Highly Focused Supersonic Microjets

This paper describes the production of thin, focused microjets with velocities of up to 850 m/s by the rapid vaporization of a small mass of liquid in an open liquid-filled capillary. The vaporization is caused by the absorption of a low-energy laser pulse. A likely explanation of the observed phenomenon is based on the impingement of the shock wave caused by the nearly instantaneous vaporization on the free surface of the liquid. We conduct an experimental study of the dependence of the jet velocity on several parameters and develop a semiempirical relation for its prediction. The coherence of the jets and their high velocity, good reproducibility, and controllability are unique features of the system. A possible application is to development of needle-free drug-injection systems that would be of great importance for health care worldwide.