Many advanced materials are designed for separation of immiscible oils/ organic solvents and aqueous solutions, including poly(vinylidene fluoride) (PVDF) based materials with superwettability. However, due to the limited solubility of PVDF, techniques (e.g., phase inversion and electrospinning) often involve the use of toxic organic solvents. Here a facile organic solvent free method is described to prepare a porous PVDF-MWCNT (multiwalled carbon nanotube) foam using table salt as a sacrificial template. The porous PVDF-MWCNT foam is characterized as superhydrophobic-superoleophilic with good elasticity due to its 3D porosity and low surface energy. The foam exhibits high adsorption capacity to a variety of oils/organic solvents and can be easily reused by squeezing, heating, or releasing in other solvents. More over, the foam is highly resistant toward UV exposure, corrosive aqueous solutions such as acidic, alkaline, salty solutions, and turbulent environ ments, and shows effective oils/organic solvents removal in these complex environments. The continuous separation of immiscible oils/organic solvents and corrosive aqueous solutions with vacuum assistance is also presented. The organic solvent free and reusable PVDF-MWCNT foam is a promising candidate for large scale industrial separation of oils/organic solvents and water in corrosive and turbulent conditions.

Robust superamphiphobic coatings fabricated by a facile chemical deposition and low surface energy modification were coated on both hard and soft materials to repel water and oils.

The preparation of superoleophobic and superhydrophobic surfaces requires surface microgeometries and surface chemistry. In this study, an economical and environmentally friendly electrochemical etching method was developed to prepare superoleophobic and superhydrophobic titanium surfaces. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), energy-dispersive spectroscopy (EDS), and optical contact angle measurements were used to characterize the surface morphologies, crystal structures, chemical compositions, and wettability of the surfaces for both water and oil. The results show that the prepared superoleophobic surface has water, glycerol, and hexadecane contact angles above 150°, with rolling angles of only 1–2°. Analysis of the electrolyte, the reaction process, and the products demonstrates that the proposed method is inexpensive and environmentally friendly. The effects of electrochemical parameters such as current density, electrochemical etching time, electrolyte temperature, and electrolyte concentration on the surface wettability for water, glycerol, and hexadecane were also investigated. Superoleophobicity and superhydrophobicity can be selectively obtained by varying the electrochemical parameters. The proposed method is believed to be adopted for industrial production of superoleophobic and superhydrophobic titanium surfaces.

Superhydrophobic-superhydrophilic patterned surfaces have attracted more and more attention due to their great potential applications in the fog harvest process. In this work, we developed a simple and universal electrochemical-etching method to fabricate the superhydrophobic-superhydrophilic patterned surface on metal superhydrophobic substrates. The anti-electrochemical corrosion property of superhydrophobic substrates and the dependence of electrochemical etching potential on the wettability of the fabricated dimples were investigated on Al samples. Results showed that high etching potential was beneficial for efficiently producing a uniform superhydrophilic dimple. Fabrication of long-term superhydrophilic dimples on the Al superhydrophobic substrate was achieved by combining the masked electrochemical etching and boiling-water immersion methods. A long-term wedge-shaped superhydrophilic dimple array was fabricated on a superhydrophobic surface. The fog harvest test showed that the surface with a wedge-shaped pattern array had high water collection efficiency. Condensing water on the pattern was easy to converge and depart due to the internal Laplace pressure gradient of the liquid and the contact angle hysteresis contrast on the surface. The Furmidge equation was applied to explain the droplet departing mechanism and to control the departing volume. The fabrication technique and research of the fog harvest process may guide the design of new water collection devices.

Spontaneous pumpless transportation (SPT) of liquids has generated tremendous demands in microfluidic systems and advanced devices. However, the transportation of nonpolar organic liquids on open platforms underwater remains a challenge because most existing SPT systems are only designed for use in air. Here, we report a surface-tension-driven SPT system to transport various nonpolar organic liquids using underwater extreme wettability patterns. The patterns were fabricated with a wedge-shaped superoleophilic track on a superoleophobic background by combining CuCl2 etching, stearic acid modification, and mask-based nitrogen cold plasma treatment. Three types of underwater SPT processes-horizontal transport, tilted transport, and directional transport-were studied experimentally and theoretically. For horizontal SPT and tilted SPT, the capillary force was the main driving force, which depended on the wedge angle of the superoleophilic track. The excellent transportation ability of horizontal SPT of underwater liquid droplets was obtained at a wedge angle of 3-5°. The maximum moving height of organic liquids on the tilted SPT transport was obtained at an angle of 8°. For directional SPT, organic liquids did not drop off in the moving process because of the constraint imposed by surface tension, resulting in the sustained directional transport with long distances and complex trajectories.