The world's most powerful acoustic tractor beam could pave the way for levitating humans

January 22, 2018, University of Bristol
Working principle of virtual vortices: intertwined short vortices of opposite directions are emitted to trap and stabilize the particle. Credit: University of Bristol

Acoustic tractor beams use the power of sound to hold particles in mid-air, and unlike magnetic levitation, they can grab most solids or liquids. For the first time University of Bristol engineers have shown it is possible to stably trap objects larger than the wavelength of sound in an acoustic tractor beam. This discovery opens the door to the manipulation of drug capsules or micro-surgical implements within the body. Container-less transportation of delicate larger samples is now also a possibility and could lead to levitating humans.

Researchers previously thought that acoustic tractor beams were fundamentally limited to levitating small objects as all the previous attempts to trap particles larger than the wavelength had been unstable, with objects spinning uncontrollably. This is because rotating field transfers some of its spinning motion to the objects causing them to orbit faster and faster until they are ejected.

The new approach, published in Physical Review Letters today, uses rapidly fluctuating acoustic vortices, which are similar to tornadoes of sound, made of a twister-like structure with loud sound surrounding a silent core.

The Bristol researchers discovered that the rate of rotation can be finely controlled by rapidly changing the twisting direction of the vortices, this stabilises the tractor beam. They were then able to increase the size of the silent core allowing it to hold larger objects. Working with ultrasonic waves at a pitch of 40kHz, a similar pitch to that which only bats can hear, the researchers held a two-centimetre polystyrene sphere in the tractor beam. This sphere measures over two acoustic wavelengths in size and is the largest yet trapped in a tractor beam. The research suggests that, in the future much larger objects could be levitated in this way.

A styrofoam particle of 1.6cm (1.88 wavelengths of sound) trapped in the centre of a 40kHz ultrasonic generator of virtual vortices. Credit: University of Bristol

Dr Asier Marzo, lead author on the paper from Bristol's Department of Mechanical Engineering, said: "Acoustic researchers had been frustrated by the size limit for years, so its satisfying to find a way to overcome it. I think it opens the door to many new applications."

Dr Mihai Caleap, Senior Research Associate, who developed the simulations, explained: "In the future, with more acoustic power it will be possible to hold even larger objects. This was only thought to be possible using lower pitches making the experiment audible and dangerous for humans."

Bruce Drinkwater, Professor of Ultrasonics from the Department of Mechanical Engineering, who supervised the work, added: "Acoustic tractor beams have huge potential in many applications. I'm particularly excited by the idea of contactless production lines where delicate objects are assembled without touching them."

Styrofoam painted particles of 2mm diameter spinning inside a regular vortex. Credit: University of Bristol

Explore further: Sonic tractor beam invented (w/ Video)

More information: Acoustic virtual vortices with tunable orbital angular momentum for trapping of Mie particles, Physical Review Letters (2018). journals.aps.org/prl/accepted/ … 0495104784e979276734

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16 comments

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antialias_physorg
5 / 5 (3) Jan 22, 2018
This discovery opens the door to the manipulation of drug capsules or micro-surgical implements within the body

I also saw an application where they used this in combination with gesture control as a force feedback mechanism. that would put Augmented reality on another level entirely (as currently teh lack of any kind of force feedback is a real pain in the behind when trying to manipulate menus and controls)
FredJose
1 / 5 (8) Jan 22, 2018
This is a great development.

One is immediately reminded of the biblical verse where Elijah is taken up into heaven by the whirlwind.....seems such an appropriate connection.
mackita
5 / 5 (1) Jan 22, 2018
You would levitate and your kidney stones will be melted in addition...
TheGhostofOtto1923
5 / 5 (7) Jan 22, 2018
One is immediately reminded of the biblical verse where Elijah is taken up into heaven by the whirlwind.....seems such an appropriate connection
-Which is like when Jack climbed the beanstalk to get to giant heaven. Similar appropriateness.
Whydening Gyre
4.2 / 5 (5) Jan 22, 2018
This is a great development.

One is immediately reminded of the biblical verse where Elijah is taken up into heaven by the whirlwind.....seems such an appropriate connection.

You being about the only "One" to be reminded of that...
which seems appropriate...
rrwillsj
3 / 5 (2) Jan 22, 2018
Hey! The next generation of carnival fun-rides. Cause, there are just not enough ways now to have you upside down and inside out like a Klein Bottle. Puking your corndogs and cotton candy all over any spectators stupid enough to stand too close!
TheGhostofOtto1923
5 / 5 (1) Jan 22, 2018
Re jack/beanstalk, I am not thge only one with holy allegory powers...

"A vision and word:
This morning as I waited on the Lord I saw a vision of a seed being planted that overnight turned into a beanstalk that reached to Heaven. It was like a scene out of the fairy tale, "Jack and the Beanstalk".

"As seeds were planted, God's people were ascending to the Throne Room in Heaven and seated next to the Father and the Son.

"I was immediately reminded of the story of the widow and her son in 1 Kings 17 where she takes the last of her provision and obeys God by using it to feed the prophet Elijah."

-But unlike this lady and st fred, I do not imagine that god or elijah or the angels gabriel and moron-i are sending me special messages. I just have a sense of humor which I happen to think is a far more valuable blessing.
mackita
5 / 5 (1) Jan 22, 2018
in the future much larger objects could be levitated in this way
It's highly improbable, because for lifting heavier objects than polystyrene balls (note that density of levitating objects remains the same in all experiments) we should increase energy of ultrasound, thus increase its frequency and decrease its wavelength - which would in turn limit the size of levitating objects.
rrwillsj
1 / 5 (1) Jan 23, 2018
Now Mack, stop being reasonable. You're spoiling the fun for those of us who enjoy making fun of whoever writes these ridiculous headlines.
mackita
not rated yet Jan 23, 2018
OK, let's talk about practical applications...
rrwillsj
1 / 5 (1) Jan 24, 2018
Like I said Mack, carnival fun rides! You know the kinda money the concession organizers make?
Aroryborealis
5 / 5 (1) Jan 24, 2018
Mack' and rrwil', what inquiring minds really need to know is:
I mean...c'mon, let's get real. It's phreakin' sound!
How do they expect this to work in Space?
.
.
.
.
Ya' know, like a docking accoutrement for some FTL starship?

TheGhostofOtto1923
5 / 5 (2) Jan 25, 2018
Mack' and rrwil', what inquiring minds really need to know is:
I mean...c'mon, let's get real. It's phreakin' sound!
How do they expect this to work in Space?
makita/zephyr believes that all of space is full of infinitely dense aether and vibrations in it are the cause of everything.

But DO NOT ask him about it as the ensuing flood will only get him banned for the 50th time. Which he deserves but it's still sad.
rrwillsj
3 / 5 (2) Jan 26, 2018
Yeah Otto, you're right about how tedious m/z gets with that magical A***** crap.

When everyone knows that all the stars in the sky are products of deistic flatulence. Go ahead, compare the chemistry!
savvys84
not rated yet Jan 29, 2018
Superman comes of age
EnricM
not rated yet Jan 29, 2018
This is a great development.

One is immediately reminded of the biblical verse where Elijah is taken up into heaven by the whirlwind.....seems such an appropriate connection.

You being about the only "One" to be reminded of that...
which seems appropriate...


LOL, I was reminded of "I got levitation" of 13 Floor Elevator fame ;)

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