Multifrequency Acoustic Levitation

Acoustic levitation permits non-contact particle manipulation. The position and orientation of the levitated particle can be controlled by altering the acoustic field. Existing acoustic levitators have employed a single frequency which limits the types of acoustic traps that can be created. The use of multiple frequencies makes it possible to control the forces acting on a particle independently in all directions. We predict theoretically the forces acting on particles placed in the acoustic fields created with multiple coexisting frequencies. To realize the fields, we constructed a 450-channel phased array acoustic levitator with individual frequency, phase, and amplitude control for each channel.