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Polymeric vesicles (PVs) have proven to be a promising container for various agents because of the benefit of core–shell structures. The formation mechanism of PVs has been investigated in the hydr...

Pressure drop (Δp) and collection efficiency (η) are used to evaluate the separation performance of the cyclone separator. In this study, we conducted comparative study of cyclone models using response surface methodology (RSM), back propagation neural network (BPNN), and group method of data handling (GMDH) networks to develop optimal predictive cyclone models. Also, we conducted multi-objective optimization for maximizing model and minimizing model using genetic algorithm (GA). CFD was performed instead of experimental method to get the estimated values for modeling of Δp and η. The validation results of CFD showed 0.5% and 2% errors for Δp and η, respectively, compared with the experimental data. Second, design of experiment (DOE) analysis for 10 cyclone geometrical parameters was executed to obtain the significant geometrical parameters. Vortex finder diameter Dx, inlet width a, inlet height b and cone height Hco have a significant effect on η and Δp. However, interaction effects between the geometrical parameters have small effects. The cyclone models by RSM, BPNN and GMDH based on 25 CFD training set were developed. The predictive performance results by the cyclone models were compared by 25 CFD test set. The GMDH method achieved the best prediction for Δp ( ${R^2} = 99.7 $, RMSE = 0.102) $R_{\textrm{adjusted}}^2 = 98.99 $, RMSE = 0.0119) than the RSM, BPNN cyclone models. Additionally, uncertainty analysis was performed to estimate the quantitative performance of cyclone models. The results show that the uncertainty width of GMDH models achieved the best prediction ( $\eta $: ±0.0065, Δp: ±0.0188). Finally, GA was applied to optimize the GMDH models simultaneously. GA generated 70 non-dominant solutions. Reproducibility of five optimal points was validated by using CFD. The trade-off optimal point showed improvement by 24.31%, 18% and 8.79% for Δp ${\textrm{d}_{50}} $ and $\eta $, respectively.

This study investigated an influence of the temperature field on thickness distribution of thermoformed products using complex and high-aspect-ratio mold. The optimum temperature field was obtained to achieve a more uniform thickness distribution in the thermoformed products by using finite element simulation. The material properties of acrylonitrile-butadiene-styrene (ABS) polymer sheet were obtained by two rheological measurement tests. The linear viscoelastic properties, such as the storage modulus and loss modulus, were measured by a small amplitude oscillatory shear (SAOS) test for wide ranges of frequency and temperature. The discrete relaxation time and discrete relaxation modulus were obtained by nonlinear regression. The fitting parameters C1 and C2 for the WLF model were obtained by curve fitting. The nonlinear viscoelastic property, such as stress relaxation modulus, was measured by a step strain test. The damping function and fitting parameter α of Wagner-Demarmels (WD) model were determined by curve fitting. Then, the Kaye–Bernstein-Kearsley-Zapas (K-BKZ) constitutive equation was utilized to the thermoforming simulation in order to investigate the material behavior of the polymer sheet. The numerical results showed that a more uniform thickness distribution could be achieved with the optimum temperature field of the sheet. The thinnest part of the products was improved by more than 30%.

This paper presents a novel method to prevent blockages by embolic microspheres in catheter channels by using convex air bubbles attached to the channels&rsquo, inner wall surface. The clogging by microspheres can occur by the arching of the microspheres in the catheter. A few studies have been done on reducing the blockage, but their methods are not suitable for use with embolic catheters. In this study, straight catheter channels were fabricated. They had cavities to form convex air bubbles, additionally, a straight channel without the cavities was designed for comparison. Blockage was observed in the straight channel without the cavities, and the blockage arching angle was measured to be 70&deg, while no blockage occurred in the cavity channel with air bubbles, even at a geometrical arching angle of 85&deg, The convex air bubbles have an important role in preventing blockages by microspheres. The slip effect on the air bubble surface and the centrifugal effect make the microspheres drift away from the channel wall. It was observed that as the size of the cavity was increased, the drift distance became larger. Additionally, as more convex air bubbles were formed, the amount of early drift to the center increased. It will be advantageous to design a catheter with large cavities that have a small interval between them.

