Myung-Suk Chun

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Verified

Myung-Suk verified their affiliation via an institutional email.

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• Ph.D.
• Group Leader at Korea Institute of Science and Technology

In order to exactly understand the curvature-induced secondary flow motion, the steady electro-osmotic flow (EOF) is investigated by applying the full Poisson-Boltzmann/Navier-Stokes equations in a whole domain of the rectangular microchannel. The momentum equation is solved with the continuity equation as the pressure-velocity coupling achieves co...

The human bone marrow-derived mesenchymal stem cells (hMSCs) consist of heterogeneous subpopulations with different multipotent properties: small and large cells with high and low multipotency, respectively. Accordingly, sorting of a target subpopulation from the others is very important to increase the effectiveness of cell-based therapy. We perfo...

We develop a theoretical model of the electrokinetic streaming potential considering the Navier–Stokes equation coupled with the Poisson–Boltzmann equation in order to elaborate the possible applicability of the microfluidic-battery from conceptualization to system validation. The ion transport in the microchannel is described on the basis of the N...

The ability of antimicrobial peptides (AMPs) for effective binding to multiple target microbes has drawn lots of attention as an alternative to antibodies for detecting whole bacteria. We investigated pathogenic Escherichia coli (E. coli) detection by applying a microfluidic based biosensing device embedded with AMP-labeled beads. According to a ne...

To elaborate on the applicability of the electrokinetic micro power generation, we designed and fabricated the silicon-glass as well as the PDMS-glass microfluidic chips with the unique features of a multi-channel. Besides miniaturizing the device, the key advantage of our microfluidic chip utilization lies in the reduction in water flow rate. Both...

Human bone marrow-derived mesenchymal stem cells (hMSCs) comprise diverse subpopulations with different levels of multipotency, which refers to the capability of stem cells to differentiate into a limited range of cell types. Notably, smaller cells typically exhibit greater multipotency, whereas larger cells show reduced differentiation potential....

Provided is an apparatus for cell particle sorting based on microfluidic-chip flow, by using a design in which Dean flow focusing occurring in a spiral channel and hydrodynamic filtration are coupled. The apparatus comprises a first substrate including a spiral channel having an inner surface and an outer surface based on a radius of curvature, a s...

Microfluidic-chip based hydrodynamic filtration is one of the passive sorting techniques that can separate cell or particle suspensions into subpopulations of different sizes. As the branch channels and side channels play an important role in maintaining particle focusing, their rational design is necessary for highly efficient sorting. A model fra...

Bacterial infections represent a serious and global threat in modern medicine; thus, it is very important to rapidly detect pathogenic bacteria, such as Escherichia coli (E. coli) O157:H7. Once treatments are delayed after the commencement of symptoms, the patient’s health quickly deteriorates. Hence, real-time detection and monitoring of infectiou...

Stem cell technologies have presented explicit evidence of the neurodevelopmental hypothesis of schizophrenia. However, few studies investigated relevance of the schizophrenia genetic liability and the use of genetic reprogramming on pluripotent stem cells to the impaired neurodevelopment shown by stem cells. Therefore, this study sought to investi...

In this study, the model framework that includes almost all relevant parameters of interest has been developed to quantify the electrostatic potential and charge density occurring in microchannels grafted with polyelectrolyte brushes and simultaneously filled with polyelectrolyte dispersion. The brush layer is described by the Alexander-de Gennes m...

Flow features of rheologically complex fluids inside curved microchannels should be meaningfully scrutinized for effective mixing, sorting, and manipulation of nano- and micro-sized colloids or particles. In this study, a particle streak velocimetry method with coordinate transformation is incorporated to depict experimentally the axial velocity pr...

As one of the flow-based passive sorting, the hydrodynamic filtration (HDF) using a microfluidic-chip has shown to effectively separate into different sizes of subpopulations from cell or particle suspensions. Its model framework involving two-phase Newtonian or generalized Newtonian fluid (GNF) was developed, by performing the complete analysis of...

