Liquid Repellency Research Articles

Chemical Etching, Thermally Driven Combination Strategy to Fabricate Superhydrophobic Fe-Based Amorphous Coatings with Excellent Anticorrosion Property: Based on Hydroxylation Effect.

Fe-based amorphous coatings are ideal materials for surface protection due to their outstanding mechanical properties and corrosion resistance. However, coating defects are inevitably formed during the preparation of coatings by thermal spray technology, which seriously affects the corrosion performance. Inspired by bionics, conceiving superhydrophobic surfaces with liquid barrier properties has become a new idea for the corrosion protection of metal surfaces. In this work, based on surface hydroxylation, we designed a superhydrophobic Fe-based amorphous coating with corrosion resistance by chemical etching combined with a thermally driven preparation strategy. The obtained superhydrophobic coatings exhibit liquid repellency (contact angle >150°) and excellent corrosion resistance (corrosion current density and passive current density reduced by 3 orders of magnitude). The results revealed that the superhydrophobic behavior stems from the construction of hydroxyl-induced surface micro-/nanomultilevel aggregates (cluster structures). The hydrophobic agent layer deposited on the surface of cluster aggregates and the nanoparticle elements that constitute the clusters dominate the corrosion resistance of the coating. This work provides an effective guide to the design of high-corrosion-resistant Fe-based amorphous alloy coatings and promotes their engineering applications.

Mechanical Stability of Liquid‐Infused Surfaces Based on Mussel‐Inspired Polydopamine Chemistry

AbstractLiquid‐infused surfaces exhibit remarkable repellency properties toward water, oils, and complex fluids and are widely applied to maintain clean, operational, and high‐performing surfaces in various fields, from the biomedical sector to marine infrastructure. Polydopamine (PDA) forms an ideal base layer for the development of such coatings as it adheres to virtually any substrate and can be chemically modified via amino‐containing molecules to adjust the surface properties. Here, strategies are explored to increase the mechanical stability of such coatings by i) incorporating imidazole during film formation to increase crosslinking, and ii) formation of a composite consisting of the organic PDA and an inorganic siliceous porous coating by infiltration of a preformed porous silica layer with PDA. Both strategies exhibit improved resistance to tangential shear assessed by a sandpaper abrasion test and to dynamic impact assessed by a sand trickle test. These improved mechanical properties are successfully transferred to liquid‐infused surfaces created from such modified PDA base layers. The most durable coatings retain efficient liquid repellency after 25 abrasion cycles, indicating improved resilience in real‐world applications.

Robust and durable self-lubricated surface by facile fabrication for anti-icing/deicing

Undesired ice accumulation can lead to serious negative impacts on daily life and equipment safety. Slippery liquid-infused surfaces (SLISs) have been widely studied for their low ice adhesion strength (τice). However, the lack of durability, weak robustness, and complex preparation process hinder the application of SLISs. In this work, robust oil-infused porous surface (RIPS) was obtained by a facile one-step method, which used epoxy resin (E44) as a substrate and contained fumed silica and silicone oil. The RIPS-6 displays outstanding anti-icing/deicing ability, superior liquid repellency, good self-cleaning performance, and excellent mechanical robustness. At −5 °C, the water droplet remained unfrozen after 7200 s. τice was only 6.9 kPa at −20 °C and remained below 15 kPa during 10 icing cycles. Furthermore, the mixture of E44 and fumed silica enhanced the mechanical properties including the hardness (4 H) and abrasion resistance of RIPS-6. The icephobicity can be remained (τice < 40 kPa) even after 150 cycles of sandpaper abrasion at 2.5 kPa. The anti-icing and deicing coating with excellent mechanical stability and durability significantly improves the practical application possibility of the coating in harsh environments.

A bio-inspired slippery coating with mechanochemical robustness for anti-ice and anti-corrosion

Slippery coatings with outstanding liquid repellency and drag reduction are essential for energy saving and economic society. However, their long-term durability is still limited by weak slippery capacity and mechanochemical stability. Here, a manta ray skin inspired coating (MSC) via straightforward spraying method is developed. The rational design of the hemispherical structures composed of silicon-containing materials endows a transparent and robust slippery surface with hardness of 0.94 GPa and an extremely low friction coefficient of 0.076. The MSC can be applied on diverse substrates with strong adhesion and exhibits an outstanding resistance to liquid with a wide range of surface tension and viscosity up to 1,499 mPa·s. The coating maintains transparency and sustains liquid repellency after 1,000 abrasion cycles under 250 g loads or 32 days treatment at extreme high/low temperatures. In addition, the distinct anti-icing/de-icing properties and good anti-corrosion performance along with a facile spraying process provide MSC a tremendous potential for achieving industrial applications.

