Antifogging Properties Research Articles

Highly Transparent, Robust Hydrophobic, and Amphiphilic Organic-Inorganic Hybrid Coatings for Antifogging and Antibacterial Applications.

The control of surface wettability through a combination of surface roughness, chemical composition, and structural modification has attracted significant attention for antifogging and antibacterial applications. Herein, a two-step spin-coating method for amphiphilic organic-inorganic hybrid materials with incorporated transition metal ions is presented. The coating solution was prepared via photochemical thiol-ene click reaction between the mercapto functional group in trimethylolpropane tris(3-mercaptopropionate) and the vinyl functionalized silica precursor 3-(trimethoxysilyl)propyl methacrylate. In the first step of coating, a glass substrate was coated using a solution of metal nitrate hydrates and subsequently showed hydrophobic properties. As the second step, the spin-coated glass substrate was further coated with silica nanoparticles (SiO2 NPs) and polycaprolactone triol (PCT) suspension, where the contents of SiO2 NPs were fixed at 0.1 wt %, unless otherwise noted. The coated substrate exhibited hydrophilic properties. For comparison, the coating was also formulated with the SiO2 NPs/PCT suspension without SiO2 NPs and with 0.5 wt % SiO2 NPs as well as by adjusting different coating layer thicknesses. The surface morphology and chemical compositions of the obtained coating materials were analyzed by field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The transparency and static contact angle of coated samples were measured by UV-visible spectrophotometry and drop shape analysis, respectively. It was concluded that our novel hybrid coating materials exhibited excellent antibacterial and antifogging properties with extremely high scratch resistance and transparency.

Fabrication of superhydrophillic and graded index antireflective double layer coating for solar photovoltaics module using aerosol impact deposition assembly

In the study presented, a double layer graded refractive indices silicon dioxide nano-porous coating was deposited on glass substrates to reduce the optical losses in solar photovoltaics using the technique referred as Aerosol Impact Deposition Assembly (AIDA). The proposed system consists of the gaseous precursors namely Silane, Oxygen and Helium that ionize in the plasma reaction chamber of AIDA to form silica nanoparticles. The nanoparticles size and shape can be controlled by the flow rates of each precursor gas, pressure difference in reaction and deposition chamber, and the proportion of helium gas. The assembly accelerates the silica nanoparticles towards deposition chamber with high impact speed using a small slit nozzle where they are coated on a glass/silicon substrate placed on a moving stage. Using this technique, thin film silica nanoparticle double layer was coated and characterized using Transmission electron microscope (TEM), Scanning Electron Microscope and Atomic Force Microscope to determine the particle shape, size, and morphology respectively. The average nanoparticle size determined from TEM image was 12.5 nm while the porosity of the top and bottom thin films was 60% and 42%, respectively. The UV-Spectroscopy results showed that reflection losses were decreased from 9% to 2% in a broad range of solar spectrum i.e., wavelength 300-1200 nm. In addition, due to high porosity and sufficient roughness, the coated thin film showed excellent self-cleaning and antifogging properties with water contact angle less than 5o. Moreover, short current density of the cell was increased by 1.4 mA/cm2, from 39.1 mA/cm2 to 40.5 mA/cm2, which shows enhancement in the electrical performance of the solar cell.

Anti-Fogging, Photocatalytic and Self-Cleaning Properties of TiO2-Transparent Coating

Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2- sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 oC. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 oC improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.

Ultrasonically Induced Polymerization and Polymer Grafting in the Presence of Carbonaceous Nanoparticles

Nanotechnology refers to technologies using at least one nanometric dimension. Most advances have been in the field of nanomaterials used in research and industry. The vast potential of polymeric nanocomposites for advanced materials and applications such as hybrid nanocomposites with customized electrical conductivity, anti-bacterial, anti-viral, and anti-fog properties have attracted considerable attention. The number of studies on the preparation of nanocomposites in the presence of carbon materials, i.e., carbon nanotubes (CNTs) and graphene, has intensified over the last decade with the growing interest in their outstanding synergic properties. However, the functionality of such nanocomposites depends on overcoming three key challenges: (a) the breakdown of nanoparticle agglomerates; (b) the attachment of functional materials to the nanoparticle surfaces; and (c) the fine dispersion of functional nanoparticles within the polymeric matrices. Ultrasonic polymerization and grafting in the presence of nanoparticles is an innovative solution that can meet these three challenges simultaneously. These chemical reactions are less well known and only a few research groups have dealt with them to date. This review focuses on two main pathways to the design of ultrasonically induced carbon-based nanocomposites: the covalent approach which is based on the chemical interactions between the carbon fillers and the matrix, and the non-covalent approach which is based on the physical interactions.

