Electrospun dual-layer core-shell Janus membranes for unidirectional water transport and biphasic thymol release

The development of Janus nanofibrous membranes represents a promising strategy for advanced moisture management and multifunctional materials. However, the practical application of biobased functional agents is often limited by their rapid release and short functional duration. To address this challenge, a novel dual-layer Janus nanofibrous membrane with dual core-shell structures was proposed by sequential coaxial electrospinning. The asymmetric structure consists of a hydrophobic inner layer composed of poly(lactic acid) (PLA) encapsulating thymol (THY), and a hydrophilic outer layer incorporating poly(vinyl alcohol) (PVA) and THY into poly(ethylene oxide)/chitosan (PEO/CS). Compared to the conventional Janus membranes with single structural nanofiber, PEO/CS@PVA/THY-PLA@THY (PCPT-PT) achieves biphasic release of THY through a hierarchical design integrating a dual-layer structure with core-shell fibers in both layers. CS and THY localized in the inner-side of polymer provide an initial rapid diffusion for immediate antibacterial action, while the THY encapsulated deeply in both layers ensures a biphasic and sustained release for prolonged efficacy. The membrane exhibits robust mechanical properties, with a dry tensile strength of 4.76 ± 0.21 MPa and a wet tensile strength of 1.67 ± 0.13 MPa, a high swelling ratio of 765.2% that enables efficient unidirectional moisture management, broad-spectrum antibacterial activity against both Escherichia coli and Staphylococcus aureus, and excellent antioxidant performance, with a DPPH radical scavenging rate of 79.2 ± 1.5% and an ABTS radical scavenging rate of 99.92 ± 0.08%. This work provides a facile strategy for constructing multifunctional Janus membranes, showing great application potential in active food packaging, advanced moisture-wicking smart textiles and bioactive material substrates.