This paper deals with the characteristics of the cyclone separator from the Lagrangian perspective to design important dependent variables, develops a neural network model for predicting the separation performance parameter, and compares the predictive performance between the traditional surrogate model and the neural network model. In order to design the important parameters of the cyclone separator based on the particle separation theory, the force acting until the particles are separated was calculated using the Lagrangian-based CFD methodology. As a result, it was proved that the centrifugal force and drag acting on the critical diameter having a separation efficiency of 50% were similar, and the particle separation phenomenon in the cyclone occurred from the critical diameter, and it was set as an important dependent variable. For developing a critical diameter prediction model based on machine learning and multiple regression methods, Unsteady-RANS analyzes according to shape dimensions were performed. The input design variables for predicting the critical diameter were selected as four geometry parameters that affect the turbulent flow inside the cyclone. As a result of comparing the model prediction performances, the ML model showed the 32.5 % of improvement rate of R2 compared to the traditional MLR considering the nonlinear relationship between the cyclone design variable and the critical diameter. The proposed techniques have proven to be fast and practical tools for cyclone design.

In this paper, the characteristics of the cyclone separator was analyzed from the Lagrangian perspective for designing the important dependent variables. The neural network network model was developed for predicting the separation performance parameter. Further, the predictive performances were compared between the traditional surrogate model and the developed neural network model. In order to design the important parameters of the cyclone separator based on the particle separation theory, the force acting until the particles are separated was calculated using the Lagrangian-based computational fluid dynamics (CFD) methodology. As a result, it was proved that the centrifugal force and drag acting on the critical diameter having a separation efficiency of 50% were similar, and the particle separation phenomenon in the cyclone occurred from the critical diameter, and it was set as an important dependent variable. For developing a critical diameter prediction model based on machine learning and multiple regression methods, unsteady-Reynolds averaged Navier-Stokes analyzes according to shape dimensions were performed. The input design variables for predicting the critical diameter were selected as four geometry parameters that affect the turbulent flow inside the cyclone. As a result of comparing the model prediction performances, the machine learning (ML) model, which takes into account the critical diameter and the nonlinear relationship of cyclone design variables, showed a 32.5% improvement in R-square compared to multi linear regression (MLR). The proposed techniques have proven to be fast and practical tools for cyclone design.

In this work, a centrifugal classifier for separating lithium carbonate particles, used as a cathode material for lithium-ion batteries, was investigated. This work numerically evaluates the internal flow and particle separation performance of the centrifugal classifier. The complex turbulent flow field in the classifier is key to understanding particle motion. A Reynolds stress model, to describe air flow field, and a discrete phase model, to track particle motion, were applied to a numerical simulation. Design parameters such as mass flow rate and rotor speed were investigated, and a ring-shaped baffle, in particular, was designed to investigate the effects of flow and particle separation in the centrifugal classifier. The simple geometry of the baffle changes the movement direction of unseparated particles to the rotor cage region, and increases the local air velocity in the separation zone. The numerical analysis results were verified through a baffle experiment.

The generation of virus-mimetic nanoparticles has received much attention in developing a new vaccine for overcoming the limitations of current vaccines. Thus, a method, encompassing most viral features for their size, hydrophobic domain and antigen display, would represent a meaningful direction for the vaccine development. In the present study, a polymer-templated protein nanoball with direction oriented hemagglutinin1 on its surface (H1-NB) was prepared as a new influenza vaccine, exhibiting most of the viral features. Moreover, the concentrations of antigen on the particle surface were controlled, and its effect on immunogenicity was estimated by in vivo studies. Finally, H1-NB efficiently promoted H1-specific immune activation and cross-protective activities, which consequently prevented H1N1 infections in mice.

