Fabrication of hierarchical polymer surfaces with superhydrophobicity by injection molding from nature and function-oriented design

A comparison of processes and wettability characteristics was presented for injection molded super-hydrophobic polypropylene surfaces from two fabricating strategies. One is the biomimetic replication of patterns from indocalamus leaf in nature. The contact angle of water sitting on this PP surface was measured as 152 +/- 2 degrees, with comparable wetting behavior to natural indocalamus leaf surface. The other strategy is the fabrication of superhydrophobic structure by combining methods that produce structures at different length scales. Regarding both the machinability of mold inserts and function-oriented design, three micro-quadrangular arrays and one hierarchical micro-nano cylinder array were designed with the goal of superhydrophobicity. Particularly, a simple approach to the fabrication of hierarchical structures was proposed by combining the anodized plate and the punching plate. The function-oriented design targets as superhydrophobicity were all reached for the designed four structures. The measured contact angles of droplet for these structures were almost consistent with the calculated equilibrium contact angles from thermodynamic analysis. Among them, the contact angle of droplet on the surface of designed hierarchical structure reached about 163 degrees with the sliding angle of 5 degrees, resulting in self-cleaning characteristic. The superhydrophobicity of function-oriented designed polymer surfaces could be modified and controlled, which is exactly the limitation of replicating from natural organisms. (C) 2017 Elsevier B.V. All rights reserved.