Liquid Repellency Research Articles

Flexibility-Patterned Liquid-Repelling Surfaces

Droplets impacting solid surfaces is ubiquitous in nature and of practical importance in numerous industrial applications. For liquid-repelling applications, rigidity-based asymmetric redistribution and flexibility-based structural oscillation strategies have been proven on artificial surfaces; however, these are limited by strict impacting positioning. Here, we show that the gap between these two strategies can be bridged by a flexibility-patterned design similar to a trampoline park. Such a flexibility-patterned design is realized by three-dimensional projection micro-stereolithography and is shown to enhance liquid repellency in terms of droplet impalement resistance and contact time reduction. This is the first demonstration of the synergistic effect obtained by a hybrid solution that exploits asymmetric redistribution and structural oscillation in liquid-repelling applications, paving the rigidity-flexibility cooperative way of wettability tuning. Also, the flexibility-patterned surface is applied to accelerate liquid evaporation.

Tunable Adhesive Self-Cleaning Coating with Superhydrophobicity and Photocatalytic Activity.

Superhydrophobic coatings with intelligent properties have attracted much attention because of their wide application in many fields. However, there is a limited amount of literature on superhydrophobic coatings whose wettability and adhesion can be adjusted by UV irradiation and calcination at the same time. In this study, amorphous SiO2 microspheres (A-SiO2) and nano-TiO2 particles (N-TiO2) were used to fabricate A-SiO2/N-TiO2 composites by wet grinding, and then, they were modified with polydimethylsiloxane (PDMS) and sprayed onto substrate surfaces to obtain a tunable adhesive superhydrophobic A-SiO2/N-TiO2@PDMS coating. It is worth noting that the wettability and adhesion of the coating to water droplets could be adjusted by UV irradiation and calcination. The mechanisms of the aforementioned phenomena were studied. Moreover, methyl orange solution could be degraded by the coating due to its photocatalysis. The as-prepared coating had good adaptation to different substrates and outdoor environments. Moreover, the surfaces of these coatings exhibited the same liquid repellency towards different droplets. This research provides an environmental strategy to prepare advanced self-cleaning coatings.

Robust Superhydrophobic and Repellent Coatings Based on Micro/Nano SiO2 and Fluorinated Epoxy

Superhydrophobic surfaces possess low mechanical strength, and can be easily contaminated by fluids with low surface tension, such as oil; this hinders their practical applications. In this study, fluorinated epoxy was prepared through the thiol-ene click reaction at first. The superhydrophobic surface with high oil-repellency was prepared by the addition of unmodified nano-SiO2 and micron-SiO2 to the fluorinated epoxy. The effect of the ratio of micro- and nano-silica particles on the morphology and wettability of the coating was investigated. It was shown that a re-entrant structure appears and FEP-S coating has good liquid repellency when the amounts of nano-SiO2 and micro-SiO2 are equal. The contact angles of the FEP-S coating (coating with the best liquid repellent performance) for water, glycerol, ethylene glycol, and diiodomethane were 158.6° ± 1.1°, 152.4° ± 0.9°, 153.4° ± 1.3°, and 140.7° ± 0.9°, respectively. In addition, the superhydrophobic coatings possess excellent mechanical and chemical durability, excellent performance in self-cleaning, corrosion resistance, and anti-icing properties. The preparation method of superhydrophobic coating is relatively simple; therefore, it has a wide range of applications and can also be applied to various substrates.

Blood repellent superhydrophobic surfaces constructed from nanoparticle-free and biocompatible materials

Durable and environment friendly superhydrophobic surfaces are needed for a set of important applications. Biomedical applications, in particular, impose stringent requirements on the biocompatibility of the materials used in the fabrication of superhydrophobic surfaces. In this study, we demonstrate the fabrication of mechanically durable superhydrophobic surfaces via an in-situ structuring strategy starting from natural carnauba wax and biocompatible polydimethylsiloxane (PDMS) materials. The transfer of the structure of the paper to a free-standing PDMS film provided the microscale structure. On top of this structured surface, the wax was spray-coated, initially resulting in a relatively homogeneous film with limited liquid repellence. The key in achieving superhydrophobicity was rubbing the surface for in-situ generation of a finely textured wax coating with a water contact angle of 169° and a sliding angle of 3°. The hierarchically structured surface exhibits mechanical robustness as demonstrated with water impact and linear abrasion tests. We finally demonstrate repellence of the surfaces against a range of blood products including platelet suspension, erythrocyte suspension, fresh plasma, and whole blood.

