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윤지욱(Ji-Wook Yoon),설명헌(Myeng-Heon Seol),김재근(Jae-geun Kim),손익부(Ik-Bu Shon),이호(Ho Lee) 한국레이저가공학회 2008 한국레이저가공학회 학술대회 논문집 Vol.2008 No.-
Femtosecond laser machining is appropriate method for micromachining because of short pulse duration and minimizing the heat diffusion. We fabricated hologram pattern on the mold material using the femtosecond laser ablation. We machined the mold with the various fluence ranging from 3J/㎠ to 3.7J/㎠. We were able to produce the gratings on the mold material with the pitches as small as 15.um.
윤지욱(Ji-Wook Yoon),이종흔(Jong-Heun Lee) 한국세라믹학회 2019 세라미스트 Vol.22 No.1
Breath analysis is rapidly evolving as a non-invasive disease recognition and diagnosis method. Metal oxide gas sensors are one of the most ideal platforms for realizing portable, hand-held breath analysis devices in the near future. This paper reviewed the recent developments in metal oxide gas sensors detecting exhaled biomarker gases such as nitric oxides, acetone, ammonia, hydrogen sulfide, and hydrocarbons. Emphasis was placed on strategies to tailor sensing materials/films capable of highly selective and sensitive detection of biomarker gases with negligible cross-response to ethanol, the major interfering breath gas. Specific examples were given to highlight the validity of the strategies, which include optimization of sensing temperature, doping additives, utilizing acid-base interaction, loading catalysts, and controlling gas reforming reaction. In addition, we briefly discussed the design and optimization method of gas sensor arrays for implementing the simultaneous assessment of multiple diseases. Breath analysis using high-performance metal oxide gas sensors/arrays will open new roads for point-of-care diagnosis of diseases such as asthma, diabetes, kidney dysfunction, halitosis, and lung cancer.
빔 쉐이핑을 이용한 펨토초 레이저 ITO 박막 가공 깊이 제어에 대한 연구
김훈영,윤지욱,최원석,황경현,조성학,Kim, Hoon-Young,Yoon, Ji-Wook,Choi, Won-Seok,Stolberg, Klaus,Whang, Kyoung-Hyun,Cho, Sung-Hak 한국레이저가공학회 2014 한국레이저가공학회지 Vol.17 No.1
Indium tin oxide (ITO) is an important transparent conducting oxide (TCO). ITO films have been widely used as transparent electrodes in optoelectronic devices such as organic light-emitting devices (OLED) because of their high electrical conductivity and high transmission in the visible wavelength. Finding ways to control ITO micromachining depth is important role in the fabrication and assembly of display field. This study presented the depth control of ITO patterns on glass substrate using a femtosecond laser and slit. In the proposed approach, a gaussian beam was transformed into a quasi-flat top beam by slit. In addition, pattern of square type shaped by slit were fabricated on the surfaces of ITO films using femtosecond laser pulse irradiation, under 1030nm, single pulse. Using femtosecond laser and slit, we selectively controlled forming depth and removed the ITO thin films with thickness 145nm on glass substrates. In particular, we studied the effect of pulse number on the ablation of ITO. Clean removal of the ITO layer was observed when the 6 pulse number at $2.8TW/cm^2$. Furthermore, the morphologies and fabricated depth were characterized using a optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS).
진동자를 이용한 하이브리드 극초단 펄스 레이저 초정밀가공시스템 개발 및 Cu-Zn합금 응용
최원석,윤지욱,조성학,강명창,Choi, Won-Suk,Yoon, Ji-Wook,Cho, Sung-Hak,Kang, Myung-Chang 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.4
In this paper, we describe experiment results using a vibration assisted hybrid femtosecond laser (${\lambda}$:795 nm) ultra-precision machining system. The hybrid system we have developed is possible that optical focal point of the femtosecond laser constantly and frequently within the range of PZT(piezoactuator) vibrator working distance. Using the hybrid system, We have experimented on brass and studied about differences of result of hole aspect ratio compare to general experiment setup of femtosecond laser system. Aspect ratio of a micro hole on brass is increased as 54% with 100 Hz vibration frequency and surface roughness of the side wall also improved compare to non-vibration.
