dot Solar Cells with Efficiency Approaching 13%, Advanced Materials, 2019, 31, 1900111.

  • Development of Time-of-Flight (ToF) 3D CMOS Image Sensor

    Semiconductor Systems Engineering Prof. CHOI, JAE HYUK ·전정훈 교수

    Development of Time-of-Flight (ToF) 3D CMOS Image Sensor

    Development of Time-of-Flight (ToF) 3D CMOS Image Sensor Prof. Jaehyuk Choi and Prof. Jung-Hoon Chun in the Department of Semiconductor Systems Engineering at SKKU have successfully developed a time-of-flight (ToF) 3D CMOS image sensor for mobile devices that generates 3-dimensional images of objects without motion artifact even under extreme illumination. The research paper was accepted to be published at the International Solid-State Circuits Conference (ISSCC), the top-tier conference on semiconductor circuits. Founded in 1954, ISSCC has a 66-year history this year and is the most prestigious conference called the Olympics in semiconductor circuitry. Each year, more than 3,000 scholars and engineers from 25 countries gather to showcase the world's best circuit technologies. 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. The 3D image sensor that detects not only the shape of the object but also the distance information can be used for robot navigation and security applications as well as mobile applications such as 3D face recognition, distance-based autofocusing when taking pictures, and 3D image synthesis for augmented reality. The ToF image sensor is a sensor that detects the distance of an object by irradiating infrared light with high-frequency modulation and detecting a phase change of reflected light from the object. The ToF image sensor overcomes the size limitations of the conventional structured-light 3D image sensor used in existing mobile devices, and is a miniaturized sensor semiconductor with a fine distance-accuracy of mm. ToF image sensors have recently started to be installed in mobile devices, but the Japanese company (SONY) has preoccupied the market. Besides, there are technical problems such as limitations of depth resolution and image resolution, distortion in detecting moving objects, and saturation due to extreme illumination in outdoor imaging. SKKU's research team developed a ToF image sensor SoC that integrates a high-speed photodiode device that improves depth resolution, an upscaling image processor that outputs 320 x 240 pixels of physical pixels at 640 x 480 (VGA) resolution, a dynamic modulation circuit that reduces motion artifacts, and an ambient-light cancelling circuit. In collaboration with UNIST and domestic Fabless company ZeeAnn, our research team successfully developed prototype sensor chips and outperformed existing ToF sensors. The paper will be presented at the ISSCC's Imagers and ToF Sensors session in February 2020. A total of 10 papers accepted in the session are mainly published by the world's top companies such as Samsung, Sony, Toshiba and Panasonic, and SKKU is the only domestic university. In addition to paper presentation, SKKU's research team will demonstrate the performance of the ToF image sensor directly in the demonstration session of the ISSCC conference. ※Paper: “A Dynamic Pseudo 4-Tap CMOS Time-of-Flight Image Sensor with Motion Artifact Suppression and Background Light Cancelling Over 120klux”, ISSCC, 2020. ※Authors: Donguk Kim (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), Canxing Piao Park·Yeonsoo Ahn·Kihwan Cho (co-authors, dept. of electrical and computer engineering, SKKU), Seunghyun Lee·Dahwan Park·Seong-Jin Kim (co-authors, dept. of electrical and computer engineering, UNIST), Jungsoon Shin·Seung-Min Song (co-authors, ZeeAnn)

  • All-day Mobile Healthcare Monitoring System Based on Heterogeneous Stretchable Sensors for Medical Emergencies

    Advanced Materials Science and Engineering Prof. KIM, SUNKOOK

    All-day Mobile Healthcare Monitoring System Based on Heterogeneous Stretchable Sensors for Medical Emergencies

