Journal of the Korean Society for Precision Engineering

Electrochemical Impedance Analyses of ePTFE-reinforced Polymer Electrolyte Membrane-based PEMFC with Varying Thickness and Relative Humidity: Gyutae Park, Subin Jeong, Youngjae Cho, Junseo Youn, Jiwon Baek, Jooyoung Lim, Dongjin Kim, Taehyun Park; J. Korean Soc. Precis. Eng. 2025;42(11):901-907.
Published online November 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.052

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The polymer electrolyte membrane fuel cell (PEMFC) generates electrical energy through electrochemical reactions and is a key technology for sustainable energy. The electrolyte membrane significantly affects performance under varying conditions. This study examines the impact of membrane thickness and relative humidity (RH) on PEMFC performance using j-V curves and electrochemical impedance spectroscopy (EIS). Experiments were conducted with membrane thicknesses of 30, 15, and 5 μm under RH conditions of 100%-100% and 100%-0%. Under RH 100%-100%, performance improved as the membrane thickness decreased, with values of 954, 1050, and 1235 mW/cm² for the 30, 15, and 5 μm membranes, respectively. The 5 μm membrane demonstrated a 23% performance improvement over the 30 μm membrane. Under RH 100%-0%, performances were 422, 642, and 852 mW/cm², with degradation rates of 55.8%, 39.0%, and 32.1%. The 5 μm membrane exhibited the lowest degradation rate, indicating superior performance under low humidity. These results suggest that thinner membranes generally enhance performance and maintain efficiency even in dry conditions.

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Performance Study of Dielectric Elastomer Actuators with Varying Thickness of Carbon Nanotube Electrodes and Pre-stretch Ratios: Mingyu Kang, Joong-Hyun Park, Jong-An Choi, Jingu Jeong, Soonjae Pyo; J. Korean Soc. Precis. Eng. 2025;42(10):817-823.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.D.25.00004

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This study examines how two key design parameters—the pre-stretch ratio and the thickness of the carbon nanotube (CNT) electrode—affect the actuation performance of dielectric elastomer actuators (DEAs). DEA samples are created with varying pre-stretch levels (50% and 125%) and different amounts of CNT spray coating (4 and 8 mg), and their threshold voltages and areal strains are quantitatively assessed. The experimental results indicate that higher pre-stretch ratios result in lower threshold voltages and greater areal deformations, while increased CNT thickness typically reduces actuator deformation due to enhanced mechanical stiffness. The combination of a high pre-stretch ratio and low CNT loading demonstrates improved electro-mechanical responsiveness at moderate voltages. These findings underscore the interconnected effects of structural and electrode design on DEA performance, offering practical design guidelines for optimizing soft actuator systems. This research lays a solid foundation for future applications of DEAs in haptic interfaces, wearable actuators, and soft robotics.

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Recent Advances in Ionic Polymer-Metal Composite Sensors: Gwon Min Kim, Seong-Jun Jo, Jaehwan Kim; J. Korean Soc. Precis. Eng. 2025;42(5):367-379.
Published online May 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.012

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This paper extensively explores and analyzes the latest research trends in Ionic Polymer-Metal Composites (IPMC) sensors. IPMC sensors are known for their flexibility, lightness, and high responsiveness. They show great promise across different fields. They can respond sensitively to various stimuli such as mechanical deformation, humidity, and pressure, making them ideal for bio-responsive detection, health monitoring, and energy harvesting. This paper introduces actuation and sensing mechanisms of IPMCs, discusses their manufacturing processes, and explores how these processes can influence the responsiveness and stability of sensors. Moreover, through case studies of IPMC-based research that can perform self-sensing functions, it presents possibilities brought by the integration of sensors and actuators. This paper emphasizes the potential for research and development of IPMC sensors to expand into various industrial fields and explores ways to continuously improve the accuracy and reliability of sensors. IPMC-based sensors are expected to play a significant role in advancing medical devices and wearable technologies, thereby facilitating innovation in the field.

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Micro Hole Machining Characteristics of Glassy Carbon Using Electrical Discharge Machining (EDM): Jae Yeon Kim, Ji Hyo Lee, Bo Hyun Kim; J. Korean Soc. Precis. Eng. 2025;42(4):325-332.
Published online April 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.006

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Glassy carbon (GC) has superior properties such as high corrosion resistance, heat resistance, and low adhesion to glass materials in a glass molding process (GMP). In addition, the demand for GC molds is increasing in various industries that require high precision of glass parts. However, GC is a difficult-to-machine material with high hardness and brittleness. Electrical discharge machining (EDM) can machine GC regardless of its strength or hardness. In this study, tungsten carbide (WC-Co) electrode was fabricated by wire electrical discharge grinding (WEDG). Characteristics of EDM of micro holes on GC were then analyzed. As capacitance and voltage increased, material removal rate (MRR) increased while machining time tended to decrease. However, at low voltages, short circuit and secondary discharge occurred, which increased the electrode wear rate (EWR). As a result, a D-shaped electrode that could prevent short circuit and debris accumulation was fabricated and a micro hole array was machined.

