Overcoming the Fundamental Limitations of Acoustic Levitation
Gia Jing '28
Sound is an essential and familiar part of human activities, enabling human communication, enjoyment of music, and the reception of warnings. Beyond its uses, sound is a physical phenomenon that travels as waves, vibrations of the medium’s particles, allowing energy to move from one space to another. Because sound can exert forces on matter, scientists are able to use the waves, when well-controlled, to suspend particles in midair without direct contact, a technique known as acoustic levitation. A recent breakthrough by physicists at the Institute of Science and Technology Austria (ISTA) has advanced acoustic levitation, making it possible to control multiple levitated particles simultaneously.
Acoustic levitation functions by using high-intensity sound waves that alternate compressions and expansions of regions’ pressure, as the particles push one another and transfer energy through the waves. When identical sound waves reflect and interfere with one another, specifically in air, they form standing waves. These are stationary wave patterns where specific regions of high and low air pressure remain fixed in space (American Institute of Physics, 2015). Within the standing wave, specific points called nodes mark regions where the pressure fluctuations are minimal and forces are balanced, providing ideal locations for small particles to remain suspended (Wilson, 2023). At these nodes, particles experience steady acoustic radiation pressure, which balances the downward pull of gravity and allows the lightweight particles to float (Boudreaux et al., 2025).
Although the technique of acoustic levitation has been successfully utilized to trap and manipulate a single particle, controlling multiple particles to levitate has remained a challenge for physicists. When several particles are placed within the same sound field, they “snap together like magnets in mid-air” because “the sound scattering off the particles creates attractive forces between them,” an effect known as acoustic collapse (Science Is Like Magic, Just Real, 2025). As a result, conventional acoustic levitation systems cannot maintain a stable position of multiple particles, limiting their usefulness for applications that require precise spatial control, especially for manipulating various components simultaneously.
Researchers at ISTA overcame these limitations by introducing an additional physical force. The team added the same amount of electric charge to each levitated particle, causing them to repel each other due to electrostatic repulsion, which occurs between objects carrying like charges (Shi et al., 2025). This repulsive force balances the acoustic attraction between the particles that are induced by the sound waves, enabling the physicists “to keep the particles separated from one another” when levitated in the same sound field (Shi et al., 2025).
Beyond preventing acoustic collapse, the physicists created a system where the interactions between the levitated particles can be adjusted by combining acoustic and electrostatic forces. By altering the amount of charge, the team could achieve various configurations, including “completely separated, fully collapsed, and ‘hybrids’ ones,” –a state between the separated and collapsed (ISTA, 2025). When electrostatic repulsion is weak, levitated particles collapse into a cluster; in contrast, the particles are fully separated and evenly spaced when the repulsion is strong (Shi et al., 2025). Hybrid structures, then, are intermediate conditions, including both clustered and separated particles in the same levitation field (Shi et al., 2025). The physicists named the interaction, in which the levitated particles attract each other at short distances but repel each other at larger distances, “mermaid” potential (Shi et al., 2025).
Additionally, the team observed complex, dynamic behaviors of levitated particles previously unattainable. To control the particle charge, the physicists placed a conductive reflective plate at the base of the acoustic levitation, enabling the particles to briefly touch the base to gain or lose electricity (Shi et al., 2025). This method allowed physicists to alter the arrangement of particle interactions by changing the “balance between sound scattering and electrostatic repulsion” without adjusting the sound wave structure (Michaels, 2025).
The advancement of levitating and controlling multiple particles in a single acoustic levitation field marked a significant step forward in the field of acoustic manipulation. By overcoming acoustic collapse and moving beyond demonstrations of single particles, acoustic levitation can now serve as a platform to observe and study how multiple objects or matter interact with each other, self-organize, and move without physical contact. As a result, acoustic levitation has become a more versatile tool for practical applications, as contact-free control of small objects could reduce contamination and mechanical constraints, such as friction and physical deformation. Ultimately, overcoming the challenge of acoustic collapse demonstrates how combining different physical forces can lead to new scientific possibilities.
References
American Institute of Physics. (2015, January 5). Acoustic levitation made simple. Phys.Org. https://phys.org/news/2015-01-acoustic-levitation-simple.html
Boudreaux, T., Freyhof, L., Riehl, B. D., Kim, E., Pedrigi, R. M., & Lim, J. Y. (2025). Biological acoustic levitation and its potential application for microgravity study. Bioengineering, 12(5), 458. https://doi.org/10.3390/bioengineering12050458
Eastern Illinois University: Physics—Acoustic levitation research group. (n.d.). Retrieved January 3, 2026, from https://www.eiu.edu/physics/acousticlev.php
How acoustic levitation works. (1970, January 1). HowStuffWorks.
https://science.howstuffworks.com/acoustic-levitation.htm
Institute of Science and Technology Austria. (2025, December 2). Physicists overcome fundamental limitation of acoustic levitation. Phys.org.
https://phys.org/news/2025-12-physicists-fundamental-limitation-acoustic-levitation.html Michaels, A. (2025, December 11). How electrostatic repulsion enables stable multi-particle acoustic levitation. Engineeringness.
https://engineeringness.com/how-electrostatic-repulsion-enables-stable-multi-particle-aco ustic-levitation/
Science is like magic, just real. (n.d.). Institute of Science and Technology Austria (ISTA). Retrieved January 3, 2026, from https://ista.ac.at/en/news/science-is-like-magic-just-real/ Shi, S., Hübl, M. C., Grosjean, G., Goodrich, C. P., & Waitukaitis, S. (2025). Electrostatics overcome acoustic collapse to assemble, adapt, and activate levitated matter. Proceedings of the National Academy of Sciences, 122(50), e2516865122.
https://doi.org/10.1073/pnas.2516865122
Solanke, P., Dhotre, R., & Bharkad, V. (2021). Acoustic levitation. Journal of Science & Technology, 6(Special Issue 1), 230–237.
https://doi.org/10.46243/jst.2021.v6.i04.pp230-237