Modeling large, complex levitated objects allows for applications in acoustic levitation

Acoustic levitation is used in an array of fields as a contactless way to handle and study delicate materials, ranging from bubbles to small insects. Despite rapid improvements in acoustic levitation capabilities, the typical simulation methods are limited to spherical objects and objects smaller than the acoustic wavelength. Sílvio Vieira and Marco Andrade modified the traditional models used to calculate acoustic levitation parameters to better incorporate these modern advances.

“These models work well if we are interested in calculating the acoustic radiation force on small particles, but in order to further extend the applicability of acoustic levitation, the levitator should be able to levitate not only small particles, but also larger non-spherical objects,” said Vieira.

By considering the shape of the levitated object, their approach allows for the calculation of the acoustic radiation force as well as the torque acting on the levitated object – an important factor for large or non-spherical items. In addition, the model also computes the natural frequencies for vertical, horizontal and angular oscillations.

The authors have tested the model using a disk with good experimental agreement, but they expect the model to also work for more arbitrary shapes with complex geometries. This improved understanding of the forces is a step toward future applications of acoustic levitators as contactless robotic grippers that can manipulate and control small objects remotely.

“To accomplish these tasks, it will be of great importance to calculate the acoustic radiation force and torque acting on the levitated object,” Vieira said. “This is the purpose of our model: to calculate the force and torque on objects of arbitrary shapes and sizes.”

Source: “Translational and rotational resonance frequencies of a disk in a single-axis acoustic levitator,” by Sílvio L. Vieira and Marco A. B. Andrade, Journal of Applied Physics (2020). The article can be accessed at https://doi.org/10.1063/5.0007149 .