• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.578-580
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• 2000

Micromolding process에 의한 refractive microlens array를 제작한다. PDMS, UV curable acryl adhesive 등 여러 가지 polymer 재료를 시도한다. 기존의 공장에서 주로 사용되던 etched bulk silicon, electroplated metal 등의 구조물이 아닌, polymer 구조물을 mold로 사용한다. Micromolding process에 의해 제작되는 microlens의 특성은 mold의 험상에 의해 결정된다. Reflow 공정에 의해 제작된 photoresist microlens는 매우 우수한 표면 특성과 형상 대칭성을 보여주므로, microlens의 mold로서 사용하기에 적합하다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.1
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• pp.72-77
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• 2019

The display that provides information to us through the visual sense is a very important information transmission means by intuitively transmitting information, and the liquid crystal display (LCD) is the most widely used information transmission display. In this paper, we studied solvent assisted micromolding as an alternative for the rubbing that is essential to align the liquid crystals in LCD and successfully aligned the liquid crystal molecules by constructing the nanostructures on conventional polyimide alignment layer. When generating the nanostructures on the polyimide film, there was a competitive correlation between the dissolution effect of the polymer by the solvent and the capillary effect of the polyimide molecules into the nanostructures of the mold depending on the process temperature. It was possible to form nanostructures with high step by deriving the optimum temperature. These nanostructures were able to align the liquid crystal molecules uniformly and demonstrated that they could form a desirable pretilt angle.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1887-1889
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• 2001

금속 재질의 MEMS 구조물의 모양을 폴리머에 전사하는 micromolding 과정에서 금속 구조물과 폴리머 사이를 분리 (demolding)시킬 때 금속 구조물과 폴리머 기판 사이에 분리를 방해하는 응착 (Adhesion) 문제가 발생한다. 이러한 응착 문제를 줄이고자 표면 에너지가 낮은 Self-Assembled Monolayer(SAM) coating을 금속(Ni) 표면에 시도하였다. SAM coating 막의 형성 여부와 응착력 (Adhesion force) 값을 구하기 위해 각각 XPS(X-ray photoelectron spectroscopy)와 AFM(Atomic force microscopy)을 이용하여 측정하였고 측정 결과 Ni 표면에 SAM이 형성되었음을 XPS로부터 알 수 있었고 SAM coating된 Ni 시편에서 더 낮은 응착력값을 보여 주었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.46-49
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• 2003

Microsystem technology (MST) which originated from semiconductor processes has been widely spreaded into tile other industry such as sensors, micro fluidics and displays. The MST, however. has been troubled in spreading with its high cost and material limitations. So, in this paper, new process for micromolding technology using silicone rubber mold was introduced. Silicone rubber mold, which was fabricated by vacuum casting. can be transferred a master pattern to a final product with the same shape but different materials. In order to verify the possibility of application of silicone rubber mold to the MST, its transferability was evaluated. and then it applied to the fabrications of polishing pad and PDP barrier ribs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1380-1387
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• 2003

Microsystem technology (MST) which originated from semiconductor processes has been widely spreaded into the other industry such as sensors, micro fluidics and displays. The MST, however, has been troubled in spreading with its high cost and material limitations. So, in this paper, new process for micromolding technology using silicone rubber mold was introduced. Silicone rubber mold, which was fabricated by vacuum casting, can be transferred a master pattern to a final product with the same shape but different materials. In order to verify the possibility of application of silicone rubber mold to the MST, its transferability was evaluated, and then it applied to the fabrications of polishing pad and PDP barrier ribs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.94-97
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• 2002

Micromolding methods are most suitable for mass production of plastic microlens and lens array with low cost. Among the procedures related with micromolding of microlens array, fabrication of mold insect which contains micro cavity of lens shape is the most important stage. In this study, nickel mold inserts for 45 $\mu\textrm{m}$ and 95 $\mu\textrm{m}$ diameters lens way were fabricated using electroforming process. The mother for metal mold inset was made using reflow method. A micro compression molding with polymer powders was used to test the qualities of the metal mold insets. Micro lens profile and surface roughness was measured by interferometric technique and AFM, respectively. The final molded lens replicated the mother well, and had good surface quality.

