title: Under-water superoleophobic glass: unexplored role of the surfactant-rich solvent.
abstract: Preparing low energy liquid-repellant surfaces (superhydrophobic or superoleophobic) have attracted tremendous attention of late. In all these studies, the necessary liquid repellency is achieved by irreversible micro-nano texturing of the surfaces. Here we show for the first time that a glass surface, placed under water, can be made superoleophobic (with unprecedented contact angles close to 180 degrees and roll off angles only a few fractions of 1 degree) by merely changing the surfactant content of the water medium in which the oil (immiscible in water) has been dispersed. Therefore, we propose a paradigm shift in efforts to achieve liquid-repellant systems, namely, altering the solvent characteristics instead of engineering the surfaces. The effect occurs for a surfactant concentration much larger than the critical micelle concentration, and is associated to strong adsorption of surfactant molecules at the solid surface, triggering an extremely stable Cassie-Baxter like conformation of the oil droplets.
authors.affiliation: Micro and Nano-scale Transport Laboratory, Department of Mechanical Engineering, University of Alberta, Edmonton, Canada, T6G 2G8.
authors.forename: Prashant R
authors.initials: PR
authors.lastname: Waghmare
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Das
authors.forename: Sushanta K
authors.initials: SK
authors.lastname: Mitra
mesh_terms: D005898:Glass / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D009821:Oils / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: D009821:Oils; D013501:Surface-Active Agents; D014867:Water