• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.207-213
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• 1997

A field effect transistor(FET) type dissolved carbon dioxide($pCO_{2}$) sensor with a double layer structure of hydrogel membrane and $CO_{2}$ gas permeable membrane was fabricated by utilizing a $H^{+}$ ion selective field effect transistor(pH-ISFET) with Ag/AgCl reference electrode as a base chip. Formation of hydrogel membrane with photo-crosslinkable PVA-SbQ or PVP-PVAc/photosensitizer system was not suitable with the photolithographic process. Furthermore, hydrogel membrane on pH-ISFET base chip could be fabricated by photolithographic method with the aid of N,N,N',N'-tetramethyl othylenediarnine(TED) as $O_{2}$ quencher without using polyester film as a $O_{2}$ blanket during UV irradiation process. Photosensitive urethane acrylate type oligomer was used as gas permeable membrane on top of hydrogel layer. The FET type $pCO_{2}$ sensor fabricated by photolithographic method showed good linearity (linear calibration curve) in the range of $10^{-3}{\sim}10^{0}\;mol/{\ell}$ of dissolved $CO_{2}$ in aqueous solution with high sensitivity.

• Polymer(Korea)
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• v.33 no.5
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• pp.509-513
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• 2009

For examining an effect of lithium bromide on structure and property of chitosan/fibroin blend, we investigated the structural characteristic of chitosan/fibroin blend films using solution with lithium bromide which was removed during a casting. The chitosan/fibroin blend formed a complex with the dissolved bromine/lithium ions. The crystalline phase of the complex was found in the blend film at LiBr concentration of 0.6 mol/L. The degree of crystallization was decreased with increasing the concentration of LiBr. The hydrated crystalline phase of chitosan was formed in the blend film that lithium bromide was removed in the process of casting by neutralization and osmotic action. The crystallinity of this film was increased largely as compared with that of the film without lithium bromide. The complexed blend film formed hydrogel absorbing plenty of water.

• Elastomers and Composites
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• v.47 no.4
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• pp.292-296
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• 2012

An electric double-layer capacitor (ELDC) of activated carbon electrode is prepared using a proton-conducting hydrogel polymer electrolyte, which is composed of poly(vinyl alcohol), silicotungstic acid, $H_3PO_4$, and deionized water. A solid film by evaporating the hydrogel polymer electrolyte is also prepared for comparison. The hydrogel polymer electrolyte also acts as a separator with the thickness of about $80{\mu}m$ and the room-temperature ionic conductivity of $10^{-2}S\;cm^{-1}$. The EDLC containing the symmetric electrodes of activated carbon shows the specific capacitance of $58F\;g^{-1}$ at $100mV\;s^{-1}$ with a good cycle life, implying that the hydrogel polymer electrolyte is very promising for use in EDLCs.

• Polymer(Korea)
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• v.29 no.4
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• pp.408-412
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• 2005

Structure and characteristic of the films blended chitosan matrix with silk fibroin, extracted from Bombyx mori, were studied by X-ray diffraction, differential scanning calorimetry, FT-IR spectra analysis, SEM photographs, contact angle measurement and water absorbency in order to use as biomaterials. The blend films of $0\~30 wt\%$ fibroin content were prepared in acetic solution with $Li^+$ ion. It was found that the crystallinity of chitosan/fibroin blend films was decreased by the presence of intermolecular interactions such as hydrogen bonding between animo groups of chitosan and carbonyl groups of fibroin. As the proportion of fibroin in the blend increased, anhydrous crystalline phase of chitosan disappeared, and hydrated crystalline phase decreased, and $\beta$-structure crystalline phase of fibroin was formed. Therefore the blend films were crystallized into two different crystalline region of chitosan and fibroin. Surface hydrophilicity and water absorbency increased with blending fibroin. Above 20 $wt\%$ fibroin content, hydrogel film was formed. The surface and section of the film showed uniform microstructure on SEM photographs.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.3
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• pp.205-213
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• 2019

Batch adsorption tests were performed to evaluate the applicability of adsorption kinetic model by using hydrogel chitosan bead crosslinked with glutaraldehyde (HCB-G) for Cu(II) as cation and/or phosphate as anion. Pseudo first and second order model were applied to determine the sorption kinetic property and intraparticle and Boyd equation were used to predict the diffusion of Cu(II) and phosphate at pore and boundary-layer, respectively. According to the value of theoretical and experimental uptake of Cu(II) and phosphate, pseudo second order is more suitable. On comparison with the value of adsorption rate constant (k), phosphate kinetic was 2-4 times faster than that of Cu(II) at any experimental condition indicating the electrostatic interaction between ${NH_3}^+$ and phosphate is dominated at the presence of single component. However, when Cu(II) and phosphate simultaneously exist, the value of k for phosphate was sharply decreased and then the difference was not significant. Both diffusion models confirmed that the sorption rate was controlled by film mass transfer at the beginning time (t < 3 hr) and pore diffusion at next time section (t > 6 hr).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.2
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• pp.42-52
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• 2015

In this study, cellulose nanofibrils (CNF) were modified through carboxymethylation or TEMPO-mediated oxidation and their effects on ionicity and characteristics of sheet, film, and foam were investigated. Carboxymethylation was carried out on pulp fibers as a pre-treatment before preparation of CNF. The gel-like and translucent CNF hydrogel was obtained by grinding of carboxymethylated cellulose fibers. Carboxymethylated CNF film and freeze dried sheet showed higher transparency than that of untreated CNF. The CNF sheet with high strength and the CNF foam without large ice crystals were obtained by using the carboxymethylated CNF. TEMPO-mediated oxidation was carried out as a post-treatment of CNF. The zeta potential and charge demand of TEMPO-oxidized CNF were increased with an increase in oxidation time and addition amount of NaClO. The density of sheet made of TEMPO oxidized CNF was increased with the amount of oxidizing agent. The TEMPO oxidized cellulose nanofiber (TOCN) which was obtained from supernatant after centrifugation could be converted to transparent film.

