24 results on '"Minjeong Ha"'
Search Results
2. Modified application of SAMe-TTR scoring system in Asian patients with atrial fibrillation for the selection of oral anticoagulants
- Author
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Seong Won Jeon, Nuri Lee, Ki Hong Lee, Minjeong Ha, Changhyun Kim, Yoo Ri Kim, Nam Sik Yoon, and Hyung Wook Park
- Subjects
warfarin ,prothrombin time ,atrial fibrillation ,thromboembolism ,safety ,Medicine - Abstract
Background/Aims The SAMe-TT2R2 score is used for assessing anticoagulation control (AC) quality with warfarin. However, it is hard to apply SAMe-TT2R2 score in Asian patients with atrial fibrillation (AF), because it has not been proven in those populations. This study aimed to validate the SAMe-TT2R2 score in Asian patients with AF and suggest a modified SAMe-TT2R2 score for this population. Methods We analyzed 710 Korean patients with AF who were using warfarin. The AC quality was assessed as the mean time in therapeutic range (TTR). Each component of SAMe-TT2R2 score was evaluated for the relationship with AC. Further clinical factors that predict AC were analyzed. Identified factors were re-assorted and constructed as SA2Me-TTR scoring system. Results Of the components of the SAMe-TT2R2 score, female, age, and rhythm control were associated with AC. Heart failure and renal insufficiency were newly identified factors associated with AC. The modified SA2Me-TTR score was reconstructed with the relevant risk factors (S, female gender, 1 point; A, age < 60 yr, 2 points; Me, medical history of heart failure, 1 point; T, treatment for rhythm control, 1 point; T, history of stroke or transient ischemic attack, 1 point; R, renal insufficiency, 1 point). The modified SA2Me-TTR score demonstrated an excellent relationship with the grading of AC. The modified SA2Me-TTR score ≤ 1 identified patients with good AC (hazard ratio 2.46, 95% CI 1.75–3.47). Conclusions The modified SA2Me-TTR score was useful for guiding oral anticoagulants selection in Asian patients with AF.
- Published
- 2024
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3. High-Performance Hybrid Photovoltaics with Efficient Interfacial Contacts between Vertically Aligned ZnO Nanowire Arrays and Organic Semiconductors
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Yoon Ho Lee, Minjeong Ha, Inho Song, Jeong Hun Lee, Yousang Won, Seongdong Lim, Hyunhyub Ko, and Joon Hak Oh
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Chemistry ,QD1-999 - Published
- 2019
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4. High-Resolution Filtration Patterning of Silver Nanowire Electrodes for Flexible and Transparent Optoelectronic Devices
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Hyunhyub Ko, Minsoo Kim, Youngsu Lee, Taehyo Kim, Seongdong Lim, Hochan Lee, Saewon Kang, Jin Young Kim, Minjeong Ha, Doo-Seung Um, and Ziyauddin Khan
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Photocurrent ,Shadow mask ,Materials science ,business.industry ,Bend radius ,Photodetector ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Flexible electronics ,0104 chemical sciences ,Electrode ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Solution process ,Polyimide - Abstract
Silver nanowire (AgNW) electrodes attract significant attention in flexible and transparent optoelectronic devices; however, high-resolution patterning of AgNW electrodes remains a considerable challenge. In this study, we have introduced a simple technique for high-resolution solution patterning of AgNW networks, based on simple filtration of AgNW solution on a patterned polyimide shadow mask. This solution process allows the smallest pattern size of AgNW electrodes, down to a width of 3.5 μm. In addition, we have demonstrated the potential of these patterned AgNW electrodes for applications in flexible optoelectronic devices, such as photodetectors. Specifically, for flexible and semitransparent UV photodetectors, AgNW electrodes are embedded in sputtered ZnO films to enhance the photocurrent by light scattering and trapping, which resulted in a significantly enhanced photocurrent (up to 800%) compared to devices based on AgNW electrodes mounted on top of ZnO films. In addition, our photodetector could be operated well under extremely bent conditions (bending radius of approximately 770 μm) and provide excellent durability even after 500 bending cycles.