Antifogging and antibacterial properties of amphiphilic coatings based on zwitterionic copolymers

Tackling fogging and microbial infection problems related to the endoscope lens remain challenges due to visual disturbances and bacterial threats to human health. Herein, highly transparent antifogging and antibacterial coatings were developed in a facile way by thermal curing of zwitterionic copolymers poly(n-butyl methacrylate-co-2-aminoethyl methacrylate-co-sulfobetaine methacrylate)s with 1,3,5-triformylbenzene. Characterizations of surface chemical composition and wettability suggested that the copolymer coatings exhibited amphiphilicity with a hydrophobic surface and internal hydrophilicity. The prepared amphiphilic coating exhibited excellent antifogging properties both in vivo and in vitro. The introduction of hydrophobic n-butyl methacrylate and cationic aminoethylmethacrylate could improve the stability and antibacterial capability of the coating. The growth inhibition rates of the coatings against Staphylococcus aureus and Escherichia coli were up to 99% and the copolymer coatings with the zwitterionic groups had low hemolytic rates less than 3%. The amphiphilic copolymer coatings combined antifogging and antibacterial properties may have a promising potential for applications in biomedical devices.

Lubricant-infused directly engraved nano-microstructures for mechanically durable endoscope lens with anti-biofouling and anti-fogging properties

While a clear operating field during endoscopy is essential for accurate diagnosis and effective surgery, fogging or biofouling of the lens can cause loss of visibility during these procedures. Conventional cleaning methods such as the use of an irrigation unit, anti-fogging surfactant, or particle-based porous coatings infused with lubricants have been used but proven insufficient to prevent loss of visibility. Herein, a mechanically robust anti-fogging and anti-biofouling endoscope lens was developed by forming a lubricant-infused directly engraved nano-/micro-structured surface (LIDENS) on the lens. This structure was directly engraved onto the lens via line-by-line ablation with a femtosecond laser. This directly engraved nano/microstructure provides LIDENS lenses with superior mechanical robustness compared to lenses with conventional particle-based coatings, enabling the maintenance of clear visibility throughout typical procedures. The LIDENS lens was chemically modified with a fluorinated self-assembled monolayer (F-SAM) followed by infusion of medical-grade perfluorocarbon lubricants. This provides the lens with high transparency (> 70%) along with superior and long-lasting repellency towards various liquids. This excellent liquid repellency was also shown to be maintained during blood dipping, spraying, and droplet condensation experiments. We believe that endoscopic lenses with the LIDENS offer excellent benefits to endoscopic surgery by securing clear visibility for stable operation.

Optimizing Communication in Schools and Other Settings During COVID-19

Optimizing Communication in Schools and Other Settings During COVID-19

Preparation of antifogging and enhanced antimicrobial biopolymer coating and its applications in lettuce preservation

This study focused on the development of a new biopolymer coating with antifogging and antimicrobial properties. The dual functional coatings, which consisted of multiple layers of chitosan (CS) and alginate dialdehyde (ADA), were prepared by layer-by-layer assembly driven by Schiff base, hydrogen bonding, and electrostatic interactions. Fourier transform-infrared spectroscopy indicated the formation of a Schiff base between CS and ADA. The six-layer coating had high transparency, optimum hydrophilicity and antifogging property as characterized by spectroscopy, water contact angle analysis and antifogging testing. The antibacterial activity of the six-layer coating was better than that of CS alone. Furthermore, the six-layer coating reduced decay of fresh-cut lettuce during storage. The results from this study suggest that coatings consisting of CS and ADA can prevent fogging, inhibit microbial growth, and maintain the quality of fresh produce throughout storage.

Wet-Style Superhydrophobic Antifogging Coatings for Optical Sensors.

Transparent substrates are widely used for optical applications from lenses for personal and sports eyewear to transparent displays and sensors. While these substrates require excellent optical properties, they often suffer from a variety of environmental challenges such as excessive fogging and surface contamination. In this work, it is demonstrated that a wet-style superhydrophobic coating, which simultaneously exhibits antifogging, antireflective, and self-cleaning properties, can be prepared by pattern transferring low-surface-energy microstructures onto a heterostructured nanoscale thin film comprising polymers and silica nanoparticles. The polymer-silica nanocomposite base layer serves as a hydrophilic reservoir, guiding the water molecules to preferentially condense into this underlying region and suppress reflection, while the low-surface-energy microstructure enables contaminants adsorbed on the surface to be easily removed by rinsing with water.

