# Acoustic levitation shape question (Japanese scientists link)

• ethereal_int
In summary, scientists have developed a way to levitate and manipulate objects in mid-air using ultrasonic phased arrays. The levitated particles form an X shape due to the pressure nodes in the acoustic field created by four speakers. By changing the phases of the driving signals, the particles can rotate. It is possible to create more complex shapes and control multiple objects by adding more speakers or using a speaker ring. However, suspending heavier objects would require a significant amount of acoustical power. The experiment is described in detail in the paper "Three-dimensional Mid-air Acoustic Manipulation by Ultrasonic Phased Arrays."
ethereal_int
http://sploid.gizmodo.com/amazing-scientists-make-things-fly-around-in-space-usi-1492880964

I wanted to ask is there a specific reason for the completely horizontal X shape of the levitated particles. If we already have such precise control over the standing waves, couldn't it be possible to make more unique shapes?

Like a 3d one with depth (a bigger thickness, or more levels), or a square pattern with 4 walls and an empty center? Or does it have to be a variation of a 2d star because of the orientation of the speakers? Would 2 more speakers give the X 2 more lines? What about a speaker ring or a sphere?
Ultimately that would allow us to control more objects at once independently, and use it in automated construction better.

Last edited by a moderator:
The patterns visible in the video are caused by the pressure nodes in the acoustic field. It appears there are four speakers that contribute to the total sound field. Then when their driving signals' phases are changed it causes the 4-sided group to rotate. Yes, if you mounted more speakers around the circumference the sound field would be generated with more complex (and potentially more controllable) nodes. I've never heard of a "speaker ring", but many speakers evenly spaced around the center would begin to approximate that. My guess is that yes, that would allow more complex motions of suspended particles. Those little white beads are Styrofoam, the LED, and tiny resistor are all very light weight. Suspending heavier objects would require HUGE amounts of acoustical power. Why not experiment yourself and then come back here to Physics Forums and show us your results?

Here is a paper describing the experiment:

"Three-dimensional Mid-air Acoustic Manipulation by Ultrasonic Phased Arrays"
Authors: Yoichi Ochiai, Takayuki Hoshi, Jun Rekimoto
http://arxiv.org/abs/1312.4006

## 1. What is acoustic levitation and how does it work?

Acoustic levitation is a technique that uses sound waves to suspend an object in mid-air. This is achieved by creating a standing wave pattern with two or more sound waves that cancel each other out at certain points, creating stable areas of high pressure where the object can be suspended.

## 2. What shapes can be levitated using acoustic levitation?

Acoustic levitation can be used to levitate a wide range of shapes and materials, including liquids, solids, and even living organisms. However, the shape of the object must be able to fit within the standing wave pattern created by the sound waves.

## 3. How do Japanese scientists link acoustic levitation to shaping objects?

Japanese scientists have discovered that by controlling the frequency and amplitude of the sound waves used in acoustic levitation, they can shape and manipulate the levitating object. They can also change the shape of the standing wave pattern to create more complex shapes.

## 4. What are the practical applications of acoustic levitation shape manipulation?

Acoustic levitation shape manipulation has a wide range of potential applications, including in the fields of material science, pharmaceuticals, and electronics. It can be used to precisely shape and position tiny objects, such as microchips, without the need for physical contact.

## 5. Are there any limitations to acoustic levitation shape manipulation?

While acoustic levitation has many potential applications, there are still some limitations to its use. For example, the size and weight of the object that can be levitated are limited by the strength of the sound waves. Additionally, the shape of the object must be able to fit within the standing wave pattern, which can limit the complexity of shapes that can be manipulated.

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