Improved acoustic tweezers can use sound waves to pick up and move objects without physical contact.

Researchers have successfully developed ‘acoustic tweezers’ that enable objects to be moved and stimulated using only sound waves. If the team lifted small polystyrene balls off a reflective surface without physical contact with it, they were unable to achieve the desired stability. By fine-tuning their technology, the team claims to have overcome that hurdle. By using adaptive algorithms and further miniaturization, engineers have succeeded in making the technology more stable. With the improvement, the team hopes to develop practical applications of the technology in space and future technologies.

Sound waves can exert physical force – you may have experienced this effect when standing near a loudspeaker. If the speakers are properly arranged and the correct frequency and amplitude are achieved, it allows the waves to be superimposed and create a field of effect. This field helps to move, push or lift objects in a completely non-contact and non-contaminating manner.

Researchers at Tokyo Metropolitan University used a hemispherical array of ultrasound transducers to set up a sound pressure field and use it to pick up millimeter-sized particles. The transducers were driven individually using a unique algorithm that aided the experiment. However, the acoustic tweezers lacked the stability that the researchers aimed to achieve in their new study.

The team has now developed improvements to the technology. They realized that the transducers could be operated in two modes. These are in-phase and out-of-phase. He noted that separate stages are better at performing specific tasks. In-phase mode is good for picking up and moving objects close to the surface and targeting individual particles that are only a centimeter away. The out-of-phase mode, meanwhile, was found to be efficient in bringing the lifted particles to the center of the hemispherical array.

The team observed that by using adaptive switching, they could use both modes and execute a more stable and controlled lift than before. Now, they hope the technology will pave the way for future technology development and find practical applications in space.

This research has been published in Japanese Journal of Applied Physics,