This study examines the charge reduction characteristics of charged particles using a neutralizer to prevent accidents from electrostatic discharge and enhance process efficiency. The research measures the number of charges, elimination efficiency, and penetration rate under various voltage polarity conditions with a DC-type bipolar electrostatic eliminator. The results indicate that electrostatic neutralization is most effective under negative high voltage (-HV) conditions, while the mesh penetration rate increases and charge accumulation occurs under positive high voltage (+HV) conditions. Furthermore, partial charge neutralization is observed under both positive and negative high voltage (±HV) conditions due to the sequential emission of positive and negative ions. This study quantifies the mitigation of electrostatic charge using a neutralizer, offering insights for optimizing filtration systems and improving process stability. Future research will refine electrostatic control mechanisms by considering additional parameters such as particle size, material properties, and flow conditions.
Pinhole-free ionic conductors are critical to achieve optimal performance in thin film-solid oxide fuel cells (TF-SOFCs). However, nanoscale defects, especially pinholes, can induce current leakage and contribute to cell failure by creating electrical short circuits. This study introduced a novel methodology for detecting pinholes in yttria-stabilized zirconia (YSZ) thin-film solid oxide electrolytes. The approach utilized selective adsorption of silver (Ag) nanoparticles generated via a spark discharge generator (SDG). Analytical techniques, including focused ion beam (FIB), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), were employed to investigate interactions between Ag nanoparticles and nanoscale defects. Results showed that nanoparticle-based diagnostic methods were efficacious for defect characterization, offering a solution for enhancing the quality of thin-film electrolytes.
This study investigated the effectiveness of tap water application in reducing nano-sized wear particles at a wheel-rail contact interface and its impact on air quality at different train velocities. Airborne wear particles (AWPs) were simulated using a twin-disk rig at 500, 800, and 1,300 RPM. Mass concentration of nano-sized wear particles was measured using a fast mobility particle sizer (FMPS) at a sampling frequency of 1 Hz. To simulate various vehicle dynamics and contact conditions, the slip rate was incrementally increased from 0 to 3%. During wet conditions, water was applied at a rate of 7 L/min. PM0.1 and PM0.56 under dry and wet conditions were compared to evaluate the method’s effectiveness. The analysis showed that the tap water application method improved the air quality by reducing PM0.56 by at least 74% and PM0.1 by approximately 80%. In conclusion, the water application method can effectively improve air quality by reducing generation of nano-sized wear particles. The train velocity affected the generation of nano-sized wear particles under both conditions.
In this study, to improve the performance of a solid oxide fuel cell based on a porous metal support, a fuel cell using a multi-layered anode functional layer was fabricated and electrochemical performance analysis was performed. Surface and cross-sectional microstructures according to particle size control were confirmed through FE-SEM. The pore size of the multi-layer anode functional layer was gradually reduced compared to that of a single-structure anode functional layer. As a result, it was confirmed that the surface roughness was lower than that of the single structure. This led to a reduction in polarization resistance through smooth transmission of gas generated from the electrode. As a result, it was confirmed that electrochemical performance was improved by more than 1.25 times in fuel cells using a multi-layered anode functional layer compared to that with a single structure.
The effectiveness of applying tap water method to reduce the generation of nano-sized wear particles from wheel-rail contacts in the aspect of air quality was investigated. A twin-disk rig was utilized to simulate the generation of airborne wear particles resulting from wheel-rail contacts. Slip rates ranging from 0 to 3% were continuously generated to simulate various railway vehicle dynamics. Dry and tap water application conditions (7 L/min) were tested. The mass concentration of wear particles with sizes below 560 nm generated during tests was measured using a Fast Mobility Particle Sizer (FMPS). Particles measured in the slip zone (0 to 3%) were categorized into PM0.02, PM0.03, PM0.1, and PM0.56 for analysis. Results indicated a significant decrease in mass concentration of particles with sizes above 30 nm, while those with sizes below 30 nm showed an increase. Particle reduction rate was -217.2% for PM0.02, -58.5% for PM0.03, 84.5% for PM0.1, and 90.3% for PM0.56. It should be noted that a negative reduction rate indicates an increase in the amount of particle generation. This study demonstrates that the application of tap water is effective in improving air quality by reducing the generation of nano-sized wear particles overall.
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Measurement and Analysis of Air Quality Improvement Effects of Applying Water Methods at Various Train Velocities Using a Twin-disk Rig HyunWook Lee Journal of the Korean Society for Precision Engineering.2024; 41(10): 753. CrossRef
With the advancement of microstructure manufacturing technology, an array of functional surfaces based on micro/nano structures have been developed. Recently, there has been active research in the development of functional surfaces using composite materials that combine the properties of two different materials. One notable area of research is the creation of functional surfaces that utilize magnetic force to actuate microstructures. Typically, these surfaces are produced using a composite material that blends a flexible, easily deformable material with iron particles that respond to magnetic force. However, the inclusion of iron particles in the flexible material can increase its Young’s modulus, making it more challenging to effectively actuate the microstructures. To address this issue, our paper presents a fabrication method that allows for the effective actuation of microstructures by removing the residual layer of the composite material. This method enables the arrangement of iron particles at the end of the microstructure, maximizing the bending of the microstructure when magnetic force is applied. Furthermore, we conducted experiments to actuate microstructures with varying ratios of iron particles, confirming the effectiveness of this fabrication method.
