Sound Waves Levitate Multiple Objects – Future Technology for Contactless Medical Procedures

Surgeons won’t be shrunk and sent into the body like in the 1960s Sci-Fi, Fantastic Voyage, but could program a specialised array of mini-speakers to create an intricate sound field that ‘traps’ and manipulates selected objects in ‘acoustic tweezers’ for manipulation within tissue.

Researcher testing the acoustic traps generated by the Holographic Acoustic Tweezers

 Credit Sergio Larripa, Asier Marzo, Bruce Drinkwater 2018.

Advancements in acoustic tweezers from Professor Bruce Drinkwater in the Department of Mechanical Engineering, University of Bristol, and his colleague Dr Asier Marzo, from Universidad Publica De Navarra in Spain, are driving the technology towards this futuristic-sounding reality. The team’s recent developments published today (17 December) in the Proceedings of the National Academy of Sciences, demonstrate for the first time the acoustic levitation and manipulation of multiple objects simultaneously.

Professor Drinkwater envisions an iteration of this system eventually being used to acoustically stitch up internal injuries or deliver drugs to target organs. He said: “Now we have more versatility – multiple pairs of hands to move things and perform complex procedures, it opens up possibilities that just weren’t there before.”

Sound exerts a small acoustic force and by turning up the volume of ultrasonic waves, too high pitched for humans to hear, scientists create a sound field strong enough to move small objects. Now Professor Drinkwater and Dr Marzo have enabled the efficient generation of sound fields complex enough to trap multiple objects at the target locations.

Dr Marzo explained: “We applied a novel algorithm that controls an array of 256 small loudspeakers – and that is what allows us to create the intricate, tweezer-like, acoustic fields.” https://youtu.be/0Up5kr5Xgcg Acoustic tweezers have similar capabilities to optical tweezers, the 2018 Nobel prize winner, which uses lasers to trap and transport micro-particles. However, acoustic tweezers have the edge over optical systems when it comes to operating within human tissue.

Lasers only travel through transparent media, making them tricky to use for applications within biological tissue. On the other hand, ultrasound is routinely used in pregnancy scans and kidney stone treatment as it can safely and non-invasively penetrate biological tissue.