Stretchable and Skin-Conformal Thermoelectric Generator with Highly Flexible and Plastically Bendable Silver Selenide Films.

Among inorganic thermoelectric materials, flexible thermoelectric materials have attracted considerable attention. In this study, highly flexible and plastically bendable silver selenide films with excellent thermoelectric performance at room temperature are presented. The flexibility of the freestanding silver selenide films was significantly improved through a simple annealing treatment. The highly flexible silver selenide films with a thickness of 26.0 µm displayed outstanding n-type thermoelectric performance, achieving an in-plane zT value of 0.38 at room temperature. Because silver selenide films are plastically bendable with a bending radius of less than 1 mm, they can be shaped into various forms. To achieve stretchability and skin-conformality in the thermoelectric generator, S-shaped silver selenide strips were used as an n-type thermoelectric element. Effective harvesting of electricity from heat of the human body was successfully demonstrated.

Highly Flexible and Durable Thermoelectric Power Generator Using CNT/PDMS Foam by Rapid Solvent Evaporation.

Using a simple, rapid solvent evaporation process, the authors produced 3D carbon nanotube (CNT)/polydimethylsiloxane (PDMS) foams with both high thermoelectric (TE) and good mechanical performance and used them to fabricate highly flexible and durable TE generators. The numerous pores and interfaces in the CNT/PDMS foams, which have porosities exceeding 87%, afford very low thermal conductivity of 0.13 W m-1 K-1 . The foam has a zT value of 6.6 × 10-3 , which is twice as high as that of pristine CNT foam. Importantly, the CNT/PDMS foam exhibits good tensile strength of 0.78 MPa, elongation greater than 20%, and excellent resilience even at compressive strain of 80%. This foam is used to fabricate a highly flexible TE foam generator that exhibits a moderate output power of 1.9 µW generated from the large temperature gradient of 18.1 K produced by applied heat. The authors also demonstrate a practical TE foam generator that produces sustainable output power of 3.1 µW under a compressive strain of 80% and 38.2 nW under the continuous vibrational stress produced by a car engine. The TE foam generator also exhibits excellent stability and durability under cyclic bending and harsh vibrational stress.

Transparent anti-stain coatings with good thermal and mechanical properties based on polyimide-silica nanohybrids.

In this work, we synthesized polyimide/silica hybrid materials via sol-gel method using a fluorinated poly(amic acid) silane precursor and a variety of perfluorosilane contents. We studied the influence of a hybrid coating film with the following characteristics; hydrophobicity, oleophobicity, optical transparency, and surface hardness of the coating films. The hybrid coatings with the fluorosilane contents up to 10 wt% are optically transparent and present good thermal stability with a degradation temperature of > 500 degrees C as well as a glass transition of > 300 degrees C. Both water contact angle and oil contact angle increase rapidly with introducing small amount of the fluorosilane in the hybrids and reaches the maximum of 115 degrees and 61 degrees, respectively. The hardness of the hybrid coatings increases up to 5H with an increase of the FTES content in the hybrids. These colorless, transparent, and thermally stable hybrid materials could be suitable for applications as anti-stain coatings.

Multi-functional hybrid coatings containing silica nanoparticles and anti-corrosive acrylate monomer for scratch and corrosion resistance.

Multi-functional hybrid coatings having both anti-corrosion and scratch resistance were prepared from modified silica nanoparticles and functional acrylates. To improve the dispersion properties of silica nanoparticles in the organic/inorganic hybrid coatings, the surface of the nanoparticles was modified with γ-methacryloxypropyltrimethoxysilane. The coating solution could be prepared by mixing modified silica nanoparticles, tetrasiloxane acrylate, di-acrylate monomer containing an anti-corrosion functional group, acrylic acid, and an initiator in a solvent. The mixture was then dip-coated on iron substrates and finally polymerized by ultraviolet (UV) irradiation. Corrosion and scratch resistance of the coated iron was evaluated by electrochemical impedance spectroscopy (EIS) and a pencil hardness test, respectively. From the EIS results, the coatings with tetrasiloxane acrylate and di-acrylate did not show any decrease in impedance or phase angle, even after 50 days' exposure to 0.1 M NaCl electrolyte, whereas the conventional acrylate coatings started to fail after only 24 h. A hybrid coating containing the amine-quinone functional group exhibited excellent corrosion protection properties with 4-5H pencil hardness.