This paper presents the development of a design optimization module for achieving the best performance of hydrostatic bearings. The design optimization module consists of two components: a bearing performance analysis module and an optimization module that utilizes optimization algorithms. Widely recognized global search methods, genetic algorithm (GA), and particle swarm optimization (PSO) algorithm, were employed as the optimization algorithms. The design optimization problem was defined for hydrostatic bearings. Optimization design processes were carried out to improve load capacity, stiffness, and flow rate. Subsequent experimental validation was conducted through the fabrication of a practical experimental setup. The design optimization model demonstrated superior performance compared to the initial model while satisfying design conditions and constraints. This confirms the practical applicability of the design optimization module developed in this study.
In this study, we propose a novel and simple fabrication method of the microfluidic device, with high-aspect-ratio (HAR) microchannel for microparticle separation under viscoelastic fluid flow. To fabricate the HAR (> 10) microfluidic device comprised of the Si channel and PDMS mold, basic MEMS processes such as photolithography, reactive ion etching and anisotropic wet etching of Si wafer were used, and then plasma bonding with mechanical alignment between the Si channel and PDMS mold was conducted. The width of the microchannels was determined by the difference between the Si channel width and the master width for the PDMS mold. On the other hand, the heights of the Si channel and PDMS mold could be controlled by the KOH etching time and spin-coating speed of SU-8, respectively. The HAR microfluidic device whose microchannel had 10 μm width and 100 μm height was successfully fabricated, and used to separate microparticles without other external forces. The effect on the particle focusing position and focusing width under viscoelastic fluid was investigated, depending on the flow rate and the microparticle size. It is expected that precise manipulation as well as high-throughput separation of microparticles, can be achieved using the microfluidic device with HAR microchannel.
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Process for the Fabrication of Nickel Material High Aspect-ratio Digital PCR Partition GeeHong Kim, HyungJun Lim, SoonGeun Kwon, Hak-Jong Choi Journal of the Korean Society for Precision Engineering.2024; 41(8): 663. CrossRef
Fabrication of a durable and strong nanopatterned mold insert using metal sheet and plate is important for molding of thermoplastic materials. Conventionally, the nickel stamper replicating a master pattern by electroforming process has been used for injection molding of nanotextured products such as Blu-ray media. However, a more facile and cheaper mold fabrication process is highly required for manufacturing of functional products based on nanostructured surface. In this study, zirconia nanoparticles were blended with UV curing polymer to fabricate a polymer nanocompositebased nanopattern mold. Compared to the cured pure Ormostamp, the modulus of elasticity of the nanocomposite filled with approximately 54 vol% of zirconia nanoparticles increased by 160 times. Additionally, the modulus of elasticity reached 197 ㎬ by thermal decomposition of the UV-Cured polymer and post-annealing at 800°C of the nanoparticle layer. The nanopatterns were formed on stainless steel sheet and block, and applied to hot embossing of the PMMA films and injection molding of the COC materials, respectively. No deterioration of the mold occurred during the hot embossing 30 times and the injection molding 600 shots. Nanoparticle-enhanced UV curing nanocomposites or post-heat treatment methods are cost-efficient and easy, because many molds can be manufactured from one master pattern.
In this paper, we propose acoustophoretic microfluidic devices with an acoustic transparent polymer wall using a simple and low-cost fabrication method followed by MEMS (Micro-Electromechanical Systems) processes. Generally, due to the acoustic standing wave between two opposing walls in microfluidic channel, the particle focusing lines are fixed according to the applied frequency. In the proposed device, however, it is possible to place the particle focusing lines in the arbitrary position within the fluidic domain through the optimized width of polymer wall. The PDMS (Polydimethylsiloxane) mold with thin layer was used as the sealing layer between the Si substrate and cover glass, as well as the decoupling layer between the acoustic boundary and fluidic boundary. The thickness of PDMS mold needed to be minimized to decrease the heating by the acoustic energy absorption of PDMS layer, which was successfully made using the spin-coating of PDMS and the UV tape transfer method. The acoustophoretic device with thin PDMS layer and optimized width of PDMS wall can be applied, for biotechnological applications such as the separation of blood cells and micro-particles.
