La lévitation acoustique peut aussi se faire à la maison, avec des haut-parleurs suffisamment puissants ! © Forance, Fotolia

Scientists eject objects with sound

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The first “sound clamp” was produced by CNRS researchers in 2016: based on a complex system Sound waves, made up of emitters and reflectors, which trap a particle and lift it up! This device was recreated all over the world and then improved several times. Unlike Sound levitation, which involves placing an object in the air where it was previously placed, this technique causes the object to be picked up from a reflective surface. Although they had already developed such a device last year, this time researchers from the University of Tokyo decided to improve its stability, more precisely once the particle is lifted. Details of their project were published in a study Japanese Journal of Applied Physics.

Development of a device called an “sonic gripper” to handle objects without contact. © TMU, YouTube

Evolution of sonic capture, sonic levitation

their device sound clamp It is based on the use of ultrasonic transducers, i.e. devices that convert the input signal into ultrasound. For the 180 transducers used, the Frequencies The output was at 40 kHz. At this frequency, the human ear can no longer hear the signal. The whole was placed in the form of a hemispherical lattice, with the objective surrounding the target particle. But how can sound waves “trap” a particle? Everything depends Pressure Sound radiation: The Sound waves They cause stress in the environment in which they propagate.

By using or reflecting several sources of the same frequency, or by a single reflection, a so-called standing wave can be produced: a wave consisting of a few points ” Knots “, for which the amplitude remains constant over time, and between these ends of the “stomachs”, the amplitude varies over time instead.

At the level of nodes, the amplitude does not vary. Therefore, a particle can be immobilized at the level of the sonic pressure nodes by adjusting it so that the force exerted by the waves compensates for the gravitational force. Here it is Sound levitation ! For sound clamps, it’s more complicated. Emitters must be tuned to move the particle using continuous variation of the emission frequency. “A particle travels at the ends of a standing wave. Therefore, changing the frequency of the signal from the transducers allows the transmission of a particle., describe the researchers. The nodes are thus moved slightly, and the levitating particle follows these nodes. However, this move is one-sided.

Two methods, “in phase” and “out of phase”, bring the particle to its target

The olig clamp developed by the researchers is based on a hemispherical network Ultrasonic Transducer. The manipulated particles are on the order of a millimeter and move following the acoustic pressure field created by this network. But within that field, the particle oscillated until they renewed their sonic tweezers: A major concern when shooting objects using sonic radiation force is the reflection effect caused by the sight. As the sound field is disturbed by this reflection, the object cannot be kept stationary. Researchers explain. A problem that scientists have solved “An Impedance and a Phase and Amplitude Control for Excitation of a Network of Transducers”.

More specifically, they use a switching Adaptation between anti-phase and in-phase excitations”. As the particle is first captured from the ground by in-phase excitation, not all transducers are used. Then the displacement towards the center is carried out in an out-of-phase mode (opposite phase) at this time of the entire network, and it is always maintained in phase resistance using the complete network. The signal thus generated helps to slowly lift the particle and then move it to maintain the central position. This type of device may applications In various fields, especially the manipulation of components can be done without contact: electronics or chemistry. Such an experiment can be more easily reproducedSpaceNo need to compensate for gravity.

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