• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.123-130
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• 2016

In this paper, a novel flexible microfluidic metamaterial absorber is proposed for remote chemical sensor applications. The proposed metamaterial absorber consists of a periodic of split-ring-cross resonators(SRCRs) and a microfluidic channel. The SRCR patterns are inkjet-printed using silver nanoparticle inks on paper. The microfluidic channels are laser-etched on polydimethylsiloxane(PDMS) material. The proposed absorber can detect change of the effective permittivity at different liquids. Therefore, the absorber can be used for a remote chemical sensor by detecting change of the resonant frequencies. The performance of the proposed absorber is demonstrated with full-wave simulation and measurement results. The experimental results shows that the resonant frequency is 10.49 GHz at the empty channel. When ethanol and DI-water are injected into the channel, the resonant frequencies are 10.04 GHz and 8.9 GHz, respectively.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.498-503
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• 2013

Over the past decade, the feasibility of using ink-jet printing for the decoration of porcelain tiles has been explored, and significant advances have been made regarding the technologies underlying printing system and materials. An ink-jet printing system for porcelain tiles has many advantages compared with a conventional printing system, including the following: (1) it is a digital process; (2) it uses non-contact printing; (3) it allows random image generation; (4) it is a highly efficient process (reduced production cost); (5) it offers massive and continuous production; and (6) it uses inorganic pigment colorants. For these reasons, ink-jet printing systems for porcelain tiles have been commercialized and are at present rapidly spreading toceramics-leading countries such as Spain, Italy, China and Japan. We also developed a proprietary system involving a piezo-electric drop-on-demand method and an ink-circulation step. The resolution of this system is greater than 360 dpi after a heat treatment and the maximum printable width is 600 mm, even when setting the printing head unit with four digital colors (cyan, magenta, yellow, and black). In addition, we systematically developed ceramic colorant-containing inks and tile-printing technology applicable to our ink-jet printing system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.511-511
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• 2007

Low-emissivity (low-e) coatings with visible transparency have attracted increased interest m reducing heat radiation loss through window panes from ecological and sustainable aspects. $TiO_2$-silver transparent thin films for low-e have good properties for UV and IR blocking as well as photocatalyst compared to that with commercial UV blocking films such as fluorine doped oxide (FTO), antimony doped tin oxide (ATO), etc. In this study, transparent $TiO_2$-silver thin films were prepared by successive ink-jet printing of commercial nano silver and $TiO_2$ sol. The $TiO_2$ sol, as ink for ink-jet printing, were synthesized by hydrothermal process in the autoclave externally pressurized with $N_2$ gas of 200 bar at $120^{\circ}C$ for 10 hrs. The synthesized $TiO_2$ sols were all formed with brookite phase and their particle size was several to 30 nm. At first nano sized silver sol was coated on glass substrate, after that $TiO_2$ sol was coated by ink-jet printing. With increasing coating thickness of $TiO_2$-silver multilayer by repeated ink-jet coating, the absorbance of UV region (under 400nm) and IR region (over 700nm) also increase reasonably, compared to that with commercial UV blocking films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.105-105
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• 2006

IT 산업 및 반도체 산업이 발전함에 따라 초소형, 고집적화 시스템의 요구에 대응하기 위해서 고해상도 및 고정밀의 패턴 구현에 관한 많은 연구가 진행되고 있다. 이러한 연구는 각종 산업제품의 PCB(Printed Circuit Board) 및 디스플레이 장치인 PDP(Plasma Display Panel), LCD(Liquid Crystal Display) 등에 적용되어 널리 응용되고 있다. 현재 널리 사용되는 인쇄 회로 기판은 마스킹 후 선택적 에칭 방식을 적용하여 금속 배선을 형성하는 방식을 적용하고 있다. 이러한 방식은 설계가 변경될 경우 마스크를 다시 제작해야 하는 번거로움이 있어 설계 변경이 용이하지 않고 더욱 길어진 생산시간의 증가로 인하여 생산성 및 집적도가 떨어지게 된다. 따라서 최근에는 이러한 한계를 극복하기 위한 방안이 여러 가지 측면에서 시도되고 있으며, 그 중에서도 Inkjet Printing 기술에 대한 관심이 증가하고 있다. 본 연구에서는 Inkjet Printing 방식을 적용하여 금속 배선을 형성하고 선폭과 두께의 오차를 줄여 배선의 Tolerance 를 개선할 수 있는 방안을 제안하였다. Inkjet Printing 방식을 이용한 기존의 금속 배선 형성은 고해상도의 DPI(Dot Per Inch)에서 잉크 액적이 뭉치는 Bulge 현상이 발생되어 원하는 형상 및 배선의 폭을 구현하는데 어려움이 있었다. Bulge 현상은 배선의 불균일성을 야기할 뿐만 아니라 근접한 배선의 간섭에도 영향을 미처 금속 배선의 기능을 할 수 없는 단점을 발생시킨다. 따라서 본 연구에서는 이러한 Bulge 현상을 줄이고 배선간의 간섭을 방지하여 원하는 배선을 용이하게 형성할 수 있는 순차적 인쇄 방식을 적용하였다. 본 연구에서는 노즐직경 35um 의 Inkjet Head 와 나노 Ag 입자 잉크를 사용하여 Glass 표면 위에 배선을 형성하고 배선의 폭과 두께를 측정하였다. 또한 순차적 인쇄 방식을 적용하여 700DPI 이상의 고해상도에서 나타날 수 있는 Bulge 현상이 감소하였음을 관찰하였으며 금속 배선의 Tolerance를 10%내외로 유지할 수 있음을 확인하였다.

