Polytetrafluoroethylene Thin Films Research Articles

Elucidating the modified performance of high nuclearity of Cu nanostructures-PTFE thin film

The aim of this study is to attain an extensive insight on the performance mechanism that is associated with the formation of Cu nanostructures- polytetrafluoroethylene (PTFE) thin film. The work presented Cu nanostructures synthesised via microwave-assisted method at different Cu precursor concentrations to observe the influence of different average particle diameter distribution, {d}_{m} of Cu nanostructures on the fabricated Cu nano thin film. The thin films of Cu nanostructures with a layer of PTFE were fabricated using the Meyer rod coating method. Evaluating the effect of Cu nanostructures at different {d}_{m} with overcoated PTFE layer showed that the resistance of fabricated thin film coated with PTFE is not significantly different from that of the uncoated thin film. The results implicate the influence of the PTFE layer towards the output performance, which can maintain a stable and constant resistance over time without affecting the original properties of pure Cu nanostructures, although some of the Cu nanostructures seep into the layer of PTFE. The novelty of this study lies in the effect of the intrinsic interaction between the layer of Cu nanostructure and PTFE, which modulate the performance, especially in photovoltaic cell application.

Fabrication and the film-forming mechanism of thin polytetrafluoroethylene films with enhanced dielectric and mechanical properties

Polytetrafluoroethylene (PTFE) films with outstanding dielectric properties are widely used in the next-generation integrated circuit devices. However, how to prepare the ultra-thin PTFE films with high-performance is still a challenge. In this paper, the PTFE emulsion casting-drying-sintering method was used to prepare thin PTFE films (with the thickness around 20 μm), and the film formation mechanism was investigated. It was firstly detected that the micro-cracks, generated by the solid-liquid-gas interface forces during the horizontal and vertical directional drying of the PTFE emulsion, are the key factors for the performance of PTFE films. After eliminating these micro-cracks through improved drying and sintering processes, the tensile strength of the PTFE films was increased by 3 times. Moreover, the dielectric constant and dielectric loss declined to 2.0 and 0.00065 at 10 GHz, respectively. This work provides an effective strategy to realize the fabrication of high-performance PTFE films without the addition of any additives.

Comparative wettability study of bulk and thin film of polytetrafluoroethylene after low energy ion irradiation

A comparative wettability study was carried out on bulk polytetrafluoroethylene (PTFE) and physical vapor deposited PTFE-like thin films using low-energy Argon ion beam irradiation. Both bulk PTFE and PTFE-like thin film surfaces were irradiated with the beam energy of 300 and 800 eV for 5 min. The angle of incidence of the ion beam was varied from 0° to 70° with respect to the surface normal. Ion beam irradiation produced the tilted sharp-edged microstructures on PTFE sheets elongated in the direction of the beam. After irradiation with 800 eV at 20°, the bulk PTFE sheet became superhydrophobic, the water contact angle increased from 105° to 157°, and again decreased to 132° after irradiation at 70° Whereas nanoripple-like patterns formed on PTFE-like thin films after ion beam irradiation. The maximum wavelength of such ripples was found to be 212 nm for an 800 eV irradiated surface at an angle of 50° Beyond this angle, a clear transition from ripple to facet-like patterns was observed. The contact angles of the irradiated thin film were found to be varying from 105° to 112° up to 30° irradiation and again decreased to 83° after irradiation at 70° PTFE thin film showed strong anisotropic wettability behavior with a variation of 12° of contact angle values perpendicular to the ion beam direction, and water droplets did not roll off from the surface like in the case of bulk PTFE. X-ray photoelectron spectroscopy revealed that the bulk PTFE had C−C, and CF2 bonding on the surface, whereas PTFE thin films formed additional CF, CF‒CFn, and CF3 bonding, which was not observed in the bulk PTFE. After irradiation, additional CF-CFn and CF3 bonding in bulk PTFE were observed. However, in the case of thin films, ion irradiation causes severe chain scission, crosslinking, and defluorination of the surface.

