Ion concentration polarization (ICP) has drawn unprecedented attention due to its new underlying physics and engineering applications such as biomolecular preconcentrator and electrofluidic desalination. Typically, the current-voltage characteristic of ICP has three distinctive regimes with a positive slope in all regimes, but an unintentional negative slope ("overshoot current") was often observed in the Ohmic/limiting regime. This phenomenon impeded an exact estimation of electrokinetic properties of the ICP platform. Therefore, in this work, we eliminated overshoot current by limiting the length of the diffuse layer using a coercive injection of a fresh electrolyte solution. Both the visualization of ICP layer propagation and the measurement of current-voltage characteristics verifying the time for reaching the steady state within an effective length of a microchannel played a critical role. The most relevant parameter was shown to be the diffusion relaxation time which was directly correlated with the sweep rate of an external voltage. Using this new measurement platform, one can significantly reduce the time and labor for the electrokinetic studies and applications based on them.

中文翻译：

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强制选择性离子迁移中强制性稳态消除伪负电导。

离子浓度极化（ICP）由于其新的基础物理和工程应用（例如生物分子预浓缩器和电流体脱盐）而受到了前所未有的关注。通常，ICP的电流-电压特性具有三种不同的方式，在所有方式中均具有正斜率，但是在欧姆/限制方式中经常会出现无意的负斜率（“过冲电流”）。这种现象妨碍了ICP平台的电动特性的准确估算。因此，在这项工作中，我们通过强制注入新鲜的电解质溶液来限制扩散层的长度，从而消除了过冲电流。ICP层传播的可视化和电流电压特性的测量都验证了在微通道有效长度内达到稳态所需的时间，这两者都起着至关重要的作用。最相关的参数显示为扩散弛豫时间，其与外部电压的扫描速率直接相关。使用这一新的测量平台，可以显着减少基于它们的电动研究和应用的时间和精力。