To effectively control the mixing of target materials inside microfluidic devices, the Dean flow features of generalized-Newtonian Bird-Carreau (BC) fluids in curved rectangular channels are theoretically investigated, as a passive technique. Governing equations coupled with the Cauchy momentum equation and the BC model are solved using the finite...

The model framework of hydrodynamic filtration was examined for the rational design of particle sorting, by considering the complete analysis of 3D laminar flow for flow fraction and complicated networks of main and multiple branch channels. As the objective parameters for tuning of the design, both the number of branch channels and each length of...

The fabrication of power generators utilized by streaming potential has been attracting profound interests for various applications such as wearable healthcare and self-powered micro/nano systems. So far, streaming potential has been generated by a charged channel wall and accumulated counter-ions. However, this approach is assumed as no-slip bound...

Particle migration phenomena in parallel slit channel flows of concentrated suspensions with asymmetric velocity profiles, which are governed by planar Couette–Poiseuille (C-P) flow conditions, are numerically investigated employing the diffusive flux model (DFM) via the finite volume method. The particle distributions predicted by DFM are confirme...

A curved channel is indispensable for the lab-on-chips system because it provides a convenient scheme for increasing the channel length per unit chip area in the direction of net flow. A secondary Dean flow in curved rectangular microchannels is examined by applying a finite volume scheme with a semi-implicit method for pressure-linked equations re...

The sensitivity of two-dimensional (2-D) film casting processes for viscoelastic fluids is investigated using a transfer function approach based on the transient frequency response method. The transient responses of state variables to step-changed film tension have been conveniently changed into corresponding transfer functions via the Laplace tran...

Draw resonance onsets of actual viscoelastic spinning processes with secondary forces operated by constant draw ratio are determined via transient frequency response simulations under a constant tension or force boundary condition, which causes the system to be always stable. Transfer function data between the spinline velocity and the tension at t...

Effects of the characteristics of membrane such as water permeability-coefficient, solute permeability-coefficient, and membrane resistivity on the performances of the spiral wound module in the PRO system have been studied numerically. Fluxes of water and solute through membrane, and concentrations and flow rates in the channels were obtained. The...

Water sorption and diffusion are essential physicochemical properties of a high-performance superabsorbent polymer (SAP). We combine the Park model with the obstruction-scaling model and the water clustering in confined spaces of the polymer hydrogel. Special attention is focused on elucidating the effect of chain stiffness by considering the confo...

The pressure-retarded osmosis system with the spiral wound module for power generation has been studied numerically. The system includes draw channel, membrane, and feed-channel. The water flux and the solute flux across membrane were calculated. In addition, changes in concentration, flow rate, and pressure of channel-fluids were obtained. Water f...

In the spiral wound module of the pressure-retarded osmosis (PRO) system for the salinity gradient power generation, effects of the inlet pressure differences between feed-channel and draw-channel were studied. Fluxes of water and solute through membrane and power were estimated. The water flux through membrane decreased along the x-direction and i...

The scaling relationship of the longest relaxation time of a single chain of semiflexible biological polyelectrolyte has been investigated by performing well-established coarse-grained Brownian dynamics simulations. Two kinds of longest relaxation times were estimated from time-sequences of chain trajectories, and their behaviors were interpreted b...

In order to understand the moisture diffusion, we combine the obstruction-scaling model with the moisture clustering in confined spaces of the polymer hydrogel, with relevance to the performance of the super desiccant polymer. Special attention is focused on elucidating the effect of chain stiffness by considering the conformation of polymer chain...

By extending the theoretical model previously formulated for the single unit problem, we fully analyze the performance of the reverse electrodialysis stack module aiming for electric power generation. In our prototype, each single unit is assembled in serial, where the mixing is allowed in connecting channels to exclude the ionic polarization. The...

Continuous supercritical hydrothermal synthesis of olivine (LiFePO4) nanoparticles was carried out using mixing tees of three different geometries; a 90° tee (a conventional Swagelok® T-union), a 50° tee, and a swirling tee. The effects of mixing tee geometry and flow rates on the properties of the synthesized LiFePO4, including particle size, surf...