This paper challenges the fabrication of a thin film energy storage device on a flexible polymer substrate specifically by replacing most commonly used metal foil current collectors with coated current collectors. Mass‐manufacturable spray‐coating technology enables the fabrication of two different half‐cell electric double layer capacitors (EDLC) with a spray‐coated silver paste current collector and a Ni foil current collector. The larger specific capacitances of the half‐cell EDLC with the spray‐coated silver current collector are obtained as 103.86 F/g and 76.8 F/g for scan rates of 10 mV/s and 500 mV/s, respectively. Further, even though the half‐cell EDLC with the spray‐coated current collector is heavier than that with the Ni foil current collector, smaller Warburg impedance and contact resistance are characterized from Nyquist plots. For the applied voltages ranging from −0.5 V to 0.5 V, the spray‐coated thin film energy storage device exhibits a better performance.

Compact thermo-fluidic systems with complex and narrow gap flow passages, such as heat exchangers, are attractive for use in high energy efficiency applications. However, the narrow gap flow passage limits the experimental evaluations as a result of the size of the commercial sensors and the numerical evaluations of the full model due to massive computational meshes. This paper presents a new method to measure the distribution of the static pressure and wall temperature in the narrow gap. The 300 μm-thick stainless steel plate embedded with thermocouple temperature sensors and pressure tapping holes connected with microchannels is fabricated, and the temperature and pressure measurements are calibrated through comparisons with commercial sensors. In the experimental evaluation, the 23 flat plates are stacked with a narrow gap and the sensor-embedded plate is placed in the center. Then, the stacked plate thermo-fluidic system is installed in a wind tunnel. The measurement of the static pressure and wall temperature distributions in the narrow gap is performed successfully for the increased inlet flow velocities. The static pressures are measured at five different micro tapping holes, and the measurements exhibit a standard deviation of ±3.51 Pa for the same inlet velocity. Furthermore, the wall temperatures have good agreement with the reference temperatures measured at the inlet.

A recoverable self-cleaning surface is studied by coating the nanostructured core–shell microcapsules like a chestnut bur. The microcapsules encapsulate the hydrophobic agent so that when they are broken by mechanical damage, it is released and functions to recover the loss of the self-cleaning performance. The core–shell droplets encapsulating the hydrophobic agent are generated continuously by introducing immiscible fluids into a multi-coaxial microfluidic channel platform and cured by UV irradiation to be polymerized. The control of the size and shell thickness of the microcapsules, and the volume of the hydrophobic agent are examined. Also, the nanostructures on the surface of the microcapsules are obtained by the polyaniline process for additional increase in roughness. The critical breakage forces of the microcapsules are measured for increasing the shell thickness. Finally, the nanostructured microcapsule surface is fabricated on a glass substrate and the water contact angle is measured to determine the self-cleaning performance. Also, its recovery of the self-cleaning performance surface from the mechanical damage is demonstrated. The formation of the recoverable self-cleaning surface by coating enables to apply for a large scale and arbitrary curved surface.

This paper demonstrates a piezoresistive microcantilever biosensor for a potential of the early detection of HPV infection. Gold was patterned on the top surface of the microcantilever to define the sensing area. Then, a self-assembled monolayer (SAM) was coated on the gold surface for the attachment of a gold binding protein (GBP) which was functionally activated with carboxyl groups and amine groups to bind probe molecules such as antibodies, oligonucleotide probes, DNA, and proteins. The surface-activated magnetic beads were introduced to the sensing area with DNA fragments of the HPV-infected cells. The magnetic force was induced to the surface-activated magnetic beads bound with probe molecules and HPV DNA fragments by placing a permanent magnet. The electrical signal output measured from the piezoresistive sensor integrated in the microcantilever was amplified 1000 times compared with non-HPV solution with a high SN ratio.

