• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.108-108
• /
• 2017

다양한 생체 재료들을 이용한 마이크로 및 나노 크기의 표면 구조 모사는 조직공학에서 세포의 성장 및 분화에 영향을 미치는 것으로 알려져 있다. 특히, 마이크로-나노 구조가 공존하는 계층적 표면 구조는 골 아세포의 증식과 분화에 탁월하여 뼈 조직 재생에 응용되어 왔다. 기존에는 화학적 처리 기법을 이용하여 마이크로 표면 구조가 제작 되었으나 미세 거칠기 및 계층적 표면 구조의 제어가 어려웠다. 현재 이러한 문제점들을 극복하기 위해 플라즈마를 이용한 애칭 기법이 주로 이용되고 있으나 높은 온도 공정 환경에 의한 재료 선택의 한계점 및 오랜 공정 시간에 의한 플라즈마 처리 효율이 감소되어 원하는 표면구조 및 거칠기를 얻을 수 없다는 단점이 있다. 본 연구에서는 이러한 문제점들을 극복하기 위해 마이크로/나노 주조 기법 이용하여 생체적합성 합성고분자 poly(${\varepsilon}$-caprolactone) (PCL) 위에 연꽃잎 구조를 모사한 후 플라즈마 애칭 기법을 이용하여 마이크로-($3.01-3.07{\mu}m$)와 나노크기 ($97{\pm}16nm$)를 동시에 갖는 계층적 구조를 제작하였다. 제작된 구조의 효능을 관찰하기 위해 조골세포를 배양한 결과 평평한 PCL 구조보다 제작된 계층적 구조가 높은 세포성장률 (>2.9배)및 세포 분화도(>2.1배)를 보였다. 이러한 결과는 새로운 표면 공학적 모델로서 손상된 뼈 및 치아조직 재생을 위한 적합한 거칠기 및 표면적인 환경을 제공해 빠른 재생 능력과 더불어 치료기간의 단축을 가져 올 수 있을 것으로 사료된다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.283.1-283.1
• /
• 2014

최근 주위 환경에 존재하는 다양한 에너지를 전기에너지로 회수 또는 수확하는 에너지 하베스팅 기술(energy harvesting technology)이 크게 주목을 받고 있으며, 이와 더불어 압전 나노발전소자(piezoelectric nanogenerator)의 연구가 활발해 진행되고 있다. 한편, 수열합성법 또는 전기화학증착법을 이용하여 비교적 간단하게 수직으로 성장된 산화아연 나노로드(ZnO nanorod)는 광대역 에너지 밴드갭(wide bandgap energy)과 압전(piezoelectric)특성을 갖게 된다. 이렇게 수직 정렬된 나노로드의 기하학적 구조는 외부 물리적인 힘에 의해 구부러짐(bending) 변형이 일어나 압전특성이 효과적으로 일어나며, 이런 현상을 이용하여 압전 나노발전소자에 응용할 수 있다. 본 연구에서는 상부의 전극의 표면 거칠기(surface roughness)를 증가시켜 외부 힘에 의해 산화아연 나노로드가 효과적으로 변형을 일으켜 압전 특성을 향상시켰다. 실험을 위해, 산화아연 마이크로로드 어레이 (microrod arrays)와 실리카 마이크로스피어(silica microsphere)를 각각 템플릿으로 이용하여 그 위에 금(Au)를 증착하여 상부전극을 제작하였다. 산화아연 나노로드와 마이크로로드는 전기화학증착법을 이용해서 저온공정($75^{\circ}C$)으로 ITO가 코팅된 PET 기판위에 성장하였으며, 인가된 전압의 세기를 변화시켜 산하아연 구조물의 크기를 조절하였다. 또한 화합합성법으로 실리카 마이크로 스피어를 준비하였다. 이러게 제작된 상부전극을 통해 기존의 사용되었던 전극과 비교하여 성능이 향상됨을 확인하였으며, 이와 함께 이론적인 분석을 진행하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.11a
• /
• pp.144-145
• /
• 2012

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.29 no.2
• /
• pp.111-118
• /
• 2023

In this study, the feasibility of laser patterning on the surface of food packaging polymer film was confirmed, and the surface patterning process conditions of femtosecond laser were established. In addition, it was proved that the surface properties of the film can be changed and controlled through the fabrication of various patterned films on the surface of food packaging films such as HDPE, PP, and PET. Various patterned surfaces, including large-scale circular patterns induced by a single femtosecond laser pulse, roughness patterns achieved by overlapping single pulses by 30%, straight line patterns, roughness patterns obtained by overlapping straight line patterns, and grid patterns formed by intersecting straight line patterns were fabricated. The characteristics of the patterned HDPE, PP, and PET films, based on the surface pattern structure and size, were analyzed using SEM, AFM, and contact angle measurements. Compared to the surface of each control film without femtosecond laser patterning, the contact angles of the surfaces of large-area circular patterning HDPE and PP films, large-area roughness patterning HDPE and PP films by overlapping 30% of single pulses, and large-area roughness patterning PET film by overlapping rectilinear patterning were in the range of 27.1-37.5 degree. This indicated that the HDPE, PP, and PET films became more hydrophilic after patterning. On the other hand, the HDPE film patterned with a large-scale grid pattern exhibited a contact angle of 120.4 degree, indicating that the HDPE film became more hydrophobic after patterning. Therefore, films that have been changed to hydrophilic surfaces through patterning can be used in anti-fouling applications where proteins, cells, viruses, and other food materials do not adhere or are easily detached. In addition, if a superhydrophobic surface of 150 degrees or more is fabricated through more precise lattice patterning in the future, it will be possible to use it for superhydrophobic surface applications such as self-cleaning.