• Clean Technology
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• v.24 no.2
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• pp.105-111
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• 2018

This study presents a novel and eco-friendly process that can precisely control the location of the patches on the patch particles. The method of manufacturing these anisotropic hexagram patch particles consists of sequential combinations of two separate methods such as a sequential micromolding technique for fabricating patch particles and a selective localization method for controlling the location of patches on the patch particles. The micromolding technique was carried out using physicochemically stable material as a micromold. In order to fabricate the highly stable patch anisotropic hexagram particles, the perfluoropolyether (PFPE) micromold was used to the process of the micromolding technique because they could prevent the problem of diffusion of hydrophobic monomers while conventional poly(dimethylsiloxane) (PDMS) micromold is limited to prevent the problem of diffusion of hydrophobic monomers. Based on combination methods of the micromolding technique and the selective localization method, the reproducibility and stability have been improved to fabricate 12 different types of anisotropic hexagram patch particles. This fabrication method shows the unique advantages in eco-friend condition, easy and fast fabrication due to less number of process, the feasibility of a mass production. We believe that these anisotropic hexagram patch particles can be widely utilized to the field of the directional self-assembly.

• Clean Technology
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• v.18 no.3
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• pp.295-300
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• 2012

Synthesis of well-defined particle with tunable size, shape, and functionalities is strongly emphasized for various applications such as chemistry, biology, material science, chemical engineering, medicine, and biotechnology. This study presents micromolding method for the fabrication of anisotropic particles with elegant control of curvature of covex roof. For the demostration of rapid fabrication of the particles, we have applied polydimethylsiloxane (PDMS) micromold as structure guiding template and wetting fluid to control curvature of roof of the particles. Based on this approach, we can control the radius of curvature from $20{\mu}m$ to $70{\mu}m$ with different aspect ratio of mold. In addition, wetting fluids with different wetting properties can also modulate the height and radius of curvature of the particles. We envision that this methodology is promising tool for precise control of particle shape in 3-dimensional space and new synthetic route for anisotropic particles with cost effective, simple, easy, and fast procedure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.5
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• pp.419-423
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• 2008

A new polymer replication technology using ultrasonic vibration is proposed and demonstrated. A commercial ultrasonic welder has been used in this experiment. Two different types of nickel molds have been fabricated: pillar type and pore type microstructures. Polymethyl methacrlylate (PMMA) has been used as the replication material and the optimal molding time was 2 sec and 2.5 sec for pillar-type and pore-type micromolds, respectively. Compared with the conventional polymer micromolding techniques, the proposed ultrasonic micromolding technique has the shortest processing time. In addition, only contact area between micromold and polymer substrate is melted so that the thermal shrinkage can be minimized. The fabricated PMMA microstructures have been very accurately replicated without vacuum. The proposed ultrasonic molding technique is a good alternative for high volume production.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.4
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• pp.175-183
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• 2002

In this paper, the surface modification effect of self-assembled monolayer(SAM) of 1-dodecanethiol [$CH_3$($CH_2$)$_{11}$SH] used as an anti-adhesive film in micromolding process was studied. Monolayers of 1-dodecanethiol[$CH_3$(CH$_2$)$_{11}$SH] were obtained by immersing a metal place in pure 1-dodecanethiol. SAM film on the nickel plate has been examined by using X-ray photoelectron spectroscopy(XPS). The focus has been placed on S-Ni bonding. From the XPS analysis, sulfur atoms were detected from the SAM film as a chemical composition of S-Ni. In order to measure an adhesion force of the SAM-coated nickel surface, atomic force microscopy(AFM) was used in force-distance mode, which whows the micro-adhesive force on solid surface. It was shown that adhesion forces measured from the SAM-coated nickel surface and the Ni surface without SAM coating were 3.52nN and 5.32nN, respectively. In order to investigate the effect of SAM coating on the surface foughness the replica in demolding process, hot embossing experiments were performed using a SAM-coated nickel master and a nickel master without SAM coating. Surface roughness of replica from the SAM-coated master showed 25nm and that of replica from master without SAM coating was 35nm. The smoother surface roughness of the replica from the SAM-coated, master is believed to result from reduction in the adhesion forces.ces.