Durable, scalable, and tunable omniphobicity on stainless steel mesh for separation of low surface tension liquid mixtures

Abstract

Surface repellency to high and low surface tension (LST) liquids has a wide range of commercial applications such as non-fouling, self-cleaning and separation of liquids. However, little research has been achieved to control surface repellency to LST liquids due to difficulty of developing re-entrant surface curvatures. Here, we report an effective method to control surface repellency of stainless steel meshes for liquids that have LST. We used electrochemical etching followed by hydrophobic coating where adjusting the voltage and duration of electrochemical etching controllably cover the mesh surfaces with nanoscale re-entrant structures. Variation in re-entrant surface curvatures determines the mesh's sensitivity to liquid-vapor surface tension, and changed the apparent contact angles and sliding angles for LST liquids. The difference in sensitivity of surface tension of mesh was exploited to rapidly separate liquids in binary mixtures of general solvents. The meshes achieve fast separation, and can be reused. This method to provide omniphobicity is compatible with large-scale production.