• Proceedings of the Materials Research Society of Korea Conference
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• 2007.05a
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• pp.13.2-13.2
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• 2007

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.121-127
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• 2008

This paper presents design and fabrication of optimized geometry structure of electrostatic inkjet head. In order to verify effect of geometry shape, we simulate electric field intensity according to the head structure. The electric field strength increases linearly with increasing height of the micro nozzle. As the nozzle diameter decreases, the electric field along the periphery of the meniscus can be more concentrated. We design and fabricate the electrostatic inkjet heads, hole type and pole type, with optimized structure. It was fabricated using thick-thermal oxidation and silicon micromachining technique such as the deep reactive ion etching (DRIE) and chemical wet etching process. It is verified experimentally that the use of the MEMS inkjet head allows a stable and sustainable micro-dripping mode of droplet ejection. A stable micro dripping mode of ejection is observed under the voltages 2.5 kV and droplet diameter is $10\;{\mu}m$.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.73-79
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• 2011

Inkjet printhead may have a lot of nozzles to increase productivity as a manufacturing tool. So, the uniformity of jetting performance among a lot of nozzles has been one of the key issues in inkjet technology In this study, we investigated the cross-talk effect which should be reduced for uniform jetting performance among a lot of nozzles. Due to the cross-talk, the jetting performance of a nozzle can be affected when neighboring nozzles are firing. For experimental study, we used commercial inkjet head SE-128 from Dimatix. To understand the cross-talk effect of SE-128 head, we measured the change in jetting speed of a nozzle when neighboring nozzles are jetting. The measured jetting speed was compared to the case of one nozzle jetting. Also, we used laser vibrometer to measure change in pressure wave due to cross-talk. As a result of the cross-talk, the jetting speed can become faster or sometimes slower depending on firing nozzle location. If the all nozzle are jetting, the jetting speed of a nozzle became slower because the pressure wave for jetting is reduced.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.8
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• pp.737-742
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• 2014

This paper reports a customized silver ink and its inkjet printing process on a cellulose electro-active paper (EAPap). To synthesize a silver ink, silver nanoparticle is synthesized from silver nitrate, polyvinylpyrrolidone and ethylene glycol, followed by adding a viscosifier, hydroxyethyl-cellulose solution, and a surfactant, diethylene glycol. The silver ink is used in an inkjet printer (Fujifilm Dimatix DMP-2800 series) to print silver electrodes on cellulose EAPap. After printing, the electrodes are heat treated at $200^{\circ}C$. The sintered electrodes show that the thickness of the electrodes linearly increases as the number of printing layers increases. The electrical resistivity of the printed electrodes is $23.5{\mu}{\Omega}-cm$. This customized ink can be used in inkjet printer to print complex electrode patterns on cellulose EAPap to fabricate flexible smart actuators, flexible electronics and sensors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1529-1535
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• 2010

For the reliable use of inkjet technology as patterning tools, the jetting of the inkjet dispenser needs to be monitored for real-time detection of any malfunction. We present a self-sensing circuit that can be used to detect jetting failure by measuring electrical signals only. In addition, practical problems involved in the monitoring of inkjets in multinozzle printheads are discussed. In the study, software was developed and presented to demonstrate the feasibility of the proposed method for detecting inkjet jetting failure in a printing system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.4.1-4.1
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• 2011

