Expanded Polytetrafluoroethylene Membranes for Vascular Stent Coating: Manufacturing, Biomedical and Surgical Applications, Innovations and Case Reports

Coated stents are defined as innovative stents surrounded by a thin polymer membrane based on polytetrafluoroethylene (PTFE)useful in the treatment of numerous vascular pathologies. Endovascular methodology involves the use of such devices to restore blood flow in small-, medium- and large-calibre arteries, both centrally and peripherally. These membranes cross the stent struts and act as a physical barrier to block the growth of intimal tissue in the lumen, preventing so-called intimal hyperplasia and late stent thrombosis. PTFE for vascular applications is known as expanded polytetrafluoroethylene (e-PTFE) and it can be rolled up to form a thin multilayer membrane expandable by 4 to 5 times its original diameter. This membrane plays an important role in initiating the restenotic process because wrapped graft stent could be used as the treatment option for trauma devices during emergency situations and to treat a number of pathological vascular disease. In this review, we will investigate the multidisciplinary techniques used for the production of e-PTFE membranes, the advantages and disadvantages of their use, the innovations and the results in biomedical and surgery field when used to cover graft stents.

Kinetics study of anodic electrophoretic deposition for polytetrafluoroethylene (PTFE) coatings on AZ31 magnesium alloy

Electrophoretic deposition (EPD) coating has become a hot topic due to its simple experiment, wide application, and wide material range. In this study, the PTFE coating was successfully prepared by electrophoretic deposition through the systematic study of electrophoretic deposition kinetics. In particular, in the dispersion system with ethanol as solvent, Nafion and NaOH were simultaneously added as additives to obtain a beneficial synergistic effect on PTFE electrophoretic deposition. And the best additive scheme is: when the concentration of PTFE was 6 g·L− 1 and the deposition time was increased to 20 min, adding 0.10 g·L− 1 Nafion and 0.10 mM NaOH simultaneously. Compared with the scheme with Nafion being only additive, the addition of NaOH can improve the deposition rate from 0.16 mg·cm− 2 to 0.98 mg·cm− 2, and the deposition rate increases by about 6 times. According to electrophoretic deposition kinetics, there is an obvious critical transition time between linear and parabolic regions in the preparation of the coating. Prolonging the arrival of critical transition time is beneficial to effectively achieve stable growth of the coating in a longer time. It is found that a more ideal additive can not only increase the deposition rate of coating, but also significantly accelerate the arrival of critical transition time. Meanwhile, the deposition voltage also has an important influence on the critical transition time. Increasing the voltage can improve the deposition speed but shorten the critical transition time. Therefore, the application of deposition voltage needs to strike a balance between deposition rate and critical time point. The optimal deposition conditions proposed in this work are: deposition voltage 60 V, deposition time 20 min, additive 0.10 g·L− 1 Nafion and 0.10 mM NaOH.

Quantifying instant water cleaning efficiency using zinc oxide decorated complex 3D printed porous architectures

Industrialization harms the quality of water; therefore, cleaning and monitoring water sources are essential for sustainable human health and aquatic life. An increase in active surface area and porosity can result in quick and efficient cleaning activity. 3D printing can build porous architecture with controlled porosity and active surface area. Here, catalytically active ZnO nanosheets were grown on the surface of 3D printed architecture (Schwarzites and Weissmuller) with different porosity and surface area. The Weissmuller structure along with ZnO, has shown better catalytic performance due to its higher porosity (~69%) and high active surface area, compared to Schwarzites structure. Synergistic effect of adsorption and photodegradation has resulted in ~95% removal efficiency of mixed dye within 10 min by Weissmuller structure. The dye degradation efficiency was determined using colorimetric measurements with a regular smartphone for real-time quantitative investigation of dye removal efficiency. Most importantly, decorated 3D printed structures exhibit high structural stability without residuals (ZnO nanosheets) in water after performing the recycling experiment. Therefore, the decorated 3D printing structures and colorimetric detection method will offer a user-friendly versatile technique for analysis of removal efficiency of toxic components in different polluted water sources without using high-end sophisticated instruments and complicated procedures.

Effects of Recycled Fe2O3 Nanofiller on the Structural, Thermal, Mechanical, Dielectric, and Magnetic Properties of PTFE Matrix

The purpose of this study was to improve the dielectric, magnetic, and thermal properties of polytetrafluoroethylene (PTFE) composites using recycled Fe₂O₃ (rFe₂O₃) nanofiller. Hematite (Fe₂O₃) was recycled from mill scale waste and the particle size was reduced to 11.3 nm after 6 h of high-energy ball milling. Different compositions (5–25 wt %) of rFe₂O₃ nanoparticles were incorporated as a filler in the PTFE matrix through a hydraulic pressing and sintering method in order to fabricate rFe₂O₃–PTFE nanocomposites. The microstructure properties of rFe₂O₃ nanoparticles and the nanocomposites were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The thermal expansion coefficients (CTEs) of the PTFE matrix and nanocomposites were determined using a dilatometer apparatus. The complex permittivity and permeability were measured using rectangular waveguide connected to vector network analyzer (VNA) in the frequency range 8.2–12.4 GHz. The CTE of PTFE matrix decreased from 65.28×10−6/°C to 39.84×10−6/°C when the filler loading increased to 25 wt %. The real (ε′) and imaginary (ε″) parts of permittivity increased with the rFe₂O₃ loading and reached maximum values of 3.1 and 0.23 at 8 GHz when the filler loading was increased from 5 to 25 wt %. A maximum complex permeability of 1.1−j0.07 was also achieved by 25 wt % nanocomposite at 10 GHz.