Potential of Beluntas Leaf Extract (Pluchea indica L) as a basic ingredient for Making Liquid Anti-Mosquito Repellent

The herbaceous Belugas leaves (Pluchea indica L.) belong to the Asteraceae family and are commonly utilized as food and hedges. They typically grow wild. Alkaloids, saponins, flavonoids, tannins, triterpenes, and steroids are among the substances found in belugas leaves that may have insecticidal properties. The purpose of this study is to use the leaf extract of Beluntas (Pluchea indica L.) as a foundational component for liquid mosquito repellant. In order to produce a thick extract of beluntas leaves, this study used an extraction process that involved evaporating 96% ethanol solvent. Several concentrations of the thick extract were diluted, including 15%, 25%, 35%, 45%, and 55%. The collected data, which was mosquito mortality, was subjected to a One-Way Anova test with a significance level of p = 0.000 <0.05, and then the Duncan test. The findings demonstrated that the number of mosquitoes that perished varied depending on the concentration fluctuations of beluntas leaf extract, with the highest concentration of beluntas leaf extract killing mosquitoes at a rate of 55% and a mosquito mortality percentage of 98.4%.

Omniphobic coatings based on functional acrylic polymer

Omniphobic coatings were prepared on flat surfaces using a functional acrylic polymer and common micron sized inorganic particles by a simple spray application technique. This coating comprises of a blend of functional acrylic polysiloxane polymer and liquid epoxy resin as a primer base coat followed by spray application of a mixture of organosilanes and inorganic microparticles. The microparticles are fillers commonly used in the paint and coating industry. The resulting surface has the desired surface energy and surface morphology to enable liquid repellency with contact angles of ∼150° for water and 142° for diiodomethane with a roll off angle of <5°. Scanning Electron Microscopic (SEM) and Atomic Force Microscopy (AFM) analysis were performed to study surface morphology. This coating can be applied on large areas and can be cured under ambient conditions. This omniphobic coating is robust, free of nanoparticles and can be used for potential applications in the field of self-cleaning coatings, anti-microbial coatings, and easy cleaning coatings.

Low-Temperature Atmospheric Pressure Plasma Treatment in the Polymer and Textile Industry

Plasma treatment is a popular technique for modifying the surface properties of a wide range of materials (plastics, glass, metals, and wood) prior to gluing, bonding, and painting. Physical and chemical properties are altered to improve or confer specific characteristics of materials in an environmentally friendly manner. Low-temperature atmospheric pressure plasma (LTAPP) is an innovative technology offering surface modification of heat-sensitive materials using an easy one-step procedure. LTAPP treatment is routinely employed for the surface modification of polymer-based materials to enhance their adhesion, printability, and surface sterility. This article demonstrates that LTAPP plasma treatment also opens up new opportunities for the textile industry. It has a positive effect on fabric wettability, liquid repellency, dyeability, UV protection factor, shrink resistance, flame retardancy, and so on. This article describes selected applications of LTAPP in polymer science and the textile industry, highlighting current research trends in material science.

Robust omniphobic ceramic hollow fibre membrane with leaf-like copper oxide hierarchical structure by membrane distillation

