Damage Tolerance of Superhydrophobic Coatings with Binary Cooperative Cells for Water Harvesting.

Multifunction superhydrophobic coatings that facilitate water harvesting are attractive for addressing the daunting water crisis, yet, they are caught in a double bind when their durability is considered, as durable coatings will require both tough micro-textures to survive concentrated stress and high-surface-energy chemistry to form chemical bonds within the matrix. To date, a universal bulk-phase coating that combines multifunctionality, ultra-durability, and fabrication feasibility remains challenging. Here, a binary cooperative cell design is reported that can solve the contradiction between the multifunctionality and durability requirements of superhydrophobic coatings. In this strategy, mechanochemically tailored cells with releasable nanoseeds are infused in the common matrix, which serves both as a versatile chemical bridge to achieve strong bonds within the coating building blocks, and as an instantaneous self-repairing generator to improve durability. Such a strategy significantly boosted the wear resistance and outdoor stability of the coatings by over 30-100 and 18 folds, respectively, compared with conventional coatings. The coating is applied to the sustainable application, i.e., enhancing the water collection efficiency by at least 1000% even after harsh abrasion. The strategy will broaden the vision in handling the dilemma properties among functional coatings and promote the application of superhydrophobic coatings in extreme environments.

Transparent anti-fingerprint glass surfaces: comprehensive insights into theory, design, and prospects.

With the advancement of information technology, touch-operated devices such as smartphones, tablets, and computers have become ubiquitous, reshaping our interaction with technology. Transparent surfaces, pivotal in the display industry, architecture, and household appliances, are prone to contamination from fingerprints, grease, and dust. Such contaminants compromise the cleanliness, aesthetic appeal, hygiene of the glass, and the overall user visual experience. As a result, fingerprint prevention has gained prominence in related research domains. This article delves into the primary characteristics of fingerprints and elucidates the fundamental mechanisms and components behind their formation. We then explore the essential properties, classifications, and theoretical foundations of anti-fingerprint surfaces. The paper concludes with a comprehensive review of recent advancements and challenges in transparent superlyophobic fingerprint-resistant surfaces, projecting future trajectories for transparent fingerprint-resistant glass surfaces.

Ultra-durable superhydrophobic cellular coatings.

Developing versatile, scalable, and durable coatings that resist the accretion of matters (liquid, vapor, and solid phases) in various operating environments is important to industrial applications, yet has proven challenging. Here, we report a cellular coating that imparts liquid-repellence, vapor-imperviousness, and solid-shedding capabilities without the need for complicated structures and fabrication processes. The key lies in designing basic cells consisting of rigid microshells and releasable nanoseeds, which together serve as a rigid shield and a bridge that chemically bonds with matrix and substrate. The durability and strong resistance to accretion of different matters of our cellular coating are evidenced by strong anti-abrasion, enhanced anti-corrosion against saltwater over 1000 h, and maintaining dry in complicated phase change conditions. The cells can be impregnated into diverse matrixes for facile mass production through scalable spraying. Our strategy provides a generic design blueprint for engineering ultra-durable coatings for a wide range of applications.

Correction: Double cross-linked transparent superhydrophilic coating capable of anti-fogging even after abrasion and boiling.

[This corrects the article DOI: 10.1039/D3RA03113F.].

Double cross-linked transparent superhydrophilic coating capable of anti-fogging even after abrasion and boiling.

The commercial application of surfaces with superhydrophilic (SHPL) properties is well known as an efficient strategy to address problems such as anti-fogging, anti-frosting, and anti-biological contamination. However, current SHPL coatings are limited by their poor water and abrasion resistances. Thus, herein, to solve these problems active glass was employed as a substrate, and a stable and transparent SHPL solution was prepared via the spraying process. Aqueous polyacrylic resin (PAA), SiO2 nanoparticles (NPs), tetraethyl orthosilicate (TEOS), and sodium allyl sulfonate (SDS) were utilized as the four main components of the PAA-TEOS-SiO2 coating. The durability properties including anti-abrasion, resistance to water, and contact component loss were investigated via the Taber abrasion test, boiling water immersion test, and anti-fogging test, respectively. Furthermore, the structure, composition, and wettability of the coating before and after the friction and water immersion tests were compared via water contact angle (WCA) measurements. Furthermore, the effect of the type of resin on the properties of the coating was investigated. The surface morphology of the blended water-based polyacrylic acid (PAA) resin was uniform and flat and its adhesion to the substrate was the highest (4.21 MPa). Considering the durability and optical properties of the coating, the optimal blend was 3 wt% PAA resin, which exhibited a transmittance of 90%. When the content of TEOS, which enhanced the crosslinking in the coating, was increased to 2 wt%, the results showed that the SHPL coating maintained good anti-friction, boiling resistance, and anti-fogging properties under the conditions of 300 cycle Taber friction with 250 g load and soaking in hot water at 100 °C for 1 h. In particular, the excellent durability of strong acid and alkali resistance, heat resistance, and long-term aging resistance will facilitate the commercial viability and expand the application of SHPL coating in various research fields.

