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Fabrication of the Superhydrophobic Surface Inspired from Lotus-Effect
Dae-Hwan Jung(정대환),Hyuneui Lim(임현의),Jeong-Hyun Noh(노정현),Wan-Doo Kim(김완두) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Wettability of solid surfaces with liquids is governed by the chemical properties and the microstructure of the surfaces. We report on the preparation of liquid-repellent surfaces using surface-attached monolayers of perfluorinated polymer molecules on porous silica substrates. A covalent attachment of the polymer molecules to the substrate is achieved by generation of the polymer chains through starting a surface-initiated radical-chain polymerization of a fluorinated monomer. To this, self-assembled monolayers of azo initiators are attached to silica substrates, which are used to kick off the polymerization reaction in situ. The growth of the fluorinated polymer films and the characterization of the obtained surfaces by surface plasmon spectroscopy, XPS, and contact angle measurements is described. It is shown that perfluorinated polymer films can be grown with controlled thicknesses on flat and even on porous silica surfaces, essentially without changing the surface roughness. The combination of the low surface energy coating and the surface porosity allows generation of materials which are both water and oil repellent.
Fabrication of the patterned single-walled carbon nanotubes (SWNTs) films
Dae-Hwan Jung(정대환),Hee-Tae Jung(정희태),Wan-Doo Kim(김완두) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Single-walled carbon nanotubes (SWNTs) are interesting molecular wires with unique electronic properties that have been spotlighted for future solid-state nanoelectronics. We developed the fabrication process for the formation of the patterned SWNTs film. Unrestricted patterning of SWNTs films were employed lithography technology. The resultant versatile carbon nanotube film will be suitable for use in micro- or nanoscale electronic devices and circuits.
조영삼(Young-Sam Cho),정대환(Dae-Hwan Jung),한혁섭(Houkseop Han),김완두(Wan-Doo Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In the fabrication of dry adhesive structure, increasing contact-points or contact-area is the primary goal because the adhesive force grows in proportion to the contact-area. The simplest way to extend the contact surface is the fabrication by using soft materials. However, the column-array structure could confront the matting phenomenon which columns are stuck together. Therefore, we need a novel design to reduce the effective stiffness with adequate stiff materials like a gecko’s setae. In this study, we propose a novel design for the dry adhesive structure. Moreover, we analyzed whether the adhesive structure conforms the rough surface sufficiently through finite element method adopted the non-bonding interaction as the body force. Also, we fabricated the novel structures via UV lithography and some techniques. In addition, we examined the adhesive force of the novel structures.
김종호(Jong-Ho Kim),정여울(Yeoul Jung),유대환(Dae-Hwan Yu),윤승호(Seung-Ho Yun),박관수(Gwan-Soo Park) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
설계한 휴대용 EML은 수치해석 기법을 이용한 시뮬레이션을 통해 설계의 타당성을 검토 하였으며, 코일건의 스위치와 제어 회로를 구성하기 위하여 전자회로 이론을 이용 하였다. 그리고 승압회로를 이용하여 400V이상의 고전압을 생성하여 발사체를 발사 하였으며, 성과물의 크기와 무게를 최소화하여 휴대 가능하게 제작할 것을 목표로 하였고, 그에 맞는 EML을 제작하였다.
범정철,정대환,하종욱,박인준,이수복 한국공업화학회 2002 응용화학 Vol.6 No.1
The super water-repellent composite membrane were obtained using "grafting-from" polymerization with azo initiator chemically bonded on porous silica surface and radical-chain polymerization of fluorinated monomer. The synthesis of the fluorinated polymer brushes, membrane characterization were measured by XPS(X-ray Photoelectron Spectroscopy), SEM(Scanning Electron Microscopy), contact angle measurement, and permeation test. A liquid droplet on the ultra-hydrophobic surface has a contact angle as large as 160˚ with apparent surface free energy of ca. 0.1 dyn/cm. The first application of the surface to 4th generation composite membrane is also described. Permeability measurement was performing simple time-mass measurements using water and MeOH. The permeability of the membrane was changed remarkably by the surface modification with PFA brushes.