Acoustic Holograms

Scientists from the Max Planck Institute for Intelligent Systems in Stuttgart, Germany have found a way to create "sonic tractor beams" that can manipulate objects using only the power of sound. The twist: their set-up only costs $10.

An acoustic tractor beam is a device that can levitate or manipulate small objects without touching them only using sound. To do that, it would have to create "acoustic holograms."

A regular hologram precisely scatters light to create a pattern; an acoustic one scatters sound. Now, create an acoustic hologram around a small object, and you can move it around.

This isn't the first acoustic tractor beam, a team from Spain was able to create the first one last year. But their set up used many speakers arranged in an array, which costs significantly more than this newer method. The new study was able to recreate the same phenomenon, but using just a single speaker.

Instead of an array of speakers where the combinations of sound waves create the hologram, this one manipulates the sound waves of one speaker. It does that by passing the sound through a 3D-printed plastic disk, which is specifically created for each pattern.

The German device consisted just of a cheap speaker (think a watch's alarm), the printed plastic filter, and a thin brass plate for stability—a total of less than $10.

Better Ultrasounds

If manipulating sound waves sounds familiar, that's because it is the basic concept behind ultrasound-based therapies. As the author's note, "There's already a wide variety of ultrasound-based medical therapies where ultrasound is used to stimulate tissue to regrow, like strained muscles, for example. I think you could use this technology to create really simple, but personalized devices—like patches—that stimulate a precise pattern of muscle based on whatever a doctor has prescribed."So this development could be the key for targeted delivery of ultrasound or other waves. Also, this could be used to manipulate sensitive or delicate engineering parts, or move specimens on petri dishes without contamination.

The applications are as many as they are varied to many fields. No doubt that further study will find more ways to expand on this technology. The cost factor alone could open up so many avenues for application of acoustic holograms.

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