  Acoustic tweezers are gaining increasing attention due to their excellent
biological compatibility. Recently, the concept of topology has been expanded
from condensed matter physics into acoustics, giving rise to a robust wave
manipulation against defects and sharp turns. So far, topological acoustics
have not been experimentally realized in on-chip level which can be worked as
tweezers for microparticle manipulations. Here, we achieved a topological
on-chip acoustic tweezer based on the topologically protected phononic mode.
This tweezer consisted of one-dimensional arrays of Helmholtz resonant air
cavities. Strong microfluidic oscillations induced by acoustic waves were
experimentally observed at water-air surfaces of Helmholtz resonant air
cavities at the topological interface. Acoustic radiation force induced by
these microfluidic oscillations captured microparticles whose sizes were up to
20 um and made them do orbital rotations. Our topological on-chip acoustic
tweezer realized non-contact label-free microparticle manipulations in
microfluidics and exhibited enormous application potential in the biomedical
field.