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- 2020
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5. High-Performance Hybrid Photovoltaics with Efficient Interfacial Contacts between Vertically Aligned ZnO Nanowire Arrays and Organic Semiconductors
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Hyunhyub Ko, Yousang Won, Minjeong Ha, Inho Song, Seongdong Lim, Joon Hak Oh, Jeong Hun Lee, and Yoonho Lee
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Electron mobility ,Fabrication ,Materials science ,Organic solar cell ,business.industry ,General Chemical Engineering ,Exciton ,Nanowire ,Heterojunction ,General Chemistry ,Article ,Organic semiconductor ,lcsh:Chemistry ,lcsh:QD1-999 ,Photovoltaics ,Optoelectronics ,business - Abstract
Hybrid photovoltaics (HPVs) incorporating both organic and inorganic semiconducting materials have attracted much attention as next-generation photovoltaics because of their advantage of combining both materials. The hybridization of ZnO nanowires (NWs) and organic semiconductors is expected to be a suitable approach to overcome the limited exciton diffusion length and low electron mobility associated with current organic photovoltaics. The use of ZnO NWs allows researchers to tune nanoscale dimensions more precisely and to achieve rod-to-rod spacing below 10 nm. However, the perfect incorporation of organic semiconductors into densely packed ZnO NW arrays has yet to be achieved. In this study, we report the fabrication of ZnO NW arrays and various organic heterojunction-based HPVs using the feasible and effective vacuum-assisted double coating (VADC) method, achieving full coverage of the organic semiconductors on the compact ZnO NW arrays. The newly proposed VADC method ensures perfect infiltration and full coverage of the organic semiconductors on the densely packed NW arrays. Compared with the conventional single spin-coating process, the use of the VADC method led to 11 and 14% increases in the power conversion efficiency of P3HT:PCBM- and PBDTTT-C-T:PC71BM-based HPVs, respectively. Our studies provide a feasible method for the fabrication of efficient HPVs.
- Published
- 2019
6. Printable anisotropic magnetoresistance sensors for highly compliant electronics
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Jürgen Fassbender, Denys Makarov, Eduardo Sergio Oliveros Mata, Gilbert Santiago Cañón Bermúdez, Y. Zabila, Minjeong Ha, and Tobias Kosub
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Permalloy ,Materials science ,Magnetoresistance ,business.industry ,Tantalum ,Bend radius ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Bending ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry ,Printed electronics ,Optoelectronics ,General Materials Science ,Electronics ,0210 nano-technology ,business ,Electrical conductor - Abstract
Printed electronics are attractive due to their low-cost and large-area processing features, which have been successfully extended to magnetoresistive sensors and devices. Here, we introduce and characterize a new kind of magnetoresistive paste based on the anisotropic magnetoresistive (AMR) effect. The paste is a composite of 100-nm-thick permalloy/tantalum flakes embedded in an elastomer matrix, which promotes the formation of appropriately conductive percolation networks. Sensors printed with this paste showed stable magnetoresistive properties upon mechanical bending. The AMR value of this sensor is $$0.34\%$$ 0.34 % in the field of 400 mT. Still, the response is stable and allows to resolve sub-mT field steps. When printed on ultra-thin 2.5-$$\upmu \hbox {m}$$ μ m -thick Mylar foil, the sensor can be completely folded without losing magnetoresistive performance and mechanically withstand $$20\, \upmu {\hbox {m}}$$ 20 μ m bending radius. The developed compliant printed AMR sensor would be attractive to implement on curved and/or dynamic bendable surfaces for on-skin applications and interactive printed electronics.
