Tailoring the Hydrophilicity for Delayed Condensation Frosting in Antifogging Coatings

Ultrathin, Stimuli-Responsive, Antimicrobial, Self-Cleaning, Reusable, and Biodegradable, Micro/Nanofibrous Electrospun Mat as an Efficient Face Mask Filter for Airborne Disease Prevention

A multifunctional, electrospun, ultrathin face mask is desirable for preventing disease spread while ensuring breathability. However, balancing ultrathin construction with antimicrobial efficacy is challenging. Here, we fabricated an ultrathin micro/nanofibrous electrospun matrix, consisting of three biodegradable polymer layers, for high antibacterial efficiency, breathability, and biodegradability. The outer layer, with an average thickness of 9.01 ± 3.1 μm, is composed of polycaprolactone (PCL), silver nitrate (AgNO3), and β-cyclodextrin (β-CD). The middle layer, with a thickness of 4.61 ± 1.4 μm, comprises poly(vinyl alcohol) (PVA) and multiwalled carbon nanotubes (MWCNT) as a conductive layer. The inner layer, with a thickness of 5.12 ± 1.4 μm, contains PVA, carboxymethyl chitosan (CMC), and cellulose nanofibrils (CNFs) as a superabsorbent layer, supported by medical gauze. With a total thickness of ∼300 μm, the mask provides antibacterial efficacy, self-cleaning, reusability, mechanical stability, and biodegradability. This design advances filtering face masks, offering a solution to combat contagious diseases while minimizing environmental impact.

Biomimetic Superwetting Phenomena for Antifogging Surfaces

Fog formation on transparent windows compromises the visual clarity of these surfaces and brings hidden safety dangers, which underscores the importance of research into antifogging coatings. In recent years, biomimetic superwetting coatings have garnered significant attention as a key technology for addressing fogging issues. This review outlines the latest advancements in the design and fabrication of superwetting antifogging materials. Initially, the antifogging mechanism of superwetting surfaces was introduced briefly. Subsequently, contemporary developments in superhydrophobic antifogging surfaces inspired by organisms and superhydrophilic antifogging coatings with a variety of material systems have been emphatically discussed. The amphiphilic and heat-assisted antifogging surfaces, including photothermal and electrothermal surfaces, were also overviewed. Finally, a summary and future perspective on antifogging coating from its functionality, durability, and availability were discussed.

Bioinspired Antireflective and Antifogging Surface for Highly Efficient and Stable Inverted Solar Cells

Photovoltaic devices are essentially solar energy collectors that convert incident photons into charge carriers. However, light reflection losses and external factors (e.g., fog) can lead to an inefficient utilization of incident photons. Therefore, the development of antifogging surface materials that can efficiently reduce reflection is a critical issue in the upgradation of photovoltaic devices. Herein, inspired by the wing scale structures of butterfly Trogonoptera brookiana, an antireflective and antifogging surface (BRFS) was prepared by a method combining biotemplate and sol-gel. Remarkably, the BRFS possesses a relatively large surface roughness and exhibits superhydrophilic property (static water contact angle of 0°), which can quickly split fog droplet film within 6.6 s to realize the antifogging effect. In addition, the final transmittance of BRFS is as high as 90.25%. Furthermore, as an application demonstration, BRFS was applied to the surface of the reverse organic solar cells. Without compromising the inherent performance of the panels, the BRFS enhances the electrical performance of the inverted solar panels by 18%. This work provides a simple and effective strategy for designing surfaces with superior antifogging and antireflective properties and offers significant potential value for the practical application of photoelectric devices.

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.

Chemically and geometrically programmable photoreactive polymers for transformational humidity-sensitive full-color devices

Humidity-sensitive structural color has emerged as a promising technology due to its numerous advantages that include fast response, intuitiveness, stand-alone capability, non-toxicity, as well as resistance to thermal and chemical stresses. Despite immense technological advancements, these structural colors lack the ability to present independent multiple images through transformation. Herein, we present an approach to address this constraint by introducing a chemically and geometrically programmable photoreactive polymer which allows preparation of transformational humidity-sensitive full-color devices. Utilizing azido-grafted carboxymethyl cellulose (CMC-N3) allows adjustments in swelling properties based on the grafting ratio (Γ) of azido groups upon UV-induced crosslinking. Also, the distinctive photo-curability of the polymer enables precise geometric control to achieve vivid colors in combination with disordered plasmonic cavities. Our work culminates in the development of an advanced anti-counterfeiting multiplexer capable of displaying different full-color images with variation in humidity levels. The showcased color displays signify pivotal breakthroughs in tunable optical technologies, illustrating how chemical modifications in hydrogels provides additional degrees of freedom in the design of advanced optical devices.

