Antifogging Performance Research Articles

Mechanically stable superhydrophilic antifog surface by microwave assisted sol-gel method

In this study, optically transparent and mechanically stable of superhydrophilic composite thin films were fabricated via a low-cost one-step one pot microwave-assisted sol-gel technique. The microwave reaction time was optimized according to surface characterization of homo TMOS surfaces. The reaction time was arranged as 17.5 min having low cost compared to the conventional sol-gel technic. The wettability performance and antifogging behavior of PVA-TMOS composite films were investigated according to variation of the PVA content. The static contact angle values of the composite surfaces were found to vary between 30o and 5o. Superhydrophilic surface having tilt angle is 9o showed a good antifogging performance. Mechanical durability of the composite surface was also characterized by scratching and adhesive tape test. In addition, the time depending water contact angle was also measured for 100 days. It is found that TMPV96 composite film having 0.096 (wt,%) content of PVA showed higher mechanical performance with transparent superhydrophilic surface.

Bioinspired functional glass integrated with multiplex repellency ability from laser-patterned hexagonal texturing

Optically transparent glass integrated with other functions, especially water/fog/ice/contaminate-repellent ability, is highly demanded for electronic displays, vehicle windshields and large-area building windows. Yet, the functional glass currently used in most of these applications faces challenges in integration fabrication and the trade-off between intrinsic optical property and imparted new functions, despite some advances in transparent superhydrophobic glass over the past decade. To this end, inspired by the functional hexagonal microstructure array of mosquito compound eye, a novel strategy to achieve multifunctional integration glass (MIG) is developed for omni-repellency towards water/fog/ice/contaminants in practical applications. The laser textured MIG performed well in durability and transmittance (about 98% of the pristine glass transmittance), which might be ascribed to the microstructure optimization. Moreover, some capabilities are also endowed to this glass, including a diversified self-cleaning ability for a variety of contaminants, a stable antifogging performance in dense fog environment, and an outstanding icing delay effect at low temperature. This work provides a promising fusion concept toward the design of multiplexed platforms that can integrate different functions in one glass for commercially versatile glass.

Transparent hydrophobic thermal insulation CsxWO3-ZnO-SiO2 coatings:Energy saving, anti-dust and anti-fogging performance

CsxWO3-ZnO-SiO2 smart coatings were proposed to achieve multiple functions, such as thermal insulation, anti-dust, anti-fogging and blocking harmful ultraviolet light, etc. The transparent hydrophobic hybrid resins were prepared from methyltriethoxysilane (MTES) and SiO2 sol, which was used as the substrate of the composite coating. The CsxWO3 is served as the near-infrared (NIR) absorber, and the ZnO is functioned as the ultraviolet (UV) blocking agent. Coatings with different ratios of CsxWO3 and ZnO were successfully prepared by co-blending with nano-SiO2 resin. The morphology, microstructure, surface composition, hydrophobicity, thermal stability, anti-dust and optical property of the composite coatings were investigated comprehensively. The transmittance of C10Z10 (CsxWO3 10%, ZnO 10%, nano-SiO2 resin 80%) coating at 370 nm is 2.3%, and the value of Solar Energy Transmittance Selectivity (SETS) is 0.665, which exhibits excellent NIR shielding ability. Compared with nano-SiO2 resin coating, the thermal insulation temperature difference can reach 7.0 °C. The C10Z10 coating showed good durability in the twenty times anti-dust repeated tests and the efficiency could maintain 70.3% after the repeating tests. The coating showed excellent sustainability after a 45-day outdoor exposure experiment and a 240 h of artificial accelerated aging experiment. Thus, the proposed CsxWO3-ZnO-SiO2 coatings are promising for outdoor smart windows.

