Water drop-surface interactions as the basis for the design of anti-fogging surfaces: Theory, practice, and applications trends

A Fe3+-Doped TiO2 Superhydrophilic Coating with Transparent and Long-Lasting Antifogging Properties Constructed Based on Nanostructured Antireflective and Capillary Anchoring Effects

Superhydrophilic surfaces have attracted great interest in antifogging applications. However, balancing long-lasting superhydrophilicity and high transparency on antifogging surfaces remains a serious problem to be solved. The objective of this work is to prepare superhydrophilic coatings with transparent and long-lasting antifogging properties. In the design, a three-step method was used to obtain the target coatings: (1) magnetron sputtering deposition of a TiN film to provide high intensity, (2) anodic oxidation of the TiN film to obtain TiO2 nanoparticles intended for nanostructured antireflective and capillary structures, and (3) the sol-gel method for the preparation of Fe3+-doped TiO2 coatings using spin-coating in order to achieve superhydrophilicity. The nanostructures, due to their subwavelength dimensions, not only provide high transparency but also recoverable superhydrophilicity owing to the presence of a capillary anchoring effect that prevents the coating from dissolving and peeling off after soaking. The doping of Fe3+ broadened the photoresponse range and maintained the long-lasting superhydrophilicity. Tests showed that the 2 mol % Fe3+-doped TiO2 coating with nanostructures exhibited the highest transparency, longest-lasting superhydrophilicity, and antifogging properties. Furthermore, the coating provided excellent self-cleaning properties, as well as mechanical and chemical stability.

Si-doped carbonized polymer dot as robust hydrophilic coating using for high efficiency antifogging

Hydrophilic coating can prevent surface from fogging but its application is limited by low mechanical performance. In this study, a hydrophilic coating was prepared by crosslinking the Si-doped carbonized polymer dot (Si-CPD) with 3-glycidyloxypropyltrimethoxysilane (GPTMS) and ethylene oxide (EO). The hydrophilic coating can be used as robust hydrophilic anti-fogging coating. The Si-CPD derived from ethylene diamine tetraacetic acid (EDTA) and aminopropyl oligosiloxanes (APOS) was successfully prepared via one-step hydrothermal method. Then, a resin solution was prepared by mixing Si-CPD, GPTMS and EO. Epoxy group of GPTMS and EO can react with amino group of Si-CPD. Finally, a composite coating with antifogging function can be obtained by simple heating curing. Due to the introduction of hydroxyl which derived from EO, the coating shows excellent antifogging performance. Meanwhile, the presence of inorganic component endows the coating with outstanding mechanical performance. The coating has great potential in related applications, such as optical lenses, mirrors and other transparency substrates.

Amphiphilic Nanoscale Antifog Coatings: Improved Chemical Robustness by Continuous Assembly of Polymers

Designing effective antifog coatings poses challenges in resisting physical and chemical damage, with persistent susceptibility to decomposition in aggressive environments. As their robustness is dictated by physicochemical structural features, precise control through unique fabrication strategies is crucial. To address this challenge, a novel method for crafting nanoscale antifog films with simultaneous directional growth and cross-linking is presented, utilizing solid-state continuous assembly of polymers via ring-opening metathesis polymerization (ssCAPROMP). A new amphiphilic copolymer (specified as macrocross-linker) is designed by incorporating polydimethylsiloxane, poly(2-(methacryloyloxy)ethyl) trimethylammonium chloride (PMETAC), and polymerizable norbornene (NB) pendant groups, allowing ssCAPROMP to produce antifog films under ambient conditions. This novel approach results in distinctive surface and molecular characteristics. Adjusting water-absorption and nanoscale assembly parameters produced ultra-thin (≤100 nm) antifog films with enhanced durability, particularly against strong acidic and alkaline environments, surpassing commercial antifog glasses. Thickness loss analysis against external disturbances further validated the stable surface-tethered chemistries introduced through ssCAPROMP, even with the incorporation of minimal content of cross-linkable NB moieties (5 mol%). Additionally, a potential zwitter-wettability mechanism elucidates antifog observations. This work establishes a unique avenue for exploring nanoengineered antifog coatings through facile and robust surface chemistries.

