• Korean Chemical Engineering Research
• /
• v.59 no.4
• /
• pp.639-643
• /
• 2021

In this study, fluorinated ethylene propylene (FEP) nanoparticle as an adhesive for fabricating a three-dimensional multilayered microfluidic device was studied. The formation of evenly distributed FEP nanoparticles layer with 3 ㎛ in thickness on substrates was achieved by simple spin coating of FEP dispersion solution at 1500 rpm for 30 s. It is confirmed that FEP nanoparticles transformed into a hydrophobic thin film after thermal treatment at 300 ℃ for 1 hour, and fabricated polyimide film-based microfluidic device using FEP nanoparticle was endured pressure up to 2250 psi. Finally, a three-dimensional multilayered microfluidic device composed of 16 microreactors, which are difficult to fabricate with conventional photolithography, was successfully realized by simple one-step alignment of FEP coated nine polyimide films. The developed three-dimensional multilayered microfluidic device has the potential to be a powerful tool such as high-throughput screening, mass production, parallelization, and large-scale microfluidic integration for various applications in chemistry and biology.

• Journal of the Korean Applied Science and Technology
• /
• v.40 no.1
• /
• pp.71-80
• /
• 2023

Silver paste is a valuable electrode material for electronic device applications because it is easy to handle with relatively low heat treatment. This study treated the electrode surface using an atmospheric-pressure plasma jet on the silver-paste electrode. This plasma jet was generated in an argon atmosphere using a high voltage of 5.5 to 6.5 kV with an operating frequency of 11.5 kHz. Plasma-jet may be more beneficial to the printing process by performing it at atmospheric pressure. The electrode surface becomes hydrophilic quickly and contact angle variation is observed on the electrode surface as a function of plasma treatment time, applied voltage, and gas flow rate. Also, there was no deviation in the contact angle after the plasma treatment in the large-area sample, that means a uniform result could be obtained regardless of the substrate size. The outcomes of this study are expected to be very useful in forming a stacked structure in the manufacture of large-area electronic devices and future applications.

• Journal of the Korean Vacuum Society
• /
• v.14 no.2
• /
• pp.78-83
• /
• 2005

Nanometric crystalline silicon (no-Si) embedded in dielectric medium has been paid attention as an efficient light emitting center for more than a decade. In nc-Si, excitonic electron-hole pairs are considered to attribute to radiative recombination. However the surface defects surrounding no-Si is one of non-radiative decay paths competing with the radiative band edge transition, ultimately which makes the emission efficiency of no-Si very poor. In order to passivate those defects - dangling bonds in the $Si:SiO_2$ interface, hydrogen is usually utilized. The luminescence yield from no-Si is dramatically enhanced by defect termination. However due to relatively high mobility of hydrogen in a matrix, hydrogen-terminated no-Si may no longer sustain the enhancement effect on subsequent thermal processes. Therefore instead of easily reversible hydrogen, phosphorus was introduced by ion implantation, expecting to have the same enhancement effect and to be more resistive against succeeding thermal treatments. Samples were Prepared by 400 keV Si implantation with doses of $1\times10^{17}\;Si/cm^2$ and by multi-energy Phosphorus implantation to make relatively uniform phosphorus concentration in the region where implanted Si ions are distributed. Crystalline silicon was precipitated by annealing at $1,100^{\circ}C$ for 2 hours in Ar environment and subsequent annealing were performed for an hour in Ar at a few temperature stages up to $1,000^{\circ}C$ to show improved thermal resistance. Experimental data such as enhancement effect of PL yield, decay time, peak shift for the phosphorus implanted nc-Si are shown, and the possible mechanisms are discussed as well.

