Controlling DNA translocation through gate modulation of nanopore wall surface charges.

One major challenge of nanopore-based DNA sequencing technology is to find an efficient way to reduce DNA translocation speed so that each nucleotide can reside long enough in the pore for interrogation. Here we report the electrical tuning of DNA translocation speed by gate modulation of nanopore wall surface charges. We find that native surface-charge-induced counterions in the electroosmotic layer substantially enhance advection flow of fluid, which exerts stronger dragging forces on the translocating DNA, and thereby lowering the DNA translocation speed. We propose a feedback device architecture to regulate DNA translocation by modulating the effective wall surface charge density σw*via lateral gate voltages--at the beginning, a positive gate bias is applied to weaken σw* in order to enhance the capture rate of DNA molecule; upon detection of ionic current variance indicating DNA has been driven into the nanopore, gate bias is turned to be negative so that σw* is reinforced and DNA translocation is retarded. We show that a gate electric field can dramatically decrease the DNA translocation speed at a rate about 55 μm/s per 1 mV/nm.