Fabrication of superhydrophobic surface with hierarchical structure by thermal imprinting and spraying

Study on the High-Efficiency Preparation of Superhydrophobic Polymer Thin Films by Continuous Micro/Nano Imprinting

In order to improve the preparation efficiency, quality stability, and large-area preparation of superhydrophobic thin films, a roll-to-roll continuous micro-nano imprinting method for the efficient preparation of superhydrophobic polymer films is proposed. A wear-resistant mold roller with hierarchical microstructure is prepared by wire electrical discharge machining (WEDM). The rheological filling model is constructed for revealing the forming mechanism of superhydrophobic polymer films during continuous micro/nano imprinting. The effects of imprinting temperature, rolling speed and the surface texture size of the template on the surface texture formation rate of polymer films are analyzed. The experimental results show that, compared with other process methods, the template processed by WEDM shows excellent wear resistance. Moreover, the optimal micro/nano imprinting parameters are the mold temperature of 190 °C (corresponding film temperature of 85 ± 5 °C), rolling speed of 3 rpm and roller gap of 0.1 mm. The maximum contact angle of the polymer film is 154°. In addition, the superhydrophobic polymer thin film has been proven to have good self-cleaning and anti-icing performance.

Methods for improving the properties of zinc for the application of biodegradable vascular stents

Biodegradable stents can support vessels for an extended period, maintain vascular patency, and progressively degrade once vascular remodeling is completed, thereby reducing the constraints of traditional metal stents. An ideal degradable stent must have good mechanical properties, degradation behavior, and biocompatibility. Zinc has become a new type of biodegradable metal after magnesium and iron, owing to its suitable degradation rate and good biocompatibility. However, zinc's poor strength and ductility make it unsuitable as a vascular stent material. Therefore, this paper reviewed the primary methods for improving the overall properties of zinc. By discussing the mechanical properties, degradation behavior, and biocompatibility of various improvement strategies, we found that alloying is the most common, simple, and effective method to improve mechanical properties. Deformation processing can further improve the mechanical properties by changing the microstructures of zinc alloys. Surface modification is an important means to improve the biological activity, blood compatibility and corrosion resistance of zinc alloys. Meanwhile, structural design can not only improve the mechanical properties of the vascular stents, but also endow the stents with special properties such as negative Poisson 's ratio. Manufacturing zinc alloys with excellent degradation properties, improved mechanical properties and strong biocompatibility and exploring their mechanism of interaction with the human body remain areas for future research.

Micro-/Nanohierarchical Structures Physically Engineered on Surfaces: Analysis and Perspective

The high demand for micro-/nanohierarchical structures as components of functional substrates, bioinspired devices, energy-related electronics, and chemical/physical transducers has inspired their in-depth studies and active development of the related fabrication techniques. In particular, significant progress has been achieved in hierarchical structures physically engineered on surfaces, which offer the advantages of wide-range material compatibility, design diversity, and mechanical stability, and numerous unique structures with important niche applications have been developed. This review categorizes the basic components of hierarchical structures physically engineered on surfaces according to function/shape and comprehensively summarizes the related advances, focusing on the fabrication strategies, ways of combining basic components, potential applications, and future research directions. Moreover, the physicochemical properties of hierarchical structures physically engineered on surfaces are compared based on the function of their basic components, which may help to avoid the bottlenecks of conventional single-scale functional substrates. Thus, the present work is expected to provide a useful reference for scientists working on multicomponent functional substrates and inspire further research in this field.

Icing behavior of supercooled droplets on superhydrophobic polymercoatings between lotus effect and petal effect

This paper investigated anti-icing behavior and wettability of droplets on superhydrophobic polymercoatings between lotus effect and petal effect, which were prepared on surfaces of 2021 aluminum alloy with 1H, 1H, 2H, 2H-heptafluorodecyl (FAS-17). The prepared surfaces displayed excellent hydrophobicity with contact angles of 154.9° ± 1.5°and 139.8° ± 1.3°, while rolling angles are 4° ± 1.0° (lotus effect) and 30° ± 1.5° (petal effect). Thus, the present study focused on the different characterizations and the anti-icing potential of the superhydrophobic polymersurfaces were analyzed based on three parameters including the icing delay time, the crystallization temperature of water droplets, and contact time of impinging droplets on the cold superhydrophobic polymer coatings (−15 °C). Furthermore, the anti-icing of superhydrophobic coatings between lotus effect and petal effect with freezing time and crystallization temperature experimental phenomena were consistent with the thermodynamic analysis. It is also proved that the droplets have different bounce behavior on different polymercoating surfaces by droplet impact experiment. The study offers a comprehensive perspective on polymercoatings of different wetttablility for anti-icing behavior applications.