Engineering of Silane-Pyrrolidone Nano/Microparticles and Anti-Fogging Thin Coatings

Polyvinylpyrrolidone (PVP) exhibits remarkable qualities; owing to the strong affinity for water of its pyrrolidone group, which enhances compatibility with aqueous systems, it is effective for stabilizing, binding, or carrying food, drugs, and cosmetics. However, coating the surface of polymeric films with PVP is not practical, as the coatings dissolve easily in water and ethanol. Poly(silane-pyrrolidone) nano/microparticles were prepared by combining addition polymerization of methacryloxypropyltriethoxysilane and N-vinylpyrrolidone, followed by step-growth Stöber polymerization of the formed silane-pyrrolidone monomer. The silane-pyrrolidone monomeric solution was spread on oxidized polyethylene films with a Mayer rod and polymerized to form siloxane (Si-O-Si) self-cross-linked durable anti-fog thin coatings with pyrrolidone groups exposed on the outer surface. The coatings exhibited similar wetting properties to PVP with significantly greater stability. The particles and coatings were characterized by microscopy, contact angle measurements, and spectroscopy, and tested using hot fog. Excellent anti-fogging activity was found.

Engineered Sustainable Omniphobic Coatings to Control Liquid Spreading on Food-Contact Materials

The adhesion of sticky liquid foods to a contacting surface can cause many technical challenges. The food manufacturing sector is confronted with many critical issues that can be overcome with long-lasting and highly nonwettable coatings. Nanoengineered biomimetic surfaces with distinct wettability and tunable interfaces have elicited increasing interest for their potential use in addressing a broad variety of scientific and technological applications, such as antifogging, anti-icing, antifouling, antiadhesion, and anticorrosion. Although a large number of nature-inspired surfaces have emerged, food-safe nonwetted surfaces are still in their infancy, and numerous structural design aspects remain unexplored. This Review summarizes the latest scientific research regarding the key principles, fabrication methods, and applications of three important categories of nonwettable surfaces: superhydrophobic, liquid-infused slippery, and re-entrant structured surfaces. The Review is particularly focused on new insights into the antiwetting mechanisms of these nanopatterned structures and discovering efficient platform methodologies to guide their rational design when in contact with food materials. A detailed description of the current opportunities, challenges, and future scale-up possibilities of these nanoengineered surfaces in the food industry is also provided.

Thiol-ene click reaction as an effective tool for the synthesis of PEG-functionalized alkoxysilanes-precursors of anti-fog coatings

The article presents a very simple method of glass modification to obtain the anti-fog effect. Silanes containing two types of functional groups, namely a hydrophilic and polar polyether group and an alkoxysilyl group (to bond with the surface of the modified material) were synthesized in thiol-ene reactions. The hydrothiolation reactions of polyethers containing a C=C terminal bond with mercaptoalkoxysilane proceeded efficiently, yielding quantitatively appropriate products under mild reaction conditions. This method enabled the synthesis of a series of alkoxysilanes functionalized with polyethers, differing in structure. The group of obtained derivatives was characterized by 1H, 13C, 29Si NMR, and FT-IR analyses, and then used to prepare coatings on glass using the sol-gel method. The coated glass surfaces exhibited transparency, superhydrophilic or hydrophilic properties, anti-fog and anti-frost performance.

Hydrophilic and Hydrophobic Surfaces: Features of Interaction with Liquid Drops

The processes of interaction of liquid droplets with solid surfaces have become of interest to many researchers. The achievements of world science should be used for the development of technologies for spray cooling, metal hardening, inkjet printing, anti-icing surfaces, fire extinguishing, fuel spraying, etc. Collisions of drops with surfaces significantly affect the conditions and characteristics of heat transfer. One of the main areas of research into the interaction of drops with solid surfaces is the modification of the latter. Changes in the hydrophilic and hydrophobic properties of surfaces give the materials various functional properties-increased heat transfer, resistance to corrosion and biofouling, anti-icing, etc. This review paper describes methods for obtaining hydrophilic and hydrophobic surfaces. The features of the interaction of liquid droplets with such surfaces are considered. The existing and possible applications of modified surfaces are discussed, as well as topical areas of research.