The secondary flow motion that is induced by curvature of microscale channel is thoroughly studied with simulation and experimental validation. The steady-state solution of the electroosmotic flow is achieved by applying the full Poisson-Boltzmann and the Navier-Stokes equations that are associated throughout the whole domain of the rectangular mic...

It is very important to separate the human bone marrow-derived mesenchymal stem cells (hMSCs) with high multipotential to differentiation and to increase the efficacy of cell therapy. In this view, we have investigated to develop and validate a novel method for the collection of desired size of hMSCs by utilizing the microfluidic chip with main, si...

Conformational dynamics of a single chain of wormlike polyelectrolyte xanthan polymer has been investigated in the external flow fields by employing a well-suited coarse-grained Brownian dynamics simulation. This goes beyond other simulations, which do not consider the hydrodynamic interaction between pairs of beads in polyelectrolyte polysaccharid...

Polyelectrolytes are characterized by charged soft matters bearing ionic groups and accompanying counter-ions, such as water-soluble biomolecules, DNA, and polysaccharides. This implies complication arising from Debye screening effect and high sensitivity to external fields. We investigated conformation and translational diffusion of the single cha...

The Rouse-Zimm model based on the polymer dynamics theory allows us to predict the relaxation time of polyelectrolyte dilute solution as a function of the intrinsic viscosity. In finite concentrated solutions, the empirical analysis adopted in this study is quite useful to examine the relaxation behavior, noting that proper theories are not well-cl...

The confinement-induced conformational transitions of the polyelectrolyte chain are characterized with the coarse-grained Brownian dynamics simulations and the blob theory. Submicron-sized biopolymer xanthan is chosen as a model polyelectrolyte taking into account both flexible and semiflexible chains for comparison. Confined flexible and semiflexi...

The numerical solver for the velocity field equation describing laminar pulsatile flows driven by a time-dependent pressure drop in the straight microfluidic channel of square cross-section is developed. In the computational algorithm, an orthogonal collocation on finite element scheme for spatial discretizations is combined with an adaptive Runge-...

Direct single molecule tracking of a polyelectrolyte chain by using fluorescence microscopy has allowed both the assumptions and the predictions of relevant theories to be tested. The center-ofmass displacement is determined as a function of the time that elapses between images, where the radius of gyration can be estimated from a first moment of t...

Dispersion stability of surface-modified cerium oxide (CeO2) nanoparticles in ethylene glycol is examined and the experimental stability results are compared with an extended DLVO model consisting of electrostatic, van der Waals, and hydrophobic/hydrophilic interactions. Unmodified, decanoic acid-modified and oleic acid-modified CeO2 nanoparticles...

The curved channel appears to be indispensable for the lab-on-chips systems because it provides a convenient scheme for increasing the channel length per unit chip area in the direction of net flow. A secondary Dean flow in curved rectangular microchannels is examined by applying the finite-volume scheme with a semi-implicit method for pressure-lin...

Time-dependent velocity profile and concentration distributions formed in a single reverse electrodialysis (RED) unit have been successfully pursued using simulation framework for evaluating performance of the unit, i.e., open circuit voltage and short circuit current. The single RED unit consists of two adjunct fluid channels, separated by the sem...

The migration and conformation of a single lambda-DNA chain in a microchannel with a 90 degrees bend have been investigated using the hybrid numerical scheme of Brownian dynamics (BD) simulations and a CFD (computational fluid dynamics) solver, Flow-3D. A significant displacement of the single DNA chain was found after it had passed through the mic...

This presentation reports the numerical framework and important new results regarding the velocity pattern, vorticity, and mixing property, with variations of channel geometry and heterogeneity of surface properties. Extending our previous studies, secondary Dean flow in curved rectangular microchannels is examined by applying the finite volume/SIM...

Recently, we introduced a secondary Dean flow in curved rectangular microchannels by applying the finite volume scheme with a SIMPLE (semi-implicit method for pressure-linked equations) algorithm for the pressure-driven electrokinetic transport (Yun et al., 2010). This framework is based on the theoretical model coupled with the full Poisson-Boltzm...