Reusable Filters Augmented with Heating Microfibers for Antibacterial and Antiviral Sterilization

Numerous threats to human health and ecosystems on earth exist due to air pollution and the spread of fatal diseases. Airborne pollutants and particulate matter (PM) pose serious public health risks. In addition, the emergence and spread of bacterial and viral diseases constantly threaten public health and safety. Although various approaches have been implemented thus far to protect humans from air pollution and exposure to diseases, several challenges remain to be addressed. In this study, we developed a hybrid air filter consisting of filtration, heating, and thermal insulation layers. The air filtration layer can effectively capture airborne PM₁ particles (less than 1.0 μm in diameter). Furthermore, the heating layer enables the hybrid air filter to generate temperatures above 100 °C, and the insulation layer prevents the heat from being transferred to the other side (e.g., the human skin, if the hybrid air filter is used in a facemask). Since several bacteria and viruses are incapacitated under high temperatures, this hybrid air filter holds great promise for antibacterial and antiviral protection.

Collation Efficiency of Poly(Vinyl Alcohol) and Alginate Membranes with Iron-Based Magnetic Organic/Inorganic Fillers in Pervaporative Dehydration of Ethanol

Hybrid poly(vinyl alcohol) and alginate membranes were investigated in the process of ethanol dehydration by pervaporation. As a filler, three types of particles containing iron element, i.e., hematite, magnetite, and iron(III) acetyloacetonate were used. The parameters describing transport properties and effectiveness of investigated membranes were evaluated. Additionally, the physico-chemical properties of the resulting membranes were studied. The influence of polymer matrix, choice of iron particles and their content in terms of effectiveness of membranes in the process of ethanol dehydration were considered. The results showed that hybrid alginate membranes were characterized by a better separation factor, while poly(vinyl alcohol) membranes by a better flux. The best parameters were obtained for membranes filled with 7 wt% of iron(III) acetyloacetonate. The separation factor and pervaporative separation index were equal to 19.69 and 15,998 g⋅m⁻²⋅h⁻¹ for alginate membrane and 11.75 and 14,878 g⋅m⁻²⋅h⁻¹ for poly(vinyl alcohol) membrane, respectively.

Preparation of a New Biocomposite Designed for Cartilage Grafting with Antibiofilm Activity

New polymer–inorganic composites with antibiofilm features based on the granulated poly(tetrafluoroethylene) (PTFE) and apatite materials were obtained using a standard hydraulic press. The study was performed in hydroxy- and fluorapatites doped with different amounts of silver ions and followed by heat treatment at 600 °C. The structural, morphological, and physicochemical properties were determined by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS), and transition electron microscopy (TEM). The antibacterial properties of the obtained materials were evaluated against Gram-negative pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli as well as against Gram-positive bacteria Staphylococcus epidermidis. The cytotoxicity assessment was carried out on the red blood cells (RBC) as a cell model for in vitro study. Moreover, the biofilm formation on the biocomposite surface was studied using confocal laser scanning microscopy (CLSM).

Investigation of Perovskite Oxide SrCo0.8 Cu0.1 Nb0.1 O3-δ as a Cathode Material for Room Temperature Direct Ammonia Fuel Cells

Single-phase perovskite oxide SrCo0.8 Cu0.1 Nb0.1 O3-δ was synthesized using a Pechini method. X-ray diffraction (XRD) analysis indicated a cubic structure with a=3.8806(7) Å. The oxide material was combined with active carbon, forming a composite electrode to be used as the cathode in a room temperature ammonia fuel cell based on an anion membrane electrolyte and NiCu/C anode. An open circuit voltage (OCV) of 0.19 V was observed with dilute 0.02 m (340 ppm) ammonia solution as the fuel. The power density and OCV were improved upon the addition of 1 m NaOH to the fuel, suggesting that the addition of NaOH, which could be achieved through the introduction of alkaline waste to the fuel stream, could improve performance when wastewater is used as the fuel. It was found that the SrCo0.8 Cu0.1 Nb0.1 O3-δ cathode was converted from irregular shape into shuttle-shape during the fuel cell measurements. As the key catalysts for electrode materials for this fuel cell are all inexpensive, after further development, this could be a promising technology for removal of ammonia from wastewater.

Formation and characterization of polytetrafluoroethylene nanofiber membranes for high-efficiency fine particulate filtration

Polytetrafluoroethylene (PTFE) porous membranes are widely used for high-temperature filtration. The polytetrafluoroethylene nanofiber membranes for fine particulate filtration were prepared by sintering the precursor electrospun polytetrafluoroethylene/polyvinyl/boric acid alcohol composite membranes. The effects of PTFE/PVA mass ratio and sintering temperature on the morphology and properties of the prepared membranes were investigated to obtain the PTFE nanofibers with different diameters, and the film has been characterized by SEM, TG, XRD, FT-IR, and EDS, and the mechanical and hydrophobic properties of the membranes were also investigated. The PTFE nanofiber membranes after sintering had nanofiber and nanowire structures. Moreover, the membranes were tested in air filtration. The filtration efficiency and pressure drop were tested to evaluate the membrane permeability and separation properties. The results showed a high filtration efficiency (98%) and a low pressure drop (90 Pa) for 300 nm sodium chloride aerosol particles at a 30 L min-1 airflow velocity and the hydrophobic membranes showed durable self-cleaning properties, which suggested that the PTFE nanofiber membranes were a promising candidate for high temperature filtration applications.