To enhance the thermal efficiency of aero-engines, many works on numerical and experimental evaluation of cross corrugated heat exchangers for applications such as intercoolers and recuperators have been reported. However, numerical analyzes of unit cells or of corrugated flow passages in cross corrugated heat exchangers cannot be compared directly with experimental analyzes performed only at inlets and outlets. This paper presents results of the direct measurement of static pressure distribution in a corrugated flow passage: measurement was performed by embedding pressure tapping holes connected with microchannels into the corrugated plate, which had a thickness of 200 μm. Four corrugated plates were stacked and brazed to manufacture a real scale cross corrugated heat exchanger. The static pressure distribution was successfully measured inside the compact and complex heat exchanger. The friction factors for different Reynolds numbers were correlated for hydrodynamic performance evaluation. Finally, the friction factor was discussed with a consideration of the accuracy of the manufacturing of the cross corrugated heat exchanger.

Article history: This paper summarizes the results of an investigation into the environmental factors that have an indirect impact on parts quality, as well as those process variables and modeling information that have a direct impact. The effects of strength, surface hardness, roughness, and accuracy of shape, that is, qualities that users generally need to know, were evaluated with laminating direction experimentally. The 3D printing methods used in this experiment were fused deposition modeling (FDM), stereolithography apparatus (SLA), selective laser sintering (SLS), 3D printing (3DP) and laminated object manufacturing (LOM). The goal was to achieve a high standard of quality control and product quality by optimizing the fabrication process.

This paper presents methods for the formation of hollow microcapsules and microlenses using multiphase microdroplets. Microdroplets, which consist of a gas core and an organic phase shell, were generated at a single junction on a silicon device without surface treatment of the fluidic channels. Droplet, core and shell dimensions were controlled by varying the flow rates of each phase. When the organic solvent was released from the organic phase shell, the environmental conditions changed the shape of the solidified polymer shell to either a hollow capsule or a microlens. A uniform solvent release process produced polymeric capsules with nanoliter gas core volumes and a membrane thickness of approximately 3 μm. Alternatively physical rearrangement of the core and shell allowed for the formation of polymeric microlenses. On-demand formation of the polymer lenses in wells and through-holes polydimethylsiloxane (PDMS) structures was achieved. Optical properties of the lenses were controlled by changing the dimension of these structures.

This work presents the possibility of the hollow core nanoparticles to improve luminance in an organic light emitting diode device. The finite difference time domain simulation estimates the effect of the hollow core nanoparticles on the external quantum efficiency of the organic light emitting diode device. The efficiency depends on the size and the volume fraction of the hollow core nanoparticles in the polymer layer, together with the refractive index and the thickness of the polymer layer. It is shown that the hollow core nanoparticles dispersed in a polymer layer can enhance the external quantum efficiency by a factor of 2.5. This work also introduces a continuous production method of the hollow core nanoparticles by using the microfluidic self-assembly of amphiphilic polymers and the layer formation dispersed with them for the rigorous light scattering.

This paper presents a fabrication method of hollow polymeric nanocapsules (HPNCs). The HPNCs were examined to reduce light trapping in an organic light emitting diodes (OLED) device by increasing the refractive index contrast. They were continuously fabricated by the sequential process of self-assembly and photo-crosslinking of an amphiphilic block copolymer of SBR-b-PEGMA, poly(styrene-r-butadiene)-b-poly(poly(ethylene glycol) methyl ether methacrylate) in a flow-focusing microfluidic device. After the photo-crosslinking process, the produced HPNCs have a higher resistance to water and organic solvents, which is applicable to the fabrication process of optical devices. The morphology and hollow structure of the produced nanocapsules were determined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Also, their size control was examined by varying the ratio of inlet flow rates and the morphological difference was studied by changing the polymer concentration. The size was measured by dynamic light scattering (DLS). The refractive index of the layer with and without the HPNCs was measured, and a lower refractive index was obtained in the HPNCs-dispersed layer. In future work, the light extraction efficiency of the HPNCs-dispersed OLED will be examined.