3D Monolayer Silanation of Porous Structure Facilitating Multi-Phase Pollutants Removal.

Activated carbon (AC) is widely used to removing hazardous pollutants from air and water, owing to its exceptional adsorption properties. However, the high affinity of water molecules with the surface oxygen-containing functional groups can adversely affect the adsorption performance of AC. In this study, a facile and efficient method is presented for fabrication of hydrophobic AC through surface monolayer silanation. Compared to initial AC, the hydrophobic AC improves the water contact angle from 29.7° to 123.5° while maintaining high specific surface area and enhances the removal capacity of multi-phase pollutants (emulsified oil and toluene). Additionally, the hydrophobic AC exhibits excellent adsorption capability to harmful algal bloom species (Chlorella) (97.56%) and algal organic matter (AOM) (96.23%) owing to electrostatic interactions and surface hydrophobicity. The study demonstrates that this method of surface monolayer silanation can effectively weaken the effect of water molecules on AC adsorption capacity, which has significant potential for practical use in air and water purification, as well as in the control of harmful algal blooms.

Ultra-purification of heavy metals and robustness of calcium silicate hydrate (C-S-H) nanocomposites.

For the sake of remediating the contamination of heavy metal ions (HMs) that poses high risk to the global environment, a novel inorganic nanocomposite with excellent robustness, calcium silicate hydrate (C-S-H), is synthesized at extremely low cost yet presents rapid adsorption rate and superhigh adsorption capacity. High concentrations of Cu(Ⅱ), Cd(Ⅱ), Co(Ⅱ) and Cr(Ⅲ) in wastewater can be purified to ultra-low level (∼0.008 mg L-1) within 60 min at low C-S-H dosage, the concentration and pH indexes of which meet the standard for direct discharge in China. The adsorption processes are spontaneous, following the Langmuir adsorption isotherm model, and its kinetics conforms to pseudo-second order model. Meanwhile, C-S-H presents excellent anti-interference performance during the ultra-purification of HMs when exposed to the acid environments, solutions with various HMs as well as high salinity. The ultra-purification of HMs and robustness of C-S-H is realized through multiple mechanisms based on adsorption, involving hydrolysis of HMs, electrostatic interaction, chemical microprecipitation, surface complexation and interlayer complexation, among which interlayer complexation is dominant. All these verify the robust performance and broad applicability of C-S-H to complex aqueous systems.

Transparent superhydrophilic composite coating with anti-fogging and self-cleaning properties.

Superhydrophilic coatings have incomparable advantages in anti-fogging and self-cleaning but are limited to poor abrasion resistance and water resistance. Consequently, the research on the contradiction between hydrophilicity and water resistance, as well as abrasion resistance and visible transmittance, has become a focus of superhydrophilic coatings. Herein, we design a ceramic-polymer superhydrophilic composite coating with a high density, strong cross-linking structure, and smooth surface. Because of its static water contact angle (WCA = 3.2°) and short water spreading time (ST = 1878 ms), the transparent composite coating exhibits anti-fogging performance. Meanwhile, it exhibits anti-fogging durability even after 400 Taber abrasion cycles under a 250 g load or immersion in boiling water for 30 min. Furthermore, the result of self-cleaning characterization and theoretical analysis demonstrate that the low surface roughness endows the composite coating with excellent self-cleaning properties. The composite coating can effectively scavenge oil and dust pollution on its surface in a humid environment. Thus, the developed composite coating in this work is potential in the anti-fogging and self-cleaning fields.

Solvent-Responsive Magnetic Beads for Accurate Detection of SARS-CoV-2.