Recently, circuit printing technology has been considered as a promising alternative to conventional PCB fabrication, for it can greatly reduce the manufacturing costs. Even though printed circuit has many advantages over typical subtractive technology such as fewer processes, it has some disadvantages. The major problems are low adhesion and poor resolution. Efforts to overcome these problems have been mainly focused on ink developments with a limited success. And surface treatments showed some improvements. Therefore, various plasma treatments and primer coatings on plastic substrates have been tested. Plasma treatments using hydrocarbon gases including methane and propane improved the pattern quality of the inkjet printed circuit, which are further improved upon heating of substrate. On the other hand, there is little effect on the adhesion, which is improved only by a special primer coating. The adhesion of inkjet printed circuit has been increased more than 10 times upon treatment. As for the screen printed circuits, the overall effects are less significant since there is some organic binder in the ink. Nonetheless, the treatment has strong positive effects on pattern quality and adhesion. The adhesion of 1 kgf/cm2, which is comparable with those of the conventional PCB circuits, is possible through primer coating for both screen and inkjet printed circuits. The resulting circuit also showed good thermal, mechanical and electrical properties.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.655-659
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• 2006

This paper presents a novel electrostatic drop-on-demand inkjet device featured by a MEMS fabricated pole-type and hole-type nozzle with tube shaped orifice and investigates the feasibility of applying the inkjet device to display fabrication process. The electric voltage signal applied to the ring shaped upper electrode plate, against the hole-shaped ground or pole-shaped ground, referred here pole-type and hole-type nozzle respectively, allows ejection of small 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. It is verified experimentally that the use of the pole type nozzle allows a stable and sustainable micro-dripping mode of droplet ejection for a wider range of applied voltages and of liquid viscosities. This demonstrates a feasibility of electrostatic drop-on-demand inkjet device as a disruptive alternative to conventional print heads such as thermal bubble or piezoelectric inkjet heads.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1552-1555
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• 2005

We have studied the inkjet patterning of synthesized aqueous silver nano-sol on interface-controlled ITO glass substrate. Furthermore, we designed the conductive ink for direct inkjet patterning on bare ITO glass substrate. The first, the highly concentrated polymeric dispersant-assisted silver nano sol was prepared by variation of molecular weight and control of initial nucleation and growth of silver nanoparticles. The high concentration of batch-synthesized silver nano sol was possible to 40 wt%. At the same time the particle size of silver nanoparticles was below $10{\sim}20nm$. The second, the synthesized silver nano sol was inkjet - patterned on ITO glass substrate. The connectivity and width of fine line depended largely on the wettability of silver nano sol on ITO glass substrate, which was controlled by surfactant. The relationship was understood by wetting angle. The fine line of silver electrode as fine as $50{\sim}100\;{\mu}m$ was successfully formed on ITO glass substrate. The last, the direct inkjet-patternable silver nano sol on bare ITO glass substrate was designed also.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1219-1225
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• 2003

According to the increase of lifetime and efficiency, the interest in the pLED has dramatically increased recently because pLED can be applied to large-size and flexible displays. The core process in the manufacture of pLED is the printing process of red, green and blue light emitting polymers (LEP), and inkjet printing method is one of the promising technology to print red, green and blue LEP on glass substrates. In this work, we developed a multi-head inkjet patterning system with 3 heads for each color. The developed inkjet patterning system is composed of the precise positioning system, head controller circuit, real-time ink drop evaluation system, maintenance system, and stable ink supply system. Finally, we investigated the stability and reliability of the system by printing red, green and blue LEP on the dummy substrate.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.128-133
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• 2007

An electrostatic inkjet head can be used for manufacturing processes of large display systems and printed circuit boards (PCB) as well as inkjet printers because an electrostatic field provides an external force which can be manipulated to control sizes of droplets. The existing printing methods such as thermal bubble and piezo inkjet heads have shown difficulties to control the ejection of the droplets for printing applications. Thus, the new inkjet head has been proposed using the electrostatic force. A numerical analysis has been performed to calculate the intensity of the electrostatic field using the Maxwell's equation. Also, experiments have been carried out to investigate the droplet movement using a downward capillary with outside diameter of $500{\mu}m$. Gravity, surface tension, and electrostatic force have been analyzed with high voltages for a drop-on-demand ejection. It has been observed that the droplet size decreases and the frequency of the droplet formation and the velocity of the droplet ejection increase with increasing the intensity of the electrostatic field using high-speed camera.