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Wong C.S.,Plasma Technology Research Center
Journal of Biomedical Materials Research - Part B Applied Biomaterials | Year: 2016

In this study, polycaprolactone (PCL) film, a high potential material used in biomedical applications, was treated by air plasma prior to a conjugation by carbodiimide cross-linking with various types of proteins, including type A gelatin, type B gelatin, and collagen hydrolysate. The properties of modified PCL films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurement, and atomic force microscopy. The XPS results showed that oxygen and nitrogen atoms were successfully introduced on the air plasma-treated PCL surface. Primary amine was found on the air plasma-treated PCL films. All proteins were shown to be successfully cross-linked on air plasma-treated PCL films. The wettability and roughness of protein-conjugated PCL films were significantly increased compared to those of neat PCL film. In vitro biocompatibility test using L929 mouse fibroblast showed that the attachment percentage and spreading area of attached cells on all protein-conjugated PCL films were markedly increased. Comparing among modified PCL films, no significant difference on the attachment of L929 on modified PCL films was noticed. However, the spreading areas of cells after 24 hours of culture on type A gelatin- and type B gelatin-modified PCL surfaces were higher than that on collagen hydrolysate-modified surface, possibly related to the lower percentage of amide bond on collagen hydrolysate-conjugated surface compared to those on both gelatin-conjugated PCL ones. This indicated that the two-step modification of PCL film via air plasma and carbodiimide cross-linking with collagen-derived proteins could enhance the biocompatibility of PCL films. © 2016 Wiley Periodicals, Inc. Source


Lee K.Y.,Plasma Technology Research Center
Fusion Science and Technology | Year: 2015

A method of estimating the margin of error for Thomson scattering systems based on polychromators has been devised during the operation of the Translation, Confinement, and Sustainment Upgrade (TCSU) experiment. This method first uses the propagation of uncertainty to determine the standard deviation (SD) of the ratio between two output signals. Later the SD or error is projected onto a characteristic curve that relates different ratios of the signal output to the electron temperature. This method brings an asymmetry to the error bounds, which goes accordingly to the ratio of the spectral response function for distinguishing higher temperatures. Also, the method follows with the nature of photon-statistics. As the plasma density is increased, as one might expect, the corresponding amplitude of the error bar becomes smaller. Source


Park H.J.,Plasma Technology Research Center | Ahn B.W.,Sungkyunkwan University | Kim T.Y.,Sungkyunkwan University | Lee J.W.,Sungkyunkwan University | And 4 more authors.
Thin Solid Films | Year: 2015

We introduce a possible route for vertically standing multi-layer graphene films (VMGs) on various substrates at low temperature by electron cyclone resonance microwave plasma. VMG films on various substrates, including copper sheet, glass and silicon oxide wafer, were analyzed by studying their structural, electrical, and optical properties. The density and temperature of plasma were measured using Cylindrical Langmuir probe analysis. The morphologies and microstructures of multi-layer graphene were characterized using field emission scattering electron microscope, high resolution transmission electron microscope, and Raman spectra measurement. The VMGs on different substrates at the same experimental conditions synthesized the wrinkled VMGs with different heights. In addition, the transmittance and electrical resistance were measured using ultra-violet visible near-infrared spectroscopy and 4 probe point surface resistance measurement. The VMGs on glass substrate obtained a transmittance of 68.8% and sheet resistance of 796 Ω/square, whereas the VMGs on SiO2 wafer substrate showed good sheet resistance of 395 Ω/square and 278 Ω/square. The results presented herein demonstrate a simple method of synthesizing of VMGs on various substrates at low temperature for mass production, in which the VMGs can be used in a wide range of application fields for energy storage, catalysis, and field emission due to their unique orientation. © 2015 Elsevier B.V. Source

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