We demonstrate numerically the mechanisms for enhancing mixing in micro slits of a charged solution possessing shear rate depending on viscosities. Recently, the new findings on electroosmotic phenomena in chip format allow efficient trapping and concentration of biomolecules by utilizing ion concentration polarization near nanofluidic structures. In response to this, an electric field with an induced pressure is introduced for the ion diffusion, drift, and nonlinear coupled electroosmotic flow system to lead to an explicit shape with a variation of modulated surface potential in the axial direction with the variation of slip lengths and modulated patternings. It is noted that the implementation of no-shear zones sequentially creates micro rotations resulting in a significant increment in the potential, influenced by the electroosmotic streaming current. Mixing efficiency is computed based on the comparison of the standard deviation of the point concentration or pixel intensity in the mixing section to that in the non-mixing section where the dispersion coefficient is approximated by the lubrication theory. It is observed that the electroosmotic transport mechanism is governed through conductivity gradients turned unstable when the electroviscous stretching and folding of conductivity interfaces grew faster than the dissipative effect of molecular diffusion. This could induce a higher convective diffusion when a T-type mixture outputs are pushed in the micro slit inlet with two different species concentrations resulting in the mix of fluids efficiently. Additionally, it is found that with a higher input voltage, the number of slips with the corrugated patterning generates in-plane vortices which grew faster with higher slip length resulting in a minimization of pressure drop, which could be helpful for the fabrication of micromixers designed for the mixing analogy used for continuous dilution of cell samples.