Search

Carrier geometry is a key parameter of drug delivery systems and has significant impact on the drug release rate and interaction with cells and tissues. Here we present a piezoelectric inkjet printing system as a simple and convenient approach for fabrication of drug-loaded polymer microparticles with well-defined and controlled shapes. The physical properties of paclitaxel (PTX)-loaded poly(lactic-co-glycolic acid) (PLGA) inks, such as volatility, viscosity and surface tension, were optimized for piezoelectric inkjet printing, and PTX-loaded PLGA microparticles were fabricated with various geometries, such as circles, grids, honeycombs, and rings. The resulting microparticles with 10% (w/w) PTX exhibited a fairly homogeneous shape and size. The microparticle fabrication by piezoelectric inkjet printing was precise, reproducible, and highly favorable for mass production. The microparticles exhibited a biphasic release profile with an initial burst due to diffusion and a subsequent, slow second phase due to degradation of PLGA. The release rate was dependent on the geometry, mainly the surface area, with a descending rate order of honeycomb>grid, ring>circle. The PTX-loaded microparticles showed a comparable activity in inhibiting the growth of HeLa cells. Our results demonstrate that a piezoelectric inkjet printing system would provide a new approach for large-scale manufacturing of drug carriers with a desired geometry.

The effects of Ru on the self-reducibility of Ru-doped Ni/MgAl2O4 catalysts, which do not need pre-reduction treatment with H2, were investigated in the steam reforming of methane (SRM). The Ru-promoted Ni/MgAl2O4 catalysts with various amounts of Ru (0–0.5 wt%) were prepared by stepwise impregnation and co-impregnation methods using hydrotalcite-like MgAl2O4 support. For comparison, Ru/MgAl2O4 catalysts with the same amount of Ru were also prepared by the impregnation method. The catalysts were characterized by the N2-sorption, XRD, H2-TPR, H2-chemisorption, and XPS methods. Ni/MgAl2O4 catalyst in the presence of even the trace amount of Ru (Ru content ≥0.05 wt%) showed higher conversion without pre-reduction as compared to Ru/MgAl2O4 catalysts in SRM under the same conditions. The self-activation of Ru–Ni/MgAl2O4 catalysts is mainly attributed to the spillover of hydrogen, which is produced on Ru at first and then reduces NiO species under reaction conditions. Besides, Ru doping makes the reduction of NiO easier. The stepwise impregnated Ru/Ni/MgAl2O4 catalyst produced superior performance as compared to co-impregnated Ru–Ni/MgAl2O4 catalyst for SRM.

It is not simple to accurately deposit minute quantities of polymeric materials by inkjet printing systems. High viscosity, nozzle clogging, agglomeration, precipitation, and uncontrollable drying patterns are serious problems which are frequently encountered in polymer inkjet printing. In this study, we investigated how inkjet printability of polymers correlates with the polymer ink formulations and inkjet process variables. After a systematic study with different variables, various patterns such as dots, cross stripes, and honeycombs were fabricated on flexible polyimide (PI) films and the pattern morphology and spatial distribution of the resulting polymer deposits after solvent drying were characterized.

Solution-based, direct-write patterning by an automated, computer-controlled, inkjet technique is of particular interest in a wide variety of industrial fields. We report the construction of three-dimensional (3D), micropatterned structures by polymer inkjet printing. A piezoelectric, drop-on-demand (DOD) inkjet printing system and a common polymer, PVA (poly(vinyl alcohol)), were explored for 3D construction. After a systematic preliminary study with different solvent systems, a mixture of water and DMSO was chosen as an appropriate solvent for PVA inks. The use of water as a single solvent resulted in frequent PVA clogging when the nozzles were undisturbed. Among the tested polymer ink compositions, the PVA inks in a water/DMSO mixture (4/1 v/v) with concentrations of 3 to 5 g/dL proved to be appropriate for piezoelectric DOD inkjet printing because they were well within the proper viscosity and surface tension range. When a dot was printed, the so-called ‘coffee-ring effect’ was significant, but its appearance was not prominent in line printing. The optimal polymer inkjet printing process was repeated slice after slice up to 200 times, which produced a well-defined, 3D micro-patterned surface. The overall results implied that piezoelectric DOD polymer inkjet printing could be a powerful, solid-freeform, fabrication technology to create a controlled 3D architecture.

The CO tolerance of a proton exchange membrane fuel cell (PEMFC) was investigated by ac impedance spectroscopy. The impedance of the fuel cell could be obtained by feeding oxygen into the cathode side and simulated gas into anode side. Furthermore, the anode impedance could be obtained by feeding hydrogen into the cathode side and simulated gas into anode side. The CO gas had a greater effect on the charge transfer reaction (high frequency arc) and hydrogen dissociative chemisorption (medium frequency arc) but little effect on the low frequency arc. Although the cathode impedance is a main part at high temperature, irrespective of CO concentration (≤100 ppm), the impedance of the full cell depends on anode impedance at low temperature and high CO concentration. It was found that CO gas has little effect on cathode impedance.

The effect of percolation on the electrochemical performance of lanthanum strontum manganate (LSM)–yttria-stabilized sirconia (YSZ) composite electrodes was investigated. It was identified that the polarization resistance of the LSM–YSZ composite electrodes is closely related to the connectivity of LSM–YSZ particles and depends on their size ratio. The composite electrode showed low electrochemical activity without YSZ connectivity. However, the polarization resistance decreased abruptly when YSZ connectivity occurred. Because the three phase boundary is dependent on the particle size of LSM and YSZ, the polarization resistance of the cathode decreases along with the decrease of the particle size of LSM and YSZ.

