PTFE Surface Research Articles

Bidirectional Elastic PTFE Small Diameter Artificial Blood Vessel Grafts and Surface Antithrombotic Functionalized Construction.

Expanded polytetrafluoroethylene (ePTFE) failed to achieve clinical application in the field of small-diameter blood vessels due to its lack of elasticity in the circumferential direction and high stiffness. Excellent multidirectional elasticity and dynamic compliance matching with natural blood vessels are important means to solve the problem of acute thrombosis and poor long-term patency. Herein, novel PTFE spinning blood vessels were prepared by the PTFE emulsion electrospinning process, which not only presented good bidirectional elasticity but also promoted the adhesion and proliferation of endothelial cells and induced the contractile expression of SMCs. And, a PTFE-shish and aminated polycaprolactone (PCL)-kebab structure has been developed that converted the chemically inert PTFE surface into a drug-loading platform for the multifunctionalization of PTFE vascular grafts. It provides novel preparation methods for the application of new bidirectional elastic small-diameter artificial blood vessels and their surface functionalization construction.

Hydrocarbon‐Based Ionomer/PTFE‐Reinforced Composite Membrane Through Multibar Coating Technique for Durable Fuel Cells

AbstractFor cost reduction and environmental‐friendly manufacturing, it is highly demanded to replace the current perfluorinated sulfonic acid‐based membrane in polymer electrolyte membrane fuel cells (PEMFCs) with inexpensive and readily available hydrocarbon‐based (HC) membranes. However, HC membranes suffer from profound dimensional changes caused by swelling and shrinking during operation, especially in automotive applications. These changes lead to severe mechanical degradation and shorten the service life of PEMFC. Herein, a multibar coating system is developed to manufacture HC/polytetrafluoroethylene (PTFE) composite membrane. This system facilitates capillary‐rise infiltration with the aid of an optimal amount of residual alcohol solvent on the PTFE. To address compatibility issues between PTFE and HC‐ionomer solutions, the effects of residual alcohol solvent on tuning the PTFE surface are investigated by controlling systemic parameters and performing diverse mechanical, optical, and electrochemical measurements. Based on its enhanced mechanical toughness (≈30.04%) and superior impregnation properties, the constructed HC/PTFE composite membrane exhibited more than seven‐fold improvement in mechanical durability under repeated accelerated wet–dry conditions compared with an unsupported pristine HC membrane while also mitigating performance loss (≈5.84%).

Quantitative Analysis of the Dispersion Interaction of Liquids with the Surface of Gamma-Irradiated PTFE

Quantitative Analysis of the Dispersion Interaction of Liquids with the Surface of Gamma-Irradiated PTFE

Development of Superhydrophobic PTFE Surface Using Oxygen Plasma Processing

Development of Superhydrophobic PTFE Surface Using Oxygen Plasma Processing

Functionalization of PTFE substrates with quaternary ammonium groups – An approach towards anion conducting properties

Hydrogen produced by electrolysis using renewable energy sources offers a zero-emission alternative to fossil-based sources providing high efficiencies in all energy sectors. Anion Exchange Membrane Water Electrolysis (AEM-WE) combines the advantages of the established technologies, alkaline (AEL) and proton exchange membrane (PEM) water electrolysis. However, AEM-WE still requires optimization, especially with regard to the membrane, catalysts and electrode structure. In this contribution we focus on the improvement of PTFE-based binders for AEM-WE membranes, which provide high chemical stability but lack the required ion conductivity. Thus, the functionalization of PTFE towards quaternary ammonium moieties (QAS) was investigated employing two approaches: (i) NH3-plasma treatment and (ii) O2-plasma with subsequent coupling of aminosilanes. Finally, the surface coupled amino groups were converted into QAS via alkylation with iodomethane (CH3-I), introducing ion conductivity. Successful functionalization was proved by X-ray photoelectron spectroscopy (XPS), displaying changes in the surface composition of PTFE surfaces such as the introduction of amino groups at the expense of fluorine, and the increase in surface carbon content upon alkylation. Furthermore, contact angle measurements revealed increased wettability with water due to the introduction of the polar surface functionalities, while zeta potential measurements confirmed the increase of positive surface charges along the modification processes.

