Control of two-phase flow in a microfluidic system using ac electric fields.

The control and handling of fluids are central to many applications of the lab on chip. We report how alternating current (ac) electric fields can deflect and manipulate coflowing streams of two different electrolytes within a microfluidic channel. The two different electrolytes flow side by side over an array of interdigitated electrodes which occupies the width of the channel. Application of a 20 V (peak to peak) voltage at 1 MHz to the electrodes causes the liquid with higher conductivity to occupy a larger region of the channel. This effect causes a significant displacement of the boundary between the two fluids