One-step fabrication of robust superhydrophobic and superoleophilic surfaces with self-cleaning and oil/water separation function.

Superhydrophobic surfaces have great potential for application in self-cleaning and oil/water separation. However, the large-scale practical applications of superhydrophobic coating surfaces are impeded by many factors, such as complicated fabrication processes, the use of fluorinated reagents and noxious organic solvents and poor mechanical stability. Herein, we describe the successful preparation of a fluorine-free multifunctional coating without noxious organic solvents that was brushed, dipped or sprayed onto glass slides and stainless-steel meshes as substrates. The obtained multifunctional superhydrophobic and superoleophilic surfaces (MSHOs) demonstrated self-cleaning abilities even when contaminated with or immersed in oil. The superhydrophobic surfaces were robust and maintained their water repellency after being scratched with a knife or abraded with sandpaper for 50 cycles. In addition, stainless-steel meshes sprayed with the coating quickly separated various oil/water mixtures with a high separation efficiency (>93%). Furthermore, the coated mesh maintained a high separation efficiency above 95% over 20 cycles of separation. This simple and effective strategy will inspire the large-scale fabrication of multifunctional surfaces for practical applications in self-cleaning and oil/water separation.

From natural to biomimetic: The superhydrophobicity and the contact time.

The superhydrophobicities and the contact time of lotus leaf and reed leaf were investigated. The results indicated that both lotus leaf and reed leaf have good superhydrophobic properties, and the water contact time was 12.7 and 14.7 ms on the surface of lotus leaf and reed leaf, respectively. Surface structure plays a key role in the different contacting times. Homogeneous distribution of papillae on the surface of lotus leaf was more helpful to reduce the contact time than anisotropic groove-shape on the surface of reed leaf. Based on the bionics coupling theory, the bionics sample possessing similar lotus-leaf-like surface structure on the aluminum alloy was designed and fabricated successfully. The water contact angle was about 153 ± 2°, sliding angle less than 5°, and the water contact time was 13.4 ms on the surface of bionics sample, which presented excellent superhydrophobic property, and achieved the aim of bionic design. Microsc. Res. Tech. 79:712-720, 2016. © 2016 Wiley Periodicals, Inc.

Antifatigue properties of dragonfly Pantala flavescens wings.

The wing of a dragonfly is thin and light, but can bear high frequent alternating stress and present excellent antifatigue properties. The surface morphology and microstructure of the wings of dragonfly Pantala flavescens were observed using SEM in this study. Based on the biological analysis method, the configuration, morphology, and structure of the vein were studied, and the antifatigue properties of the wings were investigated. The analytical results indicated that the longitudinal veins, cross veins, and membrane of dragonfly wing form a optimized network morphology and spacially truss-like structure which can restrain the formation and propagation of the fatigue cracks. The veins with multilayer structure present high strength, flexibility, and toughness, which are beneficial to bear alternating load during the flight of dragonfly. Through tensile-tensile fatigue failure tests, the results were verified and indicate that the wings of dragonfly P. flavescens have excellent antifatigue properties which are the results of the biological coupling and synergistic effect of morphological and structural factors.