• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1712-1713
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• 2011

Inkjet technology have many merits in plenty of industrial applications. However, deposited droplet has a very critical issue that is coffee ring effect, for the application to an industrial manufacturing process. To remove the coffee ring effect, the effect of thermal treatment conditions on shapes of inkjet printed silver patterns were investigated in various surface condition. The surface changes were characterized by the contact angle measurement. Droplets from a 50 ${\mu}m$ nozzle were printed on the substrate after optimizing the ejection of individual droplets. Ink with a high boiling point of main solvent results in coffee ring effect. This result implies that the dominant factor that determines the shape of droplet is the drying conditions of main solvent of silver nanoparticle colloidal ink. As a results, selecting a proper thermal treatment conditions is very crucial for better shapes of inkjet printed silver nanoparticle colloidal patterns.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.113-115
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• 2003

Droplet impinging into a cavity at micro-scale is one of important fluidic issues for microfabrications, e.g. bio-chip applications and inkjet deposition processes in the PLED panel manufacturing. The droplets generally dispensing from an inkjet head, which contains an array of nozzles, have a volume in several picoliters, while each nozzle jets the droplets into cavities with micron-meter size located on substrates. Due to measurement difficulties at micro-scale, the numerical simulation could serve as an efficient and preliminary way to evaluate the micro-sized droplet impinging behavior into a cavity. The micro-fluidic flow is computed by solving the three-dimensional Navier-Stokes equations through a finite volume discretization. The droplet front is predicted by a volume-of-fluid approach, in which the surface tension is modeled as a function of the fluid concentration. This paper discusses the influence of fluid properties, such as surface tension and fluid viscosity, on micro-fluidic characteristics at different jetting speeds in the deposition process via the proposed numerical approach.

• 대한기계학회논문집B
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• 제30권11호
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• pp.1107-1116
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• 2006

The droplet ejection process driven by an evaporating bubble in a thermal inkjet printhead is investigated by numerically solving the conservation equations for mass, momentum and energy. The phase interfaces are tracked by a level set method which is modified to include the effect of phase change at the interface and extended for multiphase flows with irregular solid boundaries. The compressibility effect of a bubble is also included in the analysis to appropriately describe the bubble expansion behaviour associated with the high pressure caused by bubble nucleation. The whole process of bubble growth and collapse as well as droplet ejection during thermal inkjet printing is simulated without employing a simplified semi-empirical bubble growth model. Based on the numerical results, the jet breaking and droplet formation behaviour is observed to depend strongly on the bubble growth and collapse pattern. Also, the effects of liquid viscosity, surface tension and nozzle geometry are quantified from the calculated bubble growth rate and ink droplet ejection distance.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.464-468
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• 2012

Three solvent systems, chlorobenzene (ink 1), chlorobenzene/o-dichlorobenzene (ink 2) and chlorobenzene/tetrahydronaphthalene (ink 3), were compared as printable inks for the fabrication of polymer light-emitting diodes (PLEDs) using poly[2-methoxy-5-(2-ethylhexyl-oxyl)-1,4-phenylenevinylene (MEH-PPV) as an emissive material and an inkjet printer (Fujifilm Dimatix DMP-2831). Ink 1 clogged the printer's nozzle and gave non-uniform film. Inks 2 and 3 were used to fabricate PLEDs with ITO/PEDOT:PSS/MEH-PPV/LiF/Al configurations. The best performance (turn-on voltage, 3.5 V; luminance efficiency, 0.17 cd/A; luminance, 1,800 cd/m) was obtained when ink 3 was used to form the emissive layer (thickness, 49 nm), attributable to the better morphology and suitable thickness of the MEH-PPV layer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1742-1746
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• 2008

An EHD (Electro-Hydro-Dynamic) jet for electrostatic inkjet head shows advantages to print micro-size patterns using various inks because it can generate sub-micron droplets and can use highly viscous inks. Thus, many researchers in industrial fields are concerned about the EHD jet in these days. Since the basic principle of the EHD jet is to form a droplet from an apex of meniscus at the end of the nozzle, the ejection mechanism can be changed by the shape of the meniscus. The stable ejection of the droplet is greatly affected by the shape of the meniscus which is also influenced by surface characteristics of the nozzle, electric potential and ink properties. Experiments have been performed using the nozzles with hydrophilic and hydrophobic coatings in this study. The hydrophobic nozzle forms the stable droplets in wider range of the electric potential than the hydrophilic nozzle does.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1103-1106
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• 2008

For the current display process, the innovative micro pattern fabrication process using semiconductor process should be developed, which requires the expensive equipment, the limited process environment and the expensive optic-sensitive material. The effort of process innovation during past several years ends up the limit of cost reduction. The existing ink jet technologies such as a thermal bubble ink jet printing and a piezo ink jet printing are required to shorten the nozzle diameter in order to apply to the micro pattern fabrication. In this paper, as one way to cope these problems the micro pattern equipment based on the electrostatic ink jet has been developed and carried out some experiments.