This paper presents a 3D microfluidic perfusion cell culture system to mimic microenvironments. The perfusion system is integrated with bubble trapping reservoir, linear concentration generator and meandered microchannel mixer. The sudden expansion reservoir to prevent incoming of air bubbles by using buoyancy is examined. Also, for high throughput screening, the linear concentration gradient generator connected with efficient meandered channel mixer is developed. We evaluate the performance of key components numerically and experimentally. Finally, the 3D perfusion system with linear gradient of concentration of H2O2 examines cytotoxicity of muscle cells with Ewing's sarcoma.

This paper challenges the production of the protein nanoparticles using the conjugation of Ni2+ complexed nitrilotriacetic acid end-functionalized polystyrene (Ni-NTA-PS) and histidine tagged GFP (His-GFP) hybrid. The microfluidic synthesis of the protein nanoparticle with the advantages of a uniform size, a fast reaction, and a precise control of preparation conditions is examined. The self-assembly occurs on the interfacial surface of the multi-laminated laminar flow stably formed in the microchannel. The clogging of the produced protein nanoparticles on the channel surface is solved by adding a retarding inlet channel. The size and shape of the produced protein nanoparticles are measured by the analysis of transmission electron microscopy (TEM) and scanning electron microscope (SEM) images, and the attachment of the protein is visualized with a green fluorescent image. Future research includes the encapsulation of vaccines and the coating of antigens on the protein surface.

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.

This study presents a stable and controllable synthesis of fluorescent magnetic nanoparticles in a flow-through microchannel for the bimodal use of magnetic activated cells sorting and fluorescence-activated cell sorters. The La Mer process is carried out to synthesize magnetic nanoparticles using co-precipitation. Then, the magnetic nanoparticles are coated with conjugation of chitosan and fluorescent isothiocyanate with two different concentrations. The chemical composition of the magnetic nanoparticles is determined by comparing the standard X-ray diffraction peaks of Fe3O4, and their sizes are also examined by using field emission scanning electron microscopy and dynamic light scattering measurement. The magnetic property of saturation magnetization and coercive field is characterized in a vibrating sample magnetometer. Also, the possibility of external manipulation in the synthesis of the magnetic particles is demonstrated by separating the synthesized fluorescent magnetic nanoparticles into a non-reacting lamination flow. Finally, their fluorescence property is determined by measuring the fluorescence adsorption spectra and the photoluminescence emission spectra in UV–Vis spectroscopy.

In this paper, pH sensitive hydrogel microparticles (HMs) were synthesized in a microfluidic system with easy and controllable regulation of pH, and flow rate for drug delivery. The HMs originated from PEG derivative demonstrated low toxicity, which is an important characterization in pharmacy. Especially, an injectable multiamine hydrogel was synthesized by using condensation reaction process. The well-defined hydrogel droplets of water-in-oil was continuously generated in a cross microchannel. The size of the hydrogel droplets could be controlled by both the inlet flow rate and the pH of the pre-synthesized hydrogel in water. The hydrogel microparticles have been produced in a size ranging from 5 to 35 μm. By using MTT assay of in vitro cell viability, the hydrogel microparticles do not show cytotoxicity. The doxorubicin loaded in the hydrogel microparticles was released at low pH conditions. From in vitro testing of the pH effect on the release of a drug, HMs is a potential for drug delivery strategy to treat cancer. Also, hydrogel microparticles loaded with a drug can be applied to deliver it to human tissues with a low pH.

This paper presents a microfluidic synthesis of polymeric vesicles (PVs) by employing flow-induced self-assembly of polystyrene–block–poly(ethylene glycol) (PS-b-PEG) in a double flow-focusing microchannel (DFFM). The DFFM can solve the limitation of a large size distribution of produced PVs caused by clogging issues in general microchannel synthesis. By adding an attenuation layer between the polymer-dissolved solution and water, it is determined that rapid self-assembly of the polymers can be controlled. The hollow PVs are synthesized with a narrow size distribution and the size controllability is also examined for the ratios of the inlet flow rates and the polymer concentration. The produced PVs are characterized by using transmission electron microscopy, scanning electron microscopy and dynamic light scattering. It is newly visualized that the self-assembly occurs mostly in the attenuation layer owing to the diffusion through the interfaces of the five parallel laminar flow formed in the DFFM. This finding can provide a significant clue to understand the inflow-induced synthesis of the PVs in microchannels. Also, the uniform PVs can be applied to the development of drugs and biomedical researches.

