Dip-coating Speed Research Articles

Dielectric Liquid Microlens Array with Tunable Focal Length Based on Microdroplet Array Created via Dip-Coating Method.

A dielectric liquid microlens array (LMA) with a tunable focal length was fabricated by using a microdroplet array generated through the dip-coating method. The process began with treating the octadecyltrichlorosilane (OTS) layer with selective UV/O3 irradiation for 20 min to establish a hydrophilic-hydrophobic patterning surface. The substrate was subsequently immersed in glycerol and then withdrawn at a constant rate to create a microdroplet array. Upon filling the cell with matching oil (SL5267) and placing it within a square array of a 200 μm diameter glycerol microdroplet array, the LMA was produced. The focal length ranged from approximately -0.96 to -0.3 mm within a voltage range of 0 to 60 Vrms. The glycerol microdroplets, characterized by their shapes, sizes, curvatures, and filling factors, can be precisely controlled by designing an OTS patterning or adjusting the dip-coating speed. This approach offers a rapid and high-throughput method for preparation. Our approach to fabricating tunable LMA offers several advantages, including simplicity of fabrication, uniform structural properties, cost-effectiveness, polarization independence, and excellent optical performance. These focus-tunable LMAs hold significant potential for applications in image processing, 3D displays, medical endoscopy, and military technologies.

Design and preparation of superhydrophobic, broadband and double-layer antireflective coatings

As one of the most widely used optical films, antireflective coating (ARC) is widely used in lasers, display screens and solar cells. In this article, the double-layer ARC coating consists of a bottom layer using SiO2-TiO2 composite nanomaterials and a top layer of SiO2 modified with Hexamethyldisilazane (HMDS). The optimal parameters of the double-layer ARC were obtained through the simulation software Macleod. Meanwhile, the aging time of SiO2 sol, the volume fraction of HMDS, the annealing temperature, the dip-coating speed, and the volume fraction of TiO2, which affect the refractive index of the bottom and top layers, were explored in order to match the best parameters. By adjusting the structure of the bottom and top layers, the double-layer broadband ARC coating has a maximum transmittance of 97.6% in the 400-1800 nm spectral range, and an average transmittance of 96.0%. In addition, HMDS was used to modify the SiO2 sol to obtain a double-layer ARC with superhydrophobic properties with a hydrophobic angle of 151.4°. After the high-temperature and high-humidity environment test, the antireflective performance of the double-layer ARC has not changed significantly, demonstrating the broad prospects for application in large outdoor solar photovoltaic power plants. Moreover, this work not only provides a new method for adjusting the refractive index of the coating, but also opens up a new way for the preparation of broadband ARC.

STUDY THE EFFECT OF COATING USING NANOPARTICLES ON THE CORROSION OF ALUMINUM ALLOY IN DIFFERENT SOLUTIONS

Corrosion resistance of metals is one of the most important topics for researchers. In this work, epoxy-TiO2 nanocomposite has been developed for protection of 6061AL alloy. The dip-coating technique used to deposit the coating on 6061 Al alloy substrate. Different concentrations of TiO2 NPs (1,3,5 )Wt% have been used to study the corrosion behavior in 3.5% NaCl medium. Also, 200,150 and 100 mm/min dipping speeds have been employed for 1%wt TiO2 to show their effects on coating layer and corrosion rate. Characterization of coated surfaces were investigated by AFM, FESEM andEDS,while theelectrochemical measurementswas using to evaluate protective nature of the coating. The results have shown that the corrosion rate has decreased with 1wt% of TiO2 NPs concentration. The corrosion rate (mm/y) of (7.131×10-4, 1.803×10-3 and 8.183×10-3) have been obtained with (1 , 3 and 5 wt% TiO2) respectively. The results have been confirmed by using a constant dip-coating speed of 200 mm/min, and the results of the corrosion rate for 200,150 and 100 mm/min have been 7.131×10-4, 7.984×10-4and 8.293×10-4 respectively. The morphology of coating film which characterized by SEM, have shown that the TiO2 NPs spread and was covered by epoxy very well. The AFM test used to study the surface average roughness of coating film where the Ra for sample with epoxy coating is24.4 nm and for sample with (epoxy _1%wt TiO2) is 1.508 nm.

