• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1563-1565
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• 2008

Hydrophobic plastic plates employing nano surface features are injection molded using thermoplastic materials. A variotherm molding process is devised for filling the nano pores and releasing the molded nano features from the master. The size of the molded nano surface features are about 100nm in diameter and 200nm in height. The size of the molded plate is about 30mm x 30mm and the thickness is 1mm. As molding materials, Polypropylene, PMMA, COC and PC are employed, which are all typical commodity thermoplastic materials. The mold temperature(stamper temperature) is investigated as a major processing parameter for molding high aspect ratio nano surface features. Almost fully molded nano features are fabricated above a certain level of mold temperature depends on the employing material. The contact angles on the injection molded plates are measured to estimate the hydrophobicity and found to have higher contact angle up to 180% compared to the blank plate with no surface features.

• Bulletin of the Korean Chemical Society
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• 제23권3호
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• pp.477-480
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• 2002

A new microporous TiO2-pillared layered titanate has been successfully prepared by hybridizing the exfoliated titanate with the anatase TiO2 nano-sol. According to the X-ray diffraction analysis and N2 adsorption-desorption isotherms, the TiO2-pillared layered titanate showed a pillar height of ~2 nm with a high surface area of ~460 m2/g and a pore size of ~0.95 nm, indicating that a microporous pillar structure is formed. Its photocatalytic activity was evaluated by measuring the photodegradation rate of 4-chlorophenol during irradiation of catalyst suspensions in an aqueous solution. An enhancement in activity of ca. 170% was obtained for TiO2-pillared layered titanate compared to that of the pristine compound such as layered cesium titanate.

• 한국생산제조학회지
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• 제18권6호
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• pp.697-701
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• 2009

A simple method for the fabrication of porous nano-master for the anti-reflection effect on the transparent substrates is presented. In the conventional fabrication methods for antireflective surface, coating method using materials with low refractive index has usually been used. However, it is required to have a high cost and long processing time for mass production. In this paper, we developed a porous nano-master with anti-reflective surface for the molding stamper of the injection mold, hot embossing and UV imprinting by using the aluminum anodizing process. Through two-step anodizing and etching processes, a porous nano-master with anti-reflective surface was fabricated at the large area. Pattern size Pore diameter and inter-pore distance are about 130nm and 200nm, respectively. In order to replicate anti-reflective structure, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.51.1-51.1
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• 2009

나노 임프린트 리소그래피 기술은 마스터 몰드 표면의 나노 패턴을 물리적인 가열, 가압 공정을 통해 기판 위의 고분자 층으로 전사시키는 기술이다. 이 기술은 기존의 노광 기술과는 다르게 직접적인 접촉을 통해 패턴을 형성하기 때문에 기능성 물질의 직접 패턴 형성이 가능한 기술이다. 투명 전극 재료는 다양한 분야으로의 응용이 가능하기 때문에 많은 연구가 진행되고 있다. ITO는 높은 투과율과 전도성 때문에 대표적인 투명 전극 물질로 사용되고 있다. 본 연구에서는 ITO nano particle solution을 이용하여 thermal 임프린팅 공정을 진행해 ITO nano pattern을 형성하는 연구를 진행하였고 이와 같은 기술을 이용하여 glass와 LED 기판에 ITO nano pillar pattern을 제작하였고 이를 주사 전자 현미경과 UV/vis를 이용하여 형성된 나노 ITO 나노 패턴의 구조와 광학적 특성을 분석하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.498-501
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• 2005

Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for manipulation of light. The existence of a photonic bandgap, a frequency range in which propagation of light is prevented in all direction, makes photonic crystal very useful in application where spatial localization of light is required for waveguide, beam splitter, and cavity. But fabrication of 3 dimensional photonic crystal is still difficult process. a concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air, and perforated with 2 dimensional lattice of hole. We show that the polymer slabs suspended in air with triangular lattice of air hole can exhibit the in-plane photonic bandgap for TE-like modes. The fabrication of Si master with pillar structure using hot embossing process was investigated for 2 dimensional low-index-contrast photonic crystal waveguide.

