Journal of the Korean Society for Precision Engineering

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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Suppression of Interfacial Side Reactions and Performance Enhancement of NCA Cathodes via LNO Deposition Using Particle ALD: Min-ji Kim, In-suk Song, Hyo-jun Ahn, Sun-min Kim, Young-Beom Kim; J. Korean Soc. Precis. Eng. 2025;42(10):851-859.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.025

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Improving the interfacial stability between cathode active material (CAM) and solid electrolyte (SE) is essential for enhancing the performance and durability of all-solid-state batteries (ASSBs). One promising method to achieve this is through surface coating with a chemically stable ion conductor, which helps suppress interfacial side reactions and improve long-term cycling stability. In this study, we deposited a uniform LiNbO3 (LNO) protective layer on NCA using particle atomic layer deposition (Particle ALD). This technique utilizes a self-limiting growth mechanism to ensure precise thickness control. We characterized the structural and chemical properties of the coated CAM with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), confirming the successful formation of a uniform LNO layer. Electrochemical evaluations revealed that LNO@NCA exhibited significantly improved capacity retention, maintaining 68.1% after 50 cycles at a 1C rate, compared to just 56.5% for the uncoated sample. This enhancement is attributed to the LNO layer's effectiveness in mitigating electrochemical side reactions. These findings demonstrate that Particle ALD-derived LNO coatings are an effective strategy for stabilizing CAM|SE interfaces and extending the cycle life of high-energy ASSBs.

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Thermal Fatigue Life Evaluation of EB-PVD TBC Using Newly Developed Small-scale Burner Rig: Soo Park, Jun-Young Kim, Jun-Young Kim, Seoung-Ju Kim, Chang-Sung Seok; J. Korean Soc. Precis. Eng. 2025;42(1):65-73.
Published online January 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.110

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In this study, the effect of flow rate ratio (R) and total flow rate (Q) on the surface temperature of thermal barrier coatings (TBC) was investigated using a newly developed small-scale methane-oxygen burner rig. Subsequently, the failure mode of electron beam physical vapor deposition (EB-PVD) TBC was examined, and the relationship between surface temperature and coating life was established. The surface temperature of the TBC was found to be strongly dependent on both the flow rate ratio and the total flow rate. Specifically, surface temperature exhibited a proportional relationship with total flow rate, while it showed an inverse relationship with flow rate ratio. The failure mode of the EB-PVD TBC involved a gradual increase in delamination from the rim to the center of the coin-shaped specimen, and this failure mode was found to be independent of surface temperature. Additionally, it was determined that the surface temperature of EB-PVD TBC has a perfectly inverse linear relationship with coating life. This finding implies that the derived linear regression line from the burner rig test can be directly used to predict coating life for any untested surface .temperature.

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Development of a Vertical Burner Rig Using Methane Flame: Soo Park, Dae-Jin Kim, Jun-Young Kim, Seong-Ju Kim, Ki-Yong Lee, Jeong-Min Kim, Hyung-Ick Kim, Chang-Sung Seok; J. Korean Soc. Precis. Eng. 2024;41(8):653-661.
Published online August 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.053

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In this study, we developed a new vertical thermal gradient rig that uses methane-oxygen fuel. We conducted thermal gradient testing on a thermal barrier coating system, with a flame temperature of 1,900℃. Our results showed that the maximum surface temperature reached 1,065℃, while the temperature difference between the surface temperature and the temperature of the middle substrate (ΔT) was 70oC. Using the same torch as in this study, our finding suggest that the total flow rate of the flame should be above 12.4 LPM, and the gun distance should be less than 8 cm, to simulate a surface temperature of 1,300℃, while keeping the substrate temperature below 1,000℃. This will ensure that the flame is wide enough to cover the entire surface area of the thermal barrier coating.

