Generalized potential theory for close-range acoustic interactions in the Rayleigh limit

Area of Science:

• Acoustics
• Particle Physics
• Soft Matter Physics

Background:

• Particles in acoustic fields experience radiation forces, leading to trapping and clustering at specific locations like nodes.
• Understanding these forces is crucial for acoustic manipulation and assembly of microparticles.

Purpose of the Study:

• To formulate a generalized force potential for primary and interaction forces on small particles (Rayleigh limit).
• To investigate inter-particle interaction forces under planar and nonplanar standing waves.
• To explore cluster formation and dynamics in acoustic fields.

Main Methods:

• Far-field evaluation of scattered acoustic fields.
• Formulation of a generalized force potential, including primary and interaction forces.
• Analysis of particle interactions in planar and Bessel standing waves.

Main Results:

• The generalized potential for primary forces matches Gorkov's potential.
• Interaction forces depend on the product of the acoustic field and scattered fields.
• Diverse cluster shapes beyond linear arrangements are possible.
• Mutual interaction forces between dissimilar particles are not always action-reaction pairs.
• Nonplanar Bessel waves allow for more complex particle cluster configurations.

Conclusions:

• The generalized force potential offers physical insight into acoustic manipulation of small particles.
• This framework is applicable to arbitrary acoustic wave fronts, including those in acoustic holography.
• Acoustic interactions can lead to complex, multi-directional clustering beyond simple linear arrangements.