Reversible switching of high-speed air-liquid two-phase flows using electrowetting-assisted flow-pattern change.

This work is the first demonstration of electrical modulation of surface energy to reversibly switch dynamic high-speed gas-liquid two-phase microfluidic flow patterns. Manipulation of dynamic two-phase systems with continuous high-speed flows is complex and interesting due to the multiple types of forces that need to be considered. Here, distinct stable flow patterns are formed through a multipronged approach: both surface tension forces generated by surface chemistry modulation as well as viscous and inertial forces produced by fluid flows are employed. The novel fluidic actuation mechanism provides insights into better understanding microscale two-phase flow dynamics and offers new opportunities for the development of two-phase biochemical microsystems that are mechanically simple and operational at high speeds.