Lubricant-grafted omniphobic surfaces with anti-biofouling and drag-reduction performances constructed by reactive organic–inorganic hybrid microspheres

Recently, slippery liquid-infused surfaces (SLIPSs) have been demonstrated for widespread applications due to their excellent omniphobic properties. However, the complex construction process and the instability of the lubricant layer of SLIPSs constrain its practical applications. Herein, self-adhesive organic–inorganic hybrid microspheres (Poly@V-SiO2) with controlled particle sizes and adjusted chemical constituents were prepared via the sol–gel method and radical polymerization processes. The obtained Poly@V-SiO2 microspheres showed superhydrophobicity without post-modification. Moreover, the Poly@V-SiO2 with epoxy groups could self-assembled on the hydroxylated substrates via the epoxy-hydroxyl ring-opening reaction. Furthermore, the lubricant-grafted slippery surface (LGSS) was obtained by the reaction of the remaining epoxy groups of Poly@V-SiO2 and the amino terminated polydimethylsiloxane. The LGSS exhibited outstanding liquid repellency to water and organic solvents and demonstrated excellent anti-biofouling properties. Besides, the LGSS performed sailing velocity boost by nearly 1.8 times in both water and blended oil with drag reduction rates of almost 80%. More importantly, the covalently-grafted lubricant oil demonstrated excellent long-term stability under extreme operating conditions such as high/low temperature, ultraviolet irradiation, high-speed shear, and water impact. Therefore, the robust anti-fouling LGSS can be considered a promising material in daily life and industrial applications.

Super liquid repellent coatings against the everyday life wear: Heating, freezing, scratching

Super liquid repellent coatings are among the most promising candidates for self-cleaning surfaces for indoor and outdoor applications. However, the characteristic nano- and micro-scale protrusions can easily be damaged. Improving the durability of these coatings belongs to the most important challenges to increase the coating's application potential. Here, we show that commercial polyester fabrics coated with silicone nanofilaments maintain their self-cleaning properties throughout repeated freezing-unfreezing cycles, ironing, and mechanical stress. The coating improves the heat resistance of the fabric. The surface keeps its water repellency until the fabric is almost destroyed by scratching with sandpaper or a metal sponge. The excellent performance results from the synergetic effects of i) the interwoven structure of the fabric and ii) the intrinsic hydrophobic and flexible nature of the fabric and of the nanofilaments coating. The combination of these factors generates a product which overcomes the most claimed drawbacks of super liquid repellent coatings.

Development and Investigation of PEDOT:PSS Composition Coated Fabrics Intended for Microwave Shielding and Absorption.

This study presents the investigation of the electromagnetic properties and resistance performance of electrically conductive fabrics coated with composition containing the conjugated polymer system poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS). The developed fabrics were intended for electromagnetic radiation (EMR) shielding in microwave range and for absorbing microwaves in radar operating range, so as to act as radar absorbing materials (RAM). The measurements of reflection and transmission of the developed fabrics were performed in a frequency range of 2–18 GHz, which covers the defined frequencies relevant to the application. Four types of fabrics with different fiber composition (polyamide; polyamide/cotton; wool and para-aramid/viscose) were selected and coated with conductive paste using screen printing method. It was found that EMR shielding effectiveness (SE) as well as absorption properties depend not only the amount of conductive paste topped on the fabric, but also resides in the construction parameters of fabrics. Depending on such fabric structural parameters as density, mass per unit area, type of weave, a layer of shield (or coating) just sticks on the fabric surface or penetrates into fabric, changing the shield thickness and herewith turning SE results. Meanwhile, the fiber composition of fabrics influences mostly bonding between fibers and polymer coating. To improve the resistance performance of the developed samples, a conventional textile surface modification technique, atmospheric plasma treatment, was applied. Initially, before plasma treatment and after treatment the fabrics were evaluated regarding an aqueous liquid repellency test, measuring the contact angles for the water solvent. The influence of plasma treatment on resistance performance of coated fabrics was evaluated by subjecting the plasma treated samples and untreated samples to abrasion in the Martindale abrasion apparatus and to multiplex washing cycles. These investigations revealed that applied plasma treatment visibly improved abrasion resistance as a result of better adhesion of the coating. However, washing resistance increased not so considerably.