• Journal of the Korean institute of surface engineering
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• v.40 no.4
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• pp.190-196
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• 2007

Dye sensitized solar cells(DSSC) are the most promising future energy resource due to their high energy efficiency, low production cost, and simple manufacturing process. But one problem in DSSC is short life time compared to silicon solar cells. This problem occurred from photocatalytic degradation of dye material by nanometer sized $TiO_2$ particles. To prevent dye degradation as well as to increase its life time, the transparent coating film is needed for UV blocking. In this study, we synthesized nanometer sized $TiO_2$ particles in sols by increasing its internal pressure up to 200 bar in autoclave at $120^{\circ}C$ for 10 hrs. The synthesized $TiO_2$ sols were all formed with brookite phase and their particle size was several nm to 30 nm. Synthesized $TiO_2$ sols were coated on the backside of fluorine doped tin oxide(FTO) glass by ink jet printing method. With increasing coating thickness by repeated ink jet coating, the absorbance of UV region (under 400 nm) also increases reasonably. Decomposition test of titania powders dispersed in 0.1 mM amaranth solution covered with $TiO_2$ coating glass shows more stable dye properties under UV irradiation, compared to that with as-received FTO glass.

• Journal of Sensor Science and Technology
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• v.33 no.1
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• pp.24-29
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• 2024

Inkjet printing technology is used to mass-produce displays and electrochemical sensors by dropping tens of pico-liters or less of specific-purpose ink through nozzles, just as ink is sprayed and printed on paper. Unlike the deposition method for vaporizing material in a vacuum, inkjet printing technology can be used for processing even under general atmospheric pressure and has a cost advantage because the material is dissolved in a solvent and used in the form of ink. In addition, because it can only be printed on the desired part, masks are not required. However, a technical shortcoming is the difficulty for commercialization, such as uniformity for forming the thickness and coffee ring effect. As sizes of devices decrease, the need to print electrodes with precision, thinness, and uniformity increases. In this study, we improved the printing and processing conditions to form a homogeneous electrode using Ag ink (DGP-45LT-15C) and applied this for patterning to fabricate a heat sensor. Upon the application of voltage to the heat sensor, the model with an extended width exhibited superior heat performance. However, in terms of sheet resistance, the model yielded an equivalent value of 21.6 Ω/□ compared to the ITO.

• Journal of Powder Materials
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• v.31 no.2
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• pp.169-179
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• 2024

Colloidal quantum dot (QDs) have emerged as a crucial building block for LEDs due to their size-tunable emission wavelength, narrow spectral line width, and high quantum efficiency. Tremendous efforts have been dedicated to improving the performance of quantum dot light-emitting diodes (QLEDs) in the past decade, primarily focusing on optimization of device architectures and synthetic procedures for high quality QDs. However, despite these efforts, the commercialization of QLEDs has yet to be realized due to the absence of suitable large-scale patterning technologies for high-resolution devices., This review will focus on the development trends associated with transfer printing, photolithography, and inkjet printing, and aims to provide a brief overview of the fabricated QLED devices. The advancement of various quantum dot patterning methods will lead to the development of not only QLED devices but also solar cells, quantum communication, and quantum computers.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.255-264
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• 2013

Cobalt aluminate ($CoAl_2O_4$) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, $CoAl_2O_4$ is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, $CoAl_2O_4$ pigments were synthesized by polymerized complex method and solid state reaction. Then $CoAl_2O_4$ pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE $L^*a^*b^*$. The XRD patterns of $CoAl_2O_4$ show single phase spinel structure. The particle size of $CoAl_2O_4$ measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained $CoAl_2O_4$ pigments could be confirmed through CIE $L^*a^*b^*$ measurement.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.115-122
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• 2019

Electric arc furnace dust (EAFD), which is a dust waste generated in the steel manufacturing process, contains heavy metals. Recently, researches of recycling a large amount of valuable metals such as zinc and iron in EAFD are being actively carried out. In this study, EAFD is used as a substitute for cobalt in blue ceramic pigments without any pretreatment. Then, the synthesized blue ceramic pigment using EAFD was micronized and formulated as a ceramic ink for inkjet printer. The particle size distribution, crystal structure and color characteristics during the micronization process were investigated for the development of ceramic ink. $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments showed excellent blue coloric properties and monomodal distribution through micronization process. The average particle size of $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments after 3 hours of milling was $0.271{\mu}m$, which is smaller than $0.303{\mu}m$, which is the average particle size of $CoAl_2O_4$ ceramic pigments without EAFD after 5 hours of milling. Especially, it was confirmed that $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments showed a color difference (${\Delta}E{^*}_{ab}$) value of 5.67, which smaller than ${\Delta}E{^*}_{ab}$ value of $CoAl_2O_4$ during micronization. These results show that EAFD can be used as a raw material for a blue ceramic pigment by replacing expensive cobalt without any pretreatment.