Microfluidic designs require the effort to understand the flow pattern depending on the channel geometry. An in-depth analysis based on the theoretical model is presented for the pressure-driven electrokinetic microflows in curved rectangular channels by applying the finite volume scheme with a SIMPLE semi-implicit method for pressure-linked equati...

The scaling prediction of semiflexible wormlike chain was examined by applying Brownian dynamics simulation, which goes beyond other simulations as they do not consider both the hydrodynamic interaction between pairs of beads and long-range screening effect. The rheological behavior of the intrinsic viscosity was properly implemented by combining w...

In our recent Brownian dynamics (BD) simulation study, the structure and dynamics of anionic polyelectrolyte xanthan in bulk solution as well as confined spaces of slitlike channel were examined by applying a coarse-grained model with nonlinear bead-spring discretization of a whole chain [J. Jeon and M.-S. Chun, J. Chem. Phys. 126, 154904 (2007)]....

To form an electrorheological network (ERN), semiconducting nanoparticles were embedded in a polymer that was cross-linked to restrict particle motion. The microstructure ranged from random to aligned, depending on the degree of field-induced particle alignment during chemical network formation. We investigated in detail the softness effects of the...

A coarse-grained model of semiflexible anionic polyelectrolyte xanthan is applied and its structure and dynamics are examined with Brownian dynamics (BD) simulations both in a bulk solution and under confinement between two parallel plates. The modeling is based on the nonlinear bead-spring discretization of a chain with additional long-range elect...

A coarse‐grained modeling is based on the frnitely extendable nonlinear elastic (FENE) spring with long‐range electrostatic and hydrodynamic interactions between pairs of beads, where both flexible and semiflexible chains are developed. We also consider steric and electrostatic interactions between the bead and the confining walls of different char...

We have investigated the role of gold nanoparticle incorporated in the bulk-heterojunction active layer of poly(3-hexylthiophene) (P3HT)/fullerene. Since the performance of this organic photovoltaic device is strongly related to the charge carrier transport mobility of bulk heterojunction that arises from the molecular ordering of P3HT semiconducto...

Understanding of electrophoretic mobility and zeta potential is an important issue in charge characteristics of proteins for proteomics research. By exploring the electrostatic and electrokinetic principles, we presented a framework that would allow rigorous interpretations of surface zeta potential and effective charge for highly charged condition...

We have developed the explicit model incorporated together the finite difference scheme for electrokinetic flow in rectangular microchannels encompassing Navier's boundary slip. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in t...

A polyelectrolyte chain confined in a slit nanochannel exhibits a structural transition from the one in free space. In this paper, the effect of the long-range electrostatic interactions between the xanthan polyelectrolyte and the slit wall on the confined xanthan conformation is investigated via the Brownian dynamics simulation. A neutral and two...

This paper addresses the effects of microchannel geometry with electrically insulating posts on a particle flow driven by electrokinesis and dielectrophoresis. An in-house numerical program is developed using a numerical model proposed in literature to predict particle flows in a microchannel with a circular post array. The numerical program is val...

Understanding the behavior of a polyelectrolyte in confined spaces has direct relevance in design and manipulation of microfluidic devices, as well as transport in living organisms. In this paper, a coarse-grained model of anionic semiflexible polyelectrolyte is applied, and its structure and dynamics are fully examined with Brownian dynamics (BD)...

The surface of submicrometer silica spheres are modified with aminopropyl and phenyl groups through a one-step process. Various experimental techniques, i.e., scanning electron microscopy (SEM), quasi-elastic light scattering (QELS), differential scanning calorimetry (DSC), thermogravimetry (TG), zeta potential measurement, nitrogen sorption, and w...

Organosilane-functionalized Fe3O4 composite particles are prepared by reacting organosilane precursor, bis[(3-trimethoxysilyl)propyl]-ethylenediamine (TSPED) on Fe3O4 magnetic particles. To examine the adsorption and desorption properties of the composites, brilliant blue FCF (BBF) is used as a model adsorbate. The effects of solution pH, ionic str...

The behavior of the slip length and the long-range repulsion plays an essential role for design and operation in many of μTAS devices. We have developed the explicit model incorporated together the finite difference scheme for electrokinetic flow in rectangular microchannels encompassing Navier's boundary slip. The externally applied body force ori...