Although numerous approaches were proposed for the nucleic acid (NA)-based SARS-CoV-2 detection, the nonideal NA desorption efficiency of conventional magnetic beads (MBs) limits their widespread application. In this study, we developed solvent-responsive MBs (called responsive MBs), which, in the presence of buffers, modulated the absorption and desorption capacities of NA by flipping the surface -COO-. Relative to other commercial MBs, responsive MBs exhibited similar absorption profiles and markedly enhanced desorption profiles. When applied for NA detection of complex samples, responsive MBs exhibited better performance of RNA detection than DNA, with obvious advantages in sensitivity. Specifically, the RNA and DNA desorption rates of commercial MBs were ∼85 and 82.5%, while those of responsive MBs were nearly 94 and 93.5%, respectively. Furthermore, responsive MBs exhibited remarkable extraction ability in a wide range of tissues and better performance of RNA extraction than DNA. When applied for SARS-CoV-2 detection, the responsive MBs along with the simulated digital RT-LAMP (a previously established apparatus) further improved detection efficiency, yielding a precise quantitative detection as low as 25 copies and an ultimate sensibility detection of 5 copies/mL. It was also successfully employed in numerous NA-based technologies such as polymerase chain reaction (PCR), sequencing, and so on.

Waterborne superamphiphobic coatings with network structure for enhancing mechanical durability.

Superamphiphobic coatings may significantly change the wettability of a substrate, and so are attractive for applications in aero/marine engineering, biotechnology, and heat transfer. However, the coatings are caught in a double bind when their durability is considered, as they are vulnerable to mechanical abrasion. Meanwhile, the wide use of organic solvents for preparing the coatings generates environmental pollution. Here, we present a waterborne superamphiphobic coating through one-step spraying that repels a wide range of liquids. By tailoring the repellence of the nano-silica to waterborne resin, a network structure is constructed to protect the embedded nano-silica from damage. Thus, the coatings are durable against 725 cycles of friction tester abrasion under a load of 250 g, showing a significant improvement in the mechanical durability by 3-25 times. Moreover, our coating also shows excellent comprehensive durability, including resistance to oil-flow erosion, falling sand impact, chemical attack, thermal treatment, etc. This strategy can be introduced to various waterborne resins, demonstrating its universality, and may offer a new insight to design sustainable superamphiphobic coatings for long-term practical applications.

Design of Continuous Transport of the Droplet by the Contact-Boiling Regime.

Joule-heat-driven directional transport of liquid droplets has comprehensive engineering applications in various water and thermal management, cooling systems, and self-cleaning. Generally, the driving force for the transport of liquid droplets was always observed at an extremely high Leidenfrost temperature, which limits the potential application between liquid boiling and Leidenfrost points. In this work, we design a new strategy to directionally drive the transport of droplets by blockading the vapor cushion at a temperature much lower than the Leidenfrost point. On the surface of the microhole arrays, we observed the continuous rebound behavior of ethanol droplets at Ts = 110 °C. Employing the thermal multiphase lattice Boltzmann model, the continuous rebound behavior was reproduced, verifying that the driving force was provided by the blockaded vapor pressure in microholes. By cooperating with the Laplace pressure difference, we directionally transport ethanol and water droplets on the horizontal asymmetrical concentric microridge surface. The horizontal velocity of water is 11.25 cm/s at Ts = 180 °C, similar to the traditional ratchets at the Leidenfrost point. The design of microtextures enriches the fundamental understanding of how to drive droplets at far below the Leidenfrost point and pushes the application in nongravity-driven self-cleaning and cooling systems.

Recyclable Superhydrophobic, Antimoisture-Activated Carbon Pellets for Air and Water Purification.

Activated carbon (AC) is a low-cost, highly porous material with large internal surface areas. It is highly efficient in absorbing moisture and a variety of chemical pollutants. Therefore, it has been widely used in air and water purification. However, the strong affinity to moisture often dominates, thus limiting AC's adsorption capacity of other pollutants in a humid environment and reducing its overall lifetime. In the study, superhydrophobic and anti-moisture AC (SA-AC) pellets are fabricated through one-step modification of commercially available AC with a solution consisting of superhydrophobic silica nanoparticles. The SA-AC pellets exhibit excellent water repellency with a static water contact angle reaching 160.3°. More importantly, they are moisture-resistant and air-permeable. Therefore, they preferably adsorb organic gases at humid conditions. The absorbed organic vapor can be released when they are transferred back to the dry atmosphere, for example, releasing approximately 35% of absorbed ethanol. The recoverability significantly reduces energy requirement compared to calcination or conventional extraction. Great adsorption capacity of organic dyes such as methylene blue, removal of oil-in-water microemulsions, and recyclability of SA-AC pellets are demonstrated. The morphology of the microporous structures of the SA-AC pellets is characterized against processing conditions, surface functional groups, and hierarchical structures tailored by the deposition of low-surface energy silica nanoparticles. The resulting micro-/sub-micropores on the pellet surface promote droplet condensation, thus displaying greater damp-proof performance than those treated by traditional modification. The study here presents a promising alternative for the efficient purification on large-scale air/water treatment.