The supercapacitors were fabricated using silver (Ag) nano paste and activated carbon paste on the polyimide (PI) film and 5% potassium polyacrylate (PAAK) was used for gel electrolyte. In this paper, the current collector film and the electrode film were fabricated using screen printing. The thickness of printed silver paste was 7.3 µm and the sheet resistance has the range of 5-7 mΩ/square. An activated carbon with a surface area of 1,968 m 2 /g, an electronic conducting agent (SUPER P, TIMCAL) and poly (4-vinylphenol) were mixed in 2-(2-buthoxyethoxy) ethyl acetate (BCA) with a ratio of 7:1:3 to fabricate the electrode paste. To analyze electrochemical characteristics, cyclic voltammetry was performed to evaluate the stability of the devices under the voltage range of -0.5-0.5 V. The calculated specific capacitances were 44.04 and 8.62 F/g for 10 and 500 mV/s scan rates, res

Flexible thin film super-capacitors with the silver paste current collector were printed and their electrochemical characteristics were investigated to apply for a low cost solution-based printing process. The silver paste current collector was printed on a flexible Polyethylene Telephtalate (PET) substrate and the activated carbon electrode was printed in a sequence by using a mature screen printing. In experimental evaluation, three silver pastes with different solid contents were prepared and compared because sheet resistance depended on the thickness of the current collector. By using the confocal image, the thickness of the printed electrode of the activated carbon was measured to be 27.8 microm. Cyclic voltammogram, the specific capacitance and impedence together with capacitance retension were examined to determine the performance of the printed super-capacitor. The highest specific capacitance of 53.05 F/g at a scan rate of 10 mV/s was obtained. The measurement results show that the printed super-capacitors with the silver paste current collector have a great potential to apply for wearable electronics and protable electronic devices.

This paper presents a multiamine supramolecular hydrogel (SH) modified SU-8 cantilever sensor. A chemical process to integrate the SH on the surface of SU-8 cantilever is developed to improve the stability and reusability of the functionalized cantilever sensor, instead of physical surface functionalization methods such as direct coating and self-assembly. The network structure of the SH is formed through a ring-opening and amine-substituted reaction in epoxy groups of the SU-8. The surface functionalization of the SU-8 cantilever is characterized by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The modified SU-8 cantilever sensor has been successfully applied for real-time measurement of metal ions concentration in aqueous solutions. Responses from the cantilever due to surface stress are induced by the axial coordination of ferric ions to amino groups of the SH and the chemical energy is converted into the mechanical energy which can be measured by a piezoresistive sensor. The concentration-dependent performance of the sensor is demonstrated and discussed, indicating a potential use of SH functionalized cantilever sensors.

This paper presents a practical flow-through method to separate anisole and ethyl phenylacetate, respectively, from a polystyrene mixture. The microfluidic separation uses different diffusive dynamics of the substances transverse to the lamination flow formed in a microchannel. The effect of inlet flow rates and ambient temperature on separation is examined. Additionally, the possibility of the separation of the light substance from the mixture with different molecular weight is shown numerically and experimentally. The separation efficiency is explained by the facts that the relaxation time depends on the inlet flow rate and that the diffusivity depends on the ambient temperature. This method can be applied to separate monomers from aggregates.

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 2microfluidic 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 700nm in diameter, we propose that nanoparticles of different sizes can be physically separated by time under a range of inlet volume flow rates. © 2013 The Japan Society of Applied Physics.

