DescriptionElectrokinetics provides one of the most plausible alternatives to mechanical pumping in microfluidics. Among its advantages are small volume, fundamental simplicity, overall low mass, and cost efficiency. Our work describes an experimental investigation of the superfast electrokinetics and represents the first attempts to obtain orders of magnitude higher velocities in microchannels. The significance of superfast electrokinetics is to design efficient micro pumps, space actuators, and sea gliders. The influence of applied electric field on both fluid and particle mobilities was quantified at high Peclet numbers using particle image velocimetry and flow rate measurements, simultaneously. The experiments are conducted at very short PDMS microchannels using polystyrene tracer particles and deionized water as the background flow. Electroosmotic slip velocities as large as 3 m/sec are obtained by applying very high electric fields. Classical linear electrokinetic theories cannot explain the experimental behavior of microfluidic systems in these extreme experimental conditions. The increasing field strength causes a rise in the density of ion fluxes at particle surfaces which leads to the deviation of the electrical double layer from the equilibrium state as a result of a local rearrangement in the electrolyte concentration and a potential drop. A secondary diffuse layer of counterions (space charge) is induced outside the primary electrical double layer because of concentration polarization. The nonlinearity associated with the effect of the electric field on the resulting induced charge is consistent with the obtained experimental data. Features of nonlinear electrophoresis are crucial in control, separation and manipulation of colloidal particles.