The effect of ions on liquid-solid interface investigated by charge sensitive direct current droplet-based electricity generator

The contact electrification (CE) between DI water and SiO2 or fluorinated polymer has been proven to be mainly due to electron transfer, which is significantly influenced by ions in solution. However, how these ions in water affect the charge transfer at the liquid-solid (L-S) interface is still unresolved, especially for the already charged friction layer. Here, a direct current droplet-based electricity generator (DC-DEG) which is sensitive to the change of charge transfer at the L-S interface is adopted to detect the effects of ions in the neutral salt solution on the charged PTFE surface. The distribution of ions on the charged L-S interface (the change of electric potential on the solid surface) and its effects on the output of DC-DEGs have been studied. The results indicate that the charge transfer of droplets and then the output of DC-DEGs are closely related to the concentrations of salt solutions. Anions can enhance the surface potential of PTFE due to their adsorptions on PFTE while cations can reduce it due to their screen effect. At low ionic concentrations, the surface potential enhancement caused by anion adsorption is larger than that surface potential reduction caused by screen effect from cations. At high ionic concentrations, the electrostatic screen effect of cations increases a lot to weaken the surface potential and reducing the charge separation of droplets induced by electrostatic induction (EI). This work explains the redistribution process of ions at the L-S interface and also provides a clever solution for improving the electrical output performance of DEGs.

Multi-length Scale Approach to Investigate Cleaning of Food-Derived Deposits Adhered to Hard Surfaces: Mixtures of Starch, Whey Protein, and Lard

Fouling, the accumulation of undesirable material on manufacturing equipment surfaces, poses a pervasive challenge in industrial processes. In the food industry, the complex interactions among these compounds can give rise to stubborn deposits that deviate from conventional cleaning protocols. In this work, the forces and removal mechanisms of model fouling agents composed of mixtures of starch, whey protein, and lard deposited on solid surfaces of relevant industrial interest (i.e. stainless steel, aluminium, and PTFE) are investigated using a multi-length scale approach, involving milli-manipulation and a lab-simulated Clean-In-Place (CIP) system. The forces involved in the removal process, the types of failure observed when the deposits are subjected to shear stress (adhesive, mixed, or cohesive), and the performance of the CIP system are systematically analysed as a function of the cleaning treatments applied. For stainless steel surfaces, alkaline treatment seems to facilitate the cleaning of lard and starch deposits, while the whey foulant removal tends to be more effective using hot water under the conditions tested. Hot water is effective for stainless steel and PTFE surfaces, reducing the mechanical shear stress required, while the alkaline treatment demonstrated superior efficacy for aluminium surfaces. These findings emphasise the importance of customising cleaning protocols for CIP optimisation.

Evaluating Cold Atmospheric Plasma for Endoscope Decontamination: Feasibility and Impact Analysis on PTFE Surfaces

Evaluating Cold Atmospheric Plasma for Endoscope Decontamination: Feasibility and Impact Analysis on PTFE Surfaces

Assessing the Mechanical-to-Electrical Energy Conversion Process of a Droplet Sliding on the Poly(tetrafluoroethylene) Surface.

Utilizing moving droplets to generate electricity has garnered significant attention due to its high output voltage and power. However, the understanding of energy dissipation and conversion processes during droplet movement remains limited, hindering the development of effective ways to further enhance the device's performance. In this study, we developed a method to simultaneously evaluate the input mechanical energy and output electrical energy while droplets slide on a poly(tetrafluoroethylene) (PTFE) surface to assess the energy conversion process. The influences of ion concentration, droplet volume, and contact area with PTFE on the energy conversion efficiency were investigated, suggesting optimized parameters. Moreover, by introduction of an asymmetric electric field on the PTFE surface, the input mechanical energy can be significantly reduced. In combination with the enhanced electrical output originating from improved surface charge density, the energy conversion efficiency is improved by an order of magnitude from 0.61 to 9.08%. These results shed light on strategies to improve device performance based on moving droplets.

Development of a Carbon Nanotube-Enhanced FAS Bilayer Amphiphobic Coating for Biological Fluids.

