Oil contaminated water is a common problem in the world, thus to effectively separate water and oil is an urgent task for us to resolve. By control of surface wettability of a solid substrate, both superhydrophobicity and superoleophilicity on a film can be realized, which is necessary for water and oil separation. Here we report a stable superhydrophobic and superoleophilic ZnO-coated stainless steel mesh film with special hierarchical micro/nanostructures that can be used to separate a water and oil mixture effectively. Namely, the film is superhydrophobic and water cannot penetrate the mesh film because of the large negative capillary effect, while the film is superoleophilic and liquid paraffin oil can spread out quickly and permeate the mesh film spontaneously due to the capillary effect. A detailed investigation indicates that microscale and nanoscale hierarchical structures and the appropriate size of the microscale mesh pores on the mesh films play an important role in obtaining the excellent water and oil separation property. This work provides an alternative to current separation meshes and is promising in various important applications such as separation and filtration, lab-on-a-chip devices and micro/nanofluidic devices.

EWOD was investigated from wetting to superwetting with six basic fluid systems. Each fluid system has developed special technologies for functional applications owing to the different interactions among solid, liquid and gas phases.