A novel technique for producing metallic microjets and microdrops

A new technique for producing steady metallic jets is proposed. It allows the production of supercritical jets with Weber numbers well below unity, which entails important technological advantages over existing techniques. The metallic liquid is injected through a micrometer converging nozzle located inside a gas stream. Both the liquid jet and the coflowing gas current cross an orifice located in front of the nozzle. The gas stream stabilizes the jet by sweeping away the capillary waves growing on the free surface. In this way, one can steadily produce microjets with a kinetic energy much lower than the interfacial energy, a possibility that has been predicted theoretically (Gañán-Calvo in Phys Rev E 78:026304, 2008). Experiments were conducted with mercury to assess the performance of the new technique. The experimental results agreed remarkably well with the predictions calculated from the convective/absolute instability transition of the jet. The jet breakup mechanism did not correspond to classical Rayleigh instability, but to the growth of surface waves over a capillary column which ends at a fixed location. The results were compared with those obtained with the well-established flow focusing method to show that the new technique considerably favors the jet’s stability.