Uniform superhydrophobic surfaces using micro/nano complex structures formed spontaneously by a simple and cost-effective nonlithographic process based on anodic aluminum oxide technology

This paper presents a uniform micro/nano double-roughened superhydrophobic surface with a high static contact angle (CA) and low contact angle hysteresis (CAH). The proposed micro/nano complex structured surfaces were self-fabricated simply and efficiently using a very simple and low-cost nonlithographic sequential process, which consists of aluminum (Al) sputtering, anodization of the Al layer and pore widening, without specific equipment and additional subsequent processes. The wetting properties of the fabricated surfaces were characterized by measuring the static CAs and the CAHs after plasma polymerized fluorocarbon coating with a low surface energy. The measured static CA and CAH were 154 +/- 2.3 degrees and 5.7 +/- 0.8 degrees, respectively, showing that the fabricated double-roughened surfaces exhibit superhydrophobic behaviors clearly. In addition, the proposed double-scaled surfaces at a wafer-level exhibited uniform superhydrophobic behaviors across the wafer with an apparent CA and CAH of 153.9 +/- 0.8 degrees and 4.9 +/- 1.3 degrees, respectively.