Analytical expressions for pH-regulated electroosmotic flow in microchannels.

We derived analytical expressions for the pH-regulated electroosmotic flow in a microchannel for arbitrary level of surface potential and type of electrolyte solution; previous results are almost always based on the conditions of low, constant surface potential, which are inaccurate and unrealistic. In addition, an analytical expression for the dependence of the surface potential on the electrolyte concentration and solution pH is obtained, which is capable of explaining the behavior of the empirical relation used in the literature. The analytical results derived are readily applicable to further electrokinetic analyses, and to interpret experimental observations and/or design devices involving electroosmosis such as biosensors and lab-on-a-chip.