• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1199-1202
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• 2003

In this research, microfabrication technique using localized electrochemical deposition is presented. Electric field is localized near the tip end region by applying ultra short pulses. Platinum tip is used as the counter electrode and copper is deposited on the copper substrate in 0.5 M CuSO$_4$ and 0.5 M H$_2$SO$_4$ electrolyte. The deposition characteristics such as size, shape, and structural density according to pulse duration and applied voltage are investigated. Micro-columns less than 10 $\mu\textrm{m}$ in diameter are fabricated using the presented technique. The process can be potentially used for three dimensional metal structure fabrications with micrometer feature size.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.686-692
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• 2012

Solid free-form fabrication (SFF) technology was developed to fabricate three-dimensional (3D) scaffolds for tissue engineering (TE) applications. In this study, we developed a polymer deposition system (PDS) and created 3D microstructures using a bioresorbable polycaprolactone (PCL) polymer. Fabrication of 3D scaffolds by PDS requires a combination of several devices, including a heating system, dispenser, and motion controller. The system can process a polymer with extremely high precision by using a 200 ${\mu}m$ nozzle. Based on scanning electron microscope (SEM) images, both the line width and the piled line height were fine and uniform. Several 3D micro-structures, including the ANU pattern (a pattern named after Andong National University), $45^{\circ}$ pattern square, frame, cylindrical, triangular, cross-shaped, and hexagon, have been fabricated using the polymer deposition system.

• Journal of Powder Materials
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• v.23 no.2
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• pp.170-176
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• 2016

Lithium-ion batteries (LIBs) are rapidly improving in capacity and life cycle characteristics to meet the requirements of a wide range of applications, such as portable electronics, electric vehicles, and micro- or nanoelectro-mechanical systems. Recently, atomic layer deposition (ALD), one of the vapor deposition methods, has been explored to expand the capability of LIBs by producing near-atomically flat and uniform coatings on the shell of nanostructured electrodes and membranes for conventional LIBs. In this paper, we introduce various ALD coatings on the anode, cathode, and separator materials to protect them and improve their electrochemical and thermomechanical stability. In addition, we discuss the effects of ALD coatings on the three-dimensional structuring and conduction layer through activation of electrochemical reactions and facilitation of fluent charge collection.

• Journal of the Speleological Society of Korea
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• no.76
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• pp.15-17
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• 2006

[ $YBa_2Cu_3O_{7-{\delta}}$ ] superconductor films have been prepared on silver substrates by electrophoretic deposition. As silver does not react with $YBa_2Cu_3O_{7-{\delta}}$ compound and has little influence on its superconductivity, it is usually doped in $YBa_2Cu_3O_7$ to improve the strength of the material and eliminate micro cracks. It has been proved that Ag additive can lower the melting temperature of $YBa_2Cu_3O_{7-{\delta}}$ and act as linking bridge among $YBa_2Cu_3O_{7-{\delta}}$ particles, thus in this paper Ag doped $YBa_2Cu_3O_{7-{\delta}}$ thick films are prepared by electrophoretic co deposition. As there are only some referenced experience formula and models for co electrophoretic deposition and does not exist unified explanation, the behavior of Ag particles during co electrophoretic deposition is also studied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1837-1842
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• 2010

Studies on alternative energy have been carried out for many decades because of the accelerated exhaustion of fuel. While the efficacy of solar cells is still low in comparison with that of nuclear power, solar cells have been highlighted as potential sources of alternative energy because they are environmentally friendly and have a source of unlimited energy, namely, the sun. In this study, the optimum efficiency of solar cells was simulated as a function of the incident angle of sunlight and the geometric shapes of patterns using MATLAB and MathCAD software. The foremost efficiency of the solar cell was found to be 1.10 when the thickness and width of the patterns were in the range 25-$50{\mu}m$ and 50-$100{\mu}m$, respectively. To achieve the 25 um thick layer, 100,000 cps silver paste and 500 um orifice tip has been successfully implemented with Micro-Dispensing Deposition Writing.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.6
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• pp.483-489
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• 2014