    All-day Mobile Healthcare Monitoring System Based on Heterogeneous Stretchable Sensors for Medical Emergencies Wearable mobile healthcare devices are among the most rapidly developed modern electronic technologies due to advances in novel flexible processes, ultrathin devices and sensors, and flexible/stretchable materials. Korean researchers at Sungkyunkwan University (SKKU) have developed a fully integrated wearable smart patch based sensor system with nature-inspired, and strain-free deformable structures that has temperature and humidity sensors for long-term wearable and medical emergency devices. The study appeared in the journal IEEE Transaction on Industrial Electronics Reports in November, 2019. In recent years, there have been growing interests in epidermal and wearable electronic sensor technologies due to their ability to deliver real-time healthcare information to personalized smartphones. A team of researchers led by Prof. Sunkook Kim, who have been working on this for more than five years, addressed the challenge of continuous and long-term monitoring of biological signals in the human body by introducing a well-equipped breathable, bio-compatible, and conformable smart patch that can absorb moisture (sweat) generated from the skin without any irritation. This allows the users to continuously monitor their health as well as to detect and diagnose issues early. Inspired by nature, the researchers reported a novel structured device that is comprised of 3D-deformable and 2D stretchable platforms for wearable mobile point-of-care healthcare diagnostics that is conformably attached to a person’s skin. It includes a platinum (Pt)-resistance thermometer, humidity sensor, a signal processing IC, a wireless communication module, and a long-life battery. Furthermore, the wearable device has a fall-down detection feature that consists of a 3-axis accelerometer sensor that is mounted on the device. Prof. Kim said, “We have established a fully integrated wearable sensor system that can easily attach to the skin accurately detecting body information with an integrated circuit that includes a read-out circuit. This enables wireless communication and information transfer (temperature, humidity, and motion) to mobile phones assisting with emergencies and medical checkups for vulnerable patients.” He further added, “The proposed smart patch based healthcare device allows numerous new opportunities in the wearable electronics and biomedical fields as well as in internet of things (IoT) applications.” [Reference] Lee. S. et al., (2019) “All-day Mobile Healthcare Monitoring System Based on Heterogeneous Stretchable Sensors for Medical Emergency” IEEE-TIE Reports [Main Author] Sunghoo Lee (Korea Electronics Technology Institute), Srinivas Gandla (Sungkyunkwan University), Muhammad Naqi (Sungkyunkwan University), and Uihyun Jung (Sungkyunkwan University). **For inquires regarding this project, please contact Professor Sunkook Kim at seonkuk@skku.edu.

  • Successful Development of 3D muscle-mimetic cell-laden nanofiber via cell-electrospinning

    Bio-Mechatronic Engineering Prof. KIM, GEUNHYUNG

    Successful Development of 3D muscle-mimetic cell-laden nanofiber via cell-electrospinning

    Prof. Geun Hyung KIM and his research team reported that they have successfully aligned the nanofibrous structure by producing live myoblast cells and bioink suitable for electrospinning. Nano-muscular fibers implanted with live myoblast cells acted as if it were a real muscle tissue and accelerated the regeneration of muscle tissue by guiding the muscle cell to grow in a uniaxial direction. Tissue Regeneration Engineering is a field of study developed to improve the regeneration process of damaged tissues/organs by inserting a biological substitute, which is called scaffold. 3D cell-printing and electrospinning has been widely used for this process. However, the cells cultured by 3D cell-printing and electrospinning grew randomly, which was a serious problem for muscles that required its cells to be aligned for proper regeneration. To control cell morphology, they have developed electrospinning to a cell-electrospinning process. The research team used a biocompatible hydrogel to generate cell-laden nanofibers. Also, the hydrogel was added with a material with high processability to produce a bioink, which was applied with high-voltage direct current (Figure 1). After this, myoblast-laden nanofiber can be generated with an aligned pattern. -the myoblast-laden nanofibers showed over 90% of initial cell viability, which was a sign that it overcame the problem of low cell viability from the previous conventional cell-electrospinning process. Moreover, the cell alignment and differentiation improved threefold in comparison to the 3D cell-printing process (Figure 2). -the myoblast-laden nanofibers induced cells to grow in a uniaxial direction, which assists the regeneration of skeletal and cardiac muscle. Prof. KIM said, “This was the first case to successfully produce cell-laden nanofibers in uniaxial arrangement. It suggested a possibility to become a new method of regenerating aligned tissue structure.” This research was supported by a grant from the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology. It was featured in the world-renowned peer-reviewed scientific journal “Nano Letters” (impact factor 12.279) as well as “Biomaterials” (impact factor 10.273). Figure 1. Fabrication of regenerative muscle construct by controlling the alignment of nano-particles using flow induced shear force and electric field. Figure 2. Fabrication of regenerative muscle construct by providing the aligned dECM-Ma fibers using 3D cell printing process.

