Magnetic field actuated manipulation and transfer of oil droplets on a stable underwater superoleophobic surface.

The transport of fluids at functional interfaces, driven by the external stimuli, is well established. The lossless transport of oil-based fluids under water remains a challenge, however, due to their high stickiness towards the surface. Here, a superhydrophilic and underwater superoleophobic tri-phase water/oil/solid nanoarray surface has been designed and prepared. The unique tri-phase surface exhibits underwater superoleophobic properties with an extremely low stickiness towards oil-based fluids. The magnetic-field-driven manipulation and transport of oil-based magnetic fluids are demonstrated under water, which opens up a new pathway to design flexible and smart devices for the control and transfer of liquid droplets by using tri-phase systems.