• Korean Journal of Materials Research
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• v.31 no.5
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• pp.278-285
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• 2021

This study produces electroconductive polycaprolactone (PCL)-based film with different amounts of graphene (G) through electrospinning, and the characteristics of the produced G/PCL composites are investigated. The G/PCL results are analyzed by comparing them with those obtained using pure PCL electrospun film as a control. The morphology of electrospun material is analyzed through scanning electron microscopy and transmission electron microscopy. Mechanical and electrical properties are also evaluated. Composites containing 1 % graphene have the highest elongation rate, and 5 % samples have the highest strength and elasticity. Graphene contents > 25 % show electro-conductivity, which level improves with increase of graphene content. Biological characteristics of G/PCL composites are assessed through behavioral analysis of neural cell attachment and proliferation. Cell experiments reveal that compositions < 50 % show slightly reduced cell viability. Moreover, graphene combinations facilitated cell proliferation compared to pure PCL. These results confirm that a 25 % G/PCL composition is best for application to systems that introduce external stimuli such as electric fields and electrodes to lead to synergistic efficiency of tissue regeneration.

• Journal of the Korean Society of Clothing and Textiles
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• v.46 no.2
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• pp.367-374
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• 2022

Herein, a highly elastic e-textile band with a two-wire transmission line was designed and fabricated for smart clothing applications. A conductive yarn with a very uniform low electrical resistance of 0.0357 Ω/cm was developed and used for the signal and ground lines. To control the elasticity of the e-textile band, spandex yarns were added in the warp direction during knitting and the tension was adjusted. As the length of the e-textile band increased, its RF performance deteriorated. Furthermore, the frequency corresponding to -3 dB S21 was lower in the 30% stretched band than in the unstretched band. For the e-textile bands with lengths 10, 50, and 100 cm, the frequencies corresponding to -3 dB S21 were 107.77, 24.56, and 13.02 MHz when not stretched, and 88.74, 22.02, and 12.60 MHz when stretched by 30%. The fabricated bands were flatter, more flexible, and more elastic than transmission line cables; thus, they can be easily integrated into wearables and smart clothing. However, to increase RF performance and achieve optimum utilization, future studies must focus on the fabrication of transmission lines with lower resistance and reduced distance between the signal and ground lines, and thus the number of transmission lines can be increased.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.4
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• pp.528-534
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• 2024

In continuous research of detecting highly toxic chemical warfare agents to ensure preparedness for the future battlefield, flexible and wearable sensor platforms with high sensitivity are still demanding. Herein we demonstrate a facile fabrication of polypyrrole-based chemiresistors on cellulose paper for the detection of nerve gas simulants. In order to optimize electrical properties of sensor platform, conducting polymer made of polypyrrole were first synthesized on flexible cellulose paper and interdigitated electrodes were formed thereon. Following confirmation of polypyrrole and/or oxime moiety through FT-IR analyses, electrical characteristics were measured in the various ratio of monomers between simple pyrrole and oxime-modified one. Typically for the optimized chemiresistor(2:8 molar ratio of simple pyrrole and oxime-modified one), eleven species of chemical warfare agents were examined and enhanced conductivity(10⁴~10⁵ order) was observed for three simulants(diethyl cyanophosphonate, diisopropyl fluorophosphonate and diethyl chlorophosphonate), which was mainly attributed to intermolecular hydrogen bonding, while no significant responses was recorded against sixteen common volatile organic chemicals.

• Membrane Journal
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• v.33 no.4
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• pp.211-221
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• 2023

This study presents a comprehensive study on the synthesis and characterization of PVI-PGMA/LiTFSI polymeric membrane electrolytes and CxNy-C flexible electrodes for energy storage applications. The dual-functional PVI-PGMA copolymer exhibited excellent ionic conductivity, with the PVI-PGMA73/LiTFSI200 membrane electrolyte achieving the highest conductivity of 1.0 × 10^-3 S cm^-1. The electrochemical performance of the CxNy-C electrodes was systematically investigated, with C3N2-C demonstrating superior performance, achieving the highest specific capacitance of 958 F g^-1 and lowest charge transfer resistance (R_ct) due to its highly interconnected hybrid structure comprising nanowires and polyhedrons, along with binary Co/Ni oxides, which provided abundant redox-active sites and facilitated ion diffusion. The presence of a graphitic carbon shell further contributed to the enhanced electrochemical stability during charge-discharge cycles. These results highlight the potential of PVI-PGMA/LiTFSI polymeric membrane electrolytes and CxNy-C electrodes for advanced energy storage devices, such as supercapacitors and lithium-ion batteries, paving the way for further advancements in sustainable and high-performance energy storage technologies.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.138-138
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• 2000

