Dynamics of Microscale Particles in Single-Point Acoustic Traps

Acoustic radiation force trapping is used for particle manipulation in gases and liquids. Simple standing wave fields have traditionally been employed, but developments in ultrasound wave field control have shifted focus towards single-point traps, specifically acoustic vortices. These fields carry orbital angular momentum, inducing rotational motion of the particles around the vortex axis. While such fields can enhance particle manipulation capabilities, the rotational motion can lead to instability in particle positioning or cause particle ejection, posing challenges for high-precision applications. We developed a finite element method model for simulating Rayleigh-regime particle dynamics in acoustic traps, simulating the effect of acoustic radiation force and acoustic streaming. Particle trapping ability in an acoustic vortex is characterized as a function of particle properties and acoustic pressure. The simulation can estimate the suitable particle parameters for stable trapping, enabling trap optimization for specific applications.