  • Invention of nano-wrinkle functional layer using the ESD method

    Mechanical Engineering Prof. LEE, WON YOUNG

    Invention of nano-wrinkle functional layer using the ESD method

    Prof. Wonyoung Lee and Prof. Doyoung Byun in the Department of Mechanical Engineering (First author: Jongseo Lee / co-first authors: Sangyeon Hwang, Minwoo Ahn) at SKKU announced the development of nano-wrinkle functional layer using the electrostatic spray deposition (ESD) method for the nanofiber electrode based solid oxide fuel cells. This research was published in Journal of Materials Chemistry A, one of the world's most prestigious journals in the energy field as a cover paper on August 2nd. This work is supported by the Technology Development Program to Solve Climate Changes (2017M1A2A2044927) and the Global Frontier R&D Program at the Center for Multiscale Energy System (Grant No. NRF-2014M3A6A7074784) and the Basic Science Research Program (NRF-2017R1E1A1A01075353) through the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning. Also, it is supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. 2019R1A2C4070158). A unique nano-wrinkled functional layer was fabricated by ESD between a porous nanofiber electrode and a dense electrolyte to extend and activate reaction sites at the interfaces for the high-performance intermediate-temperature solid oxide fuel cells. Upon the introduction of the nano-wrinkled functional layer, the polarization resistance was reduced 3.3-fold, while the peak power density was increased 2.2-fold at 650 ºC, compared to those of the reference sample. The substantial increases in surface area and grain boundary density in the nano-wrinkled functional layer reduce both polarization resistance and activation energy, providing a significant performance enhancement. Our results demonstrate the importance of interface engineering with a cost-effective and simple ESD process to fully utilize the nanostructured electrodes for high-performance IT-SOFCs. Prof. Wonyoung Lee said, “The structural mismatches existed at the interfaces between the nano-structured electrode and the dense electrolyte could be overcome with the nano-wrinkled functional layer.” He continued, “ESD method can greatly contribute to developing technologies at the commercialization stage because it can provide the large-area and high-speed fabrication processes for a number of nano-structures."

