P Fischer/Nature

This Sonic Tractor Beam Costs Less Than $10 to Make

Welcome to the future.

23 SEP 2016

Researchers have managed to create a sonic tractor beam that can push and pull objects using nothing but sound waves - and they did it for less than $10.

Similar to the tractor beams that drag spacecrafts on Star Trek – but on a much smaller scale – the new device uses acoustic waves to move matter through air or water in precise patterns, without having to touch them.


This isn't the first time researchers have used sound waves to manipulate matter, but it is the first time it's been done so simply – and for less than the price of a lunch.

Developed by engineers at the Max Planck Institute for Intelligent Systems in Germany, the tractor beam is made from just three parts (although it does require a 3D printer, too). All you need is a 3D-printed plastic disk, a thin brass plate, and the kind of speaker you'd find in a watch alarm.

"We were genuinely surprised that nobody had ever thought of this before," one of the researchers, Kai Melde, told William Herkewitz from Popular Mechanics.

So how does it work? The basic idea behind any tractor beam is a wave that can transfer force to an object across a distance, and in the past, researchers have done this with both light and sound

Last year, a team of researchers created the first one-sided acoustic tractor beam by carefully tuning 64 small speakers so that they could move tiny polystyrene balls around – imagine it like the speakers painting an invisible hologram in the air with sound waves.

Although that worked, it was extremely inefficient and expensive, so the team from Germany decided to simplify things.


Instead of creating the acoustic pattern with multiple speakers, what if they just used a single speaker, and covered it with a patterned, 3D-printed plastic filter?

"It worked even better than we hoped," Melde told Popular Mechanics.

In fact, using their 3D-printed plastic, which was fixed to the speaker with the brass plate, they were able to create even more detailed hologram patterns than a mix of speakers – you'd need an array of 20,000 speakers to create the same amount of resolution.

You can see the device in action below, moving a little boat through water, and levitating water droplets:

For now, there are still many limitations to the device: the speaker only sends the hologram in one direction, and can't be angled, which means it can move objects around according to the desired pattern, but can't suddenly decide to move them to the side once they're in the air. That would require a new 3D-printed plastic disc to be created.

And in its current form, the tractor beam only works in two dimensions, by moving an object around on a flat plane, instead of pulling it in and pushing it away. 

But the hope is that with further development, this kind of technology could one day be used like pair of acoustic tweezers, to manipulate sensitive and hard-to-reach substances in medicine and physics. Just imagine being able to direct your sound waves at a patient's kidney stone to break it apart, or move it someone else.

"There's a great deal of interest in using our invention to easily generate ultrasound fields with complex shapes for localised medical diagnostics and treatments," lead researcher Peer Fischer told Colin Jeffrey from New Atlas. "I am sure that there are a lot of [other] areas that could be considered."

The fact that we now know how to make at least simple versions of these tractor beams so cheaply is a great starting point.

If you have access to a 3D printer, you should definitely try this one at home – you never know, you might even come up with a better design.

The results have been published in Nature.

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