국내의 백상지 공정은 공정에 투입되는 청수의 양을 줄이면서 동시에 폐수 배출 양을 감 소시키기 위해 많은 노력을 하고 있다. 공정으로 유입되는 청수의 양과 처리된 폐수의 양을 줄이기 위한 방법으로 PDFCpolydisk filter)를 도입하여 백수를 여과하여 showertf sealing 에 재사용하고 있으며 공정수 재활용에 따른 유기 물질과 무기물질의 계 내로의 축적을 방 지하기 위한 효과적인 폐수 처리방법을 모색하고 있다. 일반적으로 청수를 백수로 대체할 경우 공정 백수 내에 TDSCtotal dissolved solid), T TSSCtotal suspended solid), CODCchemical oxygen demand), 전기 전도도와 칼숨 경 도 등이 증가되며 음이온성 저해 물질Canionic trash)이 증가하여 보류 및 지력증강용 첨가제의 효율 을 떨어뜨릴 뿐만 아니라 마모, 슬라엄, 펠트 막힘 등의 문제를 유발하게 된다고 알려져 있다. 청수를 백수로 대체함에 따라 생기는 이러한 문제를 해결하면서 효율적인 청수 절약 방안 을 세우기 위해서는 무엇보다도 문제를 유발하는 원인 물질의 축적 양을 예측하는 것이 중 요하다고 판단된다. 본 연구는 백상지 공정의 폐쇄화 수준이 높아짐에 따른 공정 백수 내의 유기물질의 축적 현상을 분석하는 것올 목적으로 하였다. 이를 위해 산화전분을 유기물질의 대표하는 물질로 설정하였다. 이는 백상파지와 함께 초지계 내로 유업되는 산화전분은 파지의 4%를 차지할 정도로 유입량이 많을 뿐만 아니라 음이온성을 띄고 있어서 지료에 홉착율이 낮고 양이온성 고분자의 효율을 저해하며 슬라임의 원인이 되기도 하는 물질이기 때문이다. 산화전분의 축적 현상을 분석하기 위하여 pilot 설비 상세 설계도를 참고하여 하루 생산량 이 16 T/D이고 백상파지만이 파지로 유입되는 백상지 생산 공정을 모델로하였으며, 산화전 분의 홉착과 용출 모델을 만들어 상용 시율레이터를 이용하여 시율레이션 프로그램을 작성 하였다. 시률레이션 프로그램에서는 장섬유 미세섬유, 충전제를 지료 구성 성분으로 설정하였고 O Orccotoma 등이 사용한 일과 보류도 모델을 응용하여 보류도 모델올 만들었다. 산화전분은 백상파지에 포함된 형태로만 초지계 내로 유입되며 백상파지가 해리되는 과정에서 완전히 백수에 용출되었다가 지료 구성 성분에 홉착되는 것으로 가정하였다. 지료 홉착된 산화전분 의 양은 용존 산화전분 총량에 비례하는 것으로 가정하였으며, 이 때 이 비례상수를 전분 홉착율이라 정의하였다. 시율레이션 결과, 공정 폐쇄화가 진행됨에 따라 백수 내의 산화 전분 농도는 증가하게 되 며, 폐쇄화 수준이 높아질수록 백수 내 전분 농도의 증가량은 더 높아졌다. 백수 내의 전분 농도의 증가량은 백상파지 첨가량이 증가할수록, 표면 사이징 양이 증가할수록 커졌다.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.1-7
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• 2024

With the increasing demand for wearable sensors that are capable of point-of-care testing, paper-based sensors have been extensively studied. Paper is not only extremely cost-effective but also lightweight and flexible, and it is easy to apply conductive materials such as carbon and hydrophobic substances like wax to its surface. Moreover, the capillary action caused by cellulose fibers in paper allows the flow of liquid without help from external forces, making paper a particularly promising platform for wearable electrochemical sensors. Accordingly, paper-based sensors for detecting various analytes through electrochemical methods have been actively developed. Recently, paper-based electrochemical sensors that utilize electrochemiluminescence (ECL) or electrochromic materials for the optical read-out have been reported. This review introduces the basic fabrication methods and various application strategies of paper-based electrochemical sensors.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.411-422
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• 2010

