Jooyoun Kim

Application of electrospun polyurethane web to breathable water-proof fabrics

Electrospun web may possibly be widely applied to protective garments or specialty textiles due to its high level of protection as well as comfort. Of particular interest in this study is to develop waterproof-breathable fabric by applying electrospun web of polyurethane directly onto the substrate fabric. The optimal electrospinning condition was examined with regards to the concentration, applied voltage and tip-to-collector distance. Solvent-electospinning of polyurethane was performed at the optimum condition, using N,N-dimethylacetamide as solvent. The thickness of 0.02 mm of electrospun web was applied onto the polyester/nylon blended fabric. For comparison, the polyester/nylon fabrics were coated with 0.02 mm thickness of polyurethane resin membranes adopting four different conditions. The electrospun PU web/fabric was compared to resin coated fabrics in terms of water-proof and breathable properties. The electrospun web applied fabric showed higher air permeability, vapor transmission, and thermal insulation properties than resin coated fabrics, which can be translated as greater comfort sensation of electrospun applied fabrics. However, water resistance value of electrospun web applied fabric did not reach that of resin coated fabrics.

Haptoglobin genotypic distribution (including Hp0 allele) and associated serum haptoglobin concentrations in Koreans

Background: Haptoglobin polymorphism is associated with the prevalence of infections, autoimmune diseases, cardiovascular diseases, and other disorders. Congenital haptoglobin deficiency is associated with anaphylactic transfusion reactions in anhaptoglobinaemic patients with antihaptoglobin antibody. Aims: To investigate haptoglobin genotypic distribution (including the Hp0 allele) and associated serum haptoglobin concentrations in Koreans. Methods: Five hundred and nine healthy Korean adults were randomly selected. Two methods were used: haptoglobin genotyping based on a polymerase chain reaction (PCR) system that exploited the structural difference of the Hp1 and Hp2 alleles, and another PCR method that detected haptoglobin gene deletion by amplification of the junctional region of the Hp0 allele. Serum haptoglobin concentrations were measured by nephelometry. Results: The haptoglobin genotypes of 509 subjects were as follows: Hp1Hp1, 7.1%; Hp2Hp1, 37.7%; Hp2Hp2, 49.3%; Hp0Hp1, 2.2%; Hp0Hp2, 3.5%; Hp0Hp0, 0.2%. The gene frequency of Hp0 in Koreans was calculated to be 0.031. Significant differences were seen among the concentrations of each haptoglobin genotype (Kruskal-Wallis test). Hp0Hp2, but not Hp0Hp1, was associated with hypohaptoglobinaemia. Conclusions: PCR methods for differentiating between haptoglobin genotypes, including the Hp0 allele, may be useful in a broad spectrum of basic studies and clinical examinations.

Defect-related room-temperature ferroelectricity in tensile-strained SrTiO3 thin films on GdScO3 (110) substrates

We investigate room-temperature (RT) ferroelectricity in tensile-strained SrTiO3 (STO) thin films grown on GdScO3 (110) substrates. To separate the strain and the defect dipole effect, we apply an electric field to measure the polarization in the direction perpendicular to the elongation axis, and the RT ferroelectric polarization is found to be perpendicular to that axis. These results clearly demonstrate the importance of the contribution of defect dipoles to the RT ferroelectricity observed in STO thin films.

Effect of Solvent Exposure on the Filtration Performance of Electrostatically Charged Polypropylene Filter Media

Solvent-induced performance deterioration in corona charged polypropylene electret filter media was studied. Electret media, exposed to isopropanol (IPA) in the liquid phase, exhibited reduced filtration efficiency with negligible changes in the pressure drop across the media. Scanning electron microscopy imaging indicated no observable morphological changes after IPA exposure. Solvent-induced efficiency deterioration of electret filter media was hypothesized to originate from charge deterioration rather than charge masking. The charge of the individual fibers in filter media was characterized using electrostatic force microscopy (EFM). EFM investigation produced evidence that exposure to IPA in the liquid phase affected the electrostatic charges on fibers. Exposure to organic solvents such as xylene, toluene, and ethyl benzene has been reported to increase charge mobility in polypropylene fibers, thereby reducing the electrostatic charge and the ability of the fibers in the electret filter media to capture particulates.

Fabrication of self-cleaning textiles by TiO2-carbon nanotube treatment:

The purpose of this study is to fabricate self-cleaning textiles with photocatalyst excited by sunlight irradiation. Self-cleaning textiles were realized by coating carbon nanotube (CNT)-TiO2-acrylate copolymer on cotton and nylon fabrics using the dip-pad-dry process. The effect of CNT addition to TiO2 was observed on the self-cleaning performance and tensile stress of the treated fabrics. The morphology, chemical structure and particle size of acrylate copolymer with CNT-TiO2 and treated fabrics were analyzed using transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and a dynamic particle-size analyzer. The self-cleaning efficiency of the treated samples was examined by decomposition rates of methylene blue in aqueous solution and that of a wine stain under sunlight irradiation. It was found that the decomposition rates both for methylene blue and the wine stain were improved by CNT addition to TiO2 treatment on fabrics. When tensile degradation by photocatalytic reaction was monitored for TiO2 and CNT-TiO2-treated fabrics, the tensile deterioration after 48 hours of irradiation appeared to be mitigated by CNT addition to TiO2 treatment.

