Seunghun Lee

Korea Institute of Materials Science

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Jun-Young Yang

Korea Institute of Materials Science

Do-Geun Kim

Korea Brain Research Institute

Sung‐Gyu Park

Korea Institute of Materials Science

ChaeWon Mun

Korea Institute of Materials Science

Sunghoon Jung

Gachon University

Jong‐Kuk Kim

Korea Institute for Advanced Study

Dong‐Ho Kim

Korea Institute of Materials Science

Nobuhiko Nishiyama

Tokyo Institute of Technology

Shigehisa Arai

Tokyo Institute of Technology

Soo Hyun Lee

Korea Institute of Materials Science

Cooperative Institutions

Seoul National University

131

Samsung (South Korea)

130

Government of the Republic of Korea

126

Korea Advanced Institute of Science and Technology

119

Pusan National University

Yonsei University

Korea University

Korea Institute of Materials Science

Sungkyunkwan University

Pohang University of Science and Technology

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Effects of rib structure and compression on liquid water transport in the gas diffusion layer of a polymer electrolyte membrane fuel cell

Journal of Mechanical Science and Technology (2022)

Seunghun Lee Hyung Min Kim

Water Transport

Gaseous diffusion

Lattice Boltzmann methods

10.1007/s12206-021-1222-8

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Citations (8)

Hydrogel-Assisted 3D Volumetric Hotspot for Sensitive Detection by Surface-Enhanced Raman Spectroscopy

International Journal of Molecular Sciences (2022)

Soo Hyun Lee Sunho Kim Jun-Young Yang ChaeWon Mun Seunghun Lee

Effective hotspot engineering with facile and cost-effective fabrication procedures is critical for the practical application of surface-enhanced Raman spectroscopy (SERS). We propose a SERS substrate composed of a metal film over polyimide nanopillars (MFPNs) with three-dimensional (3D) volumetric hotspots for this purpose. The 3D MFPNs were fabricated through a two-step process of maskless plasma etching and hydrogel encapsulation. The probe molecules dispersed in solution were highly concentrated in the 3D hydrogel networks, which provided a further enhancement of the SERS signals. SERS performance parameters such as the SERS enhancement factor, limit-of-detection, and signal reproducibility were investigated with Cyanine5 (Cy5) acid Raman dye solutions and were compared with those of hydrogel-free MFPNs with two-dimensional hotspots. The hydrogel-coated MFPNs enabled the reliable detection of Cy5 acid, even when the Cy5 concentration was as low as 100 pM. We believe that the 3D volumetric hotspots created by introducing a hydrogel layer onto plasmonic nanostructures demonstrate excellent potential for the sensitive and reproducible detection of toxic and hazardous molecules.

Surface-Enhanced Raman Spectroscopy

Nanopillar

10.3390/ijms23021004

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Citations (9)

Characteristics of Aqueous Chemical Species Generation in Plasma‐Facing Liquid Systems Using Helium Jet Plasma

ChemistryOpen (2024)

Joo Young Park Jin Hee Bae Seunghun Lee

Abstract Plasma‐facing liquids (PFLs) facilitate the storage of reactive O and N species (RONS), including H 2 O 2 and NO 2 − , which remain in the PFL after plasma treatment, and they can continuously influence the target immersed in the liquid. However, their behaviors and levels of generation and extinction depend strongly on the plasma characteristics and liquid condition. Therefore, understanding the effects of the liquid type on the plasma discharge characteristics and the RONS generated via plasma discharge is necessary. We compared the RONS generation and storage trends of deionized H 2 O and a high‐conductivity PFL, RPMI 1640, which is a well‐known cell culture medium commonly used to culture mammalian cells. RPMI 1640 acted as an electrode and enhanced the plasma discharge power by supplying abundant radicals and RONS. The production of gaseous hydroxyl radicals and NO markedly increased, which facilitated H 2 O 2 and NO 2 − production in the PFL for the first 200 s, and then the increase in the RONS concentration stagnated. With respect to storage, as the components within RMPI 1640 exhibited high reaction constants for their reactions with H 2 O 2 , H 2 O 2 elimination was completed in <30 min. Unlike H 2 O 2 , the concentration of NO 2 − in the PFL was unchanged.

10.1002/open.202300213

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Citations (2)

Hydrogenated Amorphous Carbon Films Prepared by Filtered Vacuum Arc Method with Various C₂H₂Pressures

Japanese Journal of Applied Physics (2011)

Seunghun Lee Sung Hwan Yoon Jong‐Kuk Kim Do-Geun Kim

Hydrogenated amorphous carbon films (a-C:H) were deposited on silicon (100) substrates using a filtered vacuum arc (FVA) method. A graphite cathode and acetylene (C 2 H 2 ) at various flow rates were used to synthesize the carbon films. The deposition rate of the carbon films without C 2 H 2 addition was 5 nm/min, whereas the deposition rate increased from 23 to 82 nm/min with increasing C 2 H 2 flow rate from 2.5 to 20 sccm. The supply of C 2 H 2 gas induces an increase in CH radical density near the substrate, resulting in a high deposition rate. The plasma diagnostics using optical emission spectroscopy showed that the emission peak intensity of the CH radicals (A 3 Π g –X 3 Π u , 431.26 nm) increased with increasing C 2 H 2 flow rate. Raman spectroscopy revealed a change in the deposited films from nano-crystalline graphite to a-C:H as the C 2 H 2 flow rate was increased.