Zirconia-coated NiO powder was prepared by a newly developed surface-induced coating using thermal hydrolysis of Zr(NO 3 ) 2 ·6H 2 O in a mixed solvent of alcohol and water. Amorphous zirconium hydroxide was uniformly coated on the surface of NiO powder with the thickness of 20 nm. The ZrO 2 coating layer was crystallized to tetragonal ZrO 2 with the size of 40–60 nm at 900°C. The coated NiO powder containing 15 vol.% ZrO 2 , was found to have a similar isoelectric point to that of the ZrO 2 . The surface-induced ZrO 2 coating was a more efficient method for the prevention of Ni sintering than the mechanical mixing.

BaTiO3 powders were synthesized by glycine-nitrate process, using BaCO3 and Ti[OCH(CH3)2]4 as starting materials. Nitric acid was used as a solvent for the starting materials as well as an oxidant for self-combustion. The physical and chemical properties of as-prepared and calcined powders were characterized by helium pycnometer, X-ray diffraction, BET method and SEM. Single cubic phase of BaTiO3 was obtained at 1000°C. When the glycine/cation molar ratio was 1.2, the reactivity of self-combustion was the highest and the degree of aggregates after calcination was very low. Relative density of 95% was obtained at 1400°C when the molar ratio of 1.2 for glycine/cation was applied. The dielectric constant of the sintered body was about 2000 at 1400°C.

An organically modified silicate (Ormosil) for a dye laser was produced with a 90/10 ratio of Tetraethyl orthosilicate and Polydimethyl silanol (TEOS/PDMS) by sol-gel method. The optical properties of a dye incorporated in Ormosil were studied as a function of the amount of catalyst. In the xerogel doped with Rhodamine 6G perchlorate, a dimer peak near 500 nm appeared with increases of HCl amounts. The dimer peak was affected by enlarged pore size of the Ormosil and increased porosity due to the increased HCl concentration. Also, the increase of HCl concentration led to gradually lower transmittance values of the dye host. The dimer peak was identified by measuring optical absorption by ultraviolet/visible spectrophotometer. The changes of pore structure and porosity were investigated by SEM and BET.

Extracellular matrix (ECM) secreted from the resident cell of tissue is an ideal biomaterial evolved by nature. Cartilage is also built from well-organized ECM components in a gel-like structure with a high collagen and proteoglycan content. Here, we explored cartilage tissue engineering using ECM scaffolds seeded with stem cells. Both scaffolds and stem cells were isolated from human adipose tissue, which is abundant and easily harvested in the human body. The human ECM scaffolds contained various endogenous bioactive factors, including transforming growth factor-beta1 (TGF-β1, 8782±4989 pg/g, dry ECM), insulin growth factor-1 (13319±1388 pg/g, dry ECM), basic fibroblast growth factor (82373±9572 pg/g, dry ECM), and vascular endothelial growth factor (25647±2749 pg/g, dry ECM). A composite of ECM and stem cells was prepared and cultured in chondrogenic medium (with 10 ng/mL TGF-β1 or not) for 45 days. The volumes and weights of the composites increased during culture and the surface gradually became smooth. Cell viability remained high throughout the 45 days of in vitro culture. Composites showed the formation of cartilage-like tissue with the synthesis of cartilage-specific proteins such as collagen and glycosaminoglycan. Important chondrogenic markers were expressed including Sox-9, aggrecan, and collagen type II and XI. These results demonstrate that a cell/ECM composite containing endogenous bioactive factors could provide biochemical cues for the promotion of cartilage formation.

The electrochemical properties of poly(acrylonitrile) (PAN)-based polymer electrolyte and the discharge characteristics of an Li/LiCoO 2 cell were investigated. The PAN-based polymer electrolyte maintained an ionic conductivity of 1 mS/cm at room temperature, irrespective of storage time. Also, this electrolyte showed high electrochemical stability up to 4.3 V (versus Li + /Li). An Li/LiCoO 2 cell battery with this electrolyte has been fabricated and tested. This battery showed good cycling performance.

A high proton-conductivity was observed in the composite of amorphous phosphate and polytetafluoroethylene (PTFE). Incorporation of amorphous phosphate into PTFE emulsion caused a large increase of conductivity to about 4×10−2S/cm at 23°C. However, the conductivity decreased with increasing heat-treatment temperature, and the fabricated composite showed very low chemical stability.As a chemically stable composite, PTFE-based composite was also synthesized from α- or γ-zirconium phosphate crystalline powders dispersed in partially polymerized PTFE particles. By addition of zirconium phosphate powders, the proton conductivity jumped up to 2.2×10−3S/cm from 10−13S/cm of PTFE.

A drastic increase of electrical conductivity was observed in the composite of amorphous phosphate and ion-exchange resins (Nafion) as phosphorus concentration increased. Incorporation of amorphous phosphate into Nafion caused a large increase of conductivity to about 4×10−1S/cm at 23°C. However, the fabricated composite showed very low chemical stability.A high proton conductivity was also observed in a new inorganic-organic hybrids through incorporating PMA(molibdo-phosphoric acid)/PWA(tungsto-phosphoric acid) as a proton source in amorphous silicophosphate gel structure. Obtained gels were homogeneous and chemically stable. Resulting proton conductivity is very high (up to 5.5×10−3S/cm) compared to those of silicophosphate gels.