• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.24-24
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• 2018

One of the challenges in tissue engineering is the design of optimal biomedical scaffolds, which can be governed by topographical surface characteristics, such as size, shape, and direction. Of these properties, we focus on the effects of nano - to micro - sized hierarchical surface. To fabricate the hierarchical surface structure on poly(${\varepsilon}$-caprolactone) (PCL) film, we employed a nano/micro-casting technique (NCT) and modified plasma process. The micro size topography of PCL film was controlled by sizes of the micro structures on lotus leaf. Also, the nano-size topography and hydrophilicity of PCL film were controlled by modified plasma process. After the plasma treatment, the hydrophobic property of the PCL film was significantly changed into hydrophilic property, and the nano-sized structure was well developed, as increasing the plasma exposure time and applied power. The surface properties of the modified PCL film were investigated in terms of initial cell morphology, attachment, and proliferation using osteoblast-like-cells (MG63). In particular, initial cell attachment, proliferation and osteogenic differentiation in the hierarchical structure were enhanced dramatically compared to those of the smooth surface.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.153-153
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• 2012

자연계에는 다양한 생물체들의 표면 구조가 특수한 기능을 갖는 형태로 되어 있다. 이와 같이 특수한 기능을 갖는 생물체들의 표면 구조는 일반적으로 화학적 조성과 표면의 더불어 나노와 마이크로 구조가 혼합되어 있는, 이른바 hierarchical 구조를 보인다. 그 중에서도 표면 초소수성 특성을 보이는 연잎의 표면과 같은 hierarchical 구조는 self-cleaning effect 등의 기능성 표면 제작에 활용이 가능하여 이를 모사하기 위한 연구가 활발히 진행중에 있다. 이에 본 연구에서는 연잎과 같은 초소수성을 띄는 ZnO nano-in-micro hierarchical 구조를 저온 공정을 통하여 다양한 기판에 제작하였다. 이를 위하여 ZnO 나노 입자 분산 레진을 제작하였고 UV imprinting 과 수열합성법을 통하여 마이크로 패턴 상부에 ZnO 나노 입자가 형성된 ZnO nano-in-micro hierarchical 구조를 형성하였다. 제작된 ZnO hierarchical 구조의 젖음 특성은 표면 접촉각이 $160^{\circ}C$이상인 초소수성을 보였으며, 제작 공정에는 고온의 열처리가 수반되지 않아 PET film 등 다양한 기판에 ZnO hierarchical 구조를 제작할 수 있었다.

• 한국재료학회지
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• 제23권1호
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• pp.53-58
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• 2013

Superhydrophobic $SiO_2$ layers with a micro-nano hierarchical surface structure were prepared. $SiO_2$ layers deposited via an electrospray method combined with a sol-gel chemical route were rough on the microscale. Au particles were decorated on the surface of the microscale-rough $SiO_2$ layers by use of the photo-reduction process with different intensities ($0.11-1.9mW/cm^2$) and illumination times (60-240 sec) of ultraviolet light. With the aid of nanoscale Au nanoparticles, this consequently resulted in a micro-nano hierarchical surface structure. Subsequent fluorination treatment with a solution containing trichloro(1H,2H,2H,2H-perfluorooctyl)silane fluorinated the hierarchical $SiO_2$ layers. The change in surface roughness factor was in good agreement with that observed for the water contact angle, where the surface roughness factor developed as a measure needed to evaluate the degree of surface roughness. The resulting $SiO_2$ layers revealed excellent repellency toward various liquid droplets with different surface tensions ranging from 46 to 72.3 mN/m. Especially, the micro-nano hierarchical surface created at an illumination intensity of $0.11mW/cm^2$ and illumination time of 60 sec showed the largest water contact angle of $170^{\circ}$. Based on the Cassie-Baxter and Young-Dupre equations, the surface fraction and work of adhesion for the micronano hierarchical $SiO_2$ layers were evaluated. The work of adhesion was estimated to be less than $3{\times}10^{-3}N/m$ for all the liquid droplets. This exceptionally small work of adhesion is likely to be responsible for the strong repellency of the liquids to the micro-nano hierarchical $SiO_2$ layers.