The effects of the fabric properties on fabric movement and the prediction of the fabric movements in a front-loading washer

The purpose of this study is to determine the effects of the fabric properties on fabric movement and to suggest a prediction model for the fabric movements in a front-loading washer. During a wash cycle, the fabric moves in many different ways depending on the mechanical and physiochemical properties of the fabric. In this study, 14 different fabrics were measured for their mechanical and physiochemical properties by the Kawabata Evaluation System (KES) and the water absorption test. From the observation of the fabric movements in the washer, 13 movement indexes were derived, and the relationships between the fabric properties and fabric movements were studied. The critical fabric properties that affected the fabric movements were determined by the analysis of variance (one-way ANOVA) and the post hoc test using the Scheffe method. The major fabric properties that affected fabric movements were found to be fabric weight, drape coefficient, water content, shear recovery, compression linearity, and energy required for compression. These fabric properties were investigated for their relation with the fabric movement indexes. The predicting models for fabric movements were suggested by the multi-linear regression equations.

Effect of uni-axial strain on THz/far-infrared response of graphene

We present polarized optical transmission study of uniaxially strained large scale graphene in THz/far-infrared (IR) frequency region. Graphene was supported on stretchable polyethylene substrate and they were elongated up to 20% (ΔL/Lo = 0.2) by applying tensile force. For the IR light polarized along the strain direction (EIR//strain), the optical conductivity σ1(ω) of graphene changes from Drude response into strongly non-Drude-like behavior with a peak formed at finite energy ∼10 meV. In contrast, the coherent Drude conductivity is preserved along the direction perpendicular to the strain (EIR⊥strain). Possible origin of the strain-induced non-Drude σ1(ω)-behavior is discussed.

Infrared spectroscopy of the interface charge in a ZnO field-effect transistor

We used far-infrared transmission spectroscopy to probe the electrostatically induced charge carriers in a ZnO field-effect transistor. The carrier absorption spectrum exhibits a non-Drude, incoherent conduction behavior at low gate-source voltages (VGS<40V), which evolves toward a standard Drude behavior as VGS is increased. This change is explained successfully by a generalized Drude model. We find that the interface carriers undergo strong backscattering collisions during the channel conduction and the microscopic scattering angle changes with VGS.

The effect of obesity on fibrinolytic activity and plasma lipoprotein (a) levels in patients with type 2 diabetes mellitus in Korea

To determine whether previously reported abnormalities in fibrinolytic activity and plasma lipoprotein (a) levels could reflect obesity rather than diabetes per se, plasma concentrations of tissue-type plasminogen activator (t-PA), type 1 plasminogen activator inhibitor (PAI-1), and lipoprotein (a) (Lp (a)) were investigated in sixty-four type 2 diabetic patients (56.1 +/- 9.5 years; body mass index, 24.6 +/- 3.3 kg/m2) and thirty-two control subjects (57.9 +/- 8.9 years; body mass index, 24.6 +/- 3.4 kg/m2). Both the plasma t-PA and PAI-1 antigen levels were similar between the diabetic group (10.6 +/- 3.8 ng/ml; 27.7 +/- 11.6 ng/ml) and the control group (12.2 +/- 3.5 ng/ml; 27.7 +/- 9.6 ng/ml). The PAI-1 levels were evenly distributed from 5.93 to 52.7 ng/ml in diabetic patients. The difference of Lp (a) levels between the two groups was negligible (the diabetic group, median 11 mg/dl (range 0-72 mg/dl); the control group, median 13 mg/dl (range 0-55 mg/dl)). Significant correlations between PAI-1 levels and body mass index (BMI) were observed in both groups. In the diabetic group, PAI-1 levels also correlated with fasting C-peptide levels (r = 0.54, P < 0.01) and serum triglyceride levels (r = 0.28, P < 0.05). However, we could not find a significant association between either t-PA or PAI-1 levels and Lp (a) levels in the diabetic and control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Early stage release control of an anticancer drug by drug-polymer miscibility in a hydrophobic fiber-based drug delivery system

The drug release profiles of doxorubicin-loaded electrospun fiber mats were investigated with regard to drug-polymer miscibility, fiber wettability and degradability. Doxorubicin in hydrophilic form (Dox-HCl) and hydrophobic free base form (Dox-base) was employed as model drugs, and an aliphatic polyester, poly(lactic acid) (PLA), was used as a drug-carrier matrix. When hydrophilic Dox-HCl was directly mixed with PLA solution, drug molecules formed large aggregates on the fiber surface or in the fiber core, due to poor drug-polymer compatibility. Drug aggregates on the fiber surface contributed to the rapid initial release. The hydrophobic form of Dox-base was dispersed better with PLA matrix compared to Dox-HCl. When dimethyl sulfoxide (DMSO) was used as the solvent for Dox-HCl, the miscibility of drug in the polymer matrix was significantly improved, forming a quasi-monolithic solution scheme. The drug release from this monolithic matrix was slowest, and this slow release led to a lower toxicity to hepatocellular carcinoma. When an enzyme was used to promote PLA degradation, the release rates were closely correlated with degradation rates, demonstrating degradation was the dominant release mechanism. The possible drug release mechanisms were speculated based on the release kinetics. The results suggest that manipulation of drug-polymer miscibility and polymer degradability can be an effective means of designing drug release profiles.