Non-negligible transient effect on perm-selective ion transportation*

Perm-selective ion transportation has been extensively utilized in various micro/nanofluidic applications. While a steady state assumption was typically adopted to characterize the device, here we experimentally demonstrated that there is inevitable transient effect on the perm-selective ion transportation, especially low Reynolds number environment. The voltage/current (V-C) measurement in micro/nanofluidic platform often showed that current were bumped up in limiting current regime (i.e. overshoot) unlike theoretical results of steady state assumption. In this work, we measured V-C in dead-end channel connected by side channel. Buffer liquid was continuously injected from the side channel so that a constant electrolyte concentration was kept from the side channel to reservoir. Extending the distance from membrane to the side channel resulted in more severe overshoot effect, meaning there is non-negligible transient effect on the ion transportation through membrane. Conclusively, this transient effect should be considered in designing energy-related micro/nanofluidic application.