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- 2021
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7. Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly
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Benjamin A. Evans, Minjeong Ha, Eduardo Sergio Oliveros Mata, Jessica A.-C. Liu, Joseph B. Tracy, Denys Makarov, and Gilbert Santiago Cañón Bermúdez
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Materials science ,Mechanical Engineering ,Hinge ,Nanotechnology ,02 engineering and technology ,Folding (DSP implementation) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Smart material ,01 natural sciences ,Displacement (vector) ,0104 chemical sciences ,Magnetic field ,On board ,Magnetization ,Mechanics of Materials ,General Materials Science ,0210 nano-technology ,Actuator - Abstract
Origami utilizes orchestrated transformation of soft 2D structures into complex 3D architectures, mimicking shapes and functions found in nature. In contrast to origami in nature, synthetic origami lacks the ability to monitor the environment and correspondingly adjust its behavior. Here, magnetic origami actuators with capabilities to sense their orientation and displacement as well as detect their own magnetization state and readiness for supervised folding are designed, fabricated, and demonstrated. These origami actuators integrate photothermal heating and magnetic actuation by using composite thin films (≈60 µm thick) of shape-memory polymers with embedded magnetic NdFeB microparticles. Mechanically compliant magnetic field sensors, known as magnetosensitive electronic skins, are laminated on the surface of the soft actuators. These ultrathin actuators accomplish sequential folding and recovery, with hinge locations programmed on the fly. Endowing mechanically active smart materials with cognition is an important step toward realizing intelligent, stimuli-responsive structures.
- Published
- 2021
8. Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin-Conformal Electronics
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Yakun Wang, Rico Illing, Eduardo Sergio Oliveros Mata, Minjeong Ha, Ingolf Mönch, Jürgen Fassbender, Denys Makarov, Tobias Kosub, Y. Zabila, and Gilbert Santiago Cañón Bermúdez
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Materials science ,Magnetoresistance ,Spintronics ,business.industry ,Orders of magnitude (temperature) ,Mechanical Engineering ,Conformal map ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Elastomer ,01 natural sciences ,0104 chemical sciences ,Mechanics of Materials ,Scrolling ,Optoelectronics ,General Materials Science ,Electronics ,Zoom ,0210 nano-technology ,business - Abstract
Highly compliant electronics, naturally conforming to human skin, represent a paradigm shift in the interplay with the surroundings. Solution-processable printing technologies are yet to be developed to comply with requirements to mechanical conformability of on-skin appliances. Here, it is demonstrated that high-performance spintronic elements can be printed on ultrathin 3 µm thick polymeric foils enabling the mechanically imperceptible printed magnetoelectronics, which can adapt to the periodic buckling surface to be biaxially stretched over 100%. They constitute the first example of printed and stretchable giant magnetoresistive sensors, revealing 2 orders of magnitude improvements in mechanical stability and sensitivity at small magnetic fields, compared to the state-of-the-art printed magnetoelectronics. The key enabler of this performance enhancement is the use of elastomeric triblock copolymers as a binder for the magnetosensitive paste. Even when bent to a radius of 16 µm, the sensors printed on ultrathin foils remain intact and possess unmatched sensitivity for printed magnetoelectronics of 3 T-1 in a low magnetic field of 0.88 mT. The compliant printed sensors can be used as components of on-skin interactive electronics as it is demonstrated with a touchless control of virtual objects including zooming in and out of interactive maps and scrolling through electronic documents.
- Published
- 2020
9. Micro/nanostructured surfaces for self-powered and multifunctional electronic skins
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Youngoh Lee, Hyunhyub Ko, Seungse Cho, Jonghwa Park, and Minjeong Ha
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Materials science ,business.industry ,Biomedical Engineering ,Wearable computer ,Nanotechnology ,Robotics ,02 engineering and technology ,General Chemistry ,General Medicine ,Strain sensor ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Wireless ,General Materials Science ,Electronics ,Artificial intelligence ,0210 nano-technology ,business ,Energy harvesting ,Wearable technology ,Healthcare system - Abstract
Flexible electronic devices are regarded as one of the key technologies in wearable healthcare systems, wireless communications and smart personal electronics. For the realization of these applications, wearable energy and sensor devices are the two main technologies that need to be developed into lightweight, miniaturized, and flexible forms. In this review, we introduce recent advances in the controlled design of device structures into bioinspired micro/nanostructures and 2D/3D structures for the enhancement of energy harvesting and multifunctional sensing properties of flexible electronic skins. In addition, we highlight their potential applications in flexible/wearable electronics, sensors, robotics and prosthetics, and biomedical devices.