• Journal of Periodontal and Implant Science
• /
• v.29 no.2
• /
• pp.311-326
• /
• 1999

This study was investigated to observe the effect of Treponema denticola(TDC) and Treponema lecithinolyticum(TLC) on cultured human periodontal ligament cells. Several experiments were performed including MTT test for the inhibition effect of cell proliferation, LDH test for the cytotoxicity , gelatin zymography for the gelatinase activation and observation of cell morphology change using the phase-contrast microscopy. The results were as follows. 1. The effect of concentration on cell proliferation with time showed an inhibitory effect at high concentration $(150{\mu}g/well)$ for TLC and at low concentration( $9.4{\mu}gwell$ ) for TDC. 2. The effect of time on cell proliferation with concentration showed an inhibitory effect at $150{\mu}g/well$ on 2-day incubation for TLC and at $9.4{\mu}g/well$ on 2-day incubation for TDC. 3. The effect of heat-treated TDC and TLC on the inhibition of cell proliferation showed the difference in the heat-treated group compared to the non-heat treated group for TDC, whereas no difference was found for TLC. 4. The morphological changes which were observed from the phase-contrast microscopy showed the difference in the test group compared to the control group. The loss of spindle-like appearance, cell-to-cell detachment and inhibition of cell proliferation were observed. 5. There was no difference of the cytotoxicity effect between the test group and the control group in the LDH test. 6. The active form of progelatinase A with molecular weight 72kDa was activated in both TDC and TLC on the gelatin zymography. Regarding to the above results, TDC and TLC have an effect on periodontal ligament cells by playing an inhibitory role in cell proliferation and appears to activate progelatinase A which degrades type IV collagen.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.63 no.3
• /
• pp.239-247
• /
• 2018

Soybean produces three major types of isoflavones, daidzein, genistein, and glycitein aglycones and their glucosides and malonylglucosides. It has been known that malonylated glucosides are rapidly converted to their corresponding aglycones due to the unstable thermolabile glucoside malonates; therefore, the analytical study of malonylated glucosides has been insufficient. In this study, we analyzed the malonylglucoside content in soybean seeds. Isoflavone analysis of three soybean cultivars revealed that 81.5~90.0% of the total isoflavones were malonylglucosides, whereas aglycones were rarely detected. Moreover, the total isoflavone content increased during a 5-day germination period where growth regulators and coumaric acid treatments tended to yield higher isoflavone content than the normal germination treatment, however the differences were not significant; notably, the isoflavone accumulation trend continued with additional germination days. The content of malonylglucoside was higher than that of other isoflavones, which was 83.7~86.6% of the total isoflavone content in seeds with a 3-day germination period. Furthermore, isoflavones were significantly accumulated in the hypocotyl of seedlings with a 5-day germination period. The content of isoflavone in the hypocotyl of the Pungsannamul-kong was 10,240 ug/g when treated with coumaric acid, which was considerably higher than that of other cultivars and treatments. Additionally, soybean seeds heated at $60^{\circ}C$ for 1 hour produced higher isoflavone content than non-heated soybean seeds. Our results show that it is possible to increase the isoflavone content in soybean seeds through various treatments.

• Korean Journal of Food Science and Technology
• /
• v.27 no.6
• /
• pp.909-914
• /
• 1995

