The Origin of Conductive-Pulse Sensing Inside a Nanopore and the Role of Electro-Hydrodynamics

Despite the highly negatively charged backbone of DNA, electroosmotic flow (EOF) within a nanopore can lead to DNA travelling opposite to electrophoretic force at low ionic strengths. However, EOF-pumping and its role in producing current-enhancing events is ambiguous due to the complicated interactions between nanopore walls, DNA grooves, ion mobility, and counterion clouds. Here, we discuss how current-enhancing DNA events could be the result of a flux imbalance between anions and cations. The contributing factors for driving a flux imbalance within a nanopore include pore size, voltage bias, and type of alkali chloride electrolyte. Once the mechanism behind conductive events is established, the physics of transducing a DNA translocation into an electrical signal can be further exploited for improving DNA sequencing and, more broadly, bio-sensing.