Wettability-gradient bilayer nanofiber membranes for regulating microbial, moisture microenvironment and directional water transport in food preservation

Postharvest quality retention relies on packaging materials capable of concurrently regulating microbial and moisture microenvironments. In this study, an asymmetric bilayer nanofiber membrane was engineered to integrate natural deep eutectic solvents (NADESs) and polyphenol-functionalized silver nanoparticles (PF-Ag) for coordinated regulation of these preservation pathways. NMR confirmed the hydrogen-bonded structure of the NADESs, while SEM, TEM, and FTIR verified the morphology and surface chemistry of PF-Ag. These active units were embedded within hydrophilic and hydrophobic fibers and assembled into a wettability-asymmetric bilayer via electrospinning. The NADESs improved interfacial compatibility and fiber uniformity, whereas PF-Ag imparted effective microbial suppression and radical-quenching capacity. The bilayer architecture also enabled directional moisture transport, thereby establishing a tightly regulated microbial and moisture microenvironment. Compared with single-layer or additive-free controls, the membrane exhibited markedly improved mechanical stability, gas barrier performance, and moisture management. Applied to fresh prunes, the membrane effectively slowed microbial spoilage, mitigated surface moisture accumulation, stabilized internal gas composition, and extended shelf-life to 15 days at ambient temperature. This work elucidates a synergistic NADES–PF-Ag strategy for microenvironment-responsive bilayer nanofibers and provides a promising platform for sustainable postharvest packaging.