Fabrication of multifunctional amphiphobic surfaces on copper substrates

A Superhydrophobic, Antibacterial, and Durable Surface of Poplar Wood

The silver particles were grown in situ on the surface of wood by the silver mirror method and modified with stearic acid to acquire a surface with superhydrophobic and antibacterial properties. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray energy spectroscopy (XPS) were used to analyze the reaction mechanism of the modification process. Scanning electron microscopy (SEM) and contact angle tests were used to characterize the wettability and surface morphology. A coating with a micro rough structure was successfully constructed by the modification of stearic acid, which imparted superhydrophobicity and antibacterial activity to poplar wood. The stability tests were performed to discuss the stability of its hydrophobic performance. The results showed that it has good mechanical properties, acid and alkali resistance, and UV stability. The durability tests demonstrated that the coating has the function of water resistance and fouling resistance and can maintain the stability of its hydrophobic properties under different temperatures of heat treatment.

Transparent and Flexible Amphiphobic Coatings with Excellent Fold Resistance via Solvent-Free Coating and Photocuring of Fluorinated Liquid Nitrile-Butadiene Rubber

Amphiphobic surfaces have been developed for various applications. However, the harsh construction conditions and multistep processes limit their practical application. Especially for those with a particular surface roughness and morphology, the amphiphobic property might provide a slight deformation. Here, a facile large-area construction of transparent and flexible amphiphobic coatings with excellent fold resistance has been established by simple casting of the fluorinated liquid nitrile-butadiene rubber (F-LNBR) followed by solvent-free photocuring. It was found that the fluorocarbon groups could concentrate onto the coating surface during the UV-induced photocuring. With a certain coating amount, a stable oleophobic coating was achieved with static contact angles of about 95° and 111° for nonpolar oil (n-hexadecane) and polar oil (diiodomethane). Most importantly, the static contact angles of water and diiodomethane of the amphiphobic coatings on the iron sheet increased after bending and remained around 131° and 120° after being completely folded in half for 100 cycles because the inner fluorocarbon groups could be squeezed out from the flexible cross-linked rubber matrix as a reservoir. Such features indicated the promising self-cleaning and surface protection of the proposed transparent and flexible amphiphobic coatings for deformable substrates.

Preparation of a Highly Oleophobic Magnesium Alloy AZ31 Surface with Hierarchical Structure and Fluorination

Wettability is an important surface property owing to its useful characteristics such as self-cleaning, antifrosting, and anticorrosion. In particular, an oleophobic surface, which can overcome the limitation of the antifouling performance of a hydrophobic surface, is a considerably valuable research subject. Magnesium alloys are widely used in various industrial fields owing to their superior mechanical performance; however, a technology that is applicable for surface modification has been limited due to their chemical properties. In this study, a new method to prepare a highly oleophobic magnesium alloy AZ31 surface is introduced; this method involves applying a hierarchical structure and fluorination. The hierarchical structure was formed via two-step anodization and magnesium hydroxide formation, and a self-assembled monolayer (SAM) coating method was applied to fluorinate the surface. This hierarchical structure with low surface energy can reduce the contact area between the surface and droplets, thereby decreasing the adhesive force. Contact angles were measured using various test liquids to evaluate the oleophobic surface, and all test liquids, including rapeseed oil (35.0 mN/m), were repelled by the surface.

Mechanical Stability of PDMS-Based Micro/Nanotextured Flexible Superhydrophobic Surfaces under External Loading

Superhydrophobicity based on the micro- and nanostructures is frangible to external loading. It is a challenging issue for flexible superhydrophobic surfaces to maintain superhydrophobicity while deforming under external loading. Herein, PDMS-based micro/nanotextured flexible surfaces with robust superhydrophobicity were fabricated by an effective and environmentally friendly method. The formation mechanism of the micro/nanotextured structures and the formation reason for superhydrophobicity were investigated. The effects of reaction time on wettability were also explored. Besides, the changes of morphology and superhydrophobicity under external loading were studied. It is found that micro/nanotextured structures remained unchanged, and only the bottom layer generated cracks under external loading. There were no obvious changes of superhydrophobicity under a tensile strain up to breakage, 500 cycles of bending, and 100 cm height of water droplets and NaCl particle impact. The self-cleaning property was also verified in cleaning the surfaces covered with various contaminants by water droplets. The fabricated PDMS-based micro/nanotextured flexible surfaces with good mechanical stability and self-cleaning property are expected to be applied in flexible electronic devices.