This study reports the development of a novel amphiphobic coating. The coating is a bilayer arrangement, where carbon nanotubes (CNTs) form the underlayer and fluorinated alkyl-silane (FAS) forms the overlayer, resulting in the development of highly amphiphobic coatings suitable for a wide range of substrates. The effectiveness of these coatings is demonstrated through enhanced contact angles for water and artificial blood plasma fluid on glass, stainless steel, and porous PTFE. The coatings were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) measurements. The water contact angles achieved with the bilayer coating were 106 ± 2°, 116 ± 2°, and 141 ± 2° for glass, stainless steel, and PTFE, respectively, confirming the hydrophobic nature of the coating. Additionally, the coating displayed high repellency for blood plasma, exhibiting contact angles of 102 ± 2°, 112 ± 2°, and 134 ± 2° on coated glass, stainless steel, and PTFE surfaces, respectively. The presence of the CNT underlayer improved plasma contact angles by 29%, 21.7%, and 16.5% for the respective surfaces. The presence of the CNT layer improved surface roughness significantly, and the average roughness of the bilayer coating on glass, stainless steel, and PTFE was measured to be 488 nm, 301 nm, and 274 nm, respectively. Mechanistically, the CNT underlayer contributed to the surface roughness, while the FAS layer provided high amphiphobicity. The maximum effect was observed on modified glass, followed by stainless steel and PTFE surfaces. These findings highlight the promising potential of this coating method across diverse applications, particularly in the biomedical industry, where it can help mitigate complications associated with device-fluid interactions.

A New Single‐Electrode Generator for Water Droplet Energy Harvesting with A 3 mA Current Output

AbstractTriboelectric nanogenerators (TENGs) based on water droplets can harvest water kinetic energy using triboelectrification and electrostatic induction mechanisms. However, the development of traditional liquid–solid TENGs (L–S TENGs) is severely limited due to their low‐performance output and high device encapsulation requirements for preparation technology. In this work, a single‐electrode mode droplet‐based TENG (D‐TENG) is devised to effectively harvest water kinetic energy by optimizing the interface contact behavior of droplets, increasing the short‐circuit current (ISC) of one drop of water from microamperes to milliamperes levels. In the D‐TENG configuration, the electrode is positioned above the dielectric rather than at the bottom, allowing efficient utilization of generated friction charges and reducing the dissipation of these charges, thereby enhancing the output performance of the TENG. The influencing factors and operational mechanisms of D‐TENG are studied to obtain optimized working conditions to improve its output performance. Under optimal conditions, the D‐TENG can saturate the charge of the PTFE surface with only 8 droplets, achieving an ISC of up to 3.51 mA and an output voltage (VO) of 298.27 V. This work provides a convenient method for efficiently harvesting water kinetic energy based on interfacial behavior control.

Multi‐featured epoxy composites filled with surface‐modified PTFE powders treated by Na‐naphthalenide system

AbstractThis study aimed to produce new multi‐featured epoxy composites that are advanced in terms of mechanical properties, wear and impact resistance, and glass transition and heat deflection temperatures. Epoxy composites filled with chemically surface‐treated poly (tetrafluoroethylene) (PTFE) powders at various ratios were prepared to obtain these improved properties. The chemical treatment was carried out via a Na‐naphthalenide system. After this treatment, the x‐ray photoelectron spectroscopy results presented the existence of functional groups such as OH, carbonyl groups, and CC unsaturation points on the surface of the PTFE powders. On the PTFE surfaces, while the atomic ratios of carbon and oxygen were substantially increased, the fluorine ratio presented a significant decrease after the chemical treatment. However, the wear rates of the novel composites were highly advanced despite this large decrease in the fluorine ratio on the surface of the PTFE powders. Moreover, functional groups such as OH, carbonyl groups, and CC unsaturation points and spongelike or network structures on the PTFE surfaces provided the opportunity to obtain strong adhesion and interfacial bonding between the surface‐modified PTFE powders and the matrix. Strength and modulus values showed substantial enhancement besides the IZOD impact resistance. All glass transition and heat deflection temperatures were also substantially improved.

Exploring the energy harvest of droplet flow over inducted film for the rainy-shiny solar panel application

An equivalent electrical circuit (EEC) based on transient pseudo-capacitive and electrostatic induction is established to understand the operating mechanism using voltage-time curve decomposition. All relative parameters including top electrode dimension and the instantaneous droplet area variation are used to demonstrate our droplet-base electricity generation (DEG) mechanism and illustrate the principle of the reverse voltage. Moreover, the Debye length concept is introduced to explain charge density at the interface between ionic droplet and the PTFE surface by various ion concentrations and valent number solutions. This work provides insightful and valuable perspective to explain the exponential decay of output voltage by instantaneous droplet area variation during leaving away from the PTFE surface. Moreover, the multi-functions of fluorinated ethylene propylene film coating on the solar panel by correct circuit design can improve 30% which is novel concept at rainy days alternated with dry ones.

