Enhanced micromixing of electroosmotic flows using aperiodic time-varying zeta potentials

Abstract

This paper proposes a technique for enhancing the mixing of electroosmotic flows in a microchannel by means of aperiodic spatio-temporal variations in the zeta potential. The effects of the magnitude of the time-varying zeta potential, the length of the heterogeneous surface zeta potential patterns, and the aperiodic switching frequency of the zeta potential on the fluid flow characteristics and mixing performance are analyzed by performing a series of numerical simulations in which the aperiodic oscillating source used to modulate the switching frequency of the zeta potential over time is derived using the Sprott system. The results show that the aperiodic spatio-temporal variations in the zeta potential generate irregularly alternating flow recirculations over time, which in turn produce a stirring of the species. In addition, it is shown that an effective enhancement in the mixing performance can be obtained through the application of a suitable switching frequency. Moreover, the mixing performance can be further improved by increasing the strength of the heterogeneous surface zeta potential or the length of the heterogeneous surface zeta potential patterns, respectively. Overall, it is shown that an average mixing efficiency of over 90% can be obtained when the length of the heterogeneous surface zeta potential patterns is equal to twice the channel width, the magnitude of the heterogeneous surface zeta potential is twice that of the homogeneous surface zeta potential, and the value of the oscillating frequency used to modulate the variation of the zeta potential is assigned within an appropriate range.