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Dive into the research topics where Bong Hyun Kwon is active.

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Featured researches published by Bong Hyun Kwon.


Japanese Journal of Applied Physics | 2011

Improvement of the Size-Selective Separation of Microbeads in a Curved Microchannel Using Particle Focusing

Bong Hyun Kwon; Hyung Hoon Kim; Jemyung Cha; Cheol Hee Ahn; Takahiro Arakawa; Shuich Shoji; Jeung Sang Go

The size-selective microfluidic separation of glass beads in a curved rectangular microchannel was fabricated in our previous work. In this study, we improve its separation performance and attempt an experimental visualization to examine the separation resolution. In the previous work, we found by visualization that the trajectory of 20 µm glass beads was influenced by their travelling path along a straight inlet channel. Using a forced sheath flow, a consistent bead trajectory along the middle of the straight inlet channel was obtained, and the sheath angle to minimize the focusing width of the flowing distributed beads was determined to be 45°. The physical explanation for the dynamic behavior of microbeads was elaborated. When the ratio of Stokes force to centrifugal force mainly acting on a glass bead fell under unity, the glass bead moved out to the wall in spite of the fact that its size was less than the height of the zero velocity position. To examine the separation resolution, the newly designed size-selective separation microchannel with the sheath was fabricated and its separation performance was visualized. The movement of the glass beads showed a good agreement with the separation mechanism explained by the force ratio. The resolution of the separation was visualized to be 10 µm for the size of glass beads used in the experiment. The size-selective separation performance was explained in terms of physical forces and was improved by solving the previous problems. A cascade device for the continuous separation of microbeads of various sizes can improve the separation resolution.


Japanese Journal of Applied Physics | 2011

Improvement of Filtration Performance Using Self-Tuning of Flow Resistance

Dong Hyun Yoon; Yeon Kyoung Bahk; Bong Hyun Kwon; Seong Sik Kim; Yong Deok Kim; Takahiro Arakawa; Jeung Sang Go; Shuichi Shoji

In this paper, we present the filtration of a liquid sample from polystyrene microparticles analogous to the separation of a biological liquid from mixed particles such as whole blood. The proposed self-tuning of flow resistance can prevent the excessive clogging of microparticles in the microfilter by allowing the automatic change of the flow direction when the microfilter is clogged. Numerically, at about 80% of the clogging of microparticles in the pillar channel, the sample flow is regulated suddenly to the bypass channel. Experimentally, the clogging behavior at the five successive pillar channels and the self-tuning of flow are compared by measuring the clogging area and volume with time. Also, the microfilter array connected in a series can provide an increase in the sample volume proportionally without excessive pressure build-up. This implies the potential to reduce cell fracture in the filtration of biological cells.


Japanese Journal of Applied Physics | 2013

Separation of Different Sized Nanoparticles with Time Using a Rotational Flow

Bong Hyun Kwon; Hyung Hoon Kim; Jae Hyeong Park; Dong Hyun Yoon; Moon Chan Kim; Steve Sheard; Karl Morten; Jeung Sang Go

In this paper, we describe the development of a microfluidic centrifuge with two inlets and two outlets potentially capable of rapidly separating nanoparticles and nanovesicles. Compared with the microfluidic centrifuge with a single inlet and outlet, the 2 ×2 microfluidic centrifuge gives improved centrifugation performance by increasing momentum flux transfer, angular velocity, and centrifugal acceleration. The center of flow rotation and the symmetry of the horizontal velocity in the microchamber were examined numerically. On the basis of the determined maximum velocity, the angular velocity and centrifugal acceleration were also evaluated. The centrifugation time of three different nanoparticles was examined by calculating the time when the nanoparticles left the microchamber for the first time. For visual observation and quantitative measurement of nanoparticle centrifugation, a 2 ×2 microfluidic centrifuge was fabricated and the experimental results demonstrate similar physical behavior to those of a mechanical centrifuge. On the basis of a comparison of the centrifugation time of two different nanoparticle populations of 300 and 700 nm in diameter, we propose that nanoparticles of different sizes can be physically separated by time under a range of inlet volume flow rates.


international conference on solid-state sensors, actuators and microsystems | 2011

Frictional drag reduction in microchannel using slip on convex air bubbles naturally formed in a specifed a cavity

Bong Hyun Kwon; Hyung Hoi Kim; K. Park; J.H. Park; D.G. Choi; Jeung Sang Go

This paper presents the reduction of frictional drag by using the slip on the interface of convex air bubble. The visualization shows that the convex bubbles formed naturally in the hydrophobic cavity array positioned along a microchannel with time. The size of the bubbles depended on the size of the cavity size. The velocity distribution was also displayed by using a micro-PIV measurement. Then, the volume flow rate and the momentum were examined by increasing inlet flow rate for the different sizes of microbubble. The maximum reduction of frictional drag of 52 % was obtained.