A multifunctional and environmentally-friendly method to fabricate superhydrophilic and self-healing coatings for sustainable antifogging

Antifogging films are essential in many areas, such as eyeglasses, windshields, goggles and so on. In this work, a transparent antifogging film was successfully prepared on glass by spin-coating a mixture of poly(acrylic acid) (PAA), carboxymethyl cellulose (CMC) and iron (III) chloride hexahydrate (FeCl3·6H2O). The coated film was superhydrophilic and showed excellent anti-frosting and self-healing properties. The composite coating was resistant to fouling by oil and had a very small water sliding angle about 3.1°. This coating could maintain its antifogging performance after by tape-peeling test for 80 cycles and being exposed to UV irradiation for 96 h. The diverse desirable functions demonstrated and the facile preparation procedure of the film offer huge potential in many practical applications.

Response surface methodology as a predictive tool for the fabrication of coatings with optimal anti-fogging performance

In this study, response surface methodology was applied to optimize the anti-fogging performance of coatings deposited on commercial glass samples from 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS)/N2O mixtures by atmospheric pressure plasma enhanced chemical vapor deposition. The effect of the dissipated power (DP), [N2O]/[TMCTS] ratio, and sample scroll speed on the anti-fogging performance was investigated by means of a Box-Behnken experimental design. The regression model relating transmittance of the coated glasses to these deposition parameters revealed that the anti-fogging performance strongly depends on the second-order interaction of the dissipated power and [N2O]/[TMCTS] ratio (i.e., DP × [N2O]/[TMCTS]). Contour plots showed that the dissipated power required to prepare optimal anti-fogging coatings should be of at least 0,7, 0,5 or 0,4 W cm−2, if the [N2O]/[TMCTS] ratio in the plasma is 20, 30, or 40, respectively. When placed over water at 50°C, the coated glass samples allowed 80% (or more) of 590-nm light to pass through, thus meeting the minimal anti-fogging requirement for alpine skier goggles and faceshields. Despite not having a significant impact on the anti-fogging performance, the sample scroll speed is key to fabricating coatings with the desired thickness during in-line manufacturing.

Quantifying Surface Wetting Properties Using Droplet Probe Atomic Force Microscopy.

The functional properties of a surface, such as its anti-fogging or anti-fouling performance, are influenced by its wettability. To quantify surface wettability, the most common approach is to measure the contact angles of a liquid droplet on the surface. While well established and relatively easy to perform, contact angle measurements were developed to describe macroscopic wetting properties and are difficult to perform for submillimetric droplets. Moreover, they cannot spatially resolve surface heterogeneities that can contribute to surface fouling. To address these shortcomings, we report on using an atomic force microscopy technique to quantitatively measure the interaction forces between a microdroplet and a surface with piconewton force resolution. We show how our technique can be used to spatially map topographical and chemical heterogeneities with micron resolution.

Springtail-Inspired Superamphiphobic Ordered Nanohoodoo Arrays with Quasi-Doubly Reentrant Structures.

The skin of springtails is well-known for being able to repel water and organic liquids using their hexagonally arranged protrusions with reentrant structures. Here, a method to prepare 100 nm-sized nanohoodoo arrays with quasi-doubly reentrant structures over square centimeters through combining the nanosphere lithography and the template-protected selective reactive ion etching technique is demonstrated. The top size of the nanohoodoos, the intra-nanohoodoo distance, and the height of the nanohoodoos can be readily controlled by the plasma-etching time of the polystyrene (PS) spheres, the size of the PS spheres used, and the reactive ion etching time of silicon. The strong structural control capability allows for the study of the relationship between the nanohoodoo structure and the wetting property. Superamphiphobic nanohoodoo arrays with outstanding water/organic liquid repellent properties are finally obtained. The superamphiphobic and liquid repellent properties endow the nanohoodoo arrays with remarkable self-cleaning performance even using hot water droplets, anti-fogging performance, and the surface-enhanced Raman scattering sensitivity improvement by enriching the analyte molecules on the nanohoodoo arrays. Overall, the simple and massive production of the superamphiphobic nanohoodoo structures will push their practical application processes in diverse fields where wettability and liquid repellency need to be carefully engineered.

