Predicting precise acoustic force to trap particles based on scattering patterns
Predicting precise acoustic force to trap particles based on scattering patterns lead image
Although the effects of sound waves on solid spherical particles have been studied extensively for contactless analysis inside microfluidic devices and test tubes, the association between scattering patterns and the acoustic radiation force (ARF) on spheres in a rigid cylindrical tube has not been analyzed systematically.
Shi et al. showed there is an inherent relationship between ARF and far-field scattering patterns and that the complex scattering pattern is unique for each material target. The study provides a stepping stone to developing a systematic guide for precise ARF particle control in a tube.
They found that when the forward scattering is smaller than the backscattering for any rigid, fluid or elastic material in the Rayleigh scattering regime, the ARF strengthens as the frequency increases. In addition, when the fluid-filled cavity resonates, both the ARF and backscattering pattern show identical resonance characteristics for each sphere.
In their theoretical model, the researchers placed stainless steel, gold and beryllium elastic solid spheres, each with different resonance characteristics, inside a rigid cylindrical tube filled with water.
The results show that the values of the forward scattering increase gradually to the maximum scattering and then plunge to the minimum for stainless steel and gold spheres. But for the beryllium sphere, which has more negative force at resonance, the values of the forward scattering first decrease and then shift rapidly to the maximum value.
“This means the negative force may occur when the scattering of the front hemisphere is still stronger than that of the back hemisphere in elastic material spheres,” author Xiaofeng Zhang said.
The researchers plan to confirm their findings with experiments.
Source: “Exploring the underlying mechanism of acoustic radiation force on a sphere in a fluid-filled rigid tube,” by Jingyao Shi, Shuyuan Li, Guangbin Zhang, and Xiaofeng Zhang, AIP Advances (2021). The article can be accessed at https://doi.org/10.1063/5.0054473 .
