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

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: similar to 150 nm, lattice constant: 420 nm, height: similar to 250 nm) on 2D triangular SiO2 microrod arrays (diameter: similar to 842 nm, lattice constant: 2 mu m, height: similar to 1 mu m), the maximum contact angle (160.4 degrees) 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.