Researchers use acoustic tractor beams to make complex structures in mid air

Name some science fiction technologies and you’d likely come up with actual holograms that you can also feel, or “Holos” as lazy people call them nowadays, laser weapons, food replicators, tractor beams, and more. Except all of those are already science fact which then means that you need to get with the times and update your sci fi knowledge. In the latter’s case we’re now using tractor beams to assemble things in mid air, usher in a new era of autonomous robot surgery, to make pretty patterns in mid air, and of course, to make flying carpets and capture atoms and drag them into imaginary space ships. It’s great to see leading edge technologies being used to progress humanity …

Precisely sculpted sound waves have been used to levitate things for a while now, but last week researchers used them to levitate and manipulate components and tiny droplets of quick-setting glue to build complex structures piece by piece in mid-air. And if you wonder why the heck they’d bother doing that, well, firstly because they could, and secondly because the approach may have practical engineering and medical applications. Obviously.

See it in action

Asier Marzo at the Public University of Navarre, Spain, and his colleagues have developed a system called LeviPrint, which uses a robot arm that can create very specific sound waves. The arm’s movement and acoustic levitation abilities mean that it can carry components to assemble an object from them without touching any parts.

By sculpting sound waves, the machine is able to levitate, rotate and move droplets of glue or resin and small sticks, and by combining these, it can create complex structures. The glue is set almost immediately using a beam of ultraviolet light. Small droplets of resin can also be added to parts and cured in the same way, allowing the device to function similarly to a 3D printer.

The approach offers advantages over 3D printing, says the team - a wide range of materials can be used and it can handle liquids, powders, and hot or hazardous substances.

The prototype operates with 40 kilohertz sound waves and the largest pieces successfully moved around so far were 8 centimetre long sticks of balsa wood which isn’t bad for nothing but a sound wave … Marzo says there will be engineering applications for the technology, and because sound waves can travel through liquids and the human body, there may also be medical uses.

“It’s obvious that we could try to apply these methods to also manipulate some materials inside the human body,” he says (Er … no thank you, Ed.). “Maybe our first ideas are not so much about fabricating inside the body, but manipulating or translating some elements inside of it; maybe nano robots, microscopic cameras or maybe you could transport some medicine to a desired location.”

Journal reference: SIGGRAPH ’22 Conference Proceedings, DOI: https://doi.org/10.1145/3528233.3530752