Kwangwoon University

About: Kwangwoon University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Thin film & Resonator. The organization has 4020 authors who have published 8217 publications receiving 104365 citations.

Trans-Reflective Color Filters Based on a Phase Compensated Etalon Enabling Adjustable Color Saturation

Abstract: Trans-reflective color filters, which take advantage of a phase compensated etalon (silver-titania-silver-titania) based nano-resonator, have been demonstrated to feature a variable spectral bandwidth at a constant resonant wavelength. Such adjustment of the bandwidth is presumed to translate into flexible control of the color saturation for the transmissive and reflective output colors produced by the filters. The thickness of the metallic mirror is primarily altered to tailor the bandwidth, which however entails a phase shift associated with the etalon. As a result, the resonant wavelength is inevitably displaced. In order to mitigate this issue, we attempted to compensate for the induced phase shift by introducing a dielectric functional layer on top of the etalon. The phase compensation mediated by the functional layer was meticulously investigated in terms of the thickness of the metallic mirror, from the perspective of the resonance condition. The proposed color filters were capable of providing additive colors of blue, green, and red for the transmission mode while exhibiting subtractive colors of yellow, magenta, and cyan for the reflection mode. The corresponding color saturation was estimated to be efficiently adjusted both in transmission and reflection.

Enzymatic epoxidation and polymerization of cardanol obtained from a renewable resource and curing of epoxide-containing polycardanol

Abstract: Epoxide-containing polycardanol was enzymatically synthesized via two routes using two different enzymes, viz. lipase and peroxidase. Lipase catalysis was used for the epoxidation of the unsaturated alkyl chains of both cardanol and polycardanol. Peroxidase catalysis was used for the polymerization of both cardanol and epoxide-containing cardanol. One route was the synthesis of epoxide-containing cardanol from cardanol, hydrogen peroxide and an organic acid in the presence of lipase, followed by the polymerization of the phenolic functional groups of cardanol using peroxidase. In the other route, polymerized cardanol was prepared from cardanol and hydrogen peroxide in the presence of peroxidase and, subsequently, the epoxide-containing polycardanol was synthesized from polycardanol, hydrogen peroxide and an organic acid in the presence of lipase. NMR and IR spectroscopy confirmed the polymer structure, and the former route yielded epoxide-containing polycardanol in a higher yield of over 90%. The curing of the resulting polymers proceeded thermally at 150 °C, yielding transparent polymeric films with a high gloss surface within 3 h. The pencil scratch hardness of the present films was improved compared with that of polycardanol. Owing to the epoxide contained in the polymerized cardanol, the film cured with phenalkamine showed a higher hardness value after a relatively short curing time.

Solvent-Processible Polymer Membrane-Based Liquid Junction-Free Reference Electrode

Abstract: A new type of liquid junction-free reference electrode system is devised by employing solvent-processible polymer membranes. The membranes are formulated with either a one-component silicone rubber or an aromatic-type polyurethane as the matrixes. The optimized formulations incorporate both cation- and anion-exchange sites (i.e., potassium tetrakis(p-chlorophenyl)borate and tridodecylmethylammonium chloride) and, in the case of silicone rubber, a plasticizer. The silicone rubber-based membrane, while possessing minimal response toward most ions, is found to display a near-Nernstian response to pH change. The aromatic polyurethane matrix formulation, however, is not sensitive to pH over a wide range (i.e., pH 2−12) and is shown to exhibit only a small emf variation (within ±2 mV) toward a wide variety of salts added even at very high concentrations (i.e., up to 0.1 M). Potentiometric emf responses of ISEs (e.g., Na+, K+, Ca2+, Cl-), whether paired with a polymer membrane-based reference electrode or with a...

Hybrid Si-LiNbO_3 microring electro-optically tunable resonators for active photonic devices

Abstract: Hybrid Si-LiNbO3 electro-optic tunable ring resonators have been proposed and demonstrated as a path to achieving ultracompact and high-speed electro-optic devices. Free standing single crystal LiNbO3 microplatelets (∼mm long and ∼1 μm thick) were obtained from a z-cut LiNbO3 substrate by ion implantation and thermal treatment. The platelets were transferred and thermally bonded on top of Si resonators that were fabricated in a Si-on-insulator platform by a 0.18 μm standard complementary metal-oxide-semiconductor process. For the hybrid microring resonator, a free spectral range of 16.5 nm, a finesse F of ∼1.67×102, a Q-factor of ∼1.68×104, and an effective r coefficient of ∼1.7 pm/V were achieved for the TE mode. These values are in good agreement with the calculated results.

Waterproof Electronic-Bandage with Tunable Sensitivity for Wearable Strain Sensors.

Abstract: We demonstrate high-performance wearable electronic-bandage (E-bandage) based on carbon nanotube (CNT)/silver nanoparticle (AgNP) composites covered with flexible media of fluoropolymer-coated polydimethylsiloxane (PDMS) films. The E-bandage can be used for motion-related sensors by directly attaching them to human skin, which achieves a fast and accurate electric response with high sensitivity according to the bending and stretching movements that induce changes in the conductivity. This advance in the E-bandage is realized as a result of the sensitivity that can be achieved by controlling the concentration of AgNPs in CNT pastes and by modifying the device architecture. The fluoropolymer encapsulation with hydrophobic surface characteristics allows for the E-bandage to operate in water and protects it from physical and chemical contact with the daily life conditions of the human skin. The reliability and scalability of the E-bandage as well as the compatibility with conventional microfabrication allow new possibilities to integrate flexible human-interactive nanoelectronics into mobile health-care monitoring systems combined with Internet of things (IoTs).