Autonomous Self-healable Scratch-free Bilayer Anti-corrosion Film

Thin hydrophobic polymer film, which physically prevents an approach of corrosive media, has been widely used as an anti-corrosion coating for metals. Though polymer film effectively passivates surface of metal, it loses its anti-corrosion property once the film is peeled off by physical damage, such as scratches. Corrosion can be propagated from the exposed area even if the area is small. Therefore, for long-term anti-corrosion, the film should be seamless and completely cover the entire metal surface without scratches. In this study, we introduce an autonomously self-healable hydrophobic coating with superior anti-corrosion property by a combination of self-healable/fluorinated polymers. Schiff-base linkages based polydimethylsiloxane (SC-PDMS) is used as a primary protection layer against corrosive media. The SC-PDMS matrix with the dynamic imine bonds allows scratch-free metal protection layer by reproducible damage healing property. In addition, we applied polytetrafluoroethylene (PTFE) thin film at the surface of the SC-PDMS, which suppresses the reaction of imine bond with water and helps to maintain long-term anti-corrosion property. Eventually, this simple coating of bilayer structure with SC-PDMS and PTFE shows an effective scratch-free corrosive resistance, providing a new way of long-term use of metals.

A Study of the Relationship between the Rate of Return Strain of Polytetrafluoroethylene on Time, Mechanical Stress and Dose of Electron Irradiation

The paper is devoted to the study of the influence of factors on the rate of return deformation of polytetrafluoroethylene. The dependence of the rate of return strain (ε'r) on time (t), the dose of electron irradiation (D) and mechanical stress (σ) in thin films of polytetrafluoroethylene has been experimentally investigated. Significant variations of ε'r have been found dependingon on t, D and σ. A decrease in the rate of return deformation during irradiation of the material is associated with the frictional properties between macromolecules and a change in the structure, which leads to a weaker straightening of the polymer and their poor sliding. The resulting curves for both unirradiated and irradiated material are satisfactorily described in the exponential and linear models. For dependencies ε'r on D, these are decreasing functions, and for ε'r on σ, these are increasing functions.

Conformal Passivation of Self-Cleanable, Flexible, and Transparent Polytetrafluoroethylene Thin Films on Two-Dimensional MXene and Three-Dimensional Ag Nanowire Composite Electrodes

Despite the excellent performance of MXene–Ag nanowire (MA) composite transparent conductive electrodes (TCEs), they rapidly and severely degrade in ambient and humid environments. To address this critical issue, we developed conformal polytetrafluoroethylene (PTFE) passivation thin films prepared using magnetron sputtering at room temperature. Compared to the PTFE passivated electrode, the nonpassivated bare MA-composite electrode exhibited a considerably increased sheet resistance, and the electrode flexibility and electromagnetic interference (EMI) shielding efficiency (SE) degraded rapidly over time because the moisture and impurities severely oxidized the MXene layer in the harsh testing environment. However, the MA-composite electrode with PTFE passivation shows constant sheet resistance, transmittance, flexibility, and EMI SE, even after the 85 °C–85% relative humidity (RH) test. Compared to the nonpassivated MA-electrode-based thin film heaters (TFHs), the PTFE-passivated MA-composite electrode-based TFHs exhibited improved stability and reliability, indicating that the sputtered PTFE film effectively prevented the moisture and impurity penetration of the MA-composite electrodes.

Strain‐Invariant, Highly Water Stable All‐Organic Soft Conductors Based on Ultralight Multi‐Layered Foam‐Like Framework Structures

AbstractSoft and flexible conductors are essential for the development of soft robots, wearable electronics, electronic tissue, and implants. However, conventional soft conductors are inherently characterized by a large change in conductance upon mechanical deformation or under alternating environmental conditions, e.g., humidity, drastically limiting their application potential. This work demonstrates a novel concept for the development of strain‐invariant, highly elastic and highly water stable all‐organic soft conductors, overcoming the limitations of previous strain‐invariant soft conductors. For the first time, thin film deposition technologies are combined in a three‐dimensional fashion, resulting in micro‐ and nano‐engineered, multi‐layered (<50 nm), ultra‐lightweight (< 15 mg cm−3) foam‐like framework structures based on Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) and Polytetrafluoroethylene (PTFE), characterized by a highly strain‐invariant conductivity (≈184 S/m) between 80% compressive and 25% tensile strain. Both the initial electrical and mechanical properties are retained during long‐term cycling, even after 2000 cycles at 50% compression. Furthermore, the PTFE thin film renders the framework structure highly hydrophobic, resulting in stable electrical properties, even when immersed in water for a month. Such innovative multi‐scaled and multi‐layered functional materials are of interest for a broad range of applications in soft electronics, energy storage and conversion, sensing, water and air purification, as well as biomedicine.