- Published
- 2020
10. Wearable and flexible sensors for user-interactive health-monitoring devices
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Seongdong Lim, Hyunhyub Ko, and Minjeong Ha
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Sustainable power ,Computer science ,business.industry ,Biomedical Engineering ,Wearable computer ,Robotics ,02 engineering and technology ,General Chemistry ,General Medicine ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Highly sensitive ,Key factors ,Human–computer interaction ,General Materials Science ,Electronics ,Artificial intelligence ,Medical diagnosis ,0210 nano-technology ,business ,Healthcare system - Abstract
Flexible electronic devices that are lightweight and wearable are critical for personal healthcare systems, which are not restricted by time and space. To monitor human bio-signals in a non-invasive manner, skin-conforming, highly sensitive, reliable, and sustainable healthcare monitoring devices are required. In this review, we introduce flexible and wearable sensors based on engineered functional nano/micro-materials with unique sensing capabilities for detection of physical and electrophysiological vital signs of humans. In addition, we investigate key factors for the development of user-interactive healthcare devices that are customizable, wearable, skin-conforming, and monolithic (design), and have long-term monitoring capability with sustainable power sources. Finally, we describe potential challenges of developing current wearable healthcare devices for applications in fitness, medical diagnosis, prosthetics, and robotics.
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- 2020
11. Biodegradable, electro-active chitin nanofiber films for flexible piezoelectric transducers
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Hyunhyub Ko, Jong Bok Kim, Byeongwook Choi, Sang Kyu Kwak, Chanho Park, Kyungtae Kim, Minjeong Ha, Han Sol Kang, Se Hun Joo, Bongjun Gu, Cheolmin Park, Seok Ju Kang, Ju Hyun Park, and Jungho Jin
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chemistry.chemical_classification ,Squid ,Materials science ,biology ,Renewable Energy, Sustainability and the Environment ,Nanotechnology ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferroelectricity ,Piezoelectricity ,0104 chemical sciences ,chemistry.chemical_compound ,Chitin ,chemistry ,Nanofiber ,biology.animal ,Electrode ,Chitinase ,biology.protein ,General Materials Science ,Electrical and Electronic Engineering ,0210 nano-technology - Abstract
Since the conventional fluorine-based electro-active polymers release toxic residues into the environment during their syntheses and decomposition processes, eco-friendly piezoelectric polymers are urgently demanded in the field of energy-related soft materials. Here, we derive a high-performance biodegradable chitin polymer from squid pen material and demonstrate its utility as a flexible piezoelectric material. The readily controlled ferroelectric chitin film confers excellent piezoelectricity under external mechanical pressure, resulting in comparable performance with that of conventional fluorine-based piezoelectric polymers. In particular, the sufficient piezoelectric behavior in chitin film allows us to not only realize a high-fidelity paper-type speaker and microphone that operates over a wide frequency range without significantly deteriorating the input and output sounds but also demonstrate transparent speaker consisting of AgNWs electrodes onto freestanding chitin film which also enables to resemble the original sound. Finally, the biodegradable chitin polymer can be successfully dissolved by chitinase enzyme within eight days without any toxic residues remained.