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Thermal Fatigue Life Evaluation of EB-PVD TBC Using Newly Developed Small-scale Burner Rig
Soo Park, Dae-Jin Kim, Jun-Young Kim, Seoung-Ju Kim, Chang-Sung Seok
Journal of the Korean Society for Precision Engineering.2025; 42(1): 65. CrossRef

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Machinability Improvements of Soda-lime Glass Using Various Surface Coatings: Ji Hwan Kim, Byoung Ho Yun, Suk Bum Kwon, Sangkee Min, Hae-Sung Yoon; J. Korean Soc. Precis. Eng. 2023;40(10):839-845.
Published online October 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.048

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Advanced engineering ceramics have been highlighted mainly owing to their superior hardness, corrosion/wear resistance, and thermal insulation performances. However, they are usually very difficult-to-cut because of their high brittleness. In light of this, ultra-precision machining has been studied to perform ductile-regime cutting in the machining of ceramics. Ductile-regime cutting can feature a smoother surface, and lower subsurface damage as the dominant material response during cutting showed ductile behavior. Researchers have investigated promoting ductileregime cutting to improve the machinability of ceramics. In this study, various coating materials were applied to the workpiece surface, and their effects on machinability improvements were explored. A total of 6 surface coatings and lubricants were applied to soda-lime glass. The critical depth of cut (CDC), the depth where the ductile-brittle transition (DBT) occurred, was increased in all coatings and lubricants, with an improved ductile cutting regime. Experimental results showed that solid coatings were more effective than liquid lubricants in enhancing the ductile cutting regime. It was thought that solid coatings induced an additional downward force by resisting material deformation and chip evacuation, thus contributing to suppression of crack opening. It is expected that this research can contribute to the machinability improvements of brittle materials.

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Superhydrophilic Modification of a Polypropylene Depth Filter for Efficient Oil–water Separation: Hong Ryul Park, Jeong-Won Lee, Seongmin Kim, Kihwan Kim, Yeonggeun Kim, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2023;40(8):599-605.
Published online August 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.032

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Purification of water through oil–water separation is essential for preserving the ecosystem and protecting human health. Although a conventional polypropylene depth filter can effectively purify water, modifying the wettability of a filter for oil–water separation is difficult owing to its low reactivity. In this study, we developed a superhydrophilic polypropylene filter with a hydrogel layer that could enable effective oil–water separation by using plasma treatment and dip coating, which enabled an even distribution of the coating solution across the filter. The fabricated filter was superhydrophilic with a water contact angle of 0o. It showed a high repulsive force with oil in water with an underwater oil contact angle of 142.9o. When such filter was applied to an oil–water separation device, it effectively purified water with low oil content (< 15 ppm) at a flow rate of 300 mL/min. These results demonstrate potential applications of such filters in areas such as wastewater treatment and oil spill cleanup.

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Practical Gravimetric Flow Rate Measurement Method for Slot-Die Coating Uniformity Evaluation: Kyung-Taek Yoon, Jeong-Hyun Bae, Young-Man Choi; J. Korean Soc. Precis. Eng. 2023;40(2):105-111.
Published online February 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.117

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Slot-die coating is a method of coating a wide layer of thin film on a substrate. It has the advantages of large-area coating with high reproducibility and uniform thickness. For this reason, it has been widely applied in various industrial manufacturing fields. To secure higher coating uniformity under various coating conditions, estimating and controlling the flow rate of the coating solution discharged to the substrate is crucial. In this study, a practical gravimetric flow rate measurement method for slot-die coating uniformity evaluation has been introduced. The gravimetric method is a technique for accurately and quickly estimating the flow rate through the mass change over time using a precision weighing balance. We analyzed the measurement principle and errors caused by fluid mechanics such as hydrodynamic force or capillary force. The dynamic properties based on fluid viscosity were also evaluated for flow rates from 5 to 50 μL/s. The repeatability of the fabricated measurement system was ~1.5 μL/s. Finally, it was confirmed that the settling time for high-viscosity fluid could be advanced by 56.4% through multi-step feedforward control.

