Rapid mode-switching for acoustic manipulation

Acoustic manipulation techniques are becoming increasingly common with a range of applications in the biomedical research, microassembly, and lab-on-a-chip. Recently, a class of devices have attracted considerable attention which utilize dynamic and reconfigurable acoustic fields, known as dynamic-field acoustic devices. A common method of applying dynamic fields is to use mode-switching by rapidly altering the excitation frequency. Such methods generally rely on the switching being performed faster than the time constant associated with the particle motion. Nevertheless, it remains a grand challenge to eliminate or at least reduce the switching time to a minimal value. In this paper, we suggest employing a high-speed controller to minimize the switching time, enabling continuous particle manipulation in a dynamic-field acoustic device. As a proof-of-concept, we apply such idea to a classic acoustic manipulation device, a Chladni plate which consists of a centrally-actuated vibrating plate. By employing a closed-loop real-time controller, we show successful manipulation of particles on the plate on predefined trajectories. The high-speed switching methodology can also be applied to other dynamic-field acoustic methods, such as surface acoustic wave (SAW) devices, acoustic levitators, and in-fluid acoustic devices. This can result in faster and smoother particle manipulation in such devices.