Durable superhydrophilic and antireflective coating for high-performance anti-dust photovoltaic systems

Antireflection coatings have received extensive attention due to their unique ability to reduce the reflection losses of incident light in photovoltaic (PV) systems. In this study, we report a hybrid silica sol coating fabricated via a simple and cost-effective base/acid-catalyzed two-step sol–gel method. The prepared coating exhibits these main properties: high transmittance, superhydrophilic, and anti-dust effect. Experimental conditions to achieve high transmittance were systematically optimized, such as aging time of the base-catalyzed silica sol and dip-coating speed. A transmittance improvement of about 6.35% compared to the bare glass substrate was then obtained. The morphology and film structure were also characterized. The coatings have a closed and dense structure which, combined with their superhydrophilicity, endowed them with excellent anti-dust performance, as well as high mechanical properties, with a pencil hardness of 4H. Furthermore, the coating showed great resistance to high temperature and high humidity as well as high stability to long-time outdoor exposure. The results suggest the good reliability of the prepared coatings for PV solar glass application.

Characteristics of kesterite CZTS thin films deposited by dip-coating technique for solar cells applications

In this work, we synthesis Cu2ZnSnS4 (CZTS) thin films by sol–gel method associated to dip-coating technique on the ordinary glass substrates. We investigated the effect of dip-coating speed on the structural, morphological, optical and electrical properties of films at various speeds 30, 40, 50 and 60 mm/min, respectively. The films have been characterized by different characterization techniques such as: X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), UV–Visible spectrophotometer and four point probe method. XRD spectra showed pure kesterite CZTS with a preferential orientation along (112) plane. Raman scattering measurement showed the peak at 332 cm−1 correspond to pure CZTS phase. XPS analysis confirmed the presence of Cu, Zn, Sn and S elements on the surface of deposited CZTS. SEM images showed an improvement in density and uniformity with increasing dip-coating speed. The band gap energy is decreased with increasing of dip-coating speed in the range of 1.38–1.45 eV. The electrical conductivity increased between 4.90 and 5.81 (Ω.cm)−1. These characteristics make the deposited CZTS film a suitable material as an absorber layer in photovoltaic devices.

Application of Taguchi method to optimize the sol–gel dip-coating process of the semiconductor Cu2ZnSnS4 with good optical properties

This paper presents the optimal configuration of parameters for the elaborated Cu2ZnSnS4 (CZTS) absorber layer, using the sol–gel method associated with dip-coating technique on ordinary glass substrates. Taguchi design of experiments with L27 (38) orthogonal array, a signal-to-noise (S/N) ratio, and an analysis of variance (ANOVA) were used to determine the best optical properties for photovoltaic applications (optical bandgap energy) of CZTS thin films. Eight factors named annealing temperature, Cu/(Zn+Sn) ratio, Zn/Sn ratio, S/metal ratio, number of pre-annealing and dip coating, dip-coating cycle, annealing time, and dip-coating speed were chosen. To conduct the tests, we apply Taguchi method; three levels were fixed for each factor. The most important factors of the deposition approach on the optical properties of the fixed as-synthesized CZTS films were determined. The analysis of the obtained results indicated that the important parameters are the Zn/Sn ratio and annealing temperature in air by employing Taguchi approach. A validation test is also carried out to check whether the found optimal combinations of the parameter are correct. CZTS thin-film synthesis with optimal conditions has been characterized, using an X-ray diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), UV–visible spectrophotometer, and four-point probe method. XRD data show a kesterite structure with a preferential orientation along the (112) plan; UV–visible spectrophotometer indicated that the bandgap energy of the CZTS thin film is 1.51 eV and a cross section showed the suitable film thickness in the order of ~1.80 µm.

