• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.35-40
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• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.493-499
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• 2007

Polymeric hydrogel particles were fabricated to demonstrate the scale-up possibilities with the Particle Replication In Non-wetting Templates (PRINT) process. A permanently etched, specifically designed master was made on a silicon wafer using conventional photolithography, then reactive ion etching. The master and substrate were used repeatedly to make a large number of identical elastomeric perfluoropolyethers (PFPE) replica molds. The PFPE replica molds were used to fabricate and harvest individual, monodisperse micron-sized particles using the PRINT process. A water-soluble polymer adhesive was used as a sacrificial layer for harvesting particles. Particles were composed of biodegradable poly (ethylene glycol) diacrylate (PEG-diA), and aminoethylacrylate (AEM) and 2-acryloxyethyltrimethyl ammonium chloride (AETMAC) were added to them for improving the uptake of the cells. This study suggested PRINT used to produce the uniformed and shape specific biodegradable polymer is the effective technique for the non viral vector for the drug and the gene delivery.

• Journal of Korea Spatial Information System Society
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• v.10 no.3
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• pp.79-91
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• 2008

Recently, with highly Interest In Location-Based Service(LBS) utilizing location data of moving objects, the GALIS(Gracefully Aging Location Information System) which is a cluster-based distributed computing architecture was proposed as a more efficient location management system of moving objects. In the SLDS(Short-term location Data Subsystem) which Is a subsystem of the GALIS, since the SDP(Short-term Data Processor) Master transmits current location data and queries to every SDP Worker, the SDP Master reassembles and sends query results produced by SDP Workers to the client. However, the services are suspended during the SDP Master under failure and the response time to the client is increased if the load is concentrated on the SDP Master. Therefore, in this paper, the extended SLDS was designed and implemented to solve these problems. Though one SDP Master is under failure, the other can provide the services continually, and so the extended SLDS can guarantee the high reliability of the SLDS. The extended SLDS also can reduce the response time to the client by enabling two SDP Masters to perform the distributed query processing. Finally, we proved high reliability and high availability of the extended SLDS by implementing the current location data storage, query processing, and failure takeover scenarios. We also verified that the extended SLDS is more efficient than the original SLDS through the query processing performance evaluation.

• Polymer(Korea)
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• v.28 no.4
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• pp.305-313
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• 2004

A vacuum pressure-difference technique for making a nano-precision replica is investigated for various applications. Master patterns for replication were fabricated using a nano-replication printing (nRP) process. In the nRP process, any picture and pattern can be replicated from a bitmap figure file in the range of several micrometers with resolution of 200nm. A liquid-state monomer is solidified by two-photon absorption (TPA) induced by a femto-second laser according to a voxel matrix scanning. After polymerization, the remaining monomers were removed simply by using ethanol droplets. And then, a gold metal layer of about 30nm thickness was deposited on the fabricated master patterns prior to polydimethylsiloxane molding for preventing bonding between the master and the polydimethylsiloxane mold. A few gold particles attached on the polydimethylsiloxane stamp during detaching process were removed by a gold selecting etchant. After fabricating the polydimethylsiloxane mold, a nano-precision polydimethylsiloxane replica was reproduced. More precise replica was produced by the vacuum pressure-difference technique that is proposed in this paper. Through this study, direct patterning on a glass plate, replicating a polydimethylsiloxane mold, and reproducing polydimethylsiloxane replica are demonstrated with a vacuum pressure-difference technique for various micro/nano-applications.

• Laser Solutions
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• v.6 no.2
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• pp.35-41
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• 2003

In this study, manufacturing of polymer master and mold insert for micro injection molding was investigated. Ablation by excimer laser radiation could be used successfully to make 3-D microstructure of PET. The mechanism for ablative decomposition of PET with KrF excimer laser(λ: 248nm, pulse duration: 5ns) was explained by photochemical process. And this process showed PET to be adopted in polymer master for nickel mold insert. Nickel electroforming by using laser ablated PET master was preferable for replication method. Finally, it was shown that excimer laser ablation can substitute for X-ray lithography of LIGA process in microstructuring.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.247-247
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• 2012

Plasmon subwavelength nanostructures enable the structurally modulated color due to the resonance conditions for the specific wavelength range of light with the nanoscale hole arrays on a metal layer. While the unique properties offered from a single layer of metal may open up the potential applications of integrated devices to displays and sensors, fabrication requirements in nanoscale, typically on the order of or smaller than the wavelength of light in a corresponding medium can limit the cost-effective implementation of the plasmonic nanostructures. Simpler nanoscale replication technologies based on the soft lithography or roll-to-roll nanoimprinting can introduce economically feasible manufacturing process for these devices. Such replication requires an optimal design of a master template to produce a stamp that can be applied for a roll-to-roll nanoimprinting. In this paper, a master mold with subwavelength nanostructures is fabricated and optimized using focused ion beam for the applications to nanoimprinting process. Au thin film layer is deposited by sputtering on a glass that serves as a dielectric substrate. Focused ion beam milling (FIB, JEOL JIB-4601F) is used to fabricate surface plasmon subwavelength nanostructures made of periodic hole arrays. The light spectrum of the fabricated nanostructures is characterized by using UV-Vis-NIR spectrophotometer (Agilent, Cary 5000) and the surface morphology is measured by using atomic force microscope (AFM, Park System XE-100) and scanning electron microscope (SEM, JEOL JSM-7100F). Relationship between the parameters of the hole arrays and the corresponding spectral characteristics and their potential applications are also discussed.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.13-20
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• 2004

Manufacturing process for the microfluidic device can include such sequential steps as master fabrication, electroforming, and injection molding. The laser ablation using masks has been applied to the fabrication of channels in microfluidic devices. In this study, manufacturing of polymer master and mold insert for micro injection molding was investigated. Ablation of PET (polyethylene terephthalate) by the excimer laser radiation could be used successfully to make three dimensional master fur nickel mold insert. The mechanism fur ablative decomposition of PET with KrF excimer laser $({\lambda}: 248 nm, pulse duration: 5 ns)$ was explained by photochemical process, while ablation mechanism of PMMA (polymethyl methacrylate) is dominated by photothermal process, the .eaction between PC (polycarbonate) and KrF excimer laser beam generate too much su.face debris. Thus, PET was adopted in polymer master for nickel mold insert. Nickel electroforming using laser ablated PET master was preferable for replication method. Finally, it was shown that excimer laser ablation can substitute for X-ray lithography of LIGA process in microstructuring.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.367-370
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• 2003

In this study, application of SAM (self-assembled monolayer) to nano replication process as an anti-adhesion layer was presented to reduce the surface energy between the nano mold and the replicated polymeric nano patterns. The electron beam lithography was used for master nano patterns and the electorforming process was used to fabricate the nickel nano stamper. Alkanethiol SAM as an anti-adhesion layer was deposited on metallic nano stamper using solution deposition method. To analyze wettability and adhesion force of SAM, contact angle and LFM (Lateral Force Microscopy) were measured at the actual processing temperature and pressure for the case of nano compression molding and at the actual UV dose for the case of nano UV molding. It was found that the surface energy due to SAM deposition on the nickel nano stamper markedly decreased and the quality of SAM on the nickel stamper maintained under the actual molding environments.

• Transactions of Materials Processing
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• v.20 no.1
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• pp.23-28
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• 2011

For the fabrication of nano patterned products manufacturing a nano patterned mold is needed in advance. The nano patterned stamper was fabricated by electroforming the AAO master with nickel. The surface of nickel-plated stamper had nano-patterned holes with the diameter of 73 nm and the depth of 83 nm. Hot embossing was used for forming P3HT sheet and the process factors of hot embossing were closer as pressure, temperature and time. In the present paper hot embossing experiments were performed to find the main process conditions to affect the replication ratio of nano patterns on surface of P3HT sheet. As a result, main contributing factors for the replication ratio of hot embossed pattern could be sequentially enumerated as pressure, temperature and time.