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Precision Measurement and Control of Flow Rate for Coating Uniformity in Variable Slot Die Coating
Yeeun Bae, Kyung-Taek Yoon, Hyun-Ho Lee, Moongu Lee, Hyun-Jung Kim, Young-Man Choi
Journal of the Korean Society of Manufacturing Technology Engineers.2023; 32(5): 267. CrossRef

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Unconventional Additive Manufacturing for Multiscale Ceramic Structures: Hyo Jun Lee, Young Tae Cho, Seok Kim; J. Korean Soc. Precis. Eng. 2021;38(9):639-650.
Published online September 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.072

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Nature-inspired architected materials have been widely used to achieve efficient structural materials by harnessing their cellular and hierarchical structures. For example, biological materials observed in bone, shell, nacre, and wood contain constituents, ranging from nanometers to centimeters, arranged in an ordered hierarchy. Because of their composited structures that contain micro and nanoscale building blocks arranged in an ordered hierarchy and the material size effect in the mechanical strength of nano-sized solids, bioceramic materials are mechanically robust and lightweight. The design principles offered by hard biological materials of multiscale composite structures can assist in the creation of advanced ceramic architectures. In addition, the evolution of additive manufacturing technologies has enabled the fabrication of materials with intricate cellular architected materials. In this review, we discussed advanced additive manufacturing for the fabrication of nature-inspired multiscale ceramic structures by combining conformal thin-film coating technique with conventional additive manufacturing methods.

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SEM Image Quality Improvement and MTF Measurement Technique for Image Quality Evaluation Using Convolutional Neural Network
Chan Ki Kim, Eung Chang Lee, Joong Bae Kim, Jinsung Rho
Journal of the Korean Society for Precision Engineering.2023; 40(4): 275. CrossRef

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Analysis of Compression Behavior on 3D Microlattices Coated with Metal Nanoparticle-Polymer Composites: Seo Rim Park, Do Hyeog Kim, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2021;38(9):631-637.
Published online September 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.071

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Microlattice is well known as an efficient structure having a low density which maintains mechanical properties, so microlattice is being applied to the structural design of lightweight material in many industrial fields. In this study, we proposed a core-shell microlattice structure by the conformal coating of a metal nanoparticle-polymer composite in order to enhance the mechanical properties of polymeric microlattice printed by light-based 3D printing method. Polymeric architected microlattice was fabricated using digital light printing, which enabled the printing of complex structures with good surface smoothness. Then, the polymeric microlattice was conformally coated with aluminum nanoparticle-polymer composites. To investigate the effect of the metal nanoparticle-polymer composite coating on the mechanical properties of the microlattice, we studied the compressive behavior of cubic and octet-truss microlattices. As a result, we confirmed that both compressive strength and toughness of the two types of microlattices were effectively increased by coating with aluminum nanoparticle-polymer composites.

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Robust catalyst 3D microarchitectures by digital light printing with ceramic particle–polymer composites
Do Hyeog Kim, Sang-Hoon Nam, Gina Han, Seo Rim Park, Gwang Ho Jeong, Seok Kim, Young Tae Cho, Nicholas Xuanlai Fang
APL Materials.2024;[Epub] CrossRef
Study on Mechanical Properties of MWCNT Reinforced Photocurable Urethane Acrylate for Additive Manufacturing
Hyunjun Jo, Bum-Joo Lee
Journal of the Korean Society for Precision Engineering.2024; 41(3): 199. CrossRef

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A Study on Enhanced Uniformity of Artificial Flexible Vascular Grafts Fabricated by Dip-Coating Process: Yeong Seo Kim, Seung Mun Lee, Yu Seok Kim, Da Hye Yoo, Suk-Hee Park; J. Korean Soc. Precis. Eng. 2021;38(5):365-371.
Published online May 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.009

