• Tribology and Lubricants
• /
• 제36권5호
• /
• pp.267-273
• /
• 2020

This study experimentally investigates hydrophobic surfaces fabricated via additive manufacturing. Additive manufacturing, commonly known as 3D printing, is the process of joining materials to fabricate parts from 3D model data, usually in a layer-upon-layer manner. Digital light processing is used to fabricate hydrophobic surfaces in this study. This method uses photo-curable resins and ultraviolet (UV) sources. Moreover, this technique generally has faster shaping speeds and is advantageous for the fabrication of small components because it enables the fabrication of one layer at a time. Two photo-curable resins with different compositions are used to fabricate micro-patterns of hydrophobic surfaces. The resins are composed of a photo-initiator, monomer, and oligomer. Experiments are conducted to determine suitable process conditions for the fabrication of hydrophobic surfaces depending on the type of resin. The most important factors affecting the process conditions are the UV exposure time and slice thickness. The fabrication capability according to the process conditions is evaluated using the side and top views of the micro-patterns observed using a microscope. The micro-patterns are collapsed and intertwined when the exposure time is short because sufficient light (heat) is not applied to cure the photo-curable resin with a given slice thickness. On the other hand, the micro-patterns are attached to each other when the exposure time is prolonged because the over-curing time can cure the periphery of a given shape. When the slice is thicker, the additional curing area is enlarged in each slice owing to the straightness of UV light, and the slice surface becomes rough.

• 한국진공학회지
• /
• 제14권1호
• /
• pp.35-39
• /
• 2005

본 실험에서는 단위요소 사이에 채널을 갖는 Elementwise Patterned Stamp (이하 EPS)를 이용하여 싱글스탭 (single step)으로 4인치 웨이퍼를 임프린트 하는 공정을 수행하였다. 단위요소간의 간격이 3m인 EPS를 이용한 임프린트에서 50 - 100nm급의 패턴을 성공적으로 형성하였다. 그러나 임프린트 과정 중 EPS의 채널 부분에서 웨이퍼의 미소변형이 발생하여 단위요소의 미충전과 불균일한 잔여층이 형성되는 문제들이 발생하였다. 본 논문에서는 이러한 웨이퍼의 미소변형이 단위요소 충전과 패턴형성에 미치는 영향을 확인해 보기 위해 웨이퍼의 두께를 100 - 500㎛로 변화시켜가며 임프린트 실험을 수행하였고, 유한요소법(Finite Element Method, FEM)을 이용한 수치모사를 통하여 실험결과를 확인하였다. 또한 웨이퍼의 미소변형이 발생하는 또 다른 요인인 EPS의 채널 폭을 3mm, 2mm, 1mm로 변화시키며 수행한 수치모사를 통하여 안정된 임프린트 조건을 제시하였다.

• 한방안이비인후피부과학회지
• /
• 제20권1호통권32호
• /
• pp.130-144
• /
• 2007

UV-irradiated skin shows acutely erythema, edema, pigmantation (sunbum) and chronically coarse wrinkling, roughness, dryness, laxity (photoaging). Jawoongo(紫雲膏, JW) is clinically useful external application and effective bum, sunburn, wound and symptom of dryness(燥症) in skin disease. In this experiment, we examined if JW could cure the UVB-mediated acute skin damages, inhibit UVB-mediated oxidative stress and inflammation of skin, and block the photoaging. In vivo test, we found that JW could effectively cure the UVB-mediated acute skin damages(erythema, edema, angiogenesis, hyperplasia, infiltration of lymphocytes) and inhibit expression of HSP70, CYP1A1 and p53. We also found that JW could repair destruction of collagen fiber and inhibit activation of MMP-9, and inhibit expression of $NF-{\kappa}B$ p65, iNOS, hyperplasia of keratynocyte. In vitro test, we found that JW could inhibit expression of IKK, iNOS mRNA, and production of NO. These findings shows that JW could cure the UVB-mediated acute skin damages, inhibit UVB-mediated oxidative stress and inflammation of skin, and block photoaging.

• Bulletin of the Korean Chemical Society
• /
• 제21권1호
• /
• pp.61-64
• /
• 2000

FT-IR/ATR analysis shows that the oriental lacquer coating network degrades mostly in the unsaturated side chain. The rate of increase in carbonyl intensity (a measure of photodegradation) during the accelerated weathering test was substantially different for the unstabilized and stabilized samples; adding 2 wt% HALS into the oriental lacquer formulation enhanced photostabilization up to three times. Weight loss measurements, another indication of photodegradation, and SEM analysis support this conclusion. Despite the presence of the photo-stabilizer, the other properties of the lacquer were not significantly affected. In particular, the curing behavior of purified lacquer (PL) and HALS-stabilized samples is similar, although the in-situ DETA analysis showed that addition of HALS can slightly retard the cure reaction rate in oriental lacquer coating. It is hypothesized that this cure retardation may be related to the salt formation between HALS and acid of oriental lacquer.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.1833-1836
• /
• 2008

Recently as the micro surface features become higher and diverse in their shapes, the releasing of the molded features becomes more crucial for manufacturing of the micro patterned products. The higher aspect ratio of the features or more complex shape of the features results in larger releasing force, elongation or cohesive failure of the features during the releasing. Another issue would be the uniformity of the released surface features after molding, especially for applications with large area surface. The micro patterned optical film, one of typical applications for micro surface features, consists of two layers, the thermoplastic base film and the micro formed UV resin layer. Therefore two interfaces are typically involved during the forming of this micro featured film; one is between the base film and the UV resin and another is between the resin and the pattern master. To improve the releasing of the molded surface features, the adhesive characteristic was investigated at these two interfaces. A PET film was used as a base film and two UV curable resins with different surface energy were prepared for different adhesiveness. Also the two different pattern masters were employed; one is made from brass-copper alloy and fabricated with PMMA. The adhesiveness at each interface was measured for some combinations of these base film, UV resins and the masters and the effect of this adhesiveness on the releasing was investigated.