• Tunnel and Underground Space
• /
• v.20 no.2
• /
• pp.82-91
• /
• 2010

Grouting technology is one of the ground improvement methods used in water controlling and reinforcement of rock mass in underground structure construction. It is necessarily required to find out the characteristics of grout flow through discontinuities in a rock mass for an adequate grout design and performance assessment. Laminar flow is not always applicable in simulating a grout flow in a rock mass, since the rock joints usually have apertures at a micro-scale and the flow through these joints is affected by the joint roughness and the velocity profile of the flow changes partially near the roughness. Thus, the influence of joint roughness and aperture on the grout flow in rough rock joint was numerically investigated in this study. The commercial computational fluid dynamics code, FLUENT, was applied for this purpose. The computed results by embedded Herschel-Bulkley model and VOF (volume of fluid) model, which are applicable to simulate grout flow in a narrow rock joint that is filled with air and water, were well compared with that of analytical results and previously published laboratory test for the verification. The injection pressure required to keep constant injection rate of grout was calculated in a variety of Joint Roughness Coefficient (JRC) and aperture conditions, and the effect of joint roughness and aperture on grout flow were quantified.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.2
• /
• pp.51-57
• /
• 2008

Recently, the manufacturer of microscopic structures along with the development of technology to produce electronics, communication and semiconductors allows various components to be smaller in size, with higher precision. Therefore, preoccupancy of micro/nano-level machining technology in order to product micro/nano-components and parts is key issue in the field of manufacturing. In this study, machinability of micro machining was studied through the machining of aluminum, brass and steel workpiece. Inspection of the cutting force variation patterns of large numbers of micro machining indicated that characteristics of the workpiece. Surface roughness prediction methods were developed by considering the variation of the static part of the feed direction cutting force. The accuracy of the proposed approaches were tested with experimental data and the agreement between the predictions and actual observations are addressed.

• 전자공학회논문지 IE
• /
• v.44 no.3
• /
• pp.42-50
• /
• 2007

In this paper, elastic and plastic adhesion index was very important in deciding adhesive characteristics and varying elastic and plastic index, dimensionless load and pull-off force were analyzed and simulated. Finally, using AFM, experimental surface roughness parameters of substrates and pull-off force between tip and substrates were produced. Using these values, pull-off forces were calculated and were compared with experimental pull-off forces. Through simulation and experiment, it was found that interaction of asperity also had very important influence on adhesive contact.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.4
• /
• pp.105-110
• /
• 2014

This paper presents the hysteresis friction of a sliding elastomer on various types of surfaces. The hysteresis friction is calculated by means of an analytical model which considers the energy spent by the local deformation of the rubber due to surface asperities. By establishing the fractal character of the surfaces, the contribution to rubber friction of roughness at different length scales is accounted for. High resolution surface profilometer is used in order to calculate the main three surface descriptors and the minimal length scale that can contribute to hysteresis friction. The results show that this friction prediction can be used in order to characterize in an elegant manner the surface morphology of various surfaces and to quantify the friction coefficient of sliding rubber as a function of surface roughness, load and speed.

• Tunnel and Underground Space
• /
• v.29 no.6
• /
• pp.542-557
• /
• 2019

The behavior of rock mass is influenced by its microscopic feature of internal structure generating from forming and metamorphic process. This study investigated a new methodology for characterization of rock based on the X-ray CT (computed tomography) images reflecting the spatial distribution characteristics of internal constituent materials. The X-ray image based analysis is capable of quantification of heterogeneity and anisotropy of rock fabric, size distribution and shape parameter analysis of rock mineral grains, fluid flow simulation based on pore geometry image and roughness evaluation of unexposed joint surface which are hardly acquired by conventional rock testing methods.

• Proceedings of the Optical Society of Korea Conference
• /
• 2002.07a
• /
• pp.256-257
• /
• 2002

최근 광 스위치, 광학 가변 필터와 같은 광통신용 수동 소자를 구현하기 위해 실리콘 마이크로머시닝 기술을 바탕으로 한 광 MEMS(micro electro mechanical system) 기술이 각광을 받고 있다[1,2]. 특히, 실리콘 기판을 수직 식각하여 제작한 측면 저울은 2$\times$2광 스위치나 광 필터 등에서 반사 평면이나 투과평면으로 많이 이용되고 있다. 광학 평면의 거칠기 특성은 빛의 산란에 의한 광학 손실이나 평행 광 특성 유지 등과 밀접한 관계가 있다. (중략)