• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.773-774
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• 2006

Gas surface treatment is considered to be effective for titanium because of its high reactivity. In this study, we investigated the gas nitriding mechanism in titanium sintered parts produced by metal powder injection molding (MIM) process. The microstructure and nitrogen content of sintered MIM parts were greatly affected by nitriding conditions. Nitriding process strongly depended on the specimen size, for example, the size of micro metal injection molding (${\mu}-MIM$) product is so small and the specific surface is so large that the mechanical and functional properties can be modified by nitriding.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.1-5
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• 2008

An experimental study was performed to develop the rotational fuel injection system of the micro turbojet engine. In this system, fuel is sprayed by centrifugal forces of engine shaft. The test rig was designed and manufactured to get droplet information on combustion space. This experimental apparatus consist of a high speed rotational device(Air-Spindle), fuel feeder, rotational fuel injector and acrylic case. To understand spray characteristics, spray droplet size, velocity and distribution were measured by PDPA (Phase Doppler Particle Analyzer) and spray was visualized by using Nd-Yag laser-based flash photography. From the test results, the length of liquid column from injection orifice is controlled by the rotational speeds and Sauter Mean Diameter(SMD) is decreased with rotational speed. Also, Sauter Mean Diameter is increased as increasing mass flow rate at same rotational speeds.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.4
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• pp.14-20
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• 2015

Molding technologies for plastic microstructures have been extensively investigated during the last two decades, and theoretical and numerical studies on the micro molding process have provided efficient tools for the development of such molding technologies. In this paper, we present a review of numerical simulation methods for the micro molding process. Basic models for a description of the material property, governing equations of the flow and heat transfer during the molding process, and numerical methods will be described. Particularly, numerical simulations for micro injection molding and hot embossing processes will be presented, and their main features noted and compared to those for conventional molding processes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.127-132
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• 2014

Micro/nano-injection molding is one of the main processing techniques for polymer micro-fabrication. Most of the difficulties encountered in polymer micro-molding are caused by the demolding, rather than the filling of molds. Therefore, studying the demolding process is vitally important for manufacturing polymer replicas. The most important parameters are the thermal stress, friction and adhesion forces, and mechanical strength of the resist. In this research, we determinedthe effects of the processing conditions on the ejection force for cases involving two common thermoplastic polymers. The results showed that the processing conditions noticeably influenced the ejection force.

• Design & Manufacturing
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• v.16 no.3
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• pp.58-65
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• 2022

Micro-fluidic chip has been fabricated by lithography process on silicon or glass wafer, casting using PDMS, injection molding of thermoplastics or 3D printing, etc. Among these processes, 3D printing can fabricate micro-fluidic chip directly from the design without master or template for fluidic channel fabricated previously. Due to this direct printing, 3D printing provides very fast and economical method for prototyping micro-fluidic chip comparing to conventional fabrication process such as lithography, PDMS casting or injection molding. Although 3D printing is now used more extensively due to this fast and cheap process done automatically by single printing machine, there are some issues on accuracy or surface characteristics, etc. The accuracy of the shape and size of the micro-channel is limited by the resolution of the printing and printing direction or layering direction in case of SLM type of 3D printing using UV curable resin. In this study, the printing direction and thickness of each printing layer are investigated to see the effect on the size, shape and surface of the micro-channel. A set of micro-channels with different size was designed and arrayed orthogonal. Micro-fluidic chips are 3D printed in different directions to the micro-channel, orthogonal, parallel, or skewed. The shape of the cross-section of the micro-channel and the surface of the micro-channel are photographed using optical microscopy. From a series of experiments, an optimal printing direction and process conditions are investigated for 3D printing of micro-fluidic chip.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.75-76
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.209-210
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• 2013

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.388-390
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• 2003

Paste micro-injection molding process was applied for fabrication of barrier ribs of PDP in an attempt to reduce processing steps and materials loss during the processing. For the paste, a thermally curable one was used and for the mold, a polymeric soft mold was used. It was demonstrated that the micro-molding process can be used successfully in producing barrier ribs of PDP.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.901-902
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• 2009

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2451-2456
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• 2003

In biological cell manipulation, manual thrust or penetration of an injection pipette into an egg is currently performed by a skilled operator, relying only on visual feedback information. Massive load of various micro injection of either genes, fluid or cells in the postgenomic era calls a more reliable and automatic micro injection system that can test hundreds of genes or cell types at a single experiment. We initiated to study cellular force sensing in zebrafish eggs as the first step for the development of a more controllable micro injection system by any inexperienced operator. Zebrafish eggs at different developmental stages were collected and an integrated biomanipulation system was employed to measure cellular force during penetrating the egg envelope, the chorion. First of all, the biomanipulation system integrated with cellular force sensing instrument is implemented to measure the penetration force of cell membranes and characterize mechanical properties of zebrafish embryo cells. Furthermore, implementation of cellular force sensing system and calibration are presented. Finally, the cellular force sensing of penetrating cell membranes at each developmental stages was experimentally performed. The results demonstrated that the biomanipulation system with force sensing capability can measure cellular force at real-time while the injection operation is undergoing. The magnitude of the measured force was in the range of several hundreds of uN. The precise real-time measurement should provide the first step forwards for the development of an automatic and reliable injection system of various materials into biological cells.