Recent developments in additive manufacturing (AM) process have led us to fabricate many mechanical and electrical components or devices into complex geometries. Within existing AM processes, laser is widely used as an energy source to selectively sinter particles with a powder bed fusion (PBF) process or cure photopolymers with a vat photopolymerization (VPP) process. This study investigated the applicability of the SLS process for silver nanoparticles (Ag NPs)-photopolymer inks to fabricate micro-scale conductive patterns. With Ag NPs-photopolymer inks prepared with different mixture ratios and pasted on a polyethylene terephthalate (PET) substrate, a pulse width modulation (PWM) signal-controlled 405 nm laser was applied to these inks to selectively sinter and cure the Ag NPs and the photopolymer simultaneously. The final conductive patterns were obtained after a rinse in ethanol to remove un-sintered and un-cured regions of the inks. Microstructures, thickness profiles, pattern width, electrical resistance, and resistivity of the fabricated patterns were investigated by varying the PWM duty and the laser exposure time. Effects of different numbers of scan lines in the pattern and nanoparticle mixture ratios were also investigated. The proposed method is cost effective and easy with fast patterning capabilities. It will leverage practical advances in AM industries.
Quantitative metallographic analysis is significant in predicting the mechanical and physical properties of materials. This paper presents an alternate method to the approach used by Zhao, et al. (2016) in the paper “Metallographic Quantitative Analysis for GCr15 by Digital Image Process” in identifying carbide particles present within GCr15 bearing steel. GCr15 bearing steel is classified as a quality alloy; high carbon, chromium and manganese. This study quantitated the proportion of carbide particles in GCr15 bearing steel microstructure using the Mask Region-Based Convolution Neural Networks (Mask R-CNN) approach. The approach precisely located carbide particles, using bounding box indicators based on the concept Region of Interest (ROI) as used in the Mask R-CNN approach and masked the carbide particles within the ROIs. With this approach, we accurately located and masked more than 90% of the target particles, labeled and calculated the area and perimeter of each corresponding blob within the microstructure of GCr15.
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Region versus query based instance segmentation models: application to the estimation of aggregated TiO2 particles size distribution measured by SEM Paul Monchot, Loïc Coquelin, Nicolas Fischer Machine Learning: Science and Technology.2025; 6(2): 020502. CrossRef
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Nanoparticle laser sintering is one of the vital technologies in additive manufacturing. Numerous processes such as freeform surfaces or seamless parts have been proposed for the fabrication of complex components, however, the resolution and quality of the processes do not meet the standard necessary for practical applications. Therefore, selective laser sintering is used to fabricate electrode patterns in high-precision manufacturing field. Despite the various advantages, laser sintering process generates defects on the pattern with one of the major contributing factors being the Marangoni flow. In this study, the laser sintering process was used to determine the relationship between the nanoparticle blending conditions and the microstructure of the fabricated electrode pattern through the control of the nanoparticles density and laser characteristics such as power, pulse duration, and scan speed. As a result, the conditions for Marangoni flow were analyzed in relation to the concentration of the nanoparticle solution and laser irradiation parameters. More severe Marangoni flow was produced with the solution having a low weight percent of nanoparticles, while the width of the pattern was uniform when the pulsed laser was applied using a high peak power to achieve the same total amount of energy.
In this paper, we propose a simple and low-cost fabrication method for PMMA (Poly (Methyl Methacrylate)) acoustophoretic microfluidic chips using plasma-assisted bonding followed by MEMS (Microelectromechanical Systems) processes. A metal mold for replicating the PMMA polymer was fabricated using MEMS processes, and the microfluidic channel was imprinted on the PMMA polymer using a hot-embossing process. The closed fabricated microfluidic channel was achieved by means of the plasma-assisted bonding between the PMMA channel and the flat PMMA cover. The plasma treatment and hot-embossing conditions for PMMA-PMMA bonding were studied and evaluated. The particle separation test confirmed that the PMMA acoustophoretic microfluidic chips could be used. We expect the Si-based acoustophoretic microfluidic chip to be replaced by the presented polymer chip in such applications as blood or droplet separation.
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Fabrication of Acoustophoretic Device with Lateral Polymer Wall for Micro-Particle Separation Sungdong Kim, Su Jin Ji, Song-I Han, Arum Han, Young Hak Cho Journal of the Korean Society for Precision Engineering.2022; 39(5): 379. CrossRef
Microfluidic Chip Fabrication of Fused Silica Using Microgrinding Pyeong An Lee, Ui Seok Lee, Dae Bo Sim, Bo Hyun Kim Micromachines.2022; 14(1): 96. CrossRef
PMMA Thermal Bonding System Using Boiling Point Control Dong Jin Park, Taehyun Park Journal of the Korean Society for Precision Engineering.2021; 38(8): 613. CrossRef
Microchannel Fabrication on Glass Materials for Microfluidic Devices Jihong Hwang, Young Hak Cho, Min Soo Park, Bo Hyun Kim International Journal of Precision Engineering and Manufacturing.2019; 20(3): 479. CrossRef
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