  • Bio-inspired Electronics for Enhancing Human Capability

    Chemical Engineering Prof. KIM, TAE IL

    Bio-inspired Electronics for Enhancing Human Capability

    Professor Tae-il Kim's research team combined biomimetic technology (technically reinterpreting the motifs obtained from natural structures) with flexible electronics (electronic devices assembled on a deformable substrate) to study new “bio-inspired electronics”. The team’s research has been conducted to overcome the limitations of the size and performance of existing bioelectronic devices using semiconductor-based processes and utilized in various artificial sensory organs (visual, tactile, auditory, etc.). [1] In particular, by presenting the world's smallest technologies such as artificial eardrums that simulate the spiders’ vibration receptors (lyriform slit organ) it can be an alternative technology to artificial snail tube devices (artificial cochlear implants), which are existing bio-devices. It is also useful for curvilinear structures such as the eyes, which can lead to the enhancement of human sensory organs. Related technologies can be combined with nerve interface technology to control or stimulate stress cortisol hormones by measuring or stimulating the electrical activity of nerves with biomimetic elements. In addition, the team presented hierarchical structures inspired by termite mound structures which have wonderful heat dissipation systems [2] and applied the flexible device to prevent thermal degradation and enhance the thermal response of the flexible electronic device. [3] The technology related to flexible biomimetic devices could be applied not only to bio-devices but also to rollable and foldable devices.[4] Based on such unique techniques and good insights, we have many alumni from R&D researchers in Samsung and LG to postdoctoral researchers at top-level universities. [1]. Yei Hwan Jung, B. Park, J.U. Kim, and Tae-il Kim*, "Bioinspired Electronics for artificial sensory systems" Adv. Mater. 31 (34) 183637 (Aug 2019) [impact factor 25.809] [2] Byeonghak Park, J.U. Kim, J. Kim, D. Tahk, C. Jeong, J. Ok, J. Shin, D. Kang, Tae-il Kim* "Strain-Visualization with Ultrasensitive Nanoscale Crack-based Sensor Assembled with Hierarchical Thermochromic Membrane" Adv. Funct. Mater. 29 (40) 1903360 (Oct 2019) [impact factor 15.621] [3]. Haeleen Hong, Y.H. Jung, J.S. Lee, C. Jeong, J.U. Kim, S. Lee, H. Ryu, H. Kim, and Tae-il Kim*, "Anisotropic thermal conductive composite by guided assembly of boron nitride nanosheets for flexible and stretchable electronics", Adv. Funct. Mater. 29 (37) 1902575 (Sep 2019) [impact factor 15.621] [4]. Chanho Jeong, J.S. Lee, B. Park, C.S. Hong, J.U. Kim and Tae-il Kim*, "Controllable Configuration of Sensing Band in a Pressure-Sensor by Lenticular Pattern Deformation on Designated Electrodes", Adv. Mater. 31 (36), 1902689 (Sep 2019) [impact factor 25.809]

  • Reverting “Cold tumors” into “Hot tumors” by ImmunoBioengineering

    SKKU Advanced Institute of Nano Technology Prof. LIM, YONGTAIK

    Reverting “Cold tumors” into “Hot tumors” by ImmunoBioengineering

    Prof. Yong Taik Lim’s group of Sungkyunkwan university reported that 2 different immune nano converters that can overcome the limitation of immune checkpoint inhibitors which is related to the 2018 Nobel Prize in Physiology and Medicine (Advanced Materials, September 6 / ACS nano, October 7 Online publication). Although immune checkpoint inhibitors (Anti-CTLA4, Anti-PD-1, and Anti-PD-L1, etc) are highly attracted as promising immunotherapeutic, the response rate is very low, which ranges from approximately 5~30% depending on the target tumors. The reason for this is that various immunosuppressive factors in the tumor microenvironment hindered activation of the therapeutic immune cells. To overcome this, many pharmaceutical companies around the world are focusing on developing treatment technologies to improve the response rate of immune checkpoint inhibitor. The key technologies to increase the response rate to immune checkpoint inhibitors are inducing differentiation and proliferation of antigen-specific T cells, which actually kill cancer cells, and controlling immunosuppressive cells (MDSC, TAM, and Treg) and immunosuppressive cytokines (TGF-β and IL-10) in tumor microenvironment. By controlling the function of immunosuppressive cells present in the tumor microenvironment, “cold tumor” that does not respond to immune checkpoint inhibitors can be reverted to “hot tumor” that does respond immune checkpoint inhibitors and activation of therapeutic dendritic cells, T cells and macrophage cells. In this study, the release of resiquimod (R848) was controlled from 2 different immune nano converters to reduce systemic toxicity. The two platform technologies in this study were 1) developed in a implantable disc to prevent recurrence and metastasis of cancer in situations where the cancer is not completely removed by surgery, 2) lyophilizable nanoemulsion that can be applied to cancer immunotherapy as well as infectious diseases. The two newly developed platforms are developed as biocompatible materials that have been approved for human and are highly likely to be clinically approved. Two platform technologies are expected as personalized cancer vaccines that can be loaded personalized cancer drug and neo-antigen from cancer patients to enhanced immune checkpoint inhibitor respond rates through the analysis of various immunological factors in each cancer patients. Paper title: Designer scaffold with immune nanoconverters for reverting immunosuppression and enhancing immune checkpoint blockade therapy (Advanced Materials, September 6, 2019) Paper title: Lyophilizable and Multifaceted Toll-Like Receptor 7/8 Agonist-Loaded Nanoemulsion for the Reprogramming of Tumor Microenvironments and Enhanced Cancer Immunotherapy (ACS nano, October 7, 2019)