Highly transparent polymer substrates for flexible displays using semi-interconnected interpenetrating polymer networks.

Semi-interconnected interpenetrating polymer networks (SIPNs) based on unsaturated polyurethane (UP) and different monomers, including styrene and acrylate with an UP ratio of 50 wt%, were synthesized. The resulting SIPN films exhibited excellent optical transparency in the visible range with > 90% transmittance at 400 nm. The glass transition temperature (Tg) varied in the range of 100 approximately 135 degrees C depending on the unsaturated monomers introduced. They also had good flexibility compared to the conventional rigid polystyrene or polyacrylate due to the homogeneously dispersed elastic urethane moiety in the SIPNs. Below the glass transition temperature (Tg) of the SIPN substrates, the ITO-grown SIPN films exhibited good electrical and optical properties, showing potential as a promising substrate in flexible display applications.

Mechanical properties of IIR/OMMT nanocomposites via melt-compounding and solution process.

Isobutylene-isoprene rubber (IIR)/organically modified montmorillonite (OMMT) nanocomposites were prepared by both melt-compounding and solution process. Organic modifiers were synthesized by the reaction of allyl bromide and alkyl amines to modify sodium montmorillonite (Na+ -MMT). After modification of Na+ -MMT with organic modifiers, the changes of d-spacing of OMMT were studied by X-ray diffraction (XRD). XRD patterns revealed that the d-spacing of Na+ -MMT increase from 1.1 nm for Na+ -MMT to 2.18 nm for the OMMT, indicating intercalation of organic modifier into the interlayers of montmorillonites. Mechanical properties of IIR/OMMT nanocomposites were studied by means of tensile measurements. Tensile strengths of IIR/OMMT nanocomposites prepared from melt-compounding and solution process were higher than those of IIR/Na+ -MMT nanocomposites and pristine IIR. When the solution process was used, IIR/OMMT nanocomposites provided further improvement in mechanical properties, as compared to those prepared from melt-compounding, indicating the better interaction between IIR and OMMT.

Colorless polyimide/organoclay nanocomposite substrates for flexible organic light-emitting devices.

We report the preparation and application of indium tin oxide (ITO) coated fluorine-containing polyimide/organoclay nanocomposite substrate. Fluorine-containing polyimide/organoclay nanocomposite films were prepared through thermal imidization of poly(amic acid)/organoclay mixture films, whilst on which ITO thin films were coated on the films using a radio-frequency planar magnetron sputtering by varying the substrate temperature and the ITO thickness. Finally the ITO coated fluorine-containing polyimide/organoclay nanocomposite substrate was employed to make flexible organic light-emitting devices (OLED). Results showed that the lower sheet resistance was achieved when the substrate temperature was high and the ITO film was thick even though the optical transmittance was slightly lowered as the thickness increased. approximately 10 nm width ITO nanorods were found for all samples but the size of clusters with the nanorods was generally increased with the substrate temperature and the thickness. The flexible OLED made using the present substrate was quite stable even when the device was extremely bended.

A study on the photopolymerization of acrylic monomers having fluorene moiety for the application of holographic data storage system.

We have prepared photopolymer compositions for holographic data storage system from aromatic diacrylate having fluorine moiety, a hybrid sol-gel, and photoinitiator. The fluorenyl diacrylate monomer was synthesized via nucleophilic substitution reaction of fluorene diphenol with an excess of 2-chloroethoxyethanol, followed by the reaction with acryloyl chloride. The physical and holographic properties of photopolymer were controlled by the ratio of precursor triethoxysilylpropyl polyethyleneglycol carbamate (TSPEG) in a hybrid sol-gel binder and the content of monomer. Also, we measured the photopolymerization rate and conversion of monomer by photo-differential scanning calorimeter (photo-DSC). Holographic recording was attempted by photopolymerization of the monomers in the photopolymer film using a 532 nm laser light in the presence of Irgacure 784 and holographic gratings were recorded into the photopolymer films by interfering two collimated plane wave beams. Contents of monomer and TSPEG were changed in the range of 0.25-1.0 equiv. and the composition were optimized in terms of diffraction efficiency. Finally, we obtained that efficient photopolymer films showed diffraction efficiency of 78% when 0.5 equiv. of TESPEG in sol-gel binder and 40% of compound 4 were added.

