Acoustic tractor beams use the power of sound to capture particles in the air and, in contrast to the same magnetic levitation technology, capable of capturing most of the liquids and solids. Engineers at the University of Bristol was the first to prove the possibility of stable control of relatively large objects, acoustic tractor beam, which in theory can be used, for example, to move drugs inside the body. Their invention opens the way to a levitation of a person.
Previously it was thought that acoustic tractor beams can capture and move small objects, as all previous attempts to capture particles larger than the wavelength, was unsuccessful and led to their uncontrolled rotation. This happened due to the sound field transmission of the rotational movements of objects, which began to spin faster and faster until eventually discarded, according to the portal EurekAlert.
The invention of scientists from the University of Bristol, described in the journal Physical Review Letters, uses a different approach — the fast oscillations of the acoustic funnels, whirlwinds of sound, created from the loud noises surrounding the silent core.
The researchers have discovered that the speed of rotation can be controlled by rapidly changing the direction of torque movement of the funnels, thereby stabilizing the tractor beam. Through this approach, the scientists were able to increase the size of the silent core, which ultimately allowed to retain larger objects.
Using ultrasound frequency of 40 kHz (only hear bats, to humans they are safe), the scientists were able to levitate a two-centimeter balls of polystyrene. The size of these objects was equal to two acoustic wavelengths that is greater than all items that are able to lift a tractor beam so far. According to researchers, in the future, thus it will be possible to control the movement of much larger objects.
“Acoustic research a long time could not overcome the limit of size of substance used for levitation. We are very pleased to be able to overcome this barrier. I think it opens doors for many areas,” commented lead author, Dr Asher Marzo mechanical engineering faculty of the University of Bristol.
“In the future, with higher acoustic power will be able to hold in the air even larger objects. Now this is considered possible only when using the lower tones, making such experiments audible and dangerous for humans,” added Dr. Mihai Kaleab, created a simulation model for the study.
“Sound tractor beams have great potential in many areas. Personally, I particularly welcome the idea of using contactless production line where very fragile objects can be collected without touching them”, — summed up Professor ultraacoustic Bruce Drinkwater, who led the data science project.