Optical and Mechanical Properties of Thin PTFE Films, Deposited from a Gas Phase

AbstractThin polytetrafluoroethylene (PTFE) films are produced by deposition from a gas phase by two methods: electron‐enhanced vacuum deposition (EVD) and EVD + low‐temperature plasma (LTP). Structure, morphology, and composition of the films are studied by IR spectroscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy. They are close to the structure of bulk PTFE. The roughness of the films’ surface is changed with gas pressure and LTP power variations. Films are transparent from UV to near‐infrared regions. Refractive and extinction indices and their anisotropy are measured by spectral ellipsometry. They are tuned by variations of deposition conditions. Hardness and Young modulus of the films are increased if EVD + low power LTP is used for film deposition. Use of EVD + LTP also increases thermal stability of the films. Contact angle of the films corresponds to the bulk PTFE. The PTFE molecules oriented are preferentially in perpendicular direction to the substrate surface.

Highly Transparent, Flexible, and Hydrophobic Polytetrafluoroethylene Thin Film Passivation for ITO/AgPdCu/ITO Multilayer Electrodes (Adv. Mater. Interfaces 11/2022)

PTFE Thin Film Passivation for ITO-AgPdCu-ITO (IAI) Electrodes In article number 2101823, Seong-Won Kim, Chaeyoung Kang, and Han-Ki Kim report a transparent and flexible polytetrafluoroethylene (PTFE) thin film passivation for flexible ITO-AgPdCu-ITO (IAI) electrodes to prevent severe degradation and maintain the reliable performance of the IAI-based flexible and wearable electronics.

Highly Transparent, Flexible, and Hydrophobic Polytetrafluoroethylene Thin Film Passivation for ITO/AgPdCu/ITO Multilayer Electrodes

AbstractTransparent and flexible polytetrafluoroethylene (PTFE) thin film passivation for ITO/AgPdCu (APC)/ITO (IAI) electrodes is developed to prevent severe degradation and maintain the reliable performance of the flexible IAI electrodes. Also, oxygen ion beam treatment (IBT) on the surface of the IAI electrode improves the adhesion between the top ITO and PTFE passivation layer, as well as the performance of the passivation layer. The IAI electrode with PTFE passivation exhibits constant sheet resistance, transmittance, and flexibility, even after the 85 °C and 85% RH test. However, the bare IAI electrode shows a significant increase in sheet resistance and a decrease in transmittance and flexibility, owing to the incorporation of moisture and impurities into the IAI layer, and agglomeration of the APC layer. To demonstrate the feasibility of PTFE passivation, the performance of flexible and transparent thin film heaters (TFHs) with the bare IAI and PTEF/IAI samples are compared. The better stability and reliability of the PTFE/IAI‐based TFHs than the bare IAI‐based TFHs indicate that the PTFE film effectively prevents the introduction of moisture and impurities. The performance of the TFH with PTFE/IAI electrode implies that sputtered PTFE film is a promising transparent and flexible thin film passivation for high‐quality oxide‐metal‐oxide multilayer electrodes.

