Influence of Uneven Patch Zeta Potential on Electroosmotic Mixing Characteristics in a Heterogeneously Charged Micromixer

The effects of unequal patch zeta potential modulation between walls on flow and mixing characteristics for the electroosmotically driven flow in a plane micromixer are examined utilising numerical analysis. To investigate the flow field, recirculation velocity (UR), dimensionless flow rate (Q), mixing efficiency and dimensionless species concentration field, the ratio of the patch zeta potential of the top to bottom wall \(\left( {\zeta_{{\text{r}}} } \right)\) , diffusive Peclet number (Pe) and the patch zeta potential of the bottom wall \(\left( {\zeta_{{\text{P,bottom}}} } \right)\) are varied within the physically justified range. It's been found that UR strengthens with \({\upzeta }_{{\text{P,bottom}}}\) . Interestingly, the value of UR is insensitive with \(\zeta_{{\text{r}}}\) up to \(\zeta_{{\text{r}}}\)  = 1. and UR enhances with \(\zeta_{{\text{r}}}\) when \(\zeta_{{\text{r}}}\)  > 1. Furthermore, as \(\zeta_{{\text{r}}}\) and \(\zeta_{{\text{P,bottom}}}\) rises, the flow rate decreases. The critical limit of Pe is obtained such that \(\eta\) is 100% and it increases with increasing \(\zeta_{{\text{r}}}\) at higher \(\zeta_{{\text{P,bottom}}} \left( { = 3} \right)\) . Moreover, \(\eta\) drops with Pe and rises with increase in \(\zeta_{{\text{r}}}\) for larger Pe.