• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.4
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• pp.262-268
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• 2021

For the past several decades, various next-generation patterning methods have been developed to obtain well-designed nano-to-micro structures, such as imprint lithography, nanotransfer printing (nTP), directed self-assembly (DSA), E-beam lithography, and so on. Especially, nTP process has much attention due to its low processing cost, short processing time, and good compatibility with other patterning techniques in achieving the formation of high-resolution functional patterns. To transfer functional patterns onto desirable substrates, the use of soft materials is required for precise replication of master mold. Here, we introduce a simple and practical nTP method to create highly ordered structures using various polymeric replica materials. We found that polymethyl methacrylate (PMMA), polystyrene (PS), and polyvinylpyridine (PVP) are possible candidates for replica materials for reliable duplication of Si master mold based on systematic analysis of pattern visualization. Furthermore, we successfully obtained well-defined metal and oxide nanostructures with functionality on target substrates by using replica patterns, through deposition and transfer process. We expect that the several candidates of replica materials can be exploited for effective nanofabrication of complex electronic devices.

• Korean Journal of Veterinary Research
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• v.63 no.2
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• pp.15.1-15.5
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• 2023

The hepatitis A virus (HAV) induces severe acute liver injury and is adapted to human and monkey cell lines but not other cells. In this study, the HAV was inoculated into porcine kidney (PK-15) cells to determine its infectivity in porcine cells. The growth pattern of the HAV in PK-15 cells was compared with its growth pattern in fetal rhesus kidney (FRhK-4) cells. The growth of HAV was less efficient in PK-15 cells. In conclusion, HAV replication was verified in PK-15 cells for the first time. Further investigations will be needed to identify the HAV-restrictive mechanisms in PK-15 cells.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.999-1005
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• 2004

A new stamp fabrication technique for the soft lithography has been developed in the range of several microns by means of a nano-replication printing (nRP) process. In the nRP process, a figure or a pattern can be replicated directly from a two-tone bitmap figure with nano-scale details. A photopolymerizable resin was polymerized by the two-photon absorption which was induced by a femtosecond laser. After the polymerization of master patterns, a gold metal layer (about 30 ㎚ thickness) was deposited on the fabricated master patterns for the purpose of preventing a join between the patterns and the PDMS, then the master patterns were transferred in order to fabricate a stamp by using the PDMS (poly-dimethylsiloxane). In the transferring process, a few of gold particles, which were isolated from the master patterns, remained on the PDMS stamp. A gold selective etchant, the potassium iodine (KI) was employed to remove the needless gold particles without any damage to the PDMS stamp. Through this work, the effectiveness of the nRP process with the PDMS molding was evaluated to make the PDMS stamp with the resolution of around 200 ㎚.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.153-158
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• 2007

Recently nano imprint lithography to fabricate photonic crystal on polymer is preferred because of its simplicity and short process time and ease of precise manufacturing. But, the technique requires the precise mold as an imprinting tool for good replication. These molds are made of the silicon, nickel and quartz. But this is not desirable due to complex fabrication process, high cost. So, we describe a simple, precise and low cost method of fabricating PDMS stamp to make the photonic crystals. In order to fabricate the PDMS mold, we make the original pattern with designed hole array by finding the optimal electron beam writing condition. And then, we have tried to fabricate PDMS mold by the replica molding with ultrasonic vibration and pressure system. We have used the cleaning process to solve the detaching problem on the interface. Using these methods, we acquired the PDMS mold for photonic crystals with characteristics of a good replication. And the accuracy of replication shows below 1% in 440nm at diameter and in 610nm at lattice constant by dimensional analysis by SEM and AFM.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.30-35
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• 2009

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.7-13
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• 2011

According to increasing of data transfer rate, printed circuit board (PCB) is required improvement of transmission speed. Optical PCB and its packaging technology can be one of the solutions that overcome the limitations of conventional electrical PCB. The data transmission capacity will be increased 10 Tbps at 2015. To this end, studies on various OPCB technologies are being conducted. For cost-effective and high- performance OPCB, studies of optical coupling by polymer replication process are conducted. In this work, optical waveguide and optical fiber array block were sequentially fabricated by polymer pattern replication method. Using this method we successfully demonstrate low loss optical fiber coupling between optical waveguide and optical fiber arrays. And researches on flip chip bonding process and using electro-optic connectors for packaging are conducted.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.17-21
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• 2005

High-density image sensors have microlens array to improve photosensitivity. It is conventionally fabricated by reflow process. The reflow process has some weak points. UV imprinting process can be proposed as an alternative process to integrate microlens array on photodiodes. In this study, the UV imprionting process to integrate microlens array on image sensor was developed using W transparent flexible mold and simulated image sensor substrate. The UV transparent flexible mold was fabricated by replicating master pattern using siliconacrylate photopolymer. The releasing property and shape accuacy of siliconacrylate mold was analysed. After UV imprinting process, replication quality and align accuracy was analysed.

• Transactions of the Society of Information Storage Systems
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• v.2 no.2
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• pp.91-95
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• 2006

High-density image sensors rave microlens array to improve photosensitivity. It is conventionally fabricated by reflow process. The reflow process has some weak points. UV imprinting process can be proposed as an alternative process to integrate microlens array on photodiodes. In this study, the UV imprionting process to integrate microlens array on image sensor was developed using UV transparent flexible mold and simulated image sensor substrate. The UV transparent flexible mold was fabricated by replicating master pattern using siliconacrylate photopolymer. The releasing property and shape accuacy of siliconacrylate mold was analysed. After UV imprinting process, replication quality and align accuracy was analysed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.237-240
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• 2005

The demand of micro electrical mechanical system (MEMS) bio/chemical sensor is rapidly increasing. To prevent the contamination of sensing area, a filtration system is required in on-chip total analyzing MEMS bio/chemical sensor. A nano-filter was mainly applied in some application detecting submicron feature size bio/chemical products such as bacteria, fungi and so on. We suggested a simple nano-filter fabrication process based on replication process. The mother pattern was fabricated by holographic lithography and reactive ion etching process, and the replication process was carried out using polymer mold and UV-imprinting process. Finally the nano-filter is obtained after removing the replicated part of metal deposited replica. In this study, as a practical example of the suggested process, a nano-dot array was replicated to fabricate nano-filter fur bacteria sensor application.

• The Korean Journal of Zoology
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• v.25 no.2
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• pp.55-62
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• 1982

DNA synthesis, unscheduled DNA synthesis, excision of pyrimidine dimers and phtoreactivation were determined in UV-irradiated differentiating muscle cells at various times of primary culture of 12 day chick embryos and results obtained were as follows. The rates of UV-induced unscheduled DNA synthesis were increased as increase of UV dose. And the rates were gradually decreased as the increase of time after culture, but at higher doses the decreasing tendency was remarkable. The patterns of DNA replication were changed drastically as a function of time so that in the seven day cultures the rate of $^3$H-thymidine incorporation was found to be 0.2% of the original activity. The pattern of inhibition of DNA replication by UV damage demonstrated that in cells of earlier stages there were no remarkable changes, but in cells of later stages there was significant fluctuation. Photoreactivation and the excision of pyrimidine dimer in the one day cultures showed that photoreactivation occurred immediately after UV-irradiation, but excision of pyrimidine dimer was gradually and slowly occurred. These results indicate that the differentiation of embryonic muscle cells accompanies the gradual reduction of DNA replication and unscheduled DNA synthesis, and that the photoreactivation is rapid process compared to excision repair.