• 대한기계학회논문집B
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• 제34권1호
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• pp.89-94
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• 2010

박테리아나 세포를 표면에 패터닝하는 기술은 세포생물학, 항균제 스크리닝, 항균 모니터링, 조직 공학 등 다양한 분야에 적용될 수 있는 잠재력을 지니고 있다. 본 연구에서는 부분적으로 개조된 열방식의 잉크젯 프린터를 이용하여 박테리아를 평판 한천배지에 2차원 배열로 패터닝할 수 있는 기법을 개발하였다. 박테리아 용액의 농도는 잉크젯 노즐에서 분출되는 용액 한 방울에 한개의 콜로니가 형성되도록 최적화 하였고, 박테리아 농도와 한천배지 농도가 패터닝 성능에 미치는 영향을 정량적으로 측정하였다. 상용 잉크젯 프린터를 이용한 박테리아 패터닝은 기존 방법에 비해 비용과 재료의 소모가 적다는 장점이 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1542-1543
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• 2007

This paper presents the effect of driving waveform for piezoelectric bend mode inkjet printhead with optimized mechanical design. Experimental and theoretical studies on the applied driving waveform versus jetting characteristics were performed. The inkjet head has been designed to maximize the droplet velocity, minimize voltage response of the actuator and optimize the firing frequency to eject ink droplet. The head design was carried out by using mechanical simulation. The printhead has been fabricated with Si(100) and SOI wafers by MEMS process and silicon direct bonding method. To investigate how performance of the piezoelectric ceramic actuator influences on droplet diameter and droplet velocity, the method of stroboscopy was used. Using the water based ink of viscosity of 11.8 cps and surface tension of 0.025N/m, it is possible to eject stable droplets through 64 nozzles average velocity of 4.05 m/s with standard deviation of 0.06 m/s and average diameter of $29.2\;{\mu}m$ with standard variation of $0.5\;{\mu}m$.

• 한국정밀공학회지
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• 제31권1호
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• pp.83-90
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• 2014

EHD (electro-hydro-dynamics) patterning was performed under atmospheric pressure at room temperature in a single step. The drop diameter smaller than nozzle diameter and applied high viscosity conductive ink in EHD patterning method provide a clear advantage over the piezo and thermal inkjet printing techniques. The micro electrode pattern was printed by continuous EHD patterning method using 3-type control parameters (input voltage, patterning speed, nozzle pressure). High viscosity (1000cps) conductive ink with 75wt% of silver nanoparticles was used. EHD cone type nozzle having an internal diameter of $50{\mu}m$ was used for experimentation. EHD jetting mode by input voltage and applied 1st order linear regression in stable jet mode was analyzed. The stable jet was achieved at the amplitude of 1.4~1.8 kV. $10{\mu}m$ micro electrode pattern was created at optimized parameters (input voltage 1.6kV, patterning speed 25mm/sec and nozzle pressure -2.3kPa).

• 청정기술
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• 제7권3호
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• pp.169-178
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• 2001

섬유염색은 전 세계적으로 매우 큰 시장이나, 염료를 사용하여 섬유염색을 수행하는 기존 인쇄 공정의 경우 염료의 손실 및 환경오염의 문제점을 갖고 있다. 기존 공정들의 경우 섬유 인쇄 시 전처리 및 후처리 공정이 필요하고 이들 공정에서 폐수가 발생하게 된다. 이런 문제점들의 해결방안으로 전처리 및 후처리 공정이 필요없고 잉크를 효율적으로 사용할 수 있는 잉크제트 프린팅 기법을 섬유염색 기술에 적용하려는 노력이 진행중이다. 섬유인쇄를 위해 잉크제트 프린터를 사용할 경우 안료를 사용하기 때문에 잉크는 액체 상에 고체입자가 분산되어 있는 서스펜션 상태로 존재한다. 분자역학 모사 기법과 유사한 Stokesian 역학 모사 방법을 사용한 전산모사를 통해 외부에서 가해진 압력구배에 의해 노즐 관에 흐르는 분산잉크 중의 입자 분포 및 속도 분포 변화를 살펴보았다. 전산모사결과 입자의 부피분율이 낮을수록, 평균 무차원 서스펜션 속도가 낮을수록, 노즐 관과 입자 크기 사이의 비(H/a)가 클수록 입자들의 분포가 상당히 균일한 것으로 나타났다. 따라서 잉크제트 프린팅 기법을 사용하여 섬유인쇄를 수행하는 경우, 노즐 관에의 유속을 작게 하고 노즐 관과 입자 사이의 크기 비를 크게 해야 균일한 인쇄 성능을 얻을 수 있을 것으로 판단된다.