Nanopore sensing is nearly synonymous with resistive pulse sensing due to the characteristic reduction of ionic flux during molecular occupancy of a pore, particularly at high salt concentrations. However, conductive pulses are widely reported at low salt conditions wherein electroosmotic flow can be quite significant. Aside from transporting molecules like DNA, we investigated whether electroosmotic flow has other potential impacts on sensing attributes such current enhancements due to the analyte molecule. The overwhelming majority of literature reports counterions as the dominant mechanism of conductive events (a moleculecentric theory for conductive events). Conductive events are not well understood due to the complex interplay between (charged) nanopore walls, DNA grooves, ion mobility, and counterion clouds. Yet, the prevailing consensus of counterions being introduced into the pore by the molecule does not fit well with a growing number of experiments including the fact that proteins can generate conductive events despite having a heterogeneous surface charge. Herein, we demonstrate theory and experiments underpinning the translocation mechanism (i.e., electroosmosis or electrophoresis), pulse direction (i.e., conductive or resistive) and shape (e.g., monophasic or biphasic) through fine control of chemical, physical, and electronic parameters. Results from these studies predict strong electroosmosis plays a role in driving DNA events and generating conductive events due to polarization effects (i.e. a pore-centric theory). We believe these findings will stimulate a useful discussion on the nature of conductive events and their impact on molecular sensing in nanoscale pores.

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关于纳米孔内传导脉冲传感的起源

纳米孔传感几乎是电阻脉冲传感的同义词，因为在分子占据孔期间离子通量的特征减少，特别是在高盐浓度下。然而，导电脉冲在低盐条件下被广泛报道，其中电渗流可能非常显着。除了运输 DNA 等分子外，我们还研究了电渗流是否对传感属性有其他潜在影响，例如由于分析物分子导致的电流增强。绝大多数文献报道反离子是传导事件的主要机制（传导事件的分子中心理论）。由于（带电）纳米孔壁、DNA 凹槽、离子迁移率和反离子云之间的复杂相互作用，导电事件尚不清楚。然而，由分子引入孔中的抗衡离子的普遍共识与越来越多的实验并不吻合，包括尽管蛋白质具有异质表面电荷但仍能产生导电事件的事实。在这里，我们通过对化学、物理和电子参数的精细控制，展示了支持易位机制（即电渗或电泳）、脉冲方向（即导电或电阻）和形状（例如单相或双相）的理论和实验。这些研究的结果预测，由于极化效应（即以孔为中心的理论），强电渗在驱动 DNA 事件和产生传导事件中发挥作用。