Variations of morphology of fluoropolymer thin films versus deposition conditions

Fluoropolymers (FP) are materials with a combination of excellent physical and chemical properties which make them useful in various industries. Thin films of these almost insoluble polymers were deposited with decomposition-evaporation of bulk FP in a vacuum. The pretreatment of the evaporated FP, the pressure of the emitted gas, the activation with accelerated electrons, the additional radio frequency (RF) plasma and the external magnetic field had complex effects on the morphology and relief of polytetrafluoroethylene (PTFE) films. Thin PTFE films with a roughness from 2 to 100 nm were produced. A PTFE film grown in a magnetic filed had nanoworms on its surface. The hardness of PTFE films was increased using low power RF plasma during deposition. The hardness of polychlorothrifluoroethylene (PCTFE) thin film was significantly smaller, whilst the relief of PCTFE films was rougher than that of PTFE films. A conformal PTFE coating was deposited on a nanostructured plastic surface using PTFE evaporation with electron activation and low power RF plasma.

Surface modification of polytetrafluoroethylene thin films by non-coherent UV light and water treatment for electrowetting applications

HypothesisThe electrowetting on dielectric or EWOD phenomenon is used in a wide range of applications, such as Liquid Lenses, Lab-on-Chip devices, or EWOD displays, among others. Its chemical resistance, electrical stability, ease of application, and low cost make polytetrafluoroethylene (PTFE) the preferred hydrophobic dielectric layer for such applications. However, the hydrophobic behaviour represents a challenge for spin coating other layers over its surface. As a consequence, several techniques are implemented to modify the surface of PTFE. These methods are complex, time-consuming, and produce morphology changes over the surface that are difficult and sometimes impossible to recover. In this work, we propose a new surface modification method that is based on a non-coherent UV light exposition method and a specific water treatment, that lead to a change from hydrophobic to hydrophilic, and a perfect recovery from hydrophilic to hydrophobic behaviour. ExperimentsIn this work, the fabrication of the hydrophobic layer treatment starts with the creation of a thin layer of alumina (Al2O3) over a glass substrate using an atomic layer deposition technique (ALD). A mixture of 10:1 FC40 solvent and Teflon Dupont AF1600 was coated over the alumina layer. The Teflon film was exposed to UV light produced by a low-pressure mercury (Hg) lamp for a period that ranges from 3−6 min. The results were analysed by scanning electron microscopy, x-ray spectroscopy, and static deionized water contact angle measurements. FindingsContact angles dependent on UV light exposure time were observed. From the scanning electron microscopy analysis, it was confirmed that the UV treatment does not produce morphology changes over the surface. Nevertheless, the x-ray spectroscopy revealed that the UV exposed samples react when they are brought into contact with deionized water, improving the adhesion of the surface. The original hydrophobic behaviour of the surface is recovered (up to 98 %) after 3 h of thermal treatment. Furthermore, the thermal recovery analysis reveals a correlation between the recovery percentage and the applied temperature.

Morphology-dependent optical and wetting behavior of GLAD PTFE thin films

E-beam evaporation equipped with glancing angle deposition arrangement (GLAD) was used to fabricate nanostructured polytetrafluoroethylene (PTFE) films in a single-step coating process. Three sets of PTFE coatings were prepared using various oblique angles, e-beam currents, and deposition times to explore the effects of deposition parameters on the properties of PTFE nanostructured coatings. Water contact angle (WCA) of the coatings was found to be enhanced with the increase in all the above process parameters. Optical transmittance of the coatings was also found to be improved with the above parameters except for in the case of an increase in thickness of the films (in very high thickness region), where the transmittance was degraded due to light scattering from the sample surface. After all the optimizations, the ~ 130-nm-thick GLAD PTFE sample prepared with highest e-beam current was found to be more suitable for antireflection and self-cleaning applications. The single-sided coating demonstrates a very high average transmittance of ~ 95.6% (with a wideband transmittance spectrum among the others) in the visible and NIR wavelength range with excellent self-cleaning nature (WCA ~ 156°, sliding angle ~ 10°). The trend of measured WCA with respect to surface roughness follows the Cassie–Baxter model. Overall, the study demonstrates the possibility of fabricating highly transparent self-cleaning coatings using the GLAD technique, which is potentially useful for fabricating protecting cover glasses in solar panels.