Silicone Oil-Grafted Low-Hysteresis Water-Repellent Surfaces

Wetting plays a major role in the close interactions between liquids and solid surfaces, which can be tailored by modifying the chemistry as well as the structures of the surfaces' outermost layer. Several methodologies, such as chemical vapor deposition, physical vapor deposition, electroplating, and chemical reactions, among others, have been adopted for the alteration/modification of such interactions suitable for various applications. However, the fabrication of low-contact line-pinning hydrophobic surfaces via simple and easy methods remains an open challenge. In this work, we exploit one-step and multiple-step silicone oil (5-100 cSt) grafting on smooth silicon substrates (although the technique is suitable for other substrates), looking closely at the effect of viscosity as well as the volume and layers (one to five) of oil grafted as a function of the deposition method. Remarkably, the optimization of grafting of silicone oil fabrication results in non-wetting surfaces with extremely low contact angle hysteresis (CAH) below 1° and high contact angles (CAs) of ∼108° after a single grafting step, which is an order of magnitude smaller than the reported values of previous works on silicone oil-grafted surfaces. Moreover, the different droplet-surface interactions and pinning behavior can additionally be tailored to the specific application with CAH ranging from 1 to 20° and sliding angles between 1.5 and 60° (for droplet volumes of 3 μL), depending on the fabrication parameters adopted. In terms of roughness, all the samples (independent of the grafting parameters) showed small changes in the root-mean-square roughness below 20 nm. Lastly, stability analysis of the grafting method reported here under various conditions shows that the coating is quite stable under mechanical vibrations (bath ultrasonication) and in a chemical environment (ultrasonication in a bath of ethanol) but loses its low-pinning characteristics when exposed to saturated steam at T ∼ 99 °C. The findings presented here provide a basis for selecting the most appropriate and suitable method and parameters for silicone oil grafting aimed at low pinning and low hysteresis surfaces for specific applications.

Transparent Composite Films Showing Durable Antifogging and Repeatable Self-Healing Properties Based on an Integral Blend Method

Antifogging coatings for infrastructures and transparent objects have attracted much attention lately from the perspective of safety and visibility. We have developed a one-pot process to fabricate transparent composite films showing long-lasting antifogging and fast repeatable self-healing properties based on an integral blend (IB) method. This method does not require any specific pretreatments of inorganic fillers/particles. Thus, the precursor solutions could be prepared in a single step by simply mixing raw materials, e.g., poly(vinylpyrrolidone) (PVP) having different molecular weights (MWs: 55, 360, and 1300 k), nano-clay particles (NCPs), and amino-terminated organosilane (AOS). In this study, to control the degree of cross-linking between the PVP matrices and NCPs, addition of AOS as a cross-linker to the PVP matrices (weight percentage of AOS to the PVP matrices, α = 0.01-300%) was carefully controlled. Transparency and self-healing abilities/kinetics of the resulting samples were found to be strongly influenced by both the MWs of PVP and α values. Samples spin-coated with the lowest M_W of PVP (55 k) and α values of 0.01-1% gave highly transparent and durable antifogging performance. For example, no fogging was observed for 7 days under >80% relative humidity, and scratches about 30 μm in width could be completely self-healed within a few hours. However, samples with α > 10% gave opaque/grayish films that did not show any self-healing abilities because of an increase in cross-linking of the matrices. The optimized precursor solution was also deposited directly onto the glass slides covered with a transparent porous silica nano-framework (SNF) by a spray-coating method. Due to the formation of the hard and superhydrophilic/hygroscopic SNF with a large surface area, durability of antifogging and self-healing properties of the composite films were moderately improved, compared to those on the flat glass slides.

