Wettability-Patterned Surfaces for Management of Low Surface Tension Liquids

Superhydrophobicity (extreme repellency to water) has been an extensively studied topic in recent years. Generally, it is easy to make a surface superhydrophobic as water has a relatively high surface tension (72 mN/m), but it can become difficult to prepare surfaces which can repel low surface tension liquids such as oils and fuels with surface tensions below 40 mN/m. Here, we present a robust, fluorinated material system which can be easily sprayed onto a substrate and is capable of repelling low surface tension liquids (down to 23.8 mN/m). Certain regions of these superoleophobic (extreme repellency to oils) coatings are made superoleophilic through laser processing. After laser processing, the wettability-patterned substrates are then used to passively manage and transport low surface tension liquids. This is achieved by harnessing surface tension forces which arise from the spatial contrast of surface energy between superoleophobic/superoleophilic domains of the substrate. In this work, we demonstrate and study the liquid transport dynamics (e.g. velocity, acceleration) of several oils (varying surface tension and viscosity) on open-air, wettability-patterned substrates through high-speed image analysis.