In order to investigate gelation properties of Gelation Properties of ${\alpha}-lactalbumin$(${\alpha}-La$), gelling times and protein solubilities of ${\alpha}-La$ gels prepared in 0.1 M Tris-HCI buffer(pH 8.0) followed by heating at $90^{\circ}C$ for 40 minutes under different ${\alpha}-La$ concentration, NaCl, $CaCl_2$, N-ethylmaleimide(NEM), and dithiothreitol(DTT) concentration were measured. Gelling times decreased with increasing concentration of ${\alpha}-La$, NaCl, $CaCl_2$, and DTT, but increased with increasing concentration of NEM. ${\alpha}-La$ solutions made from all treatments were gelled within 40 minutes with the exception of NEM at $20{\sim}50\;mM$. Solubilities decreased with increasing concentration of ${\alpha}-La$, NaCl, $CaCl_2$, and DTT, but the solubility of NEM-modified gels increased with increasing concentration of NEM. As the results, solubilities In standard buffer were $10.4{\sim}51.3%$, $9.2{\sim}35.4%$, $11.1{\sim}35.0%$, $8.0{\sim}9.5%$, and $96.8{\sim}56.2%$, respectively. Solubilities in standard buffer containing 8 M urea and 0.5% SDS were higher than those in standard buffer, and were $41.8{\sim}81.3%$, $41.9{\sim}64.1%$, $43.5{\sim}69.8%$, $29.6{\sim}38.5%$, and $77.4{\sim}98.9%$, respectively. Solubilities in the presence of DTT were almost close to 100% in all conditions. These results indicates that the gelation rate and solubility are influenced by many factors, i.e. protein concentration, kind and concentration of salts, concentration of thiol reagents. The solubility of gel decreased with increasing the gelation rate.

• Food Science and Preservation
• /
• v.10 no.3
• /
• pp.421-426
• /
• 2003

Effects of acid, salt, heat treatment and natural antimicrobials on survival of E. coli O157:H7 CDF1, A. sobria CDF3 and S. aureus CDF2 isolated from surface of carcass in minced meat was investigated. The growth of E. coli O157:H7 CDF1 and A. sobria CDF3 inhibited in minced meat containing above 4％ NaCl but not in 1％ lactic acid. The growth of S. aureus CDF2 was not inhibited significantly by addition of 4％ NaCl but inhibited completely in minced meat containing 1％ lactic acid. Survival of A. sorbia CDF3 did not show any differences during storage at 4 and 10$^{\circ}C$. E. coli O157:H7 CDF10 and A. sobria CDF3 did not detect after heat treatment at 60$^{\circ}C$ for 10 min but S. aureus CDF2 decreased only 1 log after the same treatment. Viable cell of E. coli O157:H7 CDF1 decreased 2 log in TSB containing 0.5％ Oolong tea extract after incubation for 12 hr compared with control but A. sobria CDF3 and S. aureus CDF2 did not detect at the same condition. The growth of E. coli O157:H7 CDF1, A. sobria CDF3 and S. aureus CDF2 was not inhibited by addition of 0.3％ Oolong tea extract but inhibited by addition of 0.5％ Oolong tea extract in minced meat at 20$^{\circ}C$ for 24hr.

• Korean Journal of Food Science and Technology
• /
• v.30 no.4
• /
• pp.957-963
• /
• 1998

Several medicinal herbs, which are nontoxic and have been used widely in traditional folk medicine, were extracted and antimicrobial activity of the extracts was investigated against various foodborne pathogens or food poisioning microorganisms. The ethanol extract of Sansa, Hwangryun, Cheukbaek, and Seokchangpo showed strong antimicrobial activities against Gram postive and Gram negative bacteria, whereas those of Sakunja, Sukjihwang and Baekji had little antimicrobial activities on microorganisms tested. Among medicinal herb extracts, ethanol extract of Coptis chinensis Franch (hwangryun) showed the strongest antimicrobial activity. Antimicrobial activity of ethanol extract of Coptis chinensis Franch was not destroyed by heating at $100^{\circ}C$ for 60 min and at $121^{\circ}C$ for 30 min, which is very stable over heat. The pH effect on minimal inhibitory concentrations (MIC) of the extract of Coptis chinensis Franch indicated that MIC was reduced with increasing the pH value of the medium. The inhibitory effect of partially purified substance from the ethanol extract of Coptis chinensis Franch on the growth of Listeria monocytogenes and Staphylococcus aureus was investigated. Growth of those strains occurred at the concentration of $100{\;}{\mu}g/mL$ and were inhibited at $500{\;}{\mu}g/mL$, whereas those strains was completely inactivated in the presence of $1000{\;}{\mu}g/mL$.