Characterization of corona discharge treatment on PTFE surface for TENG applications

As for practical application of triboelectric nanogenerators (TENGs), corona discharge treatment (CDT) is often utilized further to enhance its power outputs by injecting charges. We report compositional analysis and corresponding triboelectric outputs of Poly(1,1,2,2-tetrafluoroethylene) (PTFE) based TENGs. PTFE and Al based TENGs with various PTFE film thickness are fabricated and their performances are measured with different CDT applied bias. XPS depth profile analysis reveals the relation of triboelectric outputs and depth of oxygen ions. Our discovery may give insight in the future development of high performance TENGs using CDT.

Improved cryogenic frictional properties of thrust ball bearings in liquid nitrogen through PTFE cages and dimple-type textures

To improve the working performance of thrust ball bearings in liquid nitrogen, self-lubricating PTFE cages and surface-textured raceways are introduced into the bearings. Circular dimple-type textures are generated by the laser process. The frictional characteristics of a full-steel bearing and a bearing with a PTFE cage are tested and compared at first on a self-developed cryogenic rotating-type tribometer. The micrographs of the worn surfaces are analyzed together. Then, the surface-textured raceways are employed into the bearings with PTFE cages. The influence of different circular dimple diameters of the textures on frictional performance is analyzed. Finally, an influence mechanism of the PTFE cage and surface textures on the cryogenic frictional performance of thrust ball bearings is proposed based on the experimental results.

Liquid-gas phase transition enables microbial electrolysis cell to treat organic pollution and synchronously remediate nitrate-contaminated groundwater via hydrogenotrophic denitrification

Groundwater denitrification is challenged by a lack of electron donors and usually requires additional energy input or chemical agents. MEC can convert organic pollution into clean electron donor (hydrogen) through a gas-liquid phase transition. In this study, the MEC was combined with permeable bio-reactive barrier (PRB) as a hybrid system to achieved simultaneous organic waste removal, hydrogen production and groundwater remadition via long-distance hydrogenotrophic denitrification by biogas. The semi-hydrophobic PTFE-coated granular activated carbons (GAC) and hydrophilic GAC were filled as two kinds of biocarriers in PRBs, in which the hydrophobic PTFE surface coating improved hydrogen utilization. The PTFE-coated GAC maked the denitrification performance of PRB insensitive to hydrogen partial pressure within the tested range of 0.01–0.04 MPa and achieved effluent nitrate concentration of <20 mg L−1 within 12 h (The Water Quality Standard for Drinking Water Sources in China). The gas production in MECs was actively pumped to PRBs and spontaneously achieve negative pressure on the MEC side and positive pressure on the PRB side. The actively pumping of biogas induced negative pressure in MEC and positive pressure in PRB. The negative pressure improved current density by 18.6 ± 0.7% in MECs and the MEC-PRB hybrid system achieved a nitrate removal of 85.0 ± 0.8% in actual groundwater with an effluent concentration of 15.0 ± 0.8 mg L−1 at 72 h. This work demonstrated the feasibility of matching MEC and PRB as a novel hybrid system for organic pollution degradation and effective nitrogen removal in electron-donor-lacking groundwater.

Effects of plasma treatments on the surface wettability properties of PTFE polymeric films

A cold cathode plasma source is constructed for modifying PTFE surface characteristics. The source was easily built, had a consistent plasma discharge medium and acceleration system. A cylindrical Langmuir probe is also used to evaluate plasma parameters like density, temperature or even plasma potential. This probe is designed to be moveable so that it may approach any desired position in the plasma volume. The influences of nitrogen pressure and probe-cathode gap on plasma parameters were investigated. The electron temperature [Formula: see text] fluctuated from [Formula: see text] to [Formula: see text][Formula: see text]eV as the pressure rises from 0.2 to 0.4[Formula: see text]mbar. Further, by increasing the cathode-probe gap from 0.4 to 2[Formula: see text]cm, the electron densities increased from [Formula: see text][Formula: see text]cm[Formula: see text] to [Formula: see text][Formula: see text]cm[Formula: see text]. Furthermore, the contact angles, work of adhesion and surface free-energy of pristine as well as irradiated PTFE films, were estimated. The results demonstrated that by extending the plasma exposure duration from 0 to 12[Formula: see text]min, the water contact angle is lowered from 82.2∘ to 30.5∘. At these conditions, the work of adhesion is raised from 81.9 to 134.1[Formula: see text]mJ/m2, as the surface free energy is increased from 29.8 to 71.8[Formula: see text]mJ/m2.

