Biomimetic Hydrophobic Surfaces with Low or High Adhesion Based on Poly（vinyl alcohol） and SiO2 Nanoparticles

Superhydrophobic surfaces are often found in nature, such as plant leaves and insect wings. Inspired by superhydrophobic phenomenon of the rose petals and the lotus leaves, biomimetic hydrophnbic surfaces with high or low adhesion were prepared with a facile drop-coating approach in this paper. Poly（vinyl alcohol） （PVA） was used as adhesive and SiO2 nanoparticles were used to fabricate surface micro-structure. Stearic acid or dodecafluoroheptyl-propyl-trimethoxysilane （DFTMS） were used as low surface energy materials to modify the prepared PVA/SiO2 coating surfaces. The effects of size of SiO2 nanoparticles, concentration of SiO2 nanoparticle suspensions and the modifications on the wettability of the surface were investigated. The morphology of the PVA/SiO2 coating surfaces was observed by using scanning electron microscope. Water contact angle of the obtained superhydrophilic surface could reach to 3°. Stearic acid modified PVA/SiO2 coating surfaces showed hydrophobicity with high adhesion. By mixing the SiO2 nanoparticles with sizes of 40 nm and 200 nm and modifying with DFTMS, water contact angle of the obtained coating surface could be up to 155° and slide angle was only 5°. This work provides a facile and useful method to control surface wettability through changing the roughness and chemical composition of a surface.

Recent advances in preparation of metallic superhydrophobic surface by chemical etching and its applications

In the past few decades,inspired by the superhydrophobic surfaces(SHPS)of animals and plants such as lotus leaves,rose petals,legs of water striders,and wings of butterflies,preparing metal materials with metallic SHPS(MSHPS)have attracted great research interest,due to the great prospect in practical applications.To obtain SHPS on conventional metal materials,it is necessary to construct rough surface,followed by modification with low surface energy substances.In this paper,the action mechanism and the current research status of MSHPS were reviewed through the following aspects.Firstly,the model of wetting theory was presented,and then the progress in MSHPS preparation through chemical etching method was discussed.Secondly,the applications of MSHPS in self-cleaning,anti-icing,corrosion resistance,drag reduction,oil-water separation,and other aspects were introduced.Finally,the challenges encountered in the present application of MSHPS were summarized,and the future research interests were discussed.

Preparation of a biomimetic superomniphobic hierarchical structure and analysis of droplet wettability

In this study,a bioinspired hierarchical structure was formed with superomniphobicity on a 7075 aluminium alloy using laser ablation.The morphology and wetting characteristics of the biomimetic sample surface were characterised using scanning electron microscopy,laser confocal microscopy,and contact angle measurements.The effect of the liquid properties and surface structures on the rolling behaviour was investigated.The results suggest that the fabricated biomimetic sample surface was a hierarchical structure.The prepared sample had superomniphobicity and low adhesion properties,and the contact angles of six different liquid droplets on the sample surface reached or approached 150°.Specifically,the largest contact angle was 152°,and the average rolling angle was 7.7°.This multi-hydrophobic surface provides a valuable reference for the research study and use of a variety of solid–liquid contacts.