Robust and Transparent Antifogging Polysilsesquioxane Film Containing a Hydroxy Group

Poly(glycidyloxypropyl)silsesquioxane (PGPS) was successfully synthesized by hydrolysis and polycondensation using the nitrogen flow method. A poly(3-(2,3-dihydroxypropoxypropyl)silsesquioxane) (PSQ-OH) film was prepared via two routes. In route A, PSQ-OH was prepared by the hydrolysis of the epoxy group of PGPS in an aqueous hydrochloric acid (HCl)/tetrahydrofuran solution, affording a diol group; then, PSQ-OH was coated on a glass substrate and heated. The antifogging performance of the PSQ-OH film was evaluated in terms of water uptake (WU) and scratch resistance. The obtained PSQ-OH film exhibited a low WU of 5% and a scratch resistance of 1.6. In route B, PGPS was coated on a glass substrate and immersed in a 0.5 mol/L aqueous sulfuric acid solution for 1-15 h at room temperature, producing a diol group. The solid-state ¹³C nuclear magnetic resonance spectrum indicated that the epoxy group was completely hydrolyzed after immersion for 15 h. The WU of the PSQ-OH film prepared via route B increased from 5 to 19% with the increase in the immersion time and was higher than that of the PSQ-OH film prepared via route A. The PSQ-OH film on a glass substrate retained transparency under water vapor exposure at 60 °C. The PSQ-OH film prepared via route B exhibited a high scratch resistance of 2.7-3.6, similar to that of a poly(3-(2-aminoethylaminopropyl)silsesquioxane) film. The scratch resistance of the PSQ-OH film was 5-7 times higher than that of the poly(vinyl alcohol) film. The PSQ-OH film was uniform with no pinholes and cracks. The PSQ-OH film was transparent and colorless and exhibited a high transmittance of >90% in the wavelength range of 400-800 nm. Overall, the prepared PSQ-OH film exhibits good antifogging, transparency, and mechanical properties.

Effective Antifogging Coating from Hydrophilic/Hydrophobic Polymer Heteronetwork

Fogging on optical devices may severely impair vision, resulting in unacceptable adverse consequences. Hydrophilic coatings can prevent surface fogging by instantly facilitating pseudo-film water condensation but suffer from short antifogging duration due to water film thickening with further condensation. Here, an innovative strategy is reported to achieve longer antifogging duration via thickening the robust bonded hydrophilic/hydrophobic polymer heteronetwork coating to enhance its water absorption capacity. The combination of strong interfacial adhesion and hydrophilic/hydrophobic heteronetwork structure is key to this approach, which avoids interfacial failure and swelling-induced wrinkles under typical fogging conditions. The developed antifogging coating exhibits prolonged antifogging durations over a wide temperature range for repetitious usages. Eyeglasses coated with this coating successfully maintained fog-free vision in two typical scenarios. Besides, the coating recipes developed in this study also have potential as underwater glues as they demonstrate strong adhesions to both glass and polymer substrates in wet conditions.

Self-Cleaning Biomimetic Surfaces-The Effect of Microstructure and Hydrophobicity on Conidia Repellence

Modification of surface structure for the promotion of food safety and health protection is a technology of interest among many industries. With this study, we aimed specifically to develop a tenable solution for the fabrication of self-cleaning biomimetic surface structures for agricultural applications such as post-harvest packing materials and greenhouse cover screens. Phytopathogenic fungi such as Botrytiscinerea are a major concern for agricultural systems. These molds are spread by airborne conidia that contaminate surfaces and infect plants and fresh produce, causing significant losses. The research examined the adhesive role of microstructures of natural and synthetic surfaces and assessed the feasibility of structured biomimetic surfaces to easily wash off fungal conidia. Soft lithography was used to create polydimethylsiloxane (PDMS) replications of Solanum lycopersicum (tomato) and Colocasia esculenta (elephant ear) leaves. Conidia of B. cinerea were applied to natural surfaces for a washing procedure and the ratios between applied and remaining conidia were compared using microscopy imaging. The obtained results confirmed the hypothesis that the dust-repellent C. esculenta leaves have a higher conidia-repellency compared to tomato leaves which are known for their high sensitivities to phytopathogenic molds. This study found that microstructure replication does not mimic conidia repellency found in nature and that conidia repellency is affected by a mix of parameters, including microstructure and hydrophobicity. To examine the effect of hydrophobicity, the study included measurements and analyses of apparent contact angles of natural and synthetic surfaces including activated (hydrophilic) surfaces. No correlation was found between the surface apparent contact angle and conidia repellency ability, demonstrating variation in washing capability correlated to microstructure and hydrophobicity. It was also found that a microscale sub-surface (tomato trichromes) had a high conidia-repelling capability, demonstrating an important role of non-superhydrophobic microstructures.

