Polyvinylidene Fluoride Nanofiber Membrane Research Articles

All-Nanofiber-Based Ultralight Stretchable Triboelectric Nanogenerator for Self-Powered Wearable Electronics

The flexible and stretchable electronics have been considered as next-generation electronics. Stretchable triboelectric nanogenerators (S-TENGs) with both multifunction and comfort have become a hot field of research for wearable electronic devices recently. Here, we designed an all-nanofiber-based, ultralight, S-TENG that could be softly attached on skins for motion energy harvesting and self-powered biomechanical monitoring. The S-TENG consisted of only two nanofiber membranes: a polyvinylidene fluoride nanofiber membrane (PVDFNM) supported by thermoplastic polyurethane nanofiber membrane (TPUNM) was used as the frictional layer, and a multiwalled carbon nanotube (MWCNT) conductive material screen-printed on the TPUNM was used as the electrode layer. Due to the excellent stretchability of TPUNM, the S-TENG could generate electricity under various types of deformation, and regains its original performance after intense mechanical extension, even if it is partially cut or damaged. Owing to the great elect...

Development of Novel Membranes Based on Electro–spun Nanofibers and Their Application in Liquid Filtration, Membrane Distillation and Membrane Adsorption

Electro–spinning is known as a simple and versatile method to produce nonwoven membranes made out of nanofibers. A wide range of polymers and blends can be used to yield nanofibers. Commonly used membrane polymers such as cellulose acetate (CA), polysulfone (PSU) and polyvinylidene fluoride (PVDF) have been successfully electro–spun to form nonwoven nanofiber membranes for water filtration. Investigations have revealed that electro–spun nanofibrous membranes (ENMs) possess high–flux rates and low transmembrane pressure. These characteristics are due to its (1) high porosity, (2) interconnected open pore structure and (3) tailorable membrane thickness. Although electro–spun membranes have been extensively studied for decades and successfully commercialized as air filtration membrane, they have not been applied for water treatment. The nanofiber membranes were used recently at the Industrial Membrane Research Laboratory of the University of Ottawa with the collaboration of Nanoscience & Nanotechnology Initiative of the National University of Singapore for the following investigations.Removal of latex particles from water: PVDF nanofiber membranes were subjected to filtration of latex particles (0.1 to 10 μm) at the feed pressure of 0.6 bar gauge [1, 2].Seawater desalination by membrane distillation: PVDF nanofiber membranes were subjected to desalination of aqueous NaCl solutions by air gap membrane distillation [3, 4].Trihalomethanes (THMs) and haloacetic acids (HAAs) removal by carbonized polyacrylnitrile (PAN) nanofiber membranes [5, 6].

Polyvinylidene fluoride nanofiber coated polypropylene nonwoven fabric as a membrane for lithium-ion batteries

Polyvinylidene fluoride (PVdF) membranes in spite of having many critical properties necessary for lithium-ion batteries, do not have satisfying thermal and mechanical resistance. The goal of this study was to combine the good mechanical and thermal properties of PP nonwoven fabric with the excellent electrochemical properties of PVdF nanofibers to exploit a high-performance membrane for lithium-ion batteries. This work reports the preparation of PVdF nanofiber membranes using electrospinning on a polypropylene (PP) spunbonded nonwoven fabric and an aluminum foil followed by a hot-pressing treatment. The morphology and size of the membranes were studied by the scanning electron microscopy. The tensile strength of the membrane with the PP support was superior to the PVdF membrane. Thermal stability of the prepared membranes was determined using the TGA method and the dimensional stability was investigated by measuring the shrinkage ratio at 105 °C. The results have shown that the PVdF/PP membrane was thermally more stable than the PVdF and the commercial Celgard 2325 membranes. The batteries using PVdF/PP membrane exhibited higher electrochemical oxidation limit, better cycling performance and less discharge capacity fading during 100 cycles compared to PVdF and Celgard membranes. The results of this study showed that PVdF/PP membrane is a promising advanced membrane in lithium-ion batteries.

Preparation of Polyvinylidene Fluoride Nanofiber Membrane and Its Antibacterial Characteristics with Nanosilver or Graphene Oxide

Polyvinylidene fluoride (PVdF) (Kynar 761) nanofibers were prepared by electrospinning at an external voltage of 6-10 kV, a traveling distance of 7-15 cm and flow rate of 0.4-1 ml/hr. Although the diameter of the fiber was not significantly changed, the electrospinning conditions affected the overall distribution of diameter. This is probably due to the interactions, both attraction and repulsion, of positive charges on polymer solutions and the electrically grounded collector. Especially, the effect of voltage on the distribution of diameter was investigated in this study. The final PVdF nanofiber membrane showed narrow pore-size distribution and high water flux compared with the commercial MF membrane. PVdF nanofiber membranes incorporated nanosilver or graphene oxide were also prepared as nanosilver and graphene have an antibacterial activity. It was found that more than 200 ppm of silver nanoparticles in the PVdF nanofiber had 99.9% of growth inhibition of Staphylococcus aureus and Klebsiella pneumonia. It was also found that 0.2 wt% of graphene oxide in the PVdF electrospinning solution had 99.6% of disinfection property to E-Coli.

