• Proceedings of the KSME Conference
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• 2008.11a
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• pp.30-34
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• 2008

The transfer assembly (or transfer printing) technique is a promising method for fabricating multi-scale structures on various substrates including semiconductors and polymers, and has been applied to fabrication of flexible devices with superior performance to conventional organic flexible devices. The mechanical behaviors of the structures fabricated by the transfer assembly is a very important information for design and reliability evaluation purpose, but the measurement of the behaviors is difficult since their critical-dimensions are very tiny. In this study, Au films with nano-scale thickness were fabricated on a silicon substrate and their mechanical properties were measured using micro-tensile test. The Au films on the silicon substrate were then transferred to a PDMS substrate using the transfer assembly technique. Self-assembled monolayer (SAM) with a thiol group was used to enhance the transfer of Au films, and the mechanical behaviors were characterized using wrinkle-based test. The test results from micro-tensile and wrinkle-based test are compared to each other, and their implication to the transfer assembly technique is discussed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.19.1-19.1
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• 2010

The process of manufacturing printed electronics using printing technology is attracting attention because its process cost is lower than that of the conventional semiconductor process. This technology, which offers both a lower cost and higher productivity, can be applied in the production of organic TFT (thin film transistor), solar cell, RFID(radio frequency identification) tag, printed battery, E-paper, touch screen panel, black matrix for LCD(liquid crystal display), flexible display, and so forth. In general, in order to implement printed electronics, narrow width and gap printing, registration of multi-layer printing by several printing units, and printing accuracy of under $20\;{\mu}m$ are all required. These electronic products require high precision to the degree of tens of microns - in a large area with flexible material, and mass productivity at low cost. As such, the roll-to-roll printing process is attracting attention as a mass production system for these printed electronic devices. For the commercialization of this process, two basic electronic ink technologies, such as conductive ink and polymers, and printing equipment have to be developed. Therefore, this paper addressed basis design and test to develop fine patterning equipment employing the roll-to-roll printing equipment and electronic ink.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.103-110
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• 2023

The study aimed to enhance the properties of polylactic acid (PLA), a biodegradable and biocompatible substitute for fossil-based plastics. Since the applicability of PLA has been limited because of its toughness and brittleness, microfibrillated cellulose (MFC) and propolis were introduced into PLA. As a result, the PLA film with MFC/propolis showed significant improvements in mechanical strength, elongation, and storage modulus, while also experiencing a decrease in the glass transition temperature. Additionally, the presence of polyphenols in propolis led to a reduction in light transmittance in the UV wavelength range. These enhancements are attributed to MFC tightly bonding with PLA polymers, and propolis acting as a plasticizer and mediator between MFC and PLA, preventing agglomeration. These reinforced PLA films have the potential to be used in flexible packaging for light-sensitive products.

• Polymer(Korea)
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• v.31 no.1
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• pp.37-46
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• 2007

Fully or nearly fully 6- [4- (4'- (nitrophenylazo)phenoxycarbonyl)]pentanoated polysaccharide derivatives were synthesized by reacting cellulose, amylose, chitosan, chitin, alginic acid, pullulan or amylopectin with 6- [4- (4'- (nitrophenylazo)phenoxy) ] pentanoyl chloride (NA6C) and their thermotropic liquid crystalline behaviors were investigated. Like in the case of NA6C, all the polysaccharide derivatives formed monotropic nematic phases, suggesting that the mesophase structure of the polysaccharide derivatives is dertermined by the mesogenic side groups and not by the polysaccharide backbone. This is the first report of polysaccharide derivatives, except cellulose derivative, that form thermotropic nematic phases. The thermal stability and degree of order of the nematic phases observed for poly saccharide derivatives were significantly different from those reported for the polymers in which the azobenzene groups are attached to flexible or rigid backbones through flexible spacers. The results were discussed in terms of the difference in the arrangement of the main and side chains and the flexibility of the main chain.

• Composites Research
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• v.27 no.6
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• pp.242-247
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• 2014

The fabrication of flexible electrodes coated on the surface of a dielectric elastomer film, which is a type of electroactive polymer (EAP), was carried out. Controlled amounts of Xylitol powder were added (10, 30, 50 and 70 wt%) to the commercial conductive polymer (PEDOT:PSS) to enhance resilience of the electrode. To check resilience of the fabricated composite electrodes, tensile tests were carried out using silicone films coated with the polymer electrodes. From the test results, it was found that 70 wt% Xylitol containing conductive polymer had excellent elongation and high failure strains. Furthermore, surface of the silicone film was uniformly polished with various abrading papers to enhance the wettability of the conductive polymers on the surface of the silicone film. It was found that the silicone film polished with #120 abrading paper had the best wettability and guaranteed excellent bonding behavior.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.27.2-27.2
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• 2011