Self-sensing on micro-failure, dispersion degree and relating properties, of carbon nanotube(CNT)/epoxy composites, were investigated using wettability, electro-micromechanical technique with acoustic emission(AE). Specimens were prepared from neat epoxy as well as composites with untreated and acid-treated CNT. Degree of dispersion was evaluated comparatively by measuring volumetric electrical resistivity and its standard deviation. Apparent modulus containing the stress transfer was higher for acid-treated CNT composite than for the untreated case. Applied cyclic loading responded well for a single carbon fiber/CNT-epoxy composite by the change in contact resistivity. The interfacial shear strength between a single carbon fiber and CNT-epoxy, determined in a fiber pullout test, was lower than that between a single carbon fiber and neat epoxy. Regarding on micro-damage sensing using electrical resistivity measurement with AE, the stepwise increment in electrical resistivity was observed for a single carbon fiber/CNT -epoxy composite. On the other hand, electrical resistivity increased infinitely right after the first carbon fiber breaks for a single carbon fiber/neat epoxy composite. The occurrence of AE events of added CNT composites was much higher than the neat epoxy case, due to micro failure at the interfaces by added CNTs.

• Composites Research
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• v.19 no.5
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• pp.28-33
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• 2006

In this paper, we have studied the complex permittivities and their influence on the design of microwave absorbers of E-glass fabric/epoxy composite laminates containing three different types of carbon-based nano conductive fillers such as carbon black (CB), carbon nano fiber (CNF) and multi-wall nano tube (MWNT). The measurements were performed fur permittivities at the frequency band of 0.5 GHz$\sim$18.0 GHz using a vector network analyzer with a 7 mm coaxial air line. The experimental results show that the complex permittivities of the composites depend strongly on the natures and concentrations of the conductive fillers. The real and imaginary parts of the complex permittivities of the composites were proportional to the filler concentrations. But, depending on the types of fillers and frequency band, the increasing rates of the real and imaginary parts with respect to the filler concentrations were all different. These different rates can have an effect on the thickness in designing the single layer microwave absorbers. The effect of the different rates at 10 GHz was examined by using Cole-Cole plot; the plot is composed of a single layer absorber solution line and measured permittivities from these three types of composites. Single layer absorbers of 3 different thicknesses using carbon nano materials were fabricated and the -10 dB band of absorbing performances were all about 3 GHz.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.2
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• pp.139-150
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• 1993

This experiment was carried out to investigate the difference of seed vigor according to seed size, and the physiological aspects and physico-chemical phenomena related with seed vigor in soybean cultivars. Portion of seed coat and radicle to entire seed was much higher in cultivars with small seed than with large. Seed coat rate ranged 7.9% to 9.9%, and radicle 2.5% to 3.3% in small seed group, Whereas in large seed, seed coat rate did 5.5-6.4% and radicle, 1.5 to 2.1%. After accelerated aging treatment, there are significant difference in germination ability between seed size. The germination rate after aging ranged 47 to 80% in cultivars with small seed, but in large seed, only 14 to 24%. After seed was carried out dehydration in incubator at 25 after soaking for 6 hours, the moisture content of seed in drying for 12 hour was 25.5% in small seed, while it was 51% in large seed. Electrical conductivity, leaching soluble nitrogen and sugar content were higher in large seed cultivars. Besides, cotyledon damage after soaking was occurred frequently in large seed cultivars, and seed vigor within same cultivars was higher in small seed than large.

• Science of Emotion and Sensibility
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• v.25 no.1
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• pp.129-142
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• 2022

This study evaluates a program developed for a high school-university linked class. The program combines maker education and smart clothing technology, which has great potential. First, in the preparation stage, the dyeing design course incorporates the contents of previous studies on smart clothing and maker education. Second, in the development stage, a program was developed to make emotional eco-bags by applying the transfer dyeing technique using transfer paper for inkjet printers and smart clothing technology using conductivity thread and LED bulbs. Third, in the implementation stage, the class was offered to 17 high school students who want to major in clothing and textiles. Lastly, the class was evaluated. The program had a 4.95 satisfaction level as measures on a five-point scale. Furthermore, this paper suggested an advanced program with Lilypad Arduino. In conclusion, through this study, it was confirmed that the emotional eco-bag development program applied with conductive yarn and transfer dye could more easily produce smart clothing technology, thereby expanding the thinking of high school students regarding the clothing major.