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- 2018
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12. Magnetic Actuators: Reconfigurable Magnetic Origami Actuators with On‐Board Sensing for Guided Assembly (Adv. Mater. 25/2021)
- Author
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Gilbert Santiago Cañón Bermúdez, Eduardo Sergio Oliveros Mata, Minjeong Ha, Joseph B. Tracy, Denys Makarov, Benjamin A. Evans, and Jessica A.-C. Liu
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On board ,Materials science ,Mechanics of Materials ,Mechanical Engineering ,Mechanical engineering ,General Materials Science ,Actuator - Published
- 2021
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13. Magnetoresistive Sensors: Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin‐Conformal Electronics (Adv. Mater. 12/2021)
- Author
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Rico Illing, Denys Makarov, Y. Zabila, Minjeong Ha, Ingolf Mönch, Jürgen Fassbender, Tobias Kosub, Gilbert Santiago Cañón Bermúdez, Eduardo Sergio Oliveros Mata, and Yakun Wang
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Materials science ,Magnetoresistance ,Mechanics of Materials ,business.industry ,Mechanical Engineering ,Optoelectronics ,General Materials Science ,Conformal map ,Electronics ,business - Published
- 2021
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14. Broadband omnidirectional light detection in flexible and hierarchical ZnO/Si heterojunction photodiodes
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Minjeong Ha, Yuanjing Lin, Seongdong Lim, Zhiyong Fan, Hyunhyub Ko, Doo-Seung Um, Youngsu Lee, and Qianpeng Zhang
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Photocurrent ,Microlens ,Materials science ,business.industry ,Bend radius ,Photodetector ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Photodiode ,law.invention ,Optics ,law ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,Image sensor ,0210 nano-technology ,business ,Omnidirectional antenna - Abstract
The development of flexible photodetectors has received great attention for future optoelectronic applications including flexible image sensors, biomedical imaging, and smart, wearable systems. Previously, omnidirectional photodetectors were only achievable by integration of a hemispherical microlens assembly on multiple photodetectors. Herein, a hierarchical photodiode design of ZnO nanowires (NWs) on honeycomb-structured Si (H-Si) membranes is demonstrated to exhibit excellent omnidirectional light-absorption ability and thus maintain high photocurrents over broad spectral ranges (365 to 1,100 nm) for wide incident angles (0° to 70°), which enabled broadband omnidirectional light detection in flexible photodetectors. Furthermore, the stress-relieving honeycomb pattern within the photodiode micromembranes provided photodetectors with excellent mechanical flexibility (10% decrease in photocurrent at a bending radius of 3 mm) and durability (minimal change in photocurrent over 10,000 bending cycles). When employed in semiconductor thin films, the hierarchical NW/honeycomb heterostructure design acts as an efficient platform for various optoelectronic devices requiring mechanical flexibility and broadband omnidirectional light detection.
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- 2016
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15. Skin-Inspired Hierarchical Polymer Architectures with Gradient Stiffness for Spacer-Free, Ultrathin, and Highly Sensitive Triboelectric Sensors
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Chunggi Baig, Youngoh Lee, Soowon Cho, Sangyoon Na, Seongdong Lim, Hyunhyub Ko, and Minjeong Ha
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chemistry.chemical_classification ,animal structures ,Materials science ,Nanoporous ,Effective stress ,technology, industry, and agriculture ,General Engineering ,General Physics and Astronomy ,Stiffness ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Highly sensitive ,Stress (mechanics) ,chemistry ,medicine ,General Materials Science ,Composite material ,medicine.symptom ,0210 nano-technology ,Elastic modulus ,Triboelectric effect - Abstract
The gradient stiffness between stiff epidermis and soft dermis with interlocked microridge structures in human skin induces effective stress transmission to underlying mechanoreceptors for enhanced tactile sensing. Inspired by skin structure and function, we fabricate hierarchical nanoporous and interlocked microridge structured polymers with gradient stiffness for spacer-free, ultrathin, and highly sensitive triboelectric sensors (TESs). The skin-inspired hierarchical polymers with gradient elastic modulus enhance the compressibility and contact areal differences due to effective transmission of the external stress from stiff to soft layers, resulting in highly sensitive TESs capable of detecting human vital signs and voice. In addition, the microridges in the interlocked polymers provide an effective variation of gap distance between interlocked layers without using the bulk spacer and thus facilitate the ultrathin and flexible design of TESs that could be worn on the body and detect a variety of pressing, bending, and twisting motions even in humid and underwater environments. Our TESs exhibit the highest power density (46.7 μW/cm
- Published
- 2018
16. Flexible Health-Monitoring Devices/Sensors
- Author
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Minjeong Ha, Seongdong Lim, and Hyunhyub Ko
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Materials science - Published
- 2018
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17. Bioinspired Interlocked and Hierarchical Design of ZnO Nanowire Arrays for Static and Dynamic Pressure-Sensitive Electronic Skins
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Youngoh Lee, Hyunhyub Ko, Seongdong Lim, Minjeong Ha, Doo-Seung Um, and Jonghwa Park