Western Blot Membrane Composed of Electrospun Polyvinylidene Fluoride Nanofiber Membrane and Polyethylene Terephthalate Sheet

In a previous study, an electrospun polyvinylidene fluoride (PVDF) nanofiber membrane was developed for Western blotting. The membrane exhibited high sensitivity and high binding capacity for the detection of protein bands that was unlike that observed for conventional, microphase separation-based porous PVDF membranes. Nevertheless, the PVDF nanofiber membrane is quite expensive. The objective of this study was to develop an economical Western blot membrane using a hybrid electrospun PVDF nanofiber and polyethylene terephthalate (PET) sheet. The results showed that the detection sensitivity of the 4 gram per square meter (gsm) membrane was similar to those of the electrospun PVDF nanofiber membrane only, and the 7 gsm PVDF nanofiber membranes on a PET sheet and the electrospun PVDF nanofiber membrane. This means the protein detection sensitivity is not proportional to the thickness of the PVDF nanofiber membrane. The 4 gsm PVDF nanofiber membrane on a PET sheet can be used to detect proteins with high sensitivity and economic efficiency.

Surface Modification of Electrospun Polyvinylidene Fluoride Nanofiber Membrane by Plasma Treatment for Protein Detection

Electrospun polyvinylidene fluoride (PVDF) nanofiber membranes have 3-dementional (3-D) open pore channel and hence have excellent application potential in Western blot. In this study we have modified electrospun PVDF nanofiber membrane by argon (Ar) plasma treatment to improve the surface hydrophilic and detection sensitivity. The results showed that the detection sensitivity of the Ar plasma-treated PVDF nanofiber membrane increased with increasing plasma treatment time without the need for a methanol pre-wet step. This suggests that the Ar plasma treated PVDF nanofiber membrane can be useful in Western blot with high sensitivity and without methanol pre-wet step.

Fabrication of polyvinylidene fluoride (PVDF) nanofiber membranes by electro-spinning for direct contact membrane distillation

The main challenges for membranes used in membrane distillation (MD) are well-designed porous structure and hydrophobic surface property. Hydrophobic nanofiber membranes possess high hydrophobicity, high surface porosity and adjustable pore sizes and membrane thickness, which make them an attractive candidate as MD membrane. The current study aims to fabricate and optimize polyvinylidene fluoride (PVDF) nanofiber membranes for MD application. Scanning electron microscopy (SEM), capillary flow porometer, geniometer, a homemade setup for liquid entry pressure (LEP) measurement and direct contact MD (DCMD) setup were used to characterize the resultant nanofiber PVDF membranes. Polymer dope compositions, spinning parameters such as sprayer moving speed and chamber moisture were optimized to examine their effects on pore size distribution of the membranes. Inorganic additives were also added into the dope to improve the electro-spinability of diluted polymer dopes in order to further decrease membrane pore size. Meanwhile, a heat-press post-treatment was considered as a necessary step to improve fresh nanofiber membrane integrity, enhance water permeation flux and help prevent membrane pores from wetting in DCMD operation. The experiment confirmed that all the electrospun membranes exhibit a rough surface with high hydrophobicity (>135° water contact angle). The post-treated PVDF nanofiber membranes were able to present a steady water permeation flux of about 21kgm−2h−1 throughout the entire testing period of 15h, using a 3.5wt% NaCl solution as the feed under the feed and permeate inlet temperatures of 323K and 293K, respectively. This result was better than these of commercial PVDF membranes and the nanofiber PVDF-clay membrane reported in literature, suggesting the competency of PVDF nanofiber membranes for DCMD applications.

Preparation of PVdF nanofiber membranes by electrospinning and their use as secondary battery separators

This paper reports the development and characterization of polyvinylidene fluoride (PVdF) nanofiber separators for high rate discharge secondary batteries. The preparation of PVdF nanofiber separators was performed by an electrospinning method. The pore properties of PVdF nanofiber separators were optimized by variation of spinning conditions, after post treatment and sheet forming. The optimized PVdF nanofiber separators were characterized by scanning electron microscopy (SEM), pore properties, mechanical/thermal characteristics, water/electrolyte uptakes and electric properties. The high porosity (48%) led to a high electrolyte uptake level (142 wt%) which is necessary for thin batteries. The PVdF nanofiber separators reached higher tensile strength of 14.8 MPa/cm 2 and elongation of 117% and compared to commercial PE separator, they also exhibit higher thermal stability, up to 135 °C under air. Also, PVdF nanofiber separators showed excellent performance in tests of cyclic fading rates and high rates of discharge.

Production of drinking water from saline water by air-gap membrane distillation using polyvinylidene fluoride nanofiber membrane

Polyvinylidene fluoride nanofiber membrane could be used in membrane distillation (MD) to produce drinking water (NaCl concentration <280 ppm) from a saline water of NaCl concentration 6 wt.% by air-gap membrane distillation. This was the first attempt to use electro-spun nanofiber membrane in MD. This new approach may eventually enable the MD process to compete with conventional seawater desalination processes such as distillation and reverse osmosis.