UK team hails bendy ultrasonic levitation breakthrough

Researchers at the University of Sussex have become the first in the world to develop technology which can bend sound waves around an obstacle and then levitate an object. 

The so-called SoundBender technology, presented at the 31st ACM User Interface Software and Technology Symposium in Berlin, overcomes two key limitations of previous ultrasound levitation devices, which were unable to bypass obstacles that lay between the transducers and the levitating object.

Dr Gianluca Memoli, lecturer in Novel Interfaces and Interactions at the University of Sussex, said: “This is a significant step forward for ultrasound levitation and overcomes a significant drawback that has been hampering development in this field. We have achieved incredibly dynamic and responsive control, so real-time adjustments are just one step away."

According to the team, the key to its breakthrough was the development of a hybrid system that combines the versatility of phased arrays of transducers (PATs) with the precision of acoustic metamaterials while helping to eliminate the restrictions on sound field resolution and variability each of the previous approaches applied. The metamaterial provides a low modulator pitch to help create sound fields with high spatial resolution while the PAT adds dynamic amplitude and phase control of the field.

As well as being used to levitate objects, the technology can also be used to provide haptic feedback beyond an obstacle, and to manipulate non-solid objects such as a candle’s flame.

The group claims that the development opens up new potential in ultrasound levitation, which has a distinct advantage over other levitation techniques because it requires no specific physical properties, such as magnetic or electric, in the object to be levitated and can therefore be applied to a far wider range of materials including liquids and food.

The concept of self-bending beams was initially used in engineering applications, to obscure buildings from noise or protect areas from earthquakes, but this is the first time it has been adopted for use in acoustic levitation.

Dr Gianluca Memoli, Mohd Adili Norasikin and Dr Diego Martinez Plasencia with SoundBender. Image: University of Sussex

Potential applications include high-tech museum displays, enhanced board games with new levels of interactivity; the potential to direct desired smells from a diffuser to where they are needed; the ability to control motion in non-solid items (such as dry ice or fire) and the potential to synchronise these movements to music.

Commenting on the breakthrough Sriram Subramanian, Professor of Informatics at the University of Sussex said: “The potential now is for a device that can bend around larger objects, potentially even as the obstacle is moving. We are also pursuing how to make the device broadband so it can work for all frequencies of sound. This would allow, for instance, sending the music of a radio behind a corner or creating zones of silence in the middle of a dance floor.”