Mixing enhancement in crisscross micromixer using aperiodic electrokinetic perturbing flows

A novel method is proposed for enhancing the mixing performance in a crisscross micromixer by means of aperiodic time-varying electrokinetic perturbing flows. In the proposed approach, the aperiodic oscillating source used to modulate the perturbing electric potential is derived using the Sprott system. The effects of the perturbation conditions and micromixer geometry parameters on the fluid flow characteristics and mixing performance are analyzed by means of numerical simulations. The results show that irregularly-alternating flow recirculation structures are induced within the lateral channels of the micromixer, which cause a repeated stretching and folding of the species streams in the main channel and enhance the mixing performance as a result. It is shown that an effective improvement in the mixing performance can be obtained through a suitable specification of the scaling factor in the Sprott system. Furthermore, it is shown that the mixing performance can be further enhanced by assigning suitable values to the micromixer geometry parameters or by reducing the ratio of the main channel flow velocity to the lateral channel flow velocity. Overall, the numerical results show that an average mixing efficiency of more than 90% can be obtained by specifying the scaling factor in the Sprott system as 7.5, the ratio of the main channel velocity to the lateral channel velocity as 0.25, the separation distance between the lateral channels as equal to half the width of the main channel, and the width of the lateral channels as equal to the width of the main channel.