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Publication
Featured researches published by Sin Kwon.
ACS Nano | 2016
Zhaoyang Zhong; Hyungjin Lee; Dongwoo Kang; Sin Kwon; Young-Man Choi; Inhyuk Kim; Kwang Young Kim; Youngu Lee; Kyoohee Woo; Jooho Moon
Simple, low-cost and scalable patterning methods for Cu nanowire (NW)-based flexible transparent conducting electrodes (FTCEs) are essential for the widespread use of Cu NW FTCEs in numerous flexible optoelectronic devices, wearable devices, and electronic skins. In this paper, continuous patterning for Cu NW FTCEs via a combination of selective intense pulsed light (IPL) and roll-to-roll (R2R) wiping process was explored. The development of continuous R2R patterning could be achieved because there was significant difference in adhesion properties between NWs and substrates depending on whether Cu NW coated area was irradiated by IPL or not. Using a custom-built, R2R-based wiping apparatus, it was confirmed that nonirradiated NWs could be clearly removed out without any damage on irradiated NWs strongly adhered to the substrate, resulting in continuous production of low-cost Cu NW FTCE patterns. In addition, the variations in microscale pattern size by varying IPL process parameters/the mask aperture sizes were investigated, and possible factors affecting on developed pattern size were meticulously examined. Finally, the successful implementation of the patterned Cu NW FTCEs into a phosphorescent organic light-emitting diode (PhOLED) and a flexible transparent conductive heater (TCH) were demonstrated, verifying the applicability of the patterned FTCEs. It is believed that our study is the key step toward realizing the practical use of NW FTCEs in various flexible electronic devices.
ACS Applied Materials & Interfaces | 2017
Inhyuk Kim; Kyoohee Woo; Zhaoyang Zhong; Eonseok Lee; Dongwoo Kang; Sunho Jeong; Young-Man Choi; Yunseok Jang; Sin Kwon; Jooho Moon
Recently, highly flexible conductive features have been widely demanded for the development of various electronic applications, such as foldable displays, deformable lighting, disposable sensors, and flexible batteries. Herein, we report for the first time a selective photonic sintering-derived, highly reliable patterning approach for creating extremely flexible carbon nanotube (CNT)/silver nanoparticle (Ag NP) composite electrodes that can tolerate severe bending (20 000 cycles at a bending radius of 1 mm). The incorporation of CNTs into a Ag NP film can enhance not only the mechanical stability of electrodes but also the photonic-sintering efficiency when the composite is irradiated by intense pulsed light (IPL). Composite electrodes were patterned on various plastic substrates by a three-step process comprising coating, selective IPL irradiation, and wiping. A composite film selectively exposed to IPL could not be easily wiped from the substrate, because interfusion induced strong adhesion to the underlying polymer substrate. In contrast, a nonirradiated film adhered weakly to the substrate and was easily removed, enabling highly flexible patterned electrodes. The potential of our flexible electrode patterns was clearly demonstrated by fabricating a light-emitting diode circuit and a flexible transparent heater with unimpaired functionality under bending, rolling, and folding.
Review of Scientific Instruments | 2016
Hyunchang Kim; Eonseok Lee; Young-Man Choi; Sin Kwon; Seung-Hyun Lee; Jeongdai Jo; Taik-Min Lee; Dongwoo Kang
In printed electronics technology, the overlay accuracy of printed patterns is a very important issue when applying printing technology to the production of electric devices. In order to achieve accurate positioning of the printed patterns, this study proposes a novel precision reverse offset printing system. Furthermore, the study evaluates the effects of synchronization and printing force on position errors of the printed patterns, and presents methods of controlling synchronization and printing force so as to eliminate positional errors caused by the above-mentioned reasons. Finally, the printing position repeatability of 0.40 μm and 0.32 μm (x and y direction, respectively) at a sigma level is obtained over the dimension of 100 mm under repeated printing tests with identical printing conditions.
Nanoscale | 2018
Inhyuk Kim; Kyoohee Woo; Zhaoyang Zhong; Pyungsam Ko; Yunseok Jang; Minhun Jung; Jeongdai Jo; Sin Kwon; Seunghyun Lee; Sungwon Lee; Hongseok Youn; Jooho Moon
Recently, the demand for stretchable strain sensors used for detecting human motion is rapidly increasing. This paper proposes high-performance strain sensors based on Ag flake/Ag nanocrystal (NC) hybrid materials incorporated into a polydimethylsiloxane (PDMS) elastomer. The addition of Ag NCs into an Ag flake network enhances the electrical conductivity and sensitivity of the strain sensors. The intense localized heating of Ag flakes/NCs is induced by intense pulsed light (IPL) irradiation, to achieve efficient sintering of the Ag NCs within a second, without damaging the PDMS matrix. This leads to significant improvement in the sensor sensitivity. Our strain sensors are highly stretchable (maximum strain = 80%) and sensitive (gauge factor = 7.1) with high mechanical stability over 10 000 stretching cycles under 50% strain. For practical demonstration, the fabrication of a smart glove for detecting the motions of fingers and a sports band for measuring the applied arm strength is also presented. This study provides an effective method for fabricating elastomer-based high-performance stretchable electronics.
