Design of superhydrophobic pillars with robustness

Superhydrophobic surfaces have huge applications in wetting fields. However, compared with natural biological surfaces, artificial superhydrophobic surfaces still show serious deficiencies in the theoretical design and durability. In this work, a robust superhydrophobic surface consisting of a regular array of square pillars with secondary structures on the sidewalls was prepared using low-speed wire electrical discharge machining. We developed the design criteria of regular arrays of square pillars for achieving superhydrophobicity based on interface characteristics and force balance. A series of samples were also prepared to validate the design criteria. The results indicate that the overlap part between the theoretical superhydrophobicity region before and after abrasion leads to stable superhydrophobicity. In addition, specific surfaces transform from the Wenzel state to the Cassie state after abrasion and the contact angle shows a large increase. The design criteria based on the research of predecessors are useful to design superhydrophobic surfaces with robustness.