(744c) Towards Robust Hydrophobic and Oleophobic Surfaces

Super liquid-repellent surfaces have piqued the interest of many commercial and academic researchers over the past decade. Generally these surfaces have a texture that resists penetration of the liquid into the substrate topography, allowing droplets to sit on a composite (solid-liquid-air) interface. Liquid droplets on these non-wettable surfaces are typically characterized by a high apparent contact angle and low contact angle hysteresis. Unfortunately many such surfaces described in the literature are of limited utility in applications due to poor mechanical properties, optical opacity, expensive fabrication procedures, and/or non-robust repellency against low surface tension liquids (e.g., oils). Here we describe the development of replica molding processes to prepare crosslinked elastomeric substrates comprised of polysiloxanes or perfluoropolyethers with submicron re-entrant surface texture. Essential steps in this protocol include the preparation of a master mold using photolithographic techniques, filling the mold and subsequently curing the crosslinkable oligomers, and releasing the elastomeric replica from the template. Substrates with a range of reentrant texture feature sizes and spacings are prepared and the wettabilities of these surfaces are probed using a variety of high (e.g., water) and low (e.g., hexane) surface tension liquids.