Direct printing of anisotropic wetting patterns using aerodynamically focused nanoparticle (AFN) printing

Abstract Micro- and nanoscale structures are of interest in various engineering fields due to their unique properties, such as hydrophobicity. In particular, micro/nano hierarchical structures have been investigated to promote surface hydrophobicity. Here, aerodynamically focused nanoparticle (AFN) printing was used for direct printing of superhydrophobic patterns. As AFN printing is a room-temperature direct printing technique, printed features have a hierarchical structure of two levels; nanoscale porous surface and microscale-printed patterns in three-dimensional structures. Moreover, because it is an additive fabrication technique, the printed pattern is repairable and can be reconfigured as desired. In this study, silver nanoparticles were used to implement a superhydrophobic pattern with a minimum width of tens of microns. The contact angle of water droplets was measured for various patterns, and the effects of nanoscale porosity and pattern interval were investigated. In addition, patterns were designed and fabricated to have anisotropic superhydrophobicity. The experimental results were analyzed and explained with the classical Wenzel and Cassie–Baxter models.