극초단 펄스 레이저를 사용한 유리 내부의 필라멘테이션에 대한 실험적 연구
최원석,윤지욱,김주한,최지연,장원석,김재구,최두선,황경현,조성학,Choi, Won-Suk,Yoon, Ji-Wook,Kim, Joohan,Choi, Jiyeon,Chang, Won-Seok,Kim, Jae-Goo,Choi, Doo-Sun,Whang, Kyoung Hyun,Cho, Sung-Hak 한국레이저가공학회 2013 한국레이저가공학회지 Vol.16 No.1
We have successfully formed filament inside of a transparent soda-lime glass using a Ti:sapphire based femtosecond laser. To make filament form, keeping the laser intensity higher than critical intensity is essential. Also each of the machining parameters plays an important role for the formation of filament. In this paper, we study what parameter can possibly influence for formation of filament, and we introduce an application using filamentation by femtosecond laser for transparent material.
빔 쉐이핑된 펨토초 레이저를 이용한 터치스크린 패널의 ITO 박막 패터닝
김명주,김용현,윤지욱,최원석,조성학,최지연,Kim, Myung-Ju,Kim, Yong-Hyun,Yoon, Ji-Wook,Choi, Won-Seok,Cho, Sung-Hak,Choi, Jiyeon 한국레이저가공학회 2013 한국레이저가공학회지 Vol.16 No.4
Femtosecond laser patterning of ITO on a touch screen panel with a shaped fs laser beam was investigated. A quasi flat-top beam was formed using a variable mask and a planoconvex lens. The spatial profile of the original Gaussian beam and the shaped beam were monitored by a CCD beam profiler. The laser patterned ITO film was examined using an optical microscope, Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), and Atomic Force Microscope (AFM). It turned out that the quality of the ITO pattern fabricated by a shaped beam is superior to that of the pattern without beam shaping in terms of debris generation, height of the craters, and homogeneity of the bottom. Optimum processing window was determined at the laser irradiance exhibiting 100% removal of Sn. The removal rate of In was measured to be 83%.
바나듐이 도핑된 NiO 다공성 구조의 고감도 Trimethylamine 감응 특성
박세웅 ( Sei Woong Park ),윤지욱 ( Ji-wook Yoon ),박준식 ( Joon-shik Park ),이종흔 ( Jong-heun Lee ) 한국센서학회 2016 센서학회지 Vol.25 No.3
Pure and V-doped NiO porous structures were prepared by the evaporation-induced surfactant assembly and subsequent pyrolysis of assembled structures, and their gas sensing characteristics were investigated. Pure NiO porous structures showed negligible gas responses (S=Rg/Ra, Rg: sensor resistance in analytic gas; Ra: sensor resistance in air) to 5 ppm trimethylamine (S=1.17) as well as other interfering gases such as ethanol, p-xylene, toluene, benzene and formaldehyde (S=1.02-1.13). In contrast, the V-doped NiO porous structures exhibited a high response and selectivity to 5 ppm trimethylamine (S=14.5) with low cross-responses to other interfering gases (S=4.0-8.7) at 350oC. The high gas response of V-doped NiO porous structures to trimethylamine was explained by electronic sensitization, that is, the increase in the chemoresistive variation due to the decrease in the hole concentration. The enhanced selectivity to trimethylamine was discussed in relation to the interaction between basic trimethylamine gas and acidic V catalysts.
순수 알루미나와 탄소나노튜브 강화 알루미나 복합체의 극초단 펄스레이저 가공특성 비교
이준영(Jun-Young Lee),윤지욱(Ji-Wook Yoon),강명창(Myung-Chang Kang),조성학(Sung-Hak Cho) 한국기계가공학회 2013 한국기계가공학회지 Vol.12 No.6
In this paper, pure Al2O3 and hybrid carbon nanotube reinforced Al₂O₃ were sintered using the SPS(spark plasma sintering) method for high densification. A nanosecond laser (λ=1063 nm, τP=10 ns) and a femtosecond laser (λ=1027 nm, τP=380 fs) were installed on an optical system for the micromachining test. The ablation characteristics of the pure Al₂O₃ and CNT/Al₂O₃ composites, such as thermal effect and ablation depth, were investigated using FE-SEM and a confocal microscope device. Laser machining results for the two mating materials showed improved performances: CNT/Al₂O₃ composites showed good surface morphology of hole drilling without a melting zone due to the composites’ high thermal properties; also, the ablated depth of CNT/Al₂O₃ was higher than that of pure Al₂O₃.