Fabrication of Low and High Adhesion Hydrophobic Au Surfaces with Micro/Nano-Biomimetic Structures

Inspired by plants and animals in nature that show obvious superhydrophobic performance with high or low adhesion, developing artificial ways to mimic these surfaces is meaningful and practical for mankind. In this work, we used a simple, efficient, and highly reproducible method for producing large-area positive and negative lotus and rice leaf topography on Au surfaces based on PDMS, and then the as-prepared surfaces were chemically modified with alkanethiol to enhance hydrophobicity. Surface morphologies of Au surfaces with biomimetic micro/nanobinary textures were examined by SEM and 3D noncontact optical profilometry. Hydrophobic properties of surfaces were characterized by the contact angle and sliding angle between a water droplet and the as-prepared Au surfaces, and the smooth Au surface was provided as a comparison. Results show that both positive and negative biomimetic textures (lotus leaf and rice leaf) were successfully generated on Au surfaces, and Au surfaces with biomimetic textures exhibited improved hydrophobic ability after chemical modification. Adhesion properties between water droplet and Au surfaces with positive and negative biomimetic micro/nanotextures showed nearly opposite performance. An understandable model is proposed to interpret the mechanism which causes the different adhesion performance between Au surfaces with positive and negative biomimetic structures. The strong adhesion is attributed to van der Waals and the capillary force interactions between the biomimetic Au surfaces with negative plant topographies and water droplet.