Minimum trap separation for acoustical levitation using phased ultrasonic transducer arrays

Paper in proceeding, 2019

Acoustic levitation for interactive visualizations is an emerging field which uses ultrasonic transducer arrays to induce radiation forces on small beads. To fully utilize the interactive and responsive aspect of the system, each bead must be controllable freely in the interaction space without interfering with the other beads. When beads are placed far enough apart it is possible to design a sound field that traps all the beads at their desired positions, taking any potential limitations of the hardware into account. The underlying physics limit how close in space two traps can be without interfering with each other. In this paper, we investigate the minimum spacing required between two beads for them to successfully and independently levitate in acoustical traps. Multiple methods for the sound field design are considered and compared with regards to the overall separation required as well as the gracefulness in the breakdown region.