Japanese Engineers use Sound Waves to Levitate Objects

Sound waves, which sometimes help levitate your mood can also be used to manipulate and even levitate objects in real-time in the future. Well, this might sound like magic but Japanese engineers from Tokyo Metropolitan University have demonstrated a new technology able to lift a small polystyrene ball from a reflective surface using sound waves.

However, right now they’re not very reliable in doing so, but this could be a big step towards the practical approach for manipulation of objects using sound only. And this is the first demonstration of “non-contact pick-up of a particle on a rigid stage with reflection using a multi-channel-controlled hemispherical ultrasonic transducer array.”

Usage of this type of manipulation – without touch – is very high in the fields of Biomedical Engineering, Nanotechnology, and the Pharmaceutical industry. We have previously achieved this with the help of optical tweezers, which use lasers to generate optimum radiation pressure to move and levitate objects.

But these acoustic tweezers – discovered in the 1980s – could be a more powerful tool for this manipulation than optical tweezers because of the use of sound waves in the levitation of objects. They could move a wide range of particles and of larger size up to millimeters.

Now to develop an acoustic tweezer system that can pick an object from a rigid surface that reflects sound, Japanese engineers Shota Kondo and Kan Okubo of Tokyo Metropolitan University, decided to make a hemispherical acoustic array of ultrasound transducers, that can levitate a 3mm small polystyrene ball from a reflective surface.

As state in the research paper published in the Japanese Journal of Applied Physics (thanks ScienceAlert),

“We propose a multi-channel hemispherical ultrasonic transducer array for non-contact pick-up on a rigid stage with reflection. The phase and amplitude of each channel are optimized using the sound reproduction method. This creates an acoustic trap at only the desired position, and pick up can thus be realized on the rigid stage. To the best of our knowledge, this is the first study to demonstrate non-contact pickup using this approach.”

In their method of levitation, they split the transducer array into 8 blocks and reversed the polarity of half in each block so that it is more manageable to work than to control the transducer. Usage of inverse filter to produce sound based on acoustic waveform was a very unique technique. This is definitely optimizing the phase and amplitude of each transducer channel to generate an acoustic trap, which can be shifted by altering the behavior of the individual blocks.

The 3D simulation shows the exact setup and structure of this field that was generated using these techniques to lift and levitate a polystyrene ball above the wooden board.


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