The experimental setup, with speakers and microphones at either end of a water tank, and vertical scattering objects at the center.
Researchers have successfully manipulated the movement of objects using sound. They directed floating objects around obstacles in an aquatic environment, unveiling new possibilities for noninvasive, targeted drug delivery and other biomedical applications.
Researchers from EPFL’s School of Engineering employed optics-inspired techniques to achieve this object manipulation.
“Optical tweezers work by creating a light ‘hotspot’ to trap particles, like a ball falling into a hole. But if there are other objects in the vicinity, this hole is difficult to create and move around,” said Romain Fleury, head of the Laboratory of Wave Engineering in EPFL’s School of Engineering.
Optical tweezers manipulate microscopic particles
Optical tweezers are used to manipulate microscopic particles. These require extremely controlled, static conditions to work properly.
In the past four years, Fleury and his team members tried to move objects in uncontrolled, dynamic environments using sound waves.
According to the researchers, the team’s method – wave momentum shaping – is entirely indifferent to an object’s environment or even its physical properties. All the information that’s required is the object’s position, and the sound waves do the rest.
Method is rooted in momentum conservation
“In our experiments, instead of trapping objects, we gently pushed them around, as you might guide a puck with a hockey stick,” said Fleury.
“The method is rooted in momentum conservation, which makes it extremely simple and general, and that’s why it’s so promising.”
According to the study published in the Nature, the method does not require information about the object’s physical properties or the spatial structure of the surrounding medium but relies only on a real-time scattering matrix measurement and a positional guide-star.
The experiment
In the experimental setup, the ball floated on the surface of a large water tank, with its position tracked by an overhead camera. Audible sound waves emitted from a speaker array at each end of the tank guided the ball along a predetermined path. Simultaneously, a second array of microphones “listened” to the feedback, known as a scattering matrix, as it bounced off the moving ball.
The experiment successfully demonstrated the ability to optimally move and rotate objects, extending the potential of wave-based object manipulation to complex and dynamic scattering media. “We envision new opportunities for biomedical applications, sensing and manufacturing,” the researchers stated.
Game-changer for biological analysis
According to the researchers, Wave momentum shaping is inspired by the optical technique of wavefront shaping, which is used to focus scattered light. However, this marks the first application of the concept of moving an object.
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Furthermore, the team’s method is not limited to moving spherical objects along a path. They also used it to control rotations and manipulate more intricate floaters, such as an origami lotus.
This method could potentially revolutionize biological analysis or tissue engineering applications where physically manipulating cells would cause damage or contamination.
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Prabhat Ranjan Mishra Prabhat, an alumnus of the Indian Institute of Mass Communication, is a tech and defense journalist. While he enjoys writing on modern weapons and emerging tech, he has also reported on global politics and business. He has been previously associated with well-known media houses, including the International Business Times (Singapore Edition) and ANI.
