A superstable, flexible, and scalable nanofluidic ion regulation composite membrane.

Two-dimensional layered membranes with high and stable ion transport properties have various applications in nanofluidic devices; however, their construction remains a considerable challenge. Herein, we develop a superstable aramid nanofiber/graphite composite membrane with numerous one-dimensional and two-dimensional nano-confined interspaces for ultrafast ion transport. The fabricated flexible and scalable membrane exhibits high tensile strength (∼115.3 MPa) even after immersion in water for 90 days. Further, the aramid nanofiber/graphite conductor features the surface-charge-governed ion transport behavior. The ionic conductivity of the membrane at a low potassium chloride concentration of 10 mol/L can be enhanced by 16 times that of the bulk counterpart. More importantly, its structure and ionic conductivity remain unchanged even after immersion in different harsh solutions (e.g., acid, base, and ethanol) for over 30 days. Molecular dynamics simulations reveal that the superstability of the membrane is attributable to the robust interchain interactions within the aramid nanofibers and the strong interfacial interactions between the aramid nanofibers and graphite nanosheets. This study highlights the superior structural stability of the proposed flexible and scalable aramid nanofiber/graphite composite membrane, which could be employed in advanced nanofluidic devices for application under extreme working environments.