Thickness Of Nanofiber Layer Research Articles

Acoustic characterization of nanofibers for optimization with porous substrate.

Nanofiber-porous systems comprising a porous substrate overlaid with nanofiber weave offer the potential for higher acoustic absorption than the substrate alone with negligible increase in thickness. The characterization of nanofibers from acoustic measurements is investigated in this work, and a regression model for predicting their acoustic properties from a single physical parameter is proposed to enable the design of nanofiber-porous systems directly from fabrication parameters. Characterization as a resistive screen via Johnson-Champoux-Allard and lumped element models for transfer matrix computations of absorption coefficient for nanofiber-porous systems exhibited good agreement with the measured spectra. The lumped element model was chosen as it was defined by fewer parameters and did not require nanofiber layer thickness measurements, eliminating the associated uncertainty. A regression model for lumped element parameters vs areal density established a design tool based on a single, easily measured physical property for optimized absorption at target frequencies without prior acoustic characterization of the nanofiber layer, enabling the analysis of complex acoustic networks incorporating nanofiber-porous systems. Practical considerations of applying adhesives at the nanofiber-porous interface were studied to evaluate possible enhancement of acoustic performance. For comparison with prior work by others, flow resistances from physical measurement and acoustic characterization were compared.

Investigation of mechanical properties of electrospun poly (vinyl chloride) polymer nanoengineered composite

Nanofiber membranes are extensively used in ultra- and micro-filtration purposes due to their high surface-to-volume ratio. However, nanofiber membranes do not have adequate strength to withstand forces acting on the filter surface, especially when using very low porosity membranes. In this study, PVC nanofiber mats and nanofiber composite membranes were fabricated through electrospinning and solvent casting technology. The membranes were characterized using scanning electron microscopy (SEM), porosimetry, and tensile strength tests. Analysis indicated that electrospun mats contain varying pore sizes (nano to micro) whose frequencies within the mat vary with fiber diameter. It was also established that mats fabricated from low solution concentration contain the largest percentage of pores. The mats’ tensile strength varied with fiber packing density, fiber assembly, and the density of fiber-to-fiber contact points. The tensile properties of the nanofiber composite membranes were found to be between those of the constituents and changed with change in the nanofiber layer thickness. The fabricated nanofiber composite membranes are intended for use in applications such as air ultra-filtration, acoustic filtration etc. The high porosity and small mesh pore size of electrospun nanofiber mats allow for removal of ultra-fine particles or microbes from contaminated air, water or other media.

PVA-co-PE Nanofibrous Filter Media with Tailored Three-Dimensional Structure for High Performance and Safe Aerosol Filtration via Suspension-Drying Procedure

High efficient filtration of air pollutants exerts a great demand for nanofiber-based materials with superior structures. In this work, a mixed solution of tert-butyl alcohol (TBA) and water was employed to stably disperse PVA-co-PE nanofibers. Nanofibrous filter media based on PP nonwoven fabric substrate with various porosity were then prepared via three nanofiber-suspension drying techniques: spray-air-drying, spray-freeze-drying, and container loading-freeze-drying. The prepared nanofiber composite filter media with average nanofiber diameter about 155 nm present controllable three-dimensional structure: nanofiber layer porosity increases from 76.6% to 97.3%, various pore sizes increase from 0.493 to 2.268 μm, as well as an increased nanofiber layer thickness from about 10 to 55.3 μm for filter media with 2.667 g/m2 nanofiber coverage density (NFCD). On the basis of the structure, filter media possess a best comprehensive filtration performance with the quality factor 1.110 mmH2O–1 (99.955% and 6.73 m...

Development of Protective Clothing against Nanoparticle Based on Electrospun Nanofibers

In this paper, the development of efficient protective clothing against nanoparticulate aerosols is presented. Nanofibrous mats of polyamide 6 (PA6) were deposited onto a nonwoven viscose substrate by electrospinning technique. The influence of electrospinning parameters, including solution concentration, viscosity, and conductivity, was studied for the production of nonwovens with controlled fiber diameter showing a size distribution ranging from 66 to 195 nm. By varying several process parameters, textiles with different thickness of the nanofiber layer and thus air permeability were obtained. A hot‐press lamination process using a thermoplastic resin as glue was applied to improve the adhesion of the nanofiber layer onto the textile support. After 1500 cycles of repeated compression and torsion, the nanofiber layer was still firmly attached to the support, while mechanical damage is visible in some areas. The penetration of NaCl particles with diameter ranging from 15 to 300 nm through the electrospun textiles was found to be strongly dependent on nanofiber layer thickness. A really thin nanofiber coating provides up to 80% retention of 20 nm size particles and over 50% retention of 200 nm size nanoparticles. Increasing the thickness of the nanofiber mat, the filtration efficiency was increased to over 99% along the whole nanoparticle range. The results obtained highlight the potential of nanofibers in the development of efficient personal protective equipments against nanoparticles.

Effect of face velocity, nanofiber packing density and thickness on filtration performance of filters with nanofibers coated on a substrate

The objective of this study is to evaluate the effect of face velocity, nanofiber packing density and nanofiber layer thickness on filtration efficiency and pressure drop of filters with nanofibers coated on a substrate. The substrate is a non-woven microfiber medium with negligible filtration efficiency and pressure drop as compared to nanofiber layer. The nanofiber layer is composed of electrospun polyethylene oxide nanofibers with mean diameter equals to 208 nm. Test aerosol is sodium chloride with size ranging from 50 to 480 nm. Experimental results show that the most penetrating particle size decreases from 140 to 90 nm when nanofiber packing density increases from 3.9 to 36 × 10 −3. When face velocity is increased from 5 to 10 cm s −1, the filtration efficiency generally decreases, and the reduction becomes larger at smaller particle sizes especially for those below 100 nm. By maintaining nanofiber packing density at 8.7 × 10 −2 and almost triple the nanofiber layer thickness, the most penetrating particle size decreases slightly from 140 to 120 nm. This suggests nanofiber layer thickness has less prominent effect on most penetrating particle size than nanofiber packing density. By adding more nanofibers on microfiber substrate in a single layer especially under high fiber packing, the pressure drop across the filter elevates without significantly improving the filtration efficiency exhibiting a diminishing return behavior. Hence, the method of “multi-layering” is proposed to fabricate nanofiber filter with greatly reduced pressure drop. This is advantageous for high efficiency applications with nanofibers of high packing density.

The influence of fiber thickness, wall thickness and gap distance on the spiral nanofibrous scaffolds for bone tissue engineering

We have developed a 3D nanofibrous spiral scaffold for bone tissue engineering which has shown enhanced cell attachment, proliferation and differentiation compared to traditional cylindrical scaffolds due to the spiral structures and the nanofiber incorporation. Some important parameters of these spiral scaffolds including gap distance, wall thickness and especially fiber thickness are crucial to the performance of the spiral structured scaffolds. In this study, we investigated the fiber thickness, gap distance and wall thickness of the spiral structure on the behavior of osteoblast cells. The human osteoblast cells are seeded on spiral structured scaffolds with various fiber thickness, gap distance and wall thickness and cell attachment, proliferation, differentiation and mineralized matrix deposition on the scaffolds are evaluated. It was found that increasing the thickness of nanofiber layer not only limited the cell infiltration into the scaffolds, but also restrained the osteoblastic cell phenotype development. Moreover, the geometric effect studies indicated that scaffolds with the thinner wall and gap distance 0.2 mm show the best bioactivity for osteoblasts.