Highly durable antifogging coatings resistant to long-term airborne pollution and intensive UV irradiation

Antifogging coatings have tremendous application potential as they can prevent undesired fogging and blurring on transparent substrates when exposed to humid environment. However, most antifogging surfaces suffer from poor durability and tend to lose the antifogging property in the short term caused by airborne pollutant adsorption or environment weathering (e.g., UV irradiation). To address this issue, a series of zwitterionic and hydroxylated superhydrophilic coatings were prepared and their long-term antifogging properties under harsh conditions were systematically studied, including in a normal laboratory environment, under accelerated pollution test by exposing surfaces to acetic acid steam, and under UV irradiation. The prepared zwitterionic coatings showed significantly improved durability than the hydroxylated surfaces in all the test conditions, attributed to the chemical inertness and stability of the zwitterionic moieties. By incorporating zwitterionic coating and nanoscale roughness together, the longevity of antifogging surfaces can be further greatly improved, and eyeglasses treated with such nanostructured zwitterionic coating kept decent antifogging property even after storage for up to 210 days. The present nanostructured zwitterionic coatings are promising for real-world antifogging applications that can survive practical environmental fouling and weathering.

Large-Scale Formation of Fluorosurfactant-Doped Transparent Nanocomposite Films Showing Durable Antifogging, Oil-Repellent, and Self-healing Properties.

Transparent nanocomposite films with multiple functionalities, such as durable antifogging, dynamic oleophobic, self-healing properties, were successfully prepared by a simple spin- or spray-coating method using aqueous solutions of poly(vinylpyrrolidone) (PVP) and aminopropyl-functionalized nanoclay (AMP-clay) platelets. In this study, anionic/waterborne perfluorooctanesulfonic acid potassium salt (PFOS) was premixed with the aqueous PVP solution to achieve a homogeneous dispersion of PFOS. Due to the addition of PFOS, the resulting nanocomposite film surfaces displayed statically hydrophobic (static water contact angle over 90°) and dynamically oleophobic (5 μL of oil droplets could slide off of the surface at low sliding/substrate tilt angles of less than 10°) behaviors. In spite of our nanocomposite film surface exhibiting a statically hydrophobic nature, the antifogging properties remained unchanged even after being left under high-humidity conditions (over 80% relative humidity) for 3 days. Thanks to both exceptional water-absorbing properties of PVP/AMP-clay matrices and good mobility of PFOS driven by moisture, our oil-repellent nanocomposite films could be repeatedly self-healed even after both severe physical (cutting, scratching, or falling sand abrasion) and chemical (vacuum UV oxidation) damages. Large-scale fabrication of this multifunctional nanocomposite film (30 cm × 30 cm) could also be successfully demonstrated by a spray-coating method based on in situ gel formation.

Hydrophilic nano-SiO2/PVA-based coating with durable antifogging properties

Hydrophilic SiO2/poly(vinyl alcohol) (PVA) coating prepared by solution blended method showed high light transmittance and durable antifogging performance. The effects of SiO2 content and pH value of SiO2 suspension on the morphology and properties of hydrophilic coating were studied by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, contact angle test, ultraviolet visible light spectrophotometer, and antifogging test. Results showed that the PVA had good compatibility with nano-SiO2 because of the formation of Si–O–C chemical bond at the interface between nano-SiO2 and PVA. When prepared at pH = 7, SiO2/PVA coatings (SiO2/PVA mass ratio of 0.8) were hydrophilic, with a water contact angle of 22.9°, and exhibited papilla-like surface features (RMS = 7.6 nm). Polyethylene (PE) samples coated with this SiO2/PVA film exhibited a light transmittance of up to 90%, between 560 and 700 nm, and remained fog-free for more than 1 month after exposure to water at 60°C (QB/T 4475-2013 standard). Water-resisting and wear-resisting tests revealed that antifogging coatings demonstrated excellent mechanical properties.

Multifunctional closed-pore silica/titania composite antireflective coatings based on self-assembly process

This paper reports multifunctional closed-pore silica/titania composite antireflective coatings (ARCs) prepared through combining with emulsion polymerization, sol-gel chemistry, electrostatic self-assembly, and calcination process. The ARCs show high transmittance, with maximum transmission of 98.1% at wavelength of 519 nm and the average transmittance in visible light region (400–700 nm) of 97.1%, a 7.0% increase compared with that of bare glass. Anatase nano titania decorated ARCs are obtained via controlling calcination temperature at 600 °C for 5 min and proved by XRD results. The ARCs exhibit excellent self-cleaning properties, illustrated by accelerating organic decomposition under UV and sunlight. Furthermore, the ARCs possess outstanding superhydrophilic and antifogging properties. In addition, water is the only solvent used in the whole process. These features make the method have specific advantages in the ARCs field.

