The study presents a novel microfluidic mixing scheme in which the fluid streams are mixed via the applications of harmonic and chaotic electric potentials to four electrodes mounted on the upper and lower surfaces of the mixing chamber. Numerical simulations are performed to analyze the effects of the resulting harmonic oscillating and chaotic oscillating electrokinetic perturbation forces. The harmonic and chaotic oscillating orbits are derived by using non-linear Duffing-Holmes equation. Simulation results indicate that periodic or aperiodic oscillations between the electrodes are obtained to perturb the fluid streams by using harmonic or chaotic oscillating electric potentials to these electrodes, respectively. The results revel that the fluid mixing are improved in the suggested micromixer.