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

Abstract

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 superhydrophobicity 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.

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

“…More recently, researchers utilized stimuli‐responsive materials to fabricate controllable oil–water separators that can tackle more challenging problems . Stimuli introduced to control the separation can be categorized as physical signals, including temperature, light, voltage, magnetic field, pressure, and chemical signals, such as pH, Hg ion, gas molecules, ammonia . Xin et al fabricated a TiO 2 doped PVDF nanofiber, and the smart membrane with microscale pores was obtained by electrospinning of the special nanofiber (Figure g,h).…”

“…More recently, researchers utilized stimuli-responsive materials to fabricate controllable oil-water separators that can tackle more challenging problems. [198,202] Stimuli introduced to control the separation can be categorized as physical signals, including temperature, [219,220] light, [219,221,222] voltage, [223,224] magnetic field, [225,226] pressure, [227] and chemical signals, such as pH, [228][229][230] Hg ion, [231] gas molecules, [232] ammonia. [201,233] Xin et al [221] fabricated a TiO 2 doped PVDF nanofiber, and the Small 2020, 16,1903849 Figure 11.…”

External‐Field‐Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

“…[139] Recently, we also achieved electroresponsive selective water permeation through a root-like polyaniline nanofiber-coated mesh for oil/water separation. [140] Electroresponsive oil/water separation can be achieved based on the wettability to water transition from the Cassie state to the Wenzel state. During separation, oil adhesion to the porous substrate can also be reduced for rapid separation under an electric field.…”

Multiple Liquid Manipulations on Patterned Surfaces with Tunable Adhesive Property

“…Superhydrophobic surfaces have received significant attention for their promising applications such as self‐cleaning materials, microdroplet transportation, antireflection, and oil–water separation . The adhesion of liquid droplets on surfaces plays a crucial role in determining the dynamic properties of the droplets .…”