Acoustical particle conveyors via Bessel-beam superposition

Area of Science:

• Acoustic physics
• Optical tweezers
• Biophysics

Background:

• Acoustic tweezers offer non-invasive particle manipulation.
• Precise control of acoustic fields is crucial for advanced applications.
• Superposing acoustic beams can create complex sound fields for trapping.

Purpose of the Study:

• To propose and theoretically establish an on-axis, multi-bottle acoustic beam for particle manipulation.
• To demonstrate stable trapping, pushing, and pulling of micrometer-scale particles using acoustic radiation forces.
• To explore the optimization of acoustic tweezers for enhanced trapping stability and field observation.

Main Methods:

• Superposition of two coaxial acoustic Bessel beams to generate acoustic bottles.
• Derivation of spatial acoustic pressure distribution and source phase based on lateral wavenumber (k_r) and source radius.
• Utilizing strong-gradient acoustic radiation forces within the acoustic bottles for particle trapping.

Main Results:

• Stable trapping of micrometer-scale Rayleigh particles in free space was achieved.
• The ability to trap, push, and pull multiple particles along the propagation axis by tuning acoustic frequency was demonstrated.
• Optimization of the k_r-dependent phase lens, including k_r values and the number of Bessel beams, was discussed for improved performance.

Conclusions:

• The proposed acoustic tweezers system, using a single acoustic source and phase lens, provides precise ultrasound field control.
• This technology enables stable manipulation of micro-particles and holds significant potential for in vivo cell manipulation and targeted medical treatments.