Acoustic trapping of microbubbles in complex environments and controlled payload release

Diego Baresch*, Valeria Garbin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)
32 Downloads (Pure)


Contactless manipulation of microparticles using acoustic waves holds promise for applications ranging from cell sorting to threedimensional (3D) printing and tissue engineering. However, the unique potential of acoustic trapping to be applied in biomedical settings remains largely untapped. In particular, the main advantage of acoustic trapping over optical trapping, namely the ability of sound to propagate through thick and opaque media, has not yet been exploited in full. Here we demonstrate experimentally the use of the recently developed technique of single-beam acoustical tweezers to trap microbubbles, an important class of biomedically relevant microparticles. We show that the region of vanishing pressure of a propagating vortex beam can confine a microbubble by forcing low-amplitude, nonspherical, shape oscillations, enabling its full 3D positioning. Our interpretation is validated by the absolute calibration of the acoustic trapping force and the direct spatial mapping of isolated bubble echos, for which both find excellent agreement with our theoretical model. Furthermore, we prove the stability of the trap through centimeter-thick layers of bio-mimicking, elastic materials. Finally, we demonstrate the simultaneous trapping of nanoparticle-loaded microbubbles and activation with an independent acoustic field to trigger the release of the nanoparticles. Overall, using exclusively acoustic powering to position and actuate microbubbles paves the way toward controlled delivery of drug payloads in confined, hard-to-reach locations, with potential in vivo applications.

Original languageEnglish
Pages (from-to)15490-15496
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number27
Publication statusPublished - 2020


  • Acoustic force
  • Acoustical tweezers
  • Microbubbles
  • Micromanipulation


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