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 SFAT 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 400-12000 μm tall. The liquid needle diameter at its tip varies from less than 15μm to more than 200 μm.
- Acoustic ejector
- Acoustic streaming
- Fresnel half-wave band (FHWB)
- Self-focusing acoustic-wave transducer (SFAT)
ASJC Scopus subject areas
- Mechanical Engineering
- Electrical and Electronic Engineering