We've all been there: Building a scale model of the Death Star in our basement and thinking, "I just wish this had a tractor beam to grab onto my tiny Styrofoam Millennium Falcon." Now, thanks to a team of scientists, you can put the finishing touches on that model with your very own sonic tractor beam. OK, maybe we haven't all been there, but I'm sure someone has been there.
It's pretty easy to move things with sound, since sound waves are essentially just vibrations through some physical medium — air, in our case. The sonic tractor beam doesn't move things, but rather, traps them at the focal point of a wall of sound, the place where all of the sound waves converge. A sound source sends waves through a specially-engineered set of tubes, breaking them up and moving them out of phase with each other to produce the exact environment needed to trap a tiny object, several millimetres across.
These tractor beams have been around for a while, but Asier Marzo, a research assistant at the University of Bristol, had some challenges coming up with a DIY, 3D-printed version — there's only so much detail these printers can achieve. With a bit of work, Marzo and his colleagues were able to overcome the limitations of 3D printing and design a DIY beam that only costs around 100 bucks to build, requiring parts like motors and an Arduino. They released an accompanying YouTube video and an open access paper in the journal Applied Physics Letters.
The team hopes to see these tractor beams used in biological research, according to a press release. But there are limitations — the largest trappable items must measure below half the wavelength of the sound waves. In this case, that means your DIY beam will only be able to levitate things like tiny beads or dead flies, which might not impress anyone since a live fly could have just levitated itself.
Also, sounds (mostly) don't propagate through the vacuum of space, so you won't actually be trapping the Millennium Falcon any time soon.