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Manufacturing Process for Highly Stable Thermal Imprinting Transparent Electrode Using IPL Sintering: Yunseok Jang; J. Korean Soc. Precis. Eng. 2025;42(1):75-78.
Published online January 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.119

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This paper shows results of research on transparent electrode manufacturing processes using thermal imprinting and IPL technique. By using an IPL process instead of the existing heat sintering process, the sheet resistance value was reduced to about 1/ 10. Additionally, sintering time could be reduced from 1 hour to 1 ms. As a result of measuring the transmittance to determine the excellence of the transparent electrode produced in this way, it was confirmed that it had a high transmittance of 94.4% compared to the substrate with a very high bending stability compared to the existing ITO transparent electrode. These results show that the transparent electrode manufacturing method proposed in this study is very useful.

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2-step CMP Strategy for Dishing Control of TGV Interposers: Seunghun Jeong, Yeongil Shin, Jongmin Jeong, Seonho Jeong, Haedo Jeong; J. Korean Soc. Precis. Eng. 2024;41(6):467-472.
Published online June 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.027

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Chemical mechanical planarization (CMP) is an essential polishing process in semiconductor manufacturing. Advances in memory technology, including increased capacity and performance, have increased the importance of electronic packaging. In heterogeneous integration, the interposer acts as an important intermediary between the logic die and the substrate, solving numerous I/O bump problems in high-bandwidth memory (HBM) and logic chips. Traditionally, board-to-memory connections were made through wire bonding, which required additional space for wire connections and introduced latency due to extended signal transmission paths. A through-type approach has emerged as a solution that can significantly reduce waiting time and installation space by improving space efficiency and enabling vertical connections without extending wiring. Due to these new approaches, the importance of CMP is reemerging. Implementation of this important process requires precise control of the CMP dishing/protrusion of bonding surfaces. Improper selection of Cu pad dishing/protrusion can cause problems such as increased RC delay time and signal short circuit in the wiring. In this paper, we proposed a strategy to control dishing using CMP, especially for Through-glass-via (TGV).

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Study of Droplet Characteristics of Electrospray Coating Method as a Function of Ring Electrode Parameters: Ji Yeop Kim, Mun Hee Lee, Jun Yeop Kim, Jung Goo Hong; J. Korean Soc. Precis. Eng. 2024;41(2):153-159.
Published online February 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.140

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Among chemical coating methods, deposition using electrostatic spraying is commonly employed in coating processes to control the deposition rate, thickness, and properties of the formed materials. In this study, we considered the following variables: ring electrode, ring diameter (RD), ring voltage (RV), and nozzle-ring distance (NTR). Through experiments, we determined the atomization mode applied voltage, Sauter mean diameter (SMD), and SMD standard deviation of the nozzle. Additionally, we derived the voltage intensity and electric field along the axial direction using ANSYS maxwell to identify the optimal ring electrode atomization conditions.

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A Study of Effects of the Repetition of Assembly and the Addition of Activation on Electrochemical Characteristics of PEMFCs: Ji Woong Jeon, Gye Eun Jang, Young Jo Lee, Dong Kun Song, Ho Jun Yoo, Seung Hyeok Hong, Jung Soo Kim, Ye Rim Kwon, Da Hye Geum, Gu Young Cho; J. Korean Soc. Precis. Eng. 2023;40(11):867-872.
Published online November 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.026

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In this study, the effects of repetition of assembly and disassembly of polymer electrolyte membrane fuel cells on electrochemical performance were systematically investigated. Additionally, the effects of additional activation on polymer electrolyte membrane fuel cells were evaluated. All fuel cells were measured every three days. For the disassembled polymer electrolyte membrane fuel cells, membrane electrode assemblies were stored in a vacuum desiccator. For the maintained assembly, fuel cells were stored at room temperature. The performance and electrochemical characteristics of the fuel cell were analyzed by electrochemical impedance spectroscopy. As a result, the addition of activation to maintained assembly fuel cells showed the best performance among fuel cells with other assembly and activation conditions. Repetition of assembly and disassembly, as well as insufficient activation, caused degradation of the performance of fuel cells.

