Analytical expressions for the electroosmotic flow in a charge-regulated circular channel

• Analytical model for electroosmotic flow in a pH-regulated circular channel is derived.
• Types of ions (potential determining and indifferent) and their concentrations considered for the first time
• Constant surface potential/charge models yield quantitatively and qualitatively different behaviors.
• Based on our model, the true charged conditions can be inferred by appropriately designed experiments.

Analytical expressions are derived for the flow velocity and ionic current for the electroosmotic flow (EOF) in a charge-regulated circular channel, focusing on the effect of types of ions and their concentrations. We show that the mean flow velocity for those two cases can be different both quantitatively and qualitatively, implying that the true charged conditions can be inferred by appropriately designed experiments. The types of ionic species and their concentrations are also found to play a significant role. Both the EOF velocity and the current density increase with increasing ionic concentration, in general. However, the reverse trend is also observed at a sufficiently high ionic concentration.

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