Scientists create acoustic hologram tractor beam

Holograms have been around for a long time and have been used for all sorts of things from video games to bringing Tupac back to the stages of Coachella. A well-executed hologram can look very real with a 3D effect that makes the object being projected look real. Scientists have now added a new wrinkle to holograms with something called an acoustic hologram.

In addition to using light, acoustic holograms also use sound waves with structures created by constructively and deconstructively interfering ultrasonic waves that are able to exert force on objects. This has allows the researchers to create a tractor beam that is able to exert force on objects just as the tractor beam on the USS Enterprise from Star Trek.

When a standing wave of ultrasound is formed between two elements with one ultrasound emitter array aimed at a reflector. That wave allows small particles to be suspended in the nodes of the wave. When the phase of the wave is varied, the particles can be transported along a single axis. The catch is that the object that is being moved has to be completely inside the array.

Researchers created the acoustic hologram using a 20 x 20 ultrasonic phased array of 10mm transducers that generate a 40 KHz ultrasonic sound wave. The holographic lens creates a specific pattern of sound waves that trap small polystyrene particles that were used in testing. Check out the video to see the levitation in action.

SOURCE: Spectrum