This breakthrough in non-magnetic levitation of large objects opens a new chapter in the future transportation system.

A team of physicists from Brazil and the United Kingdom has made a groundbreaking advancement in acoustic levitation, successfully lifting a 50-mm (2-inch) solid polystyrene sphere using sound waves.

This achievement, detailed in a recent publication in Applied Physics Letters, challenges previous size limitations in the field and opens new possibilities for frictionless transportation technologies.

Historically, the transportation industry, particularly in sectors such as tire manufacturing and high-speed transit, has focused on reducing friction between moving objects and surfaces. Concepts like the Hyperloop rely on eliminating friction to achieve higher speeds and efficiency. Many involved magnets to keep objects – such as Maglev trains – suspended in the air.

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Other types include optical levitation, which uses the radiation pressure from a laser beam to hold tiny particles in place (optical tweezers used in biological research), and optical levitation, which uses electric fields to counteract gravity by applying charges to an object (NASA's research on levitating lunar dust particles).

Acoustic levitation, which uses sound waves to suspend objects in midair, could contribute to future developments in frictionless travel.

Until now, acoustic levitation was restricted by an object's size, which typically could not exceed a quarter of the wavelength of the sound wave used. With ultrasonic waves above 20 kHz, this meant objects larger than 4 mm were difficult to levitate. Furthermore, past experiments primarily succeeded with wire-like or planar objects rather than spherical ones.

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The Brazilian-U.K. research team overcame these barriers by employing multiple ultrasonic transducers in a tripod arrangement. By carefully positioning three transducers, they generated a standing wave between the devices and the levitated sphere, rather than relying on traditional pressure nodes.

This method allowed them to successfully lift and stabilize the larger sphere without direct contact or additional support, marking a significant departure from previous techniques, which often required a central pin to hold objects in place.

This discovery contributes to further research into frictionless transport and material handling technologies. As scientists refine these methods, industries ranging from manufacturing to space exploration could benefit from this novel approach to manipulating objects using sound waves.

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