We present a finite difference solution for electrokinetic flow in rectangular microchannels encompassing Navier's fluid slip phenomena. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in the equation of motion. The basic principl...

A slit-like flow channel was designed to allow for fluorescent microscope visualization in the microfluidic chip fabricated with glass substrate and polydimethylsiloxane (PDMS). For the exposure time, moving fluorescent polystyrene latexes of 1 μm radius result in image streaks, where the latex concentration is sufficiently dilute underlying the co...

A dilute colloidal suspension confined in a slit channel, where the dispersed nanoparticles are nonuniformly charged, is considered. Long-range interactions due to the electrostatic potential are analyzed under the Debye-Hückel theory. The hindered behavior with respect to concentration partitioning and hindered diffusion have been examined intensi...

In order to elaborate the possible applicability of microfluidic power generation from conceptualization to system validation, we adopt a theoretical model of the electrokinetic streaming potential previously developed for the single channel problem. The ion transport in the microchannel is described on the basis of the Nernst-Planck equation, and...

Once an organic membrane is treated with a gas containing reactive fluorine (F2), its surface gets new physical and chemical properties according as some H in the polymer structure is replaced with F. Since the surface hydrophilicity as well as the surface charge density may change according to the fluorination extent, we have expected an effect of...

We present computational results on the static properties of concentrated dispersions of bidisperse colloids. The long-range electrostatic interactions between dissimilar spherical colloids are determined using the singularity method, which provides rigorous solutions to the linearized electrostatic field. The NVT Monte Carlo simulation is applied...

We examine rigorous computations on microstructural as well as rheological properties of concentrated dis-persions of bidisperse colloids. The NVT Monte Carlo simulation is applied to obtain the radial distribution function for the concentrated system. The long-range electrostatic interactions between dissimilar spherical colloids are determined us...

The streaming potential is generated by the electrokinetic flow effect within the electrical double layer of a charged solid surface. Surface charge properties are commonly quantified in terms of the zeta potential obtained by computation with the Helmholtz-Smoluchowski (H-S) equation following experimental measurement of streaming potential. In or...

By applying a configurational-bias Gibbs ensemble Monte Carlo algorithm, priority simulation results regarding the conformation of non-dilute polyelectrolytes in solvents are obtained. Solutions of freely-jointed chains are considered, and a new method termed strandwise configurational-bias sampling is developed so as to effectively overcome a diff...

An experimental investigation of the electrokinetic streaming potentials of both fully and partially retentive nanopores as compared with the filtration progress of dilute globular protein solution under different surface charge conditions was performed using hollow fibers. The streaming potential is generated by the electrokinetic flow effect with...

UV-Visible spectroscopy and scanning tunneling microscopy (STM) studies were performed to explore reduction potentials of cation-exchanged Keggin-type heteropolyacid (HPA) catalysts. Absorption band edge and negative differential resistance (NDR) peak voltage of cation-exchanged HPA samples determined by UV-Visible spectroscopy and STM, respectivel...

In cases of the microfluidic channel, the electrokinetic influence on the transport behavior can be found. The externally applied body force originated from the electrostatic interaction between the nonlinear Poisson-Boltzmann field and the flow-induced electrical field is applied in the equation of motion. The electrostatic potential profile is co...

Partition coefficients and concentration profiles of rigid, non-spherical, axisymmetric particles between bulk solution and cylindrical pores have been calculated by stochastic Gibbs ensemble Monte Carlo (GEMC) simulation. The element spheres are used to describe the axisymmetric, non-spherical particles. The method of element spheres for describin...

We have investigated the microstructural properties of a weakly charged polyelectrolyte modeled with both Hookean spring and Debye-Hückel potential, by employing a novel hybrid scheme of molecular dynamics (MD) and Monte Carlo (MC) simulations. Although the off-lattice pivot step facilitates the earlier computations stage, it gives rise to oscillat...

In cases of the microfluidic channel, where the thickness of electric double layer is often comparable with the characteristic size of flow channels, the electrokinetic influence on the flow behavior can be found. The externally applied body force originating from the electrostatic interaction between the linearized Poisson-Boltzmann field and the...

