The fabrication of mechanically durable and stretchable superhydrophobic PDMS/SiO2 composite film

Study on PTFE superhydrophobic coating modified by IC@dMSNs and its enhanced antibacterial effect

INTRODUCTION

Vascular catheter-related infections and thrombosis are common and may lead to serious complications after catheterization. Reducing the incidence of such infections has become a significant challenge.

OBJECTIVES

This study aims to develop a super hydrophobic nanocomposite drug-loaded vascular catheter that can effectively resist bacterial infections and blood coagulation.

METHODS

In this study, a SiO2 nanocoated PTFE (Polytetrafluoroethylene) catheter (PTFE-SiO2) was prepared and further optimized to prepare a SiO2 nanocoated PTFE catheter loaded with imipenem/cilastatin sodium (PTFE-IC@dMSNs). The catheters were characterized for performance, cell compatibility, anticoagulant performance, in vitro and in vivo antibacterial effect and biological safety.

RESULTS

PTFE-IC@dMSNs catheter has efficient drug loading performance and drug release rate and has good cell compatibility and anticoagulant effect in vitro. Compared with the PTFE-SiO2 catheter, the inhibition ring of the PTFE-IC@dMSNs catheter against Escherichia coli increased from 3.98 mm2 to 4.56 mm2, and the antibacterial rate increased from about 50.8 % to 56.9 %, with a significant difference (p < 0.05). The antibacterial zone against Staphylococcus aureus increased from 8.63 mm2 to 11.74 mm2, and the antibacterial rate increased from approximately 83.5 % to 89.3 %, showing a significant difference (p < 0.05). PTFE-IC@dMSNs catheter also has good biocompatibility in vivo. Furthermore, the PTFE-IC@dMSNs catheter can reduce the adhesion of blood cells and have excellent anticoagulant properties, and even maintain these properties even with the addition of imipenem/cilastatin sodium.

CONCLUSION

Compared with PTFE, PTFE-SiO2 and PTFE-IC@dMSNs catheters have good characterization performance, cell compatibility, and anticoagulant properties. PTFE SiO2 and PTFE-IC@dMSNs catheters have good antibacterial performance and tissue safety against E. coli and S. aureus. Relatively, PTFE-SiO2 and PTFE-IC@dMSNs catheter has better antibacterial properties and histocompatibility and has potential application prospects in anti-bacterial catheter development and anticoagulation.

Stretchable superhydrophobic fluororubber fabricated by transferring mesh microstructures

Stretchable flexible superhydrophobic surfaces are in great demand to achieve waterproofing performance in aerospace, electronic industry, and other fields. However, there are still many challenges in developing superhydrophobic surfaces, which maintain their wetting characteristics under high strain conditions with good tensile durability. Here, we propose a simple and efficient method to prepare a stretchable superhydrophobic fluororubber surface composed of hierarchical micro-convexities, which are orderly arranged and interconnected. Its peculiar structure shows excellent superhydrophobicity (155.48 ± 1.97°) and high water sliding angle due to Cassie's impregnating wetting regime. Due to the special structure and high mechanical strength of the surface, it can still maintain its superhydrophobic property after a variety of durability tests, including various stretching tests, sandpaper abrasion, sand impact, and high-temperature treatment. In addition, the surface can still realize the lossless transfer of water droplets even at large stretching strains, which is expected to be applied to microfluidic devices under extreme working conditions.

Eco-Friendly Fabrication of Transparent Superhydrophobic Coating with Excellent Mechanical Robustness, Chemical Stability, and Long-Term Outdoor Durability

Surfaces that possess both superhydrophobicity and high transparency at the same time recently have attracted extensive attention in outdoor applications. However, fabrication and application of transparent superhydrophobic coating usually face following challenges: the micro-nano hierarchical structure required for superhydrophobicity usually leads to a decrease in the light transmittance due to its light trapping effect; fluorine-containing materials used in the preparation of superhydrophobic surfaces are potentially harmful to humans and the environment; and the superhydrophobic surface is easily destroyed by external factors. In this work, a transparent superhydrophobic coating was fabricated via an inexpensive and eco-friendly two-step method, that is, dipping glass substrate into the polydimethylsiloxane/SiO₂ suspension followed by calcination treatment. The prepared coating showed superhydrophobicity with a water contact angle of 164° and a sliding angle less than 1.0°. In the visible light region with the wavelength range of 300-900 nm, the maximal transmittance of the superhydrophobic coating was ∼91.4%, which is higher than that of the untreated glass substrate (∼90.9%). Moreover, the coating can maintain superhydrophobicity and high transmittance after sandpaper abrasion, water flow impact, immersion in strong acid/alkaline solution, UV irradiation, and long-term outdoor exposure. We believing that the coating has huge potential value in outdoor applications.

