Dual-scale artificial lotus leaf fabricated by fully nonlithographic simple approach based on sandblasting and anodic aluminum oxidation techniques

This paper reports a micro/nano dual-scaled artificial lotus leaf that is formed on a silicon substrate by simple and inexpensive fully nonlithographic approach, combining a sandblasting technique and an anodic aluminum oxidation (AAO) process. The proposed dual-scaled surface was demonstrated by covering the sandblasted micro-roughened substrate entirely with nano-scale protuberances, and its surface wettability was characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH). The measurements confirmed that the proposed dual-scaled surface can sufficiently ensure superhydrophobicity in the Cassie wetting regime with a high SCA of 159.4 ± 0.5° and a low CAH of 3.9 ± 0.7°, and the surface wetting properties can be improved greatly compared to those of flat, sandblasted micro-roughened and nano-scale protuberance-arrayed surfaces. Through a dropping test, it was observed that the fabricated dual-scaled surface can ensure its superior water-repellency with various levels of the impact velocity. Finally, a self-cleaning ability of the proposed dual-roughened surface was verified experimentally by observing the dynamic rolling-off behavior of the water droplet on the surface covered with contaminants.