Treatment of oily wastewaters by highly porous whisker-constructed ceramic membranes: Separation performance and fouling models

Efficient treatment of challenging oily emulsion wastewater can alleviate water pollution to provide more chances for water reuse and resource recovery. Despite their promising application potential, conventional porous ceramic membranes have challenging bottleneck issues such as high cost and insufficient permeance. This study presents a new strategy for highly efficient treatment of not only synthetic but real oily emulsions via unexpensive whisker-constructed ceramic membranes, exhibiting exceptional permeance and less energy input. Compared with common ceramic membranes, such lower-cost mullite membranes with a novel whisker-constructed structure show higher porosity and water permeance, and better surface oleophobicity in water. Treatment performance such as permeate flux and oil rejection was explored for the oily emulsions with different properties under key operating parameters. Furthermore, classical Hermia models were used to reveal membrane fouling mechanism to well understand the microscopic interactions between emulsion droplets and membrane interface. Even for real acidic oily wastewater, such membranes also exhibit high permeance and less energy consumption, outperforming most state-of-the-art ceramic membranes. This work provides a new structure concept of highly permeably whisker-constructed porous ceramic membranes that can efficiently enable more water separation applications.

Coordination-Driven Surface Zwitteration for Antibacterial and Antifog Applications

The enhancement of surface wettability by hydrophilic polymer coatings has been of great interest because it has been used to address several technical challenges such as biofouling and surface fogging. Among the hydrophilic polymers, zwitterionic polymers have been extensively utilized to coat solid surfaces due to their excellent capability to bind water molecules, thereby forming dense hydration layers on the solid surfaces. For these zwitterionic polymers to function appropriately on the solid surfaces, techniques for fixing polymers onto the solid surface with high efficiency are required. Herein, we report a new approach to graft zwitterionic polymers onto solid substrates. The approach is based on the mussel-inspired surface chemistry and metal coordination. It consists of polydopamine coating and the coordination-driven grafting of the zwitterionic polymers. Polydopamine coating enables the versatile surface immobilization of catechols. Zwitterionic polymers are then easily fixed onto the catechol-immobilized surface by metal-mediated crosslinking reactions. Using this approach, nanometer-thick zwitterionic polymer layers that are highly resistant to bacterial adhesion and fog generation could be successfully fabricated on solid substrates in a substrate-independent manner.

Bioinspired adhesive coatings from polyethylenimine and tannic acid complexes exhibiting antifogging, self-cleaning, and antibacterial capabilities

In this work, we develop a simple yet robust method to fabricate a bioinspired adhesive coating based on polyethyleneimine (PEI) and tannic acid (TA) complexes, exhibiting excellent antifogging, self-cleaning, and antibacterial properties. The polyethyleneimine-tannic acid (PEI-TA) complexes coating combined with the bioinspired adhesive property from TA can be effectively and stably coated onto various substrates through a one-step deposition process, and the hydrophilicity of the coated substrates can be significantly enhanced with their water contact angle less than 10°. The bioinspired adhesive coating endows the coated substrates with outstanding antifogging and self-cleaning performance. Moreover, it is found that the PEI-TA coated safety goggles display excellent durability and antifogging capability compared to the commercial antifogging safety goggles and commercial antifogging agents coated safety goggles under 65 ℃ vapor condition for 2 h. Furthermore, the PEI-TA coatings show superior antibacterial activities for Gram-negative Escherichiak coli and Gram-positive Staphylococcus aureus. The antifogging, self-cleaning, and antibacterial coating provides widely potential application prospects in optical and medical devices.

