Nabyl Khenoussi

Effect of nanofiber diameter on water absorption properties and pore size of polyamide-6 electrospun nanoweb

Electrospinning is a common method used to produce nanofiber from almost all types of polymers. By changing effective parameters of this process, especially polymer solution concentration, it is possible to produce nanoweb that consists of nanofibers with different averages of diameter. Here, the effect of nanofibers’ diameter on textural properties (water absorption time and pore size) of polyamide-6 nanoweb has been studied. In this way, three nanowebs with nanofibers’ average diameter of 111, 151, and 318 nm were electrospun from three different concentrations of 15, 20, and 25 wt%, respectively. Contact angle measurement and mercury porosimetry were used to investigate the nanowebs’ water absorption properties and porosity (pore size). The results from the water absorption test demonstrated that the absorption time of a 2 µL water droplet was remarkably shorter for electrospun nanoweb with larger nanofiber diameter. Nanowebs electrospun from 15 and 20 wt% concentrations had roughly the same absorption regime, while for 25 wt% the absorption regime was totally different. Mercury porosimetry of electrospun nanowebs revealed that the pore size in the nanoweb structure decreased by decreasing average diameter of nanofibers. The results of this study showed that contact angle measurement and mercury porosimetry tests could be used as complementary methods to scanning electron microscopy and atomic force microscopy and presented as promising methods to study the textural and physical properties of electrospun nanowebs.

Preparation and morphology study of carbon nanotube reinforced polyacrylonitrile nanofibres

Abstract The aim of this study was to prepare polyacrylonitrile (PAN) nanofibres filled with multiwall carbon nanotubes (CNT) through an electrospinning process of a dispersion of CNT in a DMF solution of PAN. The rheological properties of pure PAN solutions and of CNT dispersion in PAN solutions were studied as the viscosity of the spun solution plays an important role in the spinning process. If the PAN solutions behave like a Newtonian fluid, CNT dispersions exhibit a more complex rheological behaviour characterised by the apparition of a flowing threshold. CNT dispersions containing 0 to 2·5% of CNT were electrospun in a homemade device. The morphology of prepared nanofibres was examined using scanning electron microscopy and atomic force microscopy. Nanofibres containing CNT show a mean diameter three times higher than the one spun without CNT and also a higher surface roughness. These observations suggest that CNT aggregates are not destroyed and create this particular morphology.

Structural observation of nanofibre surface by AFM

Abstract Electrospinning, a process which allows the production of nanofibres, was recently rediscovered. Electrospinning uses the electrostatic attraction between an electrically charged polymer solution and a collector related to the ground. Polyamid-6 (PA-6) was electrospun in different spinning conditions such as the distance between needle tip and collector, the voltage and the needle tip geometry. Using scanning electron microscopy (SEM) and atomic force microscopy (AFM), the nanoweb longitudinal and cross-sectional morphologies were evidenced. Different morphologies, exhibiting various nanoroughnesses, were observed, which could be related to the experimental electrospinning parameters. These structural differences could be attributed to instability of the polymer jet and to the intrinsic behaviour of the electrospinning solution.

Quantitative approaches of nanofibers organization for biomedical patterned nanofibrous scaffold by image analysis: Quantitative approaches of nanofibers organization for biomedical patterned nanofibrous scaffold by image analysis

This study proposes a novel design of a laboratory built static collector using the 3D printing technology. This new collector produces aligned-to-random nanofibers in nanofibrous scaffold through electrospinning process. A design of experiment (DOE), based on response surface, analyzes the effect of the main process parameters; concentration, voltage, and distance; on the responses diameter and orientation. A quantifying approach has been used to investigate the orientation of nanofibers in the produced patterned scaffold through Fourier transforms method. The obtained results have proven a good potential to be used in tissue engineering application, especially for cells requiring specific guidance.

Novel 3D electrospun polyamide scaffolds prepared by 3D printed collectors and their interaction with chondrocytes

ABSTRACT Electrospinning is significantly one of the simple and versatile methods for producing micro- and nanofibrous scaffolds. Its assembly can be modified in different ways to combine material properties with different morphological structures for biomedical applications. In this process, collector design plays an important role to determine the nanofiber orientation in electrospun nanoweb. In this work, 3D patterned scaffolds were produced by electrospinning of polyamide-66 solution on different 3D collectors that have been obtained. The aim of this work is to investigate the attachment of the chondrocyte cells on the prepared electrospun scaffolds that have different types of nanofiber orientations that could be used in tissue engineering applications. GRAPHICAL ABSTRACT

An in Situ Crystal Growth of Metal Organic Frameworks-5 on Electrospun PVA Nanofibers

Abstract In this study, a simple, general and straightforward method for growing metal-organic frameworks (MOFs) crystals directly on nanofibers is presented. A chelating polymer was first blent with metal cation and then electrospun. The obtained nanofibers were immersed in a linker solution. Metal cations were released and the metal-organic frameworks crystals were grown on the fibers’ surface. In this work, this method was tested with polyvinyl alcohol as chelating polymer, Zn2+ as metal cation and Terephthalic acid as linker. The pair cation/linker corresponds to the MOF-5. The latter is a robust metal organic framework formed from Zn4O nodes with 1,4-benzodicarboxylic acid struts between the nodes. SEM images revealed that the MOF-5 nanocrystals have grown along the PVA/Zn2+ nanofibers that served as the crystals’ growth template by providing the Zn2+ ions. This result was also confirmed by infrared spectroscopy, which indicates the presence of characteristic bands of MOF-5 in the modified nanofibers spectrum. Moreover, the X-ray diffraction showed that MOF-5 material was well crystallized on the nanofibers surface according to a cubic symmetry with a space group Fm-3m and a lattice constant a = 25.8849 Å.

Structuring of electrospun nanofiber mats by 3D printing methods

Electrospinning is significantly one of the simple and versatile methods for producing micro- and nanofibrous scaffolds. Its assembly can be modified in different ways to combine material properties with different morphological structures for diverse applications ranging from tissue engineering to nanocomposite fabrication; however, electrospun nanofibers are generally deposited as a randomly oriented mat on a flat collector that limits their applications. In electrospinning process, collector design plays an important role to determine the nanofiber orientation in electrospun nanoweb. The aim of this chapter is to highlight several methods to control the arrangement of 2D/3D nanofibers, such as the use of a mechanical device and parallel electrode collectors. Subsequently, additive manufacturing (AM) methods are presented to describe different methods to achieve various geometries of collectors to be used to produce complex nanofibrous architectures during electrospinning. Finally, our work will be described as a novel method, combining electrospinning and 3D printing technology to produce patterned scaffold consisting oriented and random nanofibers. 3D patterned scaffolds were produced by electrospinning of polyamide 66/formic acid solution on different 3D collectors that have been obtained. The attachment of the chondrocyte cells on the prepared electrospun scaffolds, which have different types of nanofiber orientations that could be used in tissue engineering applications, was investigated.