Fluoropolymer Films Research Articles

Deposition of thin composite films consisting of fluoropolymer and silver nanoparticles having surface plasmon resonance

This paper describes the method of obtaining composite coatings consisting of silver nanoparticles covered by a fluoropolymer film. The morphology and optical properties of resulting coatings are given within. The presence of a surface plasmon resonance (SPR) minimum of silver nanoparticles deposited on glass and fused silica surfaces has been revealed. The paper describes a shift towards the infrared (IR) region when the average size of deposited silver nanoparticles is changed. However, coating the nanoparticles in a fluoropolymer film does not significantly shift their resonance.

High-Performance Single-Walled Carbon Nanotube-Based Thin-Film Transistors by Reducing Charge Transfer

We demonstrate high-performance single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) using the simple and robust method of an interacting fluoropolymer encapsulation with thermal annealing in vacuum to reduce the charge transfer. With an optimized combination of the fabrication process and the device configuration, drop-casted SWCNT-TFTs exhibit a field-effect mobility of $\sim 18$ cm2/ $\text{V}\,\cdot \, \text{s}$ in the linear regime, an ON–OFF-current ratio of $\sim 10^{6}$ , a threshold voltage of around 0 V, and a subthreshold swing of 97 mV/decade, which is among the best results that have been achieved in 2-D random networks of the SWCNTs. We also investigate the instability characteristics in the SWCNT-TFTs encapsulated with fluoropolymer during the prolonged electrical bias-stress. Interestingly, the drop in drain current of the SWCNT-TFTs was partially recovered with a second phenomenon that increases the drain current after a certain time. The hydrophobic surface that the fluoropolymer film possesses, reduced the chemical interaction of charge carriers with the hydroxyl (–OH) functional groups which act as defects in the SWCNT-TFTs.

シリコン表面に気相蒸着したナノ厚さフッ素系潤滑膜の耐凝着性能の評価

Anti-stiction coating must be one of the key technologies to ensure reliability of NEMS devices and to improve accuracy in a nanoimprint lithography. Typically, polymer films were coated on a silicon surface for anti-stiction. In this study, we proposed vapor-phase deposition technique to form fluoropolymer film on silicon surfaces. Fluoropolymer used in this study was perfluoropolyether (PFPE) Fomblin Zdol (molecular weight of 2000 amu). As a substrate to coat the Zdol, we used a silicon wafer. Anti-stiction properties were verified by measuring surface energies by a contact angle measurement and also by measuring stiction forces using an atomic force microscope (AFM). As a result, it was revealed that the films thicker than 0.5 nm effectively reduced the adhesion forces down to approximately a half of that of the bare silicon surface.

Preparation and Characterization of Thermally Stable Silicon-Containing Fluoropolymer Matrix for Application to Erbium-Doped Waveguide Amplifiers

This study focuses on the fabrication of fluoropolymer films as erbium(Er3+) host material with a goal of achieving sufficient thermal stability, optical clarity in the optical communication region and a chemical resistance to withstand typical fabrication processing and operation conditions. To satisfy the demands mentioned above, acrylo-polyhedral oligomeric silsesquioxane as heat-resistance improver, 2,2,3,3,4,4,5,5-octafluoropentyl acrylate as fluorinated acrylic monomer, tetrahydrofurfuryl acrylate as solubility enhancer, 3-(trimethoxysilyl)propyl methacrylate as both a silane coupling agent and another heat-resistance improver and Darocur 4265 as photoinitiator were used. Various compositions were evaluated to obtain high quantity of Er3+ ions in the polymer matrix, high thermal stability and high transparency.

Hydrophobic and superhydrophobic surfaces fabricated by plasma polymerization of perfluorohexane, perfluoro(2-methylpent-2-ene), and perfluoro(4-methylpent-2-ene)

Fluoropolymer films were deposited on silicon (1 0 0) wafers, glass, epoxy, and hierarchical dual-sized filler epoxy composite surfaces by plasma polymerization of perfluorohexane, perfluoro(2-methylpent-2-ene), and perfluoro(4-methylpent-2-ene). The procedure involved continuous wave plasma-enhanced deposition, followed by a discharge-off period, with the monomer gas feed maintained. Silanization of silicon wafers and glass surfaces with triethoxyvinylsilane was employed to improve plasma fluoropolymer bonding to these substrates. The presence of double bonds in perfluoro(2-methylpent-2-ene) and perfluoro(4-methylpent-2-ene) was found to influence fluoropolymer coating topography, thereby increasing surface roughness in modified glass and epoxy substrates. All fluorocarbons provided a similar level of hydrophobization of flat substrates, exhibited by water contact angles (WCA) of about 110°. Hydrophobization of nanocomposite hierarchical surfaces by plasma polymerization provided superhydrophobic surfaces, with WCA of 160° and contact angle hysteresis below 8°.