Preparation of durable superamphiphobic cotton fabrics with self-cleaning and liquid repellency

A durable superamphiphobic cotton fabric was obtained by coating SiO2 aerogel particles, polydimethylsiloxane (PDMS), and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFTES) on a cotton fabric via the dip-pad-dry process. The surface morphology, chemical composition, and thermal degradation behavior characterization of the as-prepared cotton fabric (PFTES/PDMS/SiO2@Cotton fabric) were performed, respectively. It was proved that the coated cotton fabric was successfully covered with PFTES/PDMS/SiO2. The porous rough surface topology structure due to the SiO2 aerogel particles along with low surface energy because of the fluorinated chains and PDMS adhesive layer on the as-obtained PFTES/PDMS/SiO2@Cotton fabric can trap a layer of air, endowing the coated fabric durable superamphiphobicity. The prepared superamphiphobic cotton fabric with a water contact angle (WCA) of 159.0 ± 0.8° and an oil contact angle (OCA) of 154.5 ± 0.7° showed good liquid repellence for common liquids in daily life like orange juice, cola, coffee, and milk, exhibiting excellent self-cleaning and stain-resistance property. Moreover, the superamphiphobic cotton fabric possessed good durability and still maintained superamphiphobicity after mechanical abrasion for 1500 cycles or ultraviolet (UV) irradiation for 96 h. This superamphiphobic cotton fabric exhibited potential applications in various fields due to the high repellency to various liquids.

A Superhydrophobic and Oleophobic Silicone Sponge with Hierarchical Structures.

The fabrication of amphiphobic materials requires a precise and complicated design, especially for 3D porous materials, and amphiphobic sponges have rarely been investigated. This paper describes the synthesis of a superhydrophobic and oleophobic silicone sponge (SS-F) by simply building hierarchical structures, that is, introducing a secondary structure on the pore walls of a hydrophobic and oleophilic silicone sponge. This simple and efficient synthesis method is based on the thiol-ene click reaction. The uniform structure, composition, and hierarchical structures of SS-F are confirmed. The results of the analyses show that the secondary microstructure improves liquid repellency, while the rough and porous surface design ensures durability. Thus, SS-F exhibits good stability, and the amphiphobicity of the surface could withstand scalpel cutting, cyclic compression, extreme temperatures of 250 and -196°C for 5 h, and long-term storage in an ambient environment. Both its outer and inner surfaces show superhydrophobicity and oleophobicity, which restrict the ability of the adsorption of liquids, enabling its use in oil and water. The introduction of hierarchical structures paves a way for preparing other 3D porous materials.

Robust Hybrid Omniphobic Surface for Stain Resistance.

Inspired by natural living surfaces, researchers have developed many excellent anti-smudge coatings, but there remain some critical challenges such as complex or expensive fabrications, poor long-term stability, non-transparency, etc., which may limit their large-area application. In this work, we designed a robust and transparent omniphobic coating with a one-step dip coating method. The perfluoropolyether chains were grafted on a smooth glass surface, and the coating surface not only presented good liquid repellency and stain resistance but also owned excellent mechanical wear resistance. The stain resistance property and wettability have barely changed after hundreds of thousands of friction cycles in air or even in an organic solvent surrounding. The robust hybrid coating possesses simple preparation, an excellent property, and durability, which may bring a widespread interest in the engineering application field.

Photocatalytic Superamphiphobic Coatings and the Effect of Surface Microstructures on Superamphiphobicity.

In recent years, superamphiphobic coatings have been widely used in industrial transportation and environmental treatments because of their unique liquid repellency. In this study, WO3-TiO2 nanorods/SiO2 were used as the constructor of surface microstructures, and 1H,1H,2H,2H-perfluorodecyltriethoxysilane was used as the provider of low surface energy, and a photocatalytic superamphiphobic coating (FTS coating) was prepared. The microstructure and chemical composition of the coating was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The coating exhibited excellent photocatalytic activity toward degradation methyl red and nitric oxide (NO), and the degradation efficiency to NO reached 47.8%. Also, the advanced contact angle and the hysteresis angle of water, glycol, glycerol, and olive oil was used to evaluate the superamphiphobicity. After 7 days of ultraviolet (UV) aging, five cycles of airbrush flushing and 48 h of immersion in acid, salt, and alkali solutions, the FTS coating still exhibits excellent amphiphobicity, which lays a foundation for its large-scale applications in the concrete exterior wall. The surface microstructure and the formation of air pockets are a prerequisite for superamphiphobicity, which promotes the liquid on the coating surface into the Cassie-Baxter state. Furthermore, the formation of air pockets is closely related to the gas adsorption capacity and the specific surface area (SBET) of the surface microstructure on the coating surface. The coatings with different SBET constructed and the advanced contact angle were measured. The influence of air pockets on the superamphiphobicity of coatings was studied in combination with the optical microscope. The understanding that SBET further influences superamphiphobicity by affecting the surface air pockets is proposed.