Controlled Growth of Large-Area Aligned Single-Crystalline Organic Nanoribbon Arrays for Transistors and Light-Emitting Diodes Driving

Organic field-effect transistors (OFETs) based on organic micro-/nanocrystals have been widely reported with charge carrier mobility exceeding 1.0 cm2 V−1 s−1, demonstrating great potential for high-performance, low-cost organic electronic applications. However, fabrication of large-area organic micro-/nanocrystal arrays with consistent crystal growth direction has posed a significant technical challenge. Here, we describe a solution-processed dip-coating technique to grow large-area, aligned 9,10-bis(phenylethynyl) anthracene (BPEA) and 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) single-crystalline nanoribbon arrays. The method is scalable to a 5 × 10 cm2 wafer substrate, with around 60% of the wafer surface covered by aligned crystals. The quality of crystals can be easily controlled by tuning the dip-coating speed. Furthermore, OFETs based on well-aligned BPEA and TIPS-PEN single-crystalline nanoribbons were constructed. By optimizing channel lengths and using appropriate metallic electrodes, the BPEA and TIPS-PEN-based OFETs showed hole mobility exceeding 2.0 cm2 V−1 s−1 (average mobility 1.2 cm2 V−1 s−1) and 3.0 cm2 V−1 s−1 (average mobility 2.0 cm2 V−1 s−1), respectively. They both have a high on/off ratio (Ion/Ioff) > 109. The performance can well satisfy the requirements for light-emitting diodes driving.Graphical

Cylindrical relative humidity sensor based on poly-vinyl alcohol (PVA) for wearable computing devices with enhanced sensitivity

In this paper, a wearable resistive-type humidity sensor is fabricated on a cylindrical organic substrate for the first time. This sensor contained polyvinyl-alcohol (PVA) as the sensing material, which was applied by the dip-coating method at the middle, and copper (Cu) thin film was applied by RF magnetron sputtering for the side electrodes. The resistance was measured for 60–90%RH. Thus, the value was decreased by hydrogen bonds between the hydroxyl groups and water molecules in the highly humid condition. In addition, as the dip-coating speed and number of coats varied, corresponding factors α and β, which were related to the activation energy, thickness, and/or conductance, were suggested based on Ohm’s law and conductivity equations. Moreover, to verify its durability as a wearable computing device, repetitive bending tests were performed with different bending times and radii.

Transparent Nanostructured Titania Coatings with Self- cleaning and Antireflective Properties for Photovoltaic Glass Surfaces

Transparent titania (TiO2) coatings having self-cleaning and antireflection (AR) properties, for application as surface functional layer in cover glasses of photovoltaic (PV) devices, were prepared, characterized and tested. The coating preparation is made by forming first a nanosol through controlled hydrolysis of a tetraisopropyl orthotitanate (TIPT) precursor. The nanosol is then deposited on the glass substrates by dip- coating with a subsequent step of calcination. This work reports the effect of the preparation parameters on both optical and morphological properties of the obtained coatings. The nanostructure and texture of the samples were characterized by X-ray diffraction, UV-vis spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM), while transmittance measurements were carried out to assess the AR properties. Self-cleaning properties were investigated by water contact angle measurements and photocatalytic activity tests. Films with good optical characteristics and high transmittance (T losses < 1 % compared to bare glass) have been obtained at low dip-coating speed (6 mm/s) and high nitric acid concentration (HNO3 0.5 N). The best transmittance values were obtained by calcination of the sample at 500 °C, but a higher amount of acid catalyst in the nanosol synthesis allows to reduce the calcination temperature to 400 °C, while maintaining good optical properties and crystallinity of the thin film.

