具有串/并联复合离子输运特性的仿生纳米通道的构筑与整流性能

Based on hierarchically branched alumina nanochannels, a serial/parallel composite nanofluidic diode system with experimentally adjustable ion rectification characteristics was fabricated. Using a simple anodization method, we fabricated four two-generation branched alumina nanochannels with 1-2-2, 1-2-3, 1-3-2 and 1-3-3 geometric structures. Among them, if we view each branch node as a diode, its first branch node will be equivalent to one series diode, and its second branch node will be equivalent to multiple parallel diodes. In this case, the circuits of the branched alumina nanochannels with 1-2-2 and 1-2-3 geometric structures are regarded as two parallel diodes and then the third diode in series. Similarly, the ones with 1-3-2 and 1-3-3 geometric structures are considered as three parallel diodes and then connected in series with the fourth diode. However, considering different structures and numbers of the secondary branches of the 1-2-2 and 1-2-3 alumina nanochannels as well as the 1-3-2 and 1-3-3 alumina nanochannels, the four branched alumina nanochannels will ultimately be classified into four nanofluidic diodes with serial/parallel composite characteristic. Accordingly, benefiting from cooperative asymmetry of the first-branched and the second-branched geometries, which affects the surface-charge distribution on inner walls, the branched alumina nanochannels with 1-2-2, 1-2-3, 1-3-2 and 1-3-3 structures exhibit gradually enhanced ionic rectification properties. Further, the rectification ratios of the representative 1-1-2 branched alumina nanochannels increase as the length of the branch channel increases. This indicates that the branch part with stronger ion selectivity plays a decisive role in the rectification characteristics of the entire series/parallel composite nanofluidic diode system. Compared with the previous single ion diode system, this serial/parallel composite nanofluidic diode with geometry-tailorable hierarchically branched alumina nanochannels could not only provide a basic platform to build ionic diode circuitry and more complex nanofluidic devices, but also spark further efforts to simulate the smart ion transport processes of multiple-channel with sparallel/serial mode in living bodies.