Acoustic manipulation of multi-body structures and dynamics

Area of Science:

• Acoustofluidics
• Soft Matter Physics
• Nonlinear Dynamics

Background:

• Contactless manipulation of objects using intense ultrasound is a well-established research area.
• Sound-mediated interactions among multiple particles, particularly at close range and sub-wavelength scales, are less explored but offer rich dynamics.
• Understanding these interactions is crucial for advancing applications in microparticle manipulation and assembly.

Purpose of the Study:

• To elucidate the fundamental mechanisms governing sound-mediated interactions among rigid and deformable particles at sub-wavelength scales.
• To highlight the influence of particle shape on interaction dynamics.
• To present recent advancements in characterizing complex interactions, including non-conservative forces, non-pairwise additivity, and emergent instabilities.

Main Methods:

• Theoretical analysis of acoustic forcing on particles.
• Investigation of secondary acoustic scattering, Bjerknes forces, and micro-streaming effects.
• Characterization of particle interactions in the sub-wavelength regime.

Main Results:

• Detailed mechanisms of sound-mediated interactions for rigid and deformable particles at sub-wavelength scales are presented.
• The significant role of particle shape in dictating interaction patterns is demonstrated.
• Non-conservative and non-pairwise additive contributions, along with instabilities and active fluctuations, are characterized at high sound energy densities.

Conclusions:

• Sound-mediated interactions among particles at sub-wavelength scales exhibit complex behaviors driven by acoustic scattering, Bjerknes forces, and micro-streaming.
• Particle shape is a critical factor influencing these interactions.
• Emergent phenomena like instabilities and active fluctuations can act as an effective temperature in these athermal systems, expanding possibilities for acoustic manipulation.