Janus Fiber-Based Membrane for Humid Condition Filtration with Concurrent Air Filtration and Directional Water Transport

Airborne particulate matter (PM) poses a serious threat to public health. Conventional air filters often suffer from excessive weight and an inherent trade-off between filtration efficiency and air permeability. Additionally, moisture management in the microenvironment between the filter and skin is frequently overlooked, compromising long-term wearing comfort. In this study, we present a multifunctional Janus fiber-based membrane composed of cellulose acetate (CA) and thermoplastic polyurethane (TPU), fabricated via a novel eccentric core–shell electrospinning technique and further integrated with a welded ultrafine TPU nanofiber network. The resulting CA/TPU Janus-TPU Net membrane features a hierarchical structure that enables efficient graded filtration, excellent air permeability, and directional water transport. Specifically, it achieves outstanding filtration efficiencies (99.1% for PM 0.3, 99.4% for PM 1.0, and 99.9% for PM 2.5 ) at a low pressure drop (87 Pa), along with a high directional water transport capacity (819%). The membrane also maintains excellent filtration performance under high airflow velocities, elevated particle concentrations, and humid conditions. These combined properties make it a promising filter core for personal protective equipment (PPE) and next-generation breathable and moisture-managing fibrous membranes.