Can Scientists Levitate Objects? Yes, Thanks To 'Acoustic Holograms'
No, it's not magic, but it almost seems like it.
A team of physicists in Germany have successfully levitated particles and manipulated objects by taking advantage of the properties of sound.
Although this has been performed before, the new research is impressive, as it generates a complex field of structures known as acoustic holograms. This is also the only time that experts have produced the occurrence using a single sound source.
"It's just like the holograms you've seen in Star Trek," said Peer Fischer, a physicist at Max Planck Institute for Intelligent Systems and one of the co-authors of the study. The difference, however, is that the new study does not generate the image using light.
"We do it with sound," said Fischer.
In 2015, scientists from the University of Bristol exhibited an acoustic system that could float objects.
This system works the same way as that of Fischer and his colleagues, as both systems generate sound waves that approach the object from multiple directions at different frequencies and amplitudes.
It works like this: when the sound waves mingle, they produce a pressure gradient in the air or fluid, which holds the particle aloft or cause the object to move if it is on the surface of water.
But the experiment of the team from Bristol needed speakerlike devices known as transducers to create exactly the right kind of wave.
Fischer said such a requirement would involve a large number of sound sources, which can be costly and complicated.
With that in mind, Fischer and his team were searching for a way to move large numbers of microparticles simultaneously, making it easier to assemble them into bigger and more complex structures.
The Max Planck Institute scientists developed their alternative method: instead of using dozens of transducers, they opted to use just one, but the sound passes through a plate that manipulates it into the exact type of sound field.
This field cannot be seen by the naked eye, but Fischer said that if we take a microphone and move it through the space, we shall hear a "3D picture." These plates are then called acoustic holograms.
Fischer and his colleagues' technique could revolutionize a wide range of fields, particularly acoustic imaging. Scientists can conduct an ultrasound to detect the patient's medical condition.
It can be used in transmitting a sound beam through a specific part of steel and determining if there is a crack. Lastly, the technique could be used in experiments where researchers can move a petri dish without touching it.
Meanwhile, details of the study are published in the journal Nature.
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