Polyimide Dielectric Layer on Filaments for Organic Field Effect Transistors: Choice of Solvent, Solution Composition and Dip-Coating Speed

Abstract In today’s research, smart textiles is an established topic in both electronics and the textile fields. The concept of producing microelectronics directly on a textile substrate is not a mere idea anymore and several research institutes are working on its realisation. Microelectronics like organic field effect transistor (OFET) can be manufactured with a layered architecture. The production techniques used for this purpose can also be applied on textile substrates. Besides gate, active and contact layers, the isolating or dielectric layer is of high importance in the OFET architecture. Therefore, generating a high quality dielectric layer that is of low roughness and insulating at the same time is one of the fundamental requirements in building microelectronics on textile surfaces. To evaluate its potential, we have studied polyimide as a dielectric layer, dip-coated onto copper-coated polyester filaments. Accordingly, the copper-coated polyester filament was dip-coated from a polyimide solution with two different solvents, 1-methyl-2-pyrrolidone (NMP) and dimethylformaldehyde. A variety of dip-coating speeds, solution concentrations and solvent-solute combinations have been tested. Their effect on the quality of the layer was analysed through microscopy, leak current measurements and atomic force microscopy (AFM). Polyimide dip-coating with polyimide resin dissolved in NMP at a concentration of 15w% in combination with a dip-coating speed of 50 mm/min led to the best results in electrical insulation and roughness. By optimising the dielectric layer’s properties, the way is paved for applying the subsequent semi-conductive layer. In further research, we will be working with the organic semiconductor material TIPS-Pentacene

Surface Morphology of Polyimide Thin Film Dip-Coated on Polyester Filament for Dielectric Layer in Fibrous Organic Field Effect Transistor

Abstract The idea of wearable electronics automatically leads to the concept of integrating electronic functions on textile substrates. Since this substrate type implies certain challenges in comparison with their rigid electronic companions, it is of utmost importance to investigate the application of materials for generating the electronic functions on the textile substrate. Only when interaction of materials and textile substrate is fully understood, the electronic function can be generated on the textile without changing the textile’s properties, being flexible or stretchable. This research deals with the optimization of the dielectric layer in a fibrous organic field effect transistor (OFET). A transistor can act as an electrical switch in a circuit. In this work, the polyimide layer was dip-coated on a copper-coated polyester filament. After thoroughly investigating the process conditions, best results with minimal thickness and roughness at full insulation could be achieved at a dip-coating speed of 50 mm/min. The polyimide solution was optimal at 15w% and the choice for the solvent NMP was made. In this paper, details on the pre-treatment methods, choice of solvent and dip-coating speed and their effect on layer morphology and thickness, electrical properties and roughness are reported. Results show that the use of polyimide as a dielectric layer in the architecture of a fibrous OFET is promising. Further research deals with the application of the semiconductor layer within the mentioned architecture, to finally build an OFET on a filament for application in smart textiles.

Effects of dip-coating speed and annealing temperature on structural, morphological and optical properties of sol-gel nano-structured TiO2thin films

We reported material characterization of the nano-structured TiO 2 thin films prepared by the sol-gel dip-coating process on glass substrates. The dependence of the structural, morphological and optical properties of the synthesized films on the fabrication parameters such as withdrawal velocity and annealing temperature were investigated by the techniques of X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible spectrophotometry. The results indicate that for the TiO 2 films annealed at 500 °C there exhibits (1 0 1) XRD peak corresponding to the anatase phase of TiO 2 . The latter is consistent with the recorded Raman signal observed at 142 cm -1 ( E g mode) and 391 cm -1 (B 1g mode), respectively. From the analyses made on the SEM micrographs and AFM images, it was revealed that the morphology and surface roughness of the thin films would depend on the withdrawal speed and the heat treatment temperature. The UV-visible spectroscopy analyses show that all the films were transparent in the visible region with an average transmittance of more than 70%. With an increase on the dip-coating speed from 1 cm/min to 3 cm/min, we observed a spectral red shift of the absorption edge from 3.76 eV to 3.71 eV, indicating a decrease in the bandgap energy ( E g ) of the films.

