An investigation of the effects of inlet channel geometry on electrokinetic instabilities

Numerical and experimental investigations are performed to examine the feasibility of inducing electrokinetic instability (EKI) phenomena in two-channel junctions containing two aqueous electrolytes with a 10:1 conductivity ratio via the application of a low-intensity DC electrical field. A deep microchannel with 700 μm in depth and 100 μm in width was designed, fabricated and used in this investigation. The results show that when the species streams are injected such that the conductivity gradient between them is perpendicular to the DC electrical driving field, an EKI effect can only be induced by applying a high electrical field intensity of 0.54 V/cm. However, when the potentials applied to the reservoirs of the microchip are switched such that the conductivity gradient is not perpendicular to the electrical field, flow instability can be achieved by applying a lower electrical field intensity.