Antibacterial features of material surface: strong enough to serve as antibiotics?

Bacteria are small but need big efforts to control. The use of antibiotics not only produces superbugs that are increasingly difficult to inactivate, but also raises environmental concerns with the growing consumption. It is now believed that the antibacterial task can count on some physiochemical features of material surfaces, which can be anti-adhesive or bactericidal without releasing toxicants. It is necessary to evaluate to what extent can we rely on the surface design since the actual application scenarios will need the antibacterial performance to be sharp, robust, environmentally friendly, and long-lasting. Herein, we review the recent laboratory advances that have been classified based on the specific surface features, including hydrophobicity, charge potential, micromorphology, stiffness and viscosity, and photoactivity, and the antibacterial mechanisms of each feature are included to provide a basic rationale for future design. The significance of anti-biofilms is also introduced, given the big role of biofilms in bacteria-caused damage. A perspective on the potential wide application of antibacterial surface features as a substitute or supplement to antibiotics is then discussed. Surface design is no doubt a solution worthy to explore, and future success will be a result of further progress in multiple directions, including mechanism study and material preparation.

Fabrication of Superhydrophobic Coating Based on Waterborne Silicone-Modified Polyurethane Dispersion and Silica Nanoparticles

In this work, eco-friendly superhydrophobic coatings were prepared by dispersing hydrophobic silica nanoparticles and a waterborne silicone-modified polyurethane dispersion into an ethanol solution, which was free of fluorine and volatile toxic solvents. The effects of the silica content on the hydrophobicity and scratch resistance of the hydrophobic surfaces were investigated by WCA measurements and a sandpaper abrasion test, respectively. The experimental results indicated that when the silica content exceeded 30% by mass, the silica/silicone-modified polyurethane coatings had superhydrophobicity. Meanwhile, the superhydrophobic coatings with a silica content of 30% by mass simultaneously had the optimal mechanical stability. We studied the morphology and roughness of the hydrophobic surfaces with different silica content and attempted to briefly explain the influence mechanism of silica content. Furthermore, anti-icing and oil-water separation experiments were carried out on the superhydrophobic coatings, which exhibited good anti-icing performance and high separation efficiency. The eco-friendly superhydrophobic coating is expected to be applied in the fields of oil-water separation, anti-icing, and self-cleaning, etc.

Preparation of Transparent Sandwich-like Superhydrophobic Coating on Glass with High Stability and Self-Cleaning Properties

High stability and transparent superhydrophobic coating on a glass substrate that can effectively repel the wetting dust as a self-cleaning property are beneficial traits for solving the decrease in optical lens clarity in an unmanned underground mining environment. However, the transparent superhydrophobic coating has still not been applied due to the contradiction between visibility, hydrophobicity and durability. Herein, a sandwich-like superhydrophobic coating was designed and prepared on borosilicate glass, which consisted of a micro/nanostructure body of neutral silicone sealant (primer) and hydrophobic silica nanoparticles (interlayer), as well as a protective layer of ultraviolet (UV) gel. The coated glass exhibited excellent superhydrophobicity towards many aqueous solutions, and had highly visible light transparency of 80% at 4 wt.% primer mass content. Furthermore, significant tests including the droplet impact, hot water boiling, stirring in acetic acid aqueous solution and sandpaper abrasion were performed on our superhydrophobic coating, which indicated that the obtained transparent coating had good stability and excellent mechanical durability. The coated glass also showed a more wonderful self-cleaning property compared with that of the original glass. This superhydrophobic coating on glass substrate, fabricated by a facile and cost-effective layer-by-layer construction approach, has great potential for general and practical application in the unmanned mining environment under multiple dust and atomized water conditions.