Superhydrophobicity of 2D SiO2 hierarchical micro/nanorod structures fabricated using a two-step micro/nanosphere lithography

Abstract

In this study, dual-triangularly patterned micro/nanorod hierarchical structures were fabricated using a simple combination of the microsphere lithography–reactive ion etching (RIE) process and the nanosphere lithography–RIE process in order to fabricate superhydrophobic surfaces. For the comparison of the wetting properties of the various hierarchical structures, the micro/nanorod geometries were controlled by changing the diameter of the microrod and/or nanorod under equal lattice constant and height conditions. Through the fabrication of two dimensional (2D) triangular SiO₂ nanorod arrays (diameter: ∼150 nm, lattice constant: 420 nm, height: ∼250 nm) on 2D triangular SiO₂ microrod arrays (diameter: ∼842 nm, lattice constant: 2 μm, height: ∼1 μm), the maximum contact angle (160.4°) of the SiO₂ micro/nanorod hierarchical structures was obtained via the subsequent coating of fluoroalkylsilane, leading to a strong superhydrophobicity. The facile two-step sphere lithography for the fabrication of superhydrophobic hierarchical structures on large scale glass wafers (2 inch) demonstrated that there are potential applications in the fields of microfluidic devices, lab-on-a-chip devices, and biological sensors.