Superhydrophobic and superhydrophilic surfaces with MoOx sub micron structures

Abstract

Presented is an investigation of surface morphology of arrayed MoOx structures with increasing aspect ratios, and their resultant superhydrophillic, and their modified superhydrophobic properties. Molybdenum oxide (MoOx) submicron structures were grown on lithium niobate (LiNbO3) substrates via the thermal evaporation of MoO3 nanopowder at 750°C in a horizontal tube furnace. A mixture of 90% argon and 10% oxygen was introduced into the thermal evaporation tube at flow rate of 1L/min. This resulted in the formation of a white film which consisted of submicron tabular structures. Scanning electron micrographs revealed that the tabular molybdenum oxide grew in arrays 80-100° with respect to the plane of the substrate, with tabular structures with a thickness of approx 0.5 - 1.5μm. Initial testing of MoOx structures revealed that they were extremely super hydrophilic. Such MoOx arrays were coated with fluoropolymer Teflon, deposited using the RF sputtering technique. The addition of a semi-conformal Teflon layer effectively converts the superhydrophilic MoOx layer into a superhydrophobic surface. These superhydrophobic surfaces exhibit contact angles with aqueous media in excess of 150°. Such surfaces can be utilized for the selective adsorption and desorption of protein or pharmacokinetic molecules, with applications in drug delivery and biomedical systems.