Biomimetic Slippery PDMS Film with Papillae-Like Microstructures for Antifogging and Self-Cleaning

Transparent materials with antifogging and self-cleaning ability are of extreme significance for utilization in outdoor solar cell devices to alleviate the performance loss and maintenance costs. Herein, with inspiration from the anti-wetting surfaces in nature, regular papillae-like microstructure arrays (PMAs) inspired by lotus leaves were designed via a common UV lithography combined with a soft replication. Subsequently, the biomimetic slippery polydimethylsiloxane (PDMS) film (BSPF) inspired by the pitcher plant was fabricated successfully by infusing with hydrophobic liquid lubricant. The resultant surface has hydrophobic surface chemistry, a slippery interface, PMAs structure. The wettability, optical characteristic, antifogging property and self-cleaning ability of the PMAs-based BSPF were characterized experimentally. The film displays excellent optical transmittance, antireflection, antifogging, and self-cleaning properties, which is superior to the flat PDMS film (FPF). Remarkably, an average reflection of ∼11.3% in the FPF was reduced to ∼8.9% of the BSPF. In addition, after gradient spray test for 120 s, the antifogging efficiency was close to 100% for the BSPF surface in comparison with the flat PDMS film (FPF), biomimetic PDMS film (BPF) and flat slippery PDMS film (FSPF) (35%, 70% and 85%). Furthermore, we also discovered that the BSPF surface exhibited a better self-cleaning performance toward a variety of liquids than solid dust.

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.

Recent Progresses of Superhydrophobic Coatings in Different Application Fields: An Overview

With the development of material engineering and coating industries, superhydrophobic coatings with exceptional water repellence have increasingly come into researchers’ horizons. The superhydrophobic coatings with corrosion resistance, self-cleaning, anti-fogging, drag-reduction, anti-icing properties, etc., meet the featured requirements from different application fields. In addition, endowing superhydrophobic coatings with essential performance conformities, such as transparency, UV resistance, anti-reflection, water-penetration resistance, thermal insulation, flame retardancy, etc. plays a remarkable role in broadening their application scope. Various superhydrophobic coatings were fabricated by diverse technologies resulting from the fundamental demands of different fields. Most past reviews, however, provided only limited information, and lacked detailed classification and presentation on the application of superhydrophobic coatings in different sectors. In the current review, we will highlight the recent progresses on superhydrophobic coatings in automobile, marine, aircraft, solar energy and architecture-buildings fields, and discuss the requirement of prominent functionalities and performance conformities in these vital fields. Poor durability of superhydrophobic coating remains a practical challenge that needs to be addressed through real-world application. This review serves as a good reference source and provides insight into the design and optimization of superhydrophobic coatings for different applications.

Chemically Robust Antifog Nanocoating through Multilayer Deposition of Silica Composite Nanofilms

A coating must remain intact to perform its inherent functions on a surface, and often functional organic coatings fail due to deterioration because of their intrinsic vulnerabilities. In this work, we present a biomimetic material based on a glass sponge to provide a robust silica composite nanocoating with an antifog effect. The silica composite nanocoating was constructed with a binary film structure consisting of (1) a Fe(III)-tannic acid (TA) nanofilm for adhesion to coat the substrates and (2) a SiO₂ layer to enhance the durability of the coating. Due to the universal coating property of Fe(III)-TA nanofilms, we demonstrated that the silica composite nanocoating was effective regardless of the substrate. By layer-by-layer assembly of the silica composite, it is possible to precisely control the nanocoating thickness. The superhydrophilic nature of the SiO₂ layer showed an exceptional antifog effect that remained intact against multiple deteriorative conditions, including acid treatment, peroxide degradation, sudden temperature change, severe heat conduction, and oil contamination. In addition, the silica composite nanocoating is scalable for surfaces of different shapes and sizes with the aid of a spray-assisted deposition technique. The bioinspired, multicomposite nanocoating strategy herein contributes to the improvement of organic coatings for uses in applications to tackle current technological problems.

