Theoretical and Experimental Studies on AC Electric Field Induced Droplet Deformation in a Microchannel.

We present both theoretical and experimental studies on the deformation of aqueous droplets in an alternating-current (AC) electric field. Droplets are first generated using a microfluidic T-junction and are then deformed downstream using a set of coplanar microelectrodes. We investigated how the electric field strength, AC frequencies, conductivities of the aqueous fluids and interfacial tension affect the deformation of droplets in a microchannel. The experimental results are well explained by the electrohydrodynamic (EHD) theory for almost all system parameters explored in this study. Only at very high electric field strengths do the experimental results deviate slightly from the EHD theory. The observed experimental trends can be explained by a series of scaling analyses that provide insights into the interaction of the different physical properties with the electric field. We expect that the present work will provide a better understanding of electrically mediated deformation of droplets in a microchannel.