In this study, experiments were conducted for micro pattern printing to combine solution atomization process and stencil printing based on electrospray deposition. The stencil mask fabricated by etching the photosensitive glass placed below 0.3 mm distance to substrate has 100 um line width. The process parameters of electrospray deposition system for the atomization of the solution are applied voltage and supply flow rate of the solution. Meniscus angle of cone-jet was optimized by varying the supply flow rate from 0.3 ml/hr to 0.7 ml/hr. Voltage condition was verified having symmetric cone-jet angle and no pulsation at 8.5 kV applied voltage. In addition, a number of micro patterns are printed using a single 1 step process by solution atomization process. Variable line width of approximate 100 um was confirmed by changing conditions of solution atomization regardless of the pattern size of stencil mask.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.331-335
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• 1999

Electroless plating nickel has superior mechanical property to electroplated nickel. Furthermore nickel can be coated on nonconducting substrate. In this research, electroless plating of nickel were conducted in different bath condition to find optimum conditions of electroless nickel plating for MEMS applications. The selectivity of activation method on several substrates was investigated. The effects of nickel concentration, reducing agent concentration and inhibitor on deposition rate were investigated. The effect of pH on deposition rate and content of phosphorous in deposited nickel was also investigated.

• Transactions of Materials Processing
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• v.25 no.6
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• pp.353-358
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• 2016

Direct energy deposition (DED) is an additive manufacturing technique that involves the melting of metal powder with a high-powered laser beam and is used to build a variety of components. In recent year, it can be widely used in order to produce hard, wear resistant and/or corrosion resistant surface layers of metallic mechanical parts, such as dies and molds. For the purpose of the hardfacing to achieve high wear resistance and hardness, application of high speed steel (HSS) can be expected to improve the tool life. During the DED process using the high-carbon steel, however, defects (delamination or cracking) can be induced by rapid solidification of the molten powder. Thus, substrate preheating is generally adopted to reduce the deposition defect. While the substrate preheating ensures defect-free deposition, it is important to select the optimal preheating temperature since it also affects the microstructure evolution and mechanical properties. In this study, AISI M4 powder was deposited on the AISI 1045 substrate preheated at different temperatures (room temperature to $500^{\circ}C$). In addition, the micro-hardness distribution, cooling rates, and microstructures of the deposited layers were investigated in order to observe the influence of the substrate preheating on the mechanical and metallurgical properties.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1544-1553
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• 2005

In this article, a micro cantilever array actuated by PZT films is designed and fabricated for micro fluidic systems. The design features for maximizing tip deflections and minimizing fluid leakage are described. The governing equation of the composite PZT cantilever is derived and the actuating behavior predicted. The calculated value of the tip deflection was 15 ${\mu}m$ at 5 V. The fabrication process from SIMOX (Separation by oxygen ion implantation) wafer is presented in detail with the PZT film deposition process. The PZT films are characterized by investigating the ferroelectric properties, dielectric constant, and dielectric loss. Tip deflections of 12 ${\mu}m$ at 5 V are measured, which agreed well with the predicted value. The 18 ${\mu}l/s$ leakage rate of air was observed at a pressure difference of 1000 Pa. Micro cooler is introduced, and its possible application to micro compressor is discussed.

• Journal of the Korean institute of surface engineering
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• v.45 no.4
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• pp.151-154
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• 2012

A hydrophobic surface has been fabricated on aluminum by two-step surface treatment processes consisting of structure modification and surface coating. Nature inspired micro nano scale structures were artificially created on the aluminum surface by a blasting and Ar ion beam etching. And a hydrophobic thin film was coated by a trimethylsilane ($(CH_3)_3SiH$) plasma deposition to minimize the surface energy of the micro nano structure surface. The contact angle of micro nano structured aluminum surface with the trimethylsilane coating was $123^{\circ}$ (surface energy: 9.05 $mJ/m^2$), but the contact angle of only trimethylsilane coated sample without the micro nano surface structure was $92^{\circ}$ (surface energy: 99.15 $mJ/m^2$). In the hydrophobic treatment of aluminum surface, a trimethylsilane coated sample having the micro nano structure was more effective than only trimethylsilane coated sample without the micro nano structure.