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Fabrication of Transparent Electrode based on Metallic Nanofiber Network via Combined Heat Treatment: Na Kyoung Kim, So Eun Kim, Doyeon Im, Seung Mi Hong, Taechang An, Geon Hwee Kim; J. Korean Soc. Precis. Eng. 2023;40(10):813-819.
Published online October 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.075

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With the increasing interest in research on the development of next-generation technologies such as flexible smartphones, displays, and wearable devices, interest in the development of materials and processes for transparent electrodes constituting them is also increasing. The most widely used material for manufacturing transparent devices is indium tin oxide (ITO). However, ITO is scarce, expensive, and brittle, making it is essential to replace it with new materials. In this study, we successfully fabricated a transparent electrode by electrospinning polyvinylpyrrolidone (PVP) and copper electroless deposition on the polyimide film. Especially, this study suggests a new combined heat treatment that uses both the hot plate and the convection oven. Through the combined heat treatment, the junctions between the nanofibers overlapped removed consequently reducing contact resistance. The mechanical stability of the fabricated electrode was evaluated by using a highly repeated bending test. Also, through the tape-peeling test, we confirmed that the adhesive strength of the electrode was high. This method can be applied to various polymer-based, substrate which are vulnerable to annealing process.

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Design of Compact Multiple-test Machine for Evaluation of Electrical and Mechanical Properties of Flexible Thin Electrode
Ji Hong Lee, Na Kyoung Kim, Taegyun Kim, Mun Jeong Choi, Seung Min Kang, Jungho Cho, Harim Son, Kanghyun Kim, Geon Hwee Kim
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(2): 95. CrossRef

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A Study on Electrochemical Resistance Change through the Pressurization Process of MEA for PEMFC: Ye Rim Kwon, Dong Kun Song, Ho Jun Yoo, Gye Eun Jang, Young Jo Lee, Jung Soo Kim, Ji Woong Jeon, Da hae Guem, Gu Young Cho; J. Korean Soc. Precis. Eng. 2023;40(7):539-544.
Published online July 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.150

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In this study, the electrochemical characteristics of fuel cell were evaluated after applying a compressive load to the activation area of membrane electrode assembly (MEA) in polymer electrolyte membrane fuel cells. The effects of the pressed area under the compressive load were systematically investigated using polarization curves and electrochemical impedance spectroscopies (EIS) of the fuel cell. Interestingly, the performance of the fuel cell was improved as the pressed area of the MEA was increased from 25.2% to 100% of the active area. In addition, the increased pressed area led to a decrease in the ohmic resistance and the activation resistance of fuel cells.

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Laser EDM Hybrid Micro Machining of CFRP: Do Kwan Chung, Chan Ho Han, Yu Jin Choi, Jun Seo Park; J. Korean Soc. Precis. Eng. 2023;40(2):99-104.
Published online February 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.115

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CFRP (Carbon Fiber Reinforced Plastic) is a composite material formed using carbon fibers and epoxy resin matrices. It has low productivity and suffers from machining defects during precision machining. Laser machining of CFRP is associated with the problem of heat damage to the epoxy resin. EDM of CFRP can process various shapes with a shaped tool, however it has a lower material removal rate compared to laser, and the non-conductive epoxy resin layer on the surface must be removed before EDM processing. In this study, we have proposed a laser EDM hybrid machining in which CFRP was pre-processed with a laser and then post-processed by EDM. The laser pre-processing conditions were selected by adjusting the laser power and the number of repetitions to minimize thermal damage. According to EDM conditions, the size of the thermal damage area occurring in the epoxy resin, the change in the side gap, and the change in the processing time were investigated. Using the hybrid processing, micro-holes with a diameter of 150 μm were machined, and square-shaped micro-holes were also machined. To improve productivity, a multi-tool capable of processing four square shapes was manufactured, and multi-processing was performed.

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Fabrication of micro holes with confined pitting corrosion by laser and electrochemical machining: Pitting corrosion formation mechanisms and protection method
Jian Yang, Yufeng Wang, Yong Yang, Yunfeng Liu, Wenwu Zhang
Journal of Materials Processing Technology.2025; 335: 118677. CrossRef
Laser Drilling of Micro-Hole Array on CFRP Using Nanosecond Pulsed Fiber Laser
Do Kwan Chung
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(5): 92. CrossRef

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EDM Using Wire Electrical Discharge Milling Electrode: Do Kwan Chung; J. Korean Soc. Precis. Eng. 2022;39(1):21-27.
Published online January 1, 2022; DOI: https://doi.org/10.7736/JKSPE.021.107

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In this study, a wire electrical discharge milling electrode was developed, and electric discharge machining characteristics were studied by using the electrode. The wire electrical discharge milling electrode is a form, in which the wire is conveyed by using a cylindrical rod with a hemispherical end as a guide, and it also rotates in one direction around the guide axis. If the wire electrical discharge milling electrode is used in electrical discharge machining (EDM), there is no need to consider electrode wear compensation. The EDM characteristics according to capacitance of the RC circuit and the rotational speed of the wire electrical discharge milling electrode were examined. The machining conditions were selected, and a hemispherical shape with good shape accuracy and fine surface finish was fabricated in two stages of roughing and finishing. By applying the wire electrical discharge milling electrode to the electric discharge milling process, straight and curved shapes were successfully machined.

