Superhydrophobic surfaces have long faced challenges in repelling low-surface-tension liquids like oil and alcohol, limiting their practical applications. Over the past few years, researchers have been actively looking for new alternatives to overcome this issue. Recently, superomniphobic surfaces have attracted significant interest due to their ability to repel both high- and low-surface-tension liquids. Compared with superhydrophobic surfaces, superomniphobic surfaces provide enhanced liquid repellency, making them more suitable for industrial and real-world applications. This Review explores the recent advancements in the fabrication of superomniphobic surfaces. Three basic wetting principles, Young's, Wenzel's, and Cassie-Baxter's equations, are discussed. The vital role of low surface energy and high surface roughness of hierarchical and re-entrant structures in achieving a steady Cassie-Baxter state that has a low contact area between the solid surface and liquid droplet is emphasized. Additionally, a comprehensive description of various fabrication techniques, characterizations, and practical applications of superomniphobic surfaces is provided. Finally, the challenges and future prospects regarding this research area are addressed. This comprehensive review aims to inspire researchers to refine and enhance current development methods of superomniphobic surfaces and stimulate further exploration in the research field.

Titanium(IV) oxide (TiO₂) nanoparticles have been incorporated into mixed matrix membranes (MMMs) to improve gas separation performance. However, TiO₂ nanoparticles tend to agglomerate due to high surface energy and van der Waals forces. This leads to precipitation which causes the formation of non-homogeneous MMM morphology. In this study, the effect of octaisobutyl polyhedral oligomeric silsesquioxane (POSS) addition on TiO₂/polysulfone MMM was investigated. The aims are to enhance gas separation performance whilst preventing agglomeration of TiO₂ nanoparticles. The results demonstrated that inclusion of POSS as dispersant increases MMMs’ CO₂/CH₄ selectivity and permeance, possibly due to less void formation and more evenly distributed pore structure. For example, synergistic addition of 5 wt% TiO₂ and 5 wt% POSS increased the CO₂/CH₄ selectivity up to 390% compared to MMM without POSS. This is supported by elemental mapping of titanium which revealed that POSS successfully dispersed TiO₂ nanoparticles and prevented aggregation. TiO₂-POSS/PSf MMMs also retained their favorable thermal stability.

Membrane gas-liquid separation technology has gained great interest in membrane desalination, distillation, and gas absorption attributed to its good operation flexibility, small footprint and high specific interfacial area. Membrane acts as the non-selective barrier between gas and liquid solvent by allowing the diffusion of gas molecules via pressure difference. Currently used membrane is susceptible to pore wetting at high operational pressure, transforming its non-wetted condition to partially wetted and wetted mode. Such condition introduces additional mass transfer resistance to gas molecules, leading to the poor removal flux. In order to alleviate the wetting tendency, membrane hydrophobicity needs to be enhanced. In this work, highly hydrophobic PVDF-HFP membrane of improved anti-wettability properties was synthesized via non-solvent induced phase separation. The effect of polymer concentration and coagulation medium on membrane wettability were studied. The results revealed that PVDF-HFP membrane of 10wt% polymer concentration presented high water contact angle of 100.4°. By changing water to ethanol as coagulation medium, membrane exhibited a symmetric nodular structure which enhanced water contact angle by 20.3% to 130.5º. To further improve membrane hydrophobicity, modified silica (MS) nanoparticles were used as surface modifier in coagulation bath. When the nanoparticles content increased from 0g to 2g, the water contact angle of the PVDF-HFP modified membrane increased significantly from 130.5° to 163.1°. As a result, the liquid entry pressure of the membranes increased gradually from 0.58bar to 3.38bar with MS incorporation. This disparity in membrane anti-wettability is due to the increase in surface roughness and reduction in surface energy. Additionally, the modified membrane at MS loading of 2g showed high porosity at 78%, which is adequate to provide increased mass transfer rate between gas and liquid solvent.