Influence of topography of nanofibrous scaffolds on functionality of engineered neural tissue

Properly engineered scaffolds combined with functional neurons can be instrumental for the effective repair of the neural tissue. In particular, it is essential to investigate how three-dimensional (3D) systems and topographical features can impact on neuronal activity to obtain engineered functional neural tissues. In this study, polyphenylene sulfone (PPSu) scaffolds constituted by randomly distributed or aligned electrospun nanofibers were fabricated to evaluate the neural activity in 3D culture environments for the first time. The obtained results demonstrated that the nanofibers can successfully support the adhesion and growth of neural stem cells (NSCs) and enhance neuronal differentiation compared to 2D substrates. In addition, NSCs could spread and migrate along the aligned fibers. The percentage of active NSC-derived neurons and the overall network activity in the fibrous substrates were also remarkably enhanced. Finally, the data of neuronal activity showed not only that the neurons cultured on the nanofibers are part of a functional network, but also that their activity increases, and the direction of neural signals can be controlled in the aligned 3D scaffolds

High-RI resist polymers for 193 nm immersion lithography

A critical aim within the field of 193 nm immersion lithography is the development of high refractive index immersion fluids and resists. Increases in the refractive index (RI) of the immersion fluid will result in increases in the numerical aperture and depth of focus. Increasing the RI of resist polymers will improve exposure latitude for the process. A challenge for increasing the RI of resist polymers is to do so without detrimentally affecting other properties of the polymer such as transparency, line edge roughness, adhesion and plasma etch resistance. It is well known in the literature that introducing sulfur, bromine or aromatic groups into a polymer structure will increase its RI. However, due to the relatively strong absorption of phenyl groups at 193 nm these groups have to be avoided. Furthermore, the use of bromine poses problems associated with contamination of the silicon wafer. Hence, in this study, a systematic approach has been used to increase the sulfur content of 193 nm type resist polymers, by synthesis of sulfur-containing monomers and by performing bulk modifications of the polymer. The effect of sulfur content on the RI at 193 nm was then investigated. A broad study of the relationship between molecular structure and RI dispersion from 250-180 nm has also been undertaken, and conclusions drawn using QSPR methodologies. Finally, the effect of sulfur content on other lithography parameters, such as transparency, adhesion and plasma etch resistance, was also evaluated

Study on Thermal Properties and Mechanical Properties of Short-cut Polyimide-Fiber Reinforced Polyphenyl Sulfone Composites

In order to increase the thermal stability and mechanical property of PPSU, two different polyimide (PI) short cut fibers reinforced polyphenyl sulfone (PPSU) composites were prepared by melt extrusion using a threescrew extruder. In addition, the effects of fiber lengths on thermal stability, heat resistance and mechanical properties of the composites was studied. The results indicate that the addition of polyimide chopped fiber can greatly improve the heat resistance of the composites. Comparing with PPSU, with the increasing of fiber content, the heat deformation temperature (HDT) of composites increased from 205 °C to 229 °C, but the addition of polyimide fiber has limited effect on the thermal stability of the composites. Meanwhile, the addition of polyimide chopped fiber can also improve the mechanical properties of the composites. Compared with PPSU, the tensile strength of composites can be increased by 102%, and the bending strength can be raised by 117%

Liquid crystal polyester-carbon fiber composites

Liquid crystal polymers (LCP) have been developed as a thermoplastic matrix for high performance composites. A successful melt impregnation method has been developed which results in the production of continuous carbon fiber (CF) reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality. Tensile and flexural properties of LCP/CF composites are comparable to those of epoxy/CF composites. The LCP/CF composites have better impact resistance than the latter, although epoxy/CF composites possess superior compression and shear strength. The LCP/CF composites have good property retention until 200 F (67 % of room temperature value). Above 200 F, mechanical properties decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber as adequate toughness of the LCP matrix. Low mechanical property retention at high temperatures may be attributable to the low beta-transition temperature (around 80 C) of the LCP matrix material

Fabrication, tuning and optimization of poly (acrilonitryle) nanofiltration membranes for effective nickel and chromium removal from electroplating wastewater

In the present study, response surface methodology (RSM) is employed according to central composite design (CCD) for modeling and optimization NF membranes fabricated and tuned for effective removal of Ni and Cr from electroplating wastewater streams. The effect of concentration of poly(acrylonitrile) (PAN: 21–25 wt.%) as the main membrane material as well as poly(ethylene glycol) (PEG: 0–1.5 wt.%) and titanium dioxide nanoparticles (TiO2: 0–1 wt.%) as the additives and their mutual interaction on membrane performance and morphology were investigated. According to the quadratic polynomial model, independent factors were statistically significant and the obtained models were accurate. The optimized responses for Ni and Cr rejection and pure water flux were 87.093 (%), 83.271 (%) and 71.801 (Lit m−2 h−1) respectively at optimum membrane formulations of PAN: 23.93%, PEG: 0.41% and TiO2: 0.82%. The results of validation experiment confirm the data for predicted model at optimum point (Ni rejection: 88.093%, Cr rejection: 80.271% and pure water flux: 76.801 Lit m−2 h−1). Both Ni and Cr rejections increased from 60.87% to 80.36% and from 56.35% to 78.64%, respectively upon increasing PAN concentration in the dope from 21 wt.% to 25 wt.%. It was also found that decreasing PEG concentration led to increase in Ni and Cr rejections and decrease in pure water flux. Using of TiO2 nanoparticles led to increase of Ni and Cr rejections and pure water flux at different PAN concentrations. From the morphological perspective, increase in polymer concentration led to change of porous to spongy like structure while increasing PEG concentration led to increase in macrovoids area. Both porosity and mean pore size reduced by increase of PAN concentration and decrease of PEG concentration