Liquid Needle.

This paper describes a novel phenomenon "liquid needle" produced by the self-focusing acoustic transducer (SFAT). The SFAT is composed of a metal/piezo-material/metal plate (with and without a support layer) which has one side air backed while the other side is liquid backed. The SEAT generates and focuses acoustic waves (through wave interference) at the top surface of the liquid (with acoustic intensity up to 15W/cm²). The focused acoustic beam deforms the free liquid surface through the acoustic streaming effect, and produces a needle-shaped liquid column on the free liquid surface. With various SFATs and different types of liquids, we have obtained liquid needles that are 400-12 000 µm tall. The liquid needle diameter at its tip varies from less than 15 µm to more than 200 µm. [ABSTRACT FROM AUTHOR]