Acoustic Tractor Beams: Is Levitation Possible?
By: April Carson
Acoustic tractor beams, unlike magnetic levitation technology which can only grab solids or liquids, are now able to hold particles in mid-air and manipulate them. This means that for the first time ever they will be usable on objects larger than a sound wave's wavelength such as drug capsules or microsurgical tools inside of someone's body without being damaged by it. The discovery also opens up new possibilities like container less transportation because delicate goods could be picked up with an acoustic beam instead of having to come into contact with anything else.
Previously, researchers thought that acoustic tractor beams could only move small objects like dust. They couldn't trap larger things because the sound waves would make them spin too fast and then they would be thrown out of the beam. But now, scientists have found a way to create a stable beam by using new technology.
A team of scientists in Canada has come up with a novel way to contain sound which may eventually lead to an improved method for reducing the noise pollution.
Their new approach, published in Physical Review Letters today, uses rapidly fluctuating acoustic vortices (similar to tornadoes) made from twister-like structures surrounded by loud sounds while having silent cores. They discovered that these vortexes can be used as enclosures and because they are able to adjust their size at will; it should result in better flexibility than previous methods available on the market currently such as ear plugs or headphones.
A group of researchers created what is being called "acoustic tornadoes" - whirlwinds composed of two distinct parts: one side where all other noises around it are blocked out and another that allows acoustic waves to pass through. The acoustic tornado.
What is a tractor beam?
A tractor beam is a force field being used in science fiction to pull objects or people towards the source of the beam, hence the term "tractor" beam. The concept was introduced by E. E. Smith (1908–1965) in his book " Skylark of Space", where he depicted two spaceships, one of them pulling another using an invisible force- field beam.
The acoustic tractor beam is controlled by manipulating nodes - points where the acoustic pressure has a minimum value. By controlling the positions of these nodes, acoustic engineers have been able to create acoustic tweezers that can grab tiny objects such as cells and pull them along an acoustic beam or acoustic hands which can push and move objects towards desired locations.
For acoustic tractor beams, acoustic twisters could be used to levitate small objects and acoustic barriers could be used to redirect sound waves around solid objects. Sound is made up of waves of pressure that travel at different speeds depending on temperature differences in the air or medium (in this case liquid) the waves are passing through. A tornado acoustic twister is a (spinning) acoustic vortex that picks up acoustic energy and transports it along its axis in the direction the acoustic twister's spirals are pointing. This acoustic energy can be harvested from acoustic twisters for use in acoustic tractor beams or acoustic hands.
So is acoustic levitation possible? The answer is yes, it's possible to levitate larger objects since the wavelength increases. Tractors beams have crossed over from science fiction into reality, thanks to a new breakthrough by British researchers. Next up? Levitating larger objects and maybe eventually humans.
Experts at the University of Bristol have found a way to overcome limitations in acoustic levitation previously thought unconquerable. Previous research had always given estimates for how big an object can be made to float, but this latest study may remove those restraints on size.