• Journal of Periodontal and Implant Science
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• v.41 no.6
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• pp.263-272
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• 2011

A number of surface modification techniques using immobilization of biofunctional molecules of Titanium (Ti) for dental implants as well as surface properties of Ti and Ti alloys have been developed. The method using passive surface oxide film on titanium takes advantage of the fact that the surface film on Ti consists mainly of amorphous or low-crystalline and nonstoichiometric $TiO_2$. In another method, the reconstruction of passive films, calcium phosphate naturally forms on Ti and its alloys, which is characteristic of Ti. A third method uses the surface active hydroxyl group. The oxide surface immediately reacts with water molecules and hydroxyl groups are formed. The hydroxyl groups dissociate in aqueous solutions and show acidic and basic properties. Several additional methods are also possible, including surface modification techniques, immobilization of poly(ethylene glycol), and immobilization of biomolecules such as bone morphogenetic protein, peptide, collagen, hydrogel, and gelatin.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.463-469
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• 2015

Purpose: A hydrogel including alginate and $CaCl_2$ extracted from seaweed was manufactured, and their physical properties were investigated. Also, its applicability as contact lenses was examined. Methods: A film-type sample used in this experiment was manufactured using 2-hydroxyethyl methacrylate (HEMA), which is the raw material of hydrogel contact lenses; azobisiobutyonitile (AIBN), which is an initiator and ethylenglycoldimethacrylate (EGDMA), which is a cross-linking agent. It was hydrated in a PBS solution for 24 hours, and an interpenetrating polymer network (IPN) was formed in 1% and 2% alginate and 1%, 3%, and 5% $CaCl_2$ solutions for 24 hours, respectively. Results: The measurement of the physical properties of the film after the IPN showed that the moisture content was 30.89~36.89%, the refractive index was 1.431~1.441, the contact angle was $62.98{\sim}80.45^{\circ}$, and the tensile strength was 2.378~4.215 ($gf/mm^2$). Also, the physical properties hardly changed as the content of alginate increased, and the moisture content decreased as the content of $CaCl_2$ increased. As a result of the IPN, the moisture content and contact angle decreased compared to those of basic HEMA, but the tensile strength increased. The tensile strength of the second IPN was higher than that of the first IPN. In the case of $CaCl_2$, for the sample polymerized for 24 hours and the second IPN sample with 2% alginate, the contact angle decreased as the content of $CaCl_2$ increased. Conclusions: In this study, the tensile strength increased as the content of $CaCl_2$ increased, and the wettability increased as a result of IPN of alginate and $CaCl_2$. The hydrogel containing the alginate and $CaCl_2$ was confirmed possible utilization as contact lens material.

• Membrane Journal
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• v.33 no.6
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• pp.383-389
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• 2023

A high-performance forward osmosis (FO) membrane was prepared using polyethylene glycol diacrylate (PEGDA) hydrogel as a support layer. Through the UV-induced polymerization and subsequent phase separation of PEGDA, the crosslinked, hydrophilic, and porous PEGDA suppor layer was obtained. To achieve high FO flux and salt selectivity using the fabricated PEGDA support, a selective layer was synthesized via the toluene-assisted interfacial polymerization (TIP), in which toluene is used as an organic solvent. The prepared PEGDA-based FO membrane showed higher FO water flux and lower salt selectivity compared with commercial HTI membranes using 1.0 M NaCl draw solution and DI water feed solution. We propose the strategy to fabricate high-performance FO membranes utilizing supports formed with new hydrophilic materials and fabrication processes.

• Membrane Journal
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• v.16 no.1
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• pp.39-50
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• 2006

Porous chitosan and chitin membranes were prepared by using silica particles as porogen. Membrane preparation was achieved via the following three steps: (1) chitosan film formation by casting an chitosan solution containing silica particles, (2) preparation of porous chitosan membrane by dissolving the silica particles by immersing the film into an alkaline solution and (3) preparation of porous chitin membrane by acetylation of chitosan membrane with acetic anhydride. The optimum preparation conditions which could provide a chitosan and chitin membranes with good mechanical strength and adequate pure water flux were determined. To allow protein affinity, a reactive dye (Cibacron Blue 3GA) was immobilized on porous chitosan membrane. Binding capacities of affinity chitosan and chitin membranes for protein and enzyme were determined by the batch adsorption experiments of BSA protein and lysozyme enzyme. The maximum binding capacity of affinity chitosan membrane for BSA protein is about 22 mg/mL, and that of affinity chitin membrane for lysozyme enzyme is about 26 mg/mL. Those binding capacities are about $several{\sim}several$ tens times larger than those of chitosan and chitin-based hydrogel beads. Those results suggest that the porous chitosan and chitin membranes are suitable in affinity filtration chromatography for large scale separation of proteins.