Sodium alginate oxide assembly layered double hydroxide and its structure-activity relationship to anti-fogging properties and flame retardancy of leather

The small molecular volatilized during the leather fogging process will pollute the air environment inside the car and make leather products flammable. In this paper, layered double hydroxide (LDH) was modified by different dosage of oxidized sodium alginate (OSA) via exfoliation-reassembly, and its structure were investigated by XRD and TEM. Then modified Zanthoxylum Bungeanum Maxim Seed Oil/ OSA modified LDH (MZBMSO/OSA-LDH) were obtained by introducing OSA modified LDH (OSA-LDH) into modified Zanthoxylum Bungeanum Maxim Seed Oil (MZBMSO), and used MZBMSO/OSA-LDH in leather fatliquoring process. The effect of the introduction of OSA-LDH on the anti-fogging and flame retardancy of leather was investigated. Compared to the MZBMSO treated leather, MZBMSO/OSA-LDH-0.2 treated leather exhibited remarkable improvement on fogging value of the leather, which was decreased by 45%. Furthermore, the leather treated by MZBMSO/OSA-LDH-0.4 has reduction of length of charring and smoke density around 36.1% and 37.5%, respectively. A potential interaction mechanism demonstrates that under the influence of OSA-LDH, an organic-inorganic interpenetrating network structure formed by leather collagen fibers-fatliquor molecule-LDH layer, which utilized to the steric hindrance and adsorption effect to hinder small molecule migration inside the leather fibers, thereby suppressing the fogging of the leather.

A multifunctional antifog, antifrost, and self-cleaning zwitterionic polymer coating based on poly(SBMA-co-AA)

In this work, a multifunctional coating was developed by grafting a zwitterionic poly[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)-co-acrylic acid [poly(SBMA-co-AA)] polymer onto a glass slide, which possesses excellent antifog, antifrost, and self-cleaning properties. These properties are attributed to the strong hydration of the hydrophilic zwitterionic PSBMA segments. The durability of the coating can be improved because the carboxyl group (–COOH) of the PAA segment enables formation of a robust covalent bond with the amino group (–NH2) on the substrate. The coating presents long-term stability, as proved by water contact angles, which were stable at 12 ± 1° after exposing the coating in ambient environment for 60 days or immersing in deionized water for 24 h. In addition, the underwater oil contact angle measurement demonstrated that an oil stain on the zwitterionic poly(SBMA-co-AA) polymer coating can be easily removed upon contact with water, showing self-cleaning performance. These properties verified that the zwitterionic multifunctional coating exploited in this research has many potential application prospects, including construction, automotive, aerospace, shipbuilding, biomedical, and other optical fields.

Antifogging/Antibacterial Coatings Constructed by N-Hydroxyethylacrylamide and Quaternary Ammonium-Containing Copolymers.

Endoscopic surgery has gained widespread applications in various clinical departments, and endoscope surfaces with antifogging and antibacterial properties are essential for elaborate procedures. In this work, novel antifogging/antibacterial coatings were developed from a cationic copolymer and a hydrophilic copolymer, polyhedral oligomeric silsesquioxane-poly(quaternary ammonium compound-co-2-aminoethyl methacrylate hydrochloride) [POSS-P(QAC-co-AEMA)] and poly(N-hydroxyethylacrylamide-co-glycidyl methacrylate) [P(HEAA-co-GMA)] via a facile and green blending method. Such transparent coatings showed excellent antifogging performance under both in vitro and in vivo fogging conditions, mainly attributed to the high water-absorbing capability of HEAA and QAC. Antibacterial assays proved that the blending coatings had a superior antibacterial property, which could be improved with the proportion of POSS-P(QAC-co-AEMA) because of the bactericidal efficiency of cationic QAC. Meanwhile, owing to the high hydratability of HEAA, the blending coatings exhibited a bacteria-repelling property. By simply tuning the blending ratio of POSS-P(QAC-co-AEMA) and P(HEAA-co-GMA), the comprehensive bacteria-killing and bacteria-repelling properties of the coatings were achieved. Moreover, after incubating with red blood cells, the prepared blending coatings presented a lower hemolytic rate of less than 5%. The findings provided a potential means for addressing the challenge of fogging and bacterial contamination occurring in endoscopic lenses and other medical devices.