Investigation on the microstructural and mechanical properties of a Polytetrafluoroethylene thin film by radio frequency magnetron sputtering

Relying on magnetron sputtering technology, a Polytetrafluoroethylene (PTFE) thin film was deposited on silicon substrate. We systematically investigated the atomic bonding, growth mode, and surface morphology of the as-prepared PTFE thin films by different nominal deposition power with different thicknesses. The mechanical properties including elastic modulus, hardness, strain rate sensitivity and creep resistance were carefully detected in a thick (1270 nm) PTFE film by an instrumental nanoindentation. In comparison to its bulk counterpart, PTFE thin film owns much higher elastic modulus and stronger resistances to the plastic and time-dependent plastic deformation. The results of its chemistry and mechanical properties show the films are hydrophobic and of higher mechanical strength. The enhanced mechanical properties of PTFE thin film could be intrinsically tied to its complex fluorocarbon groups which generated from the breakage and re-organization of C-F chains during sputtering process. The creep resistance of PTFE thin film was approximately two times stronger than the bulk PTFE.

Particle-Laden Droplet-Driven Triboelectric Nanogenerator for Real-Time Sediment Monitoring Using a Deep Learning Method.

Continuous information on the suspended sediment in the water system is critical in various areas of industry and hydrological studies. However, because of the high variation of suspended sediment flow, challenges still remain in developing new techniques implementing simple, reliable, and real-time sediment monitoring. Herein, we report a potential method to realize real-time sediment monitoring by introducing a particle-laden droplet-driven triboelectric nanogenerator (PLDD-TENG) combined with a deep learning method. The PLDD-TENG was operated under the single-electrode mode with a triboelectric layer of polytetrafluoroethylene (PTFE) thin film. The working mechanism of the PLDD-TENG was proved to be induced by liquid-PTFE contact electrification and sand particle-electrode electrostatic induction. Then, its performance was explored under various particle parameters, and the results indicated that the output signal of the PLDD-TENG was very sensitive to the sand particle size and mass fraction. A convolutional neural network-based deep learning method was finally adopted to identify the particle parameters based on the output signal. High identifying accuracies over 90% were achieved in most of the cases by the proposed method, which sheds light on the application of the PLDD-TENG in real-time sediment monitoring.

Multi-directional triboelectric nanogenerator based on industrial Q-switched pulsed laser etched Aluminum film

A multi-directional Spring-Assisted triboelectric nanogenerator (SA-TENG) with a power of 0.42 mW is successfully fabricated based on a simple industrial technique. Here, a Q-switched pulsed laser (QSL) is applied to etch the Aluminum film surface. It enables to create a micro-nanostructured surface with a groove system perpendicular to the distance between the grooves of 20μm. For Polytetrafluoroethylene (PTFE) thin films, however, the surface is modified by the Inductively Coupled Plasma Reactive Ion Etching technology (ICP-RIE). The role of QSL Etched Aluminum in enhancing the triboelectric performance of the Al/PTFE device is demonstrated. Indeed, the open-circuit voltage and the short-circuit current both increase from 80 V to 130 V and from 3.9 μA to 6.6 μA, respectively, when the Al surface is treated. In the vertically vibrating operation mode, the SA-TENG produces a voltage, current and power of 66 V, 5.1 μA and 350 μW, respectively, at the average velocity of 10 cm/s. In addition, the horizontally rotation mode with a rotation angle of 30° and an angular velocity of 30 deg/s generates an open-circuit voltage of 57 V, a short-circuit current of 4.4 μA and a power of 64 μW at 107 Ω. The real-time practical applicability of SA-TENG was confirmed by the lighting up of 92 LEDs connected in series and by the charging up of a 10 μF capacitor to 2.5 V in 35 s.

Bivariate analysis of the hydrophobic textiles obtained by plasma treatment

This paper presents aspects concerning the bivariate analysis of the textiles surfaces treated by RF plasma technologies (Ar RF plasma and SF6 RF plasma) to obtain the hydrophobic effect. Besides this, it was studied the remnant or temporary hydrophobic effect obtained by polytetrafluoroethylene (PTFE) thin-film by physical vapor deposition (PVD) technique and SF6 RF plasma technique. In this paper, there are presented the bivariate analysis of the parameters and characterization of hydrophobic textile samples (cotton 100% with mass 401 g/m2) by investigation of the water contact angle using the device VCA OPTIMA and resistance to surface wetting by James Heal spray tester. The morphological modification of the textile was evaluated by scanning electron microscope with magnification x8000. Following these investigations there has been observed that the treatment with polytetrafluoroethylene is even more harmful to the environment, offering a hydrophobic effect resistant in time, for approximative 101 days, and the treatment by SF6 RF plasma confer a temporary effect for 24 hours.

