In nanofluidics, the valence numbers of the ions determines their net electrophoretic velocities. In other words, the velocity of an ion in the nano-channel is related not only to its ion mobility but also its ion valence. This enables the sorting function of nanofluidics, which cannot be done in a micro-channel. Therefore, it is possible to do sorting and separation for short strand DNA by using a nanochannel. For the single-molecule DNA application, the final goal is to sequence a strand of genomic DNA in a reproducible and precise result. Similar application can also be found in chromatography, or separation of various ingredients in the solution.