Muhammet Ceylan

Superhydrophobic electrospun nanofibers

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.

Study of superhydrophobic electrospun nanocomposite fibers for energy systems

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.

Recent progress on conventional and non-conventional electrospinning processes

Electrospinning is a process of producing micro- and nanoscale fibers using electrostatically charged polymeric solutions under various conditions. Most synthetic and naturally occurring polymers can be electrospun using appropriate solvents and/or their blends. Because of the fascinating properties of electrospun fibers, electrospinning has recently attracted enormous attention worldwide. Initially, this method did not receive much industrial attention due to lower production rates, costs, and lack of interest in size, shape, and flexibility of electrospun nanofibers. However, with the advancement of needleless electrospinning, multiple needles in series, near-field electrospinning techniques, and nanotechnology in particular, this is no longer an issue. This paper outlines the recent progress on the production of various sizes and shapes of fibers using conventional and non-conventional electrospinning processes (e.g., rotating drum and disc, translating spinnerets, rotating strings of electrodes in polymeric solutions, and forcespinning) and presents a complete view of electrospun fiber productions techniques and the resultant products’ applications in different fields to date.

Nanofibers support oligodendrocyte precursor cell growth and function as a neuron-free model for myelination study

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 copolymer. 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 copolymer 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 copolymer nanofibers than those on PCL nanofibers alone.

An Electrospun Polyaniline Nanofiber as a Novel Platform for Real-Time COX-2 Biomarker Detection

The presence of Cyclooxygenase-2 (COX-2) biomarker has been associated with the development of certain types of cancer such as breast cancer. Moreover, reliable quantification of COX-2 as an enzyme responsible for pain and inflammation is vital. Here we demonstrate the feasibility of sensitive COX-2 detection via integration of nanoporous polyaniline fibers on the microfabricated platform to develop a label-free biosensor. Highly porous polyaniline nanofibers were fabricated in different diameters and integrated on the interdigitated microelectrodes to develop electrochemical platforms. Characterization results revealed that the smaller diameter improved the sensitivity of the biosensor due to enhancement in the specific surface area. The developed biosensor was able to detect analyte as low as 0.1pg/mL with a large dynamic linear range of 10fg/mL to 1μg/mL. The fabricated sensor showed remarkable sensitivity towards COX-2 antigen suggesting the significant contribution of this nanofiber based platform to the enhanced sensitivity in COX-2 analyte detection.Copyright

Development of low pressure filter testing vessel and analysis of electrospun nanofiber membranes for water treatment

A low-pressure filtration unit incorporated with polymeric electrospun polyvinyl chloride (PVC) fiber membranes was designed and fabricated for the treatment of waste water in order to improve its quality. This custom-made pressure filter was designed according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC). A scanning electron microscope (SEM) was used to characterize the electrospun membranes. In order to increase the hydrophilicity and filtration rates of PVC membranes, a lower dosage of poly (ethylene oxide) was added to the PVC solution prior to the electrospinning process. The filter was found to be well suited for the reduction of larger suspended solids, turbidity, and odor. It was demonstrated that this type of filtration membrane could be manufactured at a lower cost and not require electricity or any other external power source to achieve high flow rates. This technology could even be used to enhance the quality of tap water in many places, such as Africa. Another application could be a pre-filtration of reverse osmosis (RO) or other ultrafine filtration systems, to increase the life of the primary filter while decreasing fouling and maintenance.Copyright

Enhancing the superhydrophobic behavior of electrospun fibers via graphene addition and heat treatment

Polyvinyl chloride (PVC) fibers incorporated with graphene nanoflakes were produced using electrospinning technique, and then superhydrohobicity of the electrospun nanofibers were investigated as a function of inclusion and temperature. In the absence of graphene, water contact angle of the fibers is below 140°; however, the water contact angle values of 0.5, 1, 2 and 4% graphene in fibers become 142, 152, 165 and 166°, respectively. Using a heat treatment, the contact angle values of samples also increase up to glass transition temperature of PVC. This indicates that graphene inclusions in the polymeric fibers and temperature drastically change the surface morphology and chemistry, which results in higher contact angles. The reason behind this phenomena may be the formation of smaller nanosized graphene bumps on the fiber surface that make the contact area between the droplet and the fiber extremely small. As a result, this process minimizes attractive forces between the water molecules and surface atoms of the rough nanocomposite fibers to bead up and rolls off.Copyright