Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea.
Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States.
Nano Lett. 2021 Jun 23;21(12):5438-5446. doi: 10.1021/acs.nanolett.0c05049. Epub 2021 Mar 30.
Overlimiting current (OLC) through electrolytes interfaced with perm-selective membranes has been extensively researched for understanding fundamental nano-electrokinetics and developing efficient engineering applications. This work studies how a network of microchannels in a nonuniform array, which mimics a natural pore configuration, can contribute to OLC. Here, micro/nanofluidic devices are fabricated with arrays of parallel microchannels with nonuniform size distributions, which are faced with a perm-selective membrane. All cases maintain the same surface and bulk conduction to allow probing of the sensitivity only by the nonuniformity. Rigorous experimental and theoretical investigation demonstrates that overlimiting conductance has a maximum value depending on the nonuniformity. Furthermore, visualization reveals that the nonuniform arrays induce flow loops across the microchannel network enhancing advective transport. This recirculating flow eliminates local salt accumulations so that it can effectively suppress undesirable salt crystallization. Therefore, these results can significantly advance not only the fundamental understanding of the driving mechanism of the OLC but also the design rule of electrochemical membrane applications.
限域电流（OLC）通过与选择透过性膜相互作用的电解质已被广泛研究，以了解基本的纳电子动力学并开发有效的工程应用。这项工作研究了在模仿自然孔隙结构的非均匀阵列中的微通道网络如何有助于 OLC。在这里，使用具有非均匀尺寸分布的平行微通道的微纳流控器件阵列与选择透过性膜相对。所有情况都保持相同的表面和体传导，仅通过非均匀性来探测灵敏度。严格的实验和理论研究表明，限域电导具有取决于非均匀性的最大值。此外，可视化显示非均匀阵列在微通道网络上诱导流环，增强了对流传输。这种再循环流消除了局部盐积累，从而可以有效地抑制不良的盐结晶。因此，这些结果不仅可以显著推进对 OLC 驱动机制的基本理解，而且可以推进电化学膜应用的设计规则。