Recent Developments in Blood-Compatible Superhydrophobic Surfaces

Superhydrophobic surfaces, as indicated in the name, are highly hydrophobic and readily repel water. With contact angles greater than 150° and sliding angles less than 10°, water droplets flow easily and hardly wet these surfaces. Superhydrophobic materials and coatings have been drawing increasing attention in medical fields, especially on account of their promising applications in blood-contacting devices. Superhydrophobicity controls the interactions of cells with the surfaces and facilitates the flowing of blood or plasma without damaging blood cells. The antibiofouling effect of superhydrophobic surfaces resists adhesion of organic substances, including blood components and microorganisms. These attributes are critical to medical applications such as filter membranes, prosthetic heart valves, extracorporeal circuit tubing, and indwelling catheters. Researchers have developed various methods to fabricate blood-compatible or biocompatible superhydrophobic surfaces using different materials. In addition to being hydrophobic, these surfaces can also be antihemolytic, antithrombotic, antibacterial, and antibiofouling, making them ideal for clinical applications. In this review, the authors summarize recent developments of blood-compatible superhydrophobic surfaces, with a focus on methods and materials. The expectation of this review is that it will support the biomedical research field by providing current trends as well as future directions.

Preparation strategy and evaluation method of durable superhydrophobic rubber composites

Superhydrophobic rubber composites have broad application prospects in national defense, industrial and agricultural production and daily life due to their special surface wettability. However, its poor durability at present seriously limits its practical application. Microstructure and low surface energy substances are the decisive factors to realize superhydrophobic surface. Therefore, three strategies to improve the durability of superhydrophobic surface were put forward, including improving the mechanical strength of microstructure, enhancing the adhesion between coating and substrate, and constructing self-repairing surface. On this basis, the preparation techniques of durable superhydrophobic rubber composites were summarized, and then the evaluation methods of durability of superhydrophobic rubber composites were introduced in detail from mechanical durability and chemical durability.

Hydrophobic Thin Films from Sol-Gel Processing: A Critical Review

Fabrication of hydrophobic thin films from a liquid phase is a hot topic with critical technological issues. Interest in the production of hydrophobic surfaces is growing steadily due to their wide applications in several industrial fields. Thin films from liquid phases can be deposited on different types of surfaces using a wide variety of techniques, while the design of the precursor solution offers the possibility of fine-tuning the properties of the hydrophobic coating layers. A general trend is the design of multifunctional films, which have different properties besides being hydrophobic. In the present review, we have described the synthesis through sol-gel processing of hydrophobic films enlightening the main achievements obtained in the field.

Robust Superhydrophobic Surface on Polypropylene with Thick Hydrophobic Silica Nanoparticle-Coated Films Prepared by Facile Compression Molding

Superhydrophobic surfaces have been extensively studied for their unique interfacial interaction between water and the surface, and they can be used for self-cleaning, drag reduction, anti-icing, and other applications. To make the superhydrophobic surfaces, nano/microscale structures and a low surface energy should be realized. The development of a durable superhydrophobic surface was hindered by the vulnerability of the surface to mechanical contact. To improve the robustness of the superhydrophobic surface toward mechanical damage, the hydrophobic polypropylene (PP) surface was coated with a thick layer of hydrophobic silica nanoparticles (SNPs) using a simple compression molding process. The thick layer consists of SNPs and PP, and the roles of SNPs and PP are nano/microscale structures with a low surface energy and binder for nanoparticles, respectively. This revealed improvement in the superhydrophobic tendency, with an apparent contact angle of about 170° and a sliding angle of less than 5°. The morphology and the corresponding elemental analysis of the PP/SNPs coated films were investigated using field emission scanning electron microscopy and energy-dispersive spectrometry. The mechanical durability of the superhydrophobic surface was evaluated by the scotch tape test and scratch test with sandpaper. The coated films with SNPs showed the superhydrophobic behavior after 25 tape tests. In addition, the coated films with SNPs showed a contact angle greater than 150° and a sliding angle less than 10° after a 100-cm scratch test with 1000 grit sandpaper, under a weight of 500 g, on an area of 40 × 40 mm2. The chemical stability of PP/SNPs coated films was also investigated in acidic, neutral, and alkaline medium solutions. The films showed good stability under the acidic and neutral medium solutions even after 24 h, but an alkaline medium could damage the surface. The obtained results demonstrated the robustness of the superhydrophobic coating with SNPs.

Recent developments in antimicrobial and antifouling coatings to reduce or prevent contamination and cross-contamination of food contact surfaces by bacteria

Illness as the result of ingesting bacterially contaminated foodstuffs represents a significant annual loss of human quality of life and economic impact globally. Significant research investment has recently been made in developing new materials that can be used to construct food contacting tools and surfaces that might minimize the risk of cross-contamination of bacteria from one food item to another. This is done to mitigate the spread of bacterial contamination and resultant foodborne illness. Internet-based literature search tools such as Web of Science, Google Scholar, and Scopus were utilized to investigate publishing trends within the last 10 years related to the development of antimicrobial and antifouling surfaces with potential use in food processing applications. Technologies investigated were categorized into four major groups: antimicrobial agent-releasing coatings, contact-based antimicrobial coatings, superhydrophobic antifouling coatings, and repulsion-based antifouling coatings. The advantages for each group and technical challenges remaining before wide-scale implementation were compared. A diverse array of emerging antimicrobial and antifouling technologies were identified, designed to suit a wide range of food contact applications. Although each poses distinct and promising advantages, significant further research investment will likely be required to reliably produce effective materials economically and safely enough to equip large-scale operations such as farms, food processing facilities, and kitchens.