Journal of the Korean Society of Visualization | 2014

Performance Evaluation of Rotational Flow of a 2×2 Microfluidic Centrifuge with varying Inlet Conditions and Chamber Sizes

Hyeong Jin Jeon; Bong Hyun Kwon; Dae Il Kim; Hyung Hoon Kim; Jeung Sang Go

This paper describes the measurement of performance evaluation of rotational flow varying chamber size and Reynolds number. Through the experimental visualization of the flow rotation, the number and position of flow rotation in the microfluidic centrifuge were examined. At a chamber width of 250, single flow rotation was obtained over at a Reynolds number of 300, while at a chamber width of 500 , single flow rotation did not appear. For performance evaluation, the intensity in microchamber was measured during 20 sec. At a chamber width of 250 , performance of rotational flow increased as Reynolds number increased. However, the variation of intensity in microchamber remained unchanged at a chamber width of 500 . The numerical analysis showed that the threshold centrifugal acceleration to obtain rotational flow for ejected particles was 200g.


nanotechnology materials and devices conference | 2012

Chemical modification of polymeric cantilever Sensors with multiamine supramolecular hydrogel

Yan Zhang; Hyung Hoon Kim; Bong Hyun Kwon; Jeung Sang Go

A chemical process to integrate stimuli-responsive hydrogels on SU-8 cantilever surface, taking advantage of the free epoxy groups of patterned SU-8 is reported. The network structure of the multiamine hydrogel is formed on the cantilever surface through a ring-opening and amine-substituted reaction at epoxy groups of SU-8. X-ray photoelectron spectroscopy (XPS) is used to demonstrate the effective placement of the supramolecular hydrogel (SH) on the patterned SU-8 surface. The enhanced practicability of functionalized SU-8 cantilever sensor is demonstrated by measuring the concentration of ferric ion, indicating a potential use of SH functionalized cantilever sensors.


Journal of the Korean Society of Visualization | 2012

Visualization of Rotational Flow for Chamber Size of a 2×2 Microfluidic Centrifuge

Hyeong Jin Jeon; Bong Hyun Kwon; Dae Il Kim; Jeung Sang Go

Abstract. This paper introduces a new parameter to design the 2×2 microfluidic centrifuge with singleflow rotation positioned at the center of microchamber. The dimensional centrifugal acceleration momen-tum flux which is defined as the interfacial momentum flux divided by distance from the center of thechamber explains the flow rotation and its threshold provides a reference to expect single flow rotation.Through the numerical and experimental visualization of the flow rotation, the number and position offlow rotation in the 2×2 microfluidic centrifuge were examined. At a channel width of 50µm and cham-ber width of 250µm, single flow rotation was obtained over at a Reynolds number of 300, while at achannel width of 100µm and chamber width of 500µm, single flow rotation did not appear. The numer-ical analysis showed that the threshold centrifugal acceleration momentum flux to obtain single flow rota-tion was 3500 kg/m·s 2 . Key Words:Microfluidic centrifuge(마이크로 유체 원심분리기), Flow rotation(회전 유동), Centrifugalacceleration momentum flux(원심가속 운동량 유속), Visualization(가시화)


Experiments in Fluids | 2014

Experimental study on the reduction of skin frictional drag in pipe flow by using convex air bubbles

Bong Hyun Kwon; Hyung Hoon Kim; Hyeong Jin Jeon; Moon Chan Kim; Inwon Lee; Sejong Chun; Jeung Sang Go


Sensors and Actuators B-chemical | 2013

Polymeric cantilever sensors functionalized with multiamine supramolecular hydrogel

Yan Zhang; Hyung Hoi Kim; Bong Hyun Kwon; Jeung Sang Go


Archive | 2010

METHOD FOR ATTACHING MICRO BUBBLE ARRAY ON PLATE SURFACE

Jeung Sang Go; Moon Jeong Kim; Bong Hyun Kwon

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Jeung Sang Go

Pusan National University

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Hyeong Jin Jeon

Pusan National University

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Hyung Hoon Kim

Pusan National University

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Dae Il Kim

Pusan National University

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Hyung Hoi Kim

Pusan National University

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Moon Chan Kim

Pusan National University

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Moon Jeong Kim

Pusan National University

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Yan Zhang

Pusan National University

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Takahiro Arakawa

Tokyo Medical and Dental University

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