不带电纳米孔中的几何诱导选择性和单向电渗
Geometrically Induced Selectivity and Unidirectional Electroosmosis in Uncharged Nanopores
摘要：
对纳米孔中正离子和负离子的选择性通常与电渗流相关联，电渗流的控制在几种微纳米流体技术中是关键的。选择性传统上被理解为改变孔腔中离子分布的表面电荷的结果。在这里，我们提出了一个纯粹的几何机制，诱导离子选择性和电渗流在不带电的纳米孔，我们测试它通过分子动力学模拟。我们的方法利用电荷的积累，由外部电场驱动，在同轴腔，装饰膜接近孔入口。的选择性被证明取决于所施加的电压和结果被完全反转时，恢复电压。离子选择性和电场方向的同时反转导致单向电渗流。我们开发了一个定量准确的理论模型，用于设计孔的几何形状，以实现所需的电渗速度。最后，我们证明，单向电渗也发生的生物孔，其结构提出了一个同轴的空腔周围的孔收缩。在不改变孔腔形状或表面电荷的情况下诱导离子选择性的能力可以为选择性膜的更灵活的设计开辟道路。
英文摘要：
Selectivity towards positive and negative ions in nanopores is often associated with electroosmotic flow, the control of which is pivotal in several micro-nanofluidic technologies. Selectivity is traditionally understood to be a consequence of surface charges that alter the ion distribution in the pore lumen. Here we present a purely geometrical mechanism to induce ionic selectivity and electroosmotic flow in uncharged nanopores and we tested it via molecular dynamics simulations. Our approach exploits the accumulation of charges, driven by an external electric field, in a coaxial cavity that decorates the membrane close to the pore entrance. The selectivity was shown to depend on the applied voltage and results to be completely inverted when reverting the voltage. The simultaneous inversion of ionic selectivity and electric field direction causes a unidirectional electroosmotic flow. We developed a quantitatively accurate theoretical model for designing pore geometry to achieve the desired electroosmotic velocity. Finally, we demonstrate that unidirectional electroosmosis also occurs for a biological pore whose structure presents a coaxial cavity surrounding the pore constriction. The capability to induce ion selectivity without altering the pore lumen shape or the surface charge may open the way to a more flexible design of selective membranes.
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