Omniphobic membranes have recently shown promising performance in water desalination using MD due to their ability to repel all liquid drop types and keep the membrane surface dry. This study successfully modified the surface of robust hydrophilic mullite-stainless steel hollow fibre membranes (M-SS HFMs) to omniphobic properties. The omniphobic layer was achieved through surface grafting with copper oxide (CuO) rough layer by a hydrothermal technique at different hydrothermal reaction times of 1, 2, 3, 4 and 5 h, followed by fluorination step using 1H,1H,2H,2H-perfluorode-cyltriethoxysilane (C8, 97 %). Next, the omniphobic membranes were characterized in terms of membrane morphology, roughness, mechanical strength, pore size/distribution, liquid entry pressure, contact angle and fouling accumulation. The prepared omniphobic M-SS HFMs were also tested through the DCMD system at 80 °C using a feed solution containing 35 g/L of NaCl and 10 mg/L of humic acid as a foulant agent. The results indicated that M-SS HFMs subjected to a 4 h hydrothermal reaction time, resulting in a leaf-like surface structure, exhibited superior characteristics compared to other omniphobic HFMs reported in the literature that used titania (SiO2), zinc oxide (ZnO), and cobalt (Co3O4) as roughing material. These superior features included higher roughness of 0.798 μm, liquid entry pressure of 5.40 bar, and enhanced liquid repellence and contact angles towards DI water of 167°, olive oil of 152°, and ethanol of 145°. Additionally, the M-SS HFMs at 4 h hydrothermal demonstrated remarkable performance in terms of rejection performance (99.99 %) and vapour flux stability of about 29 kg/m2.h in DCMD operations, surpassing the performance of omniphobic HFMs fabricated using mullite-ball clay, mullite-kaolinite, and alumina (Al2O3). Notably, no fouling/wetting on the membrane surface and elements leaching was observed throughout the MD operation. These findings highlight the potential of this omniphobic HFM for seawater desalination using DCMD systems, even in the presence of organic contaminants.

Mechanically robust liquid-embedded coating with anti-icing/deicing durability

The slippery liquid-infused porous surface has been concerned for their excellent icephobicity. However, unavoidable lubricant consumption can result in the failure of anti-icing/deicing properties. Traditional coatings cannot escape the choice between anti-icing/deicing property and mechanical performance. This paper reports mechanically robust liquid-embedded coating (MRLC) with anti-icing/deicing durability. The MRLC is prepared by a facile one-step method via adding silica and silicone oil in the process of co-curing PDMS and epoxy resin. The prepared MRLC-5–5–80 have excellent anti-fouling, self-cleaning, anti-icing/deicing and anti-frost properties in high humidity and low temperature environment. This surface remained free of liquid residue and ice within 30 min in supercooled water droplet impact test. In addition, this coating exhibited a low τice (5.48 kPa) and excellent durability. The PDMS polymer and fumed silica serve as oil storage reservoir for the coating to ensure durability, and the anti-icing/deicing durability can be restored by self-replenishing and external-replenishing. More importantly, the coating guarantees anti-icing/deicing durability while possessing excellent mechanical robustness. The liquid repellency and anti-icing/deicing performance still prevailed after various mechanical damages. This method opens the door for production of durable and mechanically robust for various anti-icing/deicing practical applications.

Owens–Wendt Characterization of Femtosecond-Laser-Textured Hydrophobic Aluminum Surfaces

The eligibility of applying the Owens–Wendt approach to determining the free surface energy of liquid-repellent aluminum surfaces, with micro- and nanotextures formed by a femtosecond laser, was considered. This approach has been shown to be applicable using two essential parameters that can be derived from the graphs. The first is related to the fraction of the contact area between the liquid and the solid surface in the Cassie state. The second is related to the degree of intrinsic polarity of the surface material or the applied organic modifier. The presented interpretation was used to compare the liquid repellency of the obtained textures. A microtexture with a period of 60 μm and a groove width of 45 μm has been shown to be the most liquid repellent. Among the modifiers, 1H,1H,2H,2H-perfluoroctyltriethoxysilane was the most effective, and stearic acid was only slightly inferior, but promising in terms of cost and environmental friendliness. It was shown that spontaneous hydrophobization provided a contact angle with water up to 159°, but the stability of such textures was inferior to the considered modifiers.

Synergistic Antibacterial Surface with Liquid Repellency and Enhanced Photothermal Bactericidal Activity.