• 한국정밀공학회지
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• 제28권12호
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• pp.1419-1424
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• 2011

Nanoimprint lithography is a next generation lithography technology, which enables to fabricate nano to micron-scale patterns through simple and low cost process. Nanoimprint lithography has been applied in various industry fields such as light emitting diodes, solar cells and display. Functional patterns, including anti-reflection moth-eye pattern, photonic crystal pattern, fabricated by nanoimprint lithography are used to improve overall efficiency of devices in that fields. For these reasons, in this study, sub-micron-scaled functional patterns were directly fabricated on Si and glass substrates by thermal imprinting process using ZnO nano-particles dispersion resin. Through the thermal imprinting process, arrays of sub-micron-scaled pillar and hole patterns were successfully fabricated on the Si and glass substrates. And then, the topography, components and optical property of the imprinted ZnO nano-particles/resin patterns are characterized by Scanning Electron Microscope, Energy-dispersive X-ray spectroscopy and UV-vis spectrometer, respectively.

• 한국지반환경공학회 논문집
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• 제15권1호
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• pp.53-62
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• 2014

기존 국내 병설터널의 이격거리는 지반조건에 따라 터널직경(D)의 2~5D 정도를 확보하는 것이 일반화되어 왔으나, 최근 들어 대규모 절취에 따른 환경훼손 및 용지매입의 제약, 선형의 연속성 유지 등의 문제를 수반하게 되면서 터널 중심간격이 1D 이하인 근접 병설터널의 현장 적용성이 확대되고 있다. 특히, 터널 필라폭이 감소할 경우 필라(Pillar)의 안전성이 터널의 거동에 영향을 미치게 되므로, 이에 대한 다양한 연구의 필요성이 대두되고 있다. 그러나 현재까지의 연구는 주로 필라의 거동특성이나 설계 영향 인자들에 대한 분석에 국한되었으며, 실무에 적용 가능하고 정량적인 데이터는 제시하지 못하고 있는 실정이다. 이에 본 연구에서는 현장 시공조건을 최대한 반영할 수 있는 안정성 평가기법 및 설계 지표를 제시하기 위해 현장조건으로 터널 간 근접도가 가장 높은 갱구부 구간의 지형 및 지층특성을 반영하고, 암반 및 완전풍화 상태의 다층지반조건 상태를 모사하였으며, 지반 강도별 필라폭 변화에 따른 수치 해석적 분석을 통해 필라의 안전성이 터널 전체 안정성에 미치는 영향 정도를 평가하였다. 또한, 지표침하비 및 간섭체적비, 평균강도/응력비 등에 대한 종합적 분석 결과와 Hoek & Brown(1980) 파괴기준을 토대로 실무에 적용이 가능한 근접 병설터널 필라의 안전율 평가식과 지반 강도별 최소 필라폭을 제시하였다.

• 대한금속재료학회지
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• 제50권8호
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• pp.591-597
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• 2012

This paper presents regularly micro-textured glass surfaces ensuring the superhydrophobic properties in the Cassie-Baxter regime. The proposed surfaces were fabricated simply and efficiently by filling the glass material into a silicon micro-mold with periodic micro-cavities based on a thermal-reflow process, resulting in a successful demonstration of the textured glass surface with periodically-arrayed micro-pillar structures. The static and dynamic wetting properties of the micro-textured glass surfaces were characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH), respectively. In addition, the surface wettability was estimated theoretically based on Wenzel and Cassie-Baxter wetting theories, and compared with the experimental ones. Through the experimental and theoretical observations, it was clearly confirmed that the proposed micro-textured glass surfaces showed the slippery superhydrophobic behaviors in the Cassie-Baxter wetting mode.

• 한국정밀공학회지
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• 제22권12호
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• pp.16-21
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• 2005

Photonic crystals, periodic structure with a high refractive index contrast modulation, have recently become very interesting platform for the manipulation of light. The existence of a photonic bandgap, a frequency range in which the propagation of light is prevented in all directions, makes photonic crystal very useful in application where the spatial localization of light is required, for example waveguide, beam splitter, and cavity. However, the fabrication of 3 dimensional photonic crystals is still difficult process. A concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air and perforated with two dimensional lattice of hole. The fabrication of Si master with pillar structure using hot embossing process is investigated for two dimensional, low-index-contrast photonic crystal waveguide. From our research we show that the multiple stamp copy process proved to be feasible and useful.

• 설비공학논문집
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• 제22권2호
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• pp.64-69
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• 2010

We investigated the variation in contact angle of a nano-sized water droplet on a nano stripe-patterned surface using molecular dynamics simulation. By changing the height and width of the stripe pillar, and the gap width of the stripes, we observed the contact angle of water droplet in equilibrium. When the surface energies were 0.1 and 0.3 kcal/mol, the calculated contact angles were in good agreement with the Cassie and Baxter equation. However, when the surface energy is 0.5 kcal/mol, the contact angles are observed to be perturbed along the Cassie and Baxter equation.