Fabrication of Thiol-Ene "Clickable" Copolymer-Brush Nanostructures on Polymeric Substrates via Extreme Ultraviolet Interference Lithography.

We demonstrate a new approach to grafting thiol-reactive nanopatterned copolymer-brush structures on polymeric substrates by means of extreme ultraviolet (EUV) interference lithography. The copolymer brushes were designed to contain maleimide functional groups as thiol-reactive centers. Fluoropolymer films were exposed to EUV radiation at the X-ray interference lithography beamline (XIL-II) at the Swiss Light Source, in order to create radical patterns on their surfaces. The radicals served as initiators for the copolymerization of thiol-ene "clickable" brushes, composed of a furan-protected maleimide monomer (FuMaMA) and different methacrylates, namely, methyl methacrylate (MMA), ethylene glycol methyl ether methacrylate (EGMA), or poly(ethylene glycol) methyl ether methacrylate (PEGMA). Copolymerization with ethylene-glycol-containing monomers provides antibiofouling properties to these surfaces. The number of reactive centers on the grafted brush structures can be tailored by varying the monomer ratios in the feed. Grafted copolymers were characterized by using attenuated total reflection infrared (ATR-IR) spectroscopy. The reactive maleimide methacrylate (MaMA) units were utilized to conjugate thiol-containing moieties using the nucleophilic Michael-addition reaction, which proceeds at room temperature without the need for any metal-based catalyst. Using this approach, a variety of functionalities was introduced to yield polyelectrolytes, as well as fluorescent and light-responsive polymer-brush structures. Functionalization of the brush structures was demonstrated via ATR-IR and UV-vis spectroscopy and fluorescence microscopy, and was also indicated by a color switch. Furthermore, grafted surfaces were generated via plasma activation, showing a strongly increased wettability for polyelectrolytes and a reversible switch in static water contact angle (CA) of up to 18° for P(EGMA-co-MaMA-SP) brushes, upon exposure to alternating visible and UV-light irradiation.

Magnetic droplet actuation on natural (Colocasia leaf) and fluorinated silica nanoparticle superhydrophobic surfaces

Interest in digital microfluidics (DMF), where discrete droplets are manipulated in a miniaturized device, has grown rapidly due to the versatility that arises from non-linear control of fluids. Adding superparamagnetic particles to the fluid allows the droplet to be manipulated by magnetic fields, such as that from a simple permanent magnet, removing some of the complexity of previous DMF devices and adding enhanced robustness. The magnetic field strength need not be high to control commercially available magnetic silica microparticles, however a hydrophobic surface is required to provide reduced friction. In this study, three types of hydrophobic surfaces were explored for their use in the magnetic actuation of water droplets containing magnetic particles. A conventional fluoropolymer film was found to have excessive frictional resistance to effectively actuate droplets. A natural superhydrophobic surface, the Colocasia leaf, was found to have too much surface microstructure to allow the magnetic particles to move freely over the surface. The commercially available Ultra-Ever Dry®, on the other hand, was suitable for effective magnetic actuation of aqueous and mixed droplets as it provided a robust, virtually frictionless surface. Based on fluorinated silica nanoparticles, this surface allowed a 20μL water droplet to be manually pulled by a magnet at speeds in excess of 550mms−1.

Nonthermal Plasma Hybrid Process for Preparation of Organic Electroluminescence Fluoropolymer Film Devices

In this paper, organic electroluminescence fluoropolymer film devices, i.e., organic light-emitting diodes (OLEDs) comprising polychlorotrifluoroethylene (PCTFE) films treated by an atmospheric-pressure nonthermal plasma (NTP) graft-polymerization process, are investigated. PCTFE films can provide a long lifetime for OLEDs because of their excellent gas barrier properties; however, they are difficult to laminate, owing to low adhesiveness. The surfaces of PCTFE films are treated by an atmospheric-pressure NTP-graft-polymerization process to improve their adhesiveness, and then, indium tin oxide and a luminous layer are deposited on the treated PCTFE films. As a result, OLEDs comprising PCTFE films are successfully demonstrated.

Electrowetting Technique for Measuring the Thickness of Spin-Coated Hydrophobic Fluoropolymer Films

Electrowetting Technique for Measuring the Thickness of Spin-Coated Hydrophobic Fluoropolymer Films

Screen printing insulator coatings for electrofluidic display devices

The screen printing of amorphous fluoropolymer films as insulators for electrofluidic display device use is demonstrated. Screen printing enables the hydrophobic dielectric to be directly patterned at device level with the required film thickness as well as excellent material utilisation. The films give very good electrical performance, with high uniformity and dielectric strength, and the resulting devices exhibit comparable electro-optic behaviour to those fabricated with spin-coated films.