The presence of microorganisms on biomedical devices and food packaging surfaces poses an important threat to human health. Superhydrophobic surfaces, a powerful tool to combat pathogenic bacterial adhesion, are threatened by their poor robustness. As a supplement, photothermal bactericidal surfaces may be expected to kill adhered bacteria. Using copper mesh as a mask, we prepared a superhydrophobic surface with a homogeneous conical array. The surface shows synergistic antibacterial properties, including a superhydrophobic character against bacterial adhesion and photothermal bactericidal activity. As a result of the excellent liquid repellency, the surface could highly repel the adherence of bacteria after immersing in a bacterial suspension for 10 s (95%) and 1 h (57%). Photothermal graphene can easily eliminate most adhered bacteria during the subsequent treatment of near-infrared (NIR) radiation. After a self-cleaning wash, the deactivated bacteria were easily rinsed off the surface. Furthermore, this antibacterial surface exhibited an approximately 99.9% resisted bacterial adhesion rate regardless of planar and various uneven surfaces. The results offer promising advancement of an antibacterial surface combining both adhesion resistance and photothermal bactericidal activity in fighting microbial infections.

Design of Fluoro-Free Surfaces Super-Repellent to Low-Surface-Tension Liquids.

Super-liquid-repellent surfaces feature high liquid contact angles and low sliding angles find key applications in anti-fouling and self-cleaning. While repellency for water is easily achieved with hydrocarbon functionalities, repellency for many low-surface-tension liquids (down to 30 mNm-1 ) still requires perfluoroalkyls (a persistent environmental pollutant and bioaccumulation hazard). Here, the scalable room-temperature synthesis of stochastic nanoparticle surfaces with fluoro-free moieties is investigated. Silicone (dimethyl and monomethyl) and hydrocarbon surface chemistries are benchmarked against perfluoroalkyls, assessed using model low-surface-tension liquids (ethanol-water mixtures). It is discovered that both hydrocarbon- and dimethyl-silicone-based functionalization can achieve super-liquid-repellency down to 40-41 mNm-1 and 32-33 mNm-1 , respectively (vs27-32 mNm-1 for perfluoroalkyls). The dimethyl silicone variant demonstrates superior fluoro-free liquid repellency likely due to its denser dimethyl molecular configuration. It is shown that perfluoroalkyls are not necessary for many real-world scenarios requiring super-liquid-repellency. Effective super-repellency of different surface chemistries against different liquids can be adequately predicted using empirically verified phase diagrams. These findings encourage a liquid-centric design, i.e., tailoring surfaces for target liquid properties. Herein, key guidelines are provided for achieving functional yet sustainably designed super-liquid-repellency.

Molecularly Capped Omniphobic Polydimethylsiloxane Brushes with Ultra-Fast Contact Line Dynamics.

Droplet friction is common and significant in any field where liquids interact with solid surfaces. This study explores the molecular capping of surface-tethered, liquid-like polydimethylsiloxane (PDMS) brushes and its substantial effect on droplet friction and liquid repellency. By exchanging polymer chain terminal silanol groups for methyls using a single-step vapor phase reaction, the contact line relaxation time is decreased by three orders of magnitude-from seconds to milliseconds. This leads to a substantial reduction in the static and kinetic friction of both high- and low-surface tension fluids. Vertical droplet oscillatory imaging confirms the ultra-fast contact line dynamics of capped PDMS brushes, which is corroborated by live contact angle monitoring during fluid flow. This study proposes that truly omniphobic surfaces should not only have very small contact angle hysteresis, but their contact line relaxation time should be significantly shorter than the timescale of their useful application, i.e., a Deborah number less than unity. Capped PDMS brushes that meet these criteria demonstrate complete suppression of the coffee ring effect, excellent anti-fouling behavior, directional droplet transport, increased water harvesting performance, and transparency retention following the evaporation of non-Newtonian fluids.

Inkjet printing of pixel arrays: droplet formation and pattern uniformity of a non-aqueous ink with tunable viscosity