Corrosion Protection of Aluminum by Hydrophobization Using Nanoparticle Polymer Coatings Containing Plant Oil

A polymer coating for corrosion protection of aluminum surfaces (AA 1050A) was evaluated, including styrene maleimide nanoparticles synthesized in aqueous dispersion by imidization of poly(styrene-co-maleic anhydride) in presence of vegetable oils (SMI/oil). Different nanoparticle coatings with mono- and poly-unsaturated oils were evaluated through Raman spectroscopy, water contact angle measurements and atomic force microscopy (AFM). One type of nanoparticles with soy oil was selected based on the high oil reactivity and formation of homogeneous coating with low content of free oil, high degree of imidization, high hydrophobicity and long-term stability. After optimization of the coating composition, the organic nanoparticles were mixed with 20 wt.% carnauba wax and 50 wt.% styrene/butadiene, resulting in a contact angle of 109o. The aluminum surfaces were pre-treated under different conditions including phosphatization or alkaline etching, and dip-coating speed variation. The best corrosion resistance after salt-spray testing occurs for samples that were etched for 10 s at 25 oC, followed by dip-coating at 125 mm min-1. The resulting coating layer is relatively thin, but with good corrosion resistance in parallel with the highest contact angle values and slightly higher average surface roughness than coatings deposited at low speeds.

Optimization of Porous SiO&lt;sub&gt;2&lt;/sub&gt; Antireflective (AR) Coatings Used in Encapsulating Solar Modules

Base catalyzed sol-gel derived porous SiO2 coatings are prospectively used as antireflective (AR) layer for encapsulating solar modules. In this paper, the properties of SiO2 AR layers coated on solar glass by different dip-coating and annealing conditions are investigated and optimized. It is shown that the transmittance of the AR coating is affected by these preparation conditions which closely related to the thickness and surface morphology. As results, the SiO2 coating had a better performance both in transmittance and adhesion when the dip-coating speed and the annealing temperature are 0.036mm/s and 300°C respectively. Further more, TMCS hydrophobic treatment was adopted to make the AR coating meet the demands of practical application.

Tunable Assembly of Vanadium Dioxide Nanoparticles to Create Porous Film for Energy-Saving Applications

Nanoparticle-assembled vanadium dioxide (VO2) films have been easily prepared with the assistance of cetyltrimethylammonium vanadate (CTAV) precursor which exhibits self-assembly properties. The obtained VO2 film has a micro/nano hierarchical porous structure, so its visible-light transmittance is significantly improved (∼25% increased compared to continuous film). The VO2 particle density as well as the film porosity can be facilely controlled by adjusting experimental parameters such as dip-coating speed. Accordingly, film optical properties can also be tuned to a large extent, in particular the visible transmittance (Tvis) and near-infrared switching efficiency (ΔTnir). These VO2 nanoparticle-assembled films prepared by this novel method provide a useful model to research the balance between Tvis and ΔTnir.

Microstructure Evolution and Device Performance in Solution-Processed Polymeric Field-Effect Transistors: The Key Role of the First Monolayer

Probing the role of the first monolayer in the evolution of the film polymer microstructure is essential for the fundamental understanding of the charge carrier transport in polymeric field-effect transistors (FETs). The monolayer and its subsequent microstructure of a conjugated polymer [poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene), PBTTT] film were fabricated via solution deposition by tuning the dip-coating speed and were then studied as accumulation and transporting layers in FETs. Investigation of the microstructure of the layers prepared at different coating velocities revealed that the monolayer serves as an important base for further development of the film. Significant improvement of the charge carrier transport occurs only at a critical multilayer network density that establishes the required percolation pathways for the charge carriers. Finally, at a low dip-coating speed, the polymer chains are uniaxially oriented, yielding pronounced structural anisotropy and high charge carrier mobilities of 1.3 cm(2) V(-1) s(-1) in the alignment direction.