• Clean Technology
• /
• v.30 no.2
• /
• pp.134-144
• /
• 2024

In this study, the mechanical stability of red mud was improved for its commercial use as a catalyst to effectively decompose HFC-134a, one of the seven major greenhouse gases. Red mud is an industrial waste discharged from aluminum production, but it can be used for the decomposition of HFC-134a. Red mud can be manufactured into a catalyst via the crushing-preparative-compression molding-firing process, and it is possible to improve the catalyst performance and secure mechanical stability through calcination. In order to determine the optimal heat treatment conditions, pellet-shaped compressed red mud samples were calcined at 300, 600, 800 ℃ using a muffle furnace for 5 hours. The mechanical stability was confirmed by the weight loss rate before and after ultra-sonication after the catalyst was immersed in distilled water. The catalyst calcined at 800 ℃ (RM 800) was found to have the best mechanical stability as well as the most catalytic activity. The catalyst performance and durability tests that were performed for 100 hours using the RM 800 catalyst showed thatmore than 99% of 1 mol% HFC-134a was degraded at 650 ℃, and no degradation in catalytic activity was observed. XRD analysis showed tri-calcium aluminate and gehlenite crystalline phases, which enhance mechanical strength and catalytic activity due to the interaction of Ca, Si, and Al after heat treatment at 800 ℃. SEM/EDS analysis of the durability tested catalysts showed no losses in active substances or shape changes due to HFC-134a abasement. Through this research, it is expected that red mud can be commercialized as a catalyst for waste refrigerant treatment due to its high economic feasibility, high decomposition efficiency and mechanical stability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.157-157
• /
• 2009

$BaTiO_3$를 기본조성으로 하는 PTC 써미스터는 Curie 온도이상에서 저항이 급격히 상승하는 반도성 전자세라믹스로서 degaussing 소자, 정온 발열체, 온도센서, 전류 제한 소자 등 상업적으로 폭넓게 사용되고 있다. 본 소자는 소결온도, 소결 및 열처리 분위기, 불순물, 첨가제 등의 제조공정상의 인자들과 기공률, 결정립 크기 등이 복합적으로 작용하여 PTCR 특성이 크게 영향을 받기 때문에 제조하기에 무척 까다로운 소자로 알려져 있다. 특히 과전류 보호 소자용으로 사용하기 위해서는 상온 비저항을 크게 낮추어야 하며 이에 대한 연구가 계속 진행되고 있다. 따라서 본 연구에서는 SiO2을 0.5~10 at%로 달리한 조성으로 환원 분위기에서 소결하고 공기 중에서 재산화 처리하여 재료의 PTC 특성에 어떠한 영향을 미치는지 분석하였다. 소정의 조성을 선택하여 $1180^{\circ}C{\sim}1240^{\circ}C$에서 2시간 동안 환원분위기에서 소결하고, $800^{\circ}C$에서 1 시간 공기 중에서 재산화 처리한 후 R-T 특성을 측정하여 SiO2 함량에 따른 PTC 특성을 분석하였다. 그 결과 SiO2의 함량이 증가할수록 상온 저항은 낮아지다가 3.0 at% 이상으로 첨가할 경우 급격히 상승하는 경향을 나타내었다. 특히 SiO2를 1.0~3.0 at% 일 때 우수한 PTC 특성을 가졌다. $1180^{\circ}C$에서는 소결 밀도가 낮아 상온 비저항이 크게 높았지만, $1200^{\circ}C{\sim}1220^{\circ}C$에서는 정상 입성장이 나타나면서 일반적인 PTC 특성을 가졌지만, $1240^{\circ}C$ 이상에서는 공정 액상이 형성되어 비정상 입성장이 일어나 상온 비저항이 크게 낮아졌다. 한편 점핑비-log(Rmax/Rmin)는 SiO2 함량이 증가할수록 높아지다가 3.0 at% 이상에서는 낮아짐을 확인하였다.