Durable superamphiphobic coatings from one-step electrostatic dusting.

Superamphiphobic coatings are fabricated via electrostatic dusting using modified silica particles and polymethyl methacrylate resin particles on conductive substrates (metal and conductive glass). The obtained translucent superamphiphobic coatings show excellent durability and chemical robustness even after exposure to strong acids and bases. Importantly, the coatings maintain hydrophobicity even after 100 cycles of abrasion testing and 1000 cycles of finger wiping. In addition, the fabricated coatings are superoleophobic after finger wiping, tape peeling and oil immersion. This facile strategy may provide researchers in related fields with new avenues for improving powder coatings in practical applications.

Enhancing the Robustness of Superhydrophobic Coatings via the Addition of Sulfide.

Micro/nano hierarchical structures with special wettability impart a wide spectrum of unique properties to the superhydrophobic surfaces that are applicable in different potential fields. Therefore, it is necessary to develop advanced superhydrophobic materials with excellent wear-resistance properties. In this study, PDMS-based robust superhydrophobic coatings, which used MoS2 or WS2 as a solid lubricant, PDMS as a binder, and SiO2 as a filler, were prepared on glass substrate by the one-step air spaying method. Lamellar MoS2 and WS2 with high crystallinity had intrinsic hydrophobic properties. The MoS2@SiO2-PDMS (MSP) and WS2@SiO2-PDMS (WSP) coatings with very rough textures showed good water-repellent behavior with water contact angles of 167.8 and 166.2°, respectively. The results demonstrated that the addition of microsized MoS2 or WS2 could easily format micro/nano second-level hierarchical structures, thus realizing the superhydrophobic properties. The friction coefficient decreased gradually with the increasing in MoS2 or WS2. A 4:1 ratio of SiO2 to MoS2/WS2 could cause the samples to preserve their superhydrophobic properties even after 100 cycles on the abraser. As a result, superhydrophobic coatings with excellent wear resistance will be good candidates for water-repellent surfaces to meet practical emerging needs in industry applications.

Beetle-like droplet-jumping superamphiphobic coatings for enhancing fog collection of sheet arrays.

Fog collection from atmosphere is an effective way to solve the water resource crisis in arid or semi-arid areas. Inspired by the bumpy surface of the desert beetle, this work provides a beetle-like superamphiphobic coating by adding silicon carbide particles to nano-SiO2 superamphiphobic coating in proportion, which shows excellent superamphiphobic performance, high nucleation rate, efficient drop removal efficiency and recommendable fog collection effect. In this work, drop removal is facilitated by the collisions of water droplets between the array sheets, and when the as-prepared samples are placed parallel to each other and with a space of ∼2 mm, the jumping drop collisions between two sample surfaces could promote the departure of droplets, and the water collection rate of the collision surface increased by ∼217% compared to that of the non-collision surface, which provides a new idea to promote water droplet removal. This work findings are instrumental in water collection and have wide application prospects in desalination, heat transfer, anti-fogging and other fields.

Large-scale fabrication of waterborne superamphiphobic coatings for flexible applications.

In recent years, there have been great achievements in superhydrophobic coatings. However, there are still some barriers restricting superhydrophobic coatings in practical applications, such as widely used organic solvents and poor oleophobicity. In this study, we proposed a method for fabricating absolutely waterborne superamphiphobic coatings in two steps. Firstly, we synthesized the waterborne SiO2 sol using methyltriethoxysilane, and then the SiO2 sol was modified in an aqueous system with a fluorocarbon surfactant. The results showed that the coating had contact angles of 160°, 153° and 150° and sliding angles of 1°, 4.7° and 6.3° with respect to water, soybean oil and hexadecane. Moreover, the coating could withstand 300 °C heating and immersion in various corrosive solutions for several hours. Furthermore, it is worth mentioning that the waterborne coating showed excellent performances in antifouling, self-cleaning, and damp-proof fields.

Frosting Behavior of Superhydrophobic Nanoarrays under Ultralow Temperature.

