Deflection of continuous droplet streams using high-voltage dielectrophoresis

We report a novel scheme for steering a high-velocity continuous droplet stream using the dielectrophoretic force. The droplet stream is created using the continuous ink jet method. A liquid jet is ejected from a nozzle at high pressure and is controllably broken up into uniform droplets 30–90 μm in diameter with velocities up to 20 m/s. Voltages up to 2 kV are used to energize a high-voltage probe located downstream from the nozzle to induce the formation of a nonuniform electric field in the vicinity of the probe tip. The stream is passed through the electric field, subjecting the droplets to the dielectrophoretic force in the direction of the electric field maxima. Our scheme provides precise displacement of the droplet stream and requires less hardware than traditional steering methods. Less hardware means the distance between the printing nozzle and receiving substrate is minimized, enabling more accurate droplet positioning and higher print resolution. Other applications of high-voltage dielectrophoresis for droplet steering includes on/off control and manipulation (or removal) of satellite droplets. A simple linear relationship predicts the deflection of the droplet stream in the vicinity of a high-voltage probe as a function of the governing parameters. This relationship holds true for a large range of droplet sizes, stream velocities, geometries, and electric field strengths.