Dual-Bioinspired Janus Membranes with Asymmetric Superwettability for High-Efficiency Oil–Water Separation and Environmental Remediation

The escalating discharge of petroleum-based contaminants and industrial organic pollutants poses significant threats to global ecosystems and human health, necessitating urgent advancements in sustainable water remediation technologies. To address this challenge, a rationally engineered Janus membrane with asymmetric superwettability was presented, synthesized through a dual-bioinspired fabrication strategy. The membrane was developed via selective surface etching of stainless steel mesh (SSM) substrates using laser etching power gradients, followed by hierarchical functionalization. On the high-power-etched surface, polydimethylsiloxane (PDMS) curing replicated the lotus leaf microstructure, yielding superhydrophobicity (water contact angle: 157.8°). Conversely, the low-power-etched surface was functionalized with chitosan and phytanic acid, hydrophilic modifiers, to emulate the hydrous properties of fish scales, achieving superhydrophilicity with underwater-oil contact angles >148.2°. The resultant PDMS/SSM/CS-PA Janus membrane demonstrated exceptional separation efficiencies (>99.90%) for both oil-in-water and water-in-oil mixtures, coupled with robust cyclic stability (>99.80% efficiency after 50 cycles). Mechanistic analysis revealed that the asymmetric wettability gradient and biomimetic micro/nanoscale architectures synergistically enhanced selective permeation of oil-water mixtures. This work establishes a novel paradigm for designing high-efficient separation materials with potential applications in industrial wastewater treatment and environmental remediation.