The theory of sonic levitation has been expanded upon by new research, which also highlights potential uses.
Sound waves can be used, like an invisible pair of tweezers, to lift small objects into the air. Although DIY sonic levitation kits are readily available online, the technology has important applications in both research and industry, including the manipulation of sensitive materials such as biological cells.
researchers in University of Technology Sydney (UTS) and the University of New South Wales (UNSW) It has recently been demonstrated that for precise particle control using ultrasound it is necessary to consider both particle shape and how this affects the acoustic field. Their findings were recently published in the journal Physical review letters.
Loudness occurs when sound waves interact and form a standing wave with nodes that can “trap” a particle. Gorcoff’s basic theory of acoustic levitation, the current mathematical basis for acoustic levitation, postulates that a trapped particle is a sphere.
“Previous theoretical models had only considered symmetric particles. We have extended the theory to account for symmetric particles, and it is more applicable to real-world experience,” said lead author Dr. Shahrukh Sepharranama of the Biodynamics Laboratory at the UTS Center for Sound, Sound and Vibration.
“Using a property called Willis coupling, we show that asymmetry alters the force and torque exerted on an object during levitation, changing the location of the ‘trap.’ This knowledge can be used to precisely control or sort objects smaller than the ultrasound wavelength,” he said.
“In a broader sense, our proposed model based on shape and geometry will bring the two leading fields of non-contact ultrasound manipulation and metamaterials (materials designed to have a property not found in nature) closer together,” he added.
Being able to precisely control small objects without touching them may enable researchers to explore the dynamic properties of sensitive biological materials such as insect limbs, insect or ant wings, and termite legs, said Assistant Professor Sebastien Oberst, Head of the Biodynamics Laboratory. .
“We know that insects have remarkable abilities – termites are very sensitive to vibrations and can communicate through this sense, ants can carry many times their own body weight and withstand great forces, and the microstructure of honeybee wings combines strength and flexibility.
“A better understanding of the specific structural dynamics of these natural objects—how they vibrate or resist forces—could allow new materials to be developed, drawing inspiration from nature, for use in industries such as construction, defense, or sensor development.”
The researchers focused on trying to understand the mechanical properties of termite sensors in order to construct highly sensitive vibration sensors. They recently determined the structural details of the subgenual organ, located in the termite’s leg, that can sense minute vibrations.
“It is currently very difficult to assess the dynamic properties of these biological materials. We don’t even have the tools to capture them. Touching them can disrupt measurements and using a non-contact laser can cause damage,” Professor Oberst said.
“So a far-reaching application of this current theoretical research is to use non-contact analysis to extract new physical principles to develop new acoustic materials.”
References: “Acoustic Radiation Force Caused by Willis Coupling and Torque Reflection” by Shahrukh Sepehrranama, Sebastian Oberst, Yan Keqiang, and David A. Powell, Oct. 17, 2022, Available here. Physical review letters.
“Low-intensity radioactivity μCT scans to reveal the detailed morphology of a termite leg and subgenual organ” by Travers M. Arthropod structure and development.
The study was funded by the Australian Research Council.
Other researchers who contributed to this study include Dr David Powell from UNSW and Dr Yan Ke Xiang from UNSW Canberra.