Applied Physics Express | 2015
Yunseok Jang; Jeongdai Jo; Young-Man Choi; Kyoohee Woo; Sin Kwon; Kwang-Young Kim
We adjusted the conductivity of a poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT/PSS) electrode and an injection barrier between the PEDOT/PSS source/drain (S/D) electrode and a pentacene semiconductor by adding HAuCl4 to a PEDOT/PSS solution. Gold in the PEDOT/PSS S/D electrode was synthesized by a redox reaction between PEDOT/PSS and Au ions. This reaction enhances the conductivity of the PEDOT/PSS S/D electrodes and reduces the injection barrier between the PEDOT/PSS S/D electrodes and the pentacene semiconductor, and causes the field-effect mobility to increase by about 230%. As such, it is considered a very useful method of making high-performance organic thin-film transistors (OTFTs).
Small | 2018
Zhaoyang Zhong; Kyoohee Woo; Inhyuk Kim; Hyuntae Kim; Pyeongsam Ko; Dongwoo Kang; Sin Kwon; Hyunchang Kim; Hongseok Youn; Jooho Moon
A simple route to fabricate defect-free Ag-nanoparticle-carbon-nanotube composite-based high-resolution mesh flexible transparent conducting electrodes (FTCEs) is explored. In the selective photonic sintering-based patterning process, a highly soft rubber or thin plastic substrate is utilized to achieve close and uniform contact between the composite layer and photomask, with which uniform light irradiation can be obtained with diminished light diffraction. This well-controlled process results in developing a fine and uniform mesh pattern (≈12 μm). The mesh patternability is confirmed to be dependent on heat distribution in the selectively light-irradiated film and the pattern design for FTCE could be adopted for more precise patterns with desired performance. Moreover, using a very thin substrate could allow the mesh to be positioned closer to the strain-free neutral mechanical plane. Due to strong interfacial adhesion between the mesh pattern and substrate, the mesh FTCE could tolerate severe mechanical deformation without performance degradation. It is demonstrated that a transparent heater with fine mesh patterns on thin substrate can maintain stability after 100 repeated washing test cycles in which a variety of stress situations occurring in combination. The presented highly durable FTCE and simple fabrication processes may be widely adoptable for various flexible, large-area, and wearable optoelectronic devices.
IEEE Transactions on Device and Materials Reliability | 2017
Yunseok Jang; Jeongdai Jo; Kyoohee Woo; Seunghyun Lee; Sin Kwon; Kwang-Young Kim; In-Young Kim
We herein demonstrate a method for reducing the surface energy in polymer insulators for high-performance organic thin-film transistors (OTFTs). The surface energy of the poly(4-vinyl phenol) (PVP) insulator was reduced from 45 mJ/m2 to 32 mJ/m2 by treatment with UV/Ozone and octadecyltrichlorosilane (ODTS). The pentacene growth was controlled by the surface energy. It caused the pentacene film deposited on the ODTS-treated PVP insulator to induce three-dimensional growth, leading to an increase in the field-effect mobility of approximately 109%. These results demonstrate that the method of adjusting the surface energy in polymer insulators is suitable for enhancing the performance of OTFTs.
Journal of Micromechanics and Microengineering | 2016
Ga Eul Kim; Kyoohee Woo; Dongwoo Kang; Yunseok Jang; Young-Man Choi; Moon G. Lee; Taik-Min Lee; Sin Kwon
In roll-offset printing (patterning) technology with a PDMS blanket as a transfer medium, one of the major reliability issues is the occurrence of swelling, which involves absorption of the ink solvent in the printing blanket with repeated printing. This study developed a method to resolve blanket swelling in gravure offset roll printing and performed experiments for performance verification. The physical phenomena of mass and heat transfer were applied to fabricate a device based on convection drying. The proposed device managed to effectively control blanket swelling through drying by blowing air and additional temperature control. The experiments verified that printing quality (in particular the variation of the width of printed patterns) was maintained over 500 continuous printing.
Nanoscale | 2016
Zhaoyang Zhong; Kyoohee Woo; Inhyuk Kim; Hyewon Hwang; Sin Kwon; Young-Man Choi; Youngu Lee; Taik Min Lee; Kwang-Young Kim; Jooho Moon
International Journal of Precision Engineering and Manufacturing | 2017
Sukhan Kim; Moonyong Lee; Kyoohee Woo; Hongseok Youn; Taik-Min Lee; Eung Ki Lee; Sin Kwon