Comparison of standards for chemical protective clothing on performance requirements and measurements

Chemical protective clothing is widely used by emergency teams in certain industries and such as fire-fighting and medical protection fields. Due to the differences of assessment, specific requirements for target products, and test methods, the relevant standards for such clothing vary greatly. By analyzing standards on chemical protective clothing, this study summarized their differences in assessment items and test methods for basic performances such as seam strength, leak tightness, permeability by liquid/gas chemicals, resistance to ignition, liquid repellency and penetration by liquids.

WO3-based slippery coatings with long-term stability for efficient fog harvesting

Inspired by Nepenthes pitcher plants, slippery liquid-infused porous surfaces (SLIPSs) have attracted wide attention and exhibited remarkable liquid repellency, droplet motion control and antifouling properties. However, lubricant-impregnated surfaces have poor durability, leading to loss of control of the movements of droplets during applications. Herein, WO3-based slippery coatings with high stability were prepared by the spray method and photocatalytic reaction. Notably, on the basis of the hierarchical structures, the strong intermolecular forces between the polydimethylsiloxane brush and silicone oil led to the formation of a stable lubricant layer on the WO3-based slippery coating, which can suppress lubricant loss during water collection. After a series of stability tests, such as high-speed centrifugation, long-term storage, acidic solution and multiple heating/cooling cycles, the biomimetic slippery surface still displays excellent surface-slippery stability. Furthermore, the slippery surface exhibits superior water mist capture, water droplet expansion and harvested water removal abilities, leading to good water collection performance. The silicone oil content in the collected water was 28 mg/L, demonstrating that the loss of oil was lower during the water collection process. Even under harsh environments, including multiple heating/cooling cycles, long-term storage and high shear force, lubricant-impregnated coatings can also maintain good water collection efficiency. Therefore, these slippery coatings are promising for widespread application.

Severe dyspnea and uncontrolled seizures following meperfluthrin poisoning: a case report

BackgroundMeperfluthrin is a novel sanitary cyhalothrin insecticide invented in China and has increasingly been used to produce liquid mosquito repellents. Oral meperfluthrin poisoning in human has rarely been reported. Here, we reported a case of meperfluthrin poisoning by ingestion of a meperfluthrin-based liquid mosquito repellent in a 16-month-old infant.Case presentationA 16-month-old boy with a history of accident ingestion of meperfluthrin was admitted to our hospital’s emergency department. He exhibited severe dyspnea, and lung radiograph showed multiple patchy and cord-like high-density shadows bilaterally in a short time. He also suffered 35 min of seizures which were finally controlled by the intravenous infusion of propofol. He was diagnosed with meperfluthrin poisoning, status epilepticus and severe pneumonia. After treated with methylprednisolone, aerosolized beclomethasone dipropionate, anti-infection, and some critical supportive therapy, the patient was in good health and showed no symptoms during 12 months of follow-up.ConclusionsMeperfluthrin poisoning is rare. Oral meperfluthrin poisoning shows neurotoxic effects and pulmonary toxicity. Controlling seizures rapidly and ensuring an adequate oxygen supply are critical to the successful treatment.

Reed leaf-inspired anisotropic slippery lubricant-infused surface for water collection and bubble transportation

Anisotropic slippery lubricant-infused surfaces with favorable sliding behaviors are highly desirable for water collection and directional bubble transportation. Inspired by natural reed leaves with anisotropic wettability along two directions of groove geometry, a soft lithographic approach of replica molding was implemented to successfully replicate the surface microstructures of reed leaves using polydimethylsiloxane (PDMS). Subsequently, various lubricants were infused to fabricate anisotropic hydrophobic or hydrophilic slippery surfaces. The as-prepared anisotropic hydrophilic lubricant-infused surface (A-HH-LIS) exhibited remarkable droplet nucleation and removal during water collection. The results demonstrated that the surfaces maintained stable water collection rate even under high shear force rate up to 7000 rpm and exhibited favorable liquid repellency at lower or higher temperature. Furthermore, the directional transportations of water (in air) and air bubbles (underwater) on anisotropic hydrophobic lubricant-infused surface (A-HB-LIS) were achieved with outstanding performance. Moreover, the effects of tilted angle β (the angle between sample and plumb line) and rotational angle α (the angle between groove direction and horizontal line) on sliding behavior were explored. The reported anisotropic slippery lubricant-infused surfaces have great potential in water condensation, bubble transportation and marine anti-fouling.