Retarding and preventing frost formation at ultralow temperature has an increasing importance due to a wide range of applications of ultralow fluids in aerospace and industrial facilities. Recent efforts for developing antifrosting surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces. Whether the antifrosting performance of the superhydrophobic surface is still effective under ultralow temperature has not been elucidated clearly. Here, we investigated the frosting behavior of fabricated superhydrophobic ZnO nanoarrays under different temperature and different environment. The surface showed excellent performance in anticondensation and antifrosting when the surface temperature was approximately -20 °C. Although the frosting event inevitably occurs on all surfaces when the temperature is decreased from -50 to -150 °C, the frost accumulation on the superhydrophobic surfaces is always less than that on the untreated surfaces. Interestingly, the frost layer detaches from the surface within a short time and keeps the surface dry in the very beginning of the defrosting process. Further, there is no frost formation on the surface at -20 °C during 10 min testing when blowing compressed air and spraying methanol together or spraying methanol individually. It can reduce the height of the frost layer and increases the density when spraying methanol at -150 °C. Furthermore, the frost crystals on the top surface can been blown away due to the low adhesion of ice or frost. It provides a basic idea for solving the frosting problem under ultralow temperature while combined with other defrosting methods.

Sprayable superhydrophobic nano-chains coating with continuous self-jumping of dew and melting frost.

Spontaneous movement of condensed matter provides a new insight to efficiently improve condensation heat transfer on superhydrophobic surface. However, very few reports have shown the jumping behaviors on the sprayable superhydrophobic coatings. Here, we developed a sprayable silica nano-porous coating assembled by fluorinated nano-chains to survey the condensates' dynamics. The dewdrops were continuously removed by self- and/or trigger-propelling motion due to abundant nano-pores from random multilayer stacking of nano-chains. In comparison, the dewdrops just could be slipped under the gravity effect on lack of nano-pores coatings stacked by silica nano-spheres and nano-aggregates. More interestingly, the spontaneous jumping effect also occurred on micro-scale frost crystals under the defrosting process on nano-chains coating surfaces. Different from self-jumping of dewdrops motion, the propelling force of frost crystals were provided by a sudden increase of the pressure under the frost crystal.

Detection of Avian H7N9 Influenza A Viruses in the Yangtze Delta Region of China During Early H7N9 Outbreaks.

Since the first H7N9 human case in Shanghai, February 19, 2013, the emerging avian-origin H7N9 influenza A virus has become an epizootic virus in China, posing a potential pandemic threat to public health. From April 2 to April 28, 2013, some 422 oral-pharyngeal and cloacal swabs were collected from birds and environmental surfaces at five live poultry markets (LPMs) and 13 backyard poultry farms (BPFs) across three cities, Wuxi, Suzhou, and Nanjing, in the Yangtze Delta region. In total 22 isolates were recovered, and six were subtyped as H7N9, nine as H9N2, four as H7N9/H9N2, and three unsubtyped influenza A viruses. Genomic sequences showed that the HA and NA genes of the H7N9 viruses were similar to those of the H7N9 human isolates, as well as other avian-origin H7N9 isolates in the region, but the PB1, PA, NP, and MP genes of the sequenced viruses were more diverse. Among the four H7N9/H9N2 mixed infections, three were from LPM, whereas the other one was from the ducks at one BPF, which were H7N9 negative in serologic analyses. A survey of the bird trading records of the LPMs and BPFs indicates that trading was a likely route for virus transmission across these regions. Our results suggested that better biosecurity and more effective vaccination should be implemented in backyard farms, in addition to biosecurity management in LPMs.

Lattice Boltzmann modeling of droplet condensation on superhydrophobic nanoarrays.

Droplet nucleation and growth on superhydrophobic nanoarrays is simulated by employing a multiphase, multicomponent lattice Boltzmann (LB) model. Three typical preferential nucleation modes of condensate droplets are observed through LB simulations with various geometrical parameters of nanoarrays, which are found to influence the wetting properties of nanostructured surfaces significantly. The droplets nucleated at the top of posts (top nucleation) or in the upside interpost space of nanoarrays (side nucleation) will generate a nonwetting Cassie state, while the ones nucleated at the bottom corners between the posts of nanoarrays (bottom nucleation) produce a wetting Wenzel state. The simulated time evolutions of droplet pressures at different locations are analyzed, which offers insight into the underlying physics governing the motion of droplets growing from different nucleation modes. It is demonstrated that the nanostructures with taller posts and a high ratio of post height to interpost space (H/S) are beneficial to produce the top- and side-nucleation modes. The simulated wetting states of condensate droplets on the nanostructures, having various geometrical configurations, compare reasonably well with experimental observations. The established relationship between the geometrical parameters of nanoarrays and the preferential nucleation modes of condensate droplets provides guidance for the design of nanoarrays with desirable anticondensation superhydrophobic properties.