  • New Method for Evaluating the Combustion Stability of Hydrogen/Oxygen Bipropellant

    Mechanical Engineering Prof. KWON, OHCHAE

    New Method for Evaluating the Combustion Stability of Hydrogen/Oxygen Bipropellant

    Oh Chae Kwon, professor of mechanical engineering, has suggested a method for evaluating the combustion stability of hydrogen/oxygen bipropellant. It is expected to be a fundamental technology for the diversification of liquid rockets propellants in Korea.The results of the research that was supported by the space core technology program promoted by the Ministry of Science and ICT and the National Research Foundation of Korea have been published on August 1 in the print edition of 'Energy'. Turbulent combustion is a complex process involving a wide range of length scales. In order to comprehend turbulent combustion phenomena in rocket engines, it is needed to investigate the turbulence-chemistry interaction that determines the flame-front structure. While the combustion characteristics of kerosene/ oxygen propellants have been recently investigated in Korea, however, the combustion characteristics of the hydrogen propellant have not been extensively studied. Hydrogen propellant which has been highlighted as a propellant of reusable rockets has various advantages such as high specific impulse and eco-friendly features compared with other conventional liquid bipropellants such as kerosene. Thus, hydrogen propellant has been used for commercial rocket engines in other countries and has the potential to be developed in Korea. His research team conducted combustion experiments, measuring combustion stability limits using a high-pressure model combustor which is designed to endure pressure up to 60 bar and a propellant supply facility capable of feeding cryogenic liquid oxygen in order to simulate actual rocket engine operating conditions. The combustion stability limits such as flame extinction and instability are directly related to the stability of rocket engines, and the results can be used for the baseline data of hydrogen rocket engine design. They analyzed the mixing and spray characteristics in various injection conditions by changing temperature, pressure, phase and injection velocity and investigated the combustion characteristics by visualizing flames. A new method to estimate Damkohler number (Da) using the flame visualization was suggested. The proposed modified Da provides the limits for the occurrence of combustion instability. A regime diagram has been constructed through the mapping of flame structure onto a two-dimensional plot. This achievement is meaningful in that it provides criteria for evaluating the combustion characteristics of propellants in general, even if the variables related to combustion such as the size of the combustion chamber, propellant flow rate, propellant injection velocity and propellant type are changed. Combustion stability limits which are measured under specific experimental conditions seem to be difficult to be used in evaluating actual rocket engines with different conditions. This dimensionless number which was applied to gas turbines and boilers can also be used for the evaluation of liquid rocket engines as well.

