ACOUSTIC TRACTOR BEAM BREAKTHROUGH COULD LEAD TO LEVITATING HUMANS
Here’s an idea that is really gaining traction: for the first time, University of Bristol engineers have created an acoustic tractor beam capable of trapping objects larger than the wavelength of the sound being used.
This discovery could lead to technology capable of manoeuvring drug capsules around the body, container-less transportation systems, and even the levitation of humans for medical or other purposes, the engineers say.
Researchers previously thought that acoustic tractor beams were limited to levitating small objects. This is because previous attempts to trap particles larger than the wavelength of the sound being used were unstable, with levitated objects spinning out of control.
The team found a workaround for this problem by using rapidly fluctuating tornadoes of sound – essentially a twisterlike structure made up of a loud sound surrounding a silent core. They were then able to increase the size of the silent core, allowing it to hold larger objects.
Using ultrasonic waves at a pitch of 40kHz, a frequency above human hearing but detectable by dogs, the researchers held a two-centimetre polystyrene sphere stationary in the tractor beam. The sphere was more than two acoustic wavelengths in size, making it the largest object to be trapped in a tractor beam.
The finding gives hope that larger objects, such as humans, could be levitated using the same technique, the researchers say.
“Acoustic tractor beams have huge potential in many applications,” said Prof Bruce Drinkwater, who supervised the research. “I’m particularly excited by the idea of contactless production lines where delicate objects are assembled without touching them.”
A polystyrene ball levitates in ultrasonic soundwaves