Flavonoids protect against cytokine-induced pancreatic beta-cell damage through suppression of nuclear factor kappaB activation.

OBJECTIVES: In the past few decades, the use of natural compounds, such as flavonoids, as anti-inflammatory agents has gained much attention. Our current study focuses on the preventive effects of quercetin, apigenin, and luteolin on cytokine-induced beta-cell damage. METHODS: Pancreatic beta-cells or islets were treated with cytokine mixtures in the presence or absence of flavonoids and the inhibitory effect of flavonoids against cytokine toxicity was determined. RESULTS: Treatment of RINm5F (RIN) rat insulinoma cells with interleukin 1beta (IL-1beta) and interferon gamma (IFN-gamma) induced cell damage. Quercetin, apigenin, and luteolin completely protected against IL-1beta- and IFN-gamma-mediated cytotoxicity in RIN cells. Incubation with quercetin, apigenin, and luteolin resulted in a significant reduction in IL-1beta- and IFN-gamma-induced nitric oxide production, a finding that correlated well with reduced levels of the inducible form of NO synthase messenger RNA and protein. The molecular mechanism by which quercetin, apigenin, and luteolin inhibited inducible NO synthase gene expression appeared to involve the inhibition of nuclear factor kappaB (NF-kappaB) activation. The IL-1beta- and IFN-gamma-stimulated RIN cells showed increases in NF-kappaB binding activity, p50 and p65 subunit levels in nucleus, and IkappaB alpha degradation in cytosol compared with unstimulated cells. Quercetin, apigenin, and luteolin also prevented IL-1beta- and IFN-gamma-mediated inhibition of insulin secretion. CONCLUSION: Quercetin, apigenin, and luteolin inhibited cytotoxicity in RIN cells and attenuated the decrease of glucose-stimulated insulin secretion in islets by IL-1beta and IFN-gamma.

Induction of G1 arrest and apoptosis by Scutellaria barbata in the human promyelocytic leukemia HL-60 cell line.

Scutellaria barbata has been used to treat cancer in Chinese medicine. The responsible anticancer mechanism, however, is not clear. Here we demonstrated an inhibitory mechanism due to a Scutellaria barbata extract (SBE) on a human promyelocytic leukemia cell line (HL-60) that has a mutation in the tumor suppressor gene p53. HL-60 cells were incubated with various concentrations of SBE. After a 24-h incubation, cytotoxicity and apoptosis were determined by MTT and DNA fragmentation assay, respectively. After treatment with SBE, cell cycle arrest was determined by measuring the cell number stained by 5'-bromo-2'-deoxyuridine (BrdU) and 7-amino-actinomycin D (7-AAD). Treatment of cells with SBE resulted in a concentration- and time-dependent inhibition of growth and a G1 phase arrest of the cell cycle. This effect was associated with a marked decrease in the protein expression of cyclin A, D1, D2, D3, and E and their activating partners, cyclin-dependent kinases (CDK) 2, 4, and 6 with concomitant upregulation of p21, cyclin-dependent kinase inhibitor. Downstream of the CDK inhibitory protein-CDK/cyclin cascade, SBE decreased phosphorylation level of retinoblastoma protein. SBE treatment also resulted in apoptosis evidenced by an increase of sub-G1 phase cells, DNA fragmentation and degradation of the inhibitory protein for the caspase-activated deoxyribonuclease. The molecular mechanism during SBE-mediated growth inhibition in HL-60 cells may be due to modulation of the cell-cycle machinery and the induction of apoptosis.