Acoustic radiation force on a cylindrical composite particle with an elastic thin shell and an internal eccentric liquid column in a plane ultrasonic wave field

A model with three-layer structure is introduced to explore the acoustic radiation force (ARF) on composite particles with an elastic thin shell. Combing acoustic scattering of cylinder and the thin-shell theorem, the ARF expression was derived, and the longitudinal and transverse components of the force and axial torque for an eccentric liquid-filled composite particle was obtained. It was found that many factors, such as medium properties, acoustic parameters, eccentricity, and radius ratio of the inner liquid column, affect the acoustic scattering field of the particle, which in turn changes the forces and torque. The acoustic response varies with the particle structures, so the resonance peaks of the force function and torque shift with the eccentricity and radii ratio of particle. The acoustic response of the particle is enhanced and exhibits higher force values due to the presence of the elastic thin shell and the coupling effect with the eccentricity of the internal liquid column. The decrease of the inner liquid density may suppress the high-order resonance peaks, and internal fluid column has less effects on the change in force on composite particle at ka > 3, while limited differences exist at ka < 3. The axial torque on particles due to geometric asymmetry is closely related to ka and the eccentricity. The distribution of positive and negative force and torque along the axis ka exhibits that composite particle can be manipulated or separated by ultrasound. Our theoretical analysis can provide support for the acoustic manipulation, sorting, and targeting of inhomogeneous particles.