Marco Andrady and Juliu Adamovski from the University of São Paulo (Brazil) and Anna Bernasso from Heriot-Watt University in Edinburgh (Scotland) conducted an acoustic levitation experiment. They managed to hang a foam ball with a diameter of 50 millimeters in the air. The scientists presented the results of the research in the journal Applied Physics Letters.
Flying fish
For "suspension" used ultrasonic waves, which the human ear is usually unable to hear. Previously, in this way, researchers have already forced to levitate small drops of matter, as well as "non-standard" objects like wires and two-dimensional planes.
Back in 2006, employees of the Department of Applied Physics of China Northwestern Polytechnic University repeatedly conducted levitation experiments.
Project manager Wen Jun Xie started with iridium and liquid mercury beads. Directional ultrasound counteracted gravity, and the balls soared upward. This could find application in pharmaceuticals: after all, it is known that sometimes substances interact with the containers in which they are placed. Why not invent a "flying" ball that won't touch the walls of the vessel?
And then Wen Jun Xie wondered what would happen if a living being was placed in the field of an ultrasonic emitter? In the course of the experiment, various small animals were placed under the emitter, creating air vibrations with a wavelength of about 20 millimeters, using tweezers: ants, spiders, beetles, bees, tadpoles, and small fish. Some animals tried to escape, but they failed, as ultrasound pressed on them. But under the influence of vibrations, they "jumped" up and hung in the air … Most of the subjects withstood the whole 30 minutes of this "torture". In general, they endured the procedure normally, except that the fish did not feel well due to the lack of water. In addition, the researchers managed to remove the fry from the eggs in the zone of the ultrasonic field. Wen Jun Xie stated,that the results of the experiment can contribute to important discoveries in the field of biology.
Promotional video:
Big sizes
Now a group of scientists from Brazil and Scotland has for the first time been able to demonstrate the levitation of an object longer than the sound wavelength (14 millimeters). “The acoustic levitation of small objects at the pressure nodes of a standing wave is fairly well known,” commented one of the authors of the article, Marco Andrade. “However, 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 Marco Andrade. "In our article, we show that a combination of ultrasonic emitters can lift a much larger object into the air."
Attempts to make flat objects of considerable size levitate have already been undertaken in the past by other specialists. But then they only managed to create the effect of vertical pressure, and the researchers were forced to prick objects on the needle so that they would not literally fly away …
Marco Andrade and his team forced the levitating object into a stable position without any additional measures. The engineers built a "tripod" system of ultrasonic transducers to provide both vertical and lateral pressure. Their tilt angle and number can be changed. But the essence is the same: a standing sound wave is created between the ball and the emitters, which raises the object into the air. The lifting force of ultrasound is such that the ball soars at a height of seven millimeters (this distance is approximately half the length of the sound wave).
The scope of the application is space
According to the developers, it is theoretically possible to make objects of a wide variety of shapes and sizes "fly", and in addition, to change their position in the air.
If the technology of acoustic levitation is mastered, then this, according to scientists, will make it possible to work successfully with hot materials and liquids, for example, in conditions of space microgravity. Since in orbit the droplets of matter, due to surface tension, acquire larger sizes than we have on Earth, you must first "practice" on larger "specimens" …