Radiation polymerization for the preparation of universal coatings: remarkable anti-fogging and frost-resisting performance

Hydrophilic anti-fogging coatings have attracted considerable attention due to their ease of preparation and excellent fog resistance. In this study, a hydrophilic anti-fogging coating based on the random copolymer p(AA-co-SAS) was prepared using acrylic acid (AA) and sodium allylsulfonate (SAS) as monomers through radiation polymerization. The introduction of SAS successfully transformed the random copolymer from a gel state into a film-forming polymer solution. The presence of AA structural units in p(AA-co-SAS) improved the film-forming properties of the polymer solution. Additionally, there was a positive correlation between the proportion of SAS structural units in the random copolymer and the scratch hardness and wetting properties of the coating. After coating polycarbonate (PC) sheets, the surface hydrophilicity was significantly enhanced, with the contact angle of PC-AA10/SAS5 decreasing from 100.1° to 18.8° within 50 seconds. The outstanding wetting properties endowed the coating with exceptional anti-fogging and frost-resisting performance. It exhibited optimal transparency under both testing conditions and demonstrated good stability during cyclic testing. Tape adhesion tests indicated that the adhesion between the coating and PC reached a 5B level. When AA10/SAS5 was applied to PET film, glass, and PMMA goggles, all samples showed excellent anti-fog performance. Even after being naturally placed for one year under ambient conditions, the PMMA goggles still maintained good performance in the anti-fog and frost resistance tests. The remarkable comprehensive properties of the polymer coating based on p(AA-co-SAS) suggest enormous potential applications in industries such as packaging, healthcare, and optical equipment.

Development of seaweed-derived polysaccharide/cellulose nanocrystal-based antifogging labels loaded with alizarin for monitoring aquatic products' freshness

Intelligent freshness indicator labels have attracted great interest for their massive potential in monitoring the freshness of aquatic products over the years. However, there is still a challenge where fogging on the labels during dramatic temperature changes affects the reading of freshness. At the same time, the freshness indicator labels need high mechanical strength to resist collision damage during transportation and storage. Herein, an antifogging freshness indicator label was developed based on seaweed extracts and alizarin. Firstly, soluble polysaccharides and insoluble components were extracted from Gelidium amansii, and cellulose nanocrystal (CNC) was further prepared from the insoluble components by sulfuric acid hydrolysis. Subsequently, a polysaccharide-based film was fabricated using soluble polysaccharides as the matrix materials and CNC as the reinforcement agent. Antifogging experiments showed that the hydrophilic composite films presented good antifogging performance. After loading with alizarin, the composite indicator label exhibited both antifogging and freshness-indicating properties for the salmon sample. The work provided a new idea for developing freshness indicator labels suitable for low-temperature transportation and storage.

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.

Recent advances in prevailing antifogging surfaces: structures, materials, durability, and beyond

In past decades, antifogging surfaces have drawn more and more attention owing to their promising and wide applications such as in aerospace, traffic transportation, optical devices, the food industry, and medical and other fields. Therefore, the potential hazards caused by fogging need to be solved urgently. At present, the up-and-coming antifogging surfaces have been developing swiftly, and can effectively achieve antifogging effects primarily by preventing fog formation and rapid defogging. This review analyzes and summarizes current progress in antifogging surfaces. Firstly, some bionic and typical antifogging structures are described in detail. Then, the antifogging materials explored thus far, mainly focusing on substrates and coatings, are extensively introduced. After that, the solutions for improving the durability of antifogging surfaces are explicitly classified in four aspects. Finally, the remaining big challenges and future development trends of the ascendant antifogging surfaces are also presented.