APPLICATIONS
Acoustic levitation can be used as a tool in many situations depending on the distance between the levitated object and the vibrating surface as well as the local gravity. A few of these applications are detailed below.
Generally, acoustic levitation is used for the movement and manipulation of small and/or fragile objects as well as liquid droplets.
Fragile objects and organisms may be manipulated using acoustic levitation without causing damage or harm [1].
Liquid droplets can similarly be suspended between two vibrating surfaces, allowing scientists to investigate the properties of the liquid and produce more effective pharmaceuticals [2].
In the cases where the levitated object is sufficiently close to the vibrating plate, the situation transitions to the near-field regime, which is commonly used for microassembly, non-contact transport, non-contact bearings, and acoustic motors.
In the near-field regime, acoustic levitation can be used to contactlessly transport objects horizontally by applying a traveling wave to the levitated object [3].
In addition to levitating an object, an automatic torque can also be produced by applying near-field acoustic levitation in the form of an acoustic motor - causing the levitated object to rotate [4].
Near-field acoustic levitation can also be used to produce squeeze film air bearings, which have the advantages of producing less frictional wear and having a high stability compared to other non-contact bearings [5].
Under certain circumstances, the levitating force switches to an attractive force - allowing small objects to be transported and manipulated against the force of gravity [6].
In microgravity conditions, acoustic levitation becomes easier to produce due to the absence of gravity resulting in a lower acoustic force requirement. The effect of hypergravity on near-field acoustic levitation, however, has not yet been determined and is the topic of our study.
Through parabolic flight tests, it was found that lower gravity levels allow larger droplets to be levitated, transported, and coalesced than is possible with Earth’s gravity - motivating the use of acoustic levitation as a way of manipulating droplets for future space experiments and missions [7].
Flown on space shuttle flight STS 41-B, the ACES module attempted to use acoustic positioning techniques to facilitate the containerless melting and processing of a fluoride glass sample. Later, this same module and sample were used to verify a non-contact surface tension measurement technique. Unfortunately, no useful data was recovered from these experiments because of a number of instrument malfunctions that resulted in reduced sample visibility and feedback system instability [8].
[1] Xie, W.J., Cao, C.D., Lü, Y.J., Hong, Z.Y., and Wei, B. (2006). Acoustic method for levitation of small living animals, Appl. Phys. Lett. 89, 214102
[2] Sagoff, J. (2012, September 12). No magic show: Real-world levitation to inspire better pharmaceuticals. Retrieved April 04, 2021, from https://www.anl.gov/article/no-magic-show-realworld-levitation-to-inspire-better-pharmaceuticals
[1] Xie, W.J., Cao, C.D., Lü, Y.J., Hong, Z.Y., and Wei, B. (2006). Acoustic method for levitation of small living animals, Appl. Phys. Lett. 89, 214102
[3] Ueha, S. (2002). Phenomena, theory and applications of near-field acoustic levitation, Rev. Acústica 33(4)
[4] Shi, M., Feng, K., Hu, J., Zhu, J., & Cui, H. (2019). Near-field acoustic levitation and applications to bearings: A critical review. International Journal of Extreme Manufacturing, 1(3), 032002. doi:10.1088/2631-7990/ab3e54
[5] Davis, S., Gabai, R., & Bucher, I. (2018). Realization of an automatic, contactless, acoustic levitation motor via degenerate mode excitation and autoresonance. Sensors and Actuators A: Physical, 276, 34-42. doi:10.1016/j.sna.2018.03.021
[6] Andrade, M. A., Pérez, N., & Adamowski, J. C. (2017). Review of Progress in Acoustic Levitation. Brazilian Journal of Physics, 48(2), 190-213. doi:10.1007/s13538-017-0552-6
[7] Hasegawa, K., Watanabe, A., & Abe, Y. (2019). Acoustic manipulation of droplets under reduced gravity. Scientific Reports, 9. doi:10.1038/s41598-019-53281-4
[8] Elleman, D., Wang, T., & Barmatz, M. (1988). Acoustic Containerless Experiment System A Non-Contact Surface Tension Measurement (Rep. No. N89-20308). NASA Technical Reports. oai:casi.ntrs.nasa.gov:19890010937
