The origin of the voltage dependence of conductance blockades from DNA translocation through solid-state nanopores

Abstract

Understanding the origin of ionic conductance modulation of nanopore sensors is important for achieving the precise measurement of analytes at a single molecule level. Most reported model of the amplitude of conductance blockades under high ionic strength is based on geometrical considerations and independent of applied voltage. Here, we present the intriguing increase of measured conductance blockades with applied voltage, which is also influenced by pore diameter and length. Through a series of numerical simulations, it is found that electroosmotic flow (EOF) and ionic concentration polarization (ICP) lead to the fact that applied voltage impacts ionic conductance. The ICP causes the suppression of electric field and the ion enrichment inside the pore, while the EOF depletes the ion concentration in the pore. DNA translocation can enhance the effects of ICP and EOF due to its strongly charged surface, resulting in the voltage dependent conductance blockades. We also have calculated the changes in conductance blockades over voltage for different sized pores. These results offer a valuable reference for nanopore sensor design.