In the confined space of narrow channels, the behavior of rodlike polyelectrolytes pertaining to anisotropic configuration effect is much different than in the bulk. Based on our previous study, we analyzed on the orientational order of rodlike polyelectrolyte in dilute suspensions under the action of the long-range colloidal interactions, which re...

The microstructural properties of charged polyelectrolytes described by a potential model regarding both the harmonic springs and interaction were investigated by employing a hybrid scheme of molecular dynamics(MD) and Monte Carlo(MC) simulations. Based on the previous hybrid scheme, a novel hybrid scheme has been developed in the present study, wi...

We investigated the molecular simulations based on the Gibbs ensemble Monte Carlo method, which was previously applied to the colloidal suspensions confined with a narrow pore. The long-range electrostatic interactions between the particle and the adjacent fiber and between pairs of particles are evaluated by adopting the earlier methods. For uncha...

In order to investigate effects of the colloidal interaction in the membrane filtrations, the dead-end ultrafiltration of latex colloids was conducted with fully retentive membranes. Experimental results concerning the permeate flux during the filtration indicate that the void fraction of cake layer increased with the decrease of the ionic strength...

The glass ball inserted membrane module presented in this study is designed to enhance filtration in a flat sheet membrane. Three different modes of filtration experiments were conducted and compared to demonstrate flux enhancement due to the presence of glass balls: A normal dead-end filtration, a vortex flow filtration, and an enhanced vortex flo...

Even though purely steric partitioning within well-defined pores was treated, analytical approximations based on perturbed approach have been proved to be unreliable predictions of concentrated colloids for the whole range of relative pore size from wide to narrow. In this study, simulation results from Gibbs ensemble Monte Carlo method on electros...

: Aside from the virial expansion and density functional methods, theoretical results on the con-centration partitioning behavior for charged colloids within cylindrical pores have not been presented so far. With the increase of relative solute size as well as solute concentration, however, the approximate analytic methods have proven to be unrelia...

In this paper an extended analysis on a hollow-fiber membrane absorber is conducted for CO2 removal from flue gases. A rigorous model of gas–liquid mass transfer is developed on both narrow channels in and around the hollow fibers, including the gas absorption occurring from the reaction between CO2 and aqueous K2CO3 absorbent. CO2 concentration pr...

Equilibrium partitioning of spherical solutes between slit pores and bulk solution is investigated by the Gibbs ensemble Monte Carlo method. Two types of perturbatins are performed in this simulation: a random displacement of solutes that ensures equilibrium within both bulk and pore regions, and random interchanges of solutes that equalize the int...

A concentration depletion is developed nearby a capillary wall from the result of flow-induced radial migration to the axis region of capillary incorporating with the chain extension. The velocity enhancement factor can be defined quantifying the migration of polymers. For the experimental observation of the radial migration, the capillary hydrodyn...

The ionic strength dependence of intrinsic viscosity as a function of molecular weight was observed substantially for the anionic xanthan polyelectrolyte, while the intrinsic viscosity of nonionic schizophyllan does not change with ionic strength. Ultrasonic degradation was applied as the best mean of obtaining polymer fractions of different molecu...

In the vicinity of an interface, the properties of polymer are strongly modified relative to the properties of bulk solution. Polymers are entropically excluded from the vicinity of a neighboring wall in confined spaces, which results in a concentration depleted layer. A theoretical model of the concentration profile and the depleted layer thicknes...

Polymer solutions flowing through small-diameter capillaries of which length scale is much larger than that of polymers were experimentally demonstrated to have the enhanced flow rate as compared to in bulk flow. Thisapparent slip phenomenon was analyzed by obtaining theslip velocity and concentrationdepleted layer thickness. Hydrolyzed polyacrylam...

The extended approximate analysis on the electrostatic potential distribution around a spherical colloidal particle in asymmetric electrolytes has been performed. This analysis originated from the accurate perturbed scheme of Ohshima et al.[8] pertaining to the spherical Poisson-Boltzmann equation for symmetric electrolytes. The advantage of this a...