Low-voltage electrohydrodynamic micropumping of emulsions

A novel low-voltage technique employing electrohydrodynamic (EHD) flow for micropumping oil-in-water emulsions through microchannels is presented. The concept of EHD flow reported at microscopic scale during colloidal aggregation is extended to larger scales, for actuation of bulk motion of emulsion. The experiments involve immersing two vertical parallel electrodes in an oil-in-water emulsion and applying AC fields (15–40 Vp-p; 5–500 Hz) across the electrodes. Liquid flow along the electrode gap is analyzed by microscopically tracking the motion of the suspended oil drops on the free surface. Experimental results confirm an EHD mechanism of flow through field distortions caused by the dispersed oil drops leading to tangential electric field on the charge polarization layer. Comparison of the scheme with conventional EOF scheme shows a drastic reduction in the actuation voltage required for attaining identical velocities. Additional advantage of EHD over EOF includes the independence of the actuation voltage on the microchannel length.