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Materials science ,business.industry ,Nanowire ,Electronic skin ,Response time ,Nanotechnology ,Static pressure ,Condensed Matter Physics ,Piezoelectricity ,Piezoresistive effect ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Electrochemistry ,Optoelectronics ,Dynamic pressure ,business ,Sound pressure - Abstract
The development of electronic skin (e-skin) is of great importance in human-like robotics, healthcare, wearable electronics, and medical applications. In this paper, a bioinspired e-skin design of hierarchical micro- and nano-structured ZnO nanowire (NW) arrays in an interlocked geometry is suggested for the sensitive detection of both static and dynamic tactile stimuli through piezoresistive and piezoelectric transduction modes, respectively. The interlocked hierarchical structures enable a stress-sensitive variation in the contact area between the interlocked ZnO NWs and also the efficient bending of ZnO NWs, which allow the sensitive detection of both static and dynamic tactile stimuli. The flexible e-skin in a piezoresistive mode shows a high pressure sensitivity (−6.8 kPa−1) and an ultrafast response time (
- Published
- 2015
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18. Giant Tunneling Piezoresistance of Composite Elastomers with Interlocked Microdome Arrays for Ultrasensitive and Multimodal Electronic Skins
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Jaehyung Hong, Youngoh Lee, Jonghwa Park, Minjeong Ha, Sung Youb Kim, Youngdo Jung, Hyuneui Lim, and Hyunhyub Ko
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Materials science ,Finite Element Analysis ,Composite number ,Electronic skin ,General Physics and Astronomy ,Artificial Limbs ,Nanotechnology ,Prosthesis Design ,Elastomer ,Signal ,Materials Testing ,Electrochemistry ,Pressure ,Humans ,General Materials Science ,Electronics ,Monitoring, Physiologic ,Skin ,Nanotubes, Carbon ,General Engineering ,Reproducibility of Results ,Robotics ,Piezoresistive effect ,Elastomers ,Contact area ,Tactile sensor - Abstract
The development of flexible electronic skins with high sensitivities and multimodal sensing capabilities is of great interest for applications ranging from human healthcare monitoring to robotic skins to prosthetic limbs. Although piezoresistive composite elastomers have shown great promise in this area of research, typically poor sensitivities and low response times, as well as signal drifts with temperature, have prevented further development of these materials in electronic skin applications. Here, we introduce and demonstrate a design of flexible electronic skins based on composite elastomer films that contain interlocked microdome arrays and display giant tunneling piezoresistance. Our design substantially increases the change in contact area upon loading and enables an extreme resistance-switching behavior (ROFF/RON of ∼10(5)). This translates into high sensitivity to pressure (-15.1 kPa(-1), ∼0.2 Pa minimum detection) and rapid response/relaxation times (∼0.04 s), with a minimal dependence on temperature variation. We show that our sensors can sensitively monitor human breathing flows and voice vibrations, highlighting their potential use in wearable human-health monitoring systems.
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- 2014
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19. Facile Synthesis of Solar Light Sensitive Ag/TiO2 Nanocatalyst Wrapped with Multiwalled Carbon Nanotubes
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Minjeong Ha, Gyusun Kyung, and Seonghyuk Ko
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Materials science ,Solar light ,General Materials Science ,Nanotechnology ,Multiwalled carbon - Published
- 2014
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20. Tailoring surface plasmons of high-density gold nanostar assemblies on metal films for surface-enhanced Raman spectroscopy
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Jiwon Lee, Minjeong Ha, Seungyoung Park, Youngsu Lee, Hyunhyub Ko, Bo Hua, and Zhiyong Fan
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Coupling ,Fabrication ,Materials science ,Surface plasmon ,Nanotechnology ,Dielectric ,Surface-enhanced Raman spectroscopy ,Metal ,symbols.namesake ,visual_art ,visual_art.visual_art_medium ,symbols ,General Materials Science ,Raman spectroscopy ,Plasmon - Abstract
Plasmonic systems based on metal nanoparticles on a metal film have generated great interest for surface-enhanced Raman spectroscopy (SERS) chemical sensors. In this study, we describe the fabrication of ultrasensitive SERS substrates based on high-density gold nanostar assemblies on silver films with tailored surface plasmons, where multiple field enhancements from particle–film and interparticle plasmon couplings and lightening rod effects of sharp tips of nanostars contribute to the enormous Raman enhancements. We show that the interplay between interparticle and particle–film plasmon couplings of high-density gold nanostars (GNSs) on metal and dielectric films as a function of interparticle separation can be tailored to provide maximum SERS effects. We observe that the SERS enhancement factor (EF) of GNSs on a metal film as a function of interparticle separation follows a broken power law function, where the EF increases with the interparticle separation for the strong interparticle coupling range below an interparticle separation of ∼0.8 times the GNS size, but decreases for the weak interparticle coupling range (for an interparticle separation of >0.8 times the GNS size). Finally, we demonstrate the use of tailored plasmonic substrates as ultrasensitive SERS chemical sensors with an attomole level of detection capability of 2,4-dinitrotoluene, a model compound of nitroaromatic explosives.