Atmospheric pressure Townsend discharges as a promising tool for the one‐step deposition of antifogging coatings from N2O/TMCTS mixtures

AbstractThe need to ensuring the “see‐through” property of transparent materials when exposed to sudden temperature changes or very humid conditions has encouraged the development of antifogging strategies, such as the deposition of (super)hydrophilic coatings. However, despite the effectiveness of these coatings in combating the effects of fogging, most of the coating techniques explored to date are typically time‐consuming and environment‐unfriendly. Bearing this in mind, we demonstrate that the application of dielectric barrier discharges operated at atmospheric pressure proves to be successful in preparing antifogging coatings on glass samples from 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS) and nitrous oxide (N2O). The antifogging performance of the coatings was found to be governed by the [N2O]/[TMCTS] ratio and not by the [N2O] + [TMCTS] sum. Coatings prepared under a [N2O]/[TMCTS] = 30 were superhydrophilic (water contact angles ≈ 5°–10°) due to surface silanol groups and endowed glass samples with a superior antifogging property, as revealed by the ASTM F 659‐06 test. In contrast, because of the lesser hydrophilicity (water contact angles ≈ 60°), coatings prepared under a [N2O]/[TMCTS] = 10 did not endow glass samples with antifogging property. Regardless of the deposition conditions, the plasma‐deposited coatings displayed crack‐free smooth surfaces (Rrms = 2−4 nm).

Development of polyurethane-based superhydrophobic coatings on steel surfaces.

In this study, a superhydrophobic coating on steel surface has been developed with polyurethane, SiO2 nanoparticles and hexadecyltrimethoxysilane by using a spin-coating technique. Characterization of the coated steel surface was done by using the contact angle measurement technique, scanning electron microscopy and Fourier transform infrared spectroscopy. With a water tilt angle of 4° ± 2° and static contact angle of 165° ± 5°, the coated surface shows a superhydrophobic and self-cleaning nature. Chemical, thermal, mechanical stability tests and droplet dynamic studies were done to evaluate performance of the coating. Excellent self-cleaning, anti-fogging and anti-corrosion properties of coated steel surfaces make them ideal for industrial applications. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 3)'.

Oil-repellent and antifog coatings based on poly(vinyl alcohol)/hydrolyzed poly (styrene-co-maleic anhydride)/fluorocarbon surfactant

In order to improve the oil-repellent and antifouling ability of the antifog coatings, a poly(vinyl alcohol)/hydrolyzed poly (styrene-co-maleic anhydride)/fluorocarbon surfactant (PVA/H-PSMA/FC) was prepared by incorporating a fluorocarbon surfactant into PVA/H-PSMA via hydrogen bonds. The microstructure, antifog and oil-repellent properties were investigated in our study, and the results indicate that the strong interaction between the PVA/H-PSMA and the FC provides a good fixation for the FC inside or on the surface of the coatings. The water contact angle (WCA) ranges from 59° to 69° and the oil contact angle (OCA) ranges from 35° to 50°, which means that the PVA/H-PSMA/FC coatings are hydrophilic and oleophilic. The results also demonstrate that the prepared PVA/H-PSMA/FC coating exhibits excellent antifog properties and high transparency. Moreover, the oil droplets may slip off the coating surface without any residue and the glide angle is below 12°. A low content of FC loaded creates a large space between FC molecules, thus providing enough hydrophilicity on the PVA/H-PSMA surface and achieving excellent antifog performance. Meanwhile, the mobile fluorinated alkyl chains on the surface can be reorganized and act as “slides” to easily move oil droplets at low TA, providing oil repellency. The excellent oil-repellency makes the transparent PVA/H-PSMA/FC antifog coatings have potential application prospects in the field of surface protection of optical equipment and solar panel.

A facile and less-polluting electrochemical method to fabricate multifunctional superhydrophobic film on iron materials

Iron materials have the extremely widespread applications and they are common in all kinds of frame structures, such as iron tower. However, it is well known that ironwork is easy to rust. Besides, in cold environment the freezing rain adhered to the iron facility can also bring huge potential security problems. Herein, we present a modified electrochemical machining (ECM) method by applying a mixed aqueous solution of Na2MoO4 and NaCl to fabricate superhydrophobic film on iron materials followed by fluoroalkylsilane (FAS) modification. The proposed ECM method can not only generate rough microstructures very rapidly even at low electrical parameters, but also reduce the pollution of the electrolyte by recycling the corrosion products. The sandpaper abrasion and knife scratch tests were utilized to demonstrate the mechanical strength of the obtained superhydrophobic surfaces. Good self-cleaning properties were also showed by using several kinds of contaminants and corrosive solutions. Furthermore, we demonstrated the good anti-fogging property by using atomizer and the anti-icing property by static and dynamic anti-icing tests in a cold environment to show the practical applications of the prepared film. We believe that the modified ECM method has broad application prospects.