Do you know what acoustic levitation is? No, it’s not a term from Star Trek or some other Sci-Fi piece, but actually, a real thing that besides it looks really cool could be of great scientific importance.
Scientists were able to levitate small objects such as water droplets by using the power of sound for years, but recently they’ve managed to levitate a 50-mm (2-inch) solid polystyrene ball.
Acoustic levitation is based on high-frequency sound waves; using opposing beams of sound waves standing waves are being created which have peaks that oscillate between high and low pressure. That can be used to bounce and jostle an object up against the force of gravity. It was thought that the maximum sized object that could be levitated using ultrasound waves, which have a frequency about 20 kHz and a wavelength of 14 mm, was around 4 mm in diameter. Marco Andrade from the University of São Paulo in Brazil, one of the researchers, explained the breakthrough for Phys.org. :
“In our paper, we demonstrate that we can combine multiple ultrasonic transducers to levitate an object significantly larger than the acoustic wavelength. We could increase the maximum object size from one-quarter of the wavelength to 50 mm, which is approximately 3.6 times the acoustic wavelength.”
The team used a tripod structure of ultrasound transducers, they generated a standing wave between the transducers and the object. That means the object is being buffered on three sides by sounds waves to hold it in place.
“At the moment, we can only levitate the object at a fixed position in space. In future work, we would like to develop new devices capable of levitating and manipulating large objects in air.”
We can only imagine application possibilities of this finding and until then we can Wow! over levitating ping pong ball in the cool video below.
… and even more levitating.