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Three-dimensional (3-D) printing, with its capability for producing arbitrary shapes, has shown great potential for usage in patient-specific tissue engineering. However, if artificial tissues are fabricated directly through typical 3-D printing processes, the mechanical properties, particularly for softness or flexibility, significantly differ from those of natural tissues, resulting in inappropriate side effects during surgeries using vascular grafts. However, this can be overcome through the indirect 3-D printing of templates created with a thin-film formation process, such as dip coating. Dip coating is performed in two steps, including dipping/withdrawing a target base template from a polymer solution, and then drying the solvent into a solid thin film on the template. However, it is difficult to form a uniform layer on the arbitrary template because the gravitational flow of the coated solution disturbs the uniformity of the template as the solvent is drying. Therefore, we minimized the flow around the template after dip coating by rapidly removing the solvent removal by dipping the solution-coated template into ethanol. This reduced the solvent removal time and increased the viscosity of the coated solution, thereby alleviating the gravitational flow of the coated solution, and allowing us to successfully fabricate flexible vascular grafts.

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Fabrication of Long Porous Vascular Grafts Using Nozzle-Transfer Dip-Coating System
Seung-Mun Lee, Yeong-Seo Kim, Suk-Hee Park
Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(7): 11. CrossRef
A Study on the Mechanical Properties of a Biocompatible Conduit Structure based on Electrospun Fibers
Jeong Hwa Kim, Jaewon Choi, Yong Jun Yoon, Young Hun Jeong
Journal of the Korean Society for Precision Engineering.2022; 39(10): 739. CrossRef

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Study on Optimization of Meniscus Solution Shearing Coating Process for Fabrication of Large Area Perovskite Solar Cell: Kyeong Mi Kim, Hyun Ah Lee, Dong Soo Kim; J. Korean Soc. Precis. Eng. 2020;37(6):443-449.
Published online June 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.164

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Among the various next-generation solar cells, a perovskite solar cell can solve the economic problem because it can perform the low temperature solution process and the material is inexpensive. Photovoltaic conversion efficiency is comparable to silicon solar cells and thin-film solar cells. However, to commercialize the perovskite solar cells, there are many problems to be resolved, such as stability, upscaling, and efficiency. Thus, in this study, perovskite crystallization experiments were conducted according to the coating conditions such as the coating speed of the meniscus solution sheared coating process, and large-area perovskite solar cells with p-i-n structures were fabricated. Perovskite crystallization is one of the crucial factors that determine the efficiency of solar cells, and it is an integral process condition for manufacturing large-area perovskite solar cells.

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A Study on Crystallization of Perovskite Using a High-Speed Meniscus Solution Shearing Coating Visualization Device
I-Ji Kim, Hyun Ah Lee, Dong Soo Kim
Journal of the Korean Society for Precision Engineering.2021; 38(12): 965. CrossRef

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Improvement of Electrolyte Layer Coating Quality Using Statistical Optimization: Seongyong Kim, Changwoo Lee; J. Korean Soc. Precis. Eng. 2019;36(2):149-153.
Published online February 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.2.149

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Slot-die coating technique has become a subject of interest owing to its mass and large area production characteristics. To date, numerous research on the fluid dynamics of coated solution and experimental decision of the coating conditions to improve quality of coated layer have been conducted. However, few studies have been done on the optimization of slot-die coater geometry owing to the high cost associated with its fabrication. In this study, we optimize the geometry of the slotdie coater using computational fluid dynamics. We used a statistical optimization technique (Box-Behnken design). In the optimization process, we determined the significant factors that affect the velocity variation of coated fluid in the transverse direction. An optimal geometry was derived using a desirability test which is generally used to evaluate the suitability of a selected geometry value based on the maximization of the velocity uniformity. Experimental results presenting the uniformity of the coated layer in the transverse direction improved from 4.7% to 1.4%.