The role of PVD sputtered PTFE and Al2O3 thin films in the development of damage tolerant coating systems

The surfaces of artificial joints are susceptible to premature wear which reduces their service life leading to the increased risk of revision arthroplasty. Tribological coatings having low coefficients of friction (CoF) and which are also biocompatible are therefore required to minimise such risks.Metal matrix composite (MMC) coatings exhibiting a modified toughness structure, thus reducing the potential to crack were successfully fabricated by cold spray (CS) technology. The coatings comprised of an ultra-low wear polytetrafluoroethylene (PTFE)+alumina (Al2O3) composite, firstly delineated by Burris and Sawyer in 2006, were prepared on cold sprayed substrate and the functionality of such coatings in terms of enhanced frictional properties was investigated.In this study, PTFE+Al2O3 thin film coatings were prepared by physical vapour deposition (PVD) and incorporated with cold sprayed MMC coatings to produce a damage tolerant coating system designed to extend the service life of artificial movable joint surfaces.Surface characterisation analysis indicated the formation of a PTFE–Al2O3 nanocomposite forming between the PTFE and Al2O3. This composite thin film exhibited excellent friction reducing ability up to an applied load of 7N. Regardless of whether the Ti–6Al is manufactured by a layer-by-layer approach or co-sputtering method, the CoF is reduced to below 0.1 at the start of the test. Furthermore, the results reveal that the PVD sputtered PTFE+Al2O3 thin film functionalises the cold sprayed surface by offering a self-lubricating effect and that PVD combined with CS is reliable for devising material systems operating in high-wear applications.

Tribological performance of polydopamine + Ag nanoparticles/PTFE thin films

Abstract This study aims to improve the polytetrafluoroethylene (PTFE) thin film adhesion to stainless steel substrates by incorporating Ag nanoparticles (AgNPs) in a polydopamine (PDA) underlayer. Three different weight percent (1.0 wt%, 1.5 wt%, and 2.0 wt%) of AgNPs were added to the PDA deposition solution, resulting in an increased underlayer roughness. A 3.6-time increase in durability was achieved by adding only 2.0 wt% of AgNPs. Scratch and wear tests demonstrated the improved adhesion and wear resistance of the PDA + AgNPs/PTFE thin films. The improvement was attributed to the increased underlayer roughness, denser fibrillar PTFE network, and enhanced film transfer, all brought by the AgNPs.

Self-cleanable, waterproof, transparent, and flexible Ag networks covered by hydrophobic polytetrafluoroethylene for multi-functional flexible thin film heaters

We demonstrate a self-cleanable, waterproof, highly transparent, and flexible Ag network covered by a very thin transparent polytetrafluoroethylene (PTFE) layer using typical magnetron sputtering for multi-functional flexible thin film heaters used in smart windows. By passivation of the self-assembled Ag network with very thin PTFE films, we fabricated a multi-functional Ag network suitable for flexible thin film heaters. At a PTFE thickness of 10 nm, the Ag network passivated by hydrophobic PTFE layer showed a low sheet resistance of 11.64 Ohm/square, high optical transmittance of 80.20% at a wavelength of 550 nm, and high contact angle of 102.42°. In addition, sputtering of the PTFE layer on the Ag network improved the mechanical flexibility and reliability of the Ag network electrode. The flexible and transparent thin film heater (TTFH) with Ag network electrode covered by PTFE layer showed a saturation temperature of 120 °C at low voltage of 4.5 V and power of 2.45 W, as well as a hydrophobic surface suited for self-cleaning smart windows. These multi-functional performances of TTFH indicate that the Ag network/PTFE film-based flexible TTFH could be used as self-cleanable, waterproof TTFHs for curved smart windows in smart buildings and automobiles.