Inkjet printing is a rapid and material-efficient process that is suitable for the fabrication of large-area microarrays from a range of optoelectronic materials. In order to ensure stable droplet formation and a uniform print image with very smooth surfaces, however, the ink properties such as viscosity and surface tension have to be precisely adjusted. In this study, a non-aqueous ink formulation is proposed whose viscosity can be conveniently adjusted by controlling the mixing ratio of propylene carbonate (PC) as the low-viscosity solvent and propylene glycol (PG) as the high-viscosity solvent. Using a combination of advanced imaging techniques, we show that raising the PG content from 20% to 80% increased the viscosity of the ink from 3.36 cP to 26.70 cP, resulting in stable droplet formation and a more evenly printed image. At a spacing of 5 dots/pixel, the roughness value decreased dramatically, from root mean square (RMS): 11.28 (20% PG) to RMS: 0.09 (80% PG). Alternatively, more homogeneous patterns (albeit with a rough surface) were also produced with the low-viscosity ink (20% PG) when a conditioned substrate with low surface energy and selective liquid repellency was used. With this we present a simple but effective strategy to improve droplet formation while obtaining highly uniform pixel arrays. The knowledge gained will be particularly useful for inkjet printing of pixel-patterned color conversion layers in devices such as organic light-emitting diodes (LEDs) and micro-LED displays.

Preparation of PLA-based SMS nonwoven composites and its applications in protective apparel

The global COVID-19 pandemic has triggered a huge demand for the protective nonwovens. However, the main raw material of nonwovens comes from petroleum, and the massive consumption of petroleum-based polymers brings great pressure to ecosystem. Therefore, it is significant to develop biodegradable protective barrier products. In this work, a polylactic-based composite (a tri-layer nonwovens composed of spunbond, meltblown and spunbond, SMS) was prepared and applied for protective apparel. The surface morphology and chemical changes of the fibers were characterized and analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive spectroscopy (EDS). The liquid contact angle and permeability, breathability and moisture permeability, frictional charge and mechanical strength of the samples were evaluated and compared. The samples degradability was also recorded. The results demonstrate that the optimum formula for anti-fouling treatment on SMS is F-30. The treated fabric possesses superior liquid repellency and anti-permeability, with contact angles of water and alcohol at 128° and 115° respectively, while the alcohol repellent grade reaches level 7. The treated sample has less strength loss but exhibits favorable breathability, moisture permeability and anti-static properties, which can meet the requirements of protective apparels. After fluorine resin coating, the composite still provide excellent degradation performance, and the weight loss rate reaches more than 80% after 10 days water degradation. These results provide new insights for the application of PLA-based SMS in biodegradable protective apparel.

Fluorine-Free Super-Liquid-Repellent Surfaces: Pushing the Limits of PDMS

Methods for fabricating super-liquid-repellent surfaces have typically relied on perfluoroalkyl substances. However, growing concerns about the environmental and health effects of perfluorinated compounds have caused increased interest in fluorine-free alternatives. Polydimethylsiloxane (PDMS) is most promising. In contrast to fluorinated surfaces, PDMS-coated surfaces showed only superhydrophobicity. This raises the question whether the poor liquid repellency is caused by PDMS interacting with the probe liquid or whether it results from inappropriate surface morphology. Here, we demonstrate that a well-designed two-tier structure consisting of silicon dioxide nanoparticles combined with surface-tethered PDMS chains allows super-liquid-repellency toward a range of low surface tension liquids. Drops of water-ethanol solutions with surface tensions as low as 31.0 mN m-1 easily roll and bounce off optimized surface structures. Friction force measurements demonstrate excellent surface homogeneity and easy mobility of drops. Our work shows that fluorine-free super-liquid-repellent surfaces can be achieved using scalable fabrication methods and environmentally friendly surface functionalization.

Evaluating the Performance of Per- and Polyfluoroalkyl Substance Finishes on Upholstery Fabrics

Per- and polyfluoroalkyl substances are widely used to provide a hydrophobic and oleophobic barrier in some fabric finishing. Per- and polyfluoroalkyl substances are a class of harmful chemicals that persist in the environment and our bodies. For indoor upholstery, these finishes are used to prevent staining. In this study, we examined the effectiveness of certain per- and polyfluoroalkyl substance finishes on commercial indoor fabrics for liquid repellency and stain performance. Three fabrics, each with an unfinished control, a dip finish, and a foam finish, were tested with coffee and oil-based salad dressing stains, two dwell times, two stain application procedures, and three abrasion conditions. Oil stain severity was affected by fabric type, finish, dwell time, and application procedure, but not abrasion. For water-based coffee stains, only fabric type had an effect. Droplet contact angle tests were also performed, revealing water and oil repellency is quickly lost with abrasion. Of the six per- and polyfluoroalkyl substance-finished fabrics tested, five showed small improvements in stain performance over unfinished fabrics; however, the performance differences between fabric types were much larger than the benefits from finishes. For oil stains, per- and polyfluoroalkyl substance finishes help in ideal conditions when the finish is unabraded, stains are set gently on the fabric, and stains are cleaned quickly. Our results suggest that the use of per- and polyfluoroalkyl substances on indoor furniture can be considerably reduced through intentional material selection to achieve better stain performance in lieu of per- and polyfluoroalkyl substance finishes.

