Improved Acoustic Tweezers Can Levitate, Move Objects Without Physical Contact Using Sound Waves

Researchers have successfully developed 'acoustic tweezers' that enable objects to be moved and levitated using just sound waves. While the team lifted small polystyrene balls off a reflective surface without having any physical contact with it, they could not achieve the desired stability. Fine-tuning their technology, the team claims they have crossed that hurdle. Using an adaptive algorithm and further miniaturisation, engineers have succeded in making the technology more stable. With the improvement, the team hopes to find practical use of the technology in space and in developing futuristic technology.   

Sound waves can exert physical force — you might have experienced this effect while standing near a loudspeaker. If speakers are arranged the right way and the right frequency and amplitude are achieved, then it allows for superimposing of the waves and creating a field of influence. This field in turn helps move, push, or lift objects in a completely contactless and contamination-free manner.

Researchers from the Tokyo Metropolitan University used a hemispherical array of ultrasound transducers to set up fields of sound pressure and lift millimetre-sized particles using it. The transducers were driven individually using a unique algorithm that helped in the experiment. However, the acoustic tweezers lacked stability which the researcher aimed at achieving in their new study.

The team has now developed enhancements in the technology. They realised that the transducers can be driven in two modes. These are the in-phase and the out-of-phase. They noted that distinct phases are better at doing certain tasks. The in-phase mode is better at lifting and moving the object close to the surface and targeting individual particles that are just a centimetre apart. The out-of-phase mode, meanwhile, was found to be efficient in bringing the lifted particle to the centre of the hemispherical array.

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

The research has been published in the Japanese Journal of Applied Physics.