  • Lung cancer can be quickly diagnosed at low cost

    Chemical Engineering Prof. UM, SOONG HO ·Researcher YUK, JISOO

    Lung cancer can be quickly diagnosed at low cost

    Sungkyunkwan University (President: Dong Ryeol SHIN) announced on July 17 that Prof. Soong Ho UM from the Dept. of Chemical Engineering and Prof. Myung Ju AHN from the Dept. of Hematology and Oncology of SKKU Medical School have identified ways to dramatically improve lung cancer diagnosis. The previous lung cancer screenings took about three weeks with high cost, but as result of this research, it is expected to be diagnosed in vitro within about three hours at low cost. The researchers developed a high-performance nucleic acid nanostructure-graphene oxide complex and realized a high-speed, real-time, and multi-diagnosis of specific gene combinations of lung cancer disease without PCR. The time required for cancer diagnosis was dramatically shortened and applied to liquid biopsy, which is emerging as a non-invasive and patient-friendly cancer diagnosis method. As a result, simultaneous diagnosis of multiple biomarkers of lung cancer applicable to liquid biopsy has opened the possibility of establishing a phased lung cancer treatment model. The first author, Ms. Ji Soo YUK, developed a nucleic acid structure-graphene oxide platform that selectively discriminates the combination of epidermal growth factor receptor (EGFR), a representative biomarker and microRNAs for lung cancer. They are well known as cancer cell fingerprint genes that contain information about the process of cancer cell progress. This platform also enables the distinction of point mutations that show a difference in one single gene mutation. In addition, multiple biomarkers are determined in real time within 3 hours, so that ultra-simplicity and ultra-precision cancer diagnosis can be performed. The mutation of a specific gene or the change in the expression rate of genetic materials is thought to affect the development and progression of cancer. In the case of lung cancer, EGFR gene mutation is a typical biomarker, and 35 ~ 50% of Asian patients are similar. Recently, it has been attracting much attention because it is known that the expression of microRNA (as well as EGFR mutants) directly affects the production of cancer tumor. To detect these genes, target biomaterial samples should be secured by invasive and surgical methods. This causes considerable physical and mental pain for the patient and the utilization of technology is significantly limited depending on the location of the tumor. In addition, the genetic testing process takes weeks after tissue collection. Therefore, a patient-friendly diagnostic method is urgently required to evaluate the suitability and resistance of each patient's drug in a comprehensive manner. In this study, a high-speed diagnostic platform applicable to blood was developed. The mutation of the EGFR gene can be used actively in clinical prescription of the therapeutic agent, and simultaneous identification of the microRNA group will contribute greatly to the discovery and treatment of new cancer biomarkers. The researchers have built a nano-barcoding platform system with a new nano-hybrid material between a fluorescent nucleic acid biopolymer and graphene oxide in a triangular column model. The system is designed to selectively respond to microRNAs originating from lung cancer and specific gene biomarkers such as EGFR mutants, and specific fluorescent switches are designed to react and turn on in the presence of a specific biomarker. This is applicable to various gene biomarkers at the same time and is diagnosed in vitro, so it can be used in various aspects such as gene diagnosis and prevention kit in clinical practice. In fact, we have solved the comprehensive problems of clinical kits and have explored the possibility of precision medicine for the first time. This reagent type platform is commercialized under the name of 'FluorgraTM' in DNANO Inc. (President: Young Ku Lee). “The short-term screening time and the applicability to liquid biopsy are enabling real-time monitoring of drug efficacy in conjunction with fast prescriptions for clinical diagnosis, and thus customized treatment for patients is being realized,” said Professor Soong Ho UM. “This will evolve into a form like a commercialized pregnancy diagnosis kit and provide convenience for health and welfare in daily life as soon as possible.”

  • Ultrafast, ultralow power consuming terabit-scale memory integration based on 2D materials

    Energy Science Prof. YANG, HEEJUN ·Researcher SUN LINFENG

    Ultrafast, ultralow power consuming terabit-scale memory integration based on 2D materials

    Prof. YANG’s research group recently reported a new conceptual memory system that can be integrated up to terabit-scale by using 2D graphene and h-BN. The 2D memory device operates with an ultralow power (micro-Jules) and a time constant of tens of nanoseconds, which is 100 times faster than current non-volatile memory devices (e.g., flash memory). Unlike conventional phase change memory (PRAM) or resistance random access memory (RRAM), such high device integration with 2D materials has demonstrated various fabrication and materials issues. Moreover, most 2D semiconductors have shown not-reliable operations. Prof. YANG’s team conceived a new conceptual memory device: combining volatile and non-volatile memory devices based on representative and most stable 2D materials; graphene and h-BN. Thus, the self-selective memory does not require a ‘selector device’ that is essential for other integrated devices. Moreover, the 2D materials allow device operation with 1000 times lower power consumption and 100 faster speed. Quantum tunneling through the 2D insulator and a reliable filament formation at the inert graphene were used for the operation. Prof. YANG mentioned that the ‘self-selective memory’ is the first case to demonstrate the feasibility for large-scale memory device integration with 2D materials. While conventional oxide materials show the limitations on the operating power and speed, the self-selective memory will be widely used for the future memory applications in AI and other neuromorphic industry. This research has been published in Nature Communications (IF=11.880) on July 18, 2019. Self-selective memory with graphene and h-BN. A memory of ‘SKKU’ with 25 memory cells are demonstrated.

