• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.4
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• pp.238-243
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• 2018

A nanofiber was fabricated with carbon nanotubes for transparent electrodes. It was prepared with a composite solution of bio-molecules polycaprolactone (PCL) and multiwalled carbon nanotubes (MWCNTs) by electrospinning on a glass substrate, following which its electrical characteristics were investigated. The content of MWCNTs was varied during electrospinning, while that of PCL was fixed. Further, a nanometer-thick thin film of silver was deposited on the nanofiber layer using a thermal evaporator to improve the electrical characteristics; the sheet resistance significantly reduced after this deposition. The results showed that this carbon nanotube nanofiber has potential applications in biotechnology and as a flexible transparent display material.

• Polymer(Korea)
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• v.38 no.4
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• pp.518-524
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• 2014

Electrospinning has gained interests as a polymer processing technique for nanofiber fabrications. It is well known that both polymer solutions and polymer melts can be electrospun. Among them, melt electrospinning is environmentally friendly technique due to the absence of solvent. However, the diameter of melt-electrospun fibers is typically thicker than solution-electrospun fibers. By using a home-made melt-electrospinning device, micron-sized fibers with smooth and even surfaces were electrospun successfully. We demonstrate that low-density polyethylene fibers can be reduced in diameter with a viscosity-reducing additive such as low molecular weight polyethylene monoalcohol and polyethylene wax. The diameter was further reduced by blending it with oxidized polyethylene wax due to polarity increment. Additionally, parameters affecting the diameter were analyzed such as an applied voltage and a spinning distance.

• Polymer(Korea)
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• v.36 no.2
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• pp.124-130
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• 2012

The uniform nanofibers of poly(L-lactide-$co$-${\varepsilon}$-caprolactone) (PLCL) with different contents of marine collagen (MC) were successfully prepared by electrospinning method. The effects of the major parameters in electrospinning process such as tip to target distance (TTD), voltage, nozzle size and flow rate on the average diameter of the electrospun nanofiber were investigated in generating composite nanofiber. The diameter and morphology of the nanofibers were confirmed by a scanning electron microscopy (SEM). Also, we measured a water contact angle to determine the surface wettability of the nanofibers. The average diameter of the nanofibers decreased as the value of TTD, MC contents, and voltages increased in comparison with that of pristine PLCL nanofiber. In contrast, the diameter of the nanofibers increased as the flow rate and inner diameter of nozzle increased in comparison with that of pristine PLCL. In addition, the hydrophilicity of the nanofiber and attachment of MG-63 cells on the sheets increased as incorporated collagen contents increased. Therefore, the marine collagen would be a potential material to enhance cellular interactivity of synthetic materials by mimicking the natural tissue.

• Membrane Journal
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• v.16 no.1
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• pp.1-8
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• 2006

Nanofiber is a broad phrase generally referring to a fiber with diameter less than 1 micron. Various polymers have been successfully electrospun into nanofibers in recent years. These nanofibers, due to their high surface area and porosity, have a great potential for use as filter medium, adsorption layers in protective clothing, etc. Nanofiber filters will enable new levels of filtration performance in the field of air filtration. In particular, nanofibers provide marked increases in filtration efficiency at relatively small pressure drop in permeability. Therefore, nanofiber filters could be substituted for conventional filter market due to the easy application of process and the possibility of coating to micron-sized non-woven sheets. This review is discussed on the trend of researche and development related to nanofiber filter including future marketability.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.2.1-2.1
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• 2011

Biomedical applications of electrospun nanofibrous meshes have been receive tremendous attentions because of their unique structures and versatilities as novel biomaterials. Incorporation of growth factors in fibrous meshes can be performed by surface-modification and encapsulation. Those growth factors stimulate differentiation and proliferation of specific types of cells and thus lead tissue regenerations of specific cell types. Topographical cues of electrospun nanofibrous meshes also increase differentiation of specific cell types according to alignments of fibrous structures. Wound healing treatments of diabetic ulcers were performed using nanofibrous meshes encapsulating multiple growth factors. Aligned nanofibrous meshes and those with random configuration were compared for differentiating mesenchymal stem cells into neuronal cells. Thus, nanofibrous meshes can be applied to novel drug delivery carriers and matrix for promoting cellular proliferation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.1.1-1.1
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• 2011

