Electric Field Induced Switchable Wettability to Water on the Polyaniline Membrane and Oil/Water Separation

Smart surfaces with responsive wettability to external stimulus have attracted considerable attention especially in oil/water/solid interface, whereas there still remain challenges of response in situ, low voltage, and stable substrate. Here, a strategy is proposed to achieve the electric field induced water selectively permeation for oil/water separation based on the stainless steel mesh coated with root-like polyaniline nanofibers fabricated by emulsion polymerization. Such micro/nanoscale hierarchical-structured polyaniline mesh is superhydrophobic and underwater superoleophobic, while its super-hydrophobicity can turn to hydrophilicity at 160 V and can further selectively filter water at 170 V. As a result, the electric field induced oil/water separation is realized as long as the electric capillary pressure (ECP) is larger than the hydrostatic pressure of the membrane to water, i.e., ECP induced wettability to water transition. The mesh shows low underwater oil-adhesion force and the anti-corrosion of polyaniline, indicating that the mesh could keep working under severe environment during the practical application. Thus, this work is promising in the application of controllable oil/water separation and will also be beneficial to the study of smart filtration, microreactors, and microfluidic devices.