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.

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).

Unveiling the origin of the anti-fogging performance of plasma-coated glass: Role of the structure and the chemistry of siloxane precursors

The application of (super)hydrophilic coatings in sectors of activity concerned by fogging, such as the food industry, the architectural sector, and medicine has attracted enormous attention over the past few years. However, despite this interest, most of the coating deposition techniques used thus far are not suitable for large-scale production because of their multistep nature. In this regard, the use of atmospheric pressure dielectric barrier discharges (AP-DBD) operated under a controlled N2/N2O atmosphere offers a promising alternative to conventional deposition techniques for the fabrication of anti-fogging coatings. Using this one-step coating approach, four siloxane precursors with different structures and different number of Si―H and Si−CH3 groups; namely, 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), 1,1,3,3-tetramethyldisiloxane (TMDSO), and hexamethyldisiloxane (HMDSO) were deposited on glass samples. Because of their extreme wetting behavior (WCA < 5°), TMCTS-coated glasses featured an excellent anti-fogging performance, in contrast to OMCTS-, TMDSO-, and HMDSO-coated glasses which were not fogging-resistant (WCA ≈ 80°)). Coupled with hydrophilic functionalities, such as CO, O CO, and SiOH groups, the relatively high surface roughness of TMCTS-coated glass, compared with that of OMCTS-, TMDSO-, or HMDSO-coated glass, accounted for its superior visual characteristics when exposed to water vapor at 80 °C. These results allow us to confidently conclude that the cyclic structure of TMCTS in conjunction with the high reactivity of the Si-H bonds is responsible for the observed anti-fogging effect.

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.

Role of the surface chemistry of plasma polymer layers on their long‐term antifogging behavior

AbstractThe long‐term antifogging capability of plasma coatings obtained from a hydrophilic precursor, such as 2‐(dimethylamino)ethyl methacrylate or acrylic acid, and a hydrophobic monomer, 1H,1H,2H‐perfluoro‐1‐decene (HDFD), deposited on polycarbonate is studied for two different agings. These films, when freshly prepared, show simultaneous hydrophilicity/oleophobicity for HDFD concentrations &lt;50%. They fulfill antifogging criteria: low water contact angle (&lt;20°), high hexadecane contact angle around 70° and preservation of optical transparency after water vapor contact. Depending on their chemical structure, only p‐AA‐co‐HDFD with 20–40% of HDFD retain their antifogging properties after thermal aging, while all of them are altered when dipped in hot water. p‐AA‐co‐HDFD is more efficient than p‐DAME‐co‐HDFD in reducing airborne contamination and improving long‐term antifogging performance.

Beyond microelectronics with 1,3,5,7-tetramethylcyclotetrasiloxane: A promising molecule for anti-fogging coatings

Over the past few years, a growing number of studies have focused on designing coatings for use in applications dealing with the fogging phenomenon such as endoscopes, automobile side view mirrors, and protective goggles. However, because of the long manufacturing times, the implementation on an industrial scale of most of the coating techniques used thus far is still a pending issue. Bearing this in mind, we report on the use of atmospheric pressure dielectric barrier discharges (AP-DBDs) operated in the presence of nitrous oxide (N2O) and 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), as a reliable coating strategy for the one-step fabrication of anti-fogging glass. An increase in either the [N2O]/[TMCTS] ratio or the dissipated power resulted in coatings with such hydrophilic groups on the surface as Si–OH, C–O, and OC–O; and a structure similar to that of SiO2. Because of their “water-loving” characteristics (WCA < 40°), coatings deposited under a [N2O]/[TMCTS] ratio ≥ 30 and a dissipated power ≥ 0.25 W cm−2 conferred a remarkable anti-fogging performance to glass samples when placed over water at 80 °C. After 30 s of exposure to water vapor at 50 °C (ASTM F 659-06), the coated glasses exhibited a light transmittance greater than that of the uncoated glass (90% vs. 55%). These results illustrate how by controlling the dissipated power and the [N2O]/[TMCTS] ratio in the plasma anti-fogging glass can readily be fabricated.

