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마이크로 노즐 내부 표면개질을 통한 유동제어의 실험적 연구
변도영(Doyoung Byun),김지훈(Jihoon Kim),엄성환(Seonghwan Eom),한규일(Kyuil Han),고한서(Hanseo Ko) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Recently, the research of microfluidics has been widely studied by many researchers, because the microfluidics system has been used in several fields such as lab-on-a-chip in medicine, colloid thruster in aerospace, microhydrodynamic in engineering, etc. The hydrophobic and hydrophilic internal surfaces are very important property to optimally design the microfluidic system. However, until now, no investigation is performed experimentally and theoretically to understand the flow instability and change of meniscus shape depending on the surface affinity in the microchannel. In this study, we visualized experimentally the flow characteristics in the microchannel whose surface is divided into hydrophilic and hydrophobic regions sequencially. For the hydrophilic and hydrophobic surfaces arrangement, when the meniscus reaches the interface region, the meniscus shape changes from concave to convex and the velocity near the centre increases.
Interference Effects of Electric Field for Multi-Nozzle Electrostatic Inkjet Device
변도영(Doyoung Byun),Tran Si Bui Quang,손상욱(Sang Uk Son),이석한(Sukhan Lee),Nguyen Vu Dat 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
To design and fabricate a multi-nozzle electrostatic drop-on-demand inkjet device, interference effects is numerically investigated and the optimal array configuration is presented. The electric voltage signals applied to the ring shaped upper electrode plates, against the nozzles, allow drop-on-demand ejection of droplet to take place: That is, a tiny droplet is taken away from the peak of the mountain shaped liquid meniscus formed at the nozzle orifice. Different from the case of single nozzle device, the neighboring electrode plates, which are designed and deposited for another nozzles, can affect the strength and distribution of electric field along the meniscus. Based on FEM(finite element method) simulation of the electric field and estimation of the critical condition for the ejection, this paper presents the appropriate nozzle array to prevent the interference effects.
EWOD(Electro-Wetting on Dielectric)에 의한 초소수성 표면에서의 액적 이동과 부유물의 영향
변도영(Doyoung Byun),이영종(Youngjong Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
This article discusses about the droplet movement on the super-hydrophobic surface by the electro-wetting on dielectric and the effect of particles on the contact angle as well as the movement is investigated. The movement of droplet, driven by the principle of electro-wetting on dielectric, and the effect of particles are experimentally verified according to the driving voltage and different particles concentrations (fluorescent, charged particles). To increase the contact angle, the super-hydrophobic surface is fabricated and applied to the dielectric layer for the EWOD device. Then its performance is verified and discussed.
비정상상태 복사열전달 해석을 위한 2 차 상류스킴 및 QUICK 스킴의 유한체적복사해법 적용 연구
변도영(Doyoung Byun),이건호(Gun Ho Lee),김만영(Man Young Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
Transient radiative heat transfer is analyzed in a one-dimensional slab using finite volume method (FVM). In this study, the step, 2nd order upwind, and QUICK schemes are used for incident diffuse radiation and collimated beam, respectively. The results for diffuse radiation show that all schemes applied in this study give good agreements with available published results. In case of collimated beam, however, the results show deviations from the analytical solutions. To successfully describe the propagations of collimated beam, shock capturing schemes such as TVD scheme are need to be developed.
Si Bui Quang Tran,Doyoung Byun(변도영),Vu Dat Nguyen,Tae Sam Kang(강태삼) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Based on this in-depth study of the meniscus behavior under various signals. the optimal signal is implemented to an EHD inkjet head for drop-on-demand operation. For applied ac voltage and ac voltage superimposed on dc voltage, the jetting phenomenon is a dynamic process due to sequential opposite sign signals. Jetting occurs at the end of the oscillation cycle, where the meniscus oscillates upward and arrives at its highest position.