Controlled production of emulsion drops using an electric field in a flow-focusing microfluidic device

We describe a flexible emulsification method using an electric field to generate droplets in a hydrodynamic-flow-focusing geometry in microchannels. The droplet size is controlled by the ratio of inner and outer flow rates as well as by the electric field. As the voltage increases, the droplet size decreases. A Taylor cone is formed and generates very fine droplets, less than 1 mu m in diameter. Small inner flow rates and high electric fields are required to form a stable Taylor cone in a dc electric field. An ac electric field produces tiny droplets periodically. (C) 2007 American Institute of Physics.