Preparation of a temperature-sensitive superhydrophobic self-cleaning SiO2-TiO2@PDMS coating with photocatalytic activity

In this paper, SiO2-TiO2 composite particles were prepared by loading nano-TiO2 onto the surfaces of amorphous SiO2 microspheres, which were then modified with PDMS to obtain a SiO2-TiO2@PDMS ternary compound. The photocatalytic performance of SiO2-TiO2@PDMS and the wettability of the coated surface were tested and characterized. Moreover, the effect of microstructure and composition of SiO2-TiO2@PDMS on its properties was studied. The results showed that SiO2-TiO2@PDMS possessed a certain degree of photocatalytic activity and the coating was almost superhydrophobic. Furthermore, the wettability and adhesion to water droplets of the SiO2-TiO2@PDMS coating were affected by the heat-treatment temperature; the mechanism of the above phenomena was also analysed. Moreover, the as-prepared coating exhibited excellent repellent effects towards acid (pH = 2), alkaline (pH = 11), and organic dye droplets. A mechanically damaged coating maintained its liquid repellence, indicating that the good mechanical stability of the coating. The superhydrophobicity of the as-prepared coating did not decrease after UV irradiation for 8 h, illustrating that the as-prepared coating had a great UV irradiation resistance. In addition, the as-prepared coating was environmentally friendly and free of fluorides and is therefore suitable for practical applications.

Universal and tunable liquid\u2013liquid separation by nanoparticle-embedded gating membranes based on a self-defined interfacial parameter

Superwetting porous membranes with tunable liquid repellency are highly desirable in broad domains including scientific research, chemical industry, and environmental protection. Such membranes should allow for controllable droplet bouncing or spreading, which is difficult to achieve for low surface energy organic liquids (OLs). Here we develop an interfacial physical parameter to regulate the OL wettability of nanoparticle-embedded membranes by structuring synergistic layers with reconfigurable surface energy components. Under the tunable solid-liquid interaction in the aggregation-induced process, the membranes demonstrate positive/negative liquid gating regularity for polar protic liquids, polar aprotic liquids, and nonpolar liquids. Such a membrane can be employed as self-adaptive gating for various immiscible liquid mixtures with superior separation efficiency and permeation flux, even afford successive achievement of high-performance in situ extraction-back extraction coupling. This study should provide distinctive insights into intrinsic wetting behaviors and have pioneered a rational strategy to design high-performance separation materials for diverse applications.

An assessment on the use of liquid vaporizer mosquito repellents and their perceived adverse effect on users

The present study focuses on an assessment of the use of liquid vaporizer mosquito repellent and the effects caused due to the active ingredients (AI) present them through a concise survey. Basic information on the various brand of liquid vaporizers used as mosquito repellents was collected from local markets. To gauge the extent of protective measures employed by the local people in Chennai and to control mosquito population a multi-centric questionnaire was designed. The study presented the valuable data on public preferences towards mosquito repellents. A large proportion of the residents prefers liquid vaporizers over coils, mats and fast cards available in the market. Though there are considerable products of herbal liquid vaporizers available, synthetic products are used in large proportions. The AI present in these synthetic liquid vaporizers posed serious health effects like breathing problem and eye irritations among the users. Apart from this they also failed to offer complete protection and their cost is comparatively high in the market. Though the responders face constant mosquito related problems, 38% of them failed to take any measures to eliminate mosquito menace in and around their localities. Present study has revealed that mosquito repellents especially liquid vaporizers pose serious health hazards and hence awareness has to be initiated to go for an alternative approach.

Bioinspired photocatalytic hedgehog coating for super liquid repellency

Bioinspired hedgehog coating is superomniphobic to liquid with surface tension of 25.3 mN m−1, and repels liquids with surface tensions down to 16 mN m−1 when it is converted to a one-step liquid infused surface utilizing its photocatalytic property.

Enduring liquid repellency through slippery ionic liquid-infused organogels

Ionic liquid-infused organogel coatings increase temperature- and long-term stabiity of lubricant-infused repellent coatings.