Ultrafast fabrication of rough structures required by superhydrophobic surfaces on Al substrates using an immersion method

Abstract

Superhydrophobic surfaces are commonly fabricated by combining micro/nanometer-scale rough structures and low-surface energy materials. The present work reported a simple, facile, and highly effective method of fabricating the rough structures required by superhydrophobic surfaces. Al plates were first immersed in 1mol/L aqueous CuCl2 solution from several seconds to tens of seconds and then immersed in 1wt.% ethanol solution of fluoroalkylsilane to reduce the surface free energy. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectrophotometry (FTIR), X-ray diffraction (XRD), and contact angle measurements were performed to determine the morphological features, chemical composition, and wettability. The results show that chemical substitution occurs during the immersion process. Rough Cu structures consisting of micrometer-scale particles, submicrometer-scale leaf-like dendrites, and nanometer-scale crystals are obtained on the Al surfaces after immersion as a result of Cu deposition during the chemical substitution reaction. However, after ultrasonic cleaning, rough Al structures consisting of micrometer-scale pits, protrusions, and rectangular-shaped plateaus as well as nanometer-scale step-like structures appear as a result of the removal of Cu deposition and etching during chemical substitution. The shortest immersion times for the fabrication of hierarchical rough Cu structures and Al structures are 1 and 3s, respectively.