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)

In this study, we demonstrate the preparation of nanocapsules using the self-assembly of preformed polymers at the interface of a three-way controlled laminated stream flow in a microchannel. The production process occurs without the use of surfactants and allows the regulation of nanocapsule size with solvent recycling. Problems associated with nanocapsule attachment to the channel surface disturbing the lamination flow and producing nanocapsules of poor quality were overcome by altering the microchannel aspect ratio. The aspect ratio was altered by considering the mixing ratio and velocity distribution on the cross section along the microchannel. Modeling and practical experiment identified the aspect ratio of the microchannel of 1.6 as producing clear lamination flow. Ovalbumin-encapsulated nanocapsules were produced with a narrow size distribution of

This study introduces a new concept for a simple, efficient and cheap sensitivity amplification of a Quartz Crystal Microbalance (QCM) based immunosensor system for the detection of tumor necrosis factor-alpha (TNF-, TNF) by using an in-built magnetic system. The frequency shift due to the applied magnetic field was successfully observed on magnetic particles labeled detection antibodies, anti-human TNF-, which were bound to the immunologically captured TNF- on the gold coated quartz crystals. In the present system, the magnitude of frequency shift depends on both the strength of magnetic field and the amount of target antigen applied. Significant signal amplification was observed when the additional built-in residual stress generated by the modified magnetic particles under the magnetic field applied. Used in conjunction with a sandwich type non-competitive immunoassay format, the lower detection limit was calculated to be 25 and showed good linearity up to TNF- concentrations as high as 2.0 . The sensitivity, most importantly, was improved up to 4.3 times compared with the same QCM system which was used only an antigen-antibody binding without additional magnetic amplification.

This paper presents a fabrication method of microcapsules encapsulating fluorescent nanoparticles sensitive to an organic liquid, which is potentially applicable to the encapsulation of protein, cell and drug. It uses the supra-molecular self-assembly of a block copolymer at the interface of the stable and controllable droplets of water suspended with fluorescent nanoparticles and the polymer solved organic. The size and uniformity of the microcapsules were examined for the various polymer concentrations by using SEM image analysis. The maximum standard deviation of the produced microcapsules of less than 3.5% was obtained from the microcapsules produced from the same conditions. The inclusion of fluorescent nanoparticles was visualized in the fluorescence microscope and by using TEM image. It is shown that this fabrication method can provide the uniform size microcapsules with a higher inclusion.

This paper presents a novel direct fabrication method of the thin metal film RTD temperature sensor array on an arbitrary curved surface by using MEMS technology to measure a distributed temperature field up to without disturbing a fluid flow. In order to overcome the difficulty in the three dimensional photography of sensor patterning, the UV pre-irradiated photosensitive dry film resist technology has been developed newly. This method was applied to the fabrication of the temperature sensor array on a glass tube, which is arranged parallel and transverse to a main flow. Gold was used as a temperature sensing material. The resistance change was measured in a thermally controlled oven by increasing the environmental temperature. The linear increase in resistance change and a constant slope were obtained. Also, the sensitivity of each RTD temperature sensor was evaluated.

Recently, 3-dimensional in vitro cell cultures have gained much attention in biomedical sciences because of the closer relevance between in vitro cell cultures and in vivo environments. This paper presents a microfluidic perfusion 3D cell culture system with consistent control of long-term culture conditions to mimic an in vivo microenvironment. It consists of two sudden expansion reservoirs to trap incoming air bubbles, gradient generators to provide a linear concentration, and microchannel mixers. Specifically, the air bubbles disturb a flow in the microfluidic channel resulting in the instability of the perfusion cell culture conditions. For long-term stable operation, the sudden expansion reservoir is designed to trap air bubbles by using buoyancy before they enter the culture system. The performance of the developed microfluidic perfusion 3D cell culture system was examined experimentally and compared with analytical results. Finally, it was applied to test the cytotoxicity of cells infected with Ewing's sarcoma. Cell death was observed for different concentrations of H2O2. For future work, the developed microfluidic perfusion 3D cell culture system can be used to examine the behavior of cells treated with various drugs and concentrations for high-throughput drug screening.