911勛圖

Synopsis

The phenomena of matter suspended within an acoustic standing wave has been known since the 19th century, with work from L. V. King and L. P. Gor���kov in calculating the acoustic radiation force in the small particle regime (������返���). Since then, airborne acoustic levitation has found novel application in containerless material analysis, massive object levitation (~10g), and complex three-dimensional (3D) trajectories via Langevin transducer or phased array ultrasonic emitter configurations. Still, little is known on particle stability when size is comparable to driving wavelength (����~����). Exploring the upper limits of object size has led to recent analysis of the particle-size effect, from generalized Lornz-Mie theory and experimental study. The ultrasonic acoustic force and thus the particle���s behavior, critically depends on size. While small particles are trapped on-axis at pressure nodes, larger spheres find equilibrium off-axis at antinodes. Their results suggest extension to any complex amplitude structure, such as in 3D display technologies and surface-mount circuit board construction.