Engineering of Durable Antifog Thin Coatings on Plastic Films by UV-Curing of Proteinoid Prepolymers with PEG-Diacrylate Monomers.

Fog formation on transparent surfaces constitutes a major challenge in several optical applications, such as plastic packaging, lenses, mirrors, and windshields. To overcome this problem, we prepared and characterized durable antifog thin coatings on plastic films such as polyethylene terephthalate (PET). Proteinoids are biocompatible random polymers made of α-amino acids by thermal step-growth polymerization. Proteinoid prepolymers were prepared by adding activated double bonds to proteinoids via the Michael addition reaction. A series of thin antifog cross-linked coatings were prepared by spreading on PET films with a Mayer rod various mixtures of the proteinoid prepolymers, polyethylene glycol diacrylate, and a photoinitiator, followed by UV-curing of the dried coatings. The antifog properties of the coatings were determined by the contact angle, roughness, haze, and gloss measurements, as well as hot and cold fog tests, to examine the optical properties of the films under fog formation conditions. Mechanical properties such as adhesion, robustness, and abrasion resistance of the antifog coatings were examined by tape, knife-scratch, and sandpaper abrasion tests. The effect of coating composition, wettability, and roughness on the antifog properties of the coated PET films was elucidated. The formula was optimized, and the corresponding UV-cured antifog cross-linked thin coating exhibited transparency with good adhesion and excellent durable antifog performance.

Study of Oil Dewetting Ability of Superhydrophilic and Underwater Superoleophobic Surfaces from Air to Water for High-Effective Self-Cleaning Surface Designing.

The superhydrophilic self-cleaning surface can perfectly deal with oil pollution, which cannot be realized by the superhydrophobic surface. This research is designed to study the mechanism of wetting behavior of superhydrophilic coating with different function groups and guide to design a stable self-cleaning surface. We prepare several hydrophilic coatings including nonionic, ionic, and zwitterionic coatings to investigate their self-cleaning performance underwater when they have been polluted by oil in the dry state. The chemical composition, surface roughness, static and dynamic wettability, underwater oil adhesive force, and swelling degree of the coatings are studied to explore their oil dewetting mechanism. The results indicate that the wettability of the coating to water and oil is the key factor to determine the self-cleaning performance. The smooth 3-sulfopropyl methacrylate potassium salt (SA) anionic coating shows the best self-cleaning performance even when polluted by heavy crude oil in the dry state in air. It is also found that in the dry state, the rough hydrophilic anionic surface will lock up the oil in the structures and then lose its self-cleaning ability underwater, whereas the oil droplet can detach from the smooth coating surface quickly. Meanwhile, the superhydrophilic and underwater superoleophobic SA anionic surfaces also exhibit excellent anti-fogging and oil-water separation performance.

Excellent self-healing and antifogging coatings based on polyvinyl alcohol/hydrolyzed poly(styrene-co-maleic anhydride)

To develop low-cost and high-performance self-healing antifogging coatings, polyvinyl alcohol/hydrolyzed poly(styrene-co-maleic anhydride) (PVA/H-PSMA) coatings were prepared from a mixed solution of polyvinyl alcohol (PVA) and hydrolyzed poly(styrene-co-maleic anhydride) (H-PSMA) via spin coating and annealing. The microstructure, antifogging behavior, and self-healing ability were investigated. High transparency and low surface roughness were observed when the PVA/H-PSMA film was coated on glass slides. The PVA/H-PSMA coatings showed excellent antifogging performance in a warm, humid environment. The coatings also performed well when transferred from a refrigerator to room temperature. The antifogging coatings showed desirable water resistance due to strong chemical bonding between PVA and H-PSMA, as well as excellent self-healing ability due to hydrogen bonding self-assembly in the PVA/H-PSMA structure. The coatings still exhibited excellent antifogging effects after 20 scratching-repairing cycles, illustrating their potential use in practical applications.