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- 2014
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21. Large-Area, Solution-Processed, Hierarchical MAPbI3 Nanoribbon Arrays for Self-Powered Flexible Photodetectors
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Youngsu Lee, Seongdong Lim, Minjeong Ha, and Hyunhyub Ko
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Materials science ,business.industry ,Photodetector ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Solution processed ,Optoelectronics ,0210 nano-technology ,business - Published
- 2018
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22. Triboelectric generators and sensors for self-powered wearable electronics
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Youngoh Lee, Jonghwa Park, Minjeong Ha, and Hyunhyub Ko
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Flexibility (engineering) ,Electric Power Supplies ,Computer science ,business.industry ,Textiles ,General Engineering ,Electrical engineering ,General Physics and Astronomy ,Nanotechnology ,Identification (information) ,Electricity ,Wireless ,Humans ,General Materials Science ,Electronics ,business ,Electromagnetic Phenomena ,Triboelectric effect ,Wearable technology ,Mechanical Phenomena - Abstract
In recent years, the field of wearable electronics has evolved at a rapid pace, requiring continued innovation in technologies in the fields of electronics, energy devices, and sensors. In particular, wearable devices have multiple applications in healthcare monitoring, identification, and wireless communications, and they are required to perform well while being lightweight and having small size, flexibility, low power consumption, and reliable sensing performances. In this Perspective, we introduce two recent reports on the triboelectric generators with high-power generation achieved using flexible and lightweight textiles or miniaturized and hybridized device configurations. In addition, we present a brief overview of recent developments and future prospects of triboelectric energy harvesters and sensors, which may enable fully self-powered wearable devices with significantly improved sensing capabilities.
- Published
- 2015
23. Synthesis and characterization of Ag/TiO2 nanoparticle with high photocatalytic activity under simulated visible light
- Author
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Minjeong Ha, Nattinee Bumbudsanpharoke, and Seonghyuk Ko
- Published
- 2014
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24. Factors Influencing Viewing Behavior in Live Streaming: An Interview-Based Survey of Music Fans
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Minjeong Ham and Sang Woo Lee
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fanship ,V Live ,live streaming service ,participation ,Technology ,Science - Abstract
V Live is a live-streaming service made by South Korean IT company in August 2015. The service provides diverse video contents specific to entertainment content. Most of V Live users are K-pop fans, and they actively express emotions on V Live content by writing comments, pressing “hearts”, and sharing video content. Based on Uses and Gratifications theory, this study investigated why people use live streaming service, and the factors influencing users’ viewing behavior in live streaming. We conducted an in-depth interview with V Live users. Based on the results of the interview, an online survey was conducted. As a result, six factors—“Interpersonal relationship motivation”, “Social presence motivation”, “Celebrity support motivation”, “Celebrity presence motivation”, “Social interaction motivation”, and “Differentiation motivation”—were derived as motivations to use V Live. While “Social presence motivation” and “Differentiation motivation” among V Live use motivations that have been shown to mediate the relationship between fans’ fanship and V Live viewing time, all motivations using V Live have been shown to mediate the relationship between fans’ fanship and V Live viewing participation.
- Published
- 2020
- Full Text
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