Superhydrophobicity analysis of micro stereolithography-based 3D printed microstructures

Superhydrophobic surfaces have a widespread range of applications, starting from microfluidics to energy, due to their self-cleaning and drag-reducing properties. This study aims to 3D print structures reaching static contact angles (CA) in the superhydrophobic range using readily available materials and simple experimental methods, and to offer quantitative insights for future scalable fabrication of water-repellent surfaces by investigating the impact of geometry, spacing, and surface coating on the wettability of 3D-printed microstructures. Five geometry types, i.e., cone, cylinder, pyramid, mushroom, and square micropillars, with a variable center-to-center spacing ranging from 40 to 100 µm, were designed, fabricated via projection-micro stereolithography (PµSLA), coated with a fluorosilane solution, and finally characterized by scanning electron microscopy (SEM) imaging and contact angle (CA) measurements. Surface geometry alone proved incapable of granting superhydrophobicity. The conical and pyramidal micropillars exhibited CAs exceeding 164° at a 40 µm spacing after fluorosilane coating, thereby significantly enhancing water repellency. Larger spacings clearly reduced the CAs and thus the superhydrophobicity, highlighting the importance of optimal geometry–spacing pairings to maintain extreme aquaphobicity.