A design of experiments (DoE) approach to identify the influencing parameters that determine poly-D,L-lactic acid (PDLLA) electrospun scaffold morphologies

Electrospun fibrous materials have increasing applications in regenerative medicine due to the similarity of fibre constructs to the morphology of certain extracellular matrices. Although experimentally the electrospinning method is relatively simple, at the theoretical level the interactions between process parameters and their influence on the fibre morphology is not yet fully understood. Here, we hypothesised that a design of experiments (DoE) model could determine combinations of process parameters that result in significant effects on poly-D,L-lactic acid (PDLLA) fibre morphology. The process parameters used in this study were applied voltage, needle-to-collector distance, flow rate and polymer concentration. Data obtained for mean fibre diameter, standard deviation of the fibre diameter (stdev, measure of fibre morphology) and presence of 'beading' on the fibres (beads per µm2) were evaluated as a measure of PDLLA fibre morphology. Uniform fibres occurred at standard deviations of ≤ 500 nm, 'beads-on-string' morphologies were apparent between ± 500-1300 nm and large beads were observed at ± 1300-1800 nm respectively. Mean fibre diameter was significantly influenced by the applied voltage and interaction between flow rate and polymer concentration. Fibre morphology was mainly influenced by the polymer concentration, while bead distribution was significantly influenced by the polymer concentration as well as the flow rate. The resultant DoE model regression equations were tested and considered suitable for the prediction of parameters combinations needed for desired PDLLA fibre diameter and additionally provided information regarding the expected fibre morphology

Coaxial Electrospun Cellulose-Core Fluoropolymer-Shell Fibrous Membrane from Recycled Cigarette Filter as Separator for High Performance Lithium-Ion Battery

This paper reports an eco-friendly approach for extracting cellulose acetate (CA) from waste cigarette filter to construct a cellulose-based membrane separator for a high-performance lithium-ion battery. A cellulose/poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofiber membrane was prepared by coaxial electrospinning of a cellulose acetate core and PVDF-HFP shell, then hydrolyzed by LiOH. The cellulose-core/PVD-HFP-shell fibrous membrane shows good tensile strength (34.1 MPa), high porosity (66%), excellent thermal stability (to 200 °C), and super electrolyte compatibility (355% electrolyte uptake). It has a lower interfacial resistance (98.5 Ω) and higher ionic conductivity (6.16 mS cm-1) than those of commercial separators (280.0 Ω and 0.88 mS cm-1). In addition, the rate capability (138 mAh·g-1) and cycling performance (75.4% after 100 cycles) are also superior to those of the commercial separators, demonstrating the cellulose-core fibrous membrane to be a promising separator for a high-power and more secure lithium-ion battery

Badanie wpływu zmiennych procesu na średnicę poliuretanowych nanowłókien za pomocą projektowania czynnikowego

In this study, a factorial experimental design was used to study the effects of process parameters on nanofibre diameters, the voltage applied and the distance from the tip to collector. Nanofibres were produced using 10% concentration solution of polyurethanetetahydrofuran. The effects of solution parameters on the diameters of nanofibres are known. However, there has not been common agreement on the effect of the voltage applied on the diameter of nanofibres. A 32 factorial design was applied to identify the main and two-factor interaction effects. Analysis of the results from the design show that the distance and voltage applied had significant effects on polyurethane nanofibre diameter. It was found that for the main effect the distance from the tip to collector exhibits a great influence on the fibre diameter. The results also showed that the two-factor interaction effect significantly influenced the fibre diameter.W celu zbadania wpływu parametrów procesu (przyłożonego napięcia i odległości od wypływu polimeru do kolektora) na średnicę nanowłókien, zastosowano projektowanie czynnikowe. Nanowłókna wytworzono stosując 10% roztwór poliuretano-tetrahydrofuranu. Wpływ parametrów roztworu na średnicę nanowłókien jest znany, jednak wciąż nie jest jasna kwestia wpływu napięcia przyłożonego na średnicę nanowłókien. Analiza uzyskanych wyników wskazuje, że odległość i przyłożone napięcie mają znaczący wpływ na średnicę włókien poliuretanowych. Stwierdzono, że odległość od wypływu polimeru do kolektora ma duży wpływ na średnicę włókien. Wyniki wykazały również, że wpływ dwu-czynnikowych interakcji znacząco wpływa na średnicę włókna

Effect of Aromatic SAMs Molecules on Graphene/Silicon Schottky Diode Performance

WOS: 000378840000029Au/n-Si/Graphene/Au Schottky diodes were fabricated by transferring atmospheric pressure chemical vapor deposited (APCVD) graphene on silicon substrates. Graphene/n-Si interface properties were improved by using 5-[(3-methylphenyl)(phenyl) amino] isophthalic acid (MePIFA) and 5-(diphenyl) amino] isophthalic acid (DPIFA) aromatic self-assembled monolayer (SAM) molecules. The surface morphologies of modified and non-modified films were investigated by atomic force microscopy and scanning electron microscopy. The surface potential characteristics were obtained by Kelvin-probe force microscopy and found as 0.158 V, 0.188 V and 0,383 V as a result of SAMs modification. The ideality factors of n-Si/Graphene, n-Si/MePIFA/Graphene and n-Si/DPIFA/Graphene diodes were found as 1.07, 1.13 and 1.15, respectively. Due to the chain length of aromatic organic MePIFA and DPIFA molecules, also the barrier height phi(B) values of the devices were decreased. While the barrier height of n-Si/Graphene diode was obtained as 0.931 eV, n-Si/MePIFA/Graphene and n-Si/DPIFA/Graphene diodes have barrier height of 0.820 and 0.720 eV, respectively. (C) 2016 The Electrochemical Society. All rights reserved.TUBITAK (The Scientific and Technical Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [112T946]This work was supported by TUBITAK (The Scientific and Technical Research Council of Turkey) with project number 112T946. We also thank AQuReC (Applied Quantum Research Center) for Raman measurements

The effect of different knitted fabrics’ structures on the moisture transport properties

In this study, fabrics with different plain, tuck and float stitch combinations in three different tightness levels as tight, medium and loose are produced from combed ring spun cotton yarn. It is aimed at determining the effect of fabric structure on liquid absorption, transport and permeability properties, which are important factors in the people's perception of wear comfort. The air permeability, wicking ability and moisture management measurements of the produced fabrics are made. It is determined that the increase in the fabric tightness decreases the air permeability and increases the wicking ability especially in 60min measurements. The fabric tightness has also different effects on different knitting types in terms of moisture management properties. It is observed that structures with float stitches show high wicking ability and moisture management properties in terms of plain, tuck and float stitches combinations