Additional Effects of Silver Nanoparticles on Bactericidal Efficiency Depend on Calcination Temperature and Dip-Coating Speed

There is an increasing interest in the application of photocatalytic properties for disinfection of surfaces, air, and water. Titanium dioxide is widely used as a photocatalyst, and the addition of silver reportedly enhances its bactericidal action. However, the synergy of silver nanoparticles and TiO(2) is not well understood. The photocatalytic elimination of Bacillus atrophaeus was examined under different calcination temperatures, dip-coating speeds, and ratios of TiO(2), SiO(2), and Ag to identify optimal production conditions for the production of TiO(2)- and/or TiO(2)/Ag-coated glass for surface disinfection. Photocatalytic disinfection of pure TiO(2) or TiO(2) plus Ag nanoparticles was dependent primarily on the calcination temperature. The antibacterial activity of TiO(2) films was optimal with a high dip-coating speed and high calcination temperature (600°C). Maximal bacterial inactivation using TiO(2)/Ag-coated glass was also observed following high-speed dip coating but with a low calcination temperature (250°C). Scanning electron microscopy (SEM) showed that the Ag nanoparticles combined together at a high calcination temperature, leading to decreased antibacterial activity of TiO(2)/Ag films due to a smaller surface area of Ag nanoparticles. The presence of Ag enhanced the photocatalytic inactivation rate of TiO(2), producing a more pronounced effect with increasing levels of catalyst loading.

Two-Dimensional Non-Close-Packing Arrays Derived from Self-Assembly of Biomineralized Hydrogel Spheres and Their Patterning Applications

Two-dimensional (2D) non-close-packing arrays were fabricated by dip-coating hydrogel spheres unloaded and loaded with CaCO3 formed via in situ biomineralization. The separation distance between the particles can be well tuned by the dip-coating speed and the concentration of the gel spheres. The resultant 2D non-close-packing arrays can be used as templates to direct the self-assembly of silica colloidal spheres for formation of binary colloidal crystals with different patterns. The resulting binary structures may be manipulated by the surface wettability. Besides, they can be utilized as masks to generate functional patterned substrates.

Sol–gel route to pseudocubic shaped α-Fe 2O 3 alcohol sensor: preparation and characterization

α-Fe 2O 3 hydrosol was synthesized by sol–gel method with FeCl 3·6H 2O as the raw material and its thin films were prepared by dip-coating technique. The structure, morphology and spectroscopy of the thin films were characterized by XRD, AFM, UV–vis and FT-IR analysis methods. The results showed that uniform α-Fe 2O 3 monolayer and multilayers could be obtained at certain dip-coating speed. The particles were pseudocubic shaped, with the mean particle size of about 58 nm. The formation mechanism of α-Fe 2O 3 particles was explored by IR spectra and the change of the system acidity and conductivity. The results indicated that α-Fe 2O 3 particles formed from the intermediate complex β-FeOOH. The gas-sensing properties of the multilayers to alcohols with different chain length were measured at room temperature. The thin films exhibited high sensitivity and rapid response–recovery characteristics to these gases. The film can detect C 3H 7OH vapor concentration as low as 2 ppm. The response and recovery time of the film to CH 3OH and C 2H 5OH vapor is within 20 and 50 s, respectively.

Fabrication of regioregular poly(3-hexylthiophene) field-effect transistors by dip-coating

We report the influence of dip-coating speed and concentration of the polymer solution on the characteristics of field-effect transistors (FETs) fabricated in the bottom-contact structure with regioregular poly(3-hexylthiophene) (RR-P3HT) as the active semiconducting material. For each concentration of the polymer in solution, there is an optimum dip coating speed for film deposition with highest field effect mobility; for example, with chloroform as solvent the optimum speed is 0.5 mm/min for a solution containing 1.0 mg/ml and 1.0 mm/min for a solution containing 2.5 mg/ml. Based upon AFM studies of the resulting film morphology, we conclude that the formation of a “rod-like” morphology is the origin of the improved carrier transport in the FET channel.