How to 3D Print Your Own Tractor Beam

In Star Wars Episode IV: A New Hope, the crew of the Millennium Falcon pops out of hyperspace only to find themselves right in front of the Death Star. It’s their first encounter with the famed evil weapon, and it doesn’t go over well. The ship is immobilized in a “tractor beam” and is gradually pulled into the Death Star.

In a case of real life mimicking fiction, scientists created a real life tractor beam last year that could push, pull, and levitate objects in thin air using sound waves. Improving on those designs, the same researchers have now created a 3D printable, do-it-yourself version of the handheld tractor beam—allowing the maker community to advance the technology even further. The designs were published today in the journal Applied Physics Letters and a “How to” video is available on YouTube.

The concept of the tractor beam originates in science fiction—often portrayed as an invisible grappling hook of sorts that could capture large spaceships and pull them in. Scientists have labored over the decades using all sorts of materials, including water, to try and create such a device with minimal success. But it wasn’t until 2015 that mechanical engineer Asier Marzo, and colleagues, crafted the first true tractor beam that traps and pulls objects from one direction. And he did it with sound waves. It works on a small scale right now, paralyzing plastic beads, and even insects, drawing them into its center like a mini black hole.

“The most important thing is that it can attract the particle towards the source," said Marzo in a press release. "It's very easy to push particles from the source, but what's hard is to pull them toward the source; to attract the particles.” That’s what makes it a true tractor beam.

This tractor beam, however, was of a complex construction, expensive, and overall not something easily replicated by any at-home maker. Marzo lamented that “It was very complicated and pricey because it required a phase array, which is a complex electronic system.”

So Marzo and colleagues at the University of Bristol reexamined their tractor beam construction and replaced phase array with a much simpler, structural material. Instead of altering the sound waves electronically, they did it mechanically using simple tubes that vary in length and shape. This drastically reduces the cost of making the device. The tubes can be 3D printed, and all the other materials can be purchased from places like open-source electronics supplier, Arduino.

“The components are very simple, like an Arduino and a motor driver, and everything can be bought on Amazon for less than £50 (about $70)” said Marzo.

Marzo’s acoustic tractor beam—including his replicable, 3D printed version—are both small. And because of the difficulty of suspending objects more than half the wavelength of sound, the beam can only trap objects around a few millimeters in size. In the lab, however, Marzo and his colleagues have been able to suspend some larger objects and liquids. A lot of work remains, however. And opening its architecture up to the maker community at large will bring all sorts of new ideas and creations sure to advance the its technology.

Strangely, the tractor beam also has applications to studying the effects of microgravity on biological material. "They discovered salmonella is three times more [virulent] when it's levitated,” said Marzo. “Certain microorganisms react differently to microgravity." Fittingly, a science fiction device turned reality could perhaps be used to help humans adapt to life in space—another element of science fiction turned reality.

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