The vibration and rotation of piezoelectric particles in high frequency electric fields observed by a thermoacoustic method

Abstract

We have observed, by a thermoacoustic method, the acoustic resonance vibration of small (diameter ∼ 115 Μm) piezoelectric particles in high frequency (∼15 MHz) electric fields. The frequency dependence of the thermoacoustic signal gives direct information about the size distribution of the particles. In very strong rf electric fields we also observed a rotation of the vibrating particles by large angles — as originally suggested by Melcher and Shiren [3] — orienting the initially random rf dipoles parallel to the rf electric fields. The observed strong forces acting on vibrating piezoelectric particles in rf fields can probably be used as a new method of selectively extracting particles of a given size from a broad distribution of very small particles.