Electrohydrodynamic tip streaming and emission of charged drops from liquid cones

When a liquid is subject to a sufficiently strong electric field, it can be induced to emit thin fluid jets from conical tip structures that form at its surface. Such behaviour has both fundamental and practical implications, from raindrops in thunderclouds to pendant drops in electrospray mass spectrometry. But the large difference in length scales between these microscopic/nanoscopic jets and the macroscopic drops and films from which they emerge has made it difficult to model the electrohydrodynamic (EHD) processes that govern such phenomena. Here, we report simulations and experiments that enable a comprehensive picture of the mechanisms of cone formation, jet emission and break-up that occur during EHD tip streaming from a liquid film of finite conductivity. Simulations show that EHD tip streaming does not occur if the liquid is perfectly conducting or perfectly insulating, and enable us to develop a scaling law to predict the size of the drops produced from jet break-up.