Levitation by acoustic wave
When you hear the term sonolevitation you might start thinking of a potential method for the construction of the pyramids and then dismiss it.
After all, who at that time could produce such an intense sonowave.
So it’s impossible. But then again……Su Zhao and Jorg Wallaschek wrote A standing wave acoustic levitation system for large planar objects. In this book they discuss an acoustic levitation system that can levitate planar objects that are much larger than the wavelength of the applied acoustic wave.
They observed that a sound radiator in conjunction with the levitated planar object creates a standing wave field. Although these forces are normally weak, they can become powerful when using high intensity waves due to nonlinear characteristics.
Rayleigh1 first studied nonlinear acoustics in 1902 as an acoustic counterpart of electromagnetic waves.
Reference 1 outlines the Matrix Method to simulate acoustic levitators. Using an ultrasonic transducer and reflector. See Figure 1.
A schematic of the matrix method (Image courtesy of Reference 1)
Scientists at Argonne National Labs used this technique in 2012. Check out this video. The University of Tokyo, Nagoya Institute of Technology has a good overview of Three-Dimensional Mid-Air Acoustic Manipulation from 2013.
Much progress in this technique was made by the team of researchers at the University of Sao Paulo in Brazil1 who have developed a new device for levitation that will suspend a tiny object with far more control than ever before. Prior to this test, sonolevitation efforts needed a very precise setup where the sound source and reflector were at fixed resonant distances. This time researchers built a “non-resonant” device for levitation that did not require a fixed separation distance between the source and reflector. See Figure 2
The levitation of expanded polystyrene particles on the left and the simulated standing wave pattern on the right. (Image courtesy of M. Andrade/University of Sao Paulo).
Now larger devices may be built using this technique such as those that can handle hazardous materials or chemically-sensitive pharmaceuticals or maybe even some new high tech toys.
What other uses could you think of for this technique?
Next: References
References
Matrix Method for Acoustic Levitation Simulation, Andrade, Perez, Buiochi, Adamowski, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency control, Vol. 58, No. 8, August 2011.
Ioannis Piliounis heads up his own company called Atlascom, which works on IoT designs based on ARM Cortex-M4 32bit microcontrollers that bind GPRS, 4G, landline and microwave front-end communications with industrial, residential and telemetry monitoring and control systems.
This article first appeared on EE Times’ Planet Analog website.
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