The drop is no longer in trend - the technology has gone further …
Only recently we examined in detail how the "gods" could do this, and now … Engineers from Brazil and Great Britain set a new record for acoustic levitation by hanging an object the size of a golf ball in the air with sound. Previously, only drops of matter "flew" in this way, and even then small, as well as not quite ordinary objects, such as wires and two-dimensional planes. The ball is still far from a megalith, but progress is evident …
This time, ultrasonic waves, which the human ear usually cannot hear, suspended a 50mm foam ball in the air. And this was the first demonstration in which scientists made an object larger than the length of a sound wave (14 millimeters, that is, 3.6 times larger) to levitate.
“Acoustic levitation of small objects at the pressure nodes of a standing wave is fairly well known, but the maximum particle size that can be made to levitate in this way is a quarter of a wavelength - that is, only four millimeters,” explains one of the project's authors. "But we are showing that a combination of ultrasonic emitters allows a much larger object to be lifted into the air."
By the way, the lifting force is such that the sphere hovers at a height of seven millimeters (that is, at a distance equal to about half the sound wavelength).
There are several ways to make an object float in the air using sound. In this case, the engineers built a "tripod" of ultrasonic transducers that levitate a foam sphere. A standing wave is formed between the ball and the emitters, which pushes the sphere into the air. Earlier, in other works, physicists "caught" levitating objects in the pressure nodes of a standing wave, but in this case the approach is different.
As the developers of the new system write themselves, the angle of inclination of the emitters and their number can be changed. In addition, they showed that, in theory, it is possible to make objects of a different shape, as well as larger spheres, float in the air, and also to change the position of "flying" objects. “In future work, we want to create new devices that will allow manipulating large objects in the air,” says the researcher.
Note that previously, other experts have also shown that you can make a flat object larger than a wavelength to levitate. However, then they were able to receive only vertical pressure and had to prick their objects on a needle so that they did not literally fly away. Andrady's group came up with a scheme in which the object takes a stable position by itself without additional tweaks (the "tripod" provides both vertical and lateral pressure).
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Acoustic levitation, according to physicists, will make it possible to work with hot materials and liquids, for example, in the microgravity of space. Since droplets in orbit take on larger sizes due to surface tension forces than on Earth, the new technology can be used to study larger samples. And its potential is very great …
Let's watch a video about this discovery:
