This review describes state-of-the-art scientific and technological developments of electrospun nanofibers and their use in self-cleaning membranes, responsive smart materials, and other related applications.Superhydrophobic self-cleaning, also called the lotus effect, utilizes the right combinations of surface chemistry and topology to form a very high contact angle on a surface and drive water droplets away from it. The high-contact-angle water droplets easily roll off the surface, carrying with them dirt, particles, and other contaminants by way of gravity. A brief introduction to the theory of superhydrophobic self-cleaning and the basic principles of the electrospinning process is presented. Also discussed is electrospinning for the purpose of creating superhydrophobic self-cleaning surfaces under a wide variety of parameters that allow effective control of roughness of the porous structure with hydrophobic entities. The main principle of electrospinning at the nanoscale and existing difficulties in synthesis of one-dimensional materials by electrospinning are also covered thoroughly. The results of different electrospun nanofibers are compared to each other in terms of their superhydrophobic properties and their scientific and technological applications.

Polystyrene (PS) and polyvinyl chloride (PVC) fibers incorporated into TiO(2) nanoparticles and graphene nanoflakes were fabricated by an electrospinning technique, and then the surface morphology and superhydrophobicity of these electrospun nanocomposite fibers were investigated. Results indicated that the water contact angle of the nanocomposite fiber surfaces increases to 178° on the basis of the fiber diameter, material type, nanoscale inclusion, heat treatment, and surface porosity/roughness. This is a result of the formation of the Cassie-Baxter state in the fibers via the nanoparticle decoration, bead formation, and surface energy of the nanofiber surface. Consequently, these superhydrophobic nanocomposite fibers can be utilized in designing photoelectrodes of dye-sensitized solar cells (DSSCs) as self-cleaning and anti-icing materials for the long-term efficiency of the cells.

SUMMARY The present study reports the fabrication and characterization of electrospun polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA) nanofiber separators embedded with graphene nanoflakes. Different weight percentages (0, 2, 4, and 8 wt%) of graphene nanoflakes were dispersed in dimethylformamide (DMF) and ethanol using sonication and high‐speed agitations, and then PAN and PMMA powders were added to the dispersions prior to the mixing process. Ratios of 85:15 for DMF : PAN and 88:12 for ethanol : PMMA were chosen during the dispersion and dissolution processes. After the fabrication of the membranes via the electrospinning process, thermal, dielectric, ionic, and surface hydrophobic properties of the PAN and PMMA nanofiber separators were investigated in detail. Test results revealed that the physical properties, such as wettability, dielectric constant, ionic conductivity, and thermal conductivity values of the nanocomposite separators were significantly increased as a function of graphene concentrations. For example, the water contact angle, ionic conductivity, dielectric constant, and thermal conductivity values of the membranes were increased from 120° to 145°, 3.31 × 10−4 to 5.52 × 10−4 S/m, 3.5 to 8.5 W/m K, and 1.0 to 5.0 W/m K, respectively, when the graphene concentration was increased from 0% to 8% in PMMA. Similar trends were observed in the PAN fibers, as well. Lithium‐ion (Li‐ion) batteries have become the major source of power for portable electronic devices, and because separators are one of the major components of these batteries, the present alternatives can be an option for long‐lasting Li‐ion battery fabrications. Copyright © 2014 John Wiley & Sons, Ltd.

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Recycled high-density polyethylene (HDPE) was incorporated with graphene nanoflakes in a solvent at different concentrations (0, 1, 2, 4, and 8 wt%), and then the mechanical, thermal, electrical, and surface hydrophobic properties of the resultant nanocomposites were determined using universal tensile testing, thermal comparative, capacitance bridge, and goniometer techniques, respectively. The test results revealed that the mechanical, thermal, and dielectric properties of the polymer matrix nanocomposites were increased as a function of graphene concentrations, whereas the surface hydrophobic values were slightly increased at lower concentrations and then reduced at higher concentrations. These improvements occur mainly because of the excellent properties of graphene nanoflakes, such as tensile strength (150 GPa), Young's modulus (1.0 TPa), thermal conductivity (4,840-5,300 W/m K), electrical conductivity (1.3 3 10 6 S/cm), electrical current density (10 13 A/cm 2 ), surface hydrophobicity (>120 ), and surface smoothness/roughness (<1 nm). The worldwide consumption of polymeric products has been drastically growing, and consequently polymeric waste materials have been rising up, as well. Although the plastic recycling and reprocessing rates are considerably high, physical properties and economical values of the recycled plastics are significantly low, limiting the reuse of recycled plastics in many industrial applications. As a result, this study provides a detailed explanation of how to improve recycled plastics into highly valued new products for applications in various industries, such as transportation, energy, electronic, construction, and so forth. POLYM. COMPOS., 36:1565-1573

Nanofiber-based scaffolds may simultaneously provide immediate contact guidance for neural regeneration and act as a vehicle for therapeutic cell delivery to enhance axonal myelination. Additionally, nanofibers can serve as a neuron-free model to study myelination of oligodendrocytes. In this study, we fabricated nanofibers using a polycaprolactone and gelatin co-polymer. The ratio of the gelatin component in the fibers was confirmed by energy dispersive x-ray spectroscopy. The addition of gelatin to the polycaprolactone (PCL) for nanofiber fabrication decreased the contact angle of the electrospun fibers. We showed that both polycaprolactone nanofibers as well as polycaprolactone and gelatin co-polymer nanofibers can support oligodendrocyte precursor cell (OPC) growth and differentiation. OPCs maintained their phenotype and viability on nanofibers and were induced to differentiate into oligodendrocytes. The differentiated oligodendrocytes extend their processes along the nanofibers and ensheathed the nanofibers. Oligodendrocytes formed significantly more myelinated segments on the PCL and gelatin co3polymer nanofibers than those on PCL nanofibers alone.

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This study deals with two biomedical subjects: corrosion rates of polyelectrolyte-coated magnesium (Mg) alloys, mainly used for biomedical purposes, and antibacterial properties of these alloys. Thin sheets of Mg alloys were coated with cationic polyelectrolyte chitosan (CHI) and anionic polyelectrolyte carboxymethyl cellulose (CMC) using a layer-by-layer coating method and then embedded with antibacterial agents under vacuum. Electrochemical impedance spectroscopy was employed to analyze these samples in order to detect their corrosion properties at different conditions. In the electrochemical analysis section, a corrosion rate of 72 mille inches per year was found in a salt solution for the sample coated with a 12 phosphonic acid self-assembled monolayer and 9 CHI/CMC multilayers. In the antibacterial tests, gentamicin was used to investigate the effects of the drug embedded with the coated surfaces against the Escherichia coli (E. coli) bacteria. Antibacterial studies were tested using the disk diffusion method. Based on the standard diameter of the zone of inhibition chart, the antibacterial diffusion from the surface strongly inhibited bacterial growth in the regions. The largest recorded diameter of the zone of inhibition was 50 mm for the pre-UV treated and gentamicin-loaded sample, which is more than three times the standard diameter.