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민복기(Bokki Min),김재구(Jaegu Kim),조성학(Sunghak Cho),최두선(Doosun Choi),황경현(Kyunghyun Whang) 한국레이저가공학회 2008 한국레이저가공학회 학술대회 논문집 Vol.2008 No.-
This paper presents the method to fabricate a roll mold with microstructure using DPSS(diode pumped solid-states) UV laser. DPSS laser ablation makes it possible to micromachine by controlled energy density and pulse repetition rate of laser. But, In case of metal ablation, molten debris is caused by thermal damage. Hence, We suggest the process of the ablation of a photoresist(PR) coated on roll mold. And we design a roll coater for laminating the photoresist onto the curby surface of a copper roll mold. The microstructure on roll mold is fabricated by controlled laser pulse energy, pulse repetition rate, rotation speed and rotation number of roll. We compare and analyze the quality of microstructure by the wet etching process with the quality by the direct write process.
장원석(Wonseok Chang),최무진(Moojin Choi),김재구(Jaegu Kim),조성학(Sunghak Cho),황경현(Kyunghyun Whang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Self-Assembled Monolayers(SAMs) by alkanethiol adsorption to thin metal film are widely being investigated for applications as molecular recognition, selective binding of enzyme to surfaces, coating layer for corrosion protections or friction reduction and in fabrication of micro structure of bio molecular. In this study, standard positive photoresist techniques were adapted to generate micro/nano patterns of gold film using SAMs and femtosecond laser (200fs). SAMs formed by the adsorption of alkanethiols onto gold substrate with 100㎚ thickness are employed as very thin photoresist. We present the fabrication of thin film that has heterostructure of two different kinds of thiol by maskless laser patterning of organic SAMs. And this method also extend to nanoscale patterning using near-field scanning optical microscopy coupled with femtosecond laser.
레이저에 의해 패터닝 된 바늘과 탄성중합체와의 마찰 효과
김재구(Jaegu Kim),노승국(Seungkook Ro),박종권(Jongkweon Park),조성학(Sunghak Cho),황경현(Kyunghyun Whang) 한국레이저가공학회 2012 한국레이저가공학회지 Vol.15 No.3
The friction force of patterned needle in elastomer have been investigated to verify the application for bio and plastic industry. The micro pattern on the needle surface were prepared by 266 nm, 20 ns laser and 800 nm, 220 fs laser, which were able to generate the different surface roughness. The friction force was measured by the load cell of 10 N capacity. As the results, the friction force of no patterned needle is almost constant during the needle penetrates the silicone rubber sample. However, the needle having asperities shows the variation of the friction force. The higher the surface roughness is, the smaller the friction force is until the surface roughness is very high. In our experiment conditions, the reduction of the friction force by 20 % compared to no pattern needle was achieved with straight and 50 μm discrete line generated by 266 nm, 20 ns laser.
DPSS UV laser와 습식 식각을 이용한 금형강 미세 가공
민경익(Kyoungik Min),김재구(Jaegu Kim),조성학(Sunghak Cho),최두선(Doosun Choi),황경현(Kyunghyun Whang) 한국레이저가공학회 2009 한국레이저가공학회지 Vol.12 No.3
This paper describes the method for the fabrication of micro dot array on a plastic mold steel using DPSS (diode pumped solid-states) UV laser and wet etching process. We suggest the process of the ablation of a photoresist (PR) coated on plastic mold steel and wet etching process using solutions of various concentrations of FeCl3, HNO3 in water as etchants. This method makes it possible to fabricate metallic roller mold because the microstructures are directly fabricated on the metal surface. In the range of operating conditions studied, 17 μJ laser pulse energy and 50 ms laser exposure time, an etchant containing 40wt% FeCl3, 5wt% HNO3 and etch time for 45 s gave the 10 ㎛ of micro dot pattern on plastic mold steel.
김재구(Jaegu Kim),조성학(Sunghak Cho),장원석(Wonseok Chang),나석주(Suck-Joo Na),황경현(Kyunghyun Whang) 한국레이저가공학회 2007 한국레이저가공학회지 Vol.10 No.4
In this paper, we suggested the femtosecond laser processing using the mask which makes Gaussian spatial beam distribution to a normalized distribution by Fresenel diffraction. Holography pattern of the size of 320 × 320 ㎛² on the Cr thin film on glass substrate with a pixel size of 5 × 5 ㎛² was fabricated according to the pattern generated by the iterative Fourier transform algorithm (IFTA) algorithm. We analysed the damage threshold with an assumption the power distribution as Gaussian profile as 45 mJ/㎠, The regenerated image of letters through the diffractive pattern was well recognized at the screen.
클로로메틸 폴리이미드(CMPI) 박막과 근접장 나노 프로브 레이저 패터닝을 이용한 미세 형상 가공 기술
최무진(Moo Jin Choi),장원석(Wonseok Chang),김재구(Jaegu Kim),조성학(Sunghak Cho),황경현(Kyunghyun Whang ) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
Photo-induced surface alignment is charming as a non-contact photo-patternable alignment technology which can be used in the next generation of displays, such as large area, multi-domain. For decades, many polymer film have been investigated and developed to be used in the photo alignment. Among these photoreactive materials, recently developed polyimide, Chloromethylated Polyimide(CMPI) now became the focus of interests in this area because of its high photosensitivity and superior thermal stability. In this report, we present micro patterning method to form the nanoscale structure by Mask-Less laser patterning using this CMPI film and NSOM probe.
유영은(Yeong-Eun Yoo),김태훈(Tae-Hoon Kim),서영호(Young-Ho Seo),최두선(Doo-Sun Choi),이학주(Hak Joo Lee),김완두(Wan-Doo Kim),황경현(Kyunghyun WHang),조길원(Kil-Won Cho) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Some nano hair systems in the nature are found to show excellent adhesive characteristic, which is called dry adhesive. To develop a practical synthetic dry adhesive system, we mold nano hairs on plastic substrates using thermoplstic materials including COC, PP, PC and PMMA. and estimate the moldability and the adhesive characteristic. As a template for molding nano hairs, AAO membrane is first adopted, which is 60㎛ thick and 13㎜ in diameter. This membrane has about billions of through-holes of which diameter is around 200㎚. This AAO membrane and the pellet of materials are stacked in the mold and pressed to mold after heating up to be melted. The AAO membrane is removed using KOH to obtain the molded nano hairs. The molded nano hair substrates is estimated to show much better adhesive characteristic than a substrate without nano hairs.