Plasma-immersion ion implantation surface oxidation on a cobalt-chromium alloy for biomedical applications

Co-Cr alloys such as L605 are widely applied for the manufacture of medical devices, including tiny cardiovascular stents. The presence of potentially toxic and allergenic release of Ni, Co, and Cr ions from these devices remains an unsolved concern. Surface modification by oxygen plasma immersion implantation (PIII) could be an excellent technique to create a dense and thin passive oxide layer on a relatively complex shape of a tiny device, such as a stent, thus reducing the potential release of metallic ions. The effect of oxygen PIII was investigated on L605 alloy specimens, from 5 to 50 mTorr gas pressures, and under pulsed bias voltages from -0.1 to -10 kV. The surface chemistry was investigated by x-ray photoelectron spectroscopy, while its morphology and surface energy were evaluated, respectively, by atomic force microscopy and scanning electron microscopy and by a sessile drop static contact angle. Electrochemical characterization was performed by potentiodynamic tests in the saline solution. Mechanical properties of the modified surface layer, specifically film adhesion and hardness (H), were assessed by scratch and nanoindentation tests. Results shown that the oxidized layers were composed of a mixture of Co and Cr oxides and hydroxides and were rich in Co. The corrosion rate was considerably reduced after O PIII, even for treatments using low bias voltage (-0.1 kV) and with consequent low oxygen implantation depth. Moreover, O PIII also improved surface hardness. The oxidized layers were found to have good adhesion and to be scratch resistant.

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.

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.

Micro-/Nanostructured Interface for Liquid Manipulation and Its Applications

Understanding the relationship between liquid manipulation and micro-/nanostructured interfaces has gained much attention due to the wide potential applications in many fields, such as chemical and biomedical assays, environmental protection, industry, and even daily life. Much work has been done to construct various materials with interfacial liquid manipulation abilities, leading to a range of interesting applications. Herein, different fabrication methods from the top-down approach to the bottom-up approach and subsequent surface modifications of micro-/nanostructured interfaces are first introduced. Then, interactions between the surface and liquid, including liquid wetting, liquid transportation, and a number of corresponding models, together with the definition of hydrophilic/hydrophobic, oleophilic/olephobic, the definition and mechanism of superwetting, including superhydrophobicity, superhydrophilicity, and superoleophobicity, are presented. The micro-/nanostructured interface, with major applications in self-cleaning, antifogging, anti-icing, anticorrosion, drag-reduction, oil-water separation, water collection, droplet (micro)array, and surface-directed liquid transport, is summarized, and the mechanisms underlying each application are discussed. Finally, the remaining challenges and future perspectives in this area are included.

Advances in photocatalytic self-cleaning, superhydrophobic and electromagnetic interference shielding textile treatments

The use of nanomaterials in textiles provides many new opportunities and advantages for users and manufacturers; however, it comes with some of its downsides and challenges which need to be understood and overcome for enhancing the applicability of these products. This review article discusses the recent progress in developing self-cleaning and conductive textiles as two of the leading research fields of smart textiles. In particular, different aspects of fabricating nanocoatings for photocatalytic self-cleaning, superhydrophobic and electromagnetic interference (EMI) shielding effect will be brought to light. The theoretical concepts, mechanisms, latest fabrication methods along with their potential applications will be discussed. Moreover, the current drawbacks of these fields will be underlined and some recommendations for future research trajectories in terms of performance, current limitations, sustainability and safety will be proposed. This review article provides a comprehensive review on the state-of-the-art achievements in the field, which will be a valuable reference for researchers and decision makers.

Boronate sol-gel method for one-step fabrication of polyvinyl alcohol hydrogel coatings by simple cast- and dip-coating techniques

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities. A mixture of PVA and DBA in aqueous ethanol is prepared as a coating agent. The long pot life of the mixture allows for the coating of a wide range of materials with hydrogel films by simple cast- and dip-coating techniques. The resultant films show negligible dissolution in water and the intrinsic hydrophilicity of PVA provides the films with functional properties, such as improved antifogging property and resistance to protein and cell fouling. The self-assembling process shows adaptive inclusion properties toward nanoscale materials, such as metal–organic coordination polymers and inorganic nanoparticles, affording composite films. Furthermore, the coating film exhibits a unique secondary functionalization reactivity toward boronic acid-appended fluorescent dyes, through which a variety of materials are converted into fluorescent materials.

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities.

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.