Alteration In Kidney Biomarkers After Inhalation Exposure of Transfluthrin Based Liquid Mosquito Repellent In Rattus norvegicus (Berkenhout)

The use of liquid mosquito repellent is one of the most significant and persistent sources of indoor air pollution in houses. Human deals with the world's deadliest vector-borne disease, malaria, as well as the fastest-growing vector disease in the world right now, dengue, which is also spread by mosquitoes. Insect-borne diseases are a major public health concern. Transfluthrin, d-allethrin, bioallethrin, dimefluthrin, pralethrin, dphenothrin, cypenothrin, or esbiothrin are some of the more common insecticides contained in mosquito repellents. All of them are pyrethroid derivatives. After 7, 15, 30, 45 and 60 days of exposure to liquid insect repellent in the treated group as compared to the control group, Rattus norvegicus (Berkenhout) showed substantial increases in kidney biomarkers Urea, Creatinine, Uric acid and Blood Urea Nitrogen (BUN). The current study shows that different kidney biomarkers are adversely affected by liquid mosquito repellent. The main component of this repellent is lethal and dangerous for both people and the environment. Keywords : Repellent, Insecticides, Transfluthrin, Pyrethroid

Achieving Extreme Pressure Resistance to Liquids on a Super-Omniphobic Surface with Armored Reentrants.

Static repellency and pressure resistance toliquidsare essential for high-performance super-omniphobic surfaces. However, these two merits appear mutually exclusive in conventional designs because of their conflicting structural demands: Static liquid repellency necessitates minimal solid-liquid contact, which in turn inevitably undercuts the surface's ability to resist liquid invasion exerted by the elevated pressure. Here, inspired by the Springtail, these two merits can be simultaneously realized by structuring surfaces at two size scales, with a micrometric reentrant structure providing static liquid repellency and a nanometric reentrant structure providing pressure resistance, which dexterously avoids the dilemma of their structural conflicts. The nanometric reentrants are densely packed on the micrometric ones, serving as "armor" that prevents liquids invasion by generating multilevel energy barriers, thus naming the surface as the armored reentrants (AR) surface. The AR surface could repel liquids with verylow surface tensions, such as silicone oil (21mNm-1), and simultaneously resist great pressure from the liquids, exemplified by enduring the impact of low-surface-tension liquids under a high weber number (>400), the highest-pressure resistance ever reported. With its scalable fabrication and enhanced performance, our design could extend the application scope of liquid-repellent surfaces toward ultimateindustrial settings.

Advanced polymer processing technologies for micro‐ and nanostructured surfaces: A review

AbstractFunctional surfaces with attractive properties, such as superhydrophobicity and omniphobicity often rely on the synergy between intrinsic material properties and dual scale micro‐ and nano‐hierarchical structures for achieving desired wettability. Historically, engineered liquid repellent surfaces have attracted a great deal of interest from academia and industry due to their broad application prospects. Hence, for several years, there have been significant scientific efforts by researchers exploring state of the art manufacturing technologies that are efficient and yet cost effective to produce functional liquid repellent surfaces at an industrial scale. This technical review summarizes the various advanced and state of the art polymer processing technologies employed to fabricate the micro‐ and nanostructured polymer surfaces, with a special focus given to superhydrophobic and omniphobic applications. Here, we discuss the merits and limitations of each fabrication methods available for micro‐ and nanostructuring of polymer‐based surfaces. In addition, an attempt has been made to provide insight into the relationship between geometry of micro/nanostructures (size and shape) and intrinsic wettability on liquid repellency. A special section has been devoted to feature and document all commercialization efforts, including various commercially available products that were developed in the past decade. Finally, outlook and the development trend in the polymer micro‐ and nanostructured surfaces are highlighted to lead future research.