Structure Formation Mechanisms and Electrical Properties of PVD Fluoropolymer Films

The mechanisms of forming fluoropolymer coatings on silicon substrates via condensation from an active gas phase using directed flows of accelerated electrons and ions are studied. It is demonstrated that electrical properties of the resulting fluoropolymer films strongly depend on the technological parameters of the deposition process. Their most optimal properties are reported when condensation takes place at the temperatures within ~373–386 K. It is shown that thermal annealing of the films in vacuum at 430–470 K improves their electrophysical parameters by re-evaporating the low-molecular complexes from the structure and decreasing the concentration of defects and spin-radicals, while annealing in air gives rise to formation of additional polar groups.

A unique “cage–cage” shaped hydrophobic fluoropolymer film derived from a novel double-decker structural POSS with a low dielectric constant

A novel double-decker structural fluorinated POSS and a diphenol POSS were first synthesized for preparing a unique “cage–cage”-shaped hydrophobic fluoropolymer film with a low dielectric constant.

Thermo-mechanical characterisation of fluoropolymer films for concentrated solar thermal applications

Renewable and clean energy sources are getting more important. Therefore, a resource-saving alternative to conventional solar concentrators has been designed. This pneumatic pre-stressed concentrator is completely made of polymer films. Due to its pre-stressed construction the mechanical properties of the transparent film have a high influence on the lifetime of the concentrator. The dimension stability of the film significantly affects the effectiveness of the systems due to the shift of the focus point of the reflected radiation after deformation. Therefore, special requirements concerning thermal and mechanical properties in the application relevant temperature range have to be fulfilled.The aim of this work is to characterise fluoropolymer films as transparent layers in a pneumatic pre-stressed sun concentrator. Fluoropolymers have been chosen due to their excellent optical and mechanical properties and their extraordinary stability against ultraviolet radiation. A total of five different fluoropolymer films have been selected and their thermal, mechanical and thermo-mechanical properties at application relevant temperatures were characterised. Even though no material complies with the requirements, an ethylene-tetrafluorethylene-copolymer (ETFE) is suggested, with the recommendation to adapt and adjust the film thickness and the production process to influence the morphology and subsequently the thermo-mechanical behaviour of the material.

Low-voltage and hysteresis-free organic thin-film transistors employing solution-processed hybrid bilayer gate dielectrics

This study presents a promising approach to realize low-voltage (<3 V) organic thin-film transistors (OTFTs) exhibiting improved electrical and optical stability. Such device performance results from the use of solution-processed hybrid bilayer gate dielectrics consisting of zirconium dioxide (high-k dielectric) and amorphous fluoropolymer, CYTOP® (low-k dielectric). Employing a very thin amorphous fluoropolymer film reduces interfacial defect-states by repelling water molecules and other aqueous chemicals from an organic semiconductor active layer due to the hydrophobic surface-property. The chemically clean interface, stemming from decrease in density of trap states improves all the key device properties such as field-effect mobility, threshold voltage, and sub-threshold swing. Furthermore, degradation by electrical bias-stress and photo-induced hysteresis were suppressed in OTFTs employing hybrid bilayer gate dielectrics.

다양한 환경에서 감마선으로 조사된 불소고분자 필름들의 구조 및 열적/물성 변화

본 연구에서는 다양한 환경에서 방사선 조사된 불소고분자 필름(PTFE, FEP, PFA, PVDF 및 ETFE)들의 화학 구조 및 물성 변화를 관찰하였다. 방사선은 <TEX>$Co^{60}$</TEX> 감마선을 사용하였으며, 공기 분위기와 질소 분위기 및 진공 상태에서 조사하였다. 방사선 조사된 불소고분자 필름의 FTIR 분석을 통하여 방사선에 의해 생성된 라디칼이 공기 중 산소와 반응하여 산화반응이 진행되었음을 확인하였다. 또한 DSC를 이용하여 방사선 조사에 의해 변화되는 불소고 분자의 용융열 및 결정화도를 관찰하여 고분자 구조에 따른 절단 및 가교반응을 확인하였다. 인장 강도 실험을 통하여 방사선 조사 환경에 따른 불소고분자의 물성 변화를 관찰한 결과 공기 분위기에서 조사된 불소고분자 필름들의 기계적 물성이 현저히 떨어지는 것을 관찰하였다. In this study, the changes in the chemical structure and the physical property of fluoropolymer films (PTFE, FEP, PFA, PVDF, and ETFE) induced by <TEX>$Co^{60}$</TEX> gamma ray in air, <TEX>$N_2$</TEX>, and vacuum environments were investigated. FTIR spectra of the irradiated fluoropolymers indicate that the oxidation proceeded by the reaction of radicals generated by irradiation with oxygen in air. The changes in the heat of fusion and the degree of crystallinity of the irradiated fluoropolymers were investigated using DSC and the results indicate that the scission and crosslinking reactions of the irradiated fluoropolymers were largely influenced by the chemical structure. It was also found that the mechanical property of the irradiated fluoropolymer films under an air atmosphere was significantly decreased.