Leaves of Cannabis sativa and their trichomes studied by DESI and MALDI mass spectrometry imaging for their contents of cannabinoids and flavonoids.

In recent years, industrial production of Cannabis sativa has increased due to increased demand of medicinal products based on the plant. In these medicinal products, it is mainly the contents of cannabinoids like THCA and CBDA which are of interest, but also the flavonoids of C. sativa have pharmaceutical interest. The primary aim is to study the distribution of the different cannabinoids in leaves of C. sativa and specifically to which extent they are located on the trichomes found on the surface of C. sativa leaves. Desorption electrospray ionization (DESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) provide non-targeted imaging of numerous compounds in the same experiment. Therefore, the distribution of flavonoids is also mapped in the same experiments. Fan leaves from C. sativa were imaged in the lateral dimension using direct DESI-MSI as well as indirect DESI-MSI via a porous PTFE surface using pixel sizes of 150-200 μm. For cross sections of sugar leaves, MALDI-MSI was performed at 20 μm pixel size. From indirect DESI-MSI experiments, a connection was made between the cannabinoid CBGA and capitate-stalked trichomes. Other cannabinoids like THCA/CBDA (isomers, which are not resolved in an MSI experiment) were also detected in the capitate-stalked trichomes, but in addition to this also in the small glandular trichomes. MALDI-MSI experiments on cross sections of sugar leaves confirmed that the cannabinoids were not an integral part of the leaf tissue itself, but originated from the trichomes on the surface of the leaf. The study provides visual evidence that the cannabinoids are produced and accumulated in the trichomes of C. sativa leaves.

Solution casting of cellulose acetate films: influence of surface substrate and humidity on wettability, morphology and optical properties

Variations on the processing conditions of conventional methods for polymeric film preparation may allow tuning certain properties. In this work, different casting surfaces and humidity are presented as variables to consider for cellulose acetate (CA) film preparation using conventional solution casting method. Specifically, borosilicate glass, soda-lime glass and Teflon (PTFE) dishes have been used for casting and their influence on various properties on CA films assessed. The surfaces of glass dishes are smooth, while PTFE surface has a pattern constituted by concentric channels of micro dimensions (as seen by optical microscope), which is adopted by cast films upon drying. The resulting patterned films are translucent while films produced using smooth surfaces are transparent. The effect of the environment humidity (35%, 55% and 75% RH) in the properties of the CA films during the evaporation of solvent from solution has been evaluated. Higher humidity produces smoother surfaces and increased crystallinity as shown by XRD and DSC; however, the wettability of the films does not seem to be influenced by this variable. Due to the specific morphology of the patterned films, changes in material opacity upon wetting are detected, from translucent to transparent, while the removal of water from the surface restores the translucency. This micropatterning effect that causes different visual appearance of the material can find use as a humidity sensor in food packaging applications.

Fecalphobic oil-coated femtosecond-laser-processed PTFE surface

Water, sanitation, and hygiene (WASH) investments have become crucial not only to prevent and recover from pandemics and local outbreaks but also to prevent the spread of antimicrobial resistance. However, over 2 billion people worldwide still have access to even poor sanitation, which devastates public health and social and economic development. In addition, inadequate sanitation can cause contamination to drinking water sources where exist insufficient protection, exacerbating clean water scarcity. Here, we introduce a femtosecond laser processing technology combined with silicone oil coating to prepare a slippery surface that can repel feces, named the fecalphobic surface. Compared to a flat surface, the fecalphobic surface requires only a quarter amount of water (on average) or even no water to remove sticky viscoelastic solid-like fecal simulants. Besides, various liquids will slide off this surface. Moreover, the simulant slides off the fecalphobic surface much faster than off an untreated one, approximately 3–26 times faster depending on their weight. The mechanism of the fast sliding of fecal simulants is explained. Moreover, the fecalphobic surface is installed on a latrine prototype that integrates an automatic trap door and a urine-feces separator for improved sanitation solution.