Wang Zhixuan, Hsu Wei-Lun, Tsuchiya Shuntaro, Paul Soumyadeep, Alizadeh Amer, Daiguji Hirofumi
Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
Micromachines (Basel). 2020 Nov 26;11(12):1041. doi: 10.3390/mi11121041.
Transport-induced-charge (TIC) phenomena, in which the concentration imbalance between cations and anions occurs when more than two chemical potential gradients coexist within an ultrathin dimension, entail numerous nanofluidic systems. Evidence has indicated that the presence of TIC produces a nonlinear response of electroosmotic flow to the applied voltage, resulting in complex fluid behavior. In this study, we theoretically investigate thermal effects due to Joule heating on TIC phenomena in an ultrathin nanopore by computational fluid dynamics simulation. Our modeling results show that the rise of local temperature inside the nanopore significantly enhances TIC effects and thus has a significant influence on electroosmotic behavior. A local maximum of the solution conductivity occurs near the entrance of the nanopore at the high salt concentration end, resulting in a reversal of TIC across the nanopore. The Joule heating effects increase the reversal of TIC with the synergy of the negatively charged nanopore, and they also enhance the electroosmotic flow regardless of whether the nanopore is charged. These theoretical observations will improve our knowledge of nonclassical electrokinetic phenomena for flow control in nanopore systems.
当在超薄尺度内同时存在两个以上的化学势梯度时，阳离子和阴离子之间会出现浓度失衡的输运诱导电荷（TIC）现象，这种现象存在于众多纳米流体系统中。有证据表明，TIC的存在会使电渗流对施加电压产生非线性响应，从而导致复杂的流体行为。在本研究中，我们通过计算流体动力学模拟从理论上研究了焦耳热对超薄纳米孔中TIC现象的热效应。我们的模拟结果表明，纳米孔内局部温度的升高显著增强了TIC效应，进而对电渗行为产生重大影响。在高盐浓度端，纳米孔入口附近溶液电导率出现局部最大值，导致纳米孔内TIC发生反转。焦耳热效应与带负电的纳米孔协同作用增加了TIC的反转，并且无论纳米孔是否带电，它们都会增强电渗流。这些理论观察结果将增进我们对纳米孔系统中用于流动控制的非经典电动现象的认识。
