Nanotextured Surfaces with Underwater Anisotropic Sliding Resistance for Oil Transfer and Coalescence

Underwater oil droplet manipulations have attracted considerable attentions due to the increasing need of miniature organic reactions. In this work, nanotextured surfaces (underwater superoleophobic) patterned with smooth regions (underwater oleophilic) was prepared via simple through-mask alkalinity oxidation. Relationship between underwater sliding resistance of oil droplets and the pattern shape/size was investigated. Results indicate that the modified Furmidge equation with correction coefficient can be well applied to predict the underwater sliding resistance; underwater anisotropic sliding, which means sliding resistance varies with sliding directions, is readily achievable by design of Y-shaped and straight line pattern. With the help of gravity, the anisotropic sliding resistance can guide oil droplets to move exactly along the line pattern; and by linearly moving surfaces with line patterns, underwater oil droplet transfer and coalescence were realized. This strategy of underwater oil droplet manipulations may have promising applications in the development of new miniature platform for organic reactions.