Dielectrophoretic deflection of ink jets

In continuous ink jet systems, streams of ∼10 pL liquid droplets (diameter ∼30 μm) are ejected from an orifice at rates of up to 350 000 per second with velocities in excess of 20 m s−1. Applications as diverse as printing, MEMS fabrication and microarraying benefit from this technology; however, reliable manipulation of the jet, including basic on/off control and steering of the liquid droplets, remains difficult to achieve. We report a novel scheme to manipulate the trajectories of droplets that rebound at shallow angles from a solid substrate using the dielectrophoretic force exerted by patterned electrodes. Varying the voltage applied to the electrodes provides precise control of the rebounding trajectories, mainly by shifting the location of the droplet impact. This technique can also be used to implement on/off control of the droplet stream. A simple dynamic model successfully predicts the modified trajectories of the droplets.