Lotus leaf and shark skin-inspired micro-, nano-, hierarchical superhydrophobic surfaces for anti-fouling applications

Fouling, the accumulation and adhesion of unwanted contaminants, is a serious issue around the world in many aspects including industrial transport, marine ecological environment, maintenance of infrastructures, etc. which costs hundreds of millions of dollars and lots of manpower and material resources. Multiscale hierarchical surface structures of superhydrophobic surfaces possess various intriguing properties which provides new platforms for fabricating artificial anti-fouling surfaces. In particular, lotus leaf and shark skin with their unique micro-, nano-, hierarchical surfaces structures are highlighted as emerging tools for anti-bacterial, anti-dust, anti-corrosion, anti-icing, drag reduction applications and so on. In this review, we first provide basic information on two famous superhydrophobic states. After that we outlined the biological models and applications of lotus leaf and shark skin respectively. The self-cleaning effect of superhydrophobic lotus leaf due to their multiscale hierarchical surface structures is discussed after which anti-bacterial applications with three kinds of mechanisms and self-cleaning properties are outlined. Biological models of superhydrophobic shark skin are presented followed by their real-life applications in aircrafts and turbine blades. In addition, we discuss the potential drawbacks of recent biomimetic anti-fouling superhydrophobic surfaces like the loss of anti-fouling hydrophobic materials, adaptability to extreme environments, production and use costs and other problems as well as the possibilities of combine superhydrophobic structures and materials with high temperature resistance, oxidation resistance and other characteristics in order to be applied in more industries fields.