Size-based continuous-flow directional control of DNA with a nano-pillar anisotropic array

A size-based pre-fractionation chip applicable for enrichment of macromolecules in biological samples is proposed. In this chip, a fractionation unit with a nano-pillar anisotropic array, which functions as sieve meshes, is installed at a bi-forked junction. The mesh sizes are close to the diameters of macromolecules and vary according to the direction to the main and branch exit channels. This fractionation unit provides continuous-flow fractionation without both the dilution of samples and the limitations with the sample loading volume. Additionally, the small channel-volume, which is characteristic of chip-based systems, can reduce sample loss. Using nanometer-scale fabrication technology, we fabricated the chips and demonstrated the flow direction control of DNA molecules.