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Performance Evaluation and Analysis on Protective Coating Applied to HPT Heat Shield of GT24 Gas Turbine: Junghan Yun, Jeong-Min Lee, Chang-Sung Seok, Sukhwan Kwon, Byoungkwan Yun, Byungmoon Chang; J. Korean Soc. Precis. Eng. 2019;36(1):53-57.
Published online January 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.1.53

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Gas turbine, the core equipment of the power plant, is capable of rapid starting operation and has less carbon dioxide emission than coal power plant. So it has the advantage of being eco- friendly. In order to increase the efficiency of these gas turbines, the turbine inlet temperature has steadily increased and to ensure the safety of the gas turbine, means for protecting parts exposed to high temperatures have also been developed. Protective coating technology is one of them, which plays the role of lowering the temperature of the base metal and preventing oxidation and corrosion. In this paper, thermal fatigue test simulating the operation environment was conducted using the Amdry 9951 protective coating powder applied to the HPT Heat Shield for the Alstom GT 24 gas turbine and the performance before and after the thermal fatigue test was evaluated and examined by adhesive strength test and SEM (EDS) analysis.

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A Review - Productivity Enhancements of Micro/Nano Patterning Methods -: Moon Kyu Kwak; J. Korean Soc. Precis. Eng. 2018;35(11):1019-1026.
Published online November 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.11.1019

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The purpose of this review paper is to highlight recent efforts and achievements to realize high productivity of micro/nano structure fabrication processes and feasible applications. Due to development in micro/nano fabrication processes, demands on micro/nano related applications are increasing rapidly in various fields. To meet requirements, fabrication process must have high production yield and be automated. Also, fabricated micro/nano structures are expressed on large area substrate. So, it is timely and appropriate to move forward to a new epoch by researching more robust and high throughput fabrication methods, large area fabrication techniques, and new applications. In this review paper, we present a series of recent achievements to overcome some of the limitations in productivity and product size of current fabrication processes, such as photolithography and imprinting lithography. For potential applications, transparent metal electrode, large size optical film, bus wire for narrow bezel, and water collecting surface, are briefly described to expand the application field from the well-known.

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Design of Transparent Conductive Oxides with Metal Patterning Techniques
Hyeji Kim, Junghyun Lee, Younggwang Lee, Minwoo Hong, Dohyun Kim, Inpyo Lee, Chanhyuk Choi, Joondong Kim
Journal of the Korean Solar Energy Society.2024; 44(5): 33. CrossRef
Fabrication of Nanopatterned Metal Mold based on Zirconia Nanoparticle and its Application into Thermal Replication of Thermoplastic Materials
Selim Park, Kyoung Chan Min, Sowon Jang, Yujin Ha, Wook-Bae Kim
Journal of the Korean Society for Precision Engineering.2022; 39(7): 501. CrossRef
Variation of a Triangular Pattern Shape due to Shrinkage in the Repeated UV Imprint Process
Jiyun Jeong, Su Hyun Choi, Young Tae Cho
Journal of the Korean Society of Manufacturing Process Engineers.2020; 19(7): 67. CrossRef
Finding Ways to Deform Fine Patterns Fabricated by UV Curable Resin
Woo Young Kim, Su Hyun Choi, Seonjun Kim, Young Tae Cho
Journal of the Korean Society for Precision Engineering.2020; 37(4): 291. CrossRef

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Effect of Thiol Coating Time on the Morphology and Wettability of Copper Nanowires: Wonshik Kwak, Kihwan Kim, Handong Cho, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2018;35(4):457-461.
Published online April 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.4.457

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A study of super-hydrophobic surface originated from the analysis of lotus leaf in the nature and fabrication method of super-hydrophobic surface on copper substrate has been researched for, showed functional surfaces with anti-corrosion. However, since copper nanowires decomposed during thiol coating, it is necessary to reseach on the relation with morphology of copper nanowires and thiol coating time. In this study, the research is all about the effect of thiol coating time on wettability of copper nanowires surface. Copper hydroxide nanowires were made up by oxidation using dipping method and a polymer layer was formed on nanowires using thiol coating. Surface characteristics were assessed using scanning electron microscopy and liquid contact angles. The conclusion showed relation for wettability of thiol coated copper hydroxide nanowires with thiol coating time and proposed method would be favorable for anti-corrosion functional surface.