Slowing down DNA translocation velocity using a LiCl salt gradient and nanofiber mesh

Abstract

Solid-state nanopores are considered an attractive basis for single-molecule DNA sequencing. At present, one obstacle to be overcome is the improvement of their temporal resolution, with the DNA molecules remaining in the sensing volume of the nanopore for a long period of time. Here, we used a composite system of a concentration gradient of LiCl in solution and a nanofiber mesh to slow the DNA perforation speed. Compared to different alkali metal solutions with the same concentration, LiCl can extend the dwell time to 20 ms, five times longer than NaCl and KCl. Moreover, as the concentration gradient increases, the dwell time can be tuned from dozens of milliseconds to more than 100 ms. When we introduce a nanofiber mesh layer on top of the pore in the asymmetric solution, the DNA molecules get retarded by 162–185 μ s/nt, which is three orders of magnitude slower than the bare nanopore. At the same time, because the molecule absorption region becomes larger at the pore vicinity, the higher molecule capture rate improves the detection efficiency.