Trajectory Optimization of Levitated Particles in Mid-air Ultrasonic Standing Wave Levitators

Ultrasonic standing wave levitators have a broad range of potential applications as a non-contact transportation method in pharmaceutical, chemical, or biological procedures. In these devices, the particle is held in mid-air and moved to the target position, either by mechanically translating the levitator or by refocusing the standing wave with a phased-array. However, most acoustic levitators operate in open-loop mode and do not have feedback on the position of the particle. Without a control system, the path that the levitated particle follows differs significantly from the desired path. Tracking in three dimensions millimeter-sized particles in mid-air at the required frame rates is technically challenging and costly. In response, we explore offline optimization of the trajectory as a solution. The aim of this optimization is to increase the accuracy with which the desired path is followed by the levitated particle, benefitting contactless transportation and manipulation applications. This method could also be applied to display technologies in which a travelling particle outlines different shapes to convey information.