Electrical manipulation of electrolytes with conductivity gradients in microsystems

Fluid manipulation is of capital importance for the lab-on-a-chip (LOC) technology. We analyse numerically the electrical manipulation of an electrolyte with a steep gradient in saline concentration by a microelectrode array subjected to ac voltages. The results show that the fluid with higher conductivity tends to replace the liquid with lower conductivity in the vicinity of the microelectrodes. This results in the deflection of the interface between the two regions with different saline concentration. We compute the induced velocity as a function of applied voltage and conductivity difference. Only several volts are required to deflect the interface in microsystems.