• Design & Manufacturing
• /
• 제16권3호
• /
• pp.9-15
• /
• 2022

In order to reduce the manufacturing costs of the glass lens, it is necessary to manufacture a lens using a UV curable resin or a thermosetting resin, which is a curable material, in order to replace a glass lens. In the case of forming a lens using a thermosetting material, it is necessary to form several lenses at once using the wafer-level lens manufacturing technologies due to the long curing time of the material. When a lens is manufactured using a curable material, an error in the shape of the lens due to the shrinkage of the material during the curing process is an important cause of defects. The major factors for these shape errors and deformations are the shrinkage and the change of mechanical properties in the process of changing from a liquid material during curing to a solid state after complete curing. Therefore, it is necessary to understand the curing process of the material and to examine the shrinkage rate and change of physical properties according to the degree cure. In addition, it is necessary to proceed with CAE for lens molding using these and to review problems in lens manufacturing in advance. In this study, the viscoelastic properties of the material were measured during the curing process using a rheometer. Using the results, Rheological investigation of cure kinetics was performed. At the same time, The shrinkage of the material was measured and simple mathematical models were created. And using the results, the molding process of a single lens was analyzed using Comsol, a commercial S/W. In addition, the experiment was conducted to compare and verify the CAE results. As a result, it was confirmed that the shrinkage rate of the material had a great influence on the shape precision of the final product.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.612-615
• /
• 2003

Maskless laser patterning process is developed using 3rd harmonic Diode Pumped Solid State Laser with near visible wavelength of 355 nm. Photo-sensitive curable polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D patterns. We performed basic experiments for the various process conditions such as laser power, writing speed, laser focus, and polymer optical property to gain the optimal conditions. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8${\mu}{\textrm}{m}$ width and 5.4${\mu}{\textrm}{m}$ height. This process could be applied to fabricate a single mode waveguide without expensive mask projection method.

• 한국세라믹학회지
• /
• 제54권6호
• /
• pp.470-477
• /
• 2017

Ceramic processing to fabricate 3D complex ceramic structures is crucial for structural, energy, environmental, and biomedical applications. A unique process is ceramic stereolithography, which builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This approach directly writes layers in liquid ceramic suspension and allows one to fabricate ceramic parts and products having more accurate, complex geometries and smooth surfaces. In this paper, both UV curable materials and processes are presented. We focus on the basic material principles associated with free radical polymerization and rheological behavior, cure depth and broadening of cured lines, scattering at ceramic interface and their corresponding simulation. The immediate potentials for ceramic AM to change industry fabrication are also highlighted.

• 접착 및 계면
• /
• 제7권4호
• /
• pp.39-44
• /
• 2006

A new kind of silicone-epoxy composite is reported in this research. The silicone-epoxy resin was synthesized by the hydrosilylation of tetramethycyclotetrasiloxane and 4-vinyl-1-cyclohexene 1,2-epoxy with a high reaction yield. It was found that the obtained silicone-epoxy resin shows a high reactive activity to the aluminum complex-silanol catalyst. The resin could be cured under the catalysis of $(Al(acac)_3/Ph_2Si(OH)_2$ at a concentration below 0.1 wt% to give a hard cured resin showing excellent optical clarity, UV resistance and thermal stability. It was also found that the Si-H groups facilitated the curing reaction and the silicone-epoxy resin bearing Si-H group could be cured effectively even if $Ph_2Si(OH)_2h$ was absent. Moreover, the UV resistance and thermal stability were improved significantly by the introduction of Si-H groups. This is possibly due to the reductive property of Si-H groups which can annihilate radical and peroxide effectively. This kind of silicone-containing epoxy composite might have very promising applications as optical resin, optical adhesive and encapsulation materials for electronic devices.

• Composites Research
• /
• 제27권6호
• /
• pp.236-241
• /
• 2014

본 연구에서는 공항 포장용 유지보수 재료로 사용되는 폴리머 콘크리트의 자외선 노출에 대한 기계적 물성 변화를 확인하기 위해 자외선 노출 전/후 시편의 압축강도 및 연성인자의 변화를 평가하였다. 현재 공항 포장용으로 사용되는 폴리머 콘크리트의 비율과 선행연구를 통해 얻은 최적 배합비율을 참고하여 시편을 제작하였다. 자외선 발생 램프의 출력을 고려하여 자연상태에서 노출되는 등가시간을 계산한 후 최대 3년에 해당하는 시간만큼의 등가시간 동안 시편을 노출시켰다. 실험결과, 자외선 노출 자체는 재료물성에 거의 영향을 주지 않았으며, 자외선 노출에 따른 온도상승에 의한 재료물성 변화가 주로 관찰되었다. 자외선에 의해 발생된 열에 노출된 후 모든 시편에서 인성은 감소하고, 압축강도는 증가하는 경향을 나타내었다.