Electrohydrodynamic droplet generators

Abstract In an electrohydrodynamic (EHD) droplet generator, an electric field acts directly on the surface of an electrically conducting jet after it has been formed and ejected from the nozzle. If the electric field has the proper frequency, it will induce compression and expansion of the jet, which will eventually break up into droplets some distance downstream. In contrast to acoustic droplet generators, the initial disturbance is physically separated from the nozzle, so that the exciter and nozzle can be individually designed to perform their separate tasks efficiently. This paper presents a theory of EHD exciters which predicts the breakup length of the jet in terms of the geometry and physical properties of the printer. Experiments confirm this theory, and show that practical exciters can be designed from first principles with the expectation that the breakup length will be close to that predicted, and insensitive to changes in operating frequency.