• 한국산업융합학회 논문집
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• 제22권5호
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• pp.467-473
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• 2019

In this study, approached to improve durability of the multi-functional nano-pattern fabricated on the curved lens surface using nanoimprint lithography (NIL) was proposed, and the effects of the proposed methods on functionality after wear test were examined. To improve the mechanical property of ultraviolet(UV)-curable resin, UV-NIL was conducted at the elevated temperature around $60^{\circ}C$. In addition, micro/nano hierarchical structures was fabricated on the lens surface with a durable film mold. Analysis on the worn surfaces of nano-hole pattern and hierarchical structures and measurements on the static water contact angle and critical water volume for roll-off indicated that the UV curing process with elevated temperature is effective to maintain wettability by increasing hardness of resin. Also, it was found that the micro-scale pattern is effective to protect nano-pattern from damage during wear test.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.63-64
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• 2012

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.233.1-233.1
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• 2005

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.669-669
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• 2013

Hierarchical N doped TiO2 nanostructured catalyst with micro, meso and macro porosity have been synthesized by a facile self-formation route using ammonia and titanium isopropoxide precursor. The samples were calcined in different calcination temperature ranging from $300^{\circ}C$ to $800^{\circ}C$ at slow heating rate ($5^{\circ}C$/min) and designated as NHPT-300 to NHPT-800. $TiO_2$ nanostructured catalyst have been characterized by physico-chemical and spectroscopy methods to explore the structural, electronic and optical properties. UV-Vis diffuse reflectance spectra confirmed the red shift and band gap narrowing due to the doping of N species in TiO2 nanoporous catalyst. Hierarchical macro porosity with fibrous channel patterning was observed (confirmed from FESEM) and well preserved even after calcination at $800^{\circ}C$, indicating the thermal stability. BET results showed that micro and mesoporosity was lost after $500^{\circ}C$ calcination. The photocatalytic activity has been evaluated for methanol oxidation to formaldehyde in visible light. The enhanced photocatalytic activity is attributed to combined synergetic effect of N doping for visible light absorption, micro and mesoporosity for increase of effective surface area and light harvestation, and hierarchical macroporous fibrous structure for multiple reflection and effective charge transfer.

• Composites Research
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• 제20권2호
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• pp.17-20
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• 2007

Oxalic acid를 이용한 양극산화기법과 테플론 담금법을 이용하여 극소수성 나노/마이크로 구조물을 복제하였다. 이때 nanoscale hole의 사이즈는 양극산화시의 전압과 양극산화시간에 의해 결정된다. nanoscale에서 분자들 사이에 영향을 미치는 Van der Waals interactions에 의해서 복제 중 polymer sticking 현상이 발생한다. 이는 복제된 나노 구조물들이 서로 들러붙고 구부러지고 침강시키는 작용을 하게 된다. 이러한 현상이 microstructures위에 nanostructures가 존재하는 hierarchical structure가 생성되게 하며, 이러한 구조물은 연꽃잎의 미세구조물과 유사한 특성을 보인다. 즉 제작된 극소수성 나노/마이크로 구조물 표면은 접촉각이 $160^{\circ}{\sim}170^{\circ}$정도로 나타내고 또한 $1^{\circ}$미만의 sliding angle을 나타낸다.

• 센서학회지
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• 제31권4호
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• pp.244-248
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• 2022

Recently, several studies on the development of superhydrophobic surfaces using various nano-sized carbon-based materials have been conducted. The superhydrophobic surfaces developed using carbon soot have advantages such as low processing cost and remarkable physical and chemical properties. However, their durability is low. To address this problem, in this study, a superhydrophobic surface with high durability and a multilayer structure was fabricated using ethanol vapor treatment. Candle soot was deposited on an aluminum substrate coated with paraffin wax, and a micro-nano multilayer structure with a size of several micrometers was fabricated via ethanol vapor treatment. The fabricated superhydrophobic surface was confirmed to have a contact angle of at least 156° and high durability. Finally, it was confirmed that ethanol vapor not only changed the nanostructure of carbon but also affected the durability of the structure.

• 마이크로전자및패키징학회지
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• 제25권4호
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• pp.47-52
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• 2018

본 연구에서는 디스플레이에 적용되는 기능성 고분자 필름의 나노구조에 의한 기계적 물성 저하 문제를 해결하기 위해 열처리 방법과 멀티스케일 계층구조를 통한 PMMA(Poly(methyl-methacrylate)) 필름의 내구성 향상에 대해 연구하였다. PMMA 필름의 기계적 특성을 향상시키기 위한 열처리 공정은 고온/고압의 자유제적 제어공정과 고온 공정 후 급속히 냉각시키는 공정으로 구성되어 있으며, 열 나노임프린트를 이용하여 스크래치로부터 나노구조를 보호하기 위한 멀티스케일 계층구조를 형성하였다. 연필경도 시험에 의해 발생한 미세구조의 손상에 대한 평가를 위해 표면 형상 변화와 기능성 변화를 평가하였으며, 이를 통하여 열처리와 멀티스케일 계층구조가 스크래치에 의한 정접촉각 감소와 투과율 손실 저감에 효과적임을 확인하였다.