3D printing of fluorine‐free omniphobic surfaces

Abstract Omniphobic surfaces have attracted considerable interest in recent years due to their various applications. Such surfaces conventionally require a fluorine‐based surface chemistry with a low surface energy, which is achieved through surface modification using per‐ and polyfluoroalkyl substances (PFAS). However, PFAS, as emerging contaminants, pose serious health risks to humans and wildlife. The discovery of doubly reentrant texture has paved the way for designing fluorine‐free omniphobic surfaces, but current methods for fabricating this unique texture involve complex processes and expensive equipment. In this work, we demonstrate that the simple and inexpensive digital light processing three‐dimensional printing can be used to fabricate not only doubly reentrant but also triply reentrant micropillars. Our printed micropillars with doubly reentrant features display repellency towards liquids with a wide range of surface tensions after surface modification using a hydrocarbon silane. Water and ethanol droplets remain in the Cassie–Baxter state during the entire evaporation process, indicating the robust omniphobicity of our surface. Moreover, the printed micropillars with triply reentrant features exhibit omniphobicity even when the micropillars are composed of hydrophilic resin. Our simple method for achieving fluorine‐free omniphobicity has the potential of facilitating the development of sustainable liquid‐repellent surfaces and the mitigation of PFAS contamination.