Electrospinning has known to be very effective tool for production of versatile one-dimensional (1D) nanostructured materials such as nanofibers, nanorod, and nanotubes and for easily assembly to two-, three-dimensional(2D, 3D) nanostructures such as thin film, membrane, and nonwoven web, etc. We have studied on the electrospinning technology for novel energy storage and conversion materials such as advanced separator, dye sensitized solar cell, supercapacitor, etc. High heat-resistive nanofibrous membrane as a new separator for future lithium ion polymer battery was prepared by electrospinning of PVdF based composite solution. The novel nanofibrous composite nonwovens have tensile strength of above 50 MPa and modulus of above 1.3 GPa. The internal structure of the electrospun composite nanofiber with a diameter of few hundreds nanometer were composed of core-shell nanostructure. And also electrospun $TiO_2$ nanorod/nanosphere based dye-sensitized solar cells with high efficiency are successfully prepared. Some battery performance will be introduced.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.339-345
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• 2012

Electrospun meshed poly-caprolactone PCL was patterned by femtosecond laser with linear grooves. As parametric variables, focus spot size, pulse energy, and scanning speed were varied to determine the affects on groove size and the characteristics of the electrospun fiber at the edges of these grooves. The femtosecond laser was seen to be an effective means for flexibly structuring the surface of ES PCL scaffolds and the width of the ablated grooves was well controlled by laser energy and focus spot size. The ablation threshold was measured to be $14.9J/cm^2$ which is a little higher than other polymers. These affects were attributed to optical multiple reflections inside nano-fibers. By the laser-induced plasma at higher pulse energies, some melting of fibers was observed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.252-256
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• 2015

In this study, we propose a novel fabrication of an oxide-based lateral thermoelectric pn couple and investigate the characteristics of the thermoelectric couple. Electrospun ZnO and $LaSrCoO_3$ nanofibers are used as n- and p-legs of the couple, respectively. The Seebeck coefficients of the n- and p-type nanofibers and the pn couple are $-98.1{\mu}V/K$, $42.4{\mu}V/K$, and $118.8{\mu}V/K$, respectively. The thermoelectric couple generates an output voltage of $484.7{\mu}V$ at a temperature difference of 4.1 K.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.219.2-219.2
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• 2011

The oxyfluorination effects of electrospun carbon nanofibers (OFACFs) were investigated for $CO_2$ storage. Carbon nanofibers were prepared form poly acrylonitrile / N,N-dimethylformamide solution through electrospinning method and heat treatment. Chemical activation of carbon nanofibers were carried out in order to improve the pore structure. And the surface modification of activated carbon nanofibers was conducted by oxyfluorination to improve the $CO_2$ storage on effect of introduced functional groups. The samples were labeled CF (electrospun carbon nanofiber), ACF (activated carbon nanofibers), OFACF-1 ($F_2:O_2$ = 3:7), OFACF-2 ($F_2:O_2$ = 5:5) and OFACF-3 ($F_2:O_2$ = 7:3). The functional group of OFACFs was investigated by x-ray photoelectron spectroscopy analysis. The specific surface area, pore volume and pore size of OFACFs were calculated and pore shape was estimated by the BET equation. Through the adsorption isotherm, the specific surface area and pore volume significantly decreased by oxyfluorination.

• Macromolecular Research
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• v.13 no.1
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• pp.73-79
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• 2005

Poly(L-lactic acid-co-succinic acid-co-l,4-butane diol) (PLASB) was synthesized by direct condensation copolymerization of L-lactic acid (LA), succinic acid (SA), and 1,4-butanediol (BD) in the bulk using titanium(IV) butoxide as a catalyst. The weight-average molecular weight ofPLASB was $2.1{\times}10^{5}$ when the contents of SA and BD were each 0.5 mol/100 mol of LA. Electrospinning was used to fabricate porous membranes from this newly synthesized bioabsorbable PLASB dissolved in mixed solvents of methylene chloride and dimethylformamide. Scanning electron microscopy (SEM) images indicated that the fiber diameters and nanostructured morphologies of the electrospun membranes depended on the processing parameters, such as the solvent ratioand the polymer concentration. By adjusting both the solvent mixture ratio and the polymer concentration, we could fabricate uniform nanofiber non-woven membranes. Cell proliferation on the electrospun porous PLASB membranes was evaluated using mouse fibroblast cells; we compare these results with those of the cell responses on bulk PLASB films.