Vacuum arc

Amorphous carbon

Acetylene

Carbon fibers

Deposition

10.1143/jjap.50.01ah01

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Citations (3)

Frequency division multiple transmission method to utilize the wide bandwidth property of capacitive micromachined ultrasonic transducer arrays

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2013)

Seunghun Lee Bae-Hyung Kim Taeho Jeon Youngil Kim Kyungil Cho

CMUT-on-ASIC integration techniques are promising for the development of lower cost smaller volume scanners with higher performance in terms of features and image qualities because it minimizes parasitic capacitances and ultimately improves signal-to-noise ratio (SNR). Moreover, a frequency bandwidth of CMUT array is known as relatively broader than that of other ultrasonic transducer arrays. To utilize the wide bandwidth characteristic of the CMUT arrays, in this paper, we introduce a FDMA (frequency division multiple access) based ultrasound imaging technique using orthogonally band-divided coded signals to provide dynamic transmit focused imaging without sacrificing the frame rate. In the presented method, the orthogonal sub-band coded signals are simultaneously fired on multiple ranges, in which each signal is focused at a different range, in one transmission event. This paper also presents an ultrasound imageformation method and a modulation and demodulation process of orthogonal sub-band coded signals designed within the frequency bandwidth of the CMUT arrays. The presented method is verified by computer simulations using Field II and experiments. The simulation results using a computer generated tissue mimicking phantom show that the presented method can be achieved with both increased image quality and frame rate. The experimental results to verify the feasibility of the presented method using orthogonal sub-band coded signals show that the reflected signals from targets are successfully separated into two compressed signals. Currently, we are extending the presented approach to ultrasound imaging technique for volumetric ultrasound scanners using 2-D CMUT-on-ASIC arrays.

Frequency band

Frame rate

10.1117/12.2006719

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Citations (2)

Experimental and simulation study on performance evaluation for flame retardancy of polyurethane

Journal of Loss Prevention in the Process Industries (2024)

Junseo Lee Seunghun Lee Sehyeon Oh Byung-Chol Ma

10.1016/j.jlp.2024.105303

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Citations (2)

Effect of Ar Ion Beam Treatment on the Interfacial Adhesion between a Fluorinated Ethylene Propylene (Fep) Film and Sputtered Cu

Jun-Young Yang Seunghun Lee Eun‐Yeon Byeon Joo Young Park Dogeun Kim

10.2139/ssrn.5020229

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Bandwidth enhancement of injection-locked distributed reflector lasers with wirelike active regions

Optics Express (2010)

Seunghun Lee Devang Parekh Takahiko Shindo Weijian Yang Peng Guo

The modulation bandwidth enhancement of distributed reflector (DR) lasers with wirelike active regions utilizing optical injection locking is demonstrated both theoretically and experimentally. By the rate equation analysis, it is shown that DR lasers with wirelike active regions realize a low optical injection power and a large bandwidth enhancement under small operation currents. Experimentally, the small-signal bandwidth is increased to >15 GHz at a bias current of 5 mA, which is 4 times smaller than that for conventional edge-emitting lasers. A large signal modulation at 10 Gbps is also performed at the same bias current of 5 mA and voltage swing of 0.4 V(pp), and error-free detection was confirmed under the low-power conditions.

Biasing

Modulation (music)

10.1364/oe.18.016370

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Citations (17)

Preliminary Validation of a Continuum Model for Dimple Patterns on Polyethylene Naphthalate via Ar Ion Beam Sputtering

Polymers (2021)

Jun-Young Yang Sunghoon Jung Eun‐Yeon Byeon Hyun Hwi Lee Do-Geun Kim

This work reports the self-organization of dimple nanostructures on a polyethylene naphthalate (PEN) surface where an Ar ion beam was irradiated at an ion energy of 600 eV. The peak-to-peak roughness and diameter of dimple nanostructures were 29.1~53.4 nm and 63.4~77.6 nm, respectively. The electron energy loss spectrum at the peaks and troughs of dimples showed similar C=C, C=O, and O=CH bonding statuses. In addition, wide-angle X-ray scattering showed that Ar ion beam irradiation did not induce crystallization of the PEN surface. That meant that the self-organization on the PEN surface could be due to the ion-induced surface instability of the amorphous layer and not due to the partial crystallinity differences of the peaks and valleys. A nonlinear continuum model described surface instability due to Ar ion-induced sputtering. The Kuramoto-Sivashinsky model reproduced the dimple morphologies numerically, which was similar to the experimentally observed dimple patterns. This preliminary validation showed the possibility that the continuum equation used for metal and semiconductor surfaces could be applied to polymer surfaces where ion beam sputtering occurred.

Dimple

Polyethylene naphthalate

10.3390/polym13121932

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Citations (5)

Aerodynamics of a comb-like plate inspired by a fairyfly wing

Seunghun Lee Daegyoum Kim

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