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Soundwaves can be used to move objects

Soundwaves have emerged as a powerful alternative in the manipulation of microscopic particles, traditionally reliant on optical tweezers – a technology championed by Nobel Prize winner Arthur Ashkin.

However, these tools require static and controlled conditions to function effectively. Challenged by the limitations of optical tweezers in dynamic environments, researchers have now turned to this innovative approach.

Led by Romain Fleury from the EPFL’s Laboratory of Wave Engineering, this method seeks to redefine precision in uncontrolled settings using the principles of wave momentum shaping.

What are soundwaves?

Soundwaves are vibrations that travel through a medium, such as air, water, or solid materials. These waves are generated when an object vibrates, causing the surrounding molecules to oscillate.

This oscillation creates regions of compression and rarefaction, where particles are pushed closer together or spread apart, respectively. These alternating regions propagate through the medium as a wave.

Soundwaves are characterized by their frequency, wavelength, and amplitude. Frequency, measured in Hertz (Hz), determines the pitch of the sound, with higher frequencies producing higher pitches.

Wavelength is the distance between two consecutive points of compression or rarefaction, while amplitude refers to the wave’s height, which affects the sound’s loudness.

Humans perceive sound when these waves reach the ear, causing the eardrum to vibrate. These vibrations are then converted into electrical signals by the inner ear and interpreted by the brain, allowing us to hear and recognize different sounds.

Soundwaves as a tool: Simple, yet effective

At the core of this new method, dubbed “wave momentum shaping,” is the use of soundwaves.

The research team, led by Romain Fleury from the EPFL’s Laboratory of Wave Engineering, has developed a technique that moves objects irrespective of their surroundings or physical properties.

All that is needed is the position of the object, and the soundwaves handle the rest, pushing the objects gently as one might move a hockey puck with a stick. This analogy becomes literal in their experiments.

Imagine a ping-pong ball floating on water, maneuvered by audible soundwaves emitted from speakers. Positioned within a large tank, an overhead camera captures the ball’s position, while soundwaves guide it along a predestined path. The ball’s interactions with these soundwaves are analyzed in real-time, allowing precise control over its movement.

Expanding the potential

The researchers didn’t stop at moving spherical objects. Their experiments also included controlling the rotation of objects and maneuvering more complex shapes, such as an origami lotus.

The technique is based on momentum conservation, a principle that lends the method its simplicity and versatility.

It’s this straightforward yet flexible approach that positions wave momentum shaping as a promising technology for a variety of applications.

Promising applications in medicine and beyond

The potential of this technology extends far into the biomedical field, where it could revolutionize how treatments are administered.

For instance, it could enhance drug delivery systems by pushing medication directly towards targeted areas like tumor cells.

This method offers a noninvasive alternative that could mitigate the risks of traditional drug delivery methods.

Moreover, the technique’s application in tissue engineering could prevent the contamination or damage often caused by physically manipulating cells.

The researchers also envision its use in 3D printing, where it could arrange microscopic particles precisely before they are solidified into structures.

Looking to the future: Soundwaves and beyond

While currently focused on soundwaves, the researchers believe that the principles of wave momentum shaping could also be applied to light, potentially broadening the scope of their impact.

Supported by the Swiss National Science Foundation’s Spark program, their next objective is to scale down the experiments from the macro- to the micro-scale, using ultrasonic soundwaves to move cells under a microscope.

This innovative technique, developed in collaboration with international researchers from institutions like the University of Bordeaux, Nazarbayev University, and the Vienna University of Technology, marks a significant step forward in the manipulation of objects in uncontrolled environments.

As the team continues to refine and expand the capabilities of wave momentum shaping, its implications for science and medicine are bound to grow, opening new pathways for research and application in fields where delicate precision is paramount.

The study is published in the journal Nature Physics.


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