Sharif Digital Repository

In the present study, the feasibility of electrospun polyethersolfone (PES) nanofibrous membrane as the solid substrate for microfluidic based immunoassays to enhance the density of immobilized antibody on the surface of membrane was assessed. Conversely, the efficacy of antibody immobilization was compared by two different strategies as 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)/N-Hydroxysuccinimide (NHS) coupling chemistry and hydrophobic interaction. Compared to conventional immunoassays carried out in plates or gels, microfluidic based immunoassays grant a lot of advantages such as a consumption of little samples and reagents, shorter analysis time, and higher efficiency.... 

Polyvinylidene fluoride (PVDF) has special piezo/pyro/ferroelectric, flexibility, low weight, biocompatibility, economical, good chemical/thermal, and high mechanical properties, such as excellent nontoxic fiber/film formation. It has polar and nonpolar phases of α, β, γ, ε, and δ, in which the nonpolar α phase is the most stable one. However, the β phase is the best because it has good piezo/pyro/ferroelectric properties. Copolymers are attractive due to their low weight, nontoxic, chemical acid resistance, flexibility, and ease of processing. These aspects result in their applications in many fields. They are used for piezoelectric nanogenerators, cooling/heating sensors, electronic... 

Electrospinning is a simple and cheap process for forming one-dimensional (1D) nanofibers with controllable size, morphology, and chemistry. Besides these, the ultrahigh surface area with industrialization capability has attracted extensive interest in the research community. On the other hand, a photocatalytic process is a promising method for degrading organic pollutants that cannot be removed by conventional wastewater treatment. This review focuses on the recent progress of electrospun nanofibers for the photocatalytic degradation of water pollutants. The linkage between the electrospinning technique and the photocatalytic process is classified into two main categories: (1) polymeric... 

In this study, poly (vinylidene fluoride) PVDF/Starch nanofibers with a great potential for tissue engineering applications have been investigated. The electrospun nanofibers were formed by the electrospinning of the PVDF/Starch solutions in various ratios of PVDF to Starch. Characterizations of PVDF/Starch nanofiber were performed using rheometric mechanical spectroscopy (RMS), field emission scanning electron microscope (FE-SEM) and tensile test. The results showed that the addition of more Starch into the PVDF solution increased the viscosity of the prepared PVDF/Starch solutions. In addition, the mechanical properties of PVDF enhanced in the presence of Starch due to the higher... 

In this study, a new design of graded tubular scaffolds have been developed for the performance enhancement in vascular tissue engineering. The graded poly-L-lactide (PLLA) and gelatin fibrous scaffolds produced by electrospining were then characterized. The morphology, degradability, porosity, pore size and mechanical properties of four tubular scaffolds (graded PLLA/gelatin, layered PLLA/gelatin, PLLA and gelatin scaffolds) have been investigated. The tensile tests demonstrated that the mechanical strength and also the estimated burst pressure of the graded scaffolds were significantly increased in comparison with the layered and gelatin scaffolds. This new design, resulting in an increase... 

Understanding the dynamics of direct electrospinning is the key to control fiber morphologies that are critical for the development of new electrospinning methods and novel materials. Here, we propose the theory for direct electrospinning based on theories for (liquid) "rope coiling" and experimentally test it. For the experiments, the buckling of microscale liquid ropes formed from polymer solutions is studied systematically using three different electrospinning setups and for different polymer concentrations. We show that different buckling regimes exist, whose dynamics are governed by an interplay of electrical, inertial, and viscous forces, and that three different buckling regimes... 

Many patients all over the world suffer from acute wounds caused by traumas or burns. In most crucial cases, skin regeneration cannot be promoted spontaneously, and skin grafts are applied as the main treatment. However, this therapy has some drawbacks which motivate researchers to develop wound dressings. In this study, electrospun mats consisting of polycaprolactone (PCL) and polyvinyl alcohol (PVA) incorporated with silver sulfadiazine (SSD) are proposed to be used as antimicrobial wound dressings with the capability of cell seeding. Various amounts of SSD were loaded into PVA nanofibers, and the effects of SSD particles on the morphological characteristics of nanofibers, mechanical... 

ZnO/gC 3 N 4 hybrid nanofibers containing different concentrations of gC 3 N 4 nanosheets were prepared using electrospinning technique; this was followed by annealing at 460 forC for one hour in a box furnace. Based on scanning electron microscopy (SEM) image analysis, the mean diameter of the nanofibers was measured to be ~ 55 nm. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of ZnO and gC 3 N 4 in the prepared nanofibers. The photocatalytic activity of the nanofibers was examined under UV photoirradiation, showing that the ZCN0.5 nanofibers containing 0.5 wt% of gC 3 N 4exhibited the highest performance, as compared to other photocatalysts. The observed improvement... 

Direct near field electrospinning is used to produce very long helical polystyrene microfibers in water. The pitch length of helices can be controlled by changing the applied voltage, allowing the production of both microsprings and microchannels. Using a novel high frequency variable voltage electrospinning method we determined the helix formation speed and compared the experimental buckling frequency to theoretical expressions for viscous and elastic buckling. Finally we showed that the new method can be used to produce new periodic micro and nano structures  

A micro-solid phase extraction technique was developed using a novel polypyrrole-polyamide nanofiber sheet, fabricated by electrospinning method. The applicability of the new nanofiber sheet was examined as an extracting medium to isolate malathion as a model pesticide from aqueous samples. Solvent desorption was subsequently performed in a microvial, and an aliquot of extractant was injected into gas chromatography-mass spectrometry. Various parameters affecting the electrospinning process including monomer concentration, polyamide content, applied voltage, and electrospinning time were examined. After fabricating the most suitable preparation conditions, influential parameters on the... 

Preparation, characterization and evaluation of new generation of micro-filters based on polyacrylonitrile electrospun nanofiberous membrane (ENM) were thoroughly investigated. First, quantitative relationships between average diameter, bead area density of nano-fibers and certain electrospinning parameters, i.e., concentration, voltage, spinning distance, and feed rate, were established by empirical modeling based on a central composite design. The analysis revealed that concentration, voltage and distance are the significant parameters. Also, adequacy checking indicated the appropriateness of fit for the models. Afterwards, bead-free ENMs with diameter of 100-500 nm were prepared and... 

Electrospun hybrid membranes were synthesized using electrospinning of Poly (vinylidenefluoride) - titanium tetraisopropoxide (PVDF-TTIP) sol. Asymmetric post-treatment of membrane conducted for deprotonation of titanate and making hydrophilic/hydrophobic dual characteristics. The membranes were characterized by various methods such as wettability, scanning electron microscopy, infrared spectroscopy, X-ray diffraction and liquid entry pressure tests. For evaluating the separation performance, these membranes were applied in the VMD process to treat water heavy metal contaminants. The effects of operating parameters such as flow rate, temperature and membrane properties as porosity, on... 

Three-dimensional (3D) polyamide scaffolds were fabricated by applying a solvent bath as the collecting element. Electrospun nanofibers were immersed into the solvent bath to give a material with a laminated 3D texture. In parallel, 2D nanofibers were synthesized and utilized as microextractive phases in a needle trap device to compare the capabilities of 2D and 3D materials in terms of headspace extraction of various chlorobenzenes (chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,3,4-tetrachlorobenzene). The results demonstrate the superiority of 3D nanofibrous scaffolds over 2D mats. The porosity, morphology, and thermal stability of the 3D scaffolds...