Characterization of electroosmotic pumps using methanol/water mixtures with various compositions

We experimentally studied porous glass electroosmotic (EO) pumps with methanol/water mixtures of varying compositions. We characterized their performance in terms of maximum flow rate, maximum current, and maximum pressure. They all show a linear dependency on an applied voltage, consistent with an EO pump model. We then normalized these performance parameters with the applied voltage to see their dependency on the methanol concentration. We compared these normalized parameters for the full range of methanol concentrations from pure water (deionized water) to pure methanol. The maximum flow rate per voltage shows a nonlinear dependency, while maximum current per voltage and maximum pressure per voltage change monotonically with the methanol concentration. We attribute this dependency mainly to viscosity, which also changes non-monotonically with the methanol concentration. Viscosity would thus be a key property in EO pumping of methanol/water mixtures.