  • Triboelectricity for charging medical implants

    Advanced Materials Science and Engineering Prof. KIM, SANGWOO ·Prof. Hongjoon YOON · Ronan HINCHET

    Triboelectricity for charging medical implants

    Electronic implants offer many benefits but they are all powered by batteries that need to be replaced regularly through surgery, resulting in additional risks and costs. In this regard, powering medical implants is of great interest. Korean researchers at Sungkyunkwan University (SKKU) reported energy harvesting technology driven by ultrasound. Their study will be published through the journal Science on August 2nd. Ultrasound, transmitted through the skin, makes Perfluoroalkoxy (PFA) membrane vibrate with about 200 μm of displacement at 20 kHz. Under ultrasound excitation, the membrane vibrates in a multimode, which ultimately induces continuous triboelectrification. Prof. Sang-Woo Kim's research team suggested the triboelectric energy harvesting technology driven by transcutaneous ultrasound for powering medical implants. His group demonstrated mechanical energy harvesting by ultrasound using a rat skin. They also discovered that harvesting in a porcine tissue is feasible with vibrating and implantable triboelectric generator (VI-TEG). On top of that, they successfully charged Li-ion battery by taking advantage of the triboelectric generators for the first time. Prof. KIM stated that "We showed for the first time the triboelectrification inside the body induced by transcutaneous ultrasound, which enables powering biomedical implants in safe and convenience manner." "We believe that our findings will be influential on future medical implants market." [Reference] R. Hinchet et al., (2019) “Transcutaneous ultrasound energy harvesting using capacitive triboelectric technology.” Science [Main Author] Hong-Joon YOON (Sungkyunkwan University), Sang-Woo KIM (Sungkyunkwan University) * Contact email: Professor Sang-Woo KIM (kimsw1@skku.edu)

  • Syringeable immunotherapeutic nanogel reshapes tumor microenvironment and prevents tumor metastasis and recurrence

    SKKU Advanced Institute of Nano Technology Prof. LIM, YONGTAIK ·SONG, CHANYOUNG

    Syringeable immunotherapeutic nanogel reshapes tumor microenvironment and prevents tumor metastasis and recurrence

    Surgery maintains its strong position as a therapeutic modality for treating established solid tumors, and various immunotherapies, such as cancer vaccines and checkpoint therapies. Adoptive T cell transfer are applied to treat residual tumors after surgery and prevent tumor recurrence and metastasis. However, immunotherapies have a low response rate, which ranges from approximately 5-30% depending on the target tumor. Recently, Prof. Yong Taik LIM’s research team from Sungkyunkwan University reported a syringeable immunomodulatory multidomain nanogel (iGel) that overcame the limitation by reprogramming the pro-tumoral tumor microenvironment (TME) to antitumoral immune niches. Local and extended release of immunomodulatory drugs from iGel deplete immunosuppressive cells, while inducing immunogenic cell death, it increased immunogenicity. When iGel is applied as a local postsurgical treatment, both systemic antitumor immunity and a memory T cell response are generated, and the recurrence and metastasis of tumors to lungs and other organs are significantly inhibited. Reshaping of the TME using iGel also reverts non-responding groups to checkpoint blockade therapies into responding groups. The iGel is expected as an immunotherapeutic platform that can reshape immunosuppressive TMEs and synergize cancer immunotherapy with checkpoint therapies, with minimized systemic toxicity. Thesis Title: Syringeable immunotherapeutic nanogel reshapes tumor microenvironment and prevents tumor metastasis and recurrence

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