Fabrication and application of superhydrophilic antifog surface by sol-gel method

Herein, we report a single step and a one pot by using spin coating method for the preparation of optically transparent, superhydrophilic, antifogging composite surface. The wettability performance and also antifogging properties of these surfaces were investigated depending on silica particles content in composite solution. It was also examined the effects of production technique changes on wettability and antifogging characteristics of these surfaces having 20% wt silica particles content. The apparent water contact angle of transparent surfaces were found to vary between 65° and 4° depending on the silica content, polymer type and production technique. Superhydropilic surface (WCA = 4°) displayed a good antifogging performance and light permeability behavior. It was also observed that antifogging behavior kept showing when water contact angle is lower than 15°. However, antifogging properties disappeared when water contact angle is higher than 25°. These results were showed that one step-one pot reaction have a better results than two step reactions depending on silica particles adding time.

Enhancing antifogging/frost-resisting performances of amphiphilic coatings via cationic, zwitterionic or anionic polyelectrolytes

Polymeric antifogging and frost-resisting coatings were successfully prepared, but the performances of amphiphilic coatings containing different kinds of cationic, zwitterionic and anionic polyelectrolytes are still needed to investigate systematically. In this work, antifogging/frost-resisting coatings with high transparence were developed from amphiphilic copolymers of cationic, zwitterionic or anionic poly(2-(dimethylamino)ethyl methacrylate (DMAEMA)-co-2,2,2-trifluoroethyl methacrylate (FMA))-b-polyelectrolytes with a small amount of ethylene glycol dimethacrylate via UV-curing. Studies on the prepared amphiphilic coatings suggested that the cationic and zwitterionic coatings exhibited superior antifogging properties, whereas the anionic polyelectrolyte-based coating demonstrated a better frost-resisting behavior. Water molecule activities in the amphiphilic coatings were analyzed by differential scanning calorimetry, Raman spectroscopy and low field nuclear magnetic resonance. It was found that the cationic and zwitterionic coatings containing 2-(methacryloyloxy)-ethyltrimethyl ammonium chloride and sulfobetaine methacrylate, respectively, exhibited stronger polymer-water interactions dominated by strong hydrogen bonds, and held more nonfreezable water content with shorter transverse spin-spin relaxation time T2 than the anionic coating containing 3-sulfopropyl methacrylate potassium (SPMA). Electrostatic interactions between anionic SPMA and DMAEMA units in the copolymer could weaken the polymer-water interaction, leading to a compromise in the antifogging performance and an enhancement of frost-resisting ability of the coating. The results of this study would be applicable for exploring the advanced antifogging/frost-resisting coatings.

Non-UV activated superhydrophilicity of patterned Fe-doped TiO2 film for anti-fogging and photocatalysis

Fe3+-doped TiO2 films with the pattern surface were fabricated onto glass substrates by a facial photosensitive sol–gel method. The patterned TiO2 film has anatase crystallites and a micro- and nanometer-scale hill-to-valley hierarchical surface structure. The hydrophilicities of all TiO2 films stored in the dark for a long time were evaluated by measuring the water contact angle (CA) without being illuminated by ultraviolet (UV) light in advance. The results demonstrated that water droplets could quickly spread onto the surface of the patterned TiO2 film, resulting in a low CA. The patterned TiO2 film with the lowest period of 2 μm showed the lowest CA of 2° within 3 s. This indicated that the patterned TiO2 film had the good superhydrophilicity without any UV activation. The wetting behavior of the patterned TiO2 film followed the Cassie impregnating wetting regime, and the dynamic to hydrophilic state was attributed to the capillary effect. The patterned TiO2 film also had the non-UV induced anti-fogging performance and exhibited a good photocatalytic activity to decompose methyl orange pollutant.