Recent Progress on Fluorine-Free Smooth and Textured Surfaces Exhibiting (Super)omniphobicity and Their Future Prospects

In recent years, surface modification designed to easily repel a variety of liquids and allow them to slide off effortlessly has attracted significant attention. These liquids include both polar and nonpolar liquids with a range of surface tensions, as well as emulsions and biological fluids, such as blood. Such multiliquid-repellency is often referred to as "(super)omniphobicity". To achieve (super)omniphobicity, the most common approach has been to roughen the substrate surfaces and subsequently modify them with long-chain perfluorinated compounds (PFCs) to reduce liquid adhesion or limit the contact area between the liquid and substrate, thereby maximizing the apparent/static contact angles (θ_S). Long-chain PFCs possess very low surface energies and have been considered crucial for the development of (super)omniphobic surfaces. Recently, concerns have been raised about the effects of long-chain PFCs on both the environment and human health. Therefore, designs for (super)omniphobic surfaces that do not rely on long-chain PFCs are urgently needed. This review highlights the latest advancements in both textured superomniphobic surfaces (e.g., re-entrant structured surfaces, θ_S > 150°) and smooth, flat omniphobic surfaces (e.g., liquid-like surfaces, θ_S < 150°) that are fabricated using only ubiquitous elements, and without the use of any long-chain PFCs. Each section provides a concise summary of the current research, detailing the underlying basic and guiding concepts, materials, fabrication techniques, resulting static and dynamic dewetting performances, and any additional functionalities. Finally, existing scientific and technical challenges in fundamental research, as well as industrial applications in this promising research field, are discussed, along with potential future directions.