Abstract: Simplicity of design is achieved for an electrohydrodynamic microfluidic mixer by applying an electric field substantially transverse to the flow direction and substantially orthogonal or normal to the interfacial plane between the fluids being mixed in the main channel. The electric field is wide enough to encompass substantially the entire depth of the main channel in the microfluidic mixer. In one exemplary embodiment, the electrohydrodynamic microfluidic mixer comprises a substrate, one main channel disposed on the substrate, first and second inlet channels disposed on the substrate and individually coupled to the main channel, and first and second electrodes disposed on opposite sides of the main channel for applying an electric field across the main channel substantially transverse to the flow direction in the main channel. Field uniformity across the desired cross-section of the main channel is achieved by having the electrode thickness be substantially equal to the main channel depth.