Beetle-inspired single-feed and dual-phase segregated oil-water separation strategy with interdigital Janus microfiber membrane

The development of conventional oil-water separation systems faces fundamental challenges rooted in the monofunctional affinity — specific hydrophilicity or lipophilicity, and modifying conditions, significantly impeding the separation of various oil/water mixtures. Bio-inspired by a beetle's hydrophilic and hydrophobic architecture for water-capturing, an innovative single-feed and dual-phase segregated separation strategy in this research was developed through controlled mechanical grinding polymer fibers, yielding two microfiber domains and a Janus boundary —holding opposite and complementary Janus wettability. Subsequently, an interdigital Janus microfiber membrane (IJMM) was engineered through a filtration deposition to integrate two wettability microfiber domains, achieving universal coverage of the Janus boundary on the membrane surface. Remarkably, the IJMM completed exceptional efficiency in the continuous single-feed and dual-phase segregated separation of the three-phase system involving light oil, water, and heavy oil, achieving separation efficiencies of 94.0 ± 1.1 % (light oil), 96.7 ± 1.5 % (water), and 93.0 ± 2.2 % (heavy oil) without modifying conditions. Notably, a mixed oil (MO) with a density comparable to water was formulated for oil-water separation with 98.0 ± 0.5 % for water and 96.8 % ± 0.6 % for MO separation efficiencies, which replicated the non-stratified conditions. Consequently, this work establishes a membrane via integrating two opposite and complementary Janus wettability microfibers, presenting a novel strategy for the continuous various oil-water separation, offering promising prospects and universal platform for multiphase separation challenges, even non-stratified conditions. • Eco-friendly synthesis of two opposite wettability microfiber systems are prepared. • Janus domains with opposite and complementary wettability architecture are constructed. • Programmable interdigital boundary-enhanced separation is spatially engineered. • Autonomous and continuous three-phase systems separation capability. • Density-neutral oil/water systems separation paradigm without gravity-dependent.