Solution-processed fabrication of superhydrophobic hierarchical zinc oxide nanostructures via nanotransfer printing and hydrothermal growth

In this report, we present a solution-based process to fabricate hierarchical ZnO nanostructures by a sequential nanoimprint process and hydrothermal reaction. Micro- or mesoscale ZnO patterns are first fabricated by solution -processed nanotransfer printing using colloidal ZnO nanoparticles. Nano-scale ZnO nanorods are then hydrothermally grown on the surface of microstructures to fabricate the hierarchical architectures. The ZnObased hierarchical structures exhibited superior superhydrophobic properties with very small sliding angle (contact angle > 150 degrees, sliding angle < 4 degrees). A solution-based process using mild chemical reagents enables ZnO hierarchical structure to be fabricated on various types of substrates, including Si, glass, flexible polymer substrates, metal foils, curved surfaces, and even on the surface of LED devices, without significant damage to the substrate. This ability indicates that this fabrication method of superhydrophobic hierarchical surfaces can be potentially utilized to fabricate self-cleaning surfaces for many industrial applications, such as solar cell panels, building materials, and electronic devices.