Homeotropic Alignment of Lyotropic Chromonic Liquid Crystals Using Noncovalent Interactions

We report on the homeotropic alignment of lyotropic chromonic liquid crystals (LCLCs). Homeotropic anchoring of LCLCs is difficult to achieve, and this challenge has limited development of applications for LCLCs. In this work, homeotropic alignment is achieved using noncovalent interactions between the LCLC molecules and various alignment layers including graphene, parylene films, poly(methyl methacrylate) films, and fluoropolymer films. The LCLC molecules are unique in that they self-assemble via noncovalent interactions in water into elongated aggregates which, in turn, form nematic and columnar liquid crystal (LC) phases. Here we exploit these same noncovalent interactions to induce homeotropic anchoring of the nematic LCLC. Homeotropic alignment is confirmed by polarized optical microscopy and conoscopy. We also report on novel transient stripe textures that occur when an initial flow-induced planar alignment transforms into the equilibrium homeotropic alignment required by boundary conditions. An understanding of this behavior could be important for switching applications.

Enhanced corrosion resistance and hemocompatibility of biomedical NiTi alloy by atmospheric-pressure plasma polymerized fluorine-rich coating

To improve the corrosion resistance and hemocompatibility of biomedical NiTi alloy, hydrophobic polymer coatings are deposited by plasma polymerization in the presence of a fluorine-containing precursor using an atmospheric-pressure plasma jet. This process takes place at a low temperature in air and can be used to deposit fluoropolymer films using organic compounds that cannot be achieved by conventional polymerization techniques. The composition and chemical states of the polymer coatings are characterized by fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The corrosion behavior of the coated and bare NiTi samples is assessed and compared by polarization tests and electrochemical impedance spectroscopy (EIS) in physiological solutions including simulated body fluids (SBF) and Dulbecco's Modified Eagle's medium (DMEM). The corrosion resistance of the coated NiTi alloy is evidently improved. Protein adsorption and platelet adhesion tests reveal that the adsorption ratio of albumin to fibrinogen is increased and the number of adherent platelets on the coating is greatly reduced. The plasma polymerized coating renders NiTi better in vitro hemocompatibility and is promising as a protective and hemocompatible coating on cardiovascular implants.

Synthesis, Characterization, Curing and Properties of Carboxyl-Terminated Liquid Fluoropolymers

Low molecular weight carboxyl-terminated liquid fluoropolymers with M n ranged from 2300 to 8000 were prepared by oxidative degradation of VDF-HFP copolymer. The factors to control M n of liquid fluoropolymers are types and contents of alkaline and oxidants. FTIR, 1H NMR, 19F NMR, 13C NMR and GPC were used to characterize the structure and M n of the liquid fluoropolymers. The cure reaction and properties of the carboxyl-terminated liquid fluoropolymers with epoxy resin were discussed. Thermal properties including thermal stability and T g of these cured fluoropolymer films were also examined. Cured films have good hydrophobic and oleophobic properties, as well as good chemical resistance.

A monolithic and flexible fluoropolymer film microreactor for organic synthesis applications.

A photocurable and viscous fluoropolymer with chemical stability is a highly desirable material for fabrication of microchemical devices. Lack of a reliable fabrication method, however, limits actual applications for organic reactions. Herein, we report fabrication of a monolithic and flexible fluoropolymer film microreactor and its use as a new microfluidic platform. The fabrication involves facile soft lithography techniques that enable partial curing of thin laminates, which can be readily bonded by conformal contact without any external forces. We demonstrate fabrication of various functional channels (~300 μm thick) such as those embedded with either a herringbone micromixer pattern or a droplet generator. Organic reactions under strongly acidic and basic conditions can be carried out in this film microreactor even at elevated temperature with excellent reproducibility. In particular, the transparent film microreactor with good deformability could be wrapped around a light-emitting lamp for close contact with the light source for efficient photochemical reactions with visible light, which demonstrates easy integration with optical components for functional miniaturized systems.

Microfabrication and Metal Plating Technologies on Polytetrafluoroethylene Film Surface Treated by Atmospheric-Pressure Nonthermal-Plasma Graft Polymerization Process

Microfabrication by photolithography and nickel plating of fluoropolymer film, exposed to atmospheric-pressure nonthermal-plasma (NTP) graft polymerization, are investigated. Electroless nickel plating on the NTP-graft-polymerizationtreated polytetrafluoroethylene (PTFE) film is successfully achieved. Highly adhesive nickel plating is obtained by reverse bend test. Furthermore, photolithographic patterns are formed on the plated PTFE film. This process is expected to be applied to flexible printed substrates and millimeter-wave antenna.