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Experimental study on the wire electrical discharge machining of PCD with different grain sizes
Kechuang Zhang, Laifa Zhu, Zhongwei Chen, Jianyun Shen, Xuefeng Zhao, Xian Wu
Diamond and Related Materials.2025; 155: 112331. CrossRef

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The Effect of Thickness of Electrodes on Edge Quality in Laser Cutting of Electrodes: Dongkyu Park, Dongkyoung Lee; J. Korean Soc. Precis. Eng. 2021;38(2):97-101.
Published online February 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.095

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Many countries are trying to overcome global warming due to greenhouse gas emissions, such as CO₂. In particular, the regulation on CO₂ emissions of internal combustion engine vehicles has become strictly important. Thus, the automobile companies are putting more effort for improving the manufacturing of the battery, which is the main power supply of electrical vehicles. In the electrode cutting process, laser cutting has been actively discussed to solve problems originating from the conventional electrode cutting processes. However, there is a lack of research considering the effect of thickness of the active material on laser cutting. In this paper, the effect of thickness of the active material on laser cutting of electrodes is analyzed. First, the cut electrodes are observed through a scanning electron microscope (SEM). Next, the kerf width and clearance width of the electrodes are measured and compared at the same laser parameter. The kerf width and clearance width of relatively thick electrodes are narrowly formed. Finally, the cutting quality of the electrode is compared. A uniform cut edge is observed as the scanning speed increases.

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Comparison of laser processability for LiFePO4 cathode material with nanosecond and femtosecond laser
Jaegeun Shin, Juhee Yang, Dongkyoung Lee
Journal of Science: Advanced Materials and Devices.2024; 9(3): 100753. CrossRef

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Robot Application of Electroadhesion Pads with Dual Insulation: Yongjin Jeong, Kihyun Kim, Heon Huh; J. Korean Soc. Precis. Eng. 2020;37(10):743-750.
Published online October 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.055

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Electroadhesion has many advantages over other adhesion methods such as pneumatic, hydraulic, magnet, etc. The applications include electrostatic chucks and grippers. Recently, electroadhesion has been adopted for robots working in limited environments. The electro-adhesive climbing robots can be used for inspection and exploration in a variety of conditions. The electroadhesion robots often have a limited adhesion force. In this paper, we propose a novel pad structure improving the adhesion force. An additional insulating layer prevents the discharge from the high voltage application and increases the adhesion force per unit area. The electroadhesion forces were compared for the different pad materials and electrode structures and were partly confirmed as the theoretical model. The proposed pad was used for a climbing robot wheel. The climbing robot weighs approximately 3 kg and can manage to 3 kg of extra weight on metal walls. Experiments showed a 90-degree gradability for the climbing robot.

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Optimal Design of the Electroadhesion Pad with a Dual-Insulating Layer for Climbing Robots
Yong-Jin Jeong, Tae-Hwa Hong, Hak-Jun Lee, Kihyun Kim
Actuators.2022; 11(2): 36. CrossRef

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Patterning of Functional Nanoparticles Using Solution-based Selective Surface Treatment Process: Chang-Goo Park, Jun-Ho Jeong, Jun-Hyuk Choi, Jihye Lee, Joo-Yun Jung, Sohee Jeon, Eungsug Lee, Dae-Geun Choi; J. Korean Soc. Precis. Eng. 2019;36(11):1051-1057.
Published online November 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.11.1051

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The purpose of this study was to develop a selective patterning process with functional nanoparticles, using the selective hydrophobic treatment which can give surface energy differences. It is important to selectively pattern the nanoparticles in solution, to the desired site in a variety of fields such as transparent electrodes, displays, and bio-sensors. Selective hydrophobic treatment can reduce the additional post processes such as cleaning to remove particles unwanted position, which is a drawback of the existing solution process. Various patterns with sub-micron size that can’t be achieved with other solution processes could be fabricated by nanoimprint lithography, selective surface treatment, and a solution coating process. The transparent conductive electrode (TCE) using silver mesh patterns on the flexible substrate created from our study showed 24 Ω of sheet resistance and more than 82% transmittance. To verify the possibility of nano-patterning of various materials, quantum dot (QD) was also patterned by selectively filling. Selective surface treatment technology has significantly improved the filling process of nanoparticles into fine patterns less than 1 μm wide.