Polymer electronics is the one of the most promising way to realize the flexible electronics and many studies made remarkable progress to achieve the improvement in performance of polymer electronics comparable to current silicon-based technology. PBTTT is conjugated semiconducting polymer with highly ordered, chain-extended crystalline microstructures and shows high field effect mobilities above 0.1 $cm^2/Vs$. We studied PBTTTs FETs phase and explored methods to control channel interface in various device structures. Especially, in PBTTTs' unique nano-ribbon phase, we could obtain high mobilities of up to 0.4 $cm^2/Vs$, which was not reached before. Alignment of PBTTTs film was carried out using zone casting and anisotropy of mobilities in parallel and perpendicular to the polymer chain direction was investigated. Optical anisotropy in aligned nano-ribbon PBTTT FETs was also studied using a polarized optical absorption.

• Textile Coloration and Finishing
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• v.5 no.2
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• pp.109-116
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• 1993

Synthesis and liquid-crystallinites of thermotropic polyamides and copolyamides were investigated. Thermotropic polyamides and copolyamides containing a flexible spacer in the backbone were obtained by the two or three components melt polycondensations of 4,4'-dicarboxy-${\alpha}$${\omega}$-diphenoxy alkane as an A components, 4,4'-diacetoamido-3,3' dimethoxybiphenyl as a B, 1,4-diacetoamido-benzene (diacetylated p-phenylenediamine) was used as another amide-group-forming minomer. The content of the amide groups in the thermotropic polyamide and Copolyamide widely varied depending on the structure of the amide-group forming diacetoamido monomers. A polymer (9CLDI) showed a typical nematic texture between 218$^{circle}C$ ($T_m$) and 345$^{circle}C$($T_i$) The melting points of the members of this series of polymers increased with decreasing methylene spacer. The polymer structure and mesmorphic nature were examined by solid and solution ${^13}C$-NMR spectroscopy, cross polarizing microscopy with a hot stage.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1986.12a
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• pp.510.1-510
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• 1986

Many enzymes require the participation of readily dissociable coenzymes as NAD for thir catalytic activities. The continuous utilization of the enzymes requires the retention and regeneration of the coenzymes. For this purpose, several kinds of macromolecular NAD derivatives have been prepared by covalently attaching NAD to watersoluble polymers. We have prepared poly (ethylene glycol)-bound NAD (PEG-NAD) by coupling N$\^$6/-(2-carboxyethyl)-NAD to one terminal of ${\gamma}$ $\omega$-diaminoly (ethylene glycol) (Mr 3000) with water-soluble carbodiimide. PED-NAD thus obtained has one NAD moiety located at a terminal of the linear, flexible and hydrophilic chain of poly (ethylene glycol). PED-NAD has good coenzyme activity for various dehydrogenases and is applicable in a continuous enzyme reactor. To use these macromolecular NAD derivatives in an enzyme reactor, it si necessary to understand the behavior of the system in which the reactions of dehydrogenases are coupled by the recycling of the NAD derivative. We investigated the kinetic properties of a continuous enzyme reactor containing lactate dehydrogenase, alcohol dehydrogenase and PEG-NAD. The steady-state behavior of the enzyme reactor is explained by a simple kinetic model.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.439-444
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• 2018

This paper presents a numerical study on the behavior of continuous hollow steel beam strengthened using carbon fiber reinforced polymers (CFRP). Most previous studies on the CFRP strengthening of steel beams have been carried out on the steel beams with simple boundary conditions. No independent study, to the researcher's knowledge, has studied on the CFRP strengthening of square hollow section (SHS) continuous steel beam. However, this study explored the effect of the use of adhesively bonded CFRP flexible sheets on the behavior of the continuous SHS steel beams. Finite Element Method (FEM) has been employed for modeling. Eleven specimens, ten of which were strengthened using CFRP sheets, were analyzed under different coverage length, the number of layers, and the location of CFRP composite. ANSYS software was used to analyze the SHS steel beams. The results showed that the coverage length, the number of layers, and the location of CFRP composite are effective in increasing the ultimate load capacity of the continuous SHS steel beams. Application of CFRP composite also caused the ductility increase some strengthened specimens.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.17-20
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• 2008

This study investigated the fundamental properties and cracking shapes of mortar for the floor after Mock-up test with FRP as wastes of crafts. For the flowability of fresh mortar without FRP, it was favorable compared with fresh mortar using FRP, and the drop time at O-Lot was similar to the flowability. For the compressive strength of fresh mortar with FRP, it was increased about 10% compared with plain. The flexible strength was also increased on fresh mortar with FRP. On the cracking shape, there was many penetrated crack in all directions on plain. In the case that FRP was used, it seemed to have excellent resistance to the crack occurrence because there was no directive crack at a limited part.