Tuning surface wettability for effective oil-water separation, manipulation of ferrofluid droplets and blood contacting medical devices

Abstract

Surface interaction with liquids have gained a lot of attention that enables us to control wetting properties which find applications in self-cleaning, stain free clothing, non-fouling, separation of liquids etc. In this study we tuned surface wettability of different surfaces to showcase potential applications in oil-water separation, manipulation of under liquid droplets and blood contacting medical devices. First, we designed dual superlyophobic surfaces by combining re-entrant texture and appropriate surface energy with recently discovered recyclable polymer. Dual superlyophobic surfaces display both under-water superoleophobicity and underoil superhydrophobicity. Such surfaces are counter-intuitive because typically underwater superoleophobic surfaces require high surface energy and under-oil superhydrophobic surfaces require low surface energy. We fabricated these surfaces using a simple spray coating method that resulted in textured surface with re-entrant structures. The surface energy of the textured surfaces was then modified through plasma treatment. Our surfaces display under-water superoleophobicity for low surface tension liquids liker oils and under-oil superhydrophobicity for high surface tension liquids like water. We envision that our dual superlyophobic surfaces will find applications in membrane separation, antifouling coatings and droplet-based fluidic devices. Second, we developed polyethylene glycol based hydrophilic slippery surfaces by covalently attaching PEG silane via O-Si bonds to hydroxylated surface to form PEG brushes. The hydrophilic slippery surfaces formed are chemically homogeneous with low molecular weight PEG brushes with high grafting density. These surfaces can easily repel high surface tension liquids like water and blood with a tilt angle of 6°. It is envisioned that these surfaces can be effectively used